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Join Date: Aug 2006
Location: Cincinnati, Ohio
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Twin Turbo 928 Myths vs. Facts
There seems to be a lot of bad information floating about regarding my 928S4 twin turbo system. Consider this post an effort to eliminate this bad information by using facts to debunk these myths:
Myth 1: The twin turbo system will cost 2X what a supercharger system will cost. Fact: No it won't! Myth 2: Turbochargers don't make the midrange power of a supercharger. Fact: This depends on the supercharger used and your definition of "mid-range". Additionally, statements like this have to be based on equal paramaters, such as; same engine, same compression ratio, same fuel, etc. Pound per pound of boost a twin screw supercharger will nearly always outpower a turbo to about 2,500 or so rpm, where the turbo will then come on full song and make more power on the same boost. This is because the twin screw pump makes nearly immediate full boost pressure whereas the turbocharger requires more RPM to get on full song. Make no mistake, a centrifugal supercharger with its centrifugal compressor usually will make less HP across the entire RPM band than the turbocharger and likely less HP than the twin screw pump below about 4,500 RPM. A centrifugal supercharger will never make the off idle power numbers of a twin screw pump because it is down on boost there. Furthermore, one must consider that the centrifugal supercharger is the slowest of the three (by a long shot!) to reach full manifold pressure, because it only does so at maximum engine speed. The turbo can make all its boost by mid range RPM when it is loaded up and so can every twin screw pump. Engine torque follows cylinder pressures and cylinder pressures are a function of boost pressure (assuming all other variables equal). Engine torque applied across engine speed produced HP. All one has to do it look at the test data available. The twin turbo system was designed to provide power in the range where a performance car like the 928 is driven, namely 3,000 to 6,000 RPM and do this without taxation on the longevity or drivability of the vehicle for daily use. Looking at the data available run at the same paramaters on the same engines shows the significant HP and torque advantage the turbocharged car has in the real world. One other point to add, with a twin screw pump and a turbocharger the boost is modulated based on RPM. If you ever over-rev a turbo or screw pump car you are not likely to "overboost" the engine. Over rev a centrifugal car and you will build higher boost than the the setting at which system was designed to work. Myth 3: The twin turbo system won't make any more power than a supercharger system Fact: First off comparisons based on this statement must have several variables which are fixed, those being the same engine, same fuel, same boost pressures, same compression ratio, etc. When one says "it makes the same power as the turbo car", ask them at what boost pressure that power was made and furthermore take a look at the powerband width which is made at that same boost pressure setting. In simple terms "area under the curve per pound of boost", then pick the pump that works for the area of the curve you want to be driving around in. I can see where one might prefer a twin screw pump over a turbocharger, but I can't see on what performance basis one would pick a centrifugal over either. Consider the twin turbo system has produced in excess of 530 ft-lbs on the road and roughly 550RWHP on less than 12 psig. Too much torque for you, okay we'll crank the pressure back to 9 psig and still make the same torque than you'll see off of what the centrifugally boosted car is making on 11 or 12 psig, maybe even more. Better yet, install a cockpit adjustable wastegate control and go to town. One should consider what pressures are required with other forms of boosting systems to make these numbers, again on the same engine. Remember, you never drive your car hammered up onto the rev limiter all day long. You have to shift at that point. Even a full blown track car benefits from a wide powerband in the upstairs region. It's real simple, if off-idle instant boost is your game, pick a twin screw pump. If a peak high end HP number is your game, pick a centrifugal. If you want excellent road manners down low with massive mid range and top end power, pick the turbo. For further details, see debunk to "Myth 2" Myth 4: The twin turbo system places far more heat into the engine bay than a supercharger system Fact: Is this statement based on running at the same HP level or the same boost pressure level? Since the turbo engine doesn't have to burn as much fuel as supercharged engine to make the same power, there is less overall heat produced per pony. About 1/3 of the heat energy created by burning the fuel goes out the tailpipe...it is this heat energy we harness to power the turbocharger. The rest is letoff as heat (out the pipes or into the cooling system). Since superchargers require more fuel to be burned per HP this means there is more heat going out the tailpies and into the cooling system as compared to the turbocharged car (at the same power level). The twin turbo system has been tested in high ambient heat conditions (100 F) and has exhibited no issues with overheating or melt-down as some would like to believe or fabricate stories about. Additionally, please consider the twin turbo system and most twin screw systems available retain the 928's wondeful dual high-speed radiator fan system and shrouding as designed at the factory. A centrifugal supercharger system typically requres that you remove the large fan packs to fit the supercharger and furthermore some have intake boxes that block off a large area behind the radiator. More fuel burned per HP with a cooling system which has lost its high-power fan system and has a partially blocked radiator is not conducive to a cooler engine bay. Who's running hot again? Myth 5: A turbocharged 928 will burn up exhaust valves while one with a supercharger system will not. Fact: Is one supposed to assume a supercharger places no additional heat on the exhaust valves as compared to its normally aspirated sibling? I'm still perplexed on this statement. Granted there may be slightly more heat on a turbocharged system exhaust valve compared to a supercharged system exhaust valve, but that difference is nowhere near the difference either system places on the exhaust valves as compared to what the normally aspirated system originally had. Also, please remember that you'll have to burn more fuel with the supercharged car to make the same power as the turbocharged car did and about 1/3 of that heat is going out as raw exhaust energy. Both types of systems place additional heat on the exhaust valves...how can they not, you are burning more fuel. Myth 6: The twin turbo system forces you to cut "lots of holes" in the engine bay. Fact: Two 2.5" holes are required to get the intercooler discharge pipes back into the engine bay. I'm sorry, I was not aware people cherished that 10 square inches of material so much. Myth 7: The twin turbo system will require more maintenance than a supercharged system will. Fact: This one really confuses me  . The turbocharger is such a simple device as the rotating assembly is one part housed in dual ball-bearings. A supercharger has more moving parts, especially a centrifugal supercharger with its overdriven gearing system. Additionally, any belt driven pump will require retensioning of the belt and replacement of the belt. I can guarantee there will never be a broken crankshaft bolt, broken crankshaft pulley, slipping belt or broken belt with the twin turbo system. There is no additional maint. required with the turbocharger beyond routine oil changes. It's really that simple.Myth 8: The twin turbo system suffers from excessive "turbo lag"! Fact: This has to be the most over-used statement by a supercharger salesman  . True, a twin screw pump makes nearly immediate off-idle boost which is why they are really nice for stoplight to stoplight racing. On the other hand, a centirfugal supercharger simply can't make any appriciable boost until it is a full 2/3 up the RPM scale. When you hear statements like this ask them how much boost their system makes and ask to see the boost curve the system produces on your engine. Then remember that torque (and consequently HP) at that point in the speed range follows the manifold pressure (minus any power robbed to drive the pump).Myth 9: It's simply not worth it! Fact: Beauty is always in the eye of the beholder. In my opinion the twin screw system makes a nice functional and aesthetic addition to the engine bay of any 928. Of course, I also think the twin turbo system also makes a very nice addition to the engine bay of the 928. Myth 10: A centrifugally supercharged car is faster in the real world than an equally boosted turbo car! Statement: Prove it. Myth 11: The centrifugal boys are in reactionary mode Fact: Well, I guess this in one myth that actually IS true!  Additionally I'd like to add that if people are so sure about all of their fabricated negatives of my system, why don't they come here and state these negatives to me? I think I'm pretty reasonable and use facts and not opinion to back up my statements. I would also recommend that before you make a significant purchase like this to go on and drive an equally prepared car with each of the three systems before you purchase. Come to KY any time if you would like a ride in my car as part of your comparison. Then buy what you want to buy, we live in a free market economy! We should all be happy right now, it's nearly Christmas!
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Kuhn Performance Technologies, LLC Big Gun: 1988 928S4 Twin Turbo, 5-SPD/LSD 572 RWHP, 579 RW ft-lbs, 12 psig manifold pressure. Stock Internals, 93 octane. Little Gun: 1981 928 Competition Package Twin Turbo, 375 RWHP, 415 RW ft-lbs, 10psig manifold pressure. Nikasil Block, JE2618 Pistons, 93 octane. Last edited by Herr-Kuhn; 12-08-2007 at 12:18 PM.. |
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12-08-2007, 07:02 AM
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Join Date: Dec 2007
Location: Stockton, CA
Posts: 45
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John
You live in Kentucky or Ohio???? I might have to take you up on that test ride since I have family in Ohio!!
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Brian 1984 "Estate" racer 1988 928S4 Guards red over Champagne Leather (sold) Co founder of "Stockton Sharks Society" |
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12-08-2007, 05:34 PM
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Heavy Metal Relocator
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John--
what will really settle some of this banter about which is better performance wise and such is this: do a side by side comparison of the currently available systems in real world tests. just like the automotive magazines do---sort of. your car w/turbo's same exact car with DR's SC same exact car with MR's single turbo same exact car with Murff SC same exact car with nitrous etc, etc....... same driver, same conditions, same dyno, etc...... Drag strip test, road course test, fuel mileage test, emissions test, cost comparison, ad nauseum..... What is being argued between these packages is like the argument between the naturally aspirated nitro dragsters and the blown alky drragsters. they both run in the same class, but the nitro cars are currently outrunning the alky cars, even though the alky cars are supercharged..... two different systems, but nearly the same performance numbers. you can argue with everyone about your numbers, which are great, but until you do a side by side test with equal base line cars/tests, you're just......well, you know what you're up against. and to top it all off, you're dealing with the biggest bunch of anal know-it-alls on the planet. And that hurts your efforts. keep after it, it's a fun show. --Russ
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Absence of Evidence, is not Evidence of Absence. Bill Maher 8/4/09--- "I'll show you Obama's birth certificate, when you show me Sarah Palin's high school diploma." |
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12-08-2007, 06:36 PM
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Join Date: Aug 2006
Location: Cincinnati, Ohio
Posts: 1,019
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I'm in Northern, KY...just across the Ohio river from Cincinnati. Let me know if you plan to be in the area.
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Kuhn Performance Technologies, LLC Big Gun: 1988 928S4 Twin Turbo, 5-SPD/LSD 572 RWHP, 579 RW ft-lbs, 12 psig manifold pressure. Stock Internals, 93 octane. Little Gun: 1981 928 Competition Package Twin Turbo, 375 RWHP, 415 RW ft-lbs, 10psig manifold pressure. Nikasil Block, JE2618 Pistons, 93 octane. Last edited by Herr-Kuhn; 12-08-2007 at 07:52 PM.. |
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12-08-2007, 07:46 PM
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Location: Cincinnati, Ohio
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What's the deal with all of the heat discussions going on RH? Anybody who knows anything about internal combustion engines knows that even a NA engine on full song will glow a set of headers cherry red-hot. This is a shot of a BMW M engine on full song, no turbos, normally aspirated. Heat is a function of the amount of fuel burned. Surely though, this could not be possible on a 928, not ever, right? And with a supercharger system pumping even more air and fuel it just could not be possible to glow a non-turbo manifold or a set of non-turbo headers cherry red-hot, right? I guess this pictures is just fabricated, because this just can't be possible...only turbo manifolds glow red, right? Steel glows this color at somewhere around 1000 F to 1200 F.
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Kuhn Performance Technologies, LLC Big Gun: 1988 928S4 Twin Turbo, 5-SPD/LSD 572 RWHP, 579 RW ft-lbs, 12 psig manifold pressure. Stock Internals, 93 octane. Little Gun: 1981 928 Competition Package Twin Turbo, 375 RWHP, 415 RW ft-lbs, 10psig manifold pressure. Nikasil Block, JE2618 Pistons, 93 octane. Last edited by Herr-Kuhn; 12-08-2007 at 08:00 PM.. |
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12-08-2007, 07:54 PM
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not-banned
Join Date: Jan 2004
Posts: 78
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How nice. About your points: #1 – FACT – your asking price for the hot side parts on the 16V system is higher than what I spent on my entire supercharger setup on my 81. #2 – This is a very open issue that has many factors as you already pointed out. I’ve driven turbo cars and supercharged cars with no midrange, some with no upper end, some with no low end…… #3 – I don’t recall anyone saying this anywhere. I must have missed that post. You talk about “excellent road manners” and point towards the turbo……when was the last time you actually drove a centrifugal supercharged 928? My wife and Tim’s wife have zero issues driving our cars. My wife had the “pleasure” of driving my friends turbo car a few times. Bone stock, she hated it. Made comments about “sudden power surge”. I explained how a turbo works, what lag is etc… She said “yea, that is what’s happening, I don’t like that”. She loves driving my 81. I like how you say “the” twin turbo system, when there are at least two others in the works. #4 – This can be true if the design is poor. There have been Turbo 928’s in the past that experienced timing belts that melted due to some parts being too close. I don’t see how this is possible with a supercharger. I am not trying to imply your setup will suffer from this (I know it won’t). Just sayin. #5 – So manufacturers install heat resistant exhaust valves (sodium filled in 951’s) and coated exhaust ports for marketing reasons? Factory built supercharged cars do not have these modifications. #6 – To some this is a major concern, to others it’s not an issue. Still worth addressing, and you did cut holes in the body for your setup. #7 – I disagree, just my opinion. You don’t have to like it. #8 – I’m not a supercharger salesmen, but I have driven quite a few factory (non modified) turbo systems. Every single one suffered from lag that was unacceptable to me. This even includes new cars from VW & Audi. In fact, a friend of mine just purchased a 4.2 V8 Audi A6 over the turbo version due to lag. #9 – The engine bay of your cars is awesome. I wasn’t aware the main reason to buy your kit is looks. #10 – You First. Bring your car to Road America and we’ll see after 10 laps who is in front. You, Swaybar, or Jean-Louis. Word of caution, if Jean-Louis was in a stock 78, he would probably still win. So maybe his wife Agnes should drive instead. #11 – This is sad John, even for you. You seam to imply that if Todd and Tim wanted to build a turbo car, they couldn’t figure it out or design a good one. They choose not to, big difference. Who sounds like a used car salesmen now? Oh yea, I almost forgot. You seam to think every dyno chart that has come from the centrifugal camp is bogus and falsified. Yet we go the extra distance and use four different dyno’s in our area on a regular basis. All tests are run the same way (4th gear for manual cars). You like to imply otherwise. If all goes as planned we will be at the dyno sometime this winter, and I’m sure Todd will be back on the dyno soon. You are more than welcome to supervise the operation. I did not see anyone from the “supercharger camp” ripping on your kit. But, like always, you seam to take anything said negative towards turbo’s as a whole, personally. These are NOT direct jabs towards you, many people wish you would stop taking them as such. Turbo setups are not perfect, they have negatives. Sorry if pointing them out offends you. Starting a thread like this looks like someone in "reactionary mode". Last edited by hacker-pschorr; 12-08-2007 at 09:15 PM.. |
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12-08-2007, 09:01 PM
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You've obviously taken a lot of time to develop your system and I bet it hauls ass. But this just doesn't quite cut it for me. Your idea of fact leaves a lot to be desired. Can you please address the following?
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12-08-2007, 10:00 PM
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Network Native
Join Date: Jan 2007
Location: SoCal
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So is this "discussion" going to last until the snow melts?
I don't understand why you guys are arguing turbo vs blower when we all know the way for real power is to drop in a Chevy. 
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12-08-2007, 11:38 PM
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Join Date: Aug 2006
Location: Cincinnati, Ohio
Posts: 1,019
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Erik
If you look you will see that I have given each of the builders credit where credit is due, ALL of them. You don't find post here from me stating that Tim's product isn't worth buying, will be high maintainence, etc., and I sure as heck think David Roberts' product is a very nice piece of work. Kudos to Andy Keel AND Dave Roberts for plowing the way on that system, because it is an aesthetic work of art. Kudos to Tim Murphy for making an affordabe and good performing system too. But please tell your friends to not insult me by saying my system is unproven or can't perform to the levels of a CS car on the same pressure levels. Those statements are simply not true. Erik, you are free to come to my place anytime for a ride in my car. I've ridden in V8 cars (5.0 liter big head Mustangs) with centrifugals that make 400+ RWHP and I've obviously ridden in turbo cars at the same level of power production. It's a totally different experience. You misunderstood the word "the", it was not meant to make you think there is only one way to turbo the 928 (i.e. my way). Perhaps if I had said "THE" then it woudl have been different. You see this is the problem with the internet, as you can't read my facial expression nor can I read yours. Did I ever say any other system didn't have good road manners Erik? Please don't twist around everything I say to be a negative towards you or your friends and/or their products. The fact that another system used a higher pressure ratio, less efficient compressor and burned more fuel to make the same power is conducive to making more heat. You have to think big picture here Erik, not just is what is happening right off the cylinder heads. As I said, yes the turbo car does likely see more heat on the valves, but it is no the order of magnitude you would like it to be. Has anybody bothered to look at the compressor maps on all other boosting systems before making claims on underhood heat? Any comparison made has to be done with several variables fixed. You can't compare one system on X power to the other on Y power, it doesn't work that way. As I recall the Vortechs run about 70-72%, which is good, but not as high as the turbos, therefore they are making more heat into the charge at the same pressure ratio as the turbos do. I'm unclear on why a bunch of guys who are all supercharger are so interested in making negative statements on twin turbo pricing. Where did I ever say Tim and Todd could not build a turbo car? I will say I do find it very interesting that as soon as I release data on my product that you continue to harp about how this was studied in the mid 90s and dismissed because it "wasn't worth it". Porsche doesn't agree nor do the guys that won LeMans in the Garrett ball bearing twin turbo powered Audi R8. Only I know my costs, labor time and what profit margin I want to make. And only I know what is involved with the installation. There is nobody else who knows this information and anyway Erik, why does it matter to you to begin with, you already said you didn't want one, right? So don't buy it, but please extend me the courtesy of actually releasing the pricing before you and your friends jump all over me about it. That is "reactionary" and exactly what I was referring to. People who don't want to cut the body won't buy the product, but either way is has no impact on you whatsoever, so why even make the statement? You and your friends reacted to my results Erik, it is so obvious. I can't even put an ad on E-bay without you and your posse attacking me on it on some stupid internet forum. Grow up for Pete's sake, everybody knows your game here Erik. No joke, I often wonder if you guys are on a sales commission plan. The comparison on the 4.2 Audi and the 2.7T is useless because the 2.7T is 250 HP and the 4.2 is 300 HP in the same basic chassis. The 2.7has virtually zero lag (I know my mother has one and I've spent some time in it). The NA 4.2 simply has 50 more HP, more torque, and is faster, forget mention that it has bigger wheels, suspension, brakes, creature comforts. It's just a nicer car period. The 2.7 can easily be built to 400 HP to make the 4.2 feel doggy. Again, big picture, and as always, apples to apples. Mysterious Michagan Screw Pump Man: My system will not be offered at 2X what a supercharger is selling for. What do you mean "How can this be true?" What kind of leading statement is that anyway? This can be true and is fact because I designed it, I know the costs, and I will set the price. The first two of those three are done, the third is not, so it is therefore complete speculation for anybody to make statement on something they can't possibly have any information on. Do you know what my intercoolers cost, or the water pump, or the head flanges? No, because nobody knows or has the rights to even buy those parts since my company owns the designs. About the only piece anybody could possibly look up is the turbos and as a small business owner I pay a price lower than retail, so it's really impossible for anybody to know my numbers there too. Your statement about "bankrupting myself"??? Where in creation did that come from? I'll assure you there is less money in my car than in your's and many others out there too. It's hard work and took a lot of time and effort in an environment of being continually attacked, but it is far from bankrupting me. I'm glad everybody knows my financial status in life now too. Thanks. Is this a satisfactory answer for you regarding the "price"? You completely misunderstood the point I was making on over-revving. I was not even referencing overrevving the SC to get the desired boost pressure, but rather referring to if you over-rev the engine and listing what happens if you do so with each of the three systems. The TS and Turbo will not overboost, whereas a CS will because the shaft speed of the compressor went past its designed setting (for that application) and therefore made higher boost. Spin it to 7K and watch the boost overshoot what you designed it for. I'm sorry if that was unclear, but I think you totally misunderstood what I was saying there. The reason Top Fuel dragsters don't run turbos is because they were banned a long time ago after being penalized and having to add hundreds of lbs. becasue they were out ahead of the blower cars. Besides this point, I never viewed the 928 as a drag race type of car, that is never what it was designed to be. To me it's about mid range and top end in this car. You guys keep talking lag, lag, lag. My system runs high-medium sized ball bearing turbochargers that come on gangbusters (i.e. full boost) by about 3K and in fact can make several psi below 2000 rpm when the loads are high. Since the system retains the stock intake manifold, the torque numbers mid and high range are massive. Once I hit 2nd gear I never really leave boost and the fact that is does roll on allows the car to be easily controlled between shifts. Again, since the 928 is basically a mid range and top end car the turbos are sized to hit the sweet spot when you are running flat out but to not be jumpy around town. They are therefore properly sized for a V8. Consider where you shift and where that will land you on the torque curve when the next higher gear is selected. Have you ever driven a properly setup turbo car with an automatic transmission? Well let me tell you, you can load up the engine hard by applying the brake and throttle, basically erasing any vacuum in the engine and in some cases building a bit of boost. Then when you turn it loose, you leave the line with full manifold pressure. The twin turbo Goldmember manages 5.1 seconds 0-60 MPH and it's a silly 1980 3-sp automatic car with a 4.5 liter and tiny K-24 turbos. That car could barely do 8.5 seconds 0-60 when I bought it. It too was very streetable! That's how turbos are used on the drag strip and real world to get to unheard of times with such small displacements. I don't believe, not for one minute, that the turbo car requires more frequent oil changes at all. As stated, if you follow a regular diligent standard oil change schudule (as any high performance car owner does anyway), there is no issue. The fact that the system was designed with a 5-minute post shut down water circulation pump makes certain the turbos stay plenty cool. There is no additional maintenance with a turbocharged engine as you state above. I should know, all three of my cars are turbocharged and my Audi is closing on 300,000 miles and was upgraded to a big KKK RS2 turbo at 200K miles. I've run stock liquid cooled turbos on Audis for 200,000 miles on a standard 5,000 to 7,000 mile oil change interval for 8 years and the turbos are still fine with completely acceptable shaft play. How long does a supercharger last? I ask the question and I'm sure you can give the answer back. Just like I offered Erik, you are welcome to come here and get a ride in my car. I'll assure you you won't get out and mention the word turbo lag after the experience. I can tip in my throttle 1/3 open and build all my boost at very low RPMs. This coupled with the rest of the system design makes the car incredibly fast. Look at the credentials sheets on my car and then take a look at all the others. It flat out makes more HP and torque than any other system. Again guys, I do appreciate you coming here to have this debate, I really do. Let's keep it open, honest, and factual. I'll be glad to answer any questions you have or if you want to talk in person feel free to call the business line at 859.781.9288
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Kuhn Performance Technologies, LLC Big Gun: 1988 928S4 Twin Turbo, 5-SPD/LSD 572 RWHP, 579 RW ft-lbs, 12 psig manifold pressure. Stock Internals, 93 octane. Little Gun: 1981 928 Competition Package Twin Turbo, 375 RWHP, 415 RW ft-lbs, 10psig manifold pressure. Nikasil Block, JE2618 Pistons, 93 octane. Last edited by Herr-Kuhn; 12-12-2007 at 12:00 PM.. |
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12-09-2007, 05:43 AM
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Heavy Metal Relocator
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John-
I wasn't aware that I said anything about heat production, or its use..... All I pointed out was that in this discussion between who's the top dog on the block, it would be nice to do some real world testing to see just where the king of the hill really is...... Short of that, it's one opinion to another. ( And no, I won't get into a discussion about dyno numbers and what they tell you, because there will be another discourse about how the numbers were produced with what car, what altitude, blah, blah, blah.....) I will, however, add this: lifespan of any particular engine component, whether it be the turbocharger or supercharger is greatly dependent upon the amount of servicing and the components design. In my experience, in the diesel truck world, turbos are not as long lasting as superchargers. 1. I've had two Detroit Diesels with superchargers that were never rebuilt nor failed in over 2 million miles. 2. I have had 7 other engines (CAT, Detroit Diesel, Cummins) in my fleet, and have replaced 9 turbochargers due to failure or necessary rebuilds. Lastly, a good friend of mine up in Arkansas, running a 6-71 supercharger on his stroked and bored BBC (over 600 cubic inches--in a 70 Chevelle convertible, no less), has run his blower motor for over 25 years without any supercharger related failures. And he runs his blower at 25% overdrive, producing nearly 30 psi on race gas. Yes, he has had other failures with the engine, but no supercharger/belt /drive pulley failures in 25 years... What I'm trying to say is that there will be folks that have had good experiences with both, and none of the above. Until all of you guys get together and do a real test with a base line car, it's all "mine is better than yours, yours is not better than mine, etc......" I am still amused with the idea of force feeding an engine that's got 100,000 plus miles on it with even cracking the heads off of it to see if there is a head gasket left.......) ---Russ
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Absence of Evidence, is not Evidence of Absence. Bill Maher 8/4/09--- "I'll show you Obama's birth certificate, when you show me Sarah Palin's high school diploma." |
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12-09-2007, 03:50 PM
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not-banned
Join Date: Jan 2004
Posts: 78
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Funny how the ONLY place your brother could have received that e-mail address was from YOU. Yes I took that personal. That was way over the line John. If you had something to say to me, have the guts to say it yourself. Don't sent in your brother. Quote:
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Just to repeat myself here. You really need to re-read my posts (and many others) since I did not see (could have missed it) where anyone was ripping on anything specifically you have created. I did take a jab at Callaway, I cannot help it if you took that personally. Good luck John. Selling a good product is only 10% the actual product. The rest is you. I love 928's, that is well known and I applaud anything that enhances the performance of any 928. Even a pair of turbo’s. If you really want to “bury the hatchet” on all of this BS – you first. No more BS posts about false dyno runs or fabricated dyno sheets. When YOU start using 3-4 different dyno’s to verify results (like we do up here) let me know. Funny thing is, Tim has been sick as a dog the past week or so and I think he's missed all the fun going on between the threads. Chow
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12-10-2007, 05:50 AM
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Heavy Metal Relocator
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I propose this:
everyone who's marketing some sort of power addition (stroker, turbo, supercharger, nitrous.....whatever): Bring it to Houston sometime this coming summer. Why Houston? Several reasons.....but mainly it's the HEAT AND HUMIDITY. We have a really nice dragstrip (Houston Raceway Park). We have a few nice road courses nearby (TWS, MSR, the 610 Loop) The local chapter of PCA (Lone Star Region) might even sponsor a "dyno day" at one of the local Porsche shops.... Bring your mess here for some real world testing, in the climate that puts a real strain on things mechanical. Make it a week long event, so you can do the drag strip test, the road course test, the dyno test, ad nauseum...... Just make sure you have price lists, product availability, sales ppw, videos, scantily clad teenage girls (well, maybe not teenage), etc. AND MOST IMPORTANTLY: Full, honest, disclosure about what your car has in it (or not). and just like running in a sanctioned event, be subject to tear down for verification. after all is said and done, put the numbers together and then continue this wonderful discourse we're having about who's got the biggest/best stick on the block----- ----Russ
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Absence of Evidence, is not Evidence of Absence. Bill Maher 8/4/09--- "I'll show you Obama's birth certificate, when you show me Sarah Palin's high school diploma." |
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12-10-2007, 07:28 AM
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Registered
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Location: Cincinnati, Ohio
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Erik,
If you want to come here to debate turbo vs CS supercharger on the 928 we can do that, but I refuse to have any further conversations over what has transpired over the last 4 years between you, myself, and/or anybody else for that matter. We will take care of that offline and/or over the phone. If you have a statement to make or a question to ask, ask it and I will be glad to answer.
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Kuhn Performance Technologies, LLC Big Gun: 1988 928S4 Twin Turbo, 5-SPD/LSD 572 RWHP, 579 RW ft-lbs, 12 psig manifold pressure. Stock Internals, 93 octane. Little Gun: 1981 928 Competition Package Twin Turbo, 375 RWHP, 415 RW ft-lbs, 10psig manifold pressure. Nikasil Block, JE2618 Pistons, 93 octane. |
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12-10-2007, 01:44 PM
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Unfair and Unbalanced
Join Date: Jul 2004
Location: From the misty mountains to the bayou country
Posts: 9,711
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Wow! The debate over what makes the most power has long been settled among the folks I know. Look at any racing class, period, let turbos in, they will own the class. Feel free to show me otherwise. It might not happen immediately. Once they get the turbos sorted out, game over. After that it goes to, add weight, restrict the size of the turbo, etc, etc. Bottom line, turbos spin basically for free, SC takes power to spin.
SC's have more initial grunt but my NA car can spin the tires all I want. In fact, a properly set up turbo would have a major advantage in the 1/4 mi because of this. Turbo, progressive boost controller, turn out the lights, the party's over.
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"SARAH'S INSIDE Obama's head!!!! He doesn't know whether to defacate or wind his watch!!!!" ~ Dennis Miller! |
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12-10-2007, 02:22 PM
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Thanks for the response Mule. You seem to understand the differences.
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Kuhn Performance Technologies, LLC Big Gun: 1988 928S4 Twin Turbo, 5-SPD/LSD 572 RWHP, 579 RW ft-lbs, 12 psig manifold pressure. Stock Internals, 93 octane. Little Gun: 1981 928 Competition Package Twin Turbo, 375 RWHP, 415 RW ft-lbs, 10psig manifold pressure. Nikasil Block, JE2618 Pistons, 93 octane. |
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12-10-2007, 02:49 PM
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http://www.youtube.com/watch?v=Z3iBKwcQ3Yc&feature=related
http://www.youtube.com/watch?v=poCsdMrm998&feature=related Some good video from Mr. Banks on the subject. Listen to his direct comments on turbocharging on part 2. This man has more experience with forced induction than just about anybody else living today.
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Kuhn Performance Technologies, LLC Big Gun: 1988 928S4 Twin Turbo, 5-SPD/LSD 572 RWHP, 579 RW ft-lbs, 12 psig manifold pressure. Stock Internals, 93 octane. Little Gun: 1981 928 Competition Package Twin Turbo, 375 RWHP, 415 RW ft-lbs, 10psig manifold pressure. Nikasil Block, JE2618 Pistons, 93 octane. Last edited by Herr-Kuhn; 12-10-2007 at 03:11 PM.. |
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12-10-2007, 03:02 PM
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Banned
Join Date: Mar 2007
Location: Ft.Lauderdale, FLORIDA
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Wow...
Well, Erik, if you work your way down to Florida again...remember, my original offer stands. If you want to take my 928 for a few days down to the keys, it's yours. But I expect a full tank of gas when I get home... Anyway, I still don't understand all the fighting. Supercharging is supercharging, whether it is powered via belt or exhaust gases. Sometimes I think that people personify technology; that is, if they purchase one type of equipment, then they somehow feel that people that purchase the other type are stupid or inferior or less informed. It probably goes even deeper than that. People actually identify with certain types of technology, and develop a "block" towards alternatives. I find myself doing this exactly with pushrod valve trains. For some reason I find this feature so bizarre and backward that I won't even consider buying a car from the main proponent of this technology, the general motors corporation. [see! I didn't even capitalize that proper name...] You get the idea. I've come to the conclusion that we, members of our species, have a decided tendency to "pick sides". Twin screw: Instant power, though it probably isn't as efficient as the C-fugal blowers. Great fun if you love to leave stop lights RIGHT NOW. Downside: Wheel hop. 928's have IRS rear suspensions, and these aren't the best for transmitting high amounts of torque quickly. And it has a belt dragging against your crankshaft, putting wear and tear on the front engine bearing. And I read that the Eaton blower that Ford attached to the supercharged V6 Ford Thunderbirds could use up as much as 45 horsepower at full RPM... Centrifugal: Perfect if you want to autocross. The power builds gently, so you can enter a curve and not have to worry about a gas pedal that is so "sensitive" [remember, instant power...] that it causes you to mess up the balance that you've worked to maintain so that you don't understeer. The problem is... it still needs to spool up, and you are of course subject to that BELT. And it uses horsepower. See above- Turbocharger: These use an impellor spinning at speeds of upwards of 100,000 rpm to produce boost to the engine. The impellor is small, but it still needs a second or two to reach the sort of speeds where it will produce boost. Not the hot tip if you are exiting a curve on a race track, and want instant torque right now to get around another car. Also, if the turbo spools when you are not expecting it...it can lead to something that bit a friend of mine: Oversteer. He drove his T-bird turbocoupe into a tree when we were in college when the big turbo on his four-cylinder finally spooled up, and the sudden torque cause the car to violently oversteer, right over the curb and right into a maple tree. Turbo's work when they want, not when you want them too, and that is the problem. -If I were going to boost my car, I'd probaby ask John or Mark down in Austin to figure out a way to fit a turbo. Why? Simple. I like the way that power builds with a turbocharger- it is a great rush, and I'm not racing my car [yet...]. The torque starts soft, and then builds...and builds, and then the car basicaly goes berzerk. I love that effect! I'd own a 951 if they sounded like a 928 with a good exhaust and well, looked like a 928! See? It is purely personal preference. Andrew Olson loves his Detroit-style "stomp it and go" twin screw, and Erik probably prefers his centrifugal blower because it is best for autocrossing. John just likes the technical challenge of designing and building what amounts to an OEM-spec turbocharger system on his Porsche. We're all having fun right? N Last edited by Normy; 12-10-2007 at 05:34 PM.. |
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12-10-2007, 05:28 PM
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http://209.85.165.104/search?q=cache:c8-dTKye5GAJ:media.gm.com/division/powertrain/products/engine/carengines/2004/lsj_final.doc+SUPERCHARGED+SODIUM+FILLED+EXHAUST+V ALVES&hl=en&ct=clnk&cd=1&gl=us
Since we were debating the "need" for sodium filled exhaust valves on a turbocharged car and some were saying they were not needed on a supercharged car, well please see above. GM seems to have fitted sodium filled exhaust valves to their supercharged Ecotec engine. Does this mean I think that sodium filled valves are a must to bolt a turbo on a 928? No, but the point here is all forms of forced induction place higher thermal loads on the exhaust valves. The thought that one system needs these while another can get off scott-free is another myth. The statement that OEMs do not install sodium filled exhaust valves on a supercharged car is false. Race a twin turbo or a supercharged car and you want the extra insurance?, then go ahead and install them. Is it better? Of course it is. Do I think all owners of supercharged 928s should be worried of exhaust valve melt-down? Of course not!...but please let's stop throwing things the turbocharger's way about this sodium filled exhaust valve topic. Here we have a simple 2.0 liter GM powerplant with a positive displacement pump that has the sodium filled exhaust valves fitted by the OEM. One should consider how much more time this engine stays on boost compared to a supercharged or turbocharged V8. I'll go on a limb here and say the valves in a boosted 4 cylinder see way more thermal load than they would in a V8 turbo or supercharged car. You just don't need to hold your foot into it that long with the big V8.
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Kuhn Performance Technologies, LLC Big Gun: 1988 928S4 Twin Turbo, 5-SPD/LSD 572 RWHP, 579 RW ft-lbs, 12 psig manifold pressure. Stock Internals, 93 octane. Little Gun: 1981 928 Competition Package Twin Turbo, 375 RWHP, 415 RW ft-lbs, 10psig manifold pressure. Nikasil Block, JE2618 Pistons, 93 octane. Last edited by Herr-Kuhn; 12-10-2007 at 07:51 PM.. |
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12-10-2007, 07:13 PM
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Speaking about valves.
Does anyone know where one could find sodium filled valves for the 85/86 engines. |
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12-10-2007, 07:42 PM
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In case any of you want to buy a set of sodium filled exhaust valves, here are a set that belong in a normally aspirated, caurberated big V8.
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Kuhn Performance Technologies, LLC Big Gun: 1988 928S4 Twin Turbo, 5-SPD/LSD 572 RWHP, 579 RW ft-lbs, 12 psig manifold pressure. Stock Internals, 93 octane. Little Gun: 1981 928 Competition Package Twin Turbo, 375 RWHP, 415 RW ft-lbs, 10psig manifold pressure. Nikasil Block, JE2618 Pistons, 93 octane. |
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12-10-2007, 07:45 PM
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