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might also think about ITB's they have a very flat torque curve.
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Old 10-28-2019, 08:48 PM
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ITB's serve little purpose for big power numbers and just add a whole bunch of tuning complexity. Just look at all the 1XXX horsepower GT-R's... every single one of them ditches the ITB's for a forward facing plenum with a giant single throttle body.
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Old 10-29-2019, 07:11 AM
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I run ITB's and make 1000+ hp. I love the ability to tune each cylinder especially since the 2 center cylinders run a bit hotter. I run individual aircraft egt sensors so I can monitor what each cylinder is doing. The throttle response in unbelievable and very few single throttles can flow as much air as 6 individual ones.
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3.3 ltr, stock compression, efi, twin turbo - no intercooler.
Old 10-29-2019, 07:41 AM
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Tuning each cylinder individually is done via fueling/spark though; I'd not suggest changing throttle angle on a per-cylinder basis to correct airflow... that will get you some F'd up results at idle and part throttle.

I'd also disagree in the statement "very few single throttle bodies can flow as much as 6 individual ones". That simply means you sized the throttle body wrong... The throttle body is NOT the restriction, the throats of the head + intake runners are. So what would you expect to flow better? A 40mm intake runner with NO obstructions, or a 40mm runner each with a throttle blade in it? Even full open, the throttle blade+shaft occupy space. For big power, single plenum is the way to go or else all drag racers/standing mile cars would have them - and they don't.
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"Frankenstein" - 964 C4 chassis/driveline - 993 widebody/Speedster look - VEMS standalone - twin plug high compression 3.6L N/A engine - 945cc cc/min injectors - Bosch 044 pump - GT45 @ 1bar/14psi - non intercooled/wingless - E85 fuel - turbo inlet water meth inj. - 3.5" exhaust - GT3RS clutch + LWFW
Old 10-29-2019, 08:12 AM
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Individual throttles have a straight flow path into the cylinder. Do you think Porsche used them for a reason. All throttle shafts occupy space. Porsche tried slide valve on the turbos but the pressure would jam the plates. Want to put it to the test, be glad to race you anywhere.
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3.3 ltr, stock compression, efi, twin turbo - no intercooler.
Old 10-29-2019, 08:20 AM
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GJF, I have 930 heads, but the valves and ports are going to have to support power past 8000rpm. Consequently I am going with 51mm/43mm valves and 43mm/39mm ports. These are going to be mated to 996 GT3 intake manifolds.
Cajundaddy, there is no way of making aircooled heads watercooled and it is not necessary.
Mike, Xtreme does a great job from what I have read, but I used to port heads for a living and plan on doing as much as I can myself.
Porsche 935, there was about 5.5-6.0mm machined off the case surface, basically just enough to have a flat surface including the area surrounding the head stud holes and even left to right. The cylinders are correspondingly longer, so that the cylinder head surface is the same distance from the crankshaft centerline as originally. And the pistons have the wristpins offset, so that they compensate for the difference in crankshaft stroke and the extra length from the 3.0 rods.
Boosted79, way more complicated than is necessary, if I do not have to meet emission standards. This is going to be for WFO , so like you said, not really worth it.
Porsche 935, Eddie Bello's original SC had twin throttle bodies too, but no sequential turbos.
Ken911, 993Speedster, Porsche935, ITBs do not make more power by themselves compared to a good single TB manifold at 100% throttle. They do not add any complexity to tuning, but rather help with part throttle when running a camshaft with a lot of overlap. When running a camshaft with little overlap, then there is very little benefit. Since I am not planning on running a camshaft with a lot of overlap, there is no benefit for me, just added cost.
Old 10-29-2019, 12:11 PM
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I run quite a bit of overlap, had pockets in pistons cut another hundred thousands to clear valves. But my power peaks around 7300 rpm. I believe overlap helps reduce cylinder pressure, especially when running 25 lbs of boost and more. I never saw Eddies SC but I hooked up with him when he was here in Florida. Nice guy. The C2 really sounded good. And he drove it everywhere. What kind of weight do you think the car will be at?
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Old 10-29-2019, 12:24 PM
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If you are running a fair amount of overlap, your car would stumble and stall on part throttle without the ITBs. But the power peak is determined by port size, camshaft duration and turbo size, which I am sure you know. But with tight camshaft centerlines you end up with higher torque peaks at the cost of a shorter powerband. Plus driveability suffers, if that is something you are worried about (not a big concern of mine). My concern is having a flatter torque curve, that carries further to the right without dropping off too fast.
Old 10-29-2019, 01:40 PM
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How do you plan on transitioning the oval port of the GT3 intake to the round port of your 930 ports?
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Old 10-29-2019, 04:50 PM
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My car is fairly light, so hp curve was more important, especially with the regeared turbo box. I stay on boost longer with the higher gear sets. Traction is the only issue I have on the streets. With mild throttle I still see 70-100 in 2.4 seconds in second and pull to 180 in 3rd at 7800 rpm. How will you get power to the ground?
Old 10-29-2019, 04:50 PM
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GJF, I will only only be using the upper part of the manifold and custom make the lowers.
Porsche935, that is another issue which I can hopefully address with the tune when the time comes.
But Eddie Bello managed it with small tires, a heavier car (3000 lb) and more power on a single TB. Since I have not even driven my car for over 20 years, I have a steep learning curve ahead of me.
Old 10-29-2019, 06:15 PM
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Drag cars run the 1/8th mile in the 4's on 275mm drag radials. Getting the power to the ground should not be a problem, especially with most of the weight of a 930 sitting on and behind the rear wheels.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 10-29-2019, 06:25 PM
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I am curious on the outcome... So get to fabricating!!
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Old 10-29-2019, 06:33 PM
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Ya
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Old 10-29-2019, 08:31 PM
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Drag radials are hard to drive on. If you change tires for events, I can see hooking up is possible. I run drag radials on one of my other cars and running 14psi of air does not make for a fun turn. A lot of records and events are run on dedicated tires. But doing it in street trim in an older car takes finesse. No traction control, no launch control. You can add boost by speed or boost by gear may help. Looking forward to a video when done.
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3.3 ltr, stock compression, efi, twin turbo - no intercooler.
Old 10-30-2019, 04:50 AM
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Quote:
Originally Posted by Ollies930 View Post
First picture shows flat surface for cylinders including surface surrounding stud holes.
Second pic close up of Ollies boattailing
Third is cylinder with wide sealing surface encompassing stud holes.
Fourth and fifth stud holes full length from sealing surface to cylinder base.
Very neat stuff!

From the picture, it looks like the cylinder liner is "T" shaped and it is also the mating surface for the cylinder heads. Is it a metal to metal fit or is there a head gasket used? No flame ring?

I'm assuming you have to machine the cylinder heads to fit the profile of the cylinders too.

Custom base gaskets? Let's see more of these awesome goodies!
Old 10-30-2019, 05:41 AM
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I run drag radials full time on my 930, normal tire pressure. A buddy with a 1000+HP 'vette uses the same tires full time and does not reduce pressure. Drives from the beach to the track, clips off 6.1 sec 1/8th then drives home. It's doable. The only problem he has is the tires have to be warm before they hook up.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 10-30-2019, 06:48 AM
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My drag radial car runs 5.83 in the 1/8th but I run 12 psi air and need a few burn outs. You can run more pressure but for optimal traction different sizes and widths have specific recomendations depending on height and width. Most drive with more pressure and reduce for optimal traction at the track. But if he can do both at same pressures, got to applaud that. Vette turbo or supercharged? Has he ever road raced it?
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3.3 ltr, stock compression, efi, twin turbo - no intercooler.
Old 10-30-2019, 07:32 AM
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Finally some builds that make serious power!

Wished I was nearby to help where I could...
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Old 10-30-2019, 09:33 AM
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His goal for the 'vette was to have the most streetable daily driven car possible that could get in the 6's without changing anything. A crazy amount of work went into the build. He met the goal and then some. You would never know the car was anything more than stock. He once drove to the Tail of the Dragon and got a call from his buddies that they were going to the drag strip that evening. He jumped in and drove the few hours (getting 27mpg @ 80mph) straight to the track. With his travel bag in the rear hatch and standard tire air pressure he pulled off a 6.3 sec 1/8th. Engine is a truck block 348 LS supercharged with MeOH injection. Best time he achieved was a 6.1 after even more work fine tuning the suspension. He said power wasn't the problem it was putting the power down. Typically his street "challenges" began at 70mph. Tons of cool stories as no one expected an old guy in a plain looking convertible 'vette to be hiding all that. So if he could pull that off with a front engine car I'm sure you guys can do it in a 930.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 10-31-2019, 06:23 AM
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