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-   -   Turbo/Cam combo (http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/375285-turbo-cam-combo.html)

lukeh 11-02-2007 10:00 AM

Turbo/Cam combo
 
What turbo/cam combo would you go with on a street car that already has full B&B and a larger intercooler. I'll be doing the fuel head mode at the same time.

Thanks

ayglass 11-02-2007 11:47 AM

My thought is that it's a judgment call based on your personal values. I have what the PO installed and I think it's a pretty good choice for a street car. K27-7200, and SC cams. This combined with the GHL exhaust starts to build boost at 2400 rpm. I have 1 bar by 2700 rpm which makes the car usable on the street over a wide rev range.

What would I do differently? I have the next steps in rough order as: Modified fuel head for the safety of the engine, seal/mask the IC to the tail so that it is as effective as possible, then move to the a newer turbo like a k27hf or hfs.

My biases for a street car are: 1. Reliable conservative technology 2. broad usable power band 3. incremental changes so that I can continue to drive the car (radical makeovers on these cars seem to take them off the road for years with "one more thing" ;-)

wcc 11-02-2007 01:19 PM

Quote:

Originally Posted by ayglass (Post 3565936)
My thought is that it's a judgment call based on your personal values. I have what the PO installed and I think it's a pretty good choice for a street car. K27-7200, and SC cams. This combined with the GHL exhaust starts to build boost at 2400 rpm. I have 1 bar by 2700 rpm which makes the car usable on the street over a wide rev range.

What would I do differently? I have the next steps in rough order as: Modified fuel head for the safety of the engine, seal/mask the IC to the tail so that it is as effective as possible, then move to the a newer turbo like a k27hf or hfs.

My biases for a street car are: 1. Reliable conservative technology 2. broad usable power band 3. incremental changes so that I can continue to drive the car (radical makeovers on these cars seem to take them off the road for years with "one more thing" ;-)

I'm glad you posted. This is the exact system I've been slowly installing. I have a set of GHL headers and a K27 7200 sitting on the shelf waiting for installation. I also have the B&B intercooler, GHL muffler, and a 1.0BAR spring already installed. The SC cams will be in the future somtime. But I was wondering if you have or notice any boost creep? This has been my only concern. To the point I've considered not installing all this stuff. Maybe I'm just paranoid. :rolleyes:

pdqcarrera 11-02-2007 02:19 PM

My only issue with the SC cams is that they just plain die too soon. Not a bad match for a stock turbo or a 7200, but if you're going to step up to a higher flow turbo you're going to waste it without more top end from your cams.

Speaking of which, anybody here tried a Web 20/21 cam in a CIS 930? There are some good hybrid cams offering performance between SC and 964 cams.

ayglass 11-02-2007 04:17 PM

Hey BIll,

I definitely have boost creep. I have a .8 bar spring in there and I get just a little over 1 bar. So far it hasn't been destructive to the engine and I am OK with 1 bar. My only caveat would be with the GHL muffler. It was a little too resonant around 2200 to 2800 rpm for my taste. I switched to the Fabspeed for that reason and might soon give RarlyL8's a try. I had to uninstall a badly-done stereo and weld up the holes first, now I'm installing a better/complete sound pad behind the back seats. I love the quick spin-up, I just don't want to be deaf before I'm 50 ;-)

PDQ, let's talk about this "wasting it" thing. I am wondering if this is the racer in you wanting the most out of the mods or if I'm going to notice something new and bad if I upgrade the turbo. Right now I don't notice the car falling off before redline. Maybe a real dyno would point this out to me, I don't know. In your experience, am I going to notice a drop off with a better turbo like "it's faster to 5500 rpm and then falls back to k27-7200 levels? If I can get a faster spool with the same or more power I would consider it a win for an amateur driver like myself. If I'm going to get a kick in the pants and then a letdown that might change my direction. What do you think?

pdqcarrera 11-02-2007 05:25 PM

Definitely yes, I do want to maximize the mods, but not to the point of hurting driveability or reliability. Pretty much everything with CIS turbo is going to be some kind of compromise I suppose, but there's definitely a balance that can be struck to satisfy most tastes.

I just don't think you'll get your $ worth to change to higher flow turbo keeping SC cams (that won't efficiently use the top end), but others like Stephen/Imagine Auto are experts with a lot more data & experience than I have.

I'll have some empirical data to provide when I get my 930 off the rack with her new K27HF turbo (replacing Kokeln/Turbonetics unit). :-) My prior setup was an all or [almost] nothing power situation (the proverbial on/off switch). Very exciting when the boost came on indeed but a real handful and too scary to let the wife out in! (speaking of compromises ;-) So I'm adding an adjustable WUR to clean up the low-to-midrange efficiency, quicker spooling turbo with more than enough top end for my cams and a Tial wastegate with controller. Engine is setup for up to 1.2 bar boost but the dyno results will be deciding factor on how high she'll be able to go. It won't start spooling as low as yours, but the mid-range should be stronger and the top end a full WOW factor beyond. LOL ;-) We'll see!!!

ayglass 11-02-2007 06:31 PM

Thanks pdq,

I'm really looking forward to hearing about your new HF. Knowing when to stay with the 7200 and when to go further is going to become an important question for me if the 7200 wears out...

RarlyL8 11-02-2007 09:28 PM

You don't need the fuel head mod until the engine goes past the 350whp level. It will do nothing for you but waste gas on a moderately modded engine. It is always a good idea to verify your A/F ratios throughout the range and adjust if necessary.

Don't dismiss SC cams so easily. Combined with the right turbo and tuning they are still one of the best cams available for a street 930. I know of back-to-back testing using SC, SC330, Web, 964, and ANDIAL cams on the same engine. The SC cams won the best driveability/power compromise with 400whp and 1.0bar @2600rpm.
The best turbo? On that same test it was the K27S, again 1.0bar @ 2600rpm with 375whp.

My stock waste gate has Zerro boost creep. It jumps to 0.7bar and sticks like glue. Header design plays into this. The stock Euro exchangers use a very nice angle off the main pipe to the W/G branch. Aftermarket headers often compromise that angle and it becomes a "T" when it should be a "y" or "Y".

NathanUK 11-03-2007 02:52 AM

Brian, have you ever compared an S to a HFS at all? I would have thought the SC330 would have been a good compromise. Interesting results :)

RarlyL8 11-03-2007 07:41 AM

I don't want to get myself in trouble here.

The fellow that did all this work is a friend of mine. I helped him with the basics and he took it to the ultimate level. He was also working with a few tuners testing prototype products that are not yet for sale. Needless to say they don't want any specific information out just yet.

There is a distinct dividing line at ~375whp where you must modify the fuel system and the turbo IF driveability is a major component considered.

The SC330 cams were ultimately left in the engine because they edged out the SC cams in the HP supported and gave good driveability. (My car was used as the "baseline" for driveability using SC cams). SC330 are good cams. Understand that these are fine lines we are talking about and very subjective. It is difficult to see driveability on a dyno. The focal point was boost threshold and the subtle changes in torque at 1000-1800rpm. That involved lot of seat time and tuning.
My hat is off to the guy for his dogged persuit of the utimate in CIS tuning.

Yes, the S and HFS were compared. In this particular application the S proved to have better characteristics when used in the configuration producing <375whp while the HFS and fuel mods supported >400whp, also with good driveability but a slight reduction in fuel mileage. Remember, there was a lot of tuning involved.

Utimately you need to know exactly what your goals are. Everything must be considered, from gearing to power to fuel mileage so that you are not dissapointed.

NathanUK 11-03-2007 11:05 AM

At the moment I can only dream of 400whp. Would need to change the rod bolts for that kind of hp. I wouldn't tackle that without some expert help. Luckily my friends brother is a Porsche trained mechanic but it comes back to he knows more about the newer cars.

pdqcarrera 11-03-2007 12:12 PM

I associate RPM with rod bolt design not HP. IMHO stock is fine with stock redline.

DonE 11-03-2007 01:08 PM

I used stock rods and bolts on my 400rwhp CIS car. I now use stock rods and ARP bolts with 525rwhp EFI.

And getting a true 400rwhp with CIS is more difficult that installing a couple of "bolt-on" mods. To get 400, I had: Kokeln IC, Turbo Peformance turbo, B&B pipes (later went to custom), euro fuel system, highly mod'ed WUR, fuel head mod, ported heads, 8:1 CR, 964 cams (the best all around cam in my opinion), matched injectors, Magnaflow straight through muffler (second best thing done for HP), stock air box (drilled), 1 bar spring, extrude honed intake manifold. Most importantly, it was tuned for all these mods. It was extremely reliable (started every time - hot, cold, had great power, etc) too.

You'll notice I changed to custom pipes. There are two reasons: the B&B were falling apart (welds failing, and holes popping through in odd areas), and I needed a superior wastegate circuit.

Brian is dead on with the fuel head mod. There is much more to it - don't fall into the "irrational exuberance" of this single mod and expect more power or it to save your motor somehow.

NathanUK 11-03-2007 01:57 PM

Don, what rwhp do you think your car would have made without porting the heads, no increase in CR and leaving the manifold alone at 1bar?

DonE 11-03-2007 05:22 PM

Max HP with the above mods was 412. I did most of the mods without doing dyno's in between, so I can't really say. Maybe 375 - 390?

RarlyL8 11-03-2007 05:47 PM

The engine (long block) in the above tests was completely stock sans ported heads.
Cams, bolt-ons, and a lot of tuning got it to 400whp.
It is important to note that Don's engine and this engine arrived at the same point through convergent evolution. The optimal cam and settings for a GT turbo will not necesarily be optimal for the K27 series and vice verca.

sand_man 11-03-2007 06:09 PM

Installing K27HFS this weekend with my SC cams (currently running K27-7200). Curious to see how the car behaves.

patkeefe 11-03-2007 08:51 PM

FWIW, there is an excellent article on one of the cam manufacturers websites (Elgin, perhaps?) written by fellow Pellican jluetjen regarding cam selection and camshaft dynamics, which I found to be quite informative.

Lukesportsman 11-04-2007 07:28 PM

I have a set of 20/21's and when I called Webcam on using them in a low boost situation, they seem baffled. They first suggested their B or Evo cams as good turbo choices. I pushed on about their spec's and how it looked to be a good alternative to SC cams in a 8:1 motor for her to later agree. Just thought I add this as I agree with the above poster that they could in the right circumstances be a responsive cam that might offer a little more rpm. Webcam didn't seem aware of anyone using their cam in this manner.

I realize this offers little in opinion, but found it interesting that they, the maker, had little awareness of these alternatives to the "turbo" spec cams.

ayglass 11-04-2007 09:24 PM

Well? Well?

I am anxiously awaiting Sand_man's appraisal of the HFS turbo with the SC cams. Does it taste great? Less filling? Spool just off idle? ;-)


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