Latest Project - Headers

[911st]

I am not challenging, just dissecting to better understand.

What had me most was 400chp through a stock intercooler and that proved to be miss information.

I have seen that level of HP through stock ports before, though rare, but I belive the fueling to be questionable and in need of attention. I can see 12.5/1 in the meat of the power curve but not in the 6k rpm range. I could be wrong.

IMO, stock WUR & Fuel Dist runs out at about 350whp, with modified WUR at about 400whp.

By it's nature we usually see a lot of mods made in the effort to make big HP.

However, what I think I am seeing is the bigest consistent factors to making 400whp seems to be a big efficient turbo (these often come with boost creap if matched with a 1 bar WR) an open muffler, cool air (intercooler) and 1bar or more boost.

Ports, headers, and cams and should be concidered part of a ballanced build but do not seem to be totally necessary to make big HP.

This is not ment to lessen the contribuition of the headers as I am sure in this case they are a key part of his success.

JMO based on what I have learned so far.

[JFairman]

If equal length primary tube headers really made a bunch more power and had less turbo lag then short primary tube header designs then how come Porsche never used them on the turbocharged 934 or 935, and instead they used short log type headers.

I really think they coulda woulda used larger equal length headers if they found they made more power with less turbo lag than what they were using.

What headers does Eddie Bello use on his twin turbo 1000+hp motor?

He probably makes his own and from what I've heard they are not an equal length primary tube design.

[RarlyL8]

The topic of this thread is headers, nothing else. That is all I am concerned with.
Don't care about fuel or intercoolers or anything else that is put in place to support the power. Those items will take care of themselves for the sake of longevity.

The point I am focusing on is that the only change made to the stock long block is cam shafts. No head work. You can change a set of cam shafts with the engine in the car. What this tells us is that 400WHP is possible without an engine removal or rebuild. That is huge money saved for those interested.

For the sake of argument, if 400WHP seems impossible then lower that expectation to say 385WHP. I don' think anyone would be unhappy with that power.

When all is said and done I will dyno my power package: headers, muffler, K27HF, and my intercooler at 1bar. I have no doubt I'll hit at least 385WHP with my stock heads and SC cams.

[Speedy Squirrel]

The '77 to '79 system with thermal reactors is just bad. In addition to the thermal reactor itself, having tubes going at right angles into a log is bad because the shock wave bounces off the opposite wall. I posted an SAE paper reference on this some time back.

Ther is no benefit to equal length on a turbo motor. The turbo is not an open end, so the reflected pulse is very very weak. When you couple this with a low overlap (very low in most 930's) you have very limited scavenge capability. Best to save that energy to expand into the turbine using low volume pipes.

I think Eddie uses twin turbos, in which case none of the above applies. Twin turbos can have it all; short and equal length, with pulse conversion to boot.

[JFairman]

What Speedy says is correct about exhaust scavanging in the rear engine 911 turbo with it's space constraints and short overlap valve timing.. and it becomes even more so with a high backpressure K27 HFS heat meister bolted to it.

If you have those aluminum heat exchangers on your car when you dyno it with the HFS, watch them warp and melt off the headers when the primary tubes are glowing red hot. Same thing will happen to anyone using them on the track.

As far as the log type headers I mentioned, the primary tube curves before joining the log so the exhaust pulse should flow into the log without bouncing off the other side much,

This may be a picture David Cole took of his 934 headers and posted a while back... I saved it, and it shows the short curved primary tubes and log design with no common conical shaped collector.

[RarlyL8]

Ther is no benefit to equal length on a turbo motor.

This has been proven over and over to simply not be true. My headers and all the other equal length 930 headers such as Holcomb/Mode/Manzie etc are testament to this. Why would anyone spend $4000 on a set of 930 headers if $1000 shorties will do?

I have replaced SEVERAL aftermarket headers with mine: OBX, B&B, GHL, SSI, GSF and FabSpeed. Every single replacement out-performed the original and the owners were blown away. Yes it is a combination of many parts of the design but equal length most certainly plays into it. If nothing else the sound is worth the effort.

Why don't others do it? Not the same application. Ask them.

[David]

If Mark Donahue's book "The Unfair Advantage" is any indication, I think back in the day Porsche built race engines for peak HP not drive ability. This may be why they didn't bother with equal length headers on the 935.

[911st]

Originally Posted by RarlyL8

The topic of this thread is headers, nothing else. That is all I am concerned with...

Then maybe offer up before and after examples where it is just the headers are changed.

Don't care about fuel or intercoolers or anything else that is put in place to support the power. Those items will take care of themselves for the sake of longevity.

AFR, intercooler, and boost level may be safety items but they are also relevant to power made. 12.5/1 makes more power than a CIS safe AFR in the mid 11's. It is widely accepted that a good intercooler is good for about 30hp by its self. And boost...

The point I am focusing on is that the only change made to the stock long block is cam shafts. No head work. You can change a set of cam shafts with the engine in the car. What this tells us is that 400WHP is possible without an engine removal or rebuild. That is huge money saved for those interested...

Now you are no longer just talking about headers, you are bringing port size and cams back into the discussion.


Get that motor to a safe AFR and verify the big turbo is not over boosting higher than 1 bar and if it still makes 400whp it will be a lot more interesting.

[911st]

BTW, I love your headers and would buy them.

[RarlyL8]

Keith, that is where the 385WHP concession comes in.
We all know that all components play a part and they are all common and necessary to the build. It's a general and known formula. Any variables such as a touch of overboost or high AFRs or a cold day etc etc will all increase power a little, or take less power away if you look at it in that manner. I understand and acknowledge that.
This one data point is a good number that I expect to be repeated with other clients and a number I can and will verify with my own car.

[copbait73]

Originally Posted by JFairman

This may be a picture David Cole took of his 934 headers and posted a while back... I saved it, and it shows the short curved primary tubes and log design with no common conical shaped collector.

While here just add a picture of the total absence of any ground clearance once you flip the transaxel over. Don't make assumptions the factory could avoid making serious compromises to the exhaust systems driven by the boxer layout.
This was and still is a problem.

[911st]

I find the question of port size very interesting.

As noted, I have seen 400whp and more reported with stock ports so they do not have to be a restriction.

However, what I think I am seeing is it takes over 1 bar, at least in the cases I have seen reported, to get there with stock ports. I do not know if the cylinder is actually seeing 1 bar.

It seems that motors that do have the advantage of intake and quality head work seem to be able to make the same HP numbers at a lower boost.

I have in at least one case had a fellow C2 Turbo owner with stock Porsche heat exchangers, a 60-1 Turbo, open muffler, and just over 1 bar boost report hitting 400whp with not just the stock HE's and ports but with the --'stock cam'.

My guess is intercooler and turbo efficiency are keys to get as compact of a air fuel mix as possible and sufficient boost to get it past the small intake port and modest cam duration.


I suspect 'changing cams' is more than an in car project. Spring height should be changed or sport springs installed to deal with the more aggressive lift and the rockers should probably be resurfaced to aid rocker to cam brake in.

[911st]

Thinking out loud.

With stock ports, adding cam lift basically dose nothing on a 930. I did some calculations and the intake valve at about 40% lift is equaling port capacity.

It is the added duration that we are after to make stock ports work better. A stock 930 cam has 209 deg duration, SC 229 and C2 240 deg.

It looks like and SC cam might flow up to about 10% more and the C2 about 15%.

Not sure how much more boost it would take with stock cams to match an upgrade cam assunming the intake is the restriction.

The effect of cam timing moving the power band up the rpm scale is a different benefit. Re timing the stock cam can achieve some of that.

Lastly, opening the intake port with stock cams so it can flow 10-15% more might equal the benefit of adding a cam to stock ports and be more of a benifit to the low end. Do both and we are looking at 30% or more intake flow potential.

Fun!

[RarlyL8]

My focus is bolt-on power, there are other "ultimate" threads that cover cams, intake and head work.

It is comon knowlege that cams and turbos should be matched for optimum performance. The 964 cams and HFS turbo are a good match. The engine in question had a set of Brand X headers and Brand Y muffler, not a stock exhaust. replacing Brands X and Y with Brand RL8 made a huge difference. The cams were mensioned as they were the only non-stock item inside the engine.

I've never heard of a stock engine with stock J-pipe exchangers hitting 400WHP @ 1bar. Would like to know more about how that was done. If so I should be looking way past 400WHP with my system on a stock engine.

[JBL930]

400WHP with stock head studs is pushing it as it is don't you think?

Does anyone know what the stock 3.3 964 WHP figures are? I'm guessing about 260, maybe 270? With your headers and muffler (and a different air box) there's a gain of 80-90WHP, that's a massive amount of power for basically very little! How much better are the SC cams compared to the stock 964 turbo cams, what amount of that power can be attributed to the different cams?

[wjfk32]

1. Some of us want that magic bullet before anyone else has it.

2. Some of us, wake up in the middle of the night thinking of an answer.

3. Some of us, will just take our cars out and BLAST FOR TOP END.

4. Some of us r looking a side by side race with a 500hp. car to get an idea of what hp it has.

5. Some of us almost go to jail or do go.

6. In the end, we just need to seetle down becuz we are all in this together, hopefully.

PS. Tonight, I am taking my Turbo out and making flames! It makes me happy!!!!

Walt

[RarlyL8]

400WHP on stock rod bolts and head studs is not harmful if you stay at 1bar and don't run past redline.

Stock C2T puts out ~270WHP.
Yes adding my headers, muffler and K27-7200 to a stock 255WHP Euro 930 will gain 90WHP. I assume that cams, HF turbo, 1bar boost and tuning take you the rest of the way. SC cams help more with torque while 964 cams carry on to the HP end of the power curve.

Yes it's all about the experience! TGIF!

[911st]

The C2T with 60-1 turbo, muffler and stock HE's had to run in the 1.1 to 1.2 bar range to get to 400whp.

Looking forward to your big turbo and 1 bar.

If you are making 350whp at 1.75 bars, you should make about 400whp at 2 bars ((1.75/2) x 350)= 400) if somthing dose not start creating a bottle neck.

[PorscheGAL]

Went driving this evening and just wanted to share the sounds of Brian's exhaust. I didn't get a chance for WOT and I was mostly working on recording. It is hard to capture exterior sound without all the wind noise. Anyway, thought you might enjoy this short video. Also, couldn't help but run into a trooper and then a confused car on the exit.



YouTube - RarlyL8 Headers Video

[e170drvr]

Stephanie, nice video! What did you use to record the sound? I think we have the same setup. I tried to record mine but the sound quality was terrible! My car sounds exactly like yours. Absolutely wonderful! Huge smiles every time I take the car out.