Hmmm, In very few cases does this occur. Two things have to exist in order for this to be valid, one the displacement must be able to fill the cavity to the turbo in a steady state and two when the air goes to the turbo past the collector the collector has to be more efficient then the previous version this causing a high rate of velocity. If you take two identical headers and do nothing more than change size you loose bottom end and pick up top end. BTDT. You also have to consider where that band will be and what turbo you have and what range will it run in. Very rarely do you retain the same low spool levels with larger headers. Can anyone tell me what size primaries were on the old GT1s and GT2s?

 

Stephen: Yes, I agree. I assumed the inner diameters were similar (not sure from the photos).

The way I try to think about it is the headers are a highway that merges 3 lanes into 1. You want to have each car (each exhaust pressure pulse) fit right behind the other and exit the header in a nice, fast, orderly fashion. What you don’t want is cars crashing into each other, someone backing up, someone getting out of order, etc.

Stephen: How do you guys test your headers to see if there is an improvement? This seams extremely complex to me to have this work across the full rpm range.

 

Just remember, to simply bolt up headers without re tuning is moot. You may gain or your may lose power by simply bolting them on. You tune those headers and they will make power. You insulate them and they will make more. Of course, if you are going to insulate them, do it before you tune.

 

Another way to look at that is you're just trying to make up for the power you lost with the aftermarket headers.

BTW, what do the headers on the Porsche GT1 car look like? I can't imagine someone having a better design then that. Or, the headers on Tyson's old Protomotve car?

 

GT1? Street version @ 550 hp or the race version @ 600 hp? Sorry Bill, but you are living in the past. A motor tuned to S Car Go insulated headers will make more hp than the same motor tuned to the stock headers. I am not talking stock motors but ones producing 560 plus hp. Been there and done that.

I'd be very happy to do it again. Loser simply pays for the cost of setting the car up both ways and gets to write the thread spelling out the results. I'll even provide KA as the test mule. I'll bring KA down South to GIAC for the tuning. Are you game?

I'd love to dispel this myth once and for all.

 

I think there are two issues, power and lag. I would not be
surprised if a well-made set of headers like S-Car-Go's,
insulated and dynoed on a stock 996tt, and tuned optimally
might make more power than with a stock set of headers
with optimal tuning. However, I believe the tradeoff between
smooth equal-length headers and the very short stock
headers is max-flow vs compressible internal volume. I am
guessing that if you hate lag, you might want stock headers?
Chad, I'll make you a challenge. We can use my car for the test,
and whoever is right, you pay, OK? (hahah I crack myself up)
Joe

 

It might be easier if you post a video of your speedo/tach going from 60 to 130. That would dispel all myths once and for all.

 

Bill,

You answer my question with another question. Your new question doesn't appear to directly relate (or answer) to the header question?

To answer "your new" question, I'll be very happy to oblige in July when S Car Go Racing is finished with KA. I don't see exactly what this is going to prove about the headers? The question is stock 996tt headers versus aftermarket headers. Specifically the S Car Go Racing aftermarket header. Would you like to be more specific regarding your 60-130 mph test and myths?

Wherever you are going with this ...................... yes, I am game.


KPV ......... I apoligize to you about this little thread diversion.

 

Sorry I'm not as "verbose" as some others on this board. Unfortunately I just don't have the time I wish I had to discuss these issues at length. Maybe when I retire.

My only point is that in all my years of racing turbos, I've seen all this aftermarket stuff come and go (including some very fancy header designs). The bottom line is how the car performs as a package. The headers are just a very small part of that, even less for a turbo car because of the pressures differences from an NA car.

BTW, don't get the impression I'm living in the past. I've raced against the fastest cars that are built today, including some very fast Andial and Ruf cars, a CGT, twin-turbo Vipers and many others.

So, let's just see a 60 to 130 video of your speedo and tach so we can see how fast your package is. And then we can do some throttle response tests. Why do you think Ferrari and Porsche are using NA engines on their fastest cars? It's all about throttle response. I've killed 700 HP turbos on the track because I was long gone by the time they had to wait for the engine to respond to their foot! Take a ride in a CGT. You'll see what I mean.

 

Yeah, Chad. And what about turbines too? Don't forget they were
so good they were banned. It's the 'whole package' and don't
you forget it. That includes driver fitness, so let's meet at the gym
and see who's talking smack! There are so many lead-foots on
paper around here, I want to see someone put their foot where
their mouth is...
Joe

 

Headers schmeaders ... I'd smoke all you guys in my shifter kart.

 

Ken,
Why not just cut/grind out the offending header tube and weld in another one?

Dave

 

Bill,

I will agree headers do not make a large difference ......... if that is what you are looking for. Race cars as I'm sure you are aware have an inverse rate of return per dollars as you progressively move up the hp ladder.

Regarding parts that "come and go", again being involved in racing as you stated, things come and go (mostly) due to rule restrictions (changes) as Joe stated above. What 99.99% of us on the forums deal with is street cars. Some of these street cars would hand some of the cars you mentioned above their head in a basket on certain track layouts. Now I don't want to hear about longevity of the cars you mentioned because again, some of these street cars were not designed for hours of racing ............ they were designed to be very very fast street cars.

I will get a 60 to 130 time just for you. I know what you are thinking, KA is a car with about a 260 ci displacement (versus approx. 220 stock), it is a turbo and because of this it will have some lag and it's 60 to 130 time will not be very impressive. In the racing venue (with it's rules) you would be correct. We both agree KA is not a race car. It has the big turbo's and the big heads/valves/cams. It will perform best above 4000 rpm's. Somewhat like a GT3 on steroids.

I believe two things will make your assumption (I'm assuming now) incorrect. A 200 shot of progressive nitrous between 3000 and 4500 rpm's to spool the turbo's and gearing (all six gears have been modified as well as syncro's and oil cooler added) that puts KA in the sweet spot of second gear at 60 mph and in it's power range of third (about 5000 rpm's) at 130. I guess this is the package part you may have been refering to.

So you will get your 60-130 time around July, let's return this thread to Ken.

 

CJV, gearing only will make it worse as you will have to shift one time more and loose 0.5 seconds or so unless you are on sequential. A GT750 EVO just timed it at 7.2 seconds on another board, close to Bill S. car with 200 more claimed hp and that is not a track. You are right in what you are saying about performance of the old cars, but engineering at Porsche Motorsport or their suppliers at the time must have been at least, as good as the tuners you are mentioning. What really changed is software development.
Those headers look fabulous, but I doubt they perform any better than Imagineauto's, in a way that any non pro-racer would feel..

 

Jean.

I guess I didn't explain myself well enough. KA sees 78 mph at redline in first. First and second were stretched. KA uses a 3.16-1 first gear. The CGT uses a 3.19-1. It's been awhile, but I believe the stock turbo uses 3.86-1 and redlines at approx. 38 mph. They are very similar, yet KA's is a tad taller and she has a higher redline. You are correct, we are shifting less. In addition with a three disc. clutch rated for 1200 ft/pounds of torque, not many ponies get away.

As for the headers, in the lower rpm's ............. about six hp without coating/wrapping when tuned. Above 6500 to 10,000 rpm's there is a very large pick up in power with the headers. KA's old motor use to make maximum hp at 7500 with those headers. The cam and breathing was the limitation factor.

I believe Steven would be the first one to admit, his headers were not designed for the likes of KA's motor. As a side, when we tested the 1-5/8" tube headers, they actually had a little better torque/hp in the 4,400 rpm range, however the smaller diameter gives up too much after 5200 rpm's.