89951DREAMER

I am trying to decided on a complete exhaust system for my 951 and I'm having trouble. Can anyone give their input on the SFR downpipe. This is the short one that bolts directly to the turbo. If it makes a noticable difference, then I will consider buying their system. Otherwise, I'm leaning toward the Lindsey system with Edelbrock RPM muffler. My car is mostly stock. I have a slightly larger turbo (Majestic "Cheetah") and GURU chips. Thanks.

Ian

daniel951

Brett on the forum told me that it made a big difference and i think he has some dyno's after the downpipe too.

Epic2112

I was wondering the same thing. Isn't the smallest point in the exhaust the limiting factor? I mean, is there much of a point to going to a 3 inch exhaust if the downpipe is 2.5 inches? wouldn't that be like having a full 3 inch system witha section of 2.5 inch pipe welded into it somewhere in the middle? Or is there a difference because of where the downpipe is (right by the turbo)? I'm thinking about going to 3 inches, but I'm not going to bother for a while if it doesn't make sense to do it without the 3 inch downpipe, the thing's a pain in the *** to get out and I'm too lazy to do all that work right now.

Epic2112

Bump

jc22

The amount to which flow is inhibited depends on where the obstruction is located. Having a 2.5 inch downpipe won't hurt flow nearly as bad as having a 2.5 inch tip. The exhaust gasses' velocity is greatest right where it leaves the turbo. From there the gasses' velocity slows until it exits the pipe completely. From what I have read and researched, the ideal exhaust system tapers from 2.5 inches (for some length), to 3" (for some length), to 4" (for some length). This efficiently moves the gasses through the pipe. As the velocity decreases the larger pipe minimizes back pressure.

Bengt Sweden

It is actually vice versa. You need a larger diameter in the beginning where gases ar hot and have high pressure and velocity. The lower the velocity the less restriction you have and no meaning to go to bigger pipes.
Bengt

J Chen

No Bengt,
Same size with the turbine outlet first to minimize
turbulance at the exit of the turbine than go bigger
& start to reduce. Well I guess we'll have to find a
formula to calculate how long each pipe has got to
be not to mention that it's gonna be specific for
stock heads & modified heads

azmi951

I was wondering the same thing and just aquired a stock downpipe to use to make a 3" pipe. I will make a bracket that holds both of the flanges then cut the pipe section out. I will then make a new pipe section that tapers from the near 2.5 tubine outlet to a 3 inch. I also got a quote from Jet Hot to coat the pipe. It is really cheap, $25 per foot.

Providing that I build accurate brackets the pipe should bolt back up like stock.

Yes I know I could spend $250 and get the SFR piece but I get a lot of satisfaction building my own stuff and this will probably be cheaper.

shortyboy

there was an article in European Car magazine where they installed SFRs Stage 2 Headers and 3" DP and gained 30hp/30/tq to the rear wheels.

CPTdooberhead

But what else did the car have done to it? I wonder if it would be worth it on a car like mine, that has every other bolt on except SFR headers and 3" downpipe...

streckfu's

Velocity and pressure vary inversly.......

streckfu's

The were using the Kokeln stage V turbo and 3" exhaust, etc.

Dark Lightning

I'm thinking of making my own as well. If I can get a decent jig made up I might make a couple and sell a few off.

Anyone have a stock downpipe they have no use for and would like to sell?

Isn't it $399?

azmi951

Oh yeah that is why I didnt want to buy one, I think they are around $400.

I just put a post up a while ago and got one for $50. Just start a thread.

I will be in Michigan (Flint, Kettering) in a few weeks, I can bring my spare pipe and if you have the tools we could work together on building a jig. All we really need is a mig welder, and some other basic metal cutting tools. I was going to make it from U-bends.
PM me if you are interested

Crazy Eddie

azmi951
I would be interested in what you guys come up with ...
If I am not mistaken there are some slight differences in
the alignments of the exhaust pieces on the 951...
One thing I know you could certainly lighten the pipe
That is one heavy sucker !!
regards
Ed