Hi:

The the subject says I am looking to purchase a downpipe, of if drawings to fabricate my own.

I believe i read someone on here fabricated up a divorced pipe at some point, and that information would be great.

I can get the fabrication done, but I would really like to know what to make up not just guess at it.

iceman_ca wrote:Hi:

The the subject says I am looking to purchase a downpipe, of if drawings to fabricate my own.

I believe i read someone on here fabricated up a divorced pipe at some point, and that information would be great.

I can get the fabrication done, but I would really like to know what to make up not just guess at it.

further information will improve your chances of relevant information. The year and model of your car along with the engine setup you have and any modifications will help.

They are very easy to build yourself. Even easier if you can re-locate the battery to under the rear seat or into the trunk (you have more space).

If your car has the Garret T3 turbo you can find flanges online and just buy a few pieces of pre-bent tubing. If you have the later Mitsu TE-05 you may have to make or have made a flange, they are a little trickier to find.

Brad Shaffner at Kansas City Saab I believe made some divorced wastegate downpipes, as did Dave Kennedy at the now out-of-business Group9. Both were quite expensive.

Here is a photo of the divided down pipe that came from Brad Schaffner for a classic 900 turbo.
Is this what you are looking for?


http://www.nysocphotos.com/Jon-Williams-Garage/1991-900-Turbo-Convertible/5644621_fStkqh#!i=347151840&k=rj4QSGv

Sorry I didnt mention it is for 1993 900T. My plans include T5ing it, installing a FMIC, and installing a down pipe. I am a noob at this but I think it is the Mistu turbo on the car right now...the car is in storage for the winter so not easy to check.

Presently I have two complete engines, trannies and turbos to work with, MY 89 and 93. That would mean i have a Garret and a mistu Turbo available, correct?. Additionally i picked up the the Turbo from the 1996 900se, which I scrounged the T5 parts off of. So I have a t25 as well, I believe.

I planned on relocating the battery when I do the T5, FMIC, and downpipe conversions, either to the trunk or the opposite side of the engine bay. In all likelihood to the trunk. I have an optima battery which can be fitted sideways below the false floor area

The photo of the pipe is what i was thinking of. If the cost for the fabbed up pipe is prohibitive, what radius would you recommend for the new pipe. Is this why so people go from 3 to 4" then back to 3" to allow for a greater radius with stock mandrel elbows? If so what effect does this have on the exhaust gas flow velocities.

Thanks for your help and patience

iceman_ca wrote:Sorry I didnt mention it is for 1993 900T. My plans include T5ing it, installing a FMIC, and installing a down pipe. I am a noob at this but I think it is the Mistu turbo on the car right now...the car is in storage for the winter so not easy to check.

Presently I have two complete engines, trannies and turbos to work with, MY 89 and 93. That would mean i have a Garret and a mistu Turbo available, correct?. Additionally i picked up the the Turbo from the 1996 900se, which I scrounged the T5 parts off of. So I have a t25 as well, I believe.

I planned on relocating the battery when I do the T5, FMIC, and downpipe conversions, either to the trunk or the opposite side of the engine bay. In all likelihood to the trunk. I have an optima battery which can be fitted sideways below the false floor area

The photo of the pipe is what i was thinking of. If the cost for the fabbed up pipe is prohibitive, what radius would you recommend for the new pipe. Is this why so people go from 3 to 4" then back to 3" to allow for a greater radius with stock mandrel elbows? If so what effect does this have on the exhaust gas flow velocities.

Thanks for your help and patience

For the '89 if it is the original turbo or replaced with the correct one it will be a Garrett T3.
Here is a version of downpipe with an external wastegate that would fit.



I would say it is a 3" or 3.5" CLR bend. The elbow coming off the turbo is key. The smoother the bend the less turbo lag you will have.

DrewP wrote:They are very easy to build yourself. Even easier if you can re-locate the battery to under the rear seat or into the trunk (you have more space).

Drew you are correct, it is easy if you know how or get some tips to work with tubes getting the fit up correct. The fit up makes all the difference when you go to weld it.
Be sure to make your cuts from the centerline of the tube bend. If you do not cut and belt sand perpendicular you will create an ellipse and that will not mate with the straight section or other bent section that will be a perfect circle.
We made this simple tool to keep you honest. Sharpie pen where the string lays.


Another option is a smaller battery in the stock location.

That is a shit load of speed holes.

Very nice work, thanks for your help

DrewP wrote:That is a shit load of speed holes.

Those make the sheet metal stiff as frozen dog shit.

How about the 3" downpipe for sale on Genuine Saab? Anyone tried this one out? Too bad it doesn't have a connection for a cat.

http://www.genuinesaab.com/catalog/inde ... rers_id=26

I've heard that the 3" downpipe itself provides the greatest improvement and that you don't need more than a 2.5" for the cat back. Is that true?

That's basically true. 3" all the way back won't hurt, but I think Nick has dyno sheets on Genuine Saab somewhere of a Viggen with tube headers and a TD-04 18T with a stock cat-back that made ~300whp.

Suppose I could go with an aftermarket 3" cat or reduce just before the cat. We need the cat up here. only 88 and below are exemption from e- testing. Starting next year it will be a 2000 rpm no load test though. Right now the drive wheels are loaded during the test