I believe it is now accepted that the 850 gets it's highest hp gains when piping is 3" downpipe and 2.5" cat-back.

First of all, I just can't make this make sense to me. Shouldn't the 3" throughout produce the highest gains? If not, why?

What exhaust systems are you running (i.e. cat-back, full, manifold etc.)? And where did you guys get your exhausts? How do you like them? How was installation? Fit and finish? Customer Service? If applicable, resistance to corrosion? Performance increase? Other mods coupled to to your car (i.e. chipping, air intake etc.)?

So far, the ATR 2.5" downpipe with a 2.5" cat back seems the easiest to buy and install. However, I'm looking for the 3" downpipe and 2.5" catback. What is the piping for the SuperSprint? SS's site is pretty low when it comes to specifics and ordering.

Thanks for the help guys.

> I believe it is now accepted that the 850 gets it's highest hp gains

> when piping is 3" downpipe and 2.5" cat-back.

I think it's only accepted for those who wanted to believe in it. All the excuses I've heard do not make sense either. Maybe one of these days, someone would be kind enough to swap out with SuperSprint's 2.5" system to do a dyno...then we'll see.

Actually Kai it is possible due to venturi affect. This used to be important with carbs on older cars and actually has the same affect on the the exhaust.

The physic say it is possible but you are going to have to find someone a lot smarter than I to explain it!

As to whether or not that is the case here with these systems, we'll have to wait on the dyno runs.

John

Hmm..interesting. Yeah, we would have to see on the dyno machine. Wouldn't be surprised if that theory is valid, though.

I couldn't copy the link but look at this:

www.ferrita.com

click on the Swedish version

then click on the "produktinfo" link.

The text is is Swedish but the graph of a dyno run shows that the highest HP rating was achieved with configuration #4 which was a 3" cat and 2.5" cat back exhaust system.

The dyno run was on a '94 850 turbo with a SAM chip and different exhaust configuration.

Hope this "factual" data helps you.

Michael Svärd

'95 850 Turbo w/ K&N, chip, 3"downpipe, 4" race cat, 2.5" cat back, +more.

Nope, still not 'factual' enough..i can't even read it. Why don't you do some translation here, please? So, they have done a dyno on a same car with full 3" compared to the same car with just 3" inch downpipe, but 2.5" for the rest of the car?

So...what we should do to achieve the most out of our turbocharged cars is to have 3" downpipe then hopefully an even larger diameter cat, then give it a bottle-neck like 2.5" catback??

Still don't get the science here, maybe I've just never heard of this new way to achieve the highest power for turbocharged vehicles. Like I said, maybe one of these days I ought to give this a try compare to full 3". Then that will be enough "factual" for me.

>So, they have done a dyno on a same

> car with full 3" compared to the same car with just 3" inch

> downpipe, but 2.5" for the rest of the car?

yep, looks like you figured it out enough to understand that.

>3" downpipe then hopefully an even larger

> diameter cat, then give it a bottle-neck like 2.5" catback??

The cat on my car is 4" external dimater, 3" internal so it is the same diamter as the downpipe not larger as you are implying.

Based on the dyno run data a full 3" system is not a bad choice, however the 3" downpipe to 2.5" cat back showed a higher HP gain at higher rpms.

My nonscientific guess would be that some restrictive backpreasure may be needed in our application.

>I ought to give this a try compare to full 3". Then that will be >enough "factual" for me.

Go ahead. Maybe then you would be willing to share your dyno runs with the rest of the board. This board is still about sharing isn't it?

-Michael

> yep, looks like you figured it out enough to understand that.

Nope, I just assumed so.

> The cat on my car is 4" external dimater, 3" internal so it

> is the same diamter as the downpipe not larger as you are implying.

Then maybe you should just call it 3" cat to avoid confusion.

> My nonscientific guess would be that some restrictive backpreasure

> may be needed in our application.

Yeah, that's what my guess is. Hopefully I will get a chance to try that out with the SS catback....if anyone is kind enough to lend me one.

> Go ahead. Maybe then you would be willing to share your dyno runs

> with the rest of the board. This board is still about sharing isn't

> it?

Yeah, I actually share with many people,if not all, off the Board..only to those who dares to believe the truth. Not that I don't want to share, just found more less narrowminded friends off the Board.

I can try and translate the Ferrita page when I have time if you are truely intrested.

>Hopefully I will get a chance to try

> that out with the SS catback....if anyone is kind enough to lend me

> one.

So would you try and dyno it if you had the chance?

> Yeah, I actually share with many people,if not all, off the

> Board..only to those who dares to believe the truth. Not that I don't

> want to share, just found more less narrowminded friends off the

> Board.

I'm not sure if your implying that I'm narrowminded but when I bought my exhaust system I went in looking for (noncustom, I didn't want the fitment hassle) a complete 3" system. SuperSprint only has 2.5". BSR had a in house system in 3" which wasn't finished. ATR has 2.5", Ferrita had the 3" to 2.5" which was recommended by SCT and SAM. IPD had stopped selling its downpipe which only goes upto the cat.

I used the data which was available at the time which is the link I suggested earlier as well as SCT recommendation who had used the 3" to 2.5" as well as a 3" complete in there test applications.

I also liked the fact that the Ferrita downpipe included a race cat. It was one 3" piece all the way to the middle of the car. Unlike that of IPD's which needed welding to the existing stock cat.

I would be intrested in seeing any dyno data for your car that you may be willing to share with me regarding your mods. I would consider that data in any further advancements in my car.

Thanks, Michael

> So would you try and dyno it if you had the chance?

Yeah..it's just kinda hard to ask Pete at CFI to barrow his C70 SS kit. I doubt any vendor would do that for you. $700 something is just a bit hard to swallow....

> I'm not sure if your implying that I'm narrowminded..

Nope, just some other people.

I'm seriously considering the SS kit...it comes down the cost factor again. If SuperSprint themselves would like to prove your theory and promote their products, I'm sure they would try to contact me to let me try out their unit at cost~ LOL!

I believe SS would give me the least noise v.s what I have now. The rice can is only for the riceboys to admire and in some catching negative attentions, I really think the SS would be the best choice for European cars.

However, I don't want to pay the b.s European premium for few pipe and muffler. If you don't count the cat and downpipe, I only paid less than $450 for the catback and installation.

I'm getting better mileage and higher performance with 3 inches all the way back through the dual cat-back custom exhaust I recently installed. 3 inch ID cat, 3 inch ID resonator mounted just behind the cat, and 3 inch turbo mufflers, just like the Mustang GT across the street from me. And... It even passes Smog when I swap out the chip.

Regards,

Mike Harris in Sandy Eggo

Bigger does not always mean better!