43 replies to this topic

[Che'_Moderator]

Haven't people said the speedtuning chips run rich to begin with?  If this is the case, wouldn't a higher flow exhaust help?  I'm no expert on engine mapping here so correct me if i'm wrong.

No would make it worse.

[saturn by day volvo by night]

Actually it should make it a bit leaner, though in effect its not enough of a change to really overcome the backpressure created by the small TD04 exhaust side.

So I must say I am very confused by this post. I have never seen so many different opions on this subject. I am going tonight to my friends muffler shop to have my turbo to tip exhaust made. I was planning to have him make some extra kits,to see if anyone is interested. my car is a 94 850turbo. I was going with a 3" down pipe 3" flexpipe,3" hi flow cat,3" magnaflow.and full 3" madrel bent aluminumized pipe for around $600.00. is this the best way to go if I plan to stay with my 15g and getting a chip,or reprogam,or what ever you want to call it.

[GShyneDM]

Actually it should make it a bit leaner, though in effect its not enough of a change to really overcome the backpressure created by the small TD04 exhaust side.

Which turbo are you referring to 15g? 16T? (or are they the same connection on that side??)

I find it pretty interesting that maybe a 3" down pipe isnt going to net us any gains (maybe just a change to a race cat and free flowing 2.5 exhaust is enough) *getting revised ideas*

Edited by GShyneDM, 03 May 2005 - 10:09 PM.

[Plan_B]

I am confused too!

I have a stock turbo, and I had the IPD exhaust installed and have a 17 psi chip, I do want to upgrade my downpipe, is tha 3' the way to go?..like the one that Mike or Jesse are selling?

[Bay13]

Ok to unconfuse everyone, go back and cut and paste everything Volvospeed has said in this thread, then sit back and ask your self do you want a 12second car or not. Don't think that by changing what he has said you will end up with an 11 second car.

[Che'_Moderator]

Actually it should make it a bit leaner, though in effect its not enough of a change to really overcome the backpressure created by the small TD04 exhaust side.

Doug your basing it on just massflow rate. With a larger pipe you change the volumetric flowrate. With a larger pipe the O2 sees lower emmision and will richen the trim to bring up what it think is a lean enviroment. Again none of this matters in open loop.

[mAydAy]

Run 3". If I could, I'd run a 90* 4" bend and pipe it straight up through the hood with a rain flap on top. If you get boost creep, tighten the wastegate rod and port the exhaust housing (Worked for me, now I hold 18psi steady as a rock except the spike to 20 between shifts)

-Andy

[Plan_B]

well just get a 3inch down pipe and exhaust. Then worry about a remap when you do a larger turbo. i guess i could benefit from a remap of my ST chip becuase i have a full 3 inch exhaust and down pipe, but im upgrading the turbo so its prolly a waste of money and time to do so.

So why would you hav eto have the chip remaped if you have a stock turbo and a 3' down pipe and a chip upgrade?

[Che'_Moderator]

So why would you hav eto have the chip remaped if you have a stock turbo and a 3' down pipe and a chip upgrade?

Re-read my post about volumemetric flowrates

[thelostartof]

i think what doug means by small TD04 is the fact that even tho the laters have a larger outlet they are still 6cm2 housings which is a .49 a/r abouts .. so where its great for spool up and an auto car for a stick you do want a mucho larger housing

[GShyneDM]

Doug your basing it on just massflow rate.  With a larger pipe you change the volumetric flowrate.  With a larger pipe the O2 sees lower emmision and will richen the trim to bring up what it think is a lean enviroment.  Again none of this matters in open loop.

So...should we even touch the cat/catback...cuz that would result in better flow too (just after the front 02 sensor)

[Che'_Moderator]

I never thought about it that way Chuck. Good point. Im used to tunning cars in open loop, the larger exhaust an improvement in VE did lean the mix out some. But metering less air in closed loop makes sense. Maybe the best fix would be the move the first o2 to the top of the DP where it is still semi "narrow".

I know o2s want to be 300+ degree to operate but I dont think they way 1300 degrees.... Dunno, maybe they do

[JHEIII874T5M]

I say stock downpipe no cat-no muffler is fine for 13's

[thelostartof]

I know o2s want to be 300+ degree to operate but I dont think they way 1300 degrees....  Dunno, maybe they do

you talking about all 02's or just 850 02's?? as the old 240 turbos have the 02 right in the exhaust manifold right before the turbo.

even the stock rwd turbo cars and most all now have them them about 2-3 inches behind the outlet of the turbo so they do get and stay pretty hot

[RAzOR]

real quick q...
for 850turbo w/stock 15g @17psi,...would 2.5" racecat and muffler be better off or worse than 3" full exhaust system??
dont you need backpressure and whatnot,..like will the 3" cause the turbo to take more time to spool up vs 2.5"
just checking again before i hook the shizzle up on my car one way or the other.
any thoughts, opinions, and reviews would be greatly appreciated...
g

My advice:

If cabin noise is a concern, to me there is only one option, the TME setup. It's the only one I've found that is still pretty quiet. It is defintely tuned.

And at 17 psi, I can't imagine going from 2.5" to 3" with straight thru mufflers is going to make much difference at all.

That's my worthless advice.

[thelostartof]

And at 17 psi, I can't imagine going from 2.5" to 3" with straight thru mufflers is going to make much difference at all.

you'd be surprised, a little more exhaust flow can pick up all kinds of power on top end


and yes doug i'm right ... in the manifold ..just because your 240 was so far from stock you don't even remember


darn i guess i should read up on how these 850's work maybe i can figure out something on them ...

Edited by thelostartof, 04 May 2005 - 05:29 PM.