What is the purpose of routing the rear exhaust over the tranny to the front? Isn't there more performance to be gained by having true dual pipes with two cats? Thanks.

I don't know how it affects performance (should be less restriction wastes less horse power) but I can tell you it changes the sound of the exhaust. I love the sound of true duals out my 3500.

[This message has been edited by LZeppelin513 (edited 12-03-2011).]

Yes. But you will be limited by stock intake breathing before your dual exhaust make a difference

From a Former West Coast Fiero Employee talking about John Parenti's Mean Green Machine (3800na):

"I know for a fact is uses a Crower Cam that John put in, no idea on specs - hell, the last time I rode in the car was something like June of '97 for the Knott's Berry farn show, picked up the car down at Fiero Motorsports which has been gone for years. Knowing John, it more than likely has headwork, port matching, etc... I do know that at one time ( possibly still does ) had true dual exhaust with no crossover, sounded like a Geo Metro on crack and I believe that we successfuly talked him into changing it.
But just by seeing the pics you can see that the mod work to the engine bay, that is nothing in comparison to the sound system....

------------------
Former West Coast Fiero Employee"

I was recently told that running true dual exhaust will lower torque. I don't know any of the details but that was what I was told.

quote Originally posted by LZeppelin513: I don't know how it affects performance (should be less restriction wastes less horse power) but I can tell you it changes the sound of the exhaust. I love the sound of true duals out my 3500.

Can you post an audio clip?

quote Originally posted by Amida: Can you post an audio clip?

yes please, im bout to run exhausy on my 3500....

Any engine requires just so much breathing. More exhaust than you need will alter the torque curve and possibly cause a loss of power. Last month I wrote a post that had a link to sizing the exhaust. There was some good info there and I'll try to find the link. In summation bigger is not always better. Matching and tuning an exhaust is the better route to power.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, ZZP Intercooler, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

The best exhaust on a v6 sequential timed engine is 3x3. The scientific testing that was done shows primary pipes, 22" to 34" at 1.5" diameter, with no Y or crossover is the best for torque, showing more low end torque the longer the primary pipe.

The volume needed for the collector, being 15X the swept area of a cylinder is so huge, you could litterally run straight pipes.

A Y in a V6 is just not as good.

When I went to true duals, properly done with mandrel bends and measured, my low end torque went up.

I haven't had it to the dyno since, due to conflicting time crunches, but I intend to in the coming year. I can safely say that true duals, if done right, are superior in every way. My engine pulls strong right through the red line and higher than I'm willing to take it, and the sound is great.

Arn

I have a 3800scII just sitting on a cradle. Would this engine benefit much from headers and a dual cat system?

A supercharged engine produces more air. It can benefit greatly from headers, unlike the turbo's which don't seem to benefit much due to the turbo housing/waste gate setup.

Essentially the scavenging effect will enhance the supercharger.

Arn

quote Originally posted by phonedawgz: Yes. But you will be limited by stock intake breathing before your dual exhaust make a difference

Good point. Perhaps if the the 2.8/3.1 had the TLG dual throttle bodies, then maybe a dual exhaust would make a difference.

quote Originally posted by Amida: What is the purpose of routing the rear exhaust over the tranny to the front? Isn't there more performance to be gained by having true dual pipes with two cats? Thanks.

In the OEM application, it was done to increase exhaust system length to reduce volume levels and to make room for a cat.

With the 60 degree V6 family having equal timing of exhaust pulses on each individual bank, there isn't much if any benefit to merging the two banks. On the 90 degree V8's there is uneven firing pulses on each side, and when 2 cylinders fire back to back on that side, the exhaust is effectively smaller for that portion of the firing sequence on that bank (and too big on the other bank). So combining the two banks (via H, X, 180 headers, or large single exhaust setup) usually improves torque.

But the 60 degree V6 doesn't have the exhaust issues of a 90 degree V8 and will not result in the same benefit/hindrance the 90 degree V8 does.

quote Originally posted by Amida: What is the purpose of routing the rear exhaust over the tranny to the front?

There were probably three reasons:

1) To get a single pick-off point for a single O₂ sensor.

2) To allow the use of a single catalytic converter.

3) Because the front of the engine is where the most space was available for the cat.

quote Originally posted by Arns85GT: ... true duals, if done right, are superior ...

True. And the key is the "done right" part. To pick just one design item of many, when choosing the diameter of the primaries bigger is not always better.

to have some one form & install a dual exhaust is expensive,,for the average owner you will get the best benefit from the Truelo exhaust header ,,I practically wet my thrift shop jeans in anticipation of duals ,so cool ,but went with the truelo system backed up by a turbo muffler because of dyno reports on Performance ,& price ,I wanted better MPG ,most want the Truelo system because of the significent power increase ,, I seek increassed efficientcy with the same zeal i pursuit a wealthy mature attractive lonely
widow

Both systems are a pain in the toe to mount ,, 3 of the bolts on the front truelo are very difficult to install (REALLY) I recomend you tie the bolt in the hole with thread,you have to drop the black coolant pipe that runs along the front side,before install .
I do shutter in subservient anticipation of the truelo with a pipe leading from each header INTO A DOMINANT SOUNDING BORLA ,PUNISHING ECSTASY!!..
iM CHEAP ,WILL NOT SPEND THE TIME OF DAY, SO PURCHASE OF TRUELO HEADER WAS COBWEBS OFF THE WALLET time,but am now dating wealthy window,life is better,sunnier,more parts comming..

Not going to comment on the power gain/loss of true duals as either could net great results if properly tuned (as previously stated by others) but here is my contribution to this thread

3800sc
cheap ebay headers, no trunk modification
true dual exhaust
two long skinny straight through mufflers that look like glass packs but they are chambered like a turbo muffler



-Joe

quote Originally posted by joesfiero: Not going to comment on the power gain/loss of true duals as either could net great results if properly tuned (as previously stated by others) but here is my contribution to this thread 3800sc cheap ebay headers, no trunk modification true dual exhaust two long skinny straight through mufflers that look like glass packs but they are chambered like a turbo muffler -Joe

Woa...that sound pretty good to me...kinda lopey like it has a large cam. Do you have any more vids with reving?

[This message has been edited by Amida (edited 12-04-2011).]