exhaust housing options...

[Darth Fiero]

OK, here is what I have done and what I am working with:

97 3800 Series II SC L67 shortblock -- stock
97 3800 Series II NA L36 heads -- ported, 3 angle, backcut
98 3800 Series II NA Camaro Intake and TB -- stock
87 GN Turbo -- stock, ported exhaust housing, adj wastegate
2.5" Mandrel bent exhaust pipe feeding single Holley Terminator muffler
91 Dodge Spirit R/T "T3" Intercooler w/ elec fan, 2.5" induction plumbing

As I stated before, the exhaust housing has been ported. However, in looking at this thing, I have come to the determination that it is a poor design in which gases exiting the turbine crash into the outer wall of the housing and then are forced downward into the downpipe when the pressure builds. Now I have seen the DIY 3" downpipe mod that can be done to the stock exhaust housing by cutting and welding, but consider this alternative. How about we keep the housing like it is and weld in a section of mandrel bent pipe that will smoothly direct the escaping gases into the downpipe. What do you think? Worth the time in doing this vs. leaving it as it is? Ultimately, I would like to acquire the first foot of a THDP including the wastegate and flange because I cannot use the engine DP because of my "unique" application. The problem is I don't want to buy an entire DP just to butcher it. I also cannot seem to find anyone who wants to sell a good or damaged on cheap. The third problem is I can't seem to find any contact info as to who actually makes the THDP to see if I can call and get a blemished one at a discounted price. Any help here?

 

[WSLN 6]

I am still running the stock elbow, so I doubt you will see a lot of gain using the stock GN turbo.
JMO.........

 

[Darth Fiero]

So what you are suggesting is that if I am using a stock TR turbo, then I can expect 0 gain from upgrading to a 3" THDP? I am only using 2.5" tubing on the exhaust right now as I see little point in making the pipe bigger because the stock DP is only 2.25" at the flange. Perhaps my understanding of exhaust systems pertaining to the performance issue is not satisfactory enough...

...I was under the presumption that a stock intercooled TR could benefit by nearly .5 sec in the 1/4 mile from just the addition of a THDP. Please explain.

 

[WSLN 6]

I'm sure there will be some gain, but there is cheaper horsepower out there.
It seems that every car has had different gains from the THDP. Some high 11 sec cars have only gained 1.5mph in the quarter, so .5 sec is quite high.
The stock elbow can be ported out to a maximum of 2.75 at the flange opening while still being able to run a small gasket to seal it to the downpipe.
I agree the elbow is of poor design, and if funds would allow I would probably have a THDP under the hood, but the most performance gain would come from alcohol injection at your stage in the game.

 

[YGETV8]

Hey Darth,

I live in Davenport and would love to see that thing you're building!

A ported stock elbow is a good complement to the stock turbo as the biggest restriction is the cast in lip you see right above the leaded gasket to the DP. A slightly larger than stock replacement DP will help, too. A THDP and/or Mease Performance (same basic design) can be had in a short "starter" section, I believe, for guys just like you who have to customize it anyway. Yes, they will help, but not nearly as much on a stock turbo car.

If it were me, I'd do the THDP/Mease DP from the start as you'll just want to upgrade at a later date anyway!

Check measeperformance.com for availability.

 

[Darth Fiero]

Originally posted by YGETV8
Hey Darth,

I live in Davenport and would love to see that thing you're building!

Absolutely; I live on the very NW corner of Davenport, about 2 miles south of I-80 in a subdivision off Northwest Blvd. PM me for specific contact information.

A ported stock elbow is a good complement to the stock turbo as the biggest restriction is the cast in lip you see right above the leaded gasket to the DP. A slightly larger than stock replacement DP will help, too. A THDP and/or Mease Performance (same basic design) can be had in a short "starter" section, I believe, for guys just like you who have to customize it anyway. Yes, they will help, but not nearly as much on a stock turbo car.

If it were me, I'd do the THDP/Mease DP from the start as you'll just want to upgrade at a later date anyway!

Check measeperformance.com for availability.

I guess that is what I need to know. I figured the whole point of a THDP or equiv was to get rid of the bottleneck. The stock DP flange and pipe is approx 2.25". What does it matter how much the ex housing is ported out if u are ultimately going to be limited by the size of the pipe at the flange. Besides that, just look at that setup. A 90 degree instant bend is not good for flow to begin with.

The turbo is stock and only has 38,000 miles on it so I wanted to see what it could be pushed to. I believe my combination is unique in that I am working with a superior engine (no offense to you LC2 guys) in which the heads stand out as being the single biggest improvement to HP gains vs. the LC2 (IMO). What effect this is going to have on the efficientcy of the turbo is anyone's guess.

Basically, I was just "testing the waters" to see if there was any justification in spending money on a THDP or equiv for my combo and if it would really do me any good. I consider a .2 sec gain in the 1/4 justified if I am spending $100 or so on one particular piece. I also understand that this purchase would also pay dividens down the road should I decide to run a bigger turbo.