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Originally Posted by N0DIH Funny you should mention it, I was actually looking at the title to the thread last night, thinking, we are not posting at all about Stage 1! But the bunny trails were cruising on and on....
You are right, the MSD BTM and 4-6 psi boost to start (keep boost low initially) with a simple mechanical wastegate, unless we have $$ to get an electronic one and make a knob inside the car (which would be nice to help save the engine if boost is suddenly too high, maybe make an ESC module control the wastegate instead of the timing control) A way to monitor pinging should be seriously considered. GM put knock sensors (ESC) on 3.8L's, Turbo 301's, and various other cars. Look for G Bodies with V6's and the ESC module is on the pass side fender. Snag a few of them. Get some various knock sensors, 4.6L N*, 2.8L Chevy (if they have), 3800, 3.8L, 3300, 1.8L Turbo 4, 2.0L Turbo 4, etc. You may need to experiement with the one that is most sensitive. Install them one in each block coolant drain. Closer to the cyls is best. Becareful removing those drains! It is an aluminum block, so it might not come out easily.
Plan out where the turbo can do, how to get exhaust to it and away from it (likely on top of the trans, that is where Pontiac put it on the 1988 SSE Turbo Bonneville prototype), obviously the air box is removed, build an abundance of heat shields you WILL need them, a little goes a long way on a heat shield. You can drop temps 50 degrees with 1/2" air between the source and the thing you are protecting.
Calculate the boosted airflow requirements. If the turbo is at 14.7 psi, you are double the CID. Make sure the TBI unit will flow enough air for you, at 7.5 psi you are ballpark 450 cid. You may need a 454 unit, stock maybe, maybe a little porting. You don't want it to be a boost restriction and having it backing up the intake tract. I need to look at the allante intake more (is that Stage 1 or 2?). Make sure there is some plenum under the TBI. Being the 4.9L isn't a high revver, the 454 TBI is probably sufficient, for stage 1....
I am wondering if the MS is best saved for Stage 2 and use my idea to trigger extra fuel for stage 1. Simple, cheap, and very effective.
Does anyone know if the Cadillac PCM will handle a 3 bar MAP? And has anyone broke the programming on it? Does anyone have any friends at GM in handware or software engineering that might be willing to answer silly questions like that?
You should not need anything special on wastegate with that low boost. Like an extra exhaust pipe, etc.
When I was pondering turboing my 3800, I was looking at bringing up the exhaust to the turbo right off the factory crossover, and then return it back to the cat converter in the stock pipe with an extention. Just weld off that nasty back side crossover on the 3800. (Thrasher Engineering makes a replacment that isn't so bad, for you guys with a 3800) Odd thing, the 3800 has a 2.3" crossover pipe, the 4.9L is smaller, like a 2" or 1.75". Maybe you can adapt the 3800's pipe.
Oil supply, oil pressure sending units with a T work, but not always sufficent flow. The closer you get to the oilpump the better. If you can up oil pressure, DO SO! Oil drain back. Drain must be lower than turbo exit. The intake may work, you might need to drill a hole in the backside of the intake to drain into the lifter valley.
Being we already have an engine oil cooler, that is good. Either monitor oil temps or go synthetic. Even with me changing oil very often, the oil didn't survive enough to save my rod bearings. So it is low cost bearing insurance. 15W40 may be sufficient though.
Turbos LOVE cooling engines and cold air induction. A cold day will give you a ton more power than a warm day.
Insulate the exhaust pipes going up to the turbo. Spools faster and reduces underhood heat. But, non stainless pipes may not live as long. |