Wow, sorry for the delay folks, but I've been very very busy with other things like school and work, as well as a blown transmission in the car that is getting the forced induction.
That said, I am doing what I can to get back on this project, so please hold on a little longer, and all of you may be pleasently surprised.
Keep me posted on how the project is going, I just bought a 91 4.9 Seville and was thinking the same, I'd like to see your results!
I have been wondering myself. I keep accumulating 4T60E/4T65E trans info, you'll need it for a turbo for sure.... Did you get the LSD in the 4T60E yet? I wanna see a front wheel burn out with both tires..... In a Cadillac!
dang this thread started in 05..... I am also thinking of turbocharging my 4.9L. If you mount the turbo on the front exhaust manifold then it could get air cooled right because the fans are right in front of it am I right or wrong? Although a intercooler would be good.
I must reiterate what I said much earlier in the thread. The idea isn't to make it a highly refined turbo 4.9L. The stock block/rotatingassy/pistons can't handle it. You will blow it apart. The only way it will survive with this high compression without changing it is to make it a POORLY matched turbo/engine. This isn't optional unless you are tearing down the engine and beefing the snot out of it. You are dealing with a weak crank, cast pistons, non o-ringed head gaskets, aluminum block, no knock sensor, no PCM management, etc.
So with the high compression, a larger than it should be turbo is needed. You need to let the engine make the cyl pressure at low rpms, and let the turbo make up for weak camshaft at higher rpms. You NEVER ever want to overrev it, you never want to get more than 6 or so PSI boost with a stock cast piston. Heck, the LT1 shatters pistons with the pistons it has over 6 psi.
So, ensure you are NOT well matched. You do NOT want boost early, you want it later. Remember that Illumina has this planned in stages. Stage 1 is like this, Stage 2, however, it gonna be fun!!! Then we can match it all up well and make it a killer engine. IF the block and heads can take it.....
How did this project turn out? I'd like to put a turbo on my '92 Seville, but based on what you laid out, it would be way beyond my expertise right now.
I read this thread as well I think you guys are over complicating it. This isn't 1985 people are putting turbos on everything imaginable. I guess your main obstacle is probably budget. I would look seriously at running a rear mount turbo. There is room to run a 2" charge tube back up alongside the exhaust and into the TB. On my 92 there is plenty of room for an underhood turbo where the airbox is, but bringing in the exhaust from both banks and then having room to run the turbo exhaust back out would be very problematic. I just don't see a lot of other paths to get a 2.5" pipe out of there. Even if you built your own manifolds which would be overkill for this application that wouldn't help. The rear mount turbo solves a lot of packaging and heat problems and since hte point (at least for me) would be to maintain the cadillac off idle torque and use the turbo to beef up the midrange and top end any increased lag is not an issue. Rear mounts are being used in all sorts of applications and while lag is slightly larger than a front mount its not a huge issue. Lag has never been a big issue on V8 turbo apps anyway.
With the CAd ecu tied into so many functions and it works so well with all its diagnostics, my plan would be to use a Megasquirt to run 2 extra injectors in the inlet tube before the throttle body. They also sell other standalone injector drivers, but you will need to interrupt and change the timing as well and the MS can do that as well, and give you some datalogging. Connect a wide band to it and you should be able to put a good tune on it.
Anyway, just rambling, I"m not gonna turbo my CAdillac because the whole point of it is to be a no hassle daily driver. I keep telling myself, hot rod your hot rod, and leave the Cadillac alone !
You're overcomplicating things yourself, seeing as how the stock injectors will support 300whp with a turbo. This has been proven by the guys with turbo 4.9's running 300whp with stock injectors.
Illumina doesn't come around here much anymore but the turbo Seville project is still being worked on as far as I know.
You will need larger injectors.
Reason: Under boost the injectors see boost pressure, so if you have stock 18 lb/hr injectors @ 43.5 psi, and you boost 6 psi, you have 16.7 lb/hr flow under boost. So you need to do a boost a pump deal or put in fatter injectors. But you will need to get 80 psi on the injectors to overcome the boost referenced reduction in fuel flow. 80. That is like 6 bar! Going up 1 bar is ok, but 3 bar? That is too much for stock parts and FPR.
So you WILL need fat injectors, at LEAST LT1 injectors to handle it. BUT you enter in new problems, you can't adjust the fuel injector constant on the 4.5L/4.9L PEFI ECM's (maybe Ed Wright has hacked it, or call Lyndon Wester). I haven't had time to mess with hacking it as I don't have a 4.9L car anymore (I do take donations!), so I can't hack away at it.
There is a lot of issues. Fuel is a dangerous one. Adding a MSII might end up being the best. My idea of a single extra injector in the airflow. Like add a injector TBI unit to the intake in place of the stock TB, and trigger it only in boosted conditions. You can add as much fuel as you could ever need. I personally would inject E85 in, but that is me...
Going boosted takes some serious thought. ANY amount of boost is a big boon to power. Even 2 psi is significant. Think of it this way, at BEST you can suck 1 BAR air into the engine, honestly a zillion factors here. But at even 2 psi boost, you are 1.1-1.2 bar, and at a lower rpm. So you are seeing your 300 cubic inches fully utilized at a much lower rpm (you don't see all inches used at anything less than WOT, if throttled, you are at less than fully used displacement...)
Can you turbo stock injectors? Yes, but I wouldn't without additional fuel delivery.
So I guess the guy with the turbo 4.9 Fiero who told me he was running stock injectors told me wrong? His motor, as of the last time I spoke with him, had made over 300 1/4 mile passes (and was making over 300whp and close to if not more than 400ft/lbs) and never had a problem with the motor.
He might be, but there is likely something he isn't telling you too. Either extra fuel adder somewhere or he isn't making the power he claims. Honestly, 300 hp on the rear wheels? That is a low 13 sec car. Or better. I would expect better than that. If not, he isn't making the power he claims. Have him stick a WB O2 on and make a quarter mile run and show you. Either he is running lean as heck, he isn't making near the power he claims (how much boost?), or he is running something extra like methanol injection to keep things sane.
My 301 Turbo pushed my 4030 lb Trans AM to email@example.com mph and that was a calculated 290 rwhp. Now put that in a lighter car, with more cam, a better turbo design (mine was awful), much better gearing, etc. That car should be darn close to 12's.
And you have to REALLY watch boost on stock hypereutectic pistons. They will crack. And what happens then sucks.... I melted #7 down on my 301 Turbo. And that was a well factory modified Q-Jet, 800 CFM, super rich "DX" rods and I STILL leaned out and lunched a piston.
I'm still around too if anyone cares?
altough it seems to be very difficult, it would be nice to have a turbo xD
I still am pondering turbo/E85ing my LT1..... $$....