i plan on turbocharging a 5.3L vortec truck engine with some 6.0L heads to drop the compression to ~ 8.5:1.

I was wondering what everyone thinks is the most boost i could run at this CR for the street on 93 octane gas, with computer tuning of course and an intercooler or two.

id rather not pay for a turbo kit, so when i do this it will probably be a ghetto fabulous twin turbo setup with stock manifolds filpped around and much fab work. i was thinking about twin t3/t4's. i realize that there are different versions out there with different turbine wheels, but am i wasting my time with these? as in, if i can run 17 lbs. of boost at 8.5:1 and the t3/t4's max out at 10 lbs, its a waste of time and i should get bigger turbos. whats everyone think about grand national turbos? wastegates?

any help is greaty appreciated. i dont know much about turbos, but the idea of a twin turbo LS1 variant is very appealing.

-bryan

 

I have the "i made my own twins in my apartment parking lot" kit, and with the with ls1 heads. with tuning, im at 12 psi right now with 93 octane and seeing no knock. Im going to up the boost some and see how it likes it. Im running t4 turbos with two tial 38mm wastegates.

 

my buicks compression is 8.5:1 and i ran 16 before the alky with the little stock intercooler. if you wanna run big boost alky is the key. i run 24#s with no knock on 93 gas and could probably get some more boost out of it.

 

im going to use alky too, but i need to get rid of my stock rods before i go crazy.

 

check out www.alkycontrol.com thats who made my kit. great kit and awsome customer service.

 

im planning on running twin gn turbos (T04B's) and ill probably pick up two gn intercoolers as well. so 16 lbs was as high as you would go without alky? im really wondering what is the max boost i can run on the street without needing alky or anything besides the intercoolers to help with knock. at the track is another story, but id hate to have to get out and fill up my water/methanol tank every time before i devastated a ricer. ;D

did your kit you used have a WOT switch, or is it manually controlled?

 

i might have been able to run a little more than 16 but thats about the limits with pump gas. with alky you can go to the track and make probably 25 runs and not run dry. you only use the alky to control the knock so the less alky the better. the kit i use is progressive and uses the map sensor. so you set it once and if you up the boost the controller compensates and sprays more alky.

 

I was wondering? once my trucks Running right whats the max boost I should run. I have a 2000 gmc 5.3 with the stock sts kit a nelson performance tune,the high low boost cotrol and a methanol inj kit. 373 posi

 

also...what injectors should i use? 500-600 rwhp

 

v_7, what kind of intercooling?

 

If you can get the tune perfect you MAY be able to run 16psi for a bit but I highly doybt you'll do it on pump gas and make good power. You'll likely have to drop timing way down on pump gas. Plus if you do start making max power with 16psi then there is a good possibility you'll break something on a stock motor.

Methanol is your friend when it comes to running max power on pump gas.

Also remmeber you can't compare Buick GN boost to that of a V8 that was never designed for FI. The Buick guys can run 24psi with meth injection on pump gas NP. Try that on a V8 and you'll be giving credit card #s to your engine builder in no time. LOL

 

im thinking since im going to run twin grand national turbos i can use twin grand national intercoolers. they will be front mounted in the direct path of incoming air. this is going in a second gen rx7. seems like the gn intercoolers would work better on this than they would on the gn since its displacement is 3.8L and on this each intercooler would only have to feed ~ 2.65L since this is a 5.3L engine. like two 4 cylinders...mwahahah.

 

Gn's run one 'cooler right, so why not run a Griff FMIC.

 

im definitely going to twaek and tweal until i get teh perfect tune. it will be a safe tune too (rich) and ill start with low spark advance and work it up slowly. from what ive heard, the stock internals could handle the kind of power that im wanting to make ~ 500-600 rwhp. well...at least the crank can.

ive heard over and over about methanol and it seems like a good idea.

the reason im comparing it with a gn is that im lowering the compression on my 5.3 by adding some 6.0 heads and that will drop the compression ratio down to about 8.5:1, which is exactly what the gn runs at. also, i think the gn has steel cylinder heads and i will be running aluminum so that might help lower the dynamic CR even more. also i will probably use a good head stud kit which might help keep the block/heads a little more rigid.

im more than confident that the motor can take the power unless i have detonation problems...in that case no motor is going to last and this will be the hardest part to overcome.

i have a bit of confidence in these 5.3 motors simply because of the insane amounts of nitrous that most of the truck guys are putting through them. they also supercharge them regularly and the stress from a 4500 lb truck has to be a little more extreme than my 2800 lb rx7. at least i hope so.

 

I believe the LC2 engines in GN's were/are 8:1.

 

im running twins and want to keep the plumbing as simple as possible. with twin intercoolers i can have the input tubes coming in from the outside edge, then have both output tubes meet in the middle on their way to the throttle body. with one large fmic it gets a bit more complicated and probably will restrict flow as well. not the intercooler itself just the piping.

another bonus is that the buick guys are always upgrading and like to sell their old turbos and intercoolers for dirt cheap. turbos regularly go for 150-200 bucks and intercoolers ~100 bucks. and im a cheap bastard so it works out good for us all.

 

this guy said it was 8.5:1 but now that you mention the 8:1 i think ive heard that somewhere too...hmm...

 

"2002 Pontiac Trans Am
822 RWHP 753 RWTQ @5800RPM
C5-R 427 ATI F1 16 lbs of Boost
O2 Sensors, 93 Oct Pump Gas
Stock Computer, LSX Intake, 2 Bar HPTUNERS TUNE, LSX 90mm TB
"No Nitrous Needed", "No ALKY Needed"
"Do not make me downshift on your A@@, Too Late you have been dispatched!!!" "

 

you guys are right it is 8:1 i dont know where i came up with 8.5:1

 

im pretty sure it does. the lower the octane then you will start to knock earlier and more than if your running high octane race gas