hey gang,
i have been doing a lot of reading and research, including use of that fancy search feature, over the last several months and i am still completely lost as to how to pick the right size turbo for my planned combo.

the planned combo:
Patriot Stage2 LQ9 (71cc) heads
216/220, .525/.535, 114lsa Cam
LS6 intake or LSx 78mm
FMIC
Ported TB
and all the usual bolt-ons installed on a stock 99-02 motor.

i was thinking this combo would run safely on 10-12psi on pump gas once tuned out. i plan to shift aroudn 6500 and will have the rev limiter set at 7000

any help on turbo sizing for my combo is greatly appreciated.

thanks
tim

 

Boost is a measure of restriction, it doesn't really mean anything. Set a horsepower goal.

 

???? i am not really sure how to guess that. anyone got a program to model the combo i am considering?
i woudl like to be in the 450 to the wheels area(through a glide and a dana44)
all of the sizing information i have been reading talks about P/R and lbs of air, so i am not sure how to come up with an accurate hp guess for you.

thanks
tim

 

according to http://www.forcedinductions.com/help.htm a T88 will be around 78-80% efficiancy to supply 68cu/ft of air(what the 346 cid LS1 chart says i will need at 6500rpm with 12psi).
does this sound right? could i really need that big a turbo?

thanks
tim

 

Your engine won't live long with that set up and that much boost. You also need Fuel Injectors and Fuel pump. And chances are you will need a forged bottom end shortly after that.
But who knows, there are a couple guys that haven't had to yet.

 

fuel system and tuning are covered, 255lph pump, larger injectors, and tuning will be done with HP Tuners.
why do you think it will hurt the motor?

 

Well... you might not have any problems at all.
Someone please correct me if I am wrong, Rob Raymer, Mighty Mouse and Harlan are pushing big HP numbers and boost and achieving incredible results on a stock bottom end.
But without forged internals, something sooner or later is going to give with that much boost.
Disclaimer: I am FAR from being an expert. I just would hate for you to put this setup together and have bend some pistons and rods on your first trip out.

 

Again what type of power numbers. All the turbo sizing calculations are based on air flow. A lso a 255 lph pump only supports about 500-550 rwhp with a base pressure of 58 psi and 1:1 fuel pressure with boost.

www.performancetrends.com has a engine simulation program that is pretty good. They have a 10 day demo of the engine analyzer pro, after the ten days the program is around $550. Predicted pretty close number for my setup.

Gary

 

thanks for the tip on the analyzer.
i am going for 450 to the wheels(through a glide and a dana44), so i am trying to make 530ish at the crank. does the airflow information i got from http://www.forcedinductions.com/help.htm sound correct to anyone? or am i reading something wrong?

thanks
tim

 

I have a 67mm garrett on my pickup truck on a 6.0 litre. It made 630 at the flywheel with the truck manifolds. It made 457 at the wheels, that was with AWD and 20 inch wheels.

Kurt

 

Yes that is the correct airflow. It its based on a constant EV but it is close enough.

Jose

 

if your going for around 450rwhp then you should probably use around a T66. with enough room to grow to a bit over 550
a T76 will get you to about from about 500-700.

if your only going for 450rwhp and your using a glide (im guessing streetability doesnt matter much) why not just do some better flowing heads and a huge cam. that could get you your power goals alot easier.

 

i wouldent think your fuel is covered! better be in the range of 60# injectors
high flow fuel rails
bigger lines

 

we have rods,pistons,fasteners but stock crank and block

on stock pistons and compression.. i would not consider any margin of safety at 12 psi without race gas or alky spray..however it will also not take 12psi to get 450-500

 

Exactly. Building an engine and turbo setup to only make 450rwhp accompanied by a powerglide and dana rear just doesnt make sense to me. If you've gone that far, you might as well spend the money on a fuel system since the setup is capable of more like 600-700rwhp.

What are you planning to use the car for? Personal track goals, bracket racing, etc...

 

the reason i like the idea of FI to achieve this power level is so that i don't have to run a crazy huge cam and deal with a ton of drivability issues.

the car will be drivin to and from the track(all 3 tracks here in jersey are under 1.5hours from me) and will run on pump gas. i will be bracket racing the car in atco's points next year and i woudl like to run in the low 10's.
i also will be driving the car around town, to local cruise spots and to work from time to time.

at my desired power level the car should be perfectly capable of low 10's assuming i can hook it.

thanks
tim

 

First off do you know that a powerglide is a two speed transmission? some dont even have reverse. it isnt very streetable.
next off 450rwhp will not get you low tens, unless you take out about a 1000lbs on your car.
on a 3500lb car 600rwhp can get you low tens.

if you want a streetable car to dip in the tens you could either do nitrous or FI, or NA with alot of weight reduction.
for tranny id go with the T400 with a brake, its a 3 speed but a better choice then a 2speed.
what is your budjet, something to consider, if you have a low budjet id go with an iron block stroker and a small shot nitrous (should be high tens with just the iron block), if you have a desent budjet then go with something like the turbotech race kit with forged internals (either iron or aluminum)

 

Just wanted to add a datapoint...a T76 will take you fairly well beyond 700. I would say the range is more like 500 - 800rwhp...maybe even a bit more. I think the T76 is a great setup for a stock cube LS1. I get full boost 16psi by no later than 3500rpm and can make some nice power. I think its a great minimum compromise unit. Okay low psi response with a good bit of room to grow on the top end. I tried the T71 unit and the difference in spool up time was neglible. At 12psi, it pulled about 580rwhp with a fair amount of tuning effort. The T76 at the same boost level topped 600rwhp with no change tuning.

 

my car will weigh somewhere in the neighborhood of 2900lbs on teh starting line when it is finished

a powerglide and a th400 both have the same high gear, 1:1, so what is the difference? assuming correct TC selection both are easily driven on the street and the TH400 weighs approx 75lbs more and has 7% more internal resistance.

by the time i got all the parts seperately to do what you are suggesting i would have easily spent twice as much as i am spending by going with a motor+6spd w/ complete wiring+pcm+accessaries combo from a wrecked car(fully tested, 11k miles from 99ss, 6month warranty, and i am selling the complete 6spd set up to recover money, i got everything for $4500)
the combo you suggest woudl be nice, but i am not a nitrous fan(hate the idea of having to fill bottles all the time) and i plain old don't have teh money for it.
my combo sounds a lot fancier than it really is. the glide i picked up for $50 and grabbed a complete master rebuild kit for $175(gotta buy a manual valve body adn double ring servo still), the dana44 was actually in my old car so it costs nothign to throw the rear and complete disc brake set up onto the new car, and the motor/combo was picked based on being light weight and a cam that i got as a gift from a few friends.
i don't mean to sound rude but this is not somethign i am jumping into blind, i am 30 years old and have been playing with cars half my life. to my way of thinking turbocharging is the best way to add power when you need it without making a combination too radical to drive(big HC package), wasting power(turning a supercharger), or running out of power when it counts(empty bottle).

thanks for the advice on sizing as i originally asked, looks like a T66 or T76(<----leanign towards) is in my future.

thanks
tim

 

The LS1 likes a lot of SC/Turbo flow.

Go as large as you can fit.