Turbo Size questions
Thread Starter
Launching!
Joined: Jul 2011
Posts: 206
Likes: 1
From: Indianapolis
Turbo Size questions What would be the proper turbo size for a stock LS1?
I know its a noob question, but i have looked around on here.. everyone who has done a turbo has also done H/C/I/E.. I just want to do all my exhaust and turbo set up. change the other stuff down the road, Like when i blow up my stock engine..
And no that's not my goal, because I could do that with spray and do it a lot cheaper.. So please no turbo that is going to start spooling way late in the power band, I want something that is going to give me a good punch pretty early on but not choke me out at 5K either...
And and what will I need as far as fuel system stuff, Injector size and fuel pump
I know its a noob question, but i have looked around on here.. everyone who has done a turbo has also done H/C/I/E.. I just want to do all my exhaust and turbo set up. change the other stuff down the road, Like when i blow up my stock engine..
And no that's not my goal, because I could do that with spray and do it a lot cheaper.. So please no turbo that is going to start spooling way late in the power band, I want something that is going to give me a good punch pretty early on but not choke me out at 5K either...
And and what will I need as far as fuel system stuff, Injector size and fuel pump
Last edited by T/A2000; Apr 26, 2012 at 03:43 PM.
Thread Starter
Launching!
Joined: Jul 2011
Posts: 206
Likes: 1
From: Indianapolis
thank you very much, now what about injectors? will i need to change them? or will the stock ones work without leaning out to much? I know its a lot of questions, but where to you guys run your oil return?
How much power are you planning to make? Oil return goes either in the very front of the pan or on the side of the pan. If you do a search you will find some pictures.
Thread Starter
Launching!
Joined: Jul 2011
Posts: 206
Likes: 1
From: Indianapolis
I am looking to make as much as I can safely, with a turbo and fuel system mods.. I want room to grow, when I decide to build my engine.. Don't really need to do that at the moment, Car runs perfect and no noises.. but its still all stock and that depresses me 
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Thread Starter
Launching!
Joined: Jul 2011
Posts: 206
Likes: 1
From: Indianapolis
Got a turbo Hope this one is going to work well enough GTK-850, Got it from a buddy of mine for super cheap.. Love having good friends that also like cars lol..
And its brand new!
And its brand new!
Thread Starter
Launching!
Joined: Jul 2011
Posts: 206
Likes: 1
From: Indianapolis
Its going to be stock with a turbo for a while, until i get done building a few cars for a friend of mine.. Trying to earn some coin to buy more stuff, Have a friend that is buying a LS7 from me... That money will be used for Most of the engine build up, Then just getting suspension done.. I hope by next year I will just be able to go all out, and have this thing done the way i want it..
TECH Fanatic
Joined: Sep 2010
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Well here are the calculations.
CI x RPM x .5 x VE / 1768 (Rule of thumb stock engines are generally 85% VE)
This gives you your air flow needed in CFM.
To get your pressure ratio its 14.7 + boost PSI / 14.7.
Now you need to figure out how much the boost will add to your base CFM.
Base CFM x PR =
That tells you how much air the turbo needs to flow.
Now most compressor maps are done in lbs/min.
So take the CFM and times it by .0691 and it gives you lbs/min.
Look at a compressor map, plot your PR and your lbs a min. You want them to intersect in the highest efficiency island for a perfect match. Do this with various RPMs and any boost level you want to run. Plot like 4 dots. You want to make sure they all fall to the right of the very left line (surge limit).
So hes a stock LS1.
346 x 6500 x .5 x .85 / 1768 = ~541CFM
14.7 + 7 / 14.7 = 1.48 (7lbs of Boost)
541 x 1.48 = 800CFM (how much it will need to flow under 7psi of boost)
800 x .0691 = 55lbs/min
So you need to look at a compressor map and plot 55 on the bottom and 1.48 on the side and see where they meet on the map.
There is no compressor map for the GTK yet. They say they are comparable to a T72 but flow more. A T72 would not be a good choice at all. A T76 would be a pretty damn good choice.
CI x RPM x .5 x VE / 1768 (Rule of thumb stock engines are generally 85% VE)
This gives you your air flow needed in CFM.
To get your pressure ratio its 14.7 + boost PSI / 14.7.
Now you need to figure out how much the boost will add to your base CFM.
Base CFM x PR =
That tells you how much air the turbo needs to flow.
Now most compressor maps are done in lbs/min.
So take the CFM and times it by .0691 and it gives you lbs/min.
Look at a compressor map, plot your PR and your lbs a min. You want them to intersect in the highest efficiency island for a perfect match. Do this with various RPMs and any boost level you want to run. Plot like 4 dots. You want to make sure they all fall to the right of the very left line (surge limit).
So hes a stock LS1.
346 x 6500 x .5 x .85 / 1768 = ~541CFM
14.7 + 7 / 14.7 = 1.48 (7lbs of Boost)
541 x 1.48 = 800CFM (how much it will need to flow under 7psi of boost)
800 x .0691 = 55lbs/min
So you need to look at a compressor map and plot 55 on the bottom and 1.48 on the side and see where they meet on the map.
There is no compressor map for the GTK yet. They say they are comparable to a T72 but flow more. A T72 would not be a good choice at all. A T76 would be a pretty damn good choice.
Last edited by F0x Slaughter; Apr 30, 2012 at 01:38 PM.
now im assuming a 76mm with the 1.15ar is on front mounts.
what would you recommend for rear mounts? just curious. im about to pull a trigger myself on a T72 or T76 with either a .81 or .96 but im just not sure which one i really want.
not meaning to thread jack but thought this would help with info as well for the op and myself.
