Another Turbo Lq4 question...
Thread Starter
Staging Lane
Joined: May 2019
Posts: 73
Likes: 6
From: Northern VA
Another Turbo Lq4 question... Oh sure, this discussed many times before, I know. What I've read and gathered are either older posts and/or kinda inconclusive. Need fresh inputs to help me to decide. Here's what I have and my goal:
1972 Camaro Pro touring. Test fitted LQ4 and 4L80E and relocated accessories to clear stuff. F body oil pan, corvette water pump. Been working on hot side for a while. Almost finished. Passenger side top mount single turbo. 10.5:1 CR. 317 heads, forged piston/rods with ARP studs, BTR stage 2 cam with matching springs, etc. Wanting 850+ to wheels on E85. %100 street car. want to see some boost by 3000 RPM (Quick spool). Thinking, dual Aeromotive 340 or dual Walbro 450s in tank. Thinking 90# Injectors. Stock ECM. will maintain P/S, A/C.
Now, based on what I've read here, I was leaning toward S475 83/75 T4 1.1AR from forced induction. Then some said S475 is small for a 6.0, go with S480, Then again some said S475 is enough for what you want. Some said VS 7578. Today, I called FI and I've told something totally different. He said S476 96/76 billet 1.32 A/R, advising 1.1 A/R will blow my head gasket resulting in too much back pressure! I'm not opposed to T6 over T4, but I'm not sure if my hood will close and clear T6 housing. He also said we solved that issue by welding a v band instead of flange making it shorter. To what I know, 1.32 A/R with 96 mm turbine won't spool quick even on a 6.0. Not sure. Need some help to figure this out and put it aside. budget is about a grand for turbo. Thank you.
1972 Camaro Pro touring. Test fitted LQ4 and 4L80E and relocated accessories to clear stuff. F body oil pan, corvette water pump. Been working on hot side for a while. Almost finished. Passenger side top mount single turbo. 10.5:1 CR. 317 heads, forged piston/rods with ARP studs, BTR stage 2 cam with matching springs, etc. Wanting 850+ to wheels on E85. %100 street car. want to see some boost by 3000 RPM (Quick spool). Thinking, dual Aeromotive 340 or dual Walbro 450s in tank. Thinking 90# Injectors. Stock ECM. will maintain P/S, A/C.
Now, based on what I've read here, I was leaning toward S475 83/75 T4 1.1AR from forced induction. Then some said S475 is small for a 6.0, go with S480, Then again some said S475 is enough for what you want. Some said VS 7578. Today, I called FI and I've told something totally different. He said S476 96/76 billet 1.32 A/R, advising 1.1 A/R will blow my head gasket resulting in too much back pressure! I'm not opposed to T6 over T4, but I'm not sure if my hood will close and clear T6 housing. He also said we solved that issue by welding a v band instead of flange making it shorter. To what I know, 1.32 A/R with 96 mm turbine won't spool quick even on a 6.0. Not sure. Need some help to figure this out and put it aside. budget is about a grand for turbo. Thank you.
You can't look at it as a car built around a turbo...it all has to work together. That cam is going to favor a bigger turbine (which has been all the rage for the better part of a decade for all the wrong reasons) and a compressor that won't get sucked dry before it has a chance to spool up. That S476 1.32 would get the job done and probably be your best bet at a quick spooling setup and not stop that big cam up. I don't know where a 1.1 AR housing is going to be able to pop a head gasket though... Unless something else is built improperly, extra backpressure is just going to choke up the chamber with residual exhaust and actually drop cylinder pressure. That's what EGR does. If you want that cam for the lope sound, you'll have to go big on the hot side to make the power. T6 is probably a must. That said, I've made 1300hp on a T4 Borg before...but it was paired with the right camshaft to get the job done with a smaller hot side.
TECH Fanatic
Joined: Dec 2019
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Under the right conditions, even the big T6 will spool very fast on a 6.0.
I had a billet S475/87 1.10 T4 on a 5.3 and I was hitting boost before 3k and it made just over your goals, completely topped out.
If you don't want to try and fit a T6, go for the bigger T4 options.
VSRacing sells a billet S480 with a 96mm turbine wheel in a 1.25 A/R T4 that might give you the turbine clearance you need.
I had a billet S475/87 1.10 T4 on a 5.3 and I was hitting boost before 3k and it made just over your goals, completely topped out.
If you don't want to try and fit a T6, go for the bigger T4 options.
VSRacing sells a billet S480 with a 96mm turbine wheel in a 1.25 A/R T4 that might give you the turbine clearance you need.
a completly devided hot side 2 1/4 pipe combined with a good tune and converter will spool pretty fast. . i went from a borg 80/83 t4 with a single feed merged hotside to a devided t6 80/96 borg and it spooled much faster. car went from 9.50s on 20 psi boost to 9.0s on 18 psi boost. .if you are going to run e85 go to a bigger injector.160# or 210#
in my opinion there is no downside to a 96 turbine on a 6.0 engine. a 78/75 will spool faster in most cases but will be fighting backpressure once you really start turning it up .the 96 turbine t6 is worth 100 hp over the smaller turbine when cranked up. jmho
in my opinion there is no downside to a 96 turbine on a 6.0 engine. a 78/75 will spool faster in most cases but will be fighting backpressure once you really start turning it up .the 96 turbine t6 is worth 100 hp over the smaller turbine when cranked up. jmho
TECH Regular
Joined: Apr 2017
Posts: 424
Likes: 41
From: Worcester, Mass
Oh sure, this discussed many times before, I know. What I've read and gathered are either older posts and/or kinda inconclusive. Need fresh inputs to help me to decide. Here's what I have and my goal:
1972 Camaro Pro touring. Test fitted LQ4 and 4L80E and relocated accessories to clear stuff. F body oil pan, corvette water pump. Been working on hot side for a while. Almost finished. Passenger side top mount single turbo. 10.5:1 CR. 317 heads, forged piston/rods with ARP studs, BTR stage 2 cam with matching springs, etc. Wanting 850+ to wheels on E85. %100 street car. want to see some boost by 3000 RPM (Quick spool). Thinking, dual Aeromotive 340 or dual Walbro 450s in tank. Thinking 90# Injectors. Stock ECM. will maintain P/S, A/C.
Now, based on what I've read here, I was leaning toward S475 83/75 T4 1.1AR from forced induction. Then some said S475 is small for a 6.0, go with S480, Then again some said S475 is enough for what you want. Some said VS 7578. Today, I called FI and I've told something totally different. He said S476 96/76 billet 1.32 A/R, advising 1.1 A/R will blow my head gasket resulting in too much back pressure! I'm not opposed to T6 over T4, but I'm not sure if my hood will close and clear T6 housing. He also said we solved that issue by welding a v band instead of flange making it shorter. To what I know, 1.32 A/R with 96 mm turbine won't spool quick even on a 6.0. Not sure. Need some help to figure this out and put it aside. budget is about a grand for turbo. Thank you.
1972 Camaro Pro touring. Test fitted LQ4 and 4L80E and relocated accessories to clear stuff. F body oil pan, corvette water pump. Been working on hot side for a while. Almost finished. Passenger side top mount single turbo. 10.5:1 CR. 317 heads, forged piston/rods with ARP studs, BTR stage 2 cam with matching springs, etc. Wanting 850+ to wheels on E85. %100 street car. want to see some boost by 3000 RPM (Quick spool). Thinking, dual Aeromotive 340 or dual Walbro 450s in tank. Thinking 90# Injectors. Stock ECM. will maintain P/S, A/C.
Now, based on what I've read here, I was leaning toward S475 83/75 T4 1.1AR from forced induction. Then some said S475 is small for a 6.0, go with S480, Then again some said S475 is enough for what you want. Some said VS 7578. Today, I called FI and I've told something totally different. He said S476 96/76 billet 1.32 A/R, advising 1.1 A/R will blow my head gasket resulting in too much back pressure! I'm not opposed to T6 over T4, but I'm not sure if my hood will close and clear T6 housing. He also said we solved that issue by welding a v band instead of flange making it shorter. To what I know, 1.32 A/R with 96 mm turbine won't spool quick even on a 6.0. Not sure. Need some help to figure this out and put it aside. budget is about a grand for turbo. Thank you.
Thread Starter
Staging Lane
Joined: May 2019
Posts: 73
Likes: 6
From: Northern VA
I'll throw in my .02 from what I've learned, read, seen in the past few years. You want big turbo power you typically need bigger exhaust housings to not choke the motor up. On the flip side of that is obviously spool times can suffer. There's always a trade off. A loose converter can help with that immensely though and I noticed you made no mention of which one you'll be using. You should also watch a bunch of old Sloppy Mechanics videos and check out some of his combos. He's had quite a few combos with 6.0s. If you want a quick spool I'd suggest the new 78/75 from VS. You should hit 800 and if it's all out by then, see what direction you want to go. Take some notes about how that one spooled, what you liked, what you didn't like, and go from there. Get some real world experience first. I know a lot of people that bought something because it was "what they thought they wanted" and in the end they were disappointed because it just didnt feel or behave the way they wanted. I'd also like to add that 800rwhp in a street car is absolutely ridiculous and you'll never be able to take advantage of that power so most of the time you'll be on a lower boost setting. I agree with yenkomike, ditch the idea for those small injectors if you plan on running E85 and also go for some high flowing fuel pumps. Again just my opinion. Good luck on the build.
Last edited by Nariman; Feb 6, 2021 at 09:04 PM.
