Help with turbine ar sizing for rear mount
Thread Starter
Staging Lane
Joined: Oct 2017
Posts: 66
Likes: 6
From: Waverly, NE
Help with turbine ar sizing for rear mount I have a 2010 Sierra 5.3 CC 4x4 with 275/60/20's that I want to build a rear mount turbo system and run on e85 running not more than maybe 7psi. I have tuned it to run e85 NA, and it is driven daily- about 40-45k/year. The truck has an unkown spec TSP cam from the PO, which is big enough that it will not idle smooth/at all below about 750-800 rpm. I plan on degreeing it this fall to find out the specs. I'm completely new to turbos, so I've been doing a LOT of searching and reading all over the last month or so.
I have considered front, but am set on remote mounting. The truck will probably never see a strip. I want to increase the highway fuel economy (11-13mpg at 77-80mph on e85), and make it so my wife doesn't complain that it doesn't "get up to speed as fast as her TB LTZ when she gives it gas". That said, my goals are I would like to make it more responsive at stoplights under 'wife' and lighter throttle, as well as more power for climbing hills at highway and interstate speeds (no more converter unlocking), but not to the extent of breaking piston rings, tranny, etc. Since highway crusing speed is about 1800rpm, I'd like to start building boost by then.
I'm looking hard at the On3 76/65 with a .68 ar, or their 70mm with a .68 ar. Is the turbine AR too small?
Is my thought process that a larger turbo will help reduce pumping losses under vacuum, or would a 70mm do a better job?
I have considered front, but am set on remote mounting. The truck will probably never see a strip. I want to increase the highway fuel economy (11-13mpg at 77-80mph on e85), and make it so my wife doesn't complain that it doesn't "get up to speed as fast as her TB LTZ when she gives it gas". That said, my goals are I would like to make it more responsive at stoplights under 'wife' and lighter throttle, as well as more power for climbing hills at highway and interstate speeds (no more converter unlocking), but not to the extent of breaking piston rings, tranny, etc. Since highway crusing speed is about 1800rpm, I'd like to start building boost by then.
I'm looking hard at the On3 76/65 with a .68 ar, or their 70mm with a .68 ar. Is the turbine AR too small?
Is my thought process that a larger turbo will help reduce pumping losses under vacuum, or would a 70mm do a better job?
I'd put a Borgwarner S366 with 68mm turbine and .88 a/r. Even remote mounting it, it will still light pretty fast and make the 7psi on a 5.3 pretty easy. I had one, a 73mm turbine/91 a/r as a front mount on my 5.3 c10 and it spools to 10psi very fast!
I have a 2010 Sierra 5.3 CC 4x4 with 275/60/20's that I want to build a rear mount turbo system and run on e85 running not more than maybe 7psi. I have tuned it to run e85 NA, and it is driven daily- about 40-45k/year. The truck has an unkown spec TSP cam from the PO, which is big enough that it will not idle smooth/at all below about 750-800 rpm. I plan on degreeing it this fall to find out the specs. I'm completely new to turbos, so I've been doing a LOT of searching and reading all over the last month or so.
I have considered front, but am set on remote mounting. The truck will probably never see a strip. I want to increase the highway fuel economy (11-13mpg at 77-80mph on e85), and make it so my wife doesn't complain that it doesn't "get up to speed as fast as her TB LTZ when she gives it gas". That said, my goals are I would like to make it more responsive at stoplights under 'wife' and lighter throttle, as well as more power for climbing hills at highway and interstate speeds (no more converter unlocking), but not to the extent of breaking piston rings, tranny, etc. Since highway crusing speed is about 1800rpm, I'd like to start building boost by then.
I'm looking hard at the On3 76/65 with a .68 ar, or their 70mm with a .68 ar. Is the turbine AR too small?
Is my thought process that a larger turbo will help reduce pumping losses under vacuum, or would a 70mm do a better job?
I have considered front, but am set on remote mounting. The truck will probably never see a strip. I want to increase the highway fuel economy (11-13mpg at 77-80mph on e85), and make it so my wife doesn't complain that it doesn't "get up to speed as fast as her TB LTZ when she gives it gas". That said, my goals are I would like to make it more responsive at stoplights under 'wife' and lighter throttle, as well as more power for climbing hills at highway and interstate speeds (no more converter unlocking), but not to the extent of breaking piston rings, tranny, etc. Since highway crusing speed is about 1800rpm, I'd like to start building boost by then.
I'm looking hard at the On3 76/65 with a .68 ar, or their 70mm with a .68 ar. Is the turbine AR too small?
Is my thought process that a larger turbo will help reduce pumping losses under vacuum, or would a 70mm do a better job?
Thread Starter
Staging Lane
Joined: Oct 2017
Posts: 66
Likes: 6
From: Waverly, NE
Your goals for this build are unrealistic. A rear mount is useless for stoplight pulls, since the lag is far greater than a front mount setup. You will NOT increase fuel economy, and you will NOT change anything about the converter unlocking. A rear mount is an inferior design in every aspect except weight balance and packaging. Since the nature of such a design adds weight over a front mount, even the balance issue is debatable. This is coming from a former rear mount turbo owner who has directly compared builds with the same turbo and intercooler in front and rear mount configurations.
https://www.performancetrucks.net/forums/forced-induction-159/my-turbo-mileage-project-478072/
The 88 a/r is open, the 91 is divided, BW considers the same as far as flow is concerned in there matchbot software.
I recommended the smaller 68mm turbine since you are waiting to rear mount it. I have a 73mm on my truck which is front mounted.
IMO, you would be better off getting a manifold like I build and putting the turbo up front. I started with the STS and ran it for 2 years before building my first front mount manifold. Rear mounts work, but nothing like a front mount and you don't have a oil pump to worry about failing. (mine failed twice!)
I recommended the smaller 68mm turbine since you are waiting to rear mount it. I have a 73mm on my truck which is front mounted.
IMO, you would be better off getting a manifold like I build and putting the turbo up front. I started with the STS and ran it for 2 years before building my first front mount manifold. Rear mounts work, but nothing like a front mount and you don't have a oil pump to worry about failing. (mine failed twice!)
Thread Starter
Staging Lane
Joined: Oct 2017
Posts: 66
Likes: 6
From: Waverly, NE
The 88 a/r is open, the 91 is divided, BW considers the same as far as flow is concerned in there matchbot software.
I recommended the smaller 68mm turbine since you are waiting to rear mount it. I have a 73mm on my truck which is front mounted.
IMO, you would be better off getting a manifold like I build and putting the turbo up front. I started with the STS and ran it for 2 years before building my first front mount manifold. Rear mounts work, but nothing like a front mount and you don't have a oil pump to worry about failing. (mine failed twice!)
I recommended the smaller 68mm turbine since you are waiting to rear mount it. I have a 73mm on my truck which is front mounted.
IMO, you would be better off getting a manifold like I build and putting the turbo up front. I started with the STS and ran it for 2 years before building my first front mount manifold. Rear mounts work, but nothing like a front mount and you don't have a oil pump to worry about failing. (mine failed twice!)
My brother in law is trying to sell me on a front mount using leftover parts from all the kits they install. That was his big concern was oil pump too. Seems like the exa pump is the way to go.
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So from your original post you have a heavy truck with a 5.3 and you want better throttle respons and quicker acceleration down low in the rpm band. You want boost available when cruising down the highway at 1800 rpm. In my opinion a turbo rear or front won't take care of your goals. A positive displacement supercharger will like the lsa blower that everyone is using these days as a cheap way to get some boost. It will give you better throttle response and instant torque no matter the rpm. Look into it the cost isn't crazy to adapt one and it will meet all your goals easily. I know you only wanted to hear about turbos but I feel like your pick the wrong path to reach your goals here.
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I don't think theres anything wrong with your plan. You'll find lots of folks are skeptical about rear mount turbos simply because the cars that havent made power arent designed well as a combination as a whole and are heard about as not working. You hear about that bad, its human nature with everything.
Research more and you'll find stock exhaust manifolds, wrapped exhausts, small-mid size AR exhaust housings, less restrictive exhaust wheels, smaller cams with minimal overlap, and a tight 3000-3600rpm stall speed torque converter tends to work best in rear mount configuration for what you're looking for. You could do all this stuff and add the turbo later no problem. I think I'd go with the .96 AR 76/65
Your end result may not be EXACTLY what youre after, but will be darn close, and a lot of fun. You might try researching 'Denmah' on here's wifes red chevy work truck, its a similar idea and makes boost quicker, but its a front mount. But really, if the kits designed well, that shouldnt matter much, you can mount the turbo right behind the cab and the distance isnt as far as say a rear mount fbody or vette.
Research more and you'll find stock exhaust manifolds, wrapped exhausts, small-mid size AR exhaust housings, less restrictive exhaust wheels, smaller cams with minimal overlap, and a tight 3000-3600rpm stall speed torque converter tends to work best in rear mount configuration for what you're looking for. You could do all this stuff and add the turbo later no problem. I think I'd go with the .96 AR 76/65
Your end result may not be EXACTLY what youre after, but will be darn close, and a lot of fun. You might try researching 'Denmah' on here's wifes red chevy work truck, its a similar idea and makes boost quicker, but its a front mount. But really, if the kits designed well, that shouldnt matter much, you can mount the turbo right behind the cab and the distance isnt as far as say a rear mount fbody or vette.