.96AR ve 1.25AR?
.96AR ve 1.25AR? So I have a vsr billet 1st gen 7875 on heads and cam ls1. It will turn 7000rpm, runs good but I’d like to maximize what I have. I also car about fuel mileage as I drive this car a lot. Yea, I’m dumb to care about that, right? Well my choice. So before the turbo, on the interstate it would cruise at an average or 25-27mpg. Now with the turbo I’ve fought to get it to 19-21mpg. My thought is the exhaust turbine is choking it up so I’d like to open it some. Plus it would likely add some top end power too. I talked to viren at vs racing and he offers a 1.25 housing that bolt on, my exhaust outlet will go from 3” to 4”. I have a 3” to 3.5” downpipe so I’ll change that from 4” to 3.5”, but still will flow better. So what do you guys think about doing this? Mistake? My spool will get laggy? Not worth it? Or yea it would be worthwhile?
If your concern is the at turbine side of the turbo is causing a restriction resulting in less mpg, the restriction would be the turbine wheel, not the housing. IMO I’m not sure you’d see the improvement that you’re looking for in regards to mpg during cruise.
For power, I’d go for the 1.25 housing. I’ve got a 1.25 t4 housing on my Borg with the small wheel and at 19.5 psi I’m only seeing 1.3-1.4:1 backpressure to boost ratio. Spoil is as quick as I want it, but I also run an onboard air system for my boost control.
For power, I’d go for the 1.25 housing. I’ve got a 1.25 t4 housing on my Borg with the small wheel and at 19.5 psi I’m only seeing 1.3-1.4:1 backpressure to boost ratio. Spoil is as quick as I want it, but I also run an onboard air system for my boost control.
If your concern is the at turbine side of the turbo is causing a restriction resulting in less mpg, the restriction would be the turbine wheel, not the housing. IMO I’m not sure you’d see the improvement that you’re looking for in regards to mpg during cruise.
For power, I’d go for the 1.25 housing. I’ve got a 1.25 t4 housing on my Borg with the small wheel and at 19.5 psi I’m only seeing 1.3-1.4:1 backpressure to boost ratio. Spoil is as quick as I want it, but I also run an onboard air system for my boost control.
For power, I’d go for the 1.25 housing. I’ve got a 1.25 t4 housing on my Borg with the small wheel and at 19.5 psi I’m only seeing 1.3-1.4:1 backpressure to boost ratio. Spoil is as quick as I want it, but I also run an onboard air system for my boost control.
How do you drive the car? If you see any boost at all in your daily commute then self control will probably help you more than a larger ar turbo (as far as mpg's go).
I swapped from the TC7868 .96 ar to the T7575 1.15 ar with billet wheel. Spool was about the same, mpg about the same. Power carried further but made very similar numbers on the same amount of boost. I beat the **** out of my car tho without regard to mpg.
Of course, if you can fit it, a borg with a large turbine would be a better option. I made the swap because my current system doesn't allow for such a physically large turbo and I got a deal on the T7575.
S480 is sitting on the shelf now waiting to be thrown on.
I swapped from the TC7868 .96 ar to the T7575 1.15 ar with billet wheel. Spool was about the same, mpg about the same. Power carried further but made very similar numbers on the same amount of boost. I beat the **** out of my car tho without regard to mpg.
Of course, if you can fit it, a borg with a large turbine would be a better option. I made the swap because my current system doesn't allow for such a physically large turbo and I got a deal on the T7575.
S480 is sitting on the shelf now waiting to be thrown on.
Its not the housing its the turbine wheel. Ar doesnt play much part . Can only flow so much through a 75mm turbine . You need the turbo I have . T4, billet 80/83.. made 750 wheel through a powerglide . Almost maxed out my SEP 1500s and dual 450s lol .
How do you drive the car? If you see any boost at all in your daily commute then self control will probably help you more than a larger ar turbo (as far as mpg's go).
I swapped from the TC7868 .96 ar to the T7575 1.15 ar with billet wheel. Spool was about the same, mpg about the same. Power carried further but made very similar numbers on the same amount of boost. I beat the **** out of my car tho without regard to mpg.
Of course, if you can fit it, a borg with a large turbine would be a better option. I made the swap because my current system doesn't allow for such a physically large turbo and I got a deal on the T7575.
S480 is sitting on the shelf now waiting to be thrown on.
I swapped from the TC7868 .96 ar to the T7575 1.15 ar with billet wheel. Spool was about the same, mpg about the same. Power carried further but made very similar numbers on the same amount of boost. I beat the **** out of my car tho without regard to mpg.
Of course, if you can fit it, a borg with a large turbine would be a better option. I made the swap because my current system doesn't allow for such a physically large turbo and I got a deal on the T7575.
S480 is sitting on the shelf now waiting to be thrown on.
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The outlet on the 1.25 a/r turbine is 4” vs mine right now is 3”...,...for some reason I think that would flow more. I’m not understanding how that 4” hole is going to mate up with a turbine wheel that has a 3” hole right now. I asked viren to send me a pic.
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Verdad Gallardo How do you drive the car? If you see any boost at all in your daily commute then self control will probably help you more than a larger ar turbo (as far as mpg's go).
I swapped from the TC7868 .96 ar to the T7575 1.15 ar with billet wheel. Spool was about the same, mpg about the same. Power carried further but made very similar numbers on the same amount of boost. I beat the **** out of my car tho without regard to mpg.
Of course, if you can fit it, a borg with a large turbine would be a better option. I made the swap because my current system doesn't allow for such a physically large turbo and I got a deal on the T7575.
S480 is sitting on the shelf now waiting to be thrown on.
I swapped from the TC7868 .96 ar to the T7575 1.15 ar with billet wheel. Spool was about the same, mpg about the same. Power carried further but made very similar numbers on the same amount of boost. I beat the **** out of my car tho without regard to mpg.
Of course, if you can fit it, a borg with a large turbine would be a better option. I made the swap because my current system doesn't allow for such a physically large turbo and I got a deal on the T7575.
S480 is sitting on the shelf now waiting to be thrown on.
s480 ain’t gonna come close to fitting in my car lol.
Hmmm. A bigger housing certainly will flow more... but it won’t help unless that’s actually the problem. Regardless you are putting more back pressure on the exhaust than before, and your not going to eliminate that without removing the turbo.
since the car was NA before and you went turbo, there had to be a tune change. Most popular thing is going to SD and deleting the maf. So if your VE table was off but you were using the MAF before, this could play part. Regardless, with that hugely different exhaust and intake piping, a complete retune with a good amount of street driving will be needed to dial it in. Nothing about the way that engine takes in air and exhaust it is the same.
You could spent time leaning out the part throttle and cruise to get it to be a bit more frugal with the gas.Timing adjustment in the cruise cells could help a good bit as well. A mail order tune or a dyno tune (most of which don’t spend much time on drivability...) is not going to cut it.
since the car was NA before and you went turbo, there had to be a tune change. Most popular thing is going to SD and deleting the maf. So if your VE table was off but you were using the MAF before, this could play part. Regardless, with that hugely different exhaust and intake piping, a complete retune with a good amount of street driving will be needed to dial it in. Nothing about the way that engine takes in air and exhaust it is the same.
You could spent time leaning out the part throttle and cruise to get it to be a bit more frugal with the gas.Timing adjustment in the cruise cells could help a good bit as well. A mail order tune or a dyno tune (most of which don’t spend much time on drivability...) is not going to cut it.
Getting the turbo sized so you're pulling less vacuum at cruise will give you better mpg from my experience. Whether this means a larger compressor or a different turbine, moving more air at less load combined with the right timing and AFR will help mpg as the efficiency goes up. My TA in sig would do 30 mpg on the highway with a cammed forged 383.
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You could spent time leaning out the part throttle and cruise to get it to be a bit more frugal with the gas.Timing adjustment in the cruise cells could help a good bit as well. A mail order tune or a dyno tune (most of which don’t spend much time on drivability...) is not going to cut it.
A larger a/r won't do much if it's still choking down at the wheel.
I think tuning will help more than any turbine swap could. At the low loads and rpm you are talking nothing is really backing up in the exhaust system. It's never going to be quite as efficient as a higher compression small cam NA engine with nice long tubes, etc.
A Borg "83" mm wheel is actually 1 mm smaller then the VSR 7875 because the Borg turbine has an 83/74 wheel, VSR has a 83/75 turbine wheel. People always confuse Precision advertising numbers to Borg advertising numbers, exducer vs inducer! That said sloppy put down like 920whp through an auto with the VSR Gen 2 7875 recently, but even the Gen 1 made 800. AR certainly does play a part in your powerband, especially when on the edge of turbo sizing.
Hmmm. A bigger housing certainly will flow more... but it won’t help unless that’s actually the problem. Regardless you are putting more back pressure on the exhaust than before, and your not going to eliminate that without removing the turbo.
since the car was NA before and you went turbo, there had to be a tune change. Most popular thing is going to SD and deleting the maf. So if your VE table was off but you were using the MAF before, this could play part. Regardless, with that hugely different exhaust and intake piping, a complete retune with a good amount of street driving will be needed to dial it in. Nothing about the way that engine takes in air and exhaust it is the same.
You could spent time leaning out the part throttle and cruise to get it to be a bit more frugal with the gas.Timing adjustment in the cruise cells could help a good bit as well. A mail order tune or a dyno tune (most of which don’t spend much time on drivability...) is not going to cut it.
since the car was NA before and you went turbo, there had to be a tune change. Most popular thing is going to SD and deleting the maf. So if your VE table was off but you were using the MAF before, this could play part. Regardless, with that hugely different exhaust and intake piping, a complete retune with a good amount of street driving will be needed to dial it in. Nothing about the way that engine takes in air and exhaust it is the same.
You could spent time leaning out the part throttle and cruise to get it to be a bit more frugal with the gas.Timing adjustment in the cruise cells could help a good bit as well. A mail order tune or a dyno tune (most of which don’t spend much time on drivability...) is not going to cut it.
seriously. All smartassness aside. I’m quite versed in tuning lol. It’s dialed in to 3% or less on my trims. I have a 2 bar speed density custom operating system. So there’s no maf. My ve and maf were dialed when it was n/a also. So that’s not it. I have real time tuning also and I’ve dialed in my timing and fuel at cruise.
BTW, this housing i'm looking at swapping to is a divided housing. I just saw a dyno test where they tested a divided and non divided housing and the divided picked up a few hp but made a good bit more in the lower and mid range and spooled faster. So maybe in this case i wont give up much spool, but make more power all the way around. win-win. I hope
wait. So I have to tune it after a turbo? Are you serious. I had no idea!
seriously. All smartassness aside. I’m quite versed in tuning lol. It’s dialed in to 3% or less on my trims. I have a 2 bar speed density custom operating system. So there’s no maf. My ve and maf were dialed when it was n/a also. So that’s not it. I have real time tuning also and I’ve dialed in my timing and fuel at cruise.
seriously. All smartassness aside. I’m quite versed in tuning lol. It’s dialed in to 3% or less on my trims. I have a 2 bar speed density custom operating system. So there’s no maf. My ve and maf were dialed when it was n/a also. So that’s not it. I have real time tuning also and I’ve dialed in my timing and fuel at cruise.
i have never spent much time with economy tuning because I drive a company vehicle every day and everything else is just driven for fun. So if it makes more power/torque being on the rich side, that’s where I always put it