Spool too fast?
Spool too fast? I have had quite a few LS engines but this is my first time going turbo. Car will be 6 speed manual and weighs roughly 2900 with me in it. 99% street car. Aluminum 5.3 sbe. I will have a 4" downpipe. I was looking at the VS 7875 billet turbo and the VS gen 2 7875. Right now I'm looking for ~700whp but wanted to give myself some headroom. I was pretty set on getting the gen2 7875 until I saw this video from Richard Holdener that scared me a bit about the spool time:. https://youtu.be/AOEOFz_TjZA
But then honestly I was thinking that perhaps I want some lag time in the spool to help keep from blowing the tires off too easily and/or soften the blow to the drivetrain. I know that the car being a manual means faster spool would probably help at the track but the car is a street car.
Also thought I should really get something with a 4" exhaust outlet to match up with my downpipe.
Any thoughts? Maybe get a t4 s475 with a 1.1 AR? Other?
Thanks
But then honestly I was thinking that perhaps I want some lag time in the spool to help keep from blowing the tires off too easily and/or soften the blow to the drivetrain. I know that the car being a manual means faster spool would probably help at the track but the car is a street car.
Also thought I should really get something with a 4" exhaust outlet to match up with my downpipe.
Any thoughts? Maybe get a t4 s475 with a 1.1 AR? Other?
Thanks
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Joined: Dec 2019
Posts: 1,129
Likes: 478
I have had quite a few LS engines but this is my first time going turbo. Car will be 6 speed manual and weighs roughly 2900 with me in it. 99% street car. Aluminum 5.3 sbe. I will have a 4" downpipe. I was looking at the VS 7875 billet turbo and the VS gen 2 7875. Right now I'm looking for ~700whp but wanted to give myself some headroom. I was pretty set on getting the gen2 7875 until I saw this video from Richard Holdener that scared me a bit about the spool time:. https://youtu.be/AOEOFz_TjZA
But then honestly I was thinking that perhaps I want some lag time in the spool to help keep from blowing the tires off too easily and/or soften the blow to the drivetrain. I know that the car being a manual means faster spool would probably help at the track but the car is a street car.
Also thought I should really get something with a 4" exhaust outlet to match up with my downpipe.
Any thoughts? Maybe get a t4 s475 with a 1.1 AR? Other?
Thanks
But then honestly I was thinking that perhaps I want some lag time in the spool to help keep from blowing the tires off too easily and/or soften the blow to the drivetrain. I know that the car being a manual means faster spool would probably help at the track but the car is a street car.
Also thought I should really get something with a 4" exhaust outlet to match up with my downpipe.
Any thoughts? Maybe get a t4 s475 with a 1.1 AR? Other?
Thanks
Manual trans wont spool faster than an auto. Maybe RPM wise earlier, but not "time" earlier.
If packaging isn't a concern, I don't see the appeal of the 78/75 when the S475 is proven to spool more quickly and meets his goals power wise. It's a tank of a unit and a better turbo IMO. Especially if you buy a "real" T4 1.10T4 S475 and not a knock off. They have been proven to 950ish wheel on small bore stuff and out spool the 78/75.
Check out ls1curt on this forum and his success with the T4 S475. 950whp and backed it up with 159 mph trap speeds at 3000lbs. And it spools more quickly... Seems like a win to me.
Check out ls1curt on this forum and his success with the T4 S475. 950whp and backed it up with 159 mph trap speeds at 3000lbs. And it spools more quickly... Seems like a win to me.
Last edited by Forcefed86; Jun 15, 2020 at 08:29 AM.
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Verdad Gallardo Thanks for all replies. I had a couple of follow up questions:
1) is having a 3" turbine outlet stepped up to a 4" downpipe a significant detriment vs a 4" turbine outlet paired to the same 4" downpipe?
2) what is the overall dimensions of an t6 s475 vs t4 s475 to a t4 7875?
3) is there such a thing as too quick of spool on the street? I am genuinely concerned about blowing the tires off, and the hit to the drivetrain. Car is a 6 speed, FYI
Thanks to everyone
1) is having a 3" turbine outlet stepped up to a 4" downpipe a significant detriment vs a 4" turbine outlet paired to the same 4" downpipe?
2) what is the overall dimensions of an t6 s475 vs t4 s475 to a t4 7875?
3) is there such a thing as too quick of spool on the street? I am genuinely concerned about blowing the tires off, and the hit to the drivetrain. Car is a 6 speed, FYI
Thanks to everyone
Thanks for all replies. I had a couple of follow up questions:
1) is having a 3" turbine outlet stepped up to a 4" downpipe a significant detriment vs a 4" turbine outlet paired to the same 4" downpipe?
2) what is the overall dimensions of an t6 s475 vs t4 s475 to a t4 7875?
3) is there such a thing as too quick of spool on the street? I am genuinely concerned about blowing the tires off, and the hit to the drivetrain. Car is a 6 speed, FYI
Thanks to everyone
1) is having a 3" turbine outlet stepped up to a 4" downpipe a significant detriment vs a 4" turbine outlet paired to the same 4" downpipe?
2) what is the overall dimensions of an t6 s475 vs t4 s475 to a t4 7875?
3) is there such a thing as too quick of spool on the street? I am genuinely concerned about blowing the tires off, and the hit to the drivetrain. Car is a 6 speed, FYI
Thanks to everyone
2) someone else will have to answer who has dimensions.
3) entirely personal preference. To me nothing is worse than a laggy turbo manual car on the street. Size the turbo right for the intended boost and power level and let the tuning deal with traction.
If packaging isn't a concern, I don't see the appeal of the 78/75 when the S475 is proven to spool more quickly and meets his goals power wise. It's a tank of a unit and a better turbo IMO. Especially if you buy a "real" T4 1.10T4 S475 and not a knock off. They have been proven to 950ish wheel on small bore stuff and out spool the 78/75.
Check out ls1curt on this forum and his success with the T4 S475. 950whp and backed it up with 159 mph trap speeds at 3000lbs. And it spools more quickly... Seems like a win to me.
Check out ls1curt on this forum and his success with the T4 S475. 950whp and backed it up with 159 mph trap speeds at 3000lbs. And it spools more quickly... Seems like a win to me.
Adds significant expense though right? My BW t6 1.10 s475 was like $700? Doing a t4 is gunna add to that. but I’ll bet it would light fast! Mine does with the t6 (auto car tho)
The 7875 is gunna be way cheaper (if your a frugal guy like me lol). Guess it depends on priority.
Yup, S475 is a big boy, almost twice the size as the standard older 78/75. That's why I mentioned the packaging thing first. If you have the room, its the way to go IMO.
A laggy setup isn't going to help you with anything. All that means is there is a delay in the power onset. Which is no fun with a manual. Then when the turbo does come on, it usually comes on violently. A lot of that can be tuned out.
Id stick with a twin scroll divided setup on a 1.10 T4 S475. Run a 2" hot side with a 38mm gate on each. Sounds more complex, but I found it easier than messing with merges. Also routing the 2" pipe is super easy and cheap. Small WG's are cheap as well. You can also double or even triple wrap the piping and insulate it really well for heat. I used mild steel and a mig. on factory exh. manifolds. No need to get fancy. Tough setup to beat spool wise IMO. I spool a S480 1.32 T6 with my 4.8 pretty darn well that way.
A laggy setup isn't going to help you with anything. All that means is there is a delay in the power onset. Which is no fun with a manual. Then when the turbo does come on, it usually comes on violently. A lot of that can be tuned out.
Id stick with a twin scroll divided setup on a 1.10 T4 S475. Run a 2" hot side with a 38mm gate on each. Sounds more complex, but I found it easier than messing with merges. Also routing the 2" pipe is super easy and cheap. Small WG's are cheap as well. You can also double or even triple wrap the piping and insulate it really well for heat. I used mild steel and a mig. on factory exh. manifolds. No need to get fancy. Tough setup to beat spool wise IMO. I spool a S480 1.32 T6 with my 4.8 pretty darn well that way.
Adds significant expense though right? My BW t6 1.10 s475 was like $700? Doing a t4 is gunna add to that. but I’ll bet it would light fast! Mine does with the t6 (auto car tho)
The 7875 is gunna be way cheaper (if your a frugal guy like me lol). Guess it depends on priority.
The 7875 is gunna be way cheaper (if your a frugal guy like me lol). Guess it depends on priority.
You can get the billet "race whee" t4 S475 from VSR for $570 shipped. Thats the route I'd go.
Their Cast T4 S475 is $429. That's the route I'd go if I was on a budget.
Similarly priced to their 78/75's. But that Ebay special 78/75 is tough to beat price wise.
Depends if you go knock off or not. The $270 78/75 on ebay is pretty darn appealing if they hold up.
You can get the billet "race whee" t4 S475 from VSR for $570 shipped. Thats the route I'd go.
Their Cast T4 S475 is $429. That's the route I'd go if I was on a budget.
Similarly priced to their 78/75's. But that Ebay special 78/75 is tough to beat price wise.
You can get the billet "race whee" t4 S475 from VSR for $570 shipped. Thats the route I'd go.
Their Cast T4 S475 is $429. That's the route I'd go if I was on a budget.
Similarly priced to their 78/75's. But that Ebay special 78/75 is tough to beat price wise.
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Joined: Nov 2003
Posts: 13,616
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From: Norn Iron
I have had quite a few LS engines but this is my first time going turbo. Car will be 6 speed manual and weighs roughly 2900 with me in it. 99% street car. Aluminum 5.3 sbe. I will have a 4" downpipe. I was looking at the VS 7875 billet turbo and the VS gen 2 7875. Right now I'm looking for ~700whp but wanted to give myself some headroom. I was pretty set on getting the gen2 7875 until I saw this video from Richard Holdener that scared me a bit about the spool time:. https://youtu.be/AOEOFz_TjZA
But then honestly I was thinking that perhaps I want some lag time in the spool to help keep from blowing the tires off too easily and/or soften the blow to the drivetrain. I know that the car being a manual means faster spool would probably help at the track but the car is a street car.
Also thought I should really get something with a 4" exhaust outlet to match up with my downpipe.
Any thoughts? Maybe get a t4 s475 with a 1.1 AR? Other?
Thanks
But then honestly I was thinking that perhaps I want some lag time in the spool to help keep from blowing the tires off too easily and/or soften the blow to the drivetrain. I know that the car being a manual means faster spool would probably help at the track but the car is a street car.
Also thought I should really get something with a 4" exhaust outlet to match up with my downpipe.
Any thoughts? Maybe get a t4 s475 with a 1.1 AR? Other?
Thanks
No chance of spooling too fast.
And it's much easier to reduce/ramp boost on a fast spooling car, than it is to magically gain boost lower down in a laggy piece of junk.
What do you guys think about these 3 options:
1)Billet s475 ( https://turbo4less.com/product/vsr-7...ar-t4-divided/ )
2)billet 7875 ( https://turbo4less.com/product/vsr-billet-7875-96ar-t4/ )
3)gen2 7875 ( https://turbo4less.com/product/vsr-n...n-7875-billet/ )
I asked VS about the size differences, he said "
You are going to be around 1” difference in G1 7875 vs a s400 chassis unit.
The difference in g2 is ½ “
I like the gen 2 7875 in almost every way with the exception of the spool lag shown in this test by Holdener :
I like the spool, cost and size of the billet gen 1 7875, but don't like that the turbine has only 3" outlet
I like the s475 in terms of the specs on paper seem about perfect, but no data from others using it and it is the biggest, and for some reason I think that 1" difference might be a bit more than claimed.
1)Billet s475 ( https://turbo4less.com/product/vsr-7...ar-t4-divided/ )
2)billet 7875 ( https://turbo4less.com/product/vsr-billet-7875-96ar-t4/ )
3)gen2 7875 ( https://turbo4less.com/product/vsr-n...n-7875-billet/ )
I asked VS about the size differences, he said "
You are going to be around 1” difference in G1 7875 vs a s400 chassis unit.
The difference in g2 is ½ “
I like the gen 2 7875 in almost every way with the exception of the spool lag shown in this test by Holdener :
I like the spool, cost and size of the billet gen 1 7875, but don't like that the turbine has only 3" outlet
I like the s475 in terms of the specs on paper seem about perfect, but no data from others using it and it is the biggest, and for some reason I think that 1" difference might be a bit more than claimed.