Spool too fast?
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.
Ya 7875 packages nicer. Not many people lean enough on either one to matter so I don't get the appeal of a big clunky 75mm turbo for under 900hp. At least the S480 starts to make sense as most of the knock off 80+ mm weigh the same as the borg and are close to the same size, but then you have 1000+ worth of turbo so hopefully you use it to make it worth it.
With a manual car and a 700whp goal with "room to grow" I don't know what benefit there would be to going with larger 2.25" piping? It has proven to be effective well past the 1200 CHP zone. And while you may only gain 100-200 rpm of "spool" over 2.25"... why would you not want that in a manual trans setup? 2" is lighter, cheaper, and easier to package. I see zero reason to go larger with his goals. Look at ls1curt again. 383" LS 3400lbs trapping 160+ on a 2" hotside and T6 96mm wheel s400 frame.
The cast 75/102 compressor flows over 98lb per min. More than enough for the OP's goal. The "race" billet 75 should flow more. I'd go as far as to say with the larger exhaust housing, a "real" cast S475 out flows the 78/75. Thats looking at actual trap speeds put up by each turbo.(that I've seen) Having a larger compressor than is needed will only slow the spool down more. You want the smallest compressor to meet your goals if you are looking for quick spool. Again... 78/75 loses the battle there. The exhaust wheel design is also lacking over the S400 stuff.
The Holdner test is garbage IMO. He used an oddball tiny exhaust housings on the S475 that were setup for "twins" so peaked early and fell off early. Also wonder if the S475's he used were "real" Borg turbos.
I've yet to see someone trap as quickly on a 78/75 (of any model) compared to the T4 model S475 which has been 157 in a 6.0 at 3350 lbs in Stock48's nova.(998hp by weight/trap calc.) Maybe there are 78/75's out there than have done better, just saying I haven't seen one.
Thats super cool! What is a "gen2" Is that the "next gen" top of the line 78/75? He said 26lbs on the smallest motor, so leaning on it pretty hard. Wonder how heavy that mustang is? I"d still have to assume it's not 3350lbs which would mean the top of the line unit maxed out still isn't making the steam a cast s475 is on a 6.0? Or its making around the same?
I would guess a true S475 would top out above a 7875, but packaging and cost trump it if you go with a knock off lol. SS and another member talked about some of the differences between the original 7875 and the gen 2.5 I guess they're on now. Downpipe size is different, 6 vs. 7 wheel blade. Did the original ever come in a billet or that was only gen 2?
My question would be have the ebay $270 or the typical "billet wheel only" or Cast wheel 78/75's come anywhere close to the big trap speeds as the "top of the line" gen2 version? I believe there are 4-5 models. Some are exactly the same dimensions as the original cast unit but have billet wheels. 7 blade, 6 blade, and the latest "S" curve wheel. All with the same exh wheels I believe? Then a slew of different compressor and exhaust housings.So hard to tell!
A set of $270 twins would be my choice to party at big numbers. Screw all the guessing games and high price tags with the bigger singles. They are likely all within 50-150 hp of each other potential wise anyway until you step up to the large frame 100mm+ exhaust wheels and $3000-4000 price tags!
A set of $270 twins would be my choice to party at big numbers. Screw all the guessing games and high price tags with the bigger singles. They are likely all within 50-150 hp of each other potential wise anyway until you step up to the large frame 100mm+ exhaust wheels and $3000-4000 price tags!
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Verdad Gallardo The S475 specs I saw were 44lbs VS vs racing site claiming 28lbs for the 78/75.
With a manual car and a 700whp goal with "room to grow" I don't know what benefit there would be to going with larger 2.25" piping? It has proven to be effective well past the 1200 CHP zone. And while you may only gain 100-200 rpm of "spool" over 2.25"... why would you not want that in a manual trans setup? 2" is lighter, cheaper, and easier to package. I see zero reason to go larger with his goals. Look at ls1curt again. 383" LS 3400lbs trapping 160+ on a 2" hotside and T6 96mm wheel s400 frame.
The cast 75/102 compressor flows over 98lb per min. More than enough for the OP's goal. The "race" billet 75 should flow more. I'd go as far as to say with the larger exhaust housing, a "real" cast S475 out flows the 78/75. Thats looking at actual trap speeds put up by each turbo.(that I've seen) Having a larger compressor than is needed will only slow the spool down more. You want the smallest compressor to meet your goals if you are looking for quick spool. Again... 78/75 loses the battle there. The exhaust wheel design is also lacking over the S400 stuff.
The Holdner test is garbage IMO. He used an oddball tiny exhaust housings on the S475 that were setup for "twins" so peaked early and fell off early. Also wonder if the S475's he used were "real" Borg turbos.
I've yet to see someone trap as quickly on a 78/75 (of any model) compared to the T4 model S475 which has been 157 in a 6.0 at 3350 lbs in Stock48's nova.(998hp by weight/trap calc.) Maybe there are 78/75's out there than have done better, just saying I haven't seen one.
With a manual car and a 700whp goal with "room to grow" I don't know what benefit there would be to going with larger 2.25" piping? It has proven to be effective well past the 1200 CHP zone. And while you may only gain 100-200 rpm of "spool" over 2.25"... why would you not want that in a manual trans setup? 2" is lighter, cheaper, and easier to package. I see zero reason to go larger with his goals. Look at ls1curt again. 383" LS 3400lbs trapping 160+ on a 2" hotside and T6 96mm wheel s400 frame.
The cast 75/102 compressor flows over 98lb per min. More than enough for the OP's goal. The "race" billet 75 should flow more. I'd go as far as to say with the larger exhaust housing, a "real" cast S475 out flows the 78/75. Thats looking at actual trap speeds put up by each turbo.(that I've seen) Having a larger compressor than is needed will only slow the spool down more. You want the smallest compressor to meet your goals if you are looking for quick spool. Again... 78/75 loses the battle there. The exhaust wheel design is also lacking over the S400 stuff.
The Holdner test is garbage IMO. He used an oddball tiny exhaust housings on the S475 that were setup for "twins" so peaked early and fell off early. Also wonder if the S475's he used were "real" Borg turbos.
I've yet to see someone trap as quickly on a 78/75 (of any model) compared to the T4 model S475 which has been 157 in a 6.0 at 3350 lbs in Stock48's nova.(998hp by weight/trap calc.) Maybe there are 78/75's out there than have done better, just saying I haven't seen one.
I get it, I've seen ~1000whp with the S476 on fairly low boost and it ran 8.5's at 3700lbs, it works well enough for what it is but its not my go to turbo and not everyone has a ton of room in the engine bay.
My question would be have the ebay $270 or the typical "billet wheel only" or Cast wheel 78/75's come anywhere close to the big trap speeds as the "top of the line" gen2 version? I believe there are 4-5 models. Some are exactly the same dimensions as the original cast unit but have billet wheels. 7 blade, 6 blade, and the latest "S" curve wheel. All with the same exh wheels I believe? Then a slew of different compressor and exhaust housings.So hard to tell!
A set of $270 twins would be my choice to party at big numbers. Screw all the guessing games and high price tags with the bigger singles. They are likely all within 50-150 hp of each other potential wise anyway until you step up to the large frame 100mm+ exhaust wheels and $3000-4000 price tags!
A set of $270 twins would be my choice to party at big numbers. Screw all the guessing games and high price tags with the bigger singles. They are likely all within 50-150 hp of each other potential wise anyway until you step up to the large frame 100mm+ exhaust wheels and $3000-4000 price tags!
The 100+mm turbine turbos aren't that hateful these days, the borg 100+ mm turbine can be had under $2000, the VSR 110 or 113 mm turbines for under $1500, On3 has a 94/103 turbo for under $1000. Granted that may still be out of some budgets, but they are readily available.
It sucks! lol. Literally had the Cast 94mm in the shopping cart and was going to pull the trigger when a bud sent me links to the a few guys having issues with them! I trust Viren at VSR to stand behind his stuff. Been great working with him in the past. IMO it says something that he doesn't stock a "promod" version of those turbos selling at like prices. You'd think if it was a good unit, he'd have them as well.
I had a cast 7875 and a billet 7875. The billet might spool 200-300 rpms faster. The cast version sounded better, you could hear more turbo noise. I have a 5.3, automatic GTO. it spools pretty quickly, but its nothing like nitrous, supercharger (non centrifugal) or na. There is a nice smooth but quick ramp into boost. I have a 2.25 crossover also. I have no regrets on my setup except I'd like a gen 2 7875 with a bigger down pipe....but that wasnt out 2 years ago when I built my setup. I dont have a drag car, its full weight, probably close to 4000lbs with me in it. With a good boost controller, you can control your boost how it ramps in. But I've never felt it was ever just too fast of a spool.
I had a cast 7875 and a billet 7875. The billet might spool 200-300 rpms faster. The cast version sounded better, you could hear more turbo noise. I have a 5.3, automatic GTO. it spools pretty quickly, but its nothing like nitrous, supercharger (non centrifugal) or na. There is a nice smooth but quick ramp into boost. I have a 2.25 crossover also. I have no regrets on my setup except I'd like a gen 2 7875 with a bigger down pipe....but that wasnt out 2 years ago when I built my setup. I dont have a drag car, its full weight, probably close to 4000lbs with me in it. With a good boost controller, you can control your boost how it ramps in. But I've never felt it was ever just too fast of a spool.
I did a log the other night and just looked at it for you. So I was cruising 35mph in second gear. 3100rpms. Punch it. (3600 stall, so it’s gonna flash when I hit it)By 5500 I had full boost at 14psi.
I have a 3” down pipe which merged into a OVAL 3.5”, goes past my frame rail and merged back to a 3” to a single 3” all the way out the back with a borla muffler.
Last edited by Kfxguy; Jun 20, 2020 at 03:59 PM.
Hard to for me to give input cuz I’ve never had a manual car. T6 1.10 s475 with a 4” dp on a million mile 5.3... The other day I was cruising around 20ish mph at 3k (going off my terrible memory) I went to 80% throttle and hit 5psi (that was gate pressure) in 0.5 seconds according to the log. And I am nearly positive I have leaks at my vbands (I don’t use flex pipes and I welded up the crossover off the car on the bench. She moved a good bit when welded. Rookie mistake)
This t6 Borg spools faster than the t4 .96 master power t70 (Haven’t heard that name in awhile) on my last car. Doesn’t even make sense to me tbh
This t6 Borg spools faster than the t4 .96 master power t70 (Haven’t heard that name in awhile) on my last car. Doesn’t even make sense to me tbh