Slow Spool Billet 7875 1.25AR normal?
Slow Spool Billet 7875 1.25AR normal? Hi all,
I recently upgraded from a T4 GT45 STD 69mm T4 1.05ar to the T4 billet 7875 1.25 AR
The GT45 spooled pretty quick, didn't have to go full throttle to get into boost and would start building boost quick - within a second. With this 7875, it takes a few seconds going practically WOT to build boost. Seems like it stays in vacuum so long. Another thing is the 7875 is dead quiet, you can't even tell I have a turbo anyone. No spooly noises
.
I feel like this was a really bad upgrade lol the GT45 was perfect, tons of power and quick boost and was super cheap. Only reason I replaced it was because the GT45 broke some fins, probably due to heat / running rich
I recently upgraded from a T4 GT45 STD 69mm T4 1.05ar to the T4 billet 7875 1.25 AR
The GT45 spooled pretty quick, didn't have to go full throttle to get into boost and would start building boost quick - within a second. With this 7875, it takes a few seconds going practically WOT to build boost. Seems like it stays in vacuum so long. Another thing is the 7875 is dead quiet, you can't even tell I have a turbo anyone. No spooly noises
.I feel like this was a really bad upgrade lol the GT45 was perfect, tons of power and quick boost and was super cheap. Only reason I replaced it was because the GT45 broke some fins, probably due to heat / running rich
Hi all,
I recently upgraded from a T4 GT45 STD 69mm T4 1.05ar to the T4 billet 7875 1.25 AR
The GT45 spooled pretty quick, didn't have to go full throttle to get into boost and would start building boost quick - within a second. With this 7875, it takes a few seconds going practically WOT to build boost. Seems like it stays in vacuum so long. Another thing is the 7875 is dead quiet, you can't even tell I have a turbo anyone. No spooly noises .
I feel like this was a really bad upgrade lol the GT45 was perfect, tons of power and quick boost and was super cheap. Only reason I replaced it was because the GT45 broke some fins, probably due to heat / running rich
I recently upgraded from a T4 GT45 STD 69mm T4 1.05ar to the T4 billet 7875 1.25 AR
The GT45 spooled pretty quick, didn't have to go full throttle to get into boost and would start building boost quick - within a second. With this 7875, it takes a few seconds going practically WOT to build boost. Seems like it stays in vacuum so long. Another thing is the 7875 is dead quiet, you can't even tell I have a turbo anyone. No spooly noises
.I feel like this was a really bad upgrade lol the GT45 was perfect, tons of power and quick boost and was super cheap. Only reason I replaced it was because the GT45 broke some fins, probably due to heat / running rich
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What sort of tune tweaking? I'm guessing timing. It's a big shame, I actually wanted a turbo that would spool faster than the GT45 - after searching posts, I saw everyone saying 7875 spooled faster than the GT45. Now that I think of it, I wonder if they were referring to the .96 ar 7875
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Verdad Gallardo Sounds pretty similar to mine: PPV L77 6.0L, summit stg 2 turbo cam, Circle D 3200, 2.92 gear, 3 bar MAF tune, straight 93, 2.5 hotside to T4 log, 3-1/2" dp to dual 2-1/2" w/ stock mufflers on 9#'s. I don't have any numbers but it runs pretty well on the street. Once I have some more time, I'd like to run it up to about 15#'s and see what it does on the dragy.
Everyone idea of fast or slow spool is different in my experience. Look at the exh wheel to compressor wheel ratio. If the compressor wheel is bigger than the exhaust wheel it is generally more sluggish to spool. You want a larger exh wheel for more leverage on teh comp wheel IMO. The reason the GT45 isn't a super fast spooling BA turbo is because the exh housing is pretty large and the wheel design is old. That said it has a great wheel ratio and on a larger 6.0 and runs very well until the compressor is out of steam.
Did you go with the EBay $270 billet 78/75? Or a vendor unit? I wonder if those $270 ebay clones are to good to be true. Or if they are the same as the vendors sell. Myself and 2 other forum members tried some 72/68's out a few years back and they were plain horrible! Was like the compressor/exh. wheels didnt fit snugly in the housings and they were super inefficient. Curious what the tolerances are like on those cheap 78/75's. (i've never had one)
Did you go with the EBay $270 billet 78/75? Or a vendor unit? I wonder if those $270 ebay clones are to good to be true. Or if they are the same as the vendors sell. Myself and 2 other forum members tried some 72/68's out a few years back and they were plain horrible! Was like the compressor/exh. wheels didnt fit snugly in the housings and they were super inefficient. Curious what the tolerances are like on those cheap 78/75's. (i've never had one)
This is a short clip, gives you an idea of how a 7875 billet wheel with a .96 ar spools. I was cruising and I put it in third gear on the shifter, smashed it, downshifted to second and you can see when the boost comes in. In my opinion, it’s about ideal because it’s not too fast where it’s abrupt to break stuff but it’s not too slow either.
Everyone idea of fast or slow spool is different in my experience. Look at the exh wheel to compressor wheel ratio. If the compressor wheel is bigger than the exhaust wheel it is generally more sluggish to spool. You want a larger exh wheel for more leverage on teh comp wheel IMO. The reason the GT45 isn't a super fast spooling BA turbo is because the exh housing is pretty large and the wheel design is old. That said it has a great wheel ratio and on a larger 6.0 and runs very well until the compressor is out of steam.
Did you go with the EBay $270 billet 78/75? Or a vendor unit? I wonder if those $270 ebay clones are to good to be true. Or if they are the same as the vendors sell. Myself and 2 other forum members tried some 72/68's out a few years back and they were plain horrible! Was like the compressor/exh. wheels didnt fit snugly in the housings and they were super inefficient. Curious what the tolerances are like on those cheap 78/75's. (i've never had one)
Did you go with the EBay $270 billet 78/75? Or a vendor unit? I wonder if those $270 ebay clones are to good to be true. Or if they are the same as the vendors sell. Myself and 2 other forum members tried some 72/68's out a few years back and they were plain horrible! Was like the compressor/exh. wheels didnt fit snugly in the housings and they were super inefficient. Curious what the tolerances are like on those cheap 78/75's. (i've never had one)
It's a vendor unit, $800
between the slow spool, compared to the ebay GT45, and also how you can't even hear it, I think I'm going to sell this turbo and jump to something else
Mine is a daily driver and I'm only on about 9-10#'s. I went with the 1.25 a/r because it's a 6.0L and historically the exhaust housing has been the restriction. Works fine for me, I'm happy with my setup, was just curious why it's not working well for the OP?
Tune can make a huge difference as can weight etc.