Worth going from 83mm 1.25 ar to 87mm wheel?
11-26-2016, 08:07 PM
#1
Worth going from 83mm 1.25 ar to 87mm wheel? Worth going from my s475/83 1.25 t4 to an 87mm wheel with a 1.1 or 1.25 housing? Lights off pretty good now, just looking for a little more oomph?
5.3, 9.5:1, 243 heads, JFR 218 cam, truck intake and throttle body, shift at around 6500. Looking to make boost/more boost quicker. Heard a 92mm could be laggy on my 5.3. No backpressure measurements. Footbrake car. What do you guys think?
5.3, 9.5:1, 243 heads, JFR 218 cam, truck intake and throttle body, shift at around 6500. Looking to make boost/more boost quicker. Heard a 92mm could be laggy on my 5.3. No backpressure measurements. Footbrake car. What do you guys think?
Last edited by 3 window; 11-26-2016 at 08:19 PM.
11-27-2016, 10:10 AM
#2
that's the same question I have . I'm running a s480/83 1.25 on my 6.0 . it feels pretty good at 14 psi and runs 9.90@136 mph at that boost but am I giving anything up ? I am running less cam than you . I do know stock48 ran 8.9 with his 475/83 and 5.7 1/8 mile in his nova.
11-27-2016, 02:30 PM
#3
Need to know exactly what wheel sizes you are talking about. What are the major/minor wheel sizes?
The "83mm" S475 is usually a 74/83... Most go by the exducer on exh wheel sizing. (borgs screwy). So in the rest of the turbo world that's a 74mm exh wheel.
The big step up is the 87/96. So going from a 74 to an 87 is pretty huge and worth it IMO. But I wouldn't bother stepping up unless you went with the big wheel.
The "83mm" S475 is usually a 74/83... Most go by the exducer on exh wheel sizing. (borgs screwy). So in the rest of the turbo world that's a 74mm exh wheel.
The big step up is the 87/96. So going from a 74 to an 87 is pretty huge and worth it IMO. But I wouldn't bother stepping up unless you went with the big wheel.
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11-27-2016, 04:06 PM
#8
This is probably a very stupid way to look at it but if you subtract 87/96 you get 9. If you subtract 74/83 you get 9. I wonder if they are all broken down the same way with a 9mm split. If so the other t4 wheels would be 78/87 and 83/92. I've been researching this as well with not much luck. I wonder if drturbo will chime in, or maybe worth a call tomorrow. I will say I have a t4 s475 74/83 1.10 on a JFR 218 camed ls1 and on the street it is awesome. It's a Torque monster, but I believe the small turbine leaves a lot on the table up top.
11-27-2016, 05:36 PM
#9
Makes sense to me... the 81/87 doesn't fit the bill there, but the rest sounds right. (Think the 81/87 is an oddball S410 wheel)
My 1.10 83/74 S475 was great until about 19-20lbs on a mild 5.3 (JFR 212/212 cam). After that it stopped making the same big MPH gains. If you arent' pushing boost in the high teens, I can't see a larger unit doing all that much for you. (with a mild 5.3 that is)
Best bet would be to take your car out on 15lbs or so and keep adding boost a pound at a time until the gains level off. If it's still not fast enough, grab a more capable turbo. Pushing it after that point with the same turbo is what causes problems.
My 1.10 83/74 S475 was great until about 19-20lbs on a mild 5.3 (JFR 212/212 cam). After that it stopped making the same big MPH gains. If you arent' pushing boost in the high teens, I can't see a larger unit doing all that much for you. (with a mild 5.3 that is)
Best bet would be to take your car out on 15lbs or so and keep adding boost a pound at a time until the gains level off. If it's still not fast enough, grab a more capable turbo. Pushing it after that point with the same turbo is what causes problems.
11-27-2016, 05:53 PM
#10
Think a 1.10 housing with my 83 wheel be worth it over my 1.25? I don't have any back pressure readings, so I can't help there. But if it'll still rev clean. It come on sooner and faster, that's what I'm after. I'd honestly say 17 psi or so would be about it.
11-27-2016, 09:34 PM
#11
The housings are only $150 or so. It would be worth it to try. On my ls1 it will pull clean to 6500 with the 1.10 83 wheel. I don't see why you would have any issues if your not having any now. At the end of the day the turbine is the real restriction imo.
11-28-2016, 05:32 AM
#12
I would try that first. My 6.0 with the 83 1.25 starts nosing over after about 17 PSI but still picking up about 14 HP per lb until 19 PSI. If response is all you are looking for then for sure try the smaller housing first. They even pop up used occasionally, I know I saw one in the classifieds a few months back.
11-29-2016, 09:53 AM
#13
This is probably a very stupid way to look at it but if you subtract 87/96 you get 9. If you subtract 74/83 you get 9. I wonder if they are all broken down the same way with a 9mm split. If so the other t4 wheels would be 78/87 and 83/92. I've been researching this as well with not much luck. I wonder if drturbo will chime in, or maybe worth a call tomorrow. I will say I have a t4 s475 74/83 1.10 on a JFR 218 camed ls1 and on the street it is awesome. It's a Torque monster, but I believe the small turbine leaves a lot on the table up top.
OP wouldnt have a problem with the 92mm turbine. odds are it would spool faster.
11-29-2016, 10:40 AM
#14
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NREC Turbocompressor Design Software I use NREC design software for my turbocompressor work.
As we know the compressor wheel/cover has a map, find the "sweet spot" and match this to you engine's air flow requirements.
Once this is known, I have another method, "Delta-P" measurement.
MEASURE the IMAP/EMAP BEFORE spending money/work on a "guess"
I am VERY sure that many here would like that information NEEDED to provide the best advice.
You could also look at the Turbine/Compressor as a torque driven device.
The turbine HP required to drive the compressor wheel effects EMAP.
Would you be willing to provide a report of your EMAP ?
Lance
As we know the compressor wheel/cover has a map, find the "sweet spot" and match this to you engine's air flow requirements.
Once this is known, I have another method, "Delta-P" measurement.
MEASURE the IMAP/EMAP BEFORE spending money/work on a "guess"
I am VERY sure that many here would like that information NEEDED to provide the best advice.
You could also look at the Turbine/Compressor as a torque driven device.
The turbine HP required to drive the compressor wheel effects EMAP.
Would you be willing to provide a report of your EMAP ?
Lance
11-30-2016, 09:46 AM
#16
Alot of it depends on how you approach the whole system. My approach makes the big turbine work better.
