Fitting Rotrex C38-92 on S52. Gains over c38-71/81?

[bladerealm124]

I've been unable to find any information on this setup (c38-91 or 92). Would this trim fit on an s52? Does anyone know how much bigger is it than an -71/81 and what power gains one could expect?

I'm considering swapping my -71 for a -91/92 unit but am unsure if it would be worth the trouble. I'm hoping that I could find a used one for $1000 or less and get a decent deal on a tweak for my current tune, and then sell my 71 trim. I plan on eventually moving to a whole new setup (turbo, twinscrew, or lsx swap) but since that it still a ways a way I figure a larger trim may be a good bump in power to hold me over and essentially plug and play with my current setup.

What power and curve advantages do you think the c38-92 would have over the 71/81 units? Other mods include m50 manifold, headers, exhaust(AA track pipe, system u)

[abradic]

Good thread

I'm sure there will be plenty of the 'don't waste your time and go turbo' thoughts, but this is an interesting and good question if your goals are to be in the 400 whp range. From what I gather, the C38-92 has a larger compressor and flows more than the C38-81 and hks 8550, and can be spun faster too. I also remember a few threads with the hks 8550 being pretty much 400 whp+ right out of the box with some mods like M50 manifold and catback. If you added cams, RMS or Raceland headers, trackpipe or SS mid pipe, bbtb, you should hypothetically be in the 430's to 440's. If you went all out and did headwork (p&p), maybe even touch the 450's? I would think that should be possible...maddog20/20 has all of those mods except the headwork on an hks kit and his dyno was in the 370's @6k rpm I believe, he was having issues and couldn't rev to 7k. That 1k more should have been good for about 50-60 whp. My guess is the C38-92 would give even better numbers than that, perhaps 20 whp better, and probably an even bigger gain over a C38-81 and C38-71. Hypothetically, an S52 with cams, headers, exhaust, M52 manifold, perhaps bbtb and the -92 running a pulley allowing it to spin to it's max with a proper tune should be in the 440's and headwork may net you even more.

Anyone out there go all out with a C38-81 setup? S52 with cams, M50 manifold, headers, exhaust, bbtb....basically full bolt ons and spinning the -81 to it's max?

[bladerealm124]

Good thread

I'm sure there will be plenty of the 'don't waste your time and go turbo' thoughts, but this is an interesting and good question if your goals are to be in the 400 whp range. From what I gather, the C38-92 has a larger compressor and flows more than the C38-81 and hks 8550, and can be spun faster too. I also remember a few threads with the hks 8550 being pretty much 400 whp+ right out of the box with some mods like M50 manifold and catback. If you added cams, RMS or Raceland headers, trackpipe or SS mid pipe, bbtb, you should hypothetically be in the 430's to 440's. If you went all out and did headwork (p&p), maybe even touch the 450's? I would think that should be possible...maddog20/20 has all of those mods except the headwork on an hks kit and his dyno was in the 370's @6k rpm I believe, he was having issues and couldn't rev to 7k. That 1k more should have been good for about 50-60 whp. My guess is the C38-92 would give even better numbers than that, perhaps 20 whp better, and probably an even bigger gain over a C38-81 and C38-71. Hypothetically, an S52 with cams, headers, exhaust, M52 manifold, perhaps bbtb and the -92 running a pulley allowing it to spin to it's max with a proper tune should be in the 440's and headwork may net you even more.

Anyone out there go all out with a C38-81 setup? S52 with cams, M50 manifold, headers, exhaust, bbtb....basically full bolt ons and spinning the -81 to it's max?

There is one member I know of who has the above setup but last I knew he hadn't gotten it dynoed. It's a black e36 running a 6-speed swap and a 3.91 diff. I'll see if I can dig him up later today

[pbonsalb]

The C38-92 is still less than a Vortech Si or T Trim in flow. The best you will do is get close to the numbers the Vortechs have done. 511 rwhp with all the mods at 18 psi from a Vortech T Trim is the pump gas record. I don't see the stock accessory drive having traction to run the Rotrex that hard. You need lower compression to run that much boost.

E85 with an E85 tune would be a great option.

[abradic]

The C38-92 is still less than a Vortech Si or T Trim in flow. The best you will do is get close to the numbers the Vortechs have done. 511 rwhp with all the mods at 18 psi from a Vortech T Trim is the pump gas record. I don't see the stock accessory drive having traction to run the Rotrex that hard. You need lower compression to run that much boost.

E85 with an E85 tune would be a great option.

I would think 511 rwhp is probably out of reach on an S52 on 93 with the C38-92, but maybe 450-480 whp is possible and repeatable on 93 pump. It would take all the mods and maybe headwork (p&p), but it would be a heck of a setup in the very high 400's...possibly 470's or 480's. If looking for a 93 pump setup to run 500+, then turbo is definitely the way. For the 400's, SC can be an option.

I can't remember who just did an E85 run on a vortech set up, it may have even been the sci @ 14 psi, and broke 500 rwhp and roughly 392 wtq. Still more to be had too, so the C38-92 on E85 would definitely break 500 rwhp.

[bladerealm124]

I would think 511 rwhp is probably out of reach on an S52 on 93 with the C38-92, but maybe 450-480 whp is possible and repeatable on 93 pump. It would take all the mods and maybe headwork (p&p), but it would be a heck of a setup in the very high 400's...possibly 470's or 480's. If looking for a 93 pump setup to run 500+, then turbo is definitely the way. For the 400's, SC can be an option.

I can't remember who just did an E85 run on a vortech set up, it may have even been the sci @ 14 psi, and broke 500 rwhp and roughly 392 wtq. Still more to be had too, so the C38-92 on E85 would definitely break 500 rwhp.

E85 would not be desirable for me(DD/commuter). But 450whp would definitely be nice as well as a solid torque boost. I wonder if this would be achievable on the -92 with stock cams and an updated tune. Hopefully I'll have an opportunity to find out by the end of the year.

On another note I wonder how much of a restriction my AA track pipe and UUC system U are as opposed to a single 3" or 3.5"

[pbonsalb]

Try for 450. My guess is it will take more boost than your stock compression will support on 93 pump gas with stock cams and maybe even with 256/264 Shricks. When you give up, go turbo.

[abradic]

The C38-92 is still less than a Vortech Si or T Trim in flow. The best you will do is get close to the numbers the Vortechs have done. 511 rwhp with all the mods at 18 psi from a Vortech T Trim is the pump gas record. I don't see the stock accessory drive having traction to run the Rotrex that hard. You need lower compression to run that much boost.

E85 with an E85 tune would be a great option.

I am assuming this is accurate, it's a quote from Zak @ AA on another forum through searches I found...

HKS 8555 is rated at 918 CFM
Rotrex C38 91/92 is rated at 1205 CFM
Vortech V3si is rated to 1150 CFM

Don't quote me 100% on those conversions, both manufacturers use some odd-ball flow rates instead of something standard like kg/hr, CFM, or lbs/hr.

The rotrex 92 offers a larger housing, think S-cover in the turbo world. The wheel is not setup any differently but the cover breathes better.

Now the comparison with the Vortech. There are alot of other factors not taken in to account here. These are peak flow numbers but do nothing to reveal how the blower acts in anything other than 100% speed. The wheel geometry can change the dynamics through the blower rev range quite a bit. It is noticeable that the Rotrex/HKS units offer more flow at lower revs than the Vortech, which tends to be a bit peaky. Blowers can be under/over spun etc.

I also saw another thread, can't find it again, essentially saying the same thing about flow where it's possible the V3si may have a slight advantage, but the big difference is part throttle and response where the Rotrex was better. The downside, according to them, was that you would have more heat so the air to air intercooler is a huge benefit.

OP, it seems like this -92 may be a worthy upgrade. As pbonsalb mentioned, if you spin it faster you may end up needing a lower compression gasket. I wonder if you would need a better intercooler than the one you have? I don't know what the AA intercooler is rated for and if pumping up to say 14-15 psi to get 450+ whp would require a better intercooler to avoid WI.

[bladerealm124]

I am assuming this is accurate, it's a quote from Zak @ AA on another forum through searches I found...





I also saw another thread, can't find it again, essentially saying the same thing about flow where it's possible the V3si may have a slight advantage, but the big difference is part throttle and response where the Rotrex was better. The downside, according to them, was that you would have more heat so the air to air intercooler is a huge benefit.

OP, it seems like this -92 may be a worthy upgrade. As pbonsalb mentioned, if you spin it faster you may end up needing a lower compression gasket. I wonder if you would need a better intercooler than the one you have? I don't know what the AA intercooler is rated for and if pumping up to say 14-15 psi to get 450+ whp would require a better intercooler to avoid WI.

Good info if accurate. I also have an 80mm pulley(coming from an 85mm) I may install once I get a wideband that should put me close to 14psi with my current trim. I have been hesitant to install it due to overspinning the blower to ~98k RPM, currently spinning around 92k if my old calculations were correct. I have also been concerned about it expediting my original head gaskets inevitable death. I hope to test out the 92 trim eventually but that is months down the road as I'm getting involved in some new business ventures

[abradic]

Good info if accurate. I also have an 80mm pulley(coming from an 85mm) I may install once I get a wideband that should put me close to 14psi with my current trim. I have been hesitant to install it due to overspinning the blower to ~98k RPM, currently spinning around 92k if my old calculations were correct. I have also been concerned about it expediting my original head gaskets inevitable death. I hope to test out the 92 trim eventually but that is months down the road as I'm getting involved in some new business ventures

Damn that responsibility! I've had some life events hold me up too. I have been wanting to go FI for quite some time, and it figures when I got funds together for it I got engaged, married, and the expenses that go with that. No regrets at all though Hopefully soon enough with FI. I would guess you should be over 400 whp and into the 410's at that boost level with your -81. That would probably expedite the hg though if it's showing any weakness, 14psi is quite a bit for a stock hg. If it doesn't hold up and goes down the road, schrick cams would be an awesome upgrade. Coupled with a -92 blower, you would see a heck of a jump in power. Any idea on what the AA intercooler is rated...meaning at what point is it not efficient enough? Hopefully it's fine for 14 psi.

[bladerealm124]

Damn that responsibility! I've had some life events hold me up too. I have been wanting to go FI for quite some time, and it figures when I got funds together for it I got engaged, married, and the expenses that go with that. No regrets at all though Hopefully soon enough with FI. I would guess you should be over 400 whp and into the 410's at that boost level with your -81. That would probably expedite the hg though if it's showing any weakness, 14psi is quite a bit for a stock hg. If it doesn't hold up and goes down the road, schrick cams would be an awesome upgrade. Coupled with a -92 blower, you would see a heck of a jump in power. Any idea on what the AA intercooler is rated...meaning at what point is it not efficient enough? Hopefully it's fine for 14 psi.

I think it should be fine at 14psi,not sure exactly how efficient it is. There are a few people that have run this pulley/setup. The only one who I know got numbers for it was jszy25 who put down 386whp but I'm not sure of his supporting mods. I believe he had the stock manifold so I think I would be a bit above that with my setup, possibly just over 400whp as you said. I hope to get a wideband in the near future and get this pulley installed. I just don't want to risk anything until my finances are more stable.

[abradic]

I think it should be fine at 14psi,not sure exactly how efficient it is. There are a few people that have run this pulley/setup. The only one who I know got numbers for it was jszy25 who put down 386whp but I'm not sure of his supporting mods. I believe he had the stock manifold so I think I would be a bit above that with my setup, possibly just over 400whp as you said. I hope to get a wideband in the near future and get this pulley installed. I just don't want to risk anything until my finances are more stable.

+1 on a wideband, definitely need to have that. Also a big +1 on being financially smart and staying within your finances. It's amazing how much easier that 400 whp mark is with that hks 8550 kit is vs the C38-81. You have the manifold and exhaust mods so I would guess you'll break that 400 barrier.

[abradic]

I've been unable to find any information on this setup (c38-91 or 92). Would this trim fit on an s52? Does anyone know how much bigger is it than an -71/81 and what power gains one could expect?

I'm considering swapping my -71 for a -91/92 unit but am unsure if it would be worth the trouble. I'm hoping that I could find a used one for $1000 or less and get a decent deal on a tweak for my current tune, and then sell my 71 trim. I plan on eventually moving to a whole new setup (turbo, twinscrew, or lsx swap) but since that it still a ways a way I figure a larger trim may be a good bump in power to hold me over and essentially plug and play with my current setup.

What power and curve advantages do you think the c38-92 would have over the 71/81 units? Other mods include m50 manifold, headers, exhaust(AA track pipe, system u)

Found this recently, and this looks like an incredible upgrade over the 71/81 units.

http://www.bimmerboost.com/content.p...ce=twitterfeed

I have many, many goodies sitting at home and will be getting a C38-92 based kit for my car in 2-3 months. I am still on the hunt for headers (AA would be nice since it will bolt up to my track pipe), will get a southbend clutch, probably AKG motor and trans bushings, and the kit within my time frame. I have Schricks (256/264), valve train with +1mm valves (will get all appropriate head work done), euro oil cooler, gauges sitting at home. So we will see if I can duplicate this, or come close. Maybe this tempts you to upgrade?!

[pbonsalb]

The 527 rwhp car is tuned on E85. Good stuff if you can get it.

[abradic]

The 527 rwhp car is tuned on E85. Good stuff if you can get it.

Oh, didn't realize it was E85. Well I guess I'll see how pump 93 does, as great as E85 is for more power, I would rather stick with pump.

[95AWM3]

Have you considered a meth/water injection kit to help out with achieving this? This is also something I am currently researching, as I am trying to get to the 450whp mark with my Si trim V3 car.

[pbonsalb]

You can do 450 with 93 plus meth. A few have done it. The record is 511 rwhp SAE Dynojet on 93 pump, done in 2007 by m3jasper with a NickG 60 lb tune with a Vortech t trim at 18 psi. I did 463/368 SAE Dynojet in 2009 but could not do any better due to belt slip. 93 plus meth, aa prototype 60 lb tune, Shrick 256/264, 0.098 MLS, ARPs, big headers and exhaust, rms water/air intercooler, Vortech t trim at 16 psi.

[bladerealm124]

Found this recently, and this looks like an incredible upgrade over the 71/81 units.

http://www.bimmerboost.com/content.p...ce=twitterfeed

I have many, many goodies sitting at home and will be getting a C38-92 based kit for my car in 2-3 months. I am still on the hunt for headers (AA would be nice since it will bolt up to my track pipe), will get a southbend clutch, probably AKG motor and trans bushings, and the kit within my time frame. I have Schricks (256/264), valve train with +1mm valves (will get all appropriate head work done), euro oil cooler, gauges sitting at home. So we will see if I can duplicate this, or come close. Maybe this tempts you to upgrade?!

Wow. I kind of wish you didn't show me this haha. This just renewed my love for this setup. Although it's e85 they are very impressive numbers. I do hope to upgrade to the 92 trim since it would be so easy to do with all the other parts already in place but I may wait until my current blower fails before I do. I have far too many other things to invest in in the near future. Slight possibility that I may be able to later this year. I still have a smaller 80mm pulley that I have yet to put on and am in need of a new driveshaft(worn U-joints). With subzero temperatures here lately and no garage things my M3 hasn't received the attention she deserves. Thanks for posting though, I've been waiting years to see the 92 trim on an s52, very exciting

[RK-Tunes]

that car is on a stock botttom e36 and oem headgasket
made 550whp uncorrected (real hp that it made that day. it was very cold out)

[E36 HateR]

his car was trapping very well for a supercharged car, deff put centri setups on the map!

[cj.surr]

What did this car trap?

[E36 HateR]

I thought we were talking about yoir car cj my bad

[abradic]

Wow. I kind of wish you didn't show me this haha. This just renewed my love for this setup. Although it's e85 they are very impressive numbers. I do hope to upgrade to the 92 trim since it would be so easy to do with all the other parts already in place but I may wait until my current blower fails before I do. I have far too many other things to invest in in the near future. Slight possibility that I may be able to later this year. I still have a smaller 80mm pulley that I have yet to put on and am in need of a new driveshaft(worn U-joints). With subzero temperatures here lately and no garage things my M3 hasn't received the attention she deserves. Thanks for posting though, I've been waiting years to see the 92 trim on an s52, very exciting

I don't know how much more whp E85 gets you over 93 pump, but you would think that on 93 pump you should be able to put down at least 475 whp. LOL, hopefully I'll be able to tempt you even more in 2 months (or 3 if winter decides to hang around longer), Im going to be on 93 pump.

that car is on a stock botttom e36 and oem headgasket
made 550whp uncorrected (real hp that it made that day. it was very cold out)

That blower just seems to put down much more power than the -81. I'm surprised that AA doesn't upgrade the E36 kit to the C38-92 with an optional 42 lb and 60 lb injector tune to support the various mod/setups people would have. Pushing that 500 whp boundary would definitely get more people wanting a centri.

[pbonsalb]

93 pump plus meth will not allow the sort of power that is possible with E85. You can run more boost and more timing with E85. A few of us have made over 450 rwhp on 93 pump plus meth, SAE on a Dynojet. I recommend a 60 lb tune if you are trying this, or watch your duty cycle closely. Since you cannot run as much timing on 93 pump plus meth, you have to run more boost. That can cause the blower to run over its limit or for the belt driving it to slip. The C38-92 flows less than a Vortech Si or T Trim (and less than the new Ti Trim) despite Rotrex's claims that it is equal, but should flow fine for this exercise. Good luck. I gave up on the centri at 463 rwhp and love my turbo at 609 rwhp.

[RK-Tunes]

I've done 48xwhp on just 93 on a standard RMS kit at 16ish psi.
SAE on a dyno jet with NO meth

On e85 it would be ~510-515 EASY