Rotrex Superchargers...blasphemy lol

[mean4g]

Ok first let me say I did do a search (most threads went off-topic), and I am not a newbie to DSMs or Evos either. So please no, "stick to turbo" flaming please.

Anyways...seems like a match made in heaven. Capable of making 600 WHP in the C38-92 version, will get positive boost around 2K, makes better midrange torque/power than other centrifugal superchargers, more reliable than other centrifugals (built for track racing), better transient and throttle response than turbocharged engines, reduces significant amounts of internal stress etc.

Only downside I see is the cost. Seen them around 2K for one, then you have to set-up mount brackets, pulleys, header, intercooler etc. So perhaps 3k-4k range for a full setup. About on par with a GTX or EFR setup with a quality tubular manifold manifold or so.

Thoughts? I just think it would be pretty cool to see an outside the box build like a 2.4L, 10 to 1, E85, Rotrex C38-92 @ 28 PSI..thats all.

 

[95talongirl]

The inherent problem with superchargers is the fact they take engine power to make power. Which is why they work so well on bigger displacement engines, which have more n/a power, than smaller engines that make most of their power in the upper end of the rpm range.

They work, I mean look at the first cobalt ss. However, turbos just suit the smaller engines better, since it just uses exhaust. Back to the cobalt example, it went turbo in 2009, and was a much more powerful car.

I would assume that if you built a higher compression engine with more baseline horsepower, maybe it would work better. But then you may be boost limited, too. By time you spend the money on an expensive supercharger and setting it up, a turbo could have gotten you there and then some. So I believe that is why we don't see as many small displacement supercharged applications vs. turbo.

 

[LandSpeed-DSM]

Turbos definitely take power from the engine to run as well..

I've had the opportunity to work on a couple Rotrex powered cars. They would definitely not be my first choice for any application. For starters they are expensive as hell. Then on the technical aspects..
http://www.rotrex.com/media/2422dbd.../PDF/Rotrex Technical Datasheet C38 Range_pdf

1.) The compressor map says it all, even their "big" C38-92 has a nearly 70mm inducer, but taps out at 82-83lbs/min. Worse.. it's at only 2.1PR. You're not going to get anywhere near that part of the map with anything under ~4L and it will still require you to rev the piss out of it to get there.

2.) It's pulley driven. You don't have full boost till redline, or a few hundred rpm before. You might make a few psi down low.. but it's basically linear from there on up.

3.) It's less efficient than almost any modern turbo of the same size, will definitely make less power and the turbo will at least give you a few thousand rpm of full boost. Probably won't cost 70% as much either.


4.) Changing pulleys to change boost.
Just my 2psi.

 

[mean4g]

Turbos definitely take power from the engine to run as well..

I've had the opportunity to work on a couple Rotrex powered cars. They would definitely not be my first choice for any application. For starters they are expensive as hell. Then on the technical aspects..
http://www.rotrex.com/media/2422dbd.../PDF/Rotrex Technical Datasheet C38 Range_pdf

So did you happen to drive those cars? Your thoughts and opinions about that? I am assuming not very impressed?

1.) The compressor map says it all, even their "big" C38-92 has a nearly 70mm inducer, but taps out at 82-83lbs/min. Worse.. it's at only 2.1PR. You're not going to get anywhere near that part of the map with anything under ~4L and it will still require you to rev the piss out of it to get there.

true. figured I would have to run it close to the 90K impeller speed, and 2.9PR ratio to get anywhere near its capable flow? I haven't plotted it, but figured it was possible. Recently I read a Honda K24 build made 591 WHP...yes a much more volumetric efficient engine than ours...but still impressive.

.) It's pulley driven. You don't have full boost till redline, or a few hundred rpm before. You might make a few psi down low.. but it's basically linear from there on up.

true.... but iI just remember in my 67 lb/min turbo/build my car was not responsive at all in lower RPM's. Figured this might be better?

.) It's less efficient than almost any modern turbo of the same size, will definitely make less power and the turbo will at least give you a few thousand rpm of full boost. Probably won't cost 70% as much either.


4.) Changing pulleys to change boost.
Just my 2psi.

yes I understand that the turbo will make more power...but with more lag overall. comparatively. Yes the cost is certainly the killer on this for sure. No doubt. Don't get me wrong I do love turbochargers and have had my fair share trying to find my happy medium (S259, 50 trim, 60 trim, 16g, and an HTA 68 etc). The problem is I never could. Loved the top end pull of an S259 at 30 psi, but hated the lag. However loved the street manners, boost response and fun factor of the HTA 68, but got bored with lack higher RPM power. Honestly I was never totally happy either way. . Just thinking of other crazy things.

Thanks for your input. If you got anymore thoughts please feel free to share.

 

[Steve93Talon]

Don't get me wrong I do love turbochargers and have had my fair share trying to find my happy medium (S259, 50 trim, 60 trim, 16g, and an HTA 68 etc). The problem is I never could. Loved the top end pull of an S259 at 30 psi, but hated the lag. However loved the street manners, boost response and fun factor of the HTA 68, but got bored with lack higher RPM power. Honestly I was never totally happy either way. . Just thinking of other crazy things.

Try the EFR 7163. Flows like the S259 and spools like the HTA68.

 

[delta448]

If you want response and low end, you might want to use a small positive displacement supercharger, not a centrifugal.

Here's some good reading material posted circa 2006-7:

http://www.dsmtuners.com/forums/newbie-forum/250586-supercharger-turbo-setup-3.html#post151102828

http://www.dsmtuners.com/forums/bolt-tech/253830-twincharger-v2-0-teaser-photos-inside.html

 

[Cdc1221]

Or why not run a compound turbo setup.

 

[LandSpeed-DSM]

So did you happen to drive those cars? Your thoughts and opinions about that? I am assuming not very impressed?

true. figured I would have to run it close to the 90K impeller speed, and 2.9PR ratio to get anywhere near its capable flow? I haven't plotted it, but figured it was possible. Recently I read a Honda K24 build made 591 WHP...yes a much more volumetric efficient engine than ours...but still impressive.

true.... but iI just remember in my 67 lb/min turbo/build my car was not responsive at all in lower RPM's. Figured this might be better?

yes I understand that the turbo will make more power...but with more lag overall. comparatively. Yes the cost is certainly the killer on this for sure. No doubt. Don't get me wrong I do love turbochargers and have had my fair share trying to find my happy medium (S259, 50 trim, 60 trim, 16g, and an HTA 68 etc). The problem is I never could. Loved the top end pull of an S259 at 30 psi, but hated the lag. However loved the street manners, boost response and fun factor of the HTA 68, but got bored with lack higher RPM power. Honestly I was never totally happy either way. . Just thinking of other crazy things.

Thanks for your input. If you got anymore thoughts please feel free to share.

Yes I did drive them. No I'm not impressed. They have applications where they make sense, but they are few.

I don't intend this to be rude, but you are 100% wrong about how these Rotrex units respond and build boost. It will be worse.

Having had an S200sx also before the 67mm I run now, if you think the 59mm Borg was laggy (whether or not it was due to your tune or other parts of your setup) you will despise a comparably sized Rotrex S/C.

Again the S/C is pulley driven. If you have a 20psi capable pulley and you build 1psi at 3k with 20psi by a 7k redline, you will be making around 10psi at 5k rpm.

I have posted screen shots on here of my HX52 making 30psi by 5k at part throttle.. an old tech turbo good for ~10lb/min more mind you.

Look once more at the map on that PDF I linked. Mass flow is a limit for potential not a guarantee of power. But if you don't have the air in the first place you can't make the power.

That's why this is an important distinction.

Trace left to right from 2.1PR.. That is the most this wheel will support. Running at 2.9PR, the right side of the map recedes back to the left considerably. That is the limit Because we don't have the displacement, even at 105% and 10000rpm to, we need boost to get the mass through.

No getting around that.

 

[mean4g]

Yes I did drive them. No I'm not impressed. They have applications where they make sense, but they are few.

I don't intend this to be rude, but you are 100% wrong about how these Rotrex units respond and build boost. It will be worse.

Having had an S200sx also before the 67mm I run now, if you think the 59mm Borg was laggy (whether or not it was due to your tune or other parts of your setup) you will despise a comparably sized Rotrex S/C.

Again the S/C is pulley driven. If you have a 20psi capable pulley and you build 1psi at 3k with 20psi by a 7k redline, you will be making around 10psi at 5k rpm.

I have posted screen shots on here of my HX52 making 30psi by 5k at part throttle.. an old tech turbo good for ~10lb/min more mind you.

Look once more at the map on that PDF I linked. Mass flow is a limit for potential not a guarantee of power. But if you don't have the air in the first place you can't make the power.

That's why this is an important distinction.

Trace left to right from 2.1PR.. That is the most this wheel will support. Running at 2.9PR, the right side of the map recedes back to the left considerably. That is the limit Because we don't have the displacement, even at 105% and 10000rpm to, we need boost to get the mass through.

No getting around that.

Thank you for your input. It makes sense perfectly. As far as my 59MM turbo setup. I was getting to about 20 psi about 4300-4400 or so in 3rd or 4th gear. Was still laggy to me, but thats all personal perception I suppose. I guess some people might consider that responsive.

Try the EFR 7163. Flows like the S259 and spools like the HTA68.

thanks for the input. I was actually looking at that turbo as well. Doesn't quite flow like an S259...but certainly a happy medium with amazing spool with their new mixed flow turbine wheel. This is the turbo I would choose I think.

If you want response and low end, you might want to use a small positive displacement supercharger, not a centrifugal.

Here's some good reading material posted circa 2006-7:

http://www.dsmtuners.com/forums/newbie-forum/250586-supercharger-turbo-setup-3.html#post151102828

http://www.dsmtuners.com/forums/bolt-tech/253830-twincharger-v2-0-teaser-photos-inside.html

thanks for the reading material. Yes I looked at the screws, and the roots type superchargers. Problem with those is the size of the units, fitting a 10-rib belt and pulleys between the frame rail and the engine, and power per cost isn't all that its cracked up to be. However the honda boys are setting up some impressive numbers on a reworked MP62 mounted on the front side of the block running through an intercooler etc.

Or why not run a compound turbo setup.

thanks for the input. I have seen a few of those builds here on the forum. Certainly open minded about using it, and they are pretty cool but honestly tentative on the complexity of the setup for a daily driver car.

 

[My1GLaser]

Try the T3 7 blade HX35. I hit 38 psi around 4600-4700 in 3rd. (It's probably at 25 psi by 3800-4k. I've logged 60lb/min and it pulls at the way to 8-8.5k nicely! It out spools my buddy's 20g hands down

E85 and lots of timing in the spool up range make a big difference! I've run the same turbo for 4 years and I'm still not bored. Brings a smile to my face every time it hits!

 

[Steve93Talon]

thanks for the input. I was actually looking at that turbo as well. Doesn't quite flow like an S259...but certainly a happy medium with amazing spool with their new mixed flow turbine wheel. This is the turbo I would choose I think.

They're both rated at 60 lb/min. I'm currently on an HTA68, and the 7163 will very likely be my next turbo.

 

[mean4g]

They're both rated at 60 lb/min. I'm currently on an HTA68, and the 7163 will very likely be my next turbo.

I was under the impression that the S259 ETT was a 67 lb/min compressor flow? Please correct me if I am wrong.


Yes I had the 68 HTA myself. I absolutely loved it..."spooled like a 16g, and pulled like a 50 trim" would be how I would describe it. However I did miss that rush of the 259 pull.


What about using the twin scroll IWG housings on the EFRs. Would just have to relocate the power steering/alternator to make it work as the housing is ridiculously long. However, it does make the setup very simplistic. My only concern is I have noticed the twin scroll housing is much smaller than the single scroll housing for the 7163. .85 vs .80 (substantially even smaller when you consider the cross section). Would be concerned with chocking it. I would like to a see a .90-1.00AR TS housing for that turbo.

Try the T3 7 blade HX35. I hit 38 psi around 4600-4700 in 3rd. (It's probably at 25 psi by 3800-4k. I've logged 60lb/min and it pulls at the way to 8-8.5k nicely! It out spools my buddy's 20g hands down

E85 and lots of timing in the spool up range make a big difference! I've run the same turbo for 4 years and I'm still not bored. Brings a smile to my face every time it hits!

Were you running 60 lb/min when you trapped 121 MPH?...numbers don't seem to add up. I am assuming you are running that in a twin scroll configuration?

 

[My1GLaser]

Were you running 60 lb/min when you trapped 121 MPH?...numbers don't seem to add up. I am assuming you are running that in a twin scroll configuration?

No, I ran that when I was running the .55 A/R BEP bolt-on housing at 26-27psi. (Don't recall the airflow) The highest it ever flowed with that setup was 54-55 lb/min but that was around 33-35 psi.

I run an open T3 Turbonetics manifold and the .70A/R BEP housing now. It reaches that airflow at about 36-37 psi.

 

[mean4g]

No, I ran that when I was running the .55 A/R BEP bolt-on housing at 26-27psi. (Don't recall the airflow) The highest it ever flowed with that setup was 54-55 lb/min but that was around 33-35 psi.

I run an open T3 Turbonetics manifold and the .70A/R BEP housing now. It reaches that airflow at about 36-37 psi.

Ok that makes more sense. Probably flowing mid 40 range at that time down the track. My trap speeds were 125-126 in the BEP .55 housing on the 259. So how come you haven't ran it since? Your car spools pretty well for it's setup much better than mine did. Although I do like the holsets. They are a great budget turbo and certainly better than the older T/GT turbos and are tough as all hell. However in my experience with them I haven't found them to spool as well as some claim and they take ridiculous amounts of boost to make good power (can be an issue on pump).

 

[My1GLaser]

I haven't gotten a good run in due to breaking drivetrain parts and having clutch issues. I broke a rear end and Shep stage 3 my last 2 times at the track. I can't afford to break it again cause I'm moving out of state soon, so I haven't been back!

The spool on this thing is ridiculous. I have aggressive timing in the spool up range and the exh cam is retarded a tooth. E85 makes a big difference too!

 

[mean4g]

I haven't gotten a good run in due to breaking drivetrain parts and having clutch issues. I broke a rear end and Shep stage 3 my last 2 times at the track. I can't afford to break it again cause I'm moving out of state soon, so I haven't been back!

The spool on this thing is ridiculous. I have aggressive timing in the spool up range and the exh cam is retarded a tooth. E85 makes a big difference too!

makes sense. Good luck, should be in the 10s somewhere.

 

[gofer]

Yes I had the 68 HTA myself. I absolutely loved it..."spooled like a 16g, and pulled like a 50 trim" would be how I would describe it. However I did miss that rush of the 259 pull.

What kind of airflow numbers are you logging with the HTA68?

 

[mean4g]

What kind of airflow numbers are you logging with the HTA68?

don't remember to be honest. It definitely pulled as hard as my old 50 trim.

I had many different setups on my Early Evo (my later evo was just the stock turbo with a 10.5). Evo 3 turbo (of course), 50 trim, 60 trim, S259, and the 68HTA. The 68 was by far and away the best street turbo I have ever run.