RMS supercharger

[rayztoy]

I'm thinking about purchasingthe RMS supercharger Stage 1. Does anybody have this setup, if so, how do you like it? Any software issues, etc? Thanks. Ray

[Ryan]

I just thought that right quick I should remind everyone about zero tolerence We all know what happened last tim RMS was brought up. Anyways. I think BJ (e36m3) has an RMS setup. Checkout August? COTM.

[Samir]

You should drive a supercharged BMW before you make the purchase, so you can get a feel for the power curve of a centrifugal SC.

[poohlvhun]

Can you please enlighten me on this?
So how does the power curve differ than that of a NA car?
I thought sc gives a linear curve while turbos tend to spike in mid rpms. I have a picture in my mind that has a sc power curve similar to that of a NA but just moved up about 100hp. Is that not correct?

cheers.

[Samir]

Originally posted by poohlvhun
Can you please enlighten me on this?
So how does the power curve differ than that of a NA car?
I thought sc gives a linear curve while turbos tend to spike in mid rpms. I have a picture in my mind that has a sc power curve similar to that of a NA but just moved up about 100hp. Is that not correct?

cheers.

You're somewhat right. The centrifugal SC curve will look virtually identical to the stock motor's until about 4000RPMs, where it gradually rises to about 100HP above the stock motor's peak HP (for a 2.5-3.0 L 6 pot). A screwtype SC and turbo will have completely different power curves, compared to a centrifugal SC. Since the screwtype hits max boost by 2000 RPMs, the entire power curve will shift with torque seeing the largest gains in the lower powerband. A turbo curve will be similiar to a screwtype...depending on what type of compressor is used. Obviously a T-88 will produce nothing below 4000 RPMs, and then see a huge spike in torque/HP afterwards.

Boost Chart of Screwtype SC

[poohlvhun]

Thanks! It did not cross my mind that there were several different types of sc.

cheers.

[rayztoy]

Thanks guys for your replys, most helpful, especially Samir's post showing graph. Ray

[nicholas]

I bought it used off a friend and just had it installed last week. I am having some problems with it. My car is running very rich right now. We dynoed it just after the install and it only made 294rwhp. The same set-up made 320rwhp in my friend's car. The only difference between the two cars is that his is a 98 and mine a 96 and the software(i purchased the software from RMS, and it is supposedly the same software as in my friend's car). Their hardware is good. The software? If you do get the RMS setup, have them tune your software on the dyno. I have attached two dyno runs from my car. Run #2=294.8, Run #3=278.8.

[nicholas]