I've been looking into an M90 for my RX-7 because turbos are too laggy for the motorsports I compete in.

I *have* an M62, but it's juuuust too small...

 

well considering I don't have a boosted car since this is the NA section I'm already getting passed by turbos, old news.

 

I own a small company that makes automotive parts, so when I make something for personal use I design it in such a way that I can mass produce the parts if I choose

I do get your point though.


From a drivability stand point a blower is a better fit for the rotary because they are most efficient where the engine has low VE and least efficient at peak torque. This does two things, it gives the rotary the one thing it lacks .... low end grunt. Because the blower is less efficient at higher engine VE you are less likely to blow things up.

Supercharging a car is harder then turbocharging for the average person. Fabricating a turbo header and some charge pipes is pretty simple and most of the parts are available from various places. To supercharge a a car you need hard to find flanges, potentially custom pulley's and well made brackets to mount the blower. For the average backyard fabricator this is much harder to do.

A few notes about the M90 from a Thunderbird. It fits perfectly on top of the engine (if you move the alt) and leaves about 3 inches between the inlet and firewall. Once a TB or piping is on there it'll be a tight fit but it works. You can buy better bearings for the blower and happily spin them higher (20kish) as long as you manage you intake temps properly.

 

Clearly all the 'superchargers suck' brigade have never ACTUALLY driven even a HALF decent supercharged car, rotor or piston. THEY ROCK!

Yes, more this, more that... less this, less that... whatever.

Supercharged cars are about the WAY they drive, not the number on the top of a sheet of paper.

I can't believe we have to explain this to people...

I drive a turbo car every day, it makes HEAPS of grunt and uses very little fuel. It also cost me very little to set up. It is perfect for what I use it for.

BUT, and it is a big BUT, there is no way in hell that it is NICER to drive, in a spirited fashion, THAN (for all you people who use THEN) a well setup up supercharged equivalent. It just so happens that a close friend of mine actually has the same engine as me but WITH a supercharger on his... mine wins in a drag race, but his is AT LEAST as much fun to drive!!! oh, and cost him no more to build.

For all those who haven't driven one, do yourself a favour and get off here and try one out - as Ferris would say, It is so choice.

Oh, and rotarygod, you may be interested in this, my current project is a modern twin-screw type blower on a rotary containing ports that have been designed with supercharging in mind. I'll be sure to post results.

 

^ Gordon, was it you Im thinking of that said you had thoughts of supercharging your 20B? If so, any plans to go through with that? As I mentioned in a previous post, its something Ive always wanted to try, but not sure if I have the funds/patience to tackle the project myself.

 

Well, a bridgeported one, anyway. I got sick and tired of the street port step-like torque curve, where it's wait... wait... waaaait... OKAY HERE IT IS! power delivery.

Even with only a half bridge, the torque curve is flat with a capital F, but it's still plenty livable on the street. And some of us worship false idles

Remember, though, everyone said that a half-bridge would get you the headaches of a bridge port without the power, and so wasn't worth the bother...

 

1st off, regarding the username.. yea I made it when I was like 15 and thought it was cool. Now I admit its a bit annoying, but its a bit late to change it now being that its been what Ive gone by for the past decade (wow makes me feel old..).

I think we have alot in common in what we want out of our cars, though I will be getting slightly more radical than you as far as engine induction ( I will be running ITBs, but staying with sideports). The thought has crossed my mind to try and fab up a twin screw charger such as a kenne belle unit, but I worry about failure and lots of lost time/money. I do think it would make for an amazing combination though even at moderate boost levels. Im not trying to make a HP monster, just something respectable and a blast to drive.

But anyway, yea Id love to get a look at your car sometime being that were somewhat local. I really, really hope that my car will be up and running next year in time for the next meet out at your place, but its going to be cutting it close. I'm still gathering parts, and the project has taken a back seat lately as I just purchased a home and got all moved in recently. Hopefully in the beginning of next year progress will really pick up and Ill definitely be posting my build thread up when that time comes.

 

Well I guess I will make a post here. I will try not to discuss turbos being superior here because the OP didn't ask ok. I have owned supercharged & turbocharged vehicles, I currently have both a turbo & a supercharged rotary. I belong to the goup running prehistoric boost adders. My Camden charged race ported 13BT FC3S, has been a fun & responsive car to own. Yes I always have more room to make more power in my turbo 13BT, but I'm happy with the cars performance. I tried to fix one of the issues of the roots type blowers of creating lots of heat, by using a sandwhich plate style water to air aftercooler. I plan on having a new cooler with dry ice compartments on the sides for added cooling. If your not shooting for big power numbers & find a decently priced kit jump on it IMO. BTW I seen someone had said Pro guys don't run supercharged rotaries! That is a incorrect statement, in Aus I have seen a few centrifugal dragcars & a few 6-71 set up dragcars running very nice times & big power. Good luck with your build if you decide a blower is the way to go.

 

Every street port I've ever had, and even the 6-ports which are basically factory huge street ports, have a torque jump at about 5500rpm. My ex-street port TII block showed on the dyno that it made roughly 110ft-lb at the wheels, and then like a switch it gained ten more ft-lb at that RPM. 10ft-lb doesn't seem like all that much but it was definitely noticable when driving. On course it was frustrating, because so much time is spent under that speed.

The half-bridge made over 120 at the wheels at 3200. Peak was still around 6000, but there was a lot more below that point, and the torque curve was a curve instead of a shallow staircase.

Sadly, I was inspecting the remains of the half-bridge and the rear side housing is unusable. Two of the corner and one of the side seal springs were flattened, the oil O-rings were junk, but I didn't think to look at the housing until I was clearancing the side seals and noticed metal transfer on the rotor. Yup... there is significant wear, far too much to be lapped out. So it looks like I'm going to be going back to 6-port stuff again :cry: Probably with a very-early-opening port and beveled rotors, just because I haven't done that before. Possibly with a blower to get the torque back.

 

OH NO! Don't do that - Blowers suck...

 

^technically they blow!

 

C'mon Gordon, no credit for me - that was team work...

 

I think thats the first time that I've seen rotarygod post a joke on here! I think he's getting soft on us :P

 

WOW! lots of post!! and alot of Reading! i have step out for some leisure time, but im back now.

back to business.
Ok let start off... Right now yes im running N/A 5speed tranny with stock clutch Rb alm. flywheel and i have gtus diff 4:33 and hopefully that can run good with a supercharger. As far ECU im looking into the Rtek 2.0 but still need some reasearch to see if capable with S/C.
Yes the car is a daily driver, and why is it? Becuase i enjoy driving the rotary taking a nice drive on the weekends and early to work, but not the daily LA bumper to bumper traffic( thats where i enjoy my stock clutch, street killed me driving in traffic but i might have to go back to street clutch for AutoX). The car is going to be use for and run in AutoX. car handles great with RA-1 sticky tires and coilover etc of suspenion work on the car. ran great. But as we all know we want just a little more power/torque. As far NOS thanks for the thought =). but we continue.
It"ll be nice if i gain 400hp etc etc out of a supercharge, but i just i'm looking for decent number yeah 225-255hp with torque sounds good, is it capable dont know yet. Im not looking for 400hp and horrible street drive. im just trying to get the best of both worlds.
Some horse power, some torque and yes even if possible good gas MPG. I run 460 and i have with my setup now i can actually shift aroudn 3000rpm with no problem and next gear pulls good. old setup i had to shift atleast over 4000rpm. with shift under 3800rpm im only using primary (wasting less gas) and im looking goona run 550 on secoundary. Im not a street racer to drive like a speed demon on the street i'll leave that for the track. but at times now and then i do enjoy a nice high rpm getting on the freeway ramp on freeway to feel the fun rotary!.
great feed back from you all!

update:
Exhasut system- as far i was looking into getting the true-dual sytem from RB that gives the best power for the NA but since im going Supercharge im looking into running a NA RB street header to collector to a RB turbo REV II system from pre-silencer back. looking to have the pre-silencer flange match to fit the header flange.

 

I don't make jokes. I make technical corrections!

 

Two turbos and a supercharger? This is a rocketship, not a car

 

Well since is a supercharger thread ... i though you guys might be interested in following my thread with my rotrex supercharger:

https://www.rx7club.com/build-threads-293/well-rotrex-supercharger-has-been-ordered-921875/

 

I didn't see that thread...very interested. I'm very much contemplating selling my turbo equipment - Precision 6265 and Tial 44mm - to go this route instead. Looks like your goals are more modest than mine as I was thinking I would get the C38-81.

Very cool to see people trying new things.

 

well with the kits ill be making, you'll be able to fit whichever charger

 

good god yes