Different pulley sizes for c30-94 Rotrex...
 

All I'm finding is an old bimmerworld forum thread that mentions wheel2wheel selling 8 rib rotrex pulleys of different diameters.

I'm looking for a few different diameters, 90mm 100mm... maybe larger, idk. The pulley my C30-94 kit comes with is a 80mm, which is like 13psi at 7000rpm (at 675cfm) I'm pretty sure I'd blow something up at that level.

Run a wastegate on the manifold. Bleed excess boost at higher rpm.

what makes you think 13psi boost will automatically blow your engine

I read about that. I don't think I want to do that. Even if I did use the wastegate to limit boost, I'd still need a larger pulley. I don't see the sense in making the blower rotate close to its max rpm just to bleed it to 6-8psi.

So that you can make more boost lower down?

It's 13psi at 675 cfm... that's literally the max rotrex rpm at 7200 engine rpm? I'd rather try lower boost first. I'm not ready to commit more money for a built engine yet.

ok I'll dumb it down:

why do you think 13psi of boost at redline means blown engine?

Do research on Rotrex systems until you can see the sense in making the blower rotate as fast as possible at all times.

it likely won't even make 13psi if you cap it at 7, and if you run low timing and free flowing exhaust it won't be any harder (IMHO) on it than a 10psi turbo setup, aaaand there are many here making 10-13 on turbo setups on 01 unopened engines.

what I'm saying is you're overthinking this and should focus on more important things ;)

THIS THIS THIS.

Run the booost, don't worry about limiting boost, that's not the problem you need to solve. Tune it safe and let the boost flow, I ran 17 pounds on a stock 99 motor for a year with a GT3271 on pump gas, it did it. Just tune it safe. 13 pounds at redline is nothing, you will be fine. In fact I'd run more. Wastegate setup to regulate boost on a SC, I've designed and built one before. I would not recommend it.

You'll work the SC harder ,make more heat, and make more boost at lower RPMs, and need a heavy bypass system in place. I did this, it sucked.

Oh god. The horror. Boost at low rpms!?!? That sounds horrible.

Haha, ok, then I still need to find a place that sells the pulleys, if I'm to make more boost at redline lol.

All the boost, none of the timings...

Just as an fyi, the C30-94 outflows a EFR 6758 by 70 cfm...

I'm gonna punch you if you interchange pressure and flow again

Look what I found...

Underdog Racing Development

Will these work, even though they are 8 rib?

And the 7163 outflows the C30-94 by 100+cfm. The comparison is irrelevant to this thread, though.

^does vlad get to punch you? lol

I only brought it up because he asked me why I thought 13psi was a concern to the stock engine. I figured since it flows more than a turbo that has wrecked stock engines at less boost, it might be a safe thing to run less boost?

But idk.

The difference is the Rotrex will be making max HP at max RPM so torque is still low, vs the turbo which will be making max HP at less revs = more torque. As long as you don't exceed around 260ft lbs on the stock internals you should be right, which is around 360hp @ 7200. I don't think the C30-94 will get there on a stock engine... might be close.

Thanks Madjak.

I just got off the phone with Gary at Trackdogracing, he was very surprised I went with the c30-94 blower, on a stock engine. He was adamant about me not going over 7000rpm, even with the 95mm pulley (which I just bought from him) and very retarded timing. He was saying the c30-94 just flows too much for the stock rods at high rpms, and to actually maybe go even lower than 7000rpm for my redline.

I'm at 8000ft elevation, so I don't think I'll have a problem, at least not right away, but that altitude adjustment better be spot on, and have more retarded timing as I go lower in elevation.

So now I'm scared, and sad that I spent 3400 on a rotrex kit that I'm not using most of the parts from, on a rotrex that is too big? :/

If you don't do your research before spending money, you'll always spend more.

So Gary is finally selling his Rotrex kit? $3400 got you what parts exacty?

I think the C30-94 should be fine on a stock engine as long as you get a good tune. It's what I would run... though it's not something you can just slap on and forget about. If you are hitting too much power then you can throttle the Rotrex back by either dropping a restrictor into the intake which will limit peak boost / power, or install a recirc / BOV to vent the boost. Either way it's something I would do after you've got it on a dyno and had a play. Given the turbo power some people are running on stock engines, the Rotrex should be far more forgiving to stock rods and stock transmissions as it's power curve will be more linear.

And you did that while you are active in a forum that's called miataturbo?
Blasphemy.

The whole Kraftwerks c30-94 kit... except he didn't include the injectors or fuel module, which I was going to sell. And the piping looks used.. .but I'm not using it either.

And much to my surprise, the blower came with a 105mm pulley lol. so extra safe.

Wait what? You got a Kraftwerks kit from TDR?

by heavy bypass system you meant wastegate, right? why did it suck then? I've been reading post where ppl recommand it ..

well aside from setting up a wastegate, is there another way to restrict boost at higher rpms?

A bypass system/wastegate, yes. It explained why it sucked in my post you quoted. More heat, working SC harder, more weight, more complexity, less reliability. I would guess those recommending it have no real world experience with it, I do.

A restrictor will restrict boost at high RPM, that's a common approach that's simpler/lighter/easier/more reliable.

I wish I could end up with the mods you describe!
My first choice was the Trackspeed Turbo kit but after waiting for many months it is still not all there so I turned to the TDR Rotrex. I asked Gary about some combination of restrictor - pulleys - bov but he said that he can't (won't ?) help with any of that, "his kit comes only one way" and I guess that's that.
I want to move the torque curve down and forfeit top end HP on my stock 1.8 but the Rotrex landscape confuses me.

Trust me, TDR kits are quality.

Don't complicate the install. His kits (the street version kits) are for an otherwise stock engine. Oh I keep forgetting they don't come with good engine management. Just get a megasquirt from Brainiack. or whatever pnp ms you can find for your car.