hotroder

Hey I'm new here and have a question about putting a
vortech supercharger v-1 on my 85 rx7.
Has anybody done this?

813KR$

Call Atkins rotary, they are the main people that work with super chargers on rotaries. If anyone, they will know wassup.

mwatson184

Nobody has done it that i've seen. Atkins rotary does make a roots style supercharger kit, and that would probably be the easiest way to sc your car.

If you want to put the vortech on it will be a lot of fabrication/custom work. Not just with bolting on the supercharger (custom mounting) but also with fuel/intake system modifications (carb or fi). It would be a pretty nice project though.

Marques

mwatson184

Nobody has done it that i've seen. Atkins rotary does make a roots style supercharger kit, and that would probably be the easiest way to sc your car.

If you want to put the vortech on it will be a lot of fabrication/custom work. Not just with bolting on the supercharger (custom mounting) but also with fuel/intake system modifications (carb or fi). It would be a pretty nice project though.

Marques

web777

Nelson superchargers used to have a kit for 86-91 7's. I don't think they are around anymore.

rynberg

It's worthless putting a centrifugal blower on a rotary engine, because a centrifugal blower only works in the mid to upper rpm, where a rotary makes it's power anyway. Even worse, the centrifugal blower is parasitic in the low rpm range where it's not producing useful boost so you LOSE low-end power. That's why people use roots-blower types, which make full boost at low rpm.

I really don't understand why companies manufacture centrifugal blowers for cars like the NSX, S2000, etc. Seems incredibly stupid to me.

web777

There are 2 schools of thought on this. Your saying the a SC should be boost up the power were the engine needs it most (low RPM). Others think it should boost more power in the engine's powerband. I personally like the latter of the 2.

Evil Aviator

A centrifugal supercharger has a very linear boost profile, which makes driving the car much easier. It does not have a "disconnected" feel like a turbocharger, but yields the same compression efficiency, which is far superior to the horrible efficiency of a Roots blower. This allows for better fuel consumption, more power at a given boost level or fuel flow level, and a better detonation threshold (ie more boost is possible). Also, a centrifugal supercharger can be easily placed in various positions around the engine for clearance, and it is easily intercooled unlike a Roots blower. Sure, the centrifugal supercharger will dyno the steepest powerband of any type of supercharger at a given max boost pressure, but sometimes driveability is more important than a flat powerband. To each his own.

BTW, only the Roots supercharger is technically a "blower", while the centrifugal (including turbochargers) and Lysholm superchargers are compressors.

Usually a turbocharger is chosen for #2. The centrifugal supercharger usually only makes max boost around redline, and would only be at about half boost around 4000rpm where most turbochargers would have already reached their max boost.

rynberg

Your comments above are the reasons I don't feel a centrifugal supercharger is a good choice for a small engine with poor low-end torque.

Hell, look at some of the Mustang s/c packages, they aren't that much faster than the stock Stang because the centrifugal s/c actually makes less hp across the low to mid-rpm range and only makes extra hp at the very top of the band.

As far as efficiency goes, all s/c are bad compared to turbos. The s/c on the Mercedes-Benz AMG 5.5L V8 takes 100 hp to drive it at all full output.

mwatson184

^that depends on what you mean by efficiency. If you are looking at it as power given compared to power taken then alright. He was talking about the actually efficiency of compressing the air and the heat that it creates.

gerbraldy

cool

rotarygod

iTrader: (1)

There are so many people out there running turbos that are way too small on the exhaust side that they are very restictive and hurt power when not under boost. They also require several psi of boost just to make up for the losses before they even get a gain. Now we are talking about less power when not under boost than even stock. Look at the gains a good header system can get on a nonturbo rotary. Now consider a supercharged rotary that has a good header system. Right off the bat is is making lots more power when not under boost than the turbocharged car. Sure it takes power from the crank but it also doesn't kill flow and tuning on the exhaust side.

A properly designed turbo system will not have these problems as their exhaust housings will be big enough to have adequate flow but then they will lag a little worse and not get full power until later.

A turbo will get a little intake heating just from the fact that heat will transfer through the turbo itself and warm up the intake charge. This can't happen on a supercharger.

A proper turbo will also heat up the air less when under boost than most superchargers will and regardless of exhaust restriction still generally make more power.

I am not arguing for superchargers or against them. I am merely stating some facts that many do not take into account between turbos and superchargers. Too many people like to run turbos that are too small and too restrictive but then just spin them faster. Others like to run a turbo that is not designed for the application they intend to use it for.

In the same fashion, superchargers are typically not sized properly for the rotary. The Paxton supercharger for the 2nd gens was inadequately sized and couldn't flow enough air so it was restricted to lower boost levels so it would not overspin at high rpms. The Atkin's 5" supercharger is too small. Their 7" supercharger is good for about 6 psi or so. It can't flow enough air efficiently enough to run more boost. It would take a much larger unit to run higher boost.

Superchargers are just like turbochargers in that they need to be sized properly for the application. They do have some good potential but as others have pointed out some are better than others in certain areas.

Just so no one thinks I am insulting turbos (I'm not), I don't own a supercharged rotary. I drive a turbo rotary.

80-CU.IN.T

That was exceedingly well said.
A properly intercooled supercharger ( Of modern design ) will produce close to the same peak HP as a turbo ( Street application.) Disadvantages - crank driven, PIA to adjust boost pressure, most units are heavy. Advantages - NO LAG and a very predictable power curve.