Rx-7 S/C

[mrmattyk]

I had an argument with my friend. He thinks supercharging his rx-7 will give him more torque (which it may) and have better gains than a turbo'd rotary. I disagree tottally, turbo all the way! It's a GEN 2, GX. Anyone want to add to this? I want to show him this thread after so dont hold back :D

[three.eighteen.]

ive never seen a s/c'ed rotary...pics??

[mrmattyk]

Neither have I, but he said he found a S/C for a rx7

[Glowrider]

That's the dumbest thing I've ever heard. Thousands of Puerto Ricans can't be wrong, turbo is the way. Besides, superchargers suck ass on small displacement engines, like the ones found in Rx-7's. Turbo's are much more efficient.

[dsm69]

what about turbo lag? each system has it pros and cons

[Si_FlyGuy]

Originally posted by Glowrider
Thousands of Puerto Ricans can't be wrong

:rofl: :rofl: :rofl:

[ecstasyracer]

Here's a pic of a badass first gen 7 thats super charged, and is a Calgary car by the way. Just thought I would give an example of a supercharged car.

But I totally agree though, turbo all the way. Way more potential. You don't see supercharged rotarys hitting 500+rwhp, just turboed ones.

[Glowrider]

what about turbo lag? each system has it pros and cons

A small shot of nitrous will cure that.

[ecstasyracer]

Originally posted by dsm69
what about turbo lag? each system has it pros and cons

Actually a ported rotary engine is very good at spooling a turbo.

[STI-Guy]

Is your friend a rich, old white man who decided to take a break from domestics to modify an import, 'cause it's what all the kids are doing now-a-days?

I think everybody (including my Puerto Rican homeboys) can agree with me when I say...

TURBO ALL THE WAY!!

[RiceCake]

Turbo for the Rx7, way more room to play with and way more impressive numbers :)

[Glowrider]

I like the feel of the way turbo's deliver power better too, as opposed to a supercharger.

[THREE40SEVEN]

A centrifical cant match a turbo.
I am currently drunk.

[buh_buh]

Originally posted by dsm69
what about turbo lag? each system has it pros and cons
well it is a twin turbo setup.
And plus, all the RX-7's power is down low. No power in the top end.

[Maxt]

Originally posted by buh_buh

well it is a twin turbo setup.
And plus, all the RX-7's power is down low. No power in the top end.

???????????
umm yeah..



Each has its own merits, turbo does not have the parasitic drag of supercharger, however, it does increase the back pressure on a motor, which is also not a great thing on a rotary, since it has no exhaust valves and large port overlap. One can minimize the effects of backpressure by running a really large exhaust housing, this frees up alot of HP, and lets you run higher boost without running into the breakpoint wall, where your exhaust backpressure meets your boost pressure and you stop making power, you'd be hard pressed to find most imports or even supras running t04's with anything large than a .84 a/r or .96 on the turbine side, I run a 1.15 a/r on my t04e, and maybe a 1.32 on my new motor.
The supercharger kits that are out there for the rotary, are all kind of half assed, half researched endeavours, that were pulled off the market for one reason or another, the camden kit, like the one that pic, would not use the factory efi, and therefore would not pass any kind of emissions testing, and because of its physical size and packaging, intercooling is not possible, so boost pressure is limited to about 7 psi, before detonation and thermal loading would destroy the motor. Roots superhcargers are only 50% efficient at best.
There are some paxton and nelson kits that were on the market, however the rev range of the rotary made pulley selection hard, alot people that bought those kits found the hard way they were overspeeding the supercharger if they drove the car anywhere near redline, and wanted any boost down low as well, one guy on the www, had some many problems with broken superchargers, cracked brackets and ripped belts, the centrif style supercharger can be intercooled, if there was a decent kit it would be ok for those looking for moderate boost levels.
The linear air flow of a roots supercharger is alot easier to gear the fueling and tuning to than a centrif style compressor which is no where near linear in its air flow. Tuning a turbo motor is a tricky endeavour, on a piston motor they will take a few pings without to much to worry about, on a rotary, its russian roulette, one ping=$$$$.
The nice thing about turbo's though, that you can turn them off with your foot, especially when using a larger one, you only tend to build boost when you are really on it, so you drive around in non turbo mode, and get non turbo gas mileage, you can't do that with a supercharger, it turns and pounds more air in all the time, I get better mileage out of my TII than it did stock, with programmable efi and large turbo, which is not bad for car that came with 186 factory rated hp and is presently in the 400+hp range at the wheels easily.
Oh yeah one more thing, nothing sounds quite like a rotary with an open wastegate, turbo all the way!...Maxt

[Glowrider]

No power in the top end.

Riiiight.

[buh_buh]

Originally posted by Glowrider


Riiiight.
Well I have a friend who had one, and that's what he said.
And I'm talking about a stock twin turbo here.

[Glowrider]

Depends on the car I guess. I know a couple guys with stock twin set ups. One of them is really strong down low, starts to die out about 4th gear, another one is weak down low, but after about 100 mph the thing is a beast, blink your eyes and you're at 160 all the sudden.

[buh_buh]

Originally posted by Glowrider
Depends on the car I guess. I know a couple guys with stock twin set ups. One of them is really strong down low, starts to die out about 4th gear, another one is weak down low, but after about 100 mph the thing is a beast, blink your eyes and you're at 160 all the sudden.
I was told the power dies off substantially after 2nd gear.
And I'm talking about a 3rd gen here.

[ecstasyracer]

Originally posted by buh_buh

I was told the power dies off substantially after 2nd gear.
And I'm talking about a 3rd gen here.

Riiiiight, thats why a stock 3rd gen has a top speed of 160mph.

[buh_buh]

Originally posted by ecstasyracer


Riiiiight, thats why a stock 3rd gen has a top speed of 160mph.
we're not talking about top speed.
And plus, I'm not saying it can't get there. I'm just saying it'll take a while to get there.:rolleyes:

[persid]

Uh, if anything, rotaries are famous for having no bottom end and crazy top (6000rpm+) end. I'm not sure where you got the idea that the top end sucks in these cars. They have no camshafts and thus the power curve linearly matches the rpms, or in other words, the faster the engine is spinning, the more power it's making (well, at least when it's properly opened up). I don't remember ever seeing a non-blown rotary that has trouble with the top end.


Oh yeah one more thing, nothing sounds quite like a rotary with an open wastegate, turbo all the way!
Ported N/A running at speeds turbos can only dream of, N/A all the way! ;)

[buh_buh]

top end as in speed, and not powerband.

[Joe Malms]

Originally posted by buh_buh

well it is a twin turbo setup.
And plus, all the RX-7's power is down low. No power in the top end.

Im gonna join max and glowrider on this one.
RIIIIIIIGHT...

[persid]

top end as in speed, and not powerband.
In a car with properly set up gearing, the top speed depends only on two things, top end power and aerodynamic efficiency. As the FD has a CD factor of .31-.32 (going from memory here, but it shouldn't be too far off), which is fairly good, having a bad 'top end' could only mean that it makes bad power at high rpms. And once again, this is far from the truth.

Now, if by 'top end' you meant that a supra running crazy boost would kick it's ass on a highway run, there's really not much point in having this discussion as it will obviously end in flames.

[STI-Guy]

This is just stupid. I guess all those sleek curves are just for show. :rolleyes:

The RX-7 is awesome at top speed. In fact, I think it holds the import record.

[Glowrider]

Check out Pettit Racing's Bonzai Rx-7...230+ mph

[buh_buh]

k whoa, that's just what I was told.
I'm not arguing or anything.
and I'm talking about stock guys, not a modded one.

[Maxt]

Rotaries, at least not 2 rotors, are not known for their low end power, they are pretty much mid range and up, the stock turbo's pull ok down low, but for the most part, you have to have some revs on to make the power, they do not lug well, they are not big block v-8's...
If you port them at all, you move the entire power range up in the scale..Maxt..

[persid]

Originally posted by buh_buh
k whoa, that's just what I was told.
I'm not arguing or anything.
and I'm talking about stock guys, not a modded one.
We're just trying to clear it up, because what you've been told doesn't seem to match any of our experiences. There's a reason why stock FDs don't hit a cut until beyond 8500rpm :)