rx7w/yaw

iTrader: (1)

Just a few questions on superchargers on N/a motor.

After battling the thought of going turbo and doing a TII swap I just thought why not supercharge. I actually thought about the paxton style (looks like the cold side of a turbo but a pulley instead of the hot side). Besides the cost and moan n groaning about the parasitic effect why is nobody doing this. What needs to be done?

Would supercharging an N/a be more reasonable that a TII or reasonable on any 13b rotary?

What kind of supporting fuel mods would be needed?

Since I removed power steering I could mount it there and run a v-mounted intercooler but this come back to the MAF again what mods to do away with or make it function.

Again this is just a curiosity kind of post and I just want to see how feesable this idea really is. I could get ahold of a paxton anytime for a reasonable price but not if its just gunna collect dust.

RotaryEvolution

iTrader: (30)

generally costs more than a basic turbo swap after it's all said and done, easier to turbo as you can piece together a stock turbo set and run the car on the stock turbo fuel system and turbo ECU, AFM, pressure sensor, etc.

a supercharger requires a standalone and tuning as well as the upgraded fuel system components and supercharger itself, and depending on what supercharger a fair amount of fabrication work.

turbos are more rotary friendly because they improve upon the higher end of the power band where a supercharger usually helps the low end response but chokes up in these motors on the high end. they will still help the power throughout but not as well as a turbocharger can.

SilHaro

iTrader: (2)

I'm no expert.

From what I understand though, the 13B doesn't make enough torque to fully utilize the low-end benefits of the supercharger. Also, Rotaries have so much excess exhaust gas that it would kind of be a shame to not slap a turbocharger on it.

AGreen

iTrader: (11)

Superchargers are cool, no doubt. But it's seriously a lot of money compared to turbocharging it. You can do a turbocharger on your car with relatively little money, just look at what Aaron cake did.

http://aaroncake.net/RX-7/naturbo.htm


Keep in mind that you don't need to do everything he did. A front mount intercooler kit cost me on ebay $200, which gave me essentially everything I needed. I'm pretty sure that a turbo throttle body elbow will bolt right on to the NA throttle body, which can be had for a song and dance. After that, you'll need some larger injectors (just get some stock TII 550's) and the TII ecu (or even an 88 convertible one, which runs the TII code as well). Then a TII AFM, boost sensor, and fuel pump and you should be in business. Total it all up or get a good package deal from someone parting one out, and it'll be SIGNIFICANTLY less money than a supercharger would be. And you'll be set up for making more power. The best thing you can do with a supercharger is change the pulley.


****the above list is probably not all-inclusive, and you may need a couple other small things I may have accidentally left out***

rx7w/yaw

iTrader: (1)

I would think that the supercharger would benefit in torque due to it building/keeping pressure even during an idle. I may be wrong Im know expert either its just a thought.

Karack: I figured it would come to upgraded fuel and ecu setup, but you make a great point the way rotaries fuel system works would "choke" the rotary when the secondaries kick in. afrs would change and almost dilute the purpose of having the s/c.... hmmm

thx for the responses I think that this idea has been foiled.

jerd_hambone

I don't think it has so much to do with the fuel setup as it does with the engine characteristics.

With a rotary, the supercharger would help with bottom end, but a turbo best utilizes the rotarys top end characteristics. Let's face it, the rotary is not a torque monster in the lower rpm range.

Evil Aviator

Belt-driven centrifugal superchargers do not produce max boost until engine redline, and up until that point they only produce boost at the square of engine rpm. Turbine-driven centrifugal superchargers (aka turbos) will produce boost as fast as the exhaust gas can drive the turbine, will hit max boost as soon as they can, and the boost will stay there all the way up to engine redline if the turbo is properly matched to the engine.

Since boost produces torque, the centrifugal supercharger would totally suck if you wanted low-end torque. On the good side, the lack of low-end torque makes the car easier to drive in slippery conditions or when driven by a novice who would have trouble with a turbo kicking in quickly.

The 13B works great with a supercharger.

I agree. Also, a turbine soaks up a lot of that excess exhaust that would otherwise end up as noise, which is an important factor for street cars.

jerd_hambone

I stand corrected! Haha

Evil Aviator

Your statement is correct with respect to a Roots type of supercharger, not a belt-driven centrifugal type of supercharger. This is actually a common misconception, and of course the centrifugal supercharger vendors do their best to hide this fact. The OP was also under this misconception, which probably would have resulted in him thinking that there was something wrong with the supercharger had he spent the time and money on this project for almost no change in low-end torque, lol.

RotaryEvolution

iTrader: (30)

better idea is to do both, best of both worlds! still waiting for some time to do my compound twin charged setup..

imagine getting some actual low end response with instantaneous boost from the turbo.... mmmmm

swilson@assetworks.com

iTrader: (13)

Speaking as a former owner of a supercharged NA (now being converted to a turbo configuration) the Nelson/Paxton SC kit for the NA 13B, with necessary fuel system and clutch upgrades can make about 200 rear wheel h.p. in a street configuration. This is about the same as the turbo II with a few "relatively inexpensive" upgrades.

It is important to keep in mind that the NA trans will be a week link once you start to push more HP through it. I don't drag race and the trans in my S5 vert went boom after a couple of years of "spirited driving".