Supercharged or Turbo
 

Hi, there

I am wondering should I put a supercharge into my 8 instead of a turbo one.
The matter of putting a supercharge instead of a turbo is, I heard so much 8 or 7 asked to rebuild after installing a turbo charge a period of time. Therefore I did some research online with supercharged rotary, but there is not much data of a supercharged RX 8.
Therefore I would need some ideas from here, no matter, the cons and pros. Besides, I have no idea how much horse power a stock rotary with supercharged can produce. Can somebody please help me?
Thanks.

Phil's petit supercharged RX8 auto blew up last month.

how long did it install it?
thought supercharge is more reliable than the turbos...
my opinion, no offense to turbos

turbos cannot take offense - they are inanimate objects

both push more air into the engine, so you inject more fuel and you end up with more power.

if you're talking about engine reliability, then considering either one more reliable than the other is idiotic.

on the other hand, right now the lowest power gains from any FI kit comes from the SC camp. So with that said, you might consider the SC's more reliable since you get the least amount of gain with them. You could also just turn down the boost on a turbo kit to get the same effect.

Here's my point: 8-9 PSI on a Pettit SC = ~190 torque peak.

8-9 PSI on MM's 3071R turbo = ~250 torque peak.

Stock torque is in the 130 range, so you have a baseline.

^ Great post. Curious, would you attribute reliability to be more of a function with Net Gain or with level of PSI?

in reality psi doesn't mean anything. that same psi on a greddy turbo would produce 210 torque. It's all about flow rates.

reliability really doesn't go hand in hand with power either, unless you're pushing the car to the edge - in which case you may just randomly pop the engine.

if your power levels are somewhere in the 280-380 whp range with a good tune, maybe meth or something, you have decent cooling and all the other supporting mods, you should be doing well and not run into trouble. Your engine may wear out sooner with more power, but how much less is unknown.

I actually pretty agree mysql's statement.
But I am just wondering, as I know a turbo charger would produce high temperature whenever it starts working, even with a good inter-cooler, the engine would still suffer in a high temperature and eventually blow up easily.
But with a supercharge it's different case. (I don't really know much about supercharge, therefore I need someone to tell me what's the cons and pros of it.)
If I am wrong please correct me :-D

turbo doesn't produce high temp just by being a turbo. The heat generated is a product of the air being compressed. Any FI that compresses air (which includes superchargers) will generate heat. That's why we have the intercooler before the intake manifold, so we can cool down the air before it goes into the engine.

if you generate low amounts of pressure, you may not need an intercooler at all because you aren't going to compress the air as much and thus don't generate as much heat.

You should see the post by Rx8thunder

https://www.rx8club.com/canada-forum-35/seriously-considering-turbo-156504/

Same topic!

With our cars, you are better off going with a Turbo. A Supercharger needs to run off of the engines torque, and thus takes away power. That is why it makes less power at the same PSI.

As mysql stated, you would gain only 60lbs-ft. With all of the added weight a supercharger creates, this isn't a huge gain. Also, the weight you add is all in front of the front axle and throws off the balance of the car (which is important in our cars).

A turbo also adds weight, but can produce more power.

A N/A Rotary build up is the most expensive route, but the best for our cars. Talk to Al (#84 Racing) for more details on this

weight isn't a big deal. I don't think that's a pro or con for either tc or sc.

a sc does have more moving parts, belts and whatnot. a turbo just sits in the exhaust and spins around. It's a more efficient system - no one can deny this.

The only PRO for a SC that I can see is that you get your power instantly when you put your foot down. HOWEVER that is easily offset by a properly sized turbo. Jeff's 3071R can provide 12 psi at 2,800 rpm. Which means power is virtually instant unless you're doing something stupid like shifting into 5th gear at idle and then flooring it. Just regular driving usually means you're in the 3500 rpm range. So no big deal.

Ultimately if you want to compare them side by side, look at the dyno comparison thread. Even at the low rpm where the SC is supposed to rule, you'll see it generates less power.

If someone made a SC kit with a different type of SC, or higher PSI pulleys, these results might not be as badly skewed in favor of the turbo. But right now that's how it stands, and has stood for the entire life of the RX-8.

I know the SC guys are going to think I'm a hater. But don't look at it as "your side vs my side", instead look at the facts. I'm just stating them as plainly as I can.

In the end, a SC is a gain over stock. It will be fun to drive. At the same time, I would gladly promote the 3071R kit over the greddy kit (even though they are both turbos) because one is better than the other. Any FI is good. Some are more good than others.

To most, it's about what is the max power can we safely put down? What is the $/hp ratio? These all point to TC.

Thanks for the sharing, I like the way you both talk about, it sees more realistic data from it (no offense).

Alright, let's forget about the horse power. Let's look into the tolerance of a rotary engine would suffer, both in the turbo charge and the S/C. Comparing with the other brand motor, I believe rotary is one of the smallest and coldest engine, however, as it is a 1.3L engine, I am pretty worry about if we boost it up, the engine will eventually blow up. Besides, the 8's rotary is not come with Turbo like the 7's did, that's a point that I concern, why would mazda made a 7 with turbo rotary stock engine, but not the 8. I am not trying to challenge but this is the question I always wanna ask.
Correct me if I am wrong, and thanks for the share.

Remember the twin turbo rx-7 had reliability issues and it was commonly referred to as the "rats next" because of all the vacuum tubes.

The Rx-8 in NA makes almost as much power as the twin turbo Rx-7. They wanted a reliable rotary setup. Also less issues with emissions going without the turbo.

^+1 - its all about personal preferance. personally I like them both quite a bit.....I really am not sure which way I would go?

The truth be know, my engine never blew up just lost compression and that was due to excessive heat (not the s/c). S/C or turbo is a personal preference thing. I prefer s/c others like the turbo.

can supercharged passion emissions/smog? someone told me theres a carb sticker you put on that is guarenteed to pass and not illegal to install

Of course it will. FI introduces more air (at higher pressure) which facilitates a higher fuel flow rate, but the hydrocarbon emissions are still proportional.

Thank you, mysql, for sharing this summary. I didn't expect this thread to provide that level of experience, and I am thoroughly enjoying this read.
I really appreciate the presentation. I think what I'm saying more than anything is, "I'm really enjoying listening to the people on this thread".
Thank you for bringing us this thread Millchan!

To my knowledge there is not a s/c or t/c that is certified in the State of California or Nevada. They will not pass a smog test unless you are a talented tuner or have friends.