Okay, we all know that the Renesis Rotary doesn't have the best MPG in the world. But how much worse does it get with Turbo?

I've heard some people say that a turbo can actually HELP your MPG because of how effecient it is. Is this possible?

 

The turbo RX-8 gets -6 mpg.

 

Well that was very blunt

Any data to back that up?

 

It goes down a bit.

I took off my cat and threw the downpipe on there, and it seems to be about where it was before the turbo

 

I've seen quite a few go 5-10 MPG below what they were before FI.

 

I get about 15 miles less per tank than I did before the turbo.

So if I didn't go into boost at all, I'd guess the mileage would be very similar to non turbo.


rotarygod estimates about 1 mpg less than stock, which I'd say is pretty accurate. It all depends on how you drive. If you're going on the highway and staying in boost non stop, or boosting at every stop light, your economy will be greately decreased.

 

Good point. But if you're the kinda person going with DIY FI, you are going to drive your car harder most likely.

 

I don't think what kind of FI you have on your car matters in driving style.

I like being able to pass people at will. I like being able to go fast. But I don't do it all the time because there's a lot of cops in my area now.

 

Fair enough, just my opinion. I'm surprised that you only get 1MPG worse.... i had read that some are doing much worse which could be attributed to more intense driving after the mod. Or could be the tune itself.

 

what about with the supercharger? since we are on the mpg subject...

-Cody

 

turbo/supercharger is irrelevant... only thing that matters is the driving style and the TUNE

 

tune does play a role.

When I first had the turbo on with the EMU and the map was all fcked up, I got about 140 miles out of that tank.... and every time I shifted I blew flames.


Turbo vs SC does matter, since a turbo system is more efficent and isn't directly dragging power from the engine.

 

So, whats up with such low MPG on turbo 8's? Is it because of how rich the tune needs to be for the high compression? I know my buddies GT40R FD gets 22-23mpg..thats with city/highway mixed, and he drives it hard as hell..

 

no idea... afr should be similar or exactly the same as non turbo.

under boost, you're changing it to go down to 12 afr .... which is actually leaner than the stock pcm at upper rpms...

 

Well, the thing is, 12:1 for a non turbo is a whole lot different than 12:1 AFR for a turbo.

For example(these numbers are not correct, just an example):

If a non turbo engine sucks in 200CFM, and is running 12:1 AFR

And a turbo engine sucks in 2000CFM, and is running 12:1 AFR

The turbo engine would be using 10x more fuel to obtain the same 12:1 ratio.


I'm just wondering why the drastic difference between the FD and SE. I think the FD has 8.5:1 compression, to the 8's 10:1..but then again, all of these turbo 8's are making FAR less power than the single turbo FD's I know of.

 

yes, of course it uses more air, and thus more fuel. but like I said, unless you're in boost a lot, your numbers shouldn't be hurt much. especially if you have a catless and aftermarket exhaust to free up backpressure.

the renesis makes a ton more power than the previous rotary engines in NA form... I don't know how much we're limited due to the high compression rotors - a number of people are seeing engine failure over 350 whp though, so I'm going to stay under 300, and be happy with what I have.