With all possible SM weight reduction being done (c/f hood & trunk, removal of rear seats, etc), how low do you think one could get realistically?

 

I know engine swaps are legal in SM but is it legal to swap in a piston engine, say a turbo'd 2.0?

 

Are you peeking over my shoulder Miles? I currently have three engine scenarios for a street mod RX-8 (see option 3 below):

#1 Forced induction 13B
Minimum weight = 2,700lbs
I could go with a s/c or turbo. If I kept the Renesis, I'd buy a built 13B-MSP from Pettit Racing. They add some internal mods that make the engine more reliable for forced induction. I like the immediate throttle response of the s/c, but dislike the fact that it'll have the same peaky powerband as the n/a engine. A turbo would provide much more torque down low (as well as throughout the entire powerband), but there could be some lag to deal with when driving the car on course.

#2 16X (n/a)
Minimum weight = 2,480lbs
This engine is rumored to be making close to 300hp/200tq at the crank (if it ever materializes). With a full "catless" exhaust, intake, race gas and a good ECU tune, making 300+whp/200+wtq should be very doable. I like the fact that the car would have a low minimum weight, but I'm not sure if it's attainable??? This would be the light and nimble option which I like the best...but, who knows if and when this engine would appear in a production Mazda????

#3 MX-5 2.0L engine w/ Turbo
Minimum weight = 2,480lbs
Same minimum weight as the 16X n/a engine, but with a whole lot more hp/tq potential. Because it's a piston engine it doesn't carry the weight penalty that rotaries have. Cosworth makes forged pistons and connecting rods for the engine. Engine wouldn't sit as low or as far back in the chassis as the 13B/16X renesis so the weight distribution/handling would be adversely affected in some way (but it shouldn't be too significant). However, I like this option the least as it "bastardizes" the RX-8, but it is a Mazda engine and a legal swap for Street Mod.

I'm still in the hypothetical stage at this point, and considering my options. Might just buy a GT-R in a few years and keep the RX-8 in STX trim...

 

Jeez, why bother with the GTR when you can go GT2RS?

Google came up dry, but just how close is an NC drivetrain to just dropping in an RX8?

 

the forced induction rotary makes the most sense IMO. You don't need to make mega power (350 hp should suffice IMO), just a reasonable amount with good low end response.

FYI, most CF hoods weigh as much or more than the OE aluminum hood. Better off keeping it, cutting off the reinforcing under-layer, and cutting various duct holes in it while also saving a bunch of money for other things.

 

GT2 RS would be WAAAY oout of my price range. Realistic cars that'll be within my reach in the not-too-distant future are a new GT-R, used GT3 as well as a NSX. I like all three of these cars for different reasons.
I've been thinking that as well. However, the 16X is just a big ? right now. Hopefully it sees production and it's as good as they say.

 

A Renesis or 13B-REW would make more sense than trying to cut your teeth on unknown 16X territory, assuming it's ever produced and is worth the bother. Look at what it took just to develop the FI Renesis to where it is today ...

 

I tend to agree that a rotary makes the most sense, but if I were going to put a Mazda piston engine in, I would seriously consider the 2.5 turbo from the MS3.

 

I'd have to agree. Even if the 16X makes it to production, it could be a couple of years before there's a good aftermarket for it. I would have to go custom everything...and if the engine proved to be fragile, things would get $$$ very quickly.
I did consider that engine, but I'm not sure how hard it would be to take a transversely mounted engine from a FF platform and adapt to work in a FR platform???

 

yes would that be so hard? i am also thinking to have same engine...

 

About as hard as having a clue ....

 

Well, I'll be the first to admit that I know very little about a swap of this nature. However, a 13B w/ FI seems to be the most logical way to go.

 

^Never done an engine swap myself. But it seems that with either the 2.0 or 2.5, you'd have to fabricate engine mounts, and do all sorts of custom work (such as ECU & harness) so I don't think the net work would be that much different. But I'm sure there would be some differences.

 

Why reinvent the wheel... Mckee's drivetrain in an RX-8, you are done.

 

Is there a dyno sheet of McKee's car in SSM trim posted anywhere? I've only been able to find one when it was still an ASP car.

Personally, I'd also like to find out the upper limits of a s/c system on a 13B-MSP. Imho, the linear powerband of a s/c would make the car much easier to drive at the limit. With that said, I've never driven a turbo SM/SSM car prepped to the level of McKee's. Only ones I've driven have been STi's and Evos with decent local/regional set-ups (making 350-400whp on aftermarket turbos).

 

Jason's comment makes a lot of sense at some levels, but some of us enter these modifed classes to learn how to make a car fast, or to try something that hasn't been done before. Probably not very smart, but the challenge of making a fast car is what drives us.

To that end, if I were to ever make a hybrid Mazda SM car, I'd sooner put a force-fed rotary in a MX-5 chassis than a thumper motor in an RX-8 chassis.

Mmmm, a turbo/SC rotary powered MX-5. Now that would be a fun solo car. Have no idea how competitive it could become, however.

 

I seem to remember one of Eric's car that basically made 400 lb-ft of torque ... everywhere.

 

Yup, I've seen that dyno. It's posted on the forum at 7parts...

 

Except that either a 13B-REW (or a 20B) is a lot more work in an SE3P than an FD3. Still better to stick with the Reni IMO.

 

Interesting Street Modified proposal in the January 2011 Fastrack:

LS swap in an RX-8 in street mod....

 

Meh, too heavy. Stay 2-rotor NA and use 275 tires, the min allowable weight then becomes low-2200# range. Not sure you can get all the way there, but low 2300# range might be possible in an all out effort. Ultimately turbo 2-rotor will be the max value - min effort entry point @ 2740#, but you better stick with reasonable boost and high octane fuel to keep the motor from popping. Even then luck better be on your side. I still think the lowest possible weight option will ultimately be quickest over the power option.

I actually backed off the "stick with the Reni" comment, been discussing a 13B-PP & MoTeC combo, but the price point is about as steep as a homebuilt 20B effort world class pro racing setup though, big power buzz bomb


.