SCCA Street Modified RX-8
09-06-2019, 05:41 AM
#176
Sounds kinda similar to mine in certain turns, especially tight (for racetrack anyway) steady relatively long turns. Like it doesn’t want to take a set right away. Feels more lateral though not vertical but I could be wrong. I’ve been blaming it on the stock rear suspension bushings but you’ve already got sphericals. Mine improved going from 180k mile original bushings to new stock one but still it’s limiting especially as it delays getting to the power. Will be interested what you find to be the cause.
Front end was bottoming.
01-01-2020, 01:48 PM
#186
I don't really know. My guess with no engine or transmission would be around 2,050-2,150lbs. It depends how silly you want to get with tiny brakes and stuff. I should have weighed the car when I had the engine and gearbox out, but everything else on the car (battery, wing, cooling system, etc) but I didn't do it.
01-01-2020, 08:04 PM
#188
I weighed the MZR engine fully dressed minus the turbo and it was around 300lbs. The FD RX-7 gearbox was a little heavier than the G Force that is on there now, which is right around 70lbs.
When I had the fully dressed renesis that came out of the car it was heavier, like 315lbs IIRC but it had the clutch and flywheel on it.
When I had the fully dressed renesis that came out of the car it was heavier, like 315lbs IIRC but it had the clutch and flywheel on it.
01-02-2020, 12:06 PM
#190
An interesting SM build that I pondered is an NA 2.4L Honda K24 powerplant with a BMW ZF gearbox behind it. You pay a 150 weight penalty for the non-marque-matching engine, but an NA 2.4 plays to a 2280lb minimum, so you're looking at a min weight of 2,430lb. I think that'd be hard to get to, but maybe not impossible. Say the car ends up at 2,500 or just under, and you make 270-300whp out of that engine. Maybe not the best ProSolo car but on a speed-maintenance course it could hurt a lot of feelings, and be really easy to drive and very reliable.
I think eventually I'll figure out how to drive the turbo car well, but I do wonder from time to time if I should have put the extra engineering effort into doing the screw blower that I originally wanted. They are hard on engines, but the driveability is hard to beat, and it would have made an easy 350whp.
I think eventually I'll figure out how to drive the turbo car well, but I do wonder from time to time if I should have put the extra engineering effort into doing the screw blower that I originally wanted. They are hard on engines, but the driveability is hard to beat, and it would have made an easy 350whp.
01-02-2020, 11:11 PM
#192
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Call me crazy, and trust me most people likely will, but I'm pretty damn tempted into doing the reverse of your swap. I just blew the 2L on my NC1 (miata) and have been looking into 2.5s but I'm just not feeling it. I've always been a rotary nerd and can't help but be seduced by the idea of a Renesis NC miata! Subframes are plug and play bolt on swap between the 2 from what I hear, and the ECU's are both located in the engine bay so in theory (emphasis on theory) I could pick up a wrecked RX-8 and potentially swap drivetrains? Yes yes, I know the driveshafts and PPF frames won't be compatible. My main concern currently is wiring. Since the miata gauge cluster plugged into the rx8 wiring, in theory the same could be said about the 8 to the miata? Am I wrong in thinking that I could swap in the renesis with the ECU and engine wiring and swap the guage cluster and ignition to start the car?
Also, not sure if you still have it, but definitely swap out the stock plastic coolant expansion tank. They're a known failure point in the NC's where the tanks crack right around the filler neck and release all pressure from the coolant system. Moroso makes a aluminum version thats a direct bolt in for the miata.
Also, not sure if you still have it, but definitely swap out the stock plastic coolant expansion tank. They're a known failure point in the NC's where the tanks crack right around the filler neck and release all pressure from the coolant system. Moroso makes a aluminum version thats a direct bolt in for the miata.
01-03-2020, 10:31 AM
#194
A few tried and as far as I know were never completed including one by Mazmart(?). The wiring was a nightmare and I think they canned the idea for that reason. The guy in Australia ended using a 13B instead along with making it a dedicated race car.
there are dedicated threads for the subject; this isn’t the correct one to discuss it. You’d be better off reviving it on the Miata forum instead:
https://forum.miata.net/vb/showthrea...=346459&page=5
there are dedicated threads for the subject; this isn’t the correct one to discuss it. You’d be better off reviving it on the Miata forum instead:
https://forum.miata.net/vb/showthrea...=346459&page=5
01-03-2020, 06:17 PM
#195
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Oh yeah I've seen and been ogling that build for months! And yeah, sorry for thread jacking.
Appreciate the help though! I would've tried reviving an old thread on the miata forums, but every time someone brings up anything but the normal 2.5 duratec or LF V6 swap people just say "whats the point?".
Appreciate the help though! I would've tried reviving an old thread on the miata forums, but every time someone brings up anything but the normal 2.5 duratec or LF V6 swap people just say "whats the point?".
01-07-2020, 06:27 PM
#196
After studying this some more, I’m not sure how you came to the decision to use the MRZ engine? That’s not intended as a criticism, but just wanting to see if I’m overlooking something. Because it seems to me a 13B turbo setup would get you a lot more and still be able to hit the minimum allowed weight, which is actually a few lbs less than with the MRZ.
13B 2-rotor
1800 lbs + [(1.308L x 1.8) + 1.4] x 200 lbs = 2551 lbs minimum
MRZ 4-cyl
1800 lbs + (2.488L + 1.4) x 200 lbs = 2578 lbs minimum
I know in the past people considered a turbo rotary engine unreliable, but in the case of the 13B-REW that just isn’t true anymore if it’s built and supported properly. Additionally for the same boost level given the current technology it can make more torque and hp over a wider range. Other than just doing something different; which I can entirely relate too, I’m just scratching my head some on this.
13B 2-rotor
1800 lbs + [(1.308L x 1.8) + 1.4] x 200 lbs = 2551 lbs minimum
MRZ 4-cyl
1800 lbs + (2.488L + 1.4) x 200 lbs = 2578 lbs minimum
I know in the past people considered a turbo rotary engine unreliable, but in the case of the 13B-REW that just isn’t true anymore if it’s built and supported properly. Additionally for the same boost level given the current technology it can make more torque and hp over a wider range. Other than just doing something different; which I can entirely relate too, I’m just scratching my head some on this.
01-07-2020, 08:46 PM
#197
After studying this some more, I’m not sure how you came to the decision to use the MRZ engine? That’s not intended as a criticism, but just wanting to see if I’m overlooking something. Because it seems to me a 13B turbo setup would get you a lot more and still be able to hit the minimum allowed weight, which is actually a few lbs less than with the MRZ.
13B 2-rotor
1800 lbs + [(1.308L x 1.8) + 1.4] x 200 lbs = 2551 lbs minimum
MRZ 4-cyl
1800 lbs + (2.488L + 1.4) x 200 lbs = 2578 lbs minimum
I know in the past people considered a turbo rotary engine unreliable, but in the case of the 13B-REW that just isn’t true anymore if it’s built and supported properly. Additionally for the same boost level given the current technology it can make more torque and hp over a wider range. Other than just doing something different; which I can entirely relate too, I’m just scratching my head some on this.
13B 2-rotor
1800 lbs + [(1.308L x 1.8) + 1.4] x 200 lbs = 2551 lbs minimum
MRZ 4-cyl
1800 lbs + (2.488L + 1.4) x 200 lbs = 2578 lbs minimum
I know in the past people considered a turbo rotary engine unreliable, but in the case of the 13B-REW that just isn’t true anymore if it’s built and supported properly. Additionally for the same boost level given the current technology it can make more torque and hp over a wider range. Other than just doing something different; which I can entirely relate too, I’m just scratching my head some on this.
"Rotary Engines (Wankel) – These units will be classified on the basis of a piston displacement equivalent to 0.9 liters times the number of rotors, plus the volume determined by the difference between the maximum and minimum capacity of the working chamber times the number of rotors."
0.9 * 2 + (1308/2)*2 = 3.108L. Plus 1.4L for forced induction.
Second, it's a lot easier and a lot cheaper to make the broad power with a four cylinder. To make 450whp reliably, and more importantly to make power over a 4,000-5,000 RPM spread with a 13BREW is a big dollar affair and they are still finicky to tune. They require bigger, more expensive turbos to make the same power. There is no getting around how expensive rotary parts are, and even well tuned, they just don't last that long. My original junkyard 2.5 would have been perfectly happy at 400whp had I not screwed up and overboosted it so badly. And that engine was < $300. My new engine with studs, forged rods and pistons is under $1,000.
01-07-2020, 08:58 PM
#198
"Rotary Engines (Wankel) – These units will be classified on the basis of a piston displacement equivalent to 0.9 liters times the number of rotors, plus the volume determined by the difference between the maximum and minimum capacity of the working chamber times the number of rotors."
0.9 * 2 + (1308/2)*2 = 3.108L. Plus 1.4L for forced induction.
.
01-07-2020, 09:09 PM
#199
Not sure where my head was on that, but I kind of eluded to the idea I must be missing something. So there you have it; my complete and total fail. 
1800 lbs + (4.508 x 200 lbs) = 2701 lbs
I had 2700 lbs in my head from the past, so just my dumb mistake for not recognizing it.
you’re definitely right on the cost. A brand new 13B-REW (not reman) is $3500 from Motorsports and then you need a pile of dough making it stout and installing the turbo and support system. I still see it being competitive though, but as you said, not cheap.
.
1800 lbs + (4.508 x 200 lbs) = 2701 lbs
I had 2700 lbs in my head from the past, so just my dumb mistake for not recognizing it.
you’re definitely right on the cost. A brand new 13B-REW (not reman) is $3500 from Motorsports and then you need a pile of dough making it stout and installing the turbo and support system. I still see it being competitive though, but as you said, not cheap.
.
Last edited by TeamRX8; 01-07-2020 at 09:19 PM.
01-07-2020, 09:38 PM
#200
So, just food for thought ...
0.9 + (654/2)*2 = 1.554L + 1.4L = 2.954L
1800 + (2.954 x 200) = 2391 lbs - 200 lbs for 275 tires = 2191 lbs minimum
E85 and 30-34 psig boost should get about 360-400 whp and 250-275 ft-lbs, not sure if you had hit that minimum weight target though. Could be interesting.
0.9 + (654/2)*2 = 1.554L + 1.4L = 2.954L
1800 + (2.954 x 200) = 2391 lbs - 200 lbs for 275 tires = 2191 lbs minimum
E85 and 30-34 psig boost should get about 360-400 whp and 250-275 ft-lbs, not sure if you had hit that minimum weight target though. Could be interesting.