You got me thinking now...good info

 

the current race miata only really has the ohlins, and a fancy diff on it, and both were totally worth it. right off the trailer we're half a second off the lap record for our class at laguna.

one of our drivers likes the S2000, just because it makes you actually drive it. i think its a stupid car. it is fast though


the miata cup cars are actually slightly quicker than the Rx8's, Mazda's run both at the 25. the Rx8's do well, but they have won outright with the miata. the NC miata actually is decently quick, and then i think the cup cars gain about 20hp, and loose a bunch of weight, so they aren't slow like the old miatae. by contrast the Rx8's look stock...


agreed! it is painfully close to a really great car.

 

REW swapped RX-8 is a wonderful ride 👍

 

Great updates. I was hoping to run about 18psi on 98 fuel, running 15 on the twins at the moment. Just waiting for a few more parts before the install commences, I will keep everyone updated with my experiences!

 

For NA the Miata is the better choice, but with FI the opposite seems to be the case. The chassis just doesn't seem to be able to use the power effectively in almost ever autox FI Miata I've ever seen. On paper it looks great, but plenty of peopld tried and eventually gave up in frustration (and a lot poorer)

However, I don't think a 7670 is possible for low mount in an RX8. It doesn't have the space down there like on the previous RX7's. Thats why there's been interest in in the EFR7163 for mid-high 3xx hp goals.

 

I don't mean to derail this thread so OP let me know and I'll just send PMs. But I'm a HUGE fan of Best Motoring...for those of you who aren't familiar here's a good related link

I spent a few hours the other day finding as many videos of an rx8 on the track with professional drivers (Best Motoring) and saw it repitedly stomped by the s2000 at the Tsukuba circuit (which is a tight, short track that would be in favor for the rx8). The power to weight ratio between the 8 and s2k IMO is not enough to warrant how much quicker the s2k was in every comparison. They both have wishbone suspension, around 50/50 weight distribution, similar tire, high revving/ low torque engine output, but the rx8 has the advantage of the rotary which obviously sits lower and closer to the driver than the F20c in the S2k. In my head the rx8 should win especially with all the praise it gets about it's handling compared to many of the complaints the s2k owners give them. I've seen stock FDs lap Tsukuba 3-4 seconds faster than even the latest models of the rx8. The rx8 has all the lessons learned from the FD chassis and improved engine placement. On paper it should be second to none with a chassis of similar power/weight...but that is not what I'm seeing in reality.

Am I missing something here?

 

^ Stock for stock there's a 20 - 30RWHP difference favoring the S2000, with bolts on, the difference is even greater.

After watching the video, maybe the RX-8 engine lost compression during the race LOL

 

As it showed in that video the S2000 was 270ps(hp) with 4.59 kg/ps power to weight ratio and the RX-8 was 250ps(hp) with a 5.24 kg/ps power to weight ratio.

Further, the video shows the S2000 had intake, ecu, coilovers, catback, race seats, coilovers, CF hood, CF hardtop, brake rotors/pads in its parts list.

RX-8 (Mazdaspeed A-spec) had Mazdaspeed muffler, seats, bodykit, brake pads.

 

No worries about side tracking this thread as the pertinent information will still be there at the beginning for people that search and I announced terminating of my EFR 7670 FC project here anyways.

Regarding S2000 vs RX-8-
I think it really is power to weight on the stock RX-8 vs S2000 that has the stock S2000 slaying the RX-8 in all the track tests.

If I had to race stock cars, I too would take the S2000 every time.

The advertised powers and weights are similar, but the actual power and weights are both worse for the RX-8 and it is hobbled by bigger diameter, heavier wheels/tires as well really sucking the power.

S1 RX-8s dyno ~180hp
S2 RX-8 dyno ~180hp
S1 RX-8 base sport weight ~2,900lb 22lb wheel 26lb tire total 192lbs
S2 RX-8 R3 weight ~3,000lbs 21lb wheel 27lb tire total 192lbs
0-60 ~6.2 sec ¼ mile ~14.8sec

AP1 S2000 dyno ~200hp
AP2 s2000 dyno ~ 215hp
AP1 S2000 weight ~2,700lb (JDM 13F/14R) 18F/19R wheel 24F/26R tire total (JDM 154lbs) 172lbs
AP2 S2000 weight ~2,800lb 18F/21R wheel 22F/26R tire total 174lbs
0-60 ~5.4sec ¼ mile ~14.1sec

Now, I think the RX-8 chassis POTENTIAL is higher than the S2000 so if I was racing a 350+ HP car I would take the RX-8.

RX-8 stock body Max wheel/tire fitment 18x11 295s (and they fit in the back seat)
Rear end/axles- doesn’t break with V8 torque behind it

S2000 stock body Max wheel/tire fitment 17x10 255s (tire trailer)
Rear end/axles break under stock power if drag raced

 

I thought rear weight was something race teams desire. Considering engines getting pushed back to where fire wall is needed to be modded and rear mounted radiators,right? They go thru a lot of trouble to do so. Mid engine cars have many many advantages and long sweeping turns is one of them.

I'm also considering why your front end feels like that, numb/n feedback. Maybe corner balancing you car closer to 50/50 might compliment your driving style. Or maybe you are not running a rear sway bar and could be the cause of the front end feeling vague?

 

I thought rear weight was something race teams desire. Considering engines getting pushed back to where fire wall is needed to be modded and rear mounted radiators,right? They go thru a lot of trouble to do so. Mid engine cars have many many advantages and long sweeping turns is one of them.

Centralized mass (engine set-back) is definitely desirable and rear weight versus 50/50 bias also has advantages along with the disadvantages.

They are definitely not the same thing. For instance a rear engine 911 has rear weight bias and poor centralization of mass. A Subaru STi has poor centralization of mass and poor rear weight bias. Both can be really fast despite their disadvantages.

I personally dislike mid-engine car handling/feel despite its advantages on the track where you have a clear line and can use the rear weight bias to get on the gas sooner.

I actually prefer the way a really well set-up Miata drives over a Lotus Exige.

I also really hate racing Subarus- you are just constantly waiting on the car to respond and even your really fast times feel slow and frustrating.

For my driving style and venue (auto-x) I prefer a car that has very fast turn in and never ever understeers.

You have to slow down to correct understeer, you have to speed up to correct oversteer.

In solo racing the oversteer bias works great as you never have a car in front keeping you from countering/accelerating out of the oversteer and you don't have a car behind you to tap you into uncorrectable oversteer.

I'm also considering why your front end feels like that, numb/n feedback. Maybe corner balancing you car closer to 50/50 might compliment your driving style. Or maybe you are not running a rear sway bar and could be the cause of the front end feeling vague?

Yes, I could work on the FC by putting a rear sway bar back on and finding a way to make it work in auto-x instead of lifting the rear wheel, putting in an aftermarket 2-way diff, putting in a lighter rear end and/or moving the gas tank forward, etc etc

But why.... I already have an FD and RX-8 which don't have the FC shortcomings- minimal chassis work required on those.

My 250? hp near stock FD with wheels/tires/exhaust/brakes/seats ran a 2:19 on the hillclimb and mid 47sec laps at the enduro and my crazy fast 400rwhp FC ran 2:24 on the hillclimb and mid 49sec laps at the enduro.

Watching the videos its clear I had to brake waaaay earlier and slow more in the FC due to lack of grip from skinny tires and lots of negative camber up front.

Further, if I want good dampers for the FC I have to fabricate/valve something instead of buying great off the shelf units (Ohlins, Moton, JRZ, Penske, AST) available for the FD and RX-8.

If I want to run wide wheels/tires I need a widebody and totally redo the suspension/steering due to huge offset change. Even then my front suspension travel is severely limited by tire height and the unibody above the tire and the rear suspension still weighs a ton.

And I would have to run even higher spring rates/more negative camber to overcome the strut front vs bodyroll.

I have seen where all this leads by driving my friends CP mustang. It drives like a buckboard wagon with super spongy tall sidewall tires. Yes, its fast- yes its a POS to drive.

I understand not everyone can afford an FD let alone mod one, but if you can afford and FC you can afford an RX-8 (and the RX-8 chassis is superior to the FD anyways)!

Good thing I started this thread or I would feel bad about that long rant.

 

lol! lots of good points there. i will add some semi-relevant ones, this is the forum after all!

in road racing we have a slightly different set of problems, so we will use different setups depending on the length of the race, and or the track.

for instance the 25 hour car, is setup to be easy, as the drivers are in there for 2 hours at a time, and if they do a double, its 4. so its soft, and it understeers a little (its a miata last year, and this year, hint hint)

for a sprint race though, we set it up exactly like your solo car, we want a teeny bit of oversteer, as you can hit the gas earlier, and drive it out of a corner, vs an understeering setup having to wait to get on the gas.

dad and i went to Rennfest a couple years ago, and watching a 911 go through a turn next to a boxster was interesting, the 911 clearly has the engine in the wrong place, it looks like a cartoon...

 

Yeah, watching the FWD B-spec touring cars at Infineon was lots of fun.

The FWD cars don't have much choice but to set up the chassis for oversteer or they will cook their front tires (more)/get stomped by their competitors that can rotate and get back on the gas.

As a result the whole race is like bumper cars as they alternate trying to nudge each other into a spin on corner entry with the target car's resultant accelerating/counter into the car in front of them to keep from spinning.

Nascar has nothing on B-spec FWD touring cars if rubbing = racing.

 

its funny, the intergra's setup is the same as the FC, its just backwards. the honda is a good race car, as its pretty quick, reliable, and its cheap to run. the downsides are that the honda chassis is an economy car chassis, so we bend things and break spot welds, and then its a 60/40 weight distribution with FWD, so it can brick a tire in 1 turn.

we're running a pair of miatae this year, and they are so easy*. they are easy on tires, i'm sure the driver could burn a tire up, but so far they haven't. the chassis is also much more robust than the honda.


*hp/$ in a miata is terrible.

 

Many good points. Well then I guess I will just dump my engine in a 8. . Thanks for the lap time comparisons. Really says a lot. Forget the tech talk. Its not like I would somehow achieve a supremely better setup to keep up with the fd.

 

1 more question. What the weight comparison between the your fd and fc.

 

1 more question. What the weight comparison between the your fd and fc.


My FC is 2,5xxLbs (up to almost 2,600Lbs with a full tank of gas).

FC is built for SCCA SSM- ie it is full base interior, no sunroof, full TII running gear.

The only place I can think of easily taking weight out is that it has HEAVY Infini seats instead of true race buckets (it was my daily for years), ditching the heavy Optima battery for a 4lb LiFePo (again-was daily) and running a normal size radiator instead of the giant one (and switch it out to big one for track/hillclimb...)

Could probably get a turbo FC in SSM to 2,4xxlbs fairly easily and 2,3xxx with lots of $$ and time. Still, the FC should be in SM with the 240SX- hope they fix that.
-----------

The FD is 2,6xxx (up to and just over 2,700lb with full 20gallons of gas).

FD is a not very prepared SCCA A Street Prepared build (class below SSM), though it does have Bride CF seats dropping some weight, 4lb battery, light exhaust- but big brakes and big wheels/tires adding weight back in.

 

Why does the bw make so much less hp than the hybrid at similar boost levels? Is the 7076 the right turbo for 300-350rwhp goals as a dd trying to stay under 15psi and away from spray?

 

I ask because Aaron Cake suggested the gtx3076r as the best turbo for my goals,(300-350whp, 15psi area just below needing spray, best response and quickest spool) I was trollin around on turblown and was curious of a turbo kit including it and Elliot White of Turblown suggested the efr 7670 over the garret. I'm not into the higher psi though, will that be whats necessary to get the 7670 to work how I want it? In terms of power made, response and spool time?

 

I would choose the GTX3076R. Although the turbine wheel on the EFR is lighter and would have better spool, the aero on the EFR is much better suited for high boost. At 1 barg, the GTX makes about 55lb flow at 65% eff. At the same pressure, the EFR makes about 43lb flow. Big difference on low boost.

 

I'm not sure I have seen better response and power over Jacob Cartmill's dyno on his 8374EFR internally gated. I think he was running 12-13lbs and made 340rwhp on a dyno dynamics(reads much lower than the ego dynos) and a massive amount of low end torque. Most I had ever seen at those boost levels. I really just dont see other turbos outperforming the 8374 on low end response and power at the same boost levels.

 

I thought it was power, not boost, which determined the limits of your set up? If the 7670 requires 18-20psi to reach your power goals, instead of 15, shouldn't that be ok?

 

^not necessarily. You can run 15 psi on pump gas safely, 20 psi..... not so much.

Also, things like running race plugs (and having enough fuel pump) becomes more important at higher boost levels.

 

What is considered pump gas in the states? 91? We use 98 (our premium pump gas) here as pump gas on the FD. I run 15psi on the twins right now on 98, have for 3 years with no issues. Was hoping to turn it up a little with the 7670 installation, with a bigger v-mount system, better fuelling and better cooling. I was originally shooting for the 300rwkw mark, but I decided I was really shooting for better top end with similar response and a more stable power curve. Picking up the v-mount from thermal coating today. Installation in a few weeks or so.

 

91/93 which is roughly comparable to 95/98 where you're at.