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My friend Alex has one of the hardest accelerating Twins I've ever driven and he dyno's 195whp with STX legal mods. Intake tune header, single high flow cat, full cat back. His car accelerates much harder than mine.
Hufflepuff my engine is pretty fresh, I did the rebuild in the spring and it has about 15k on it now, It's much stronger than it was before, particularly from 5k and below. I have stock intake, basic Hypertech sport map, turboxs catback with moreoso resonator to quiet things down. I haven't dyno'd it but a VirtualDyno run showed 175whp. Much more can be had with a good quality header collector and more capable tuning hardware.
Our gearing creates the reduced acceleration, with second on my car topping out at 70mph (9900rpm redline) you can use smaller tires to improve gearing, I use the STX "go to" size of 255/40/17 on a 17x9, this is about 3.5% shorter gearing and brings redline in second to about 68mph while making you pull a bit harder everywhere.
The RX-8's strength at a national level is braking performance.
cornering grip is similar, the twins light weight is essentially a dead heat with our superior DWB front suspension in terms of cornering ability. But we have the additional benefit of our tires lasting longer because we can run less static camber for a given grip level.
The advantage of our braking performance comes from the same feature on the the twins, the McPherson struts. They need to use pretty extreme amounts of front camber to get their cornering to work well and that makes them comparatively squirrelly and unstable under braking compared to our DWB system.
My car isn't 100% by any means, but after driving Steve Mitchell's BRZ I think it'll be struggle to stay ahead, I was significantly faster in the BRZ, on the order of 1.5 seconds on a 70 second course, and that was in one run.
That all being said, the car is so much more fun to drive in STX trim vs CS that I don't plan to go back to street class, I've raw timed little Mike Snyder's STS CRX locally which if you were to compare apples and oranges, raw timing him at Nationals this year would've been good enough to trophy in STX. I'm sticking with it for the season, the twins are just not as good as road cars (I know, I own one)and I drive the car everyday and I think the RX8 should still be strong in STX with a good driver, good prep, and a little luck.
I think the RX8 should still be strong in STX with a good driver, good prep, and a little luck.
I was about mention last year when a 350z took 1st in STR at Nationals out of nowhere in a field of MX-5's and S2k's. Doesn't matter what car you have if your a crap driver and/or have a crap setup.
I'll be running my 8 in STX for the time being so I guess I'll find out first hand.
Hey all, I'm a fairly recent STX RX8 convert (bought Ruggles previous car in March after running a Mazdaspeed3 for a while) and took the car to Nationals in September...from what I can tell the biggest disadvantage vs the twins is corner exit out of low speed corners ("digs") while the RX8 advantage comes through with a higher top speed in 2nd gear, so I think course design does have a pretty big effect on how competitive we can be vs the twins on a given day.
A good example, this year at the Wilmington Tour my car managed to finish in 3rd & 6th out of 21 drivers with best times only a few tenths off of a FRS (Santel) and BMW (Herbst) on a given day (my co-driver ran great on Day 1, I drove great on Day 2) that placed Top 5 at Nationals. The course design at Wilmington involved only 1-2 low speed digs with lots of higher speed transitions (55-60mph) and lot slaloms. The next month at Nationals I couldn't really hang with these guys on the higher speed Day 2 course while I coned away any good runs on Day 1 (would have been in the last trophy spot if not for coning my best 2 runs the first day). My thought is the RX8 can crack the Top 5/10 with some really good driving and the right course design, but beating all of the twins outright at Nationals is probably out of the question.
That said, there were about 10k+ reasons for going with a used RX8 that is prepped for STX vs a stock used twin. Plus being a Mazda guy I have always liked the looks of the RX8 and having driven both on the street the FRS/BRZ lacks the same "driving feel" and enjoyment for just general driving.
This year my plan was just to purchase the car and run it "as is" while getting a feel for everything...the chassis is great and other than putting my own set-up on the car no real changes were made. This winter I'm planning a few HP mods (BHR ignition, header, pulleys) to squeeze a little more power out of the car for next season (it dyno'd at 165hp on a Mustang dyno before going to Nationals...original engine with 67k). The KWv3 coil-overs feel a little undersprung but other suspension options are too $$$ for right now. I'll stick around in STX next season to give Nationals another shot (everyone says you drive like **** your first year, and they're right...but I had a blast all week) before contemplating a move to DSP in 2017.
I went out to a "circuitcross" this past weekend, Hufflepuff showed me the fast way around! The car felt pretty "at home" on the big course, it was lots of fun!
The circuitcross was a good time. A mostly stock RX-8 is a blast to hussle around - an STX RX-8 feels even better!! Thanks to Nate for letting me ride in his car. Much better grip and composure.
Last edited by hufflepuff; 12-15-2015 at 05:45 AM.
searching on this site being what it is, I have yet to find good before/after dyno plots for headers. I'm interested in seeing midrange gains from an STX legal header.
It seems all that most of the people who post about it are interested in are peak power, of which there is little to be had.
Here's my VIrtual dyno plot, ambient temp was 32 but inlet air temp was 74, I wasn't sure which to use for temperature. I'm not sure but I think the flat top end might be a fuel supply issue. all the actuators open and with the correct timing, flattening out at the top end might be an indication of a dying fuel pump. I was thinking of replacing with the DW200 but I read the Walboro 255lph pump is the play. I'm posting on the forum so Sipe can Imply I'm an idiot for not searching. ;-)
Here's my VIrtual dyno plot, ambient temp was 32 but inlet air temp was 74, I wasn't sure which to use for temperature. I'm not sure but I think the flat top end might be a fuel supply issue. all the actuators open and with the correct timing, flattening out at the top end might be an indication of a dying fuel pump. I was thinking of replacing with the DW200 but I read the Walboro 255lph pump is the play. I'm posting on the forum so Sipe can Imply I'm an idiot for not searching. ;-)
Inlet temp would be the one to use, although I am continually amazed by how much pick-up / soak these cars seem to see - implies there is a lot of potential benefit from better insulation.
I doubt you are running out of fuel. You didn't show any f/a plots, are you running lean? I have seen the same flat hp trend before, and I think the Renesis is just running out of breath above 8K. In any event, there is no allowance in ST to upgrade the pump, so at best you can replace it with a new stock unit.
Last edited by fossumja; 12-22-2015 at 01:16 PM.
Reason: clarity
searching on this site being what it is, I have yet to find good before/after dyno plots for headers. I'm interested in seeing midrange gains from an STX legal header.
It seems all that most of the people who post about it are interested in are peak power, of which there is little to be had.
Sigh...
If you find a good before/after dyno plot I'd be interested to see it. I looked into a short tube header earlier this year when my engine was out, but ultimately decided against it as the gains appeared to be pretty small for the cost, and then I would have to deal with the heat, or adding some shielding.
According to the info on the RB site, peak gains with their short tube header is 4hp. I think this is the peak hp gain over stock, not the hp gain at peak, although it could be the same. So, figure midrange gains will be
I guess this thread does not like what I wanted to say about midrange gains... (less than 4hp is my guess, but things might improve when combined with other mods)
I went ahead and got the TurboXS header to experiment with, I'm going to do some port matching to improve the flow at the flange.
The collector is a bit shitty as I expected, I'm going to see what sort of pickup It gets me and If I'm compelled to do so in the future I'll cut off the collector and weld on a nice Burns 3-1 merge unit.
From what Ive read the full exhaust to include the header is a sort of "across the whole rev range" improvement in flow, but still the engine is exhaust port limited so there just isnt much to be found.
I'm going to be checking fuel pressure this weekend if the weather permits it, and If thats a problem I will sort it out and then make a baseline dyno run, then another after the header install.
I also plan to make a heat shield for the header to keep engine bay temps down, and to wrap the intake box in thermally reflective tape to keep the intake charge cool. Also I plan to open the hood between runs to evacuate more heat, a change of 10 degrees is worth roughly 5 horsepower so it seems worthwhile to do.
Last edited by Nathan Atkins; 12-23-2015 at 07:52 PM.
Ok so the intent is to order the N3H1-13-35ZG fuel pump assembly from Mazda for $250+shipping, this keeps me class legal. Does anyone see a flaw with this plan? There was no supersession part number for it. Anything else I should order now with it? tools, gaskets etc?
Does anyone here use the aftermarket pumps and just no one protests, kind of like the coils thing? (by this I mean, by my understanding the letter of the law regarding coils when I was in CS is they must be OEM but everyone uses aftermarket ones anyway)
There are numerous threads about fuel pumps and I read pages and pages of stuff and this is what it seems to point to, please just let me know if in your opinion I'm going about this in anything other than the best way possible within the rules.
did a bunch more diagnosing stuff, fuel pump seems fine, hold ~58psi in all situations. Also the AFR gets a bit rich at high rpm but nothing drastically out of the ordinary ~11.5AFR or so at the upper end in the open loop zone.
did a bunch more diagnosing stuff, fuel pump seems fine, hold ~58psi in all situations. Also the AFR gets a bit rich at high rpm but nothing drastically out of the ordinary ~11.5AFR or so at the upper end in the open loop zone.
So still a bit at a loss...
Is it possible the issue is with the virtual dyno measurement?
Figured I would introduce myself in this thread. I picked up Sparky's RX-8 and Im planning on running it nationally this year. Still new to RX-8s but I know this car is quite fast and a hoot to drive. I've been roaming the forums trying to see what I need to know and what performance is still left on the table as far as car set up goes. Im not worried about the Handling, Dennis did a good job there, just trying to figure out the engine and maybe weight savings. Thanks for all the great discussions so far hopefully I will have something to add soon. Can anyone confirm realistic power expectations on a STX trim car? Is e85 exploitable? If this has already been covered before sorry. Ive done hunting here and hearing everything from 175whp to 220whp wanted an idea on whats practical. Thanks in advance guys.
Figured I would introduce myself in this thread. I picked up Sparky's RX-8 and Im planning on running it nationally this year. Still new to RX-8s but I know this car is quite fast and a hoot to drive. I've been roaming the forums trying to see what I need to know and what performance is still left on the table as far as car set up goes. Im not worried about the Handling, Dennis did a good job there, just trying to figure out the engine and maybe weight savings. Thanks for all the great discussions so far hopefully I will have something to add soon. Can anyone confirm realistic power expectations on a STX trim car? Is e85 exploitable? If this has already been covered before sorry. Ive done hunting here and hearing everything from 175whp to 220whp wanted an idea on whats practical. Thanks in advance guys.
From what I recall, Dennis never put a header on the car which will buy you a few top end hp and a couple pounds of weight. I think that's about it on power gains. Unfortunately (or fortunately - depending on how you look at it) there's not a lot else to be gained at a reasonable cost. Lighter brakes and shocks will save a few pounds but won't be cheap. Racing seats will drop around 20 lbs if you can live with them on the street. E85 is no longer allowed in STX.
Does anyone here use the aftermarket pumps and just no one protests, kind of like the coils thing? (by this I mean, by my understanding the letter of the law regarding coils when I was in CS is they must be OEM but everyone uses aftermarket ones anyway)
The SCCA rules specifically permit any type of ignition coils (so D585's are legal), as long as the bracket attaches to the oem mounting location. This includes CS.
13.9 ELECTRICAL SYSTEM
A. The make of spark plugs, points, ignition coil and high tension wires is unrestricted
including spark plug wires having an in-line capacitor. Substitution
or addition of ignition coil mounting brackets is permitted, provided
they affix to the original standard location and serve no other purpose.
(Modification of the distributor cap for the purpose of installing allowed
non-standard components is not permitted.)
Fuel pumps are not mentioned until Street Mod, so they are not permitted in STX.
Got some in-car footage for my first time on something resembling an autocross course with my 8. Spun myself right around on a poorly timed 1-2 shift. It wasn't a competition event so my driving is a little lackadaisical at best. Really looking forward to this season.
^Looks like you were having fun
Just a thought here, would it be better to keep at least one hand in a fixed position on the wheel most of the time? I always found it was easier to catch a spin that way, and when you do lose it, bringing the wheel back to straight ahead tends to stop the car going around for a 2nd 180 degrees (i.e. you regain control more quickly).
Yeah, I noticed my poor form watching the video after. I think part of the course required more turning and I had to shuffle. I was running the event and two cars at the same time so its safe to say I wasn't "in the zone".
I went ahead and ordered the BHR resonator to replace my buzzing/failed Moroso unit. I still haven't installed the TXS header but will do so at the same time as I replace the resonator. after that i'll be doing a dyno run with AFR
I have a Hypertech programmer that just has a blanket mystery tune. I know very little of tuning and I want to learn so Im going to investigate some, but I think I can be sure this hypertech isn't going to get it done.
I went ahead and ordered the BHR resonator to replace my buzzing/failed Moroso unit. I still haven't installed the TXS header but will do so at the same time as I replace the resonator. after that i'll be doing a dyno run with AFR
I have a Hypertech programmer that just has a blanket mystery tune. I know very little of tuning and I want to learn so Im going to investigate some, but I think I can be sure this hypertech isn't going to get it done.
Why no Accessport? Less expensive I assume?
Ran the local autocross in Clemson, SC this past weekend. It's not on par with an scca event but still good for testing and practice. 2nd and 5th overall wasn't too shabby for it's first time out. 1st was an STX Toyobaru of course...
Think anyone will call foul if I install a Sohn adapter kit? I don't know how long I'll run in STX or how competitive I'll be but I'm just trying to make this 10k mile engine last.
12-08-2015, 09:34 AM
