RX8, learn me care and feeding and suspension travel.

So I have some RX8 inquires due to a certain curiousity that I have.

1) care and feeding for the Renesis, potential issues, preventative measures that keep them happy.

2) have much suspension travel does an RX8 have.

3) modifications needed to allow for the fitment of 15" wheels. 

I'm curious about the weight of the doors and seats as well, but realistically I think it will be very difficult to get one below 2900lb, but I think the chassis is good enough to potentially perform even at a hefty weight..

Regarding #3 - The only way to do this would be to install much smaller brakes. I wouldn't do that. Some 17" wheels do not fit. I had to "clearance" some calipers to make a set of 17s fit. The OEM brakes are awesome. 14-15 years ago when the car was new, some car mags measured it stopping from 70-0 in 145 feet. On comparable rubber I think only a 911 GT3 and certain 'Vettes have bested that. You can track the car lap after lap. All the other cars hit the pits, take a break, come back out, go back in and the RX-8 keeps going (atleast at some tracks) until gas is ~1/4 and the fuel pump starts to pull air on certain corners

Regarding #1, you'll read a lot of superstitious stuff. Honestly I don't think any of it is scientifically rigorous. Are the S2s better? Maybe, the sample size is a lot smaller and the most problematic S1 cars were the '04s. I'd consider running a heavier oil for track duty.

The S1 GS models were 2900lbs, so yeah, you can get well under 2900lbs. As with any car, I'd be shocked if you couldn't strip out 300lbs in race trim. The rear seats probably don't save much weight, the fronts strike me as reasonably heavy. I know door weight measurements are out there, but I don't think they're too bad. I believe the rears have some aluminum in them. The sheet metal is pretty thin. I believe most of the rigidity/crash structure is in the floor.

When I was seriously considering one about 5 years ago, I remember that a lot of folks were running 2-stroke oil in the gas. Seemed to make a lot of sense to me. No clue if there has been anything to back that up

I believe that fitting 15" wheels requires control arm modification as well. Fidelity101 had a thread here at one point showing test fitting of 15" wheels and what was in the way. I assume you are thinking of rally tires. 

In reply to EvanB :

You'd be correct in that assumption. I'm strongly considering either an RX8 or MR-S for a C2 rally cross build. An S2000 is the correct answer, but the starting point pricewise makes it tough to stomach cutting one up.

Any manual RX8 came with factory 18" wheels, and you are not going to fit anything smaller than a 17 without changing the brakes. The 2004-2005 (maybe 06 as well?) automatics without the sport package came with 16" wheels. You might be able to fit 15's over those brakes, but I don't really pay attention to automatic 8's and I don't know if anyone has tried a 15.

For reliability, keep the oil topped off, change the oil regularly, redline it regularly, get an aftermarket temperature gauge (by the time the stock one moves you are already in trouble), replace the plugs/coils/wires every 30k (less if tracking), and don't shut it off cold.

I've heard both sides of the premix-with-working-omp debate, and I'm not 100% sure if it is necessary or if it even helps.  My though is that it can't hurt and I add ~8oz of 2-stroke to each tank.

I can't answer your suspension travel question other than the fact that with 2 adults in the back the rears are on the bump stops, and the rears will bottom out on some potholes.

I've got a non sport auto car at the house slated for a LS.  Stock it has 16's.

I'll can check and see if 15s might fit when I get back next week. 

I'm just here to share this.

https://youtu.be/aDnP_rWu89c

tomtom already gave you all the same information I could. Although I never understood the "don't shut it off cold" thing with rotaries. I shut mine off cold all the time when I need to move it, and it has never given me an issue (knock on wood).

The early RX8's were programed to run rich during warmup. If you shut them off before they get out of that warmup cycle, you will flood them. I know several people that had this happen, and it happened to me when I picked up my car the first time. The later cars did not have as much of an issue, if any at all. There was a reflash that helped, but not all cars got it, and after that first experience I'd rather just let the car warm up. The deflooding procedure was not only annoying, but damages the cat and reduces the life of the plugs.

TheRX7Project said:

tomtom already gave you all the same information I could. Although I never understood the "don't shut it off cold" thing with rotaries. I shut mine off cold all the time when I need to move it, and it has never given me an issue (knock on wood).

The real problem is either if it's low on compression already or if you let it sit.  My 07 Rx-8 has fine compression (at least, it did about 5k ago when I had it tested by Mazda before the warranty ran out).  As long as I start it within a week or so of being moved, it seems fine.  If I move it a short distance and let it sit for a few weeks (like I accidentally did earlier this year*), it'll flood and be down compression on at least one face for a bit.

I normally just used the same method I used with my Rx-7s, which is if I have to move them cold, I'll let it idle about a minute, rev it up to 3k or so then shut it off while the engine is decelerating.  I've never had a problem doing that. 

EvanB said:

I believe that fitting 15" wheels requires control arm modification as well. Fidelity101 had a thread here at one point showing test fitting of 15" wheels and what was in the way. I assume you are thinking of rally tires. 

oh boy do I ever... and I like where this thread is heading...

1. You delete the OMP with the s1 or get an OMP adapter to run a separate tank with oil so you it pull pure 2 stroke oil instead of used engine oil allowing a much more even wear and better sealing purpose but don't expect your cat to last a long time and since its a used rx8 don't expect it last at all really... or when fueling up just add a little bit of 2 stroke oil to the gas. Be sure to redline the crap out of it like any rotary (once its properly warmed up)

2.  no idea but im sure I can measure one day, I may have some old shocks laying around that will make it easier but I'm no geometry wiz so i don't know how exactly to calculate that with the other suspension links. 

3A - Fronts: you may need to downgrade to base model auto trans front brakes which is fine because the rx8 has bigger brakes than an evo 8. Even with a BRAID large inner diameter wheel I was not able to get it to fit because the spread of the aux suspension arms is so wide that it hits the barrel. maybe a 0 offset wheel would work or spacers for that. RallyX should be okay but stage rally makes me worry some. Another idea is relocate these axillary links (I don't know what to car the other control arms that aren't the upper and lower ones) on the chassis side to narrow that spread.

3B - Rear: again a low offset wheel due to aux links and the lower ball joint on the knuckle or the lower part of the knuckle hits a rear wheel ID and you CAN grind it to make it but it seems sketch. I gave up pretty quick after that.

KLINKY rally team out of NZ have found some way and I wonder if its with coilovers changing the camber while giving ride height kind of deal? I've tried contacting them but no luck. Other idea would be for rallyX is just run 16s with some A/T tires. 

also when looking at any used rx8 (or any rotary ever for that matter) compression test is key. 

Re the two-smoke oil in the fuel - use either some synthetic two stroke oil that's designed for homeopathic dilution, or get the rotary-specific Idemitsu premix.

I got the latter for my RX8 and it certainly felt like it made a difference. For example, idle smoothed out after the second tank. It was always a "happy starter" even before I fed it the Idemitsu oil, so I can't really say how much of a difference it made in that regards. Oh, and that motor had a bit over 100k on it at that point.

If you haven't checked that already, the top tank on the radiator is notorious for leaking at the metal connector for the AST. That area is really hard to inspect without disassembly and ideally you want to catch it before it noticeably starts leaking coolant in that area.

I looked at an RX8 for a rallycross/icecross car. I looked at the base/AT brake swap and also options from the NC Miata. The S2 RX8 I was all excited about buying drove fine but came back with terrible compression numbers on both rotors.

I went for a BRZ which can take 15" Team Dynamics wheels over the stock brakes. 

But man the RX8 was fun to drive. I think the steering was better than the BRZ and it was also torquier throughout the midrange. Never thought I'd say that about the Renesis...

I don't know the answer for travel, but if that's a concern make sure that you don't buy coilovers with adjustable length bodies. They have to use a shorter shaft in order to provide the adjustment, which will cost you overall travel. You can choose where that travel is available, but you will lose somewhere.

If the RX8 can use NC Miata shocks (dunno how interchangeable they are), we can package something like 7.5" of shaft travel in the front. We actually have to limit it to 5". I'd have to look at the diagrams to see what the rears are like.

Wiscocrashtest said:

But man the RX8 was fun to drive. I think the steering was better than the BRZ and it was also torquier throughout the midrange. Never thought I'd say that about the Renesis...

I agree, the BRZ's engine sucks. I really don't like the character of it. I'm sure a hopped up toyota 2.5L would have been a better choice. The Renesis has a nice linear power delivery, pulls harder and makes much better noises. I actually think the BRZ's steering is better than the RX-8s, possibly the best out there, but we all have different preferences.

did an oil change yesterday on the s2 and at full droop it looked pretty sweet and plenty fine. The goal is when the rx7 rally car is no longer driveable the rx8 will become the new rally car so I have hopes that a proper shock/spring setup with some minor suspension/brake tweaks can get it stage worthy. Until I find a 2nd DD I wont take the rx8 to rallycross because after that happens things will break and it will be a slippery slope. 

On the care and feeding of the engine, there are a few basic rules:

1. Change the oil frequently.  The engine shears oil quickly, and dirty oil clogs the OMP / oil injectors.  I use Mobil 1 0W40 and drain and fill every 3,000 miles or 4 track hours, whichever comes first.  I change filters every 6,000 miles.

2. Keep the coils, wires, and plugs fresh.  The OE coils fail quickly--sometimes in under 10K miles.  Many of the later (after 2005) engine failures are due to the coils failing, causing fuel and oil to be dumped into the cat, which quickly clogs, and in turn kills the engine with back-pressure and heat.  (The cat part may not apply to you.)  BHR and SakeBomb sell ignition upgrade kits (or you can roll your own) that solve this problem.

3. Keep the stock airbox.  It is a CAI, and it is capable of flowing more air than a N/A engine needs.  The aftermarket options rob power, cause unstable idle, and allow enough sand ingestion to be harmful.

4. Premix is a good idea.  Any quality JASO FC or FD 2 cycle oil will work fine.  I use Lucas Semi-Synthetic 2 Cycle at a rate of 1 Oz / gallon on the track and 0.5 Oz / gallon on the street.  Others swear by Idumitsu.  There is no data I know of that proves how beneficial this may be, however.  It just seems like a good idea to lubricate more surface area inside the housings.

5. The shocks are not interchangeable with the MX-5.  Sway bars and end links are, as are brake duct spindle attachments.  I do not know the travel length.

for rally X I would remove the sway bars and as far as premix I always run anything TCW-3 and never give it much thought after that. I'm not sure what  JASO FC or FD 2 correlates to. Everyone swears by idemistu but probably because they like saying the name.