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Thread: RX8 overheating; give up and get s2k?

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    Senior Member robburgoon's Avatar
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    Default RX8 overheating; give up and get s2k?

    The original goal here was to get something street legal to comfortably drive with A/C from SD to SJ and do track days at Laguna and Infineon while I'm up there. Something that is disposable, somewhat safe-ish, and isn't too similar to a spec miata. Affordable to operate is another goal.

    The RX-8 seemed to fit the bill well, $6K for 2004 120k, modern a pillars, roof, 185whp on 225s, FANTASTIC stock handling with only an alignment.

    The trouble is even with a cheap ebay racing rad ($130 shipped!) and factory oil coolers I'm hitting 230 on coolant in 57* temps. In warmer weather it's run 4 laps and shift at 8k instead of 9k then cool off. Also even after replacing wires, plugs, coils, I still get a flashing check engine light doing 80mph. This indicates misfire, but I can't feel any hesitation.

    To make matters worse, the rotary engine is a bit of a mystery as I'm not sure if it's the original one or not. Could be fine, could be about to go. Hard to tell.

    To fix the cooling issue, could try a koyo or something, or go to a multipass ($900 shipped). I've also heard about people repurposing a tranny cooler as a second radiator in the mouth and sending the heater hose return through it. ($100). Before you ask, radiator is already sealed and on WW and 65/35 water/coolant. Only issue is the rad cap doesn't fit amazingly tight.

    To fix the ignition issue, could try coils from mazda instead of ebay ($200?) or upgrade to corvette coils ($500 kit, $200 diy?). Not sure this is a real issue though since I don't feel any hesitation.



    OR......


    Could say f* it and get an S2K. Less disposable, less safe, but faster and less bull to deal with?

    A FI or mean NA miata could make sense but I'm not sure there's a way to be both comfortable for a 7 hour drive and safe-ish.

    E36 seems kinda old and wrench heavy.


    Ideas? It really is a shame since the RX-8 is quite wonderful on cold days, and there's nothing like sliding through the Rainey curve at laguna in a car you're willing to wreck. Can't do that in my vette.

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    You bought a cheap radiator and you don't know why your car is overheating on track?
    The deposed former Sheriff of trackHQ . . .

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    Senior Member robburgoon's Avatar
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    Quote Originally Posted by Richard EVO View Post
    You bought a cheap radiator and you don't know why your car is overheating on track?
    I could certainly put a $300 koyo or CSF in, but do you really feel that there is a 50-60* swing in a same thickness radiator?

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    Rob,

    Before punting I would talk to a rotary specialist shop. Mazdatrix (Signal Hill) or Tri Point (Chatsworth) are two that come to mind.

    Mark
    AiM Data and Video systems, Suspension Setup, Race car builds, support, and rentals. At your beck and call.

    Mark Nichols
    Iron Canyon Motorsports
    http://www.ironcanyonmotorsports.com

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    dirty smack talker hakeem's Avatar
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    Get one of these: Amazon.com: BLACKWORKS BWR MAZDA RX8 2004-2008 PERFORMANCE ALUMINUM RADIATOR: Automotive

    I used one on my 20B RX7 because it was laying around, haven't seen temps over 180*. And that's with a 20B making about 2-3x the power as you.

    People seem to have luck with these ignition coils: LS2 RX8 Ignition Upgrade - Engine and Accessories - RX8 - Mazda - Products

    Or PM me if you need referrals to someone who knows what they are doing (I have some experience here)
    tq3z, bawareca and Gian like this.

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    AROSC Comp. Director Slaysman's Avatar
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    My 88 RX-7 ran hotter than i was comfortable with. Up to 7,000 it wasn't too bad, but over that, the temp just took off. I did several things, and I no longer have problems.

    First step was to seal the intake track to the radiator. Much of the original factory ducting was gone, so I replaced it all with aluminum sheet. I also sealed up air passages into the engine compartment to help the air flow through the radiator.

    Second step was to slow down the water pump by changing out the pulleys. Smaller pulley on the crankshaft, larger pulley on the water pump.

    Third step was to graft some vents into the hood just aft of the radiator to help draw hot air out of the engine compartment.
    Terry Watson
    AROSC Competition Director

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    Senior Member robburgoon's Avatar
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    Quote Originally Posted by hakeem View Post
    Get one of these: Amazon.com: BLACKWORKS BWR MAZDA RX8 2004-2008 PERFORMANCE ALUMINUM RADIATOR: Automotive

    I used one on my 20B RX7 because it was laying around, haven't seen temps over 180*. And that's with a 20B making about 2-3x the power as you.
    $260 shipped? Sure, why not.

    I'll let you know how it goes.

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    Hakeem and Burgoon . . . Odd couple?
    Olitho, bellwilliam and Bueller like this.
    The deposed former Sheriff of trackHQ . . .

    2006 Porsche 997 Carerra Coupe 6-MT - daily driver
    1992 Honda (Acura) NSX 5-MT - classic investment I couldn't resist and occasionally drive
    2004 Honda S2000 AP2 6-MT - track day car
    2006 Mitsubishi Lancer Evolution IX MR 6-MT - when I need a backseat, 4-doors, or a real trunk, and still want to haul ass . . .

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    Senior Member Gian's Avatar
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    Quote Originally Posted by Slaysman View Post
    Second step was to slow down the water pump by changing out the pulleys. Smaller pulley on the crankshaft, larger pulley on the water pump.
    That's a big help. Cavitation and water pump are not good.
    That's not a Typo, I just can't spell no so well.

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    Administrator ucfbrett's Avatar
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    What Amir said. Why replace an entire car when you can replace a radiator you cheaped out on in the first place. Sometimes economizing is anything but.

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    Senior Member fatbillybob's Avatar
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    Quote Originally Posted by robburgoon View Post
    The trouble is even with a cheap ebay racing rad ($130 shipped!) and factory oil coolers I'm hitting 230 on coolant in 57* temps. In warmer weather it's run 4 laps and shift at 8k instead of 9k then cool off. Also even after replacing wires, plugs, coils, I still get a flashing check engine light doing 80mph. This indicates misfire, but I can't feel any hesitation.

    Ideas? It really is a shame since the RX-8 is quite wonderful on cold days, and there's nothing like sliding through the Rainey curve at laguna in a car you're willing to wreck. Can't do that in my vette.
    Why is 230 high? If the car is disposable why not run it hotter? Match the oil viscosity on track to oil viscosity stock on the freeway. Knock on wood I have raced by C5Z on the same motor it came with from the factory of 9 years + 7000 street miles. On track it lives at 280 with matched oil viscosity. I can get a big radiator and run it at 250 but the engine has run so well I just never bothered to get the big radiator all the other vette guys use. I had a discussion at Runoffs with the Mobil1 race techs about additive packages, racing oil viscosity, and engine life, and their eyes glazed over. They either did not get it, think I'm from mars, or a light bulb went on they needed to digest.
    bawareca likes this.

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    Senior Member fatbillybob's Avatar
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    If the motor was an otto cycle I would do static compression and leak it down then do a "running" compression test. If you have exhausted all other simple causes of misfire including fuel injectors the problem can be in the motor. I don't know anything about rotary and if there is a parallel to otto cycle motors.

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    Senior Member robburgoon's Avatar
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    Carl,

    230 is the coolant temp, not oil. Those apex seals and springs are rather flimsy looking. I don't think rotaries like heat.
    It's entirely possible I have ruptured a coolant seal in the engine, but reving the engine with the cap off doesn't seem to produce bubbles in the pressure tank, so I might be ok there. I did a compression test (button held down) and the needle bounced the same for all six chambers, so I'm at least even there.

    Brittany, the reason why I'm considering replacing the whole car is there's no guarantee that Amir's rad or even the $1K bigger radiator will do the trick. There's also the chance that the engine isn't long for the world, and if I have to throw $1.5K at the car to get it to behave and replace the engine for another $3K, well... it might turn out that the s2k was the better option all along.

    I'm happy to try Amir's radiator, I just hope that it's my radiator that's bad and not an airflow issue dominating the situation.

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    Rob, as you know, I pursued a street-legal track car for the same reasons as you but ended up with an S197 Mustang GT (2006 model). Aside from some high coolant temp issues (but no overheating) at WSIR during August, it's been rock solid. I may eventually end up swapping in a larger racing radiator but right now, using a lower temp T-stat and turning on the cooling fans at a lower coolant temp seems to have kept coolant temps in check. Brakes and suspension have been upgraded, too, but nothing crazy.

    If you decide to sell the RX-8 and start fresh, I'd look into the following cars for a semi-modern street legal track car:
    1. S197 Mustang GT (I'm biased and you don't strike me as a Mustang guy).
    2. E46 BMW M3
    3. S2000 - I love these cars but couldn't find one for a decent price that wasn't beat to death.
    4. ??? Toyobaru FRS/BRZ, If you can find an affordable priced used one???
    5. Early NC MX-5 (Miata). Bigger, more comfortable, and handles well out of the box. But you'll need a real roll bar!
    Last edited by MikeColangelo; 12-01-2014 at 12:32 PM.

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    Senior Member fatbillybob's Avatar
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    Quote Originally Posted by robburgoon View Post
    Carl,

    230 is the coolant temp, not oil.
    My bad reading comprehension! Try 15% antifreeze for the cold and make sure the radiator cap is up to spec. The only reliable caps I have found are the standard STANT looking caps. Just about every other cap style I have seen have had bad caps right out of the new box! I test every cap. Pressure in the system makes a huge difference as well as running as much water as you can. You can also send a coolant sample to Blackstone and they can test for combustion gasses in the coolant that will not show up as bubbles when reving your engine with cap open.

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    Rob -

    I don't think a good S2000 is in your price range (the only cars you want are '03 AP1, or '04 or '05 AP2). If you want to step up and spend what is required, you won't be disappointed . . .
    The deposed former Sheriff of trackHQ . . .

    2006 Porsche 997 Carerra Coupe 6-MT - daily driver
    1992 Honda (Acura) NSX 5-MT - classic investment I couldn't resist and occasionally drive
    2004 Honda S2000 AP2 6-MT - track day car
    2006 Mitsubishi Lancer Evolution IX MR 6-MT - when I need a backseat, 4-doors, or a real trunk, and still want to haul ass . . .

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    Rob, duh yes you should get an s2k Tho probably more $ than your s2k, but not sure how much exactly since Richard isn't telling

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    Kam
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    Oddly enough, I'm selling my '04 S2000... granted, it has 133K miles it does have good compression across the board and runs like a raped-ape. I'm also selling it cheaper than any '04 S2000 in the Southwest US

    To the overall question, yes, go with the S2000 and don't turn back.
    4.6lbs / whp -- 4lbs / bhp

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    Senior Member bellwilliam's Avatar
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    Now I think about it. There used to be a ton of rx8 on track days. But they are now rare sight. Wonder why ?

    I say s2000. New brake pads are all you need. Bring spare rotors.

    I am selling my 30k miles s2000 But it isnt a disposable Price.

    I also recommend a NC Miata. Quite reliable, I Almost bought one for $7k that came with torsen
    Supermiata S1, SuperMiata S2, Supermiata S3
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    I raced an RX8 in Grand-Am and designed probably the best droo-in solution 3-pass radiator with Ron Davis. I would not go with an off the shelf Koyo or other brand. Either go all out with the best radiator you can, and oil coolers, otherwise go with the S2K. RX8s handle so well and I really like them but heat is their biggest issue (and fuel economy).

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