04-RX8 Overheating & Loss of Power

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04-RX8 Overheating & Loss of Power

Postby RXFEVER » Mon May 09, 2016 4:07 pm

Hi Brian, I hope you can give me some hints so I can solve my problem. Last weekend I raced my 2004 RX8 at Auto Club Speedway in Fontana. Initially the car was running fine, the day was perfect, in the upper 60's lower 70's. After my first two sessions the engine starts to run too hot (water), about 220 - 230 but with the oil temperature about 200 - 210. I believed that this situation was responsible for the loss of power mostly during acceleration in the long straight section of the track. I couldn't rev the engine pass 5000 - 6000 rpm's. The thing is that after the engine temp drop's back to the 200 range, basically by the time I pass the straight way and the banked turn to get into the inner track section the power was already restored. This is really frustrating, since I have been working hard on the modifications to enjoy my car.

Modifications: the engine is stock, so far, air compressor eliminated, aftermarket intake, header and open pipe up to the cat-back, new ignition coils, Ultra ignition wires, aftermarket water pump :?:, big KOYO radiator & radiator cap, silicone hoses, thermostat eliminated, throttle body coolant hoses-bypassed, new racing beat oil cooler SS braided hoses, singular Motorsports hood louvers, racing beat PCM Flashing V2, racing spark plugs. I disassemble and clean the lower intake, valves and replace the APV actuator. One thing, I never change the fuel injectors and the fuel pump.

I am not sure, but I believe that the engine is running too lean, and I said this because the S.S. exhaust pipe tips are changing in color and the interior of the pipe is clean with a brownish dust, not dark in color as in a normal combustion. Should I modify the thermostat case and close the by-pass to improve the flow? Need some guidance from the experts. Thanks
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Re: 04-RX8 Overheating & Loss of Power

Postby Brian » Mon May 09, 2016 7:59 pm

My first guess was melted cat...but sounds like no converter in your exhaust right?
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Re: 04-RX8 Overheating & Loss of Power

Postby RXFEVER » Tue May 10, 2016 8:42 am

Brian wrote:My first guess was melted cat...but sounds like no converter in your exhaust right?


That's correct, there is no cat-converter in the car..
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Re: 04-RX8 Overheating & Loss of Power

Postby Brian » Tue May 10, 2016 9:03 am

Sorry, without laying hands on the car cannot say more. Nearest good RX service to Simi valley that I know of is MazdaTrix in Signal Hill. If somebody knows a good shop closer to Simi Valley please list the suggestion.
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Re: 04-RX8 Overheating & Loss of Power

Postby RXFEVER » Tue May 10, 2016 9:40 am

Brian wrote:Sorry, without laying hands on the car cannot say more. Nearest good RX service to Simi valley that I know of is MazdaTrix in Signal Hill. If somebody knows a good shop closer to Simi Valley please list the suggestion.


That's OK. Questions?? Did you run the RX8's without thermostat? and Did you modify the thermostat housing by closing the internal bypass?
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Re: 04-RX8 Overheating & Loss of Power

Postby Brian » Tue May 10, 2016 9:41 am

We ran it with thermostat, had no issues with that part.
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