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How much does heat affect HP?

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Old 09-16-01 | 03:23 AM
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From: Bellevue, WA, USA
Question How much does heat affect HP?

I had my Stock 3rd Gen Dynod today and it came out with only
around 189HP@6000rpm and 166.8 Torque. Now those are
not great numbers and I was told I should be able to get
around 210. It was a hot day and I could hear the water
boiling in the radiator. How much does temperature affect
HP and why?
Old 09-16-01 | 01:43 PM
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LUV94RX7's Avatar
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I believe the "rule of thumb" is the input air/ fuel temperature should be as cool as posible. For every 5-10 F degrees cooler means 1% power increase. So if input air is 200 degrees and it can be reduced to 100 degrees you would get 10-20% power increase.

Correct me if I'm wrong

Ken
Old 09-17-01 | 03:53 PM
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If you only dyno'd at that much power, I'd say you have something wrong with your car. People dyno hot cars all the time and it doesn't usually hurt horsepower that drastically.

210 or more is normal with a stock car, even hot. Mike Putnam "optimized" his dyno with a totally stock car, took his power from 220rwhp to 255rwhp just by fanning and icing the car.

Wade
Old 09-17-01 | 07:31 PM
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From: Bellevue, WA, USA
Thanks for the info
Old 09-21-01 | 02:45 PM
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Most dyno figures that people get are corrected also. That takes into account ambient temps and adjusts the numbers accordingly. I would have to dig up my old notes, but I believe the DynoJet ASE average is 78F. So temps above that would have numbers corrected by a multiple above 1.00.

I hope that makes sense to everyone.
Old 09-21-01 | 08:44 PM
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I bet you have a boost leak or your second turbo is not going on at all. A stock RX-7 should pull around 220 RWHP. I pulled around 180 RWHP when my car was stock. My second turbo wasn't going on at all. I had no idea because I didn't have a boost gauge at the time. When I fixed my car, which was something really minor I put it on the dyno again and pulled 222 RWHP.

Try to post up your dyno run if you could. Also, if you don't have a boost gauge this is the time to get one to see if it is your turbos. Using a boost gauge can help you diagnose some types of boost problems.
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