Why dyno days & 100+degree weather & 91 octane don't mix.
06-23-2003, 09:26 AM
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Why dyno days & 100+degree weather & 91 octane don't mix. Had a club dyno day where about 20 of us hopped on a the dyno for some pulls. Only bad thing was is was over 100 degrees that day, and of course we only have 91 octane gas.
Well, the results were: EVERY bolt on car dynoed about 15rwhp shy of what they normally dyno in cooler weather, and my car was shy 20rwhp of what it normally dynos.
Although most of the cars were dialed with their A/F ratio, I'd say that 1/3 of the cars that went were pinging badly...some of which had a semi-safe 12.6-12.8:1 A/F ratio. Mine was all the way up to 13.4:1 or so, but no pinging here
Thanks to the great state of AZ for giving us the shittiest gas while we live in the hottest state in the US
The correction factor seemed appropriate for the day, but I had no idea the heat would kill dyno #'s that bad!
I know our cars turn down the timing depending on the intake air temp, but I a few degrees of lost timing shouldn't have this much of an effect.
Well, the results were: EVERY bolt on car dynoed about 15rwhp shy of what they normally dyno in cooler weather, and my car was shy 20rwhp of what it normally dynos.
Although most of the cars were dialed with their A/F ratio, I'd say that 1/3 of the cars that went were pinging badly...some of which had a semi-safe 12.6-12.8:1 A/F ratio. Mine was all the way up to 13.4:1 or so, but no pinging here
Thanks to the great state of AZ for giving us the shittiest gas while we live in the hottest state in the US
The correction factor seemed appropriate for the day, but I had no idea the heat would kill dyno #'s that bad!
I know our cars turn down the timing depending on the intake air temp, but I a few degrees of lost timing shouldn't have this much of an effect.
06-23-2003, 10:57 AM
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Re: Why dyno days & 100+degree weather & 91 octane don't mix. how did she dyno anyway? Im just glad we have 93 out here in Va. Or this 11:1 CR would be pinging like a **** i bet
damn these TEA heads pull there **** off though! SHEW
damn these TEA heads pull there **** off though! SHEW
06-23-2003, 11:29 AM
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Re: Why dyno days & 100+degree weather & 91 octane don't mix.
why can't you buy 93 octane where you are?
06-23-2003, 12:08 PM
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Re: Why dyno days & 100+degree weather & 91 octane don't mix.
why can't you buy 93 octane where you are?
06-23-2003, 12:31 PM
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Re: Why dyno days & 100+degree weather & 91 octane don't mix.
why can't you buy 93 octane where you are?
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06-23-2003, 12:43 PM
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Re: Why dyno days & 100+degree weather & 91 octane don't mix.
how did she dyno anyway? Im just glad we have 93 out here in Va. Or this 11:1 CR would be pinging like a **** i bet
damn these TEA heads pull there **** off though! SHEW
damn these TEA heads pull there **** off though! SHEW
First pull was 407rwhp/370rwtq
Second pull was a 413rwhp/376rwtq
The last time I dynoed at this same shop in cold weather, I put down 433.9rwhp.
Maybe I could have eeked out 418rwhp or so on a 3rd pull, but it wasn't worth it to me since I was running at 13.4-13.5:1 A/F.
The car did sit around for 2.5 hrs before hitting the dyno, so maybe the engine cooling down had an effect. I dunno.
Since I dynoed 433.9rwhp, a lot of things changed, so its really hard to get an exact idea of how much the heat played a factor in the dyno #'s. I'm going off of the differences on everyone else's cars.
The only things done to my car were 4.11 gears (up from 3.73's) and Yella Terra Rockers. I'm sure those two mods' horsepower effects cancelled each other out. I also had fresh oil and 275/40/17 tires on the car for the 433rwhp , whereas on this dyno, the oil in the car was on its last leg, and the 315/35/17's I put on the car weigh 7lbs more than the 275's.
Too many varibles for me to try to compare both dyno runs.
I'm sure they all played a factor, but I'm just more interested in getting my car dialed in right for this summer heat
13.4-13.5:1 is too much when its 110 degrees outside but overall I'd say the heat did a number on everyone.
06-23-2003, 03:27 PM
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Re: Why dyno days & 100+degree weather & 91 octane don't mix.
Sure does show that dyno numbers mean *** for the most part 
Cheers,
Chris
Cheers,
Chris
06-23-2003, 05:37 PM
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Re: Why dyno days & 100+degree weather & 91 octane don't mix.
why can't you buy 93 octane where you are?
06-24-2003, 02:51 AM
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Re: Why dyno days & 100+degree weather & 91 octane don't mix.
why can't you buy 93 octane where you are?
Maybe it has to do with the strict emissions in California? I dunno I was just passing on what I heard, could be wrong about it all.
06-24-2003, 07:24 AM
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Re: Why dyno days & 100+degree weather & 91 octane don't mix. I beleive higher octane burn slower. I know race gas burns slower than pump gas.
I hope your theory on hotter days produce lower dyno number is right, I just had a head and cam job done to my 01 Vette and felt like it should have had 420+ but it only got 414 rwhp. I dynoed it in the middle of a 98 degree afternoon.
I hope your theory on hotter days produce lower dyno number is right, I just had a head and cam job done to my 01 Vette and felt like it should have had 420+ but it only got 414 rwhp. I dynoed it in the middle of a 98 degree afternoon.
06-24-2003, 07:45 AM
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Re: Why dyno days & 100+degree weather & 91 octane don't mix. It is hot here 90 percent of the year.. Most everyone dyno in 90 plus degrees here.. It has never seemed to affect my dyno.. I have always dyno'd over 415rwhp depending on the cam.. Looking at your current dyno #'s I can see why your mph is not reflecting 440rwhp.. Just kidding..
Just kidding.. 
06-24-2003, 08:09 AM
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Re: Why dyno days & 100+degree weather & 91 octane don't mix.
how did she dyno anyway? Im just glad we have 93 out here in Va. Or this 11:1 CR would be pinging like a **** i bet
damn these TEA heads pull there **** off though! SHEW
damn these TEA heads pull there **** off though! SHEW
First pull was 407rwhp/370rwtq
Second pull was a 413rwhp/376rwtq
The last time I dynoed at this same shop in cold weather, I put down 433.9rwhp.
Maybe I could have eeked out 418rwhp or so on a 3rd pull, but it wasn't worth it to me since I was running at 13.4-13.5:1 A/F.
The car did sit around for 2.5 hrs before hitting the dyno, so maybe the engine cooling down had an effect. I dunno.
Since I dynoed 433.9rwhp, a lot of things changed, so its really hard to get an exact idea of how much the heat played a factor in the dyno #'s. I'm going off of the differences on everyone else's cars.
The only things done to my car were 4.11 gears (up from 3.73's) and Yella Terra Rockers. I'm sure those two mods' horsepower effects cancelled each other out. I also had fresh oil and 275/40/17 tires on the car for the 433rwhp , whereas on this dyno, the oil in the car was on its last leg, and the 315/35/17's I put on the car weigh 7lbs more than the 275's.
Too many varibles for me to try to compare both dyno runs.
I'm sure they all played a factor, but I'm just more interested in getting my car dialed in right for this summer heat
13.4-13.5:1 is too much when its 110 degrees outside but overall I'd say the heat did a number on everyone.
Sorry to hear things didn't go exactly to plan, good numbers for those conditions though, your example is one of the reasons why I mentioned a while ago when people represent dyno numbers in SAE to also include the correction factor for the day so everyone including the owner can get a better picture of what's going on, but it wasn't well recieved for some reason? SAE correction dosen't adjust perfectly especially with poor atmospheric conditions.
Better luck in cooler weather
.Joe.
06-24-2003, 08:48 AM
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Re: Why dyno days & 100+degree weather & 91 octane don't mix.
These are SAE Corr. numbers?
It was 103 degrees, 38 degrees of dewpoint, and elevation about 1350-1500ft.
That being said should my CF factor have been 1.07?
Since everyone else was down 15-17rwhp on average as well, I don't feel as bad for my low dyno numbers this go around, but just in case, I'm going to do a leakdown/compression test just to make sure my engine isn't enacting revenge for all my 7000rpm jaunts.
06-24-2003, 11:52 AM
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Re: Why dyno days & 100+degree weather & 91 octane don't mix. You and Vince still got some good hp #s. I have the TEA 1.5s with a 224 581 112 cam and longtubes throttlebody and a pully and only got 414hp corrected on my 2001 C5. Thats what I was hoping for because I dynoed on a very hot day also.
