By-pass question...
Thread Starter
Melting Slicks
Joined: Oct 2006
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By-pass question...
How much HP would be gained by using a smaller belt and by-passing the a/c ? It's an old hp trick from years ago when there was several belts, but I haven't heard much about it in the serpentine era, only pully swaps. I took the a/c out of my 2000 TA and it gained 19rwhp and lost several pounds. Now , I'm not proposing an a/c removal, but swapping the belts before track runs, now that could be a dooable thingy if the hp was enough......
Drifting
Joined: Jul 2005
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From: az
it wouldn't work with a shorter belt / by pass configuration, unless you remove the ac and put in a idle pulley in it location. if you take the belt off and spin the ac pulley you will notice there isn't much of a drag. of course, i am assume you already turn off the ac before you make your pass.
Le Mans Master
Joined: Feb 2006
Posts: 5,762
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From: Chandler Arizona
How much HP would be gained by using a smaller belt and by-passing the a/c ? It's an old hp trick from years ago when there was several belts, but I haven't heard much about it in the serpentine era, only pully swaps. I took the a/c out of my 2000 TA and it gained 19rwhp and lost several pounds. Now , I'm not proposing an a/c removal, but swapping the belts before track runs, now that could be a dooable thingy if the hp was enough......
Thread Starter
Melting Slicks
Joined: Oct 2006
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No, no...read it again...lol....it lost several pounds, not several hundred. I had the TA in the shop to place the battery in the pass.rear, have the a/c and all connections removed, gatorback belt and then they dyno'd it, and it pulled 19 extra rwhp and if I remember correctly, about 8 more ft lbs torque over my previous runs a few weeks earlier....no joke.The car was s/c'd if that'd make a difference in gains when compared to a stocker with a/c removal.You are correct about the weight savings, I think it was very close to your 70-80 lbs.
Le Mans Master
Joined: Feb 2006
Posts: 5,762
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From: Chandler Arizona
No, no...read it again...lol....it lost several pounds, not several hundred. I had the TA in the shop to place the battery in the pass.rear, have the a/c and all connections removed, gatorback belt and then they dyno'd it, and it pulled 19 extra rwhp and if I remember correctly, about 8 more ft lbs torque over my previous runs a few weeks earlier....no joke.The car was s/c'd if that'd make a difference in gains when compared to a stocker with a/c removal.You are correct about the weight savings, I think it was very close to your 70-80 lbs.
As far as the power. The thing I have a problem with is if the A/C was really absorbing 19 rwhp while it was not being used, where would all the heat go? All you have to spin is the pulley with the electric clutch disengaged. I don't know why you made another 19/8 but I believe you (I've always really respected your posts!).
One more thing, I can't do this, I live in Phoenix. Man, that A/C sure felt good this morning after walking 18 holes in 100 degree heat!
Thread Starter
Melting Slicks
Joined: Oct 2006
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Man, I'm getting senile!!!! Sorry, I don't know why I saw the "hundred" that wasn't there. Anyway, I think you could lose around 75 pounds if you got rid of all the hardware, brackets, and hoses.
As far as the power. The thing I have a problem with is if the A/C was really absorbing 19 rwhp while it was not being used, where would all the heat go? All you have to spin is the pulley with the electric clutch disengaged. I don't know why you made another 19/8 but I believe you (I've always really respected your posts!).
As far as the power. The thing I have a problem with is if the A/C was really absorbing 19 rwhp while it was not being used, where would all the heat go? All you have to spin is the pulley with the electric clutch disengaged. I don't know why you made another 19/8 but I believe you (I've always really respected your posts!).
btw, I keep telling the wife I wanna move out west....triple digits aren't so bad as long as the humidity isn't thick as it is here...I swear at times it looks to be raining but it's not....crazy
Le Mans Master
Joined: Feb 2006
Posts: 5,762
Likes: 4
From: Chandler Arizona
Thanks man, it amazed me that it did gain so much, but it was on the same dyno as the previous runs and by the same operators. The only other variable was the belt swap, whereas I used a stock type belt(different size of course) with the s/c until I did the a/c removal, then went to goodyear gatorbacks....maybe I was losing some hp due to slippage, but the boost always stayed tight between 6.5/7.0 psi. Anyways, back to topic, I guess there isn't much to be seen doing this in a more modern car, so it's not worth the hassel. I had to ask, though...
btw, I keep telling the wife I wanna move out west....triple digits aren't so bad as long as the humidity isn't thick as it is here...I swear at times it looks to be raining but it's not....crazy
btw, I keep telling the wife I wanna move out west....triple digits aren't so bad as long as the humidity isn't thick as it is here...I swear at times it looks to be raining but it's not....crazy
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Melting Slicks
Joined: Jun 2006
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I've heard that modern A/C units pull very little hp--even when running, so I'm amazed you got that gain on a T/A! 
Maybe it was too tight or something else was affecting your rwhp. The idea of an electric a/c compressor is a good one. Wonder when they'll get one that is product ready?
Maybe it was too tight or something else was affecting your rwhp. The idea of an electric a/c compressor is a good one. Wonder when they'll get one that is product ready?
Burning Brakes
Joined: Mar 2006
Posts: 906
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From: SF Bay CA
Id be surprised if it netted 1+whp, unlike the alternator and PS pump, when the AC is not turned on the magnetic clutch pulley on the front of the AC compressor is completely disengaged from turning the compressor and is basically just a free-wheel idler pulley, when you turn on the AC the magnetic clutch pully locks and spins the compressor.
Safety Car
Joined: Dec 2004
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From: stafford country, va. Avatar: Me on turn 3 @ Bristol (The World's Fastest Half-Mile)
and some say there isn't any gain when doing a heater core by-pass.
the a/c pulley does spin pretty freely when not engaged but then again the power steering pulley doesn't take much to spin by hand either.
i suspect you may see some gains from the smaller belt, less tension required, but i really don't think it would be worth it, unless you're gonna start making the car a pure track car. at that point you'd be shaving all sorts of weight, removing anything that doesn't help performance, seats, a/c system, carpeting, interior trim, etc. etc.
the a/c pulley does spin pretty freely when not engaged but then again the power steering pulley doesn't take much to spin by hand either.
i suspect you may see some gains from the smaller belt, less tension required, but i really don't think it would be worth it, unless you're gonna start making the car a pure track car. at that point you'd be shaving all sorts of weight, removing anything that doesn't help performance, seats, a/c system, carpeting, interior trim, etc. etc.
Thread Starter
Melting Slicks
Joined: Oct 2006
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you may be correct, it's a possibility, for sure. I just never saw a decrease in psi from the blower with the old belt, maybe it took less HP to drive it(the s/c) after a/c removal and freed up some power. Who knows, but I did see the gains then for whatever reason and was just wondering if it was worth while on a C6, now that it's been clarified, I'm good with the answers .
Le Mans Master
Joined: Jun 2003
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From: 2007 Nat'l Corvette Challenge 11.50 index Champ. New Jersey
Doesn't the computer shut down the A/C @ wide open throttle anyway, even if it's on? Not sure about bypassing the a/c for RWHP gains. Probably not much, as these engines run pretty darned efficient.
I used to do that in my 91 Mustang LX by the way though.
Were the weather conditions similar on the 2 dyno pulls, & was the car cooled down for both pulls? This could vary the results.
I used to do that in my 91 Mustang LX by the way though.
Were the weather conditions similar on the 2 dyno pulls, & was the car cooled down for both pulls? This could vary the results.
Thread Starter
Melting Slicks
Joined: Oct 2006
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Doesn't the computer shut down the A/C @ wide open throttle anyway, even if it's on? Not sure about bypassing the a/c for RWHP gains. Probably not much, as these engines run pretty darned efficient.
I used to do that in my 91 Mustang LX by the way though.
Were the weather conditions similar on the 2 dyno pulls, & was the car cooled down for both pulls? This could vary the results.
I used to do that in my 91 Mustang LX by the way though.
Were the weather conditions similar on the 2 dyno pulls, & was the car cooled down for both pulls? This could vary the results.
Drifting
Joined: Jul 2005
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From: az
Race Director
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From: Carlsbad Ca
Le Mans Master
Joined: Aug 2000
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From: Las Vegas NV
Regarding AC compressor cutout at WOT:
I can't say for certain about the C6, but the C5 (and all my other vehicles), I've held WOT long enough to feel the air from the AC vents getting warm, thus indicating the AC compressor had been disengaged. I would think someone here with a C6 has probably experienced the same thing? Anyone? Bueller?
I can't say for certain about the C6, but the C5 (and all my other vehicles), I've held WOT long enough to feel the air from the AC vents getting warm, thus indicating the AC compressor had been disengaged. I would think someone here with a C6 has probably experienced the same thing? Anyone? Bueller?
Le Mans Master
Joined: Aug 2004
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From: Monroe Township New Jersey
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I don't know about the manual but if you look at the VCM editor in the system file under A/C there is a disable RPM and disable TPS setting. The stock setting for the RPM is 7,083 RPM and the TPS is set for 200%
We know from data logging that the fuel cut off is set at 6,700 RPM and the max TPS is 88% ......... So with the stock settings the AC will not be disabled.
Now if you change the stock settings in the system file that is another story
Last edited by Tommy D; Jun 25, 2007 at 11:36 PM.
Drifting
Joined: Jul 2005
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From: az
I don't know about the manual but if you look at the VCM editor in the system file under A/C there is a disable RPM and disable TPS setting. The stock setting for the RPM is 7,083 RPM and the TPS is set for 200%
We know from data logging that the fuel cut off is set at 6,700 RPM and the max TPS is 88% ......... So with the stock settings the AC will not be disabled.
Now if you change the stock settings in the system file that is another story
i believe 8850 (it could have been someone else) that changed the setting to something alot lower and redata log, again. it didn't shut off under wot.