Fact Or Fiction: Do Electrical Systems Decrease Power?

[ctrlraven]

http://www.importtuner.com/tech/impp_1008_does_the_electrical_ system_decrease_power_fact_fic tion/index.html

[Joe Walsh]

In a naturally aspirated Subaru 2.5i, 11.5whp might be a small price to pay for comfort.

When you are only putting 114 whp down...I'd say 11.5 whp is a HUGE loss!

But with a 10.1-percent loss in power translating to over 50whp in our RWD, 450whp 370Z (June, '10 cover)...
we may be willing to suffer the heat!

WRONG!

You can't use a percentage loss from an A/C compressor and an alternator for a low HP car, then apply it to a high HP car to come up with 50 whp lost!....:eek:

If that was a 450 whp Subie with the exact same alternator and A/C compressor it would lose........11.5 HP.

The guy who wrote that should know better.

[RR|Suki]

In a naturally aspirated Subaru 2.5i, 11.5whp might be a small price to pay for comfort.

When you are only putting 114 whp down...I'd say 11.5 whp is a HUGE loss!

But with a 10.1-percent loss in power translating to over 50whp in our RWD, 450whp 370Z (June, '10 cover)...
we may be willing to suffer the heat!

WRONG!

You can't use a percentage loss from an A/C compressor and an alternator for a low HP car, then apply it to a high HP car to come up with 50 whp lost!....:eek:

If that was a 450 whp Subie with the exact same alternator and A/C compressor it would lose........11.5 HP.

The guy who wrote that should know better.


I left my AC on one run at the track a couple weeks ago when it was 90* out, and it makes me not agree about the loss being static. I lost a good 3mph that run vs. the one before it. Still ran a 12.1 or something.

[CBT]

I left my AC on one run at the track a couple weeks ago when it was 90* out, and it makes me not agree about the loss being static. I lost a good 3mph that run vs. the one before it. Still ran a 12.1 or something.
Low low 12's with the A/C on!:bows:
And I thought I was hot stuff this morning barking the tires with the A/C on.

[martyo]

I left my AC on one run at the track a couple weeks ago when it was 90* out, and it makes me not agree about the loss being static. I lost a good 3mph that run vs. the one before it. Still ran a 12.1 or something.

I believe that the clutch on the AC unlocks at WOT, so I am not sure how valid that test is.

Now, as far as even sitting in the staging lanes with the AC on, that is a bad idea. The condensor drips water and that water gets on the track. I am sure you know where I am going with this....

[Egon Spengler]

Marauders have A/C??? I will have to try it. I thought I saw A/C on my dash, but whenever I press it, hot azz air comes out... hmmmmm

[Joe Walsh]

I left my AC on one run at the track a couple weeks ago when it was 90* out, and it makes me not agree about the loss being static. I lost a good 3mph that run vs. the one before it. Still ran a 12.1 or something.

The loss isn't static based on engine rpm...the highest loss is at the highest rpm the engine attains.
The loss is static based on a given vehicle.
That vehicle's alternator and A/C compressor use a certain amount of HP to run at that vehicle's maximum engine rpm.
Regardless of whether that vehicle's engine makes 100, 200, 300 or 400 HP, the alternator & AC HP loss is the same.
It is a higher percentage loss for a 100 HP engine.

Marty, they said that they found a way to bypass the WOT A/C cut-out feature on the Subie.

Really it should be looked at as a loss of torque. (HP = torque x rpm/ 5252)
It takes a certain amount of torque to turn the alternator and the A/C compressor.
As the engine's rpms increase the torque required to turn the alternator/A/C compressor stays the same, but the HP loss gets greater.
In their test the Subie used 12.2 ft/lbs of torque = 11.5 whp
It even looks like the A/C compressor turned off anyway...look at the yellow torque curve....@5,300 rpm it stops dropping and actually rises.

[FordNut]

The loss isn't static based on engine rpm...the highest loss is at the highest rpm the engine attains.
The loss is static based on a given vehicle.
That vehicle's alternator and A/C compressor use a certain amount of HP to run at that vehicle's maximum engine rpm.
Regardless of whether that vehicle's engine makes 100, 200, 300 or 400 HP, the alternator & AC HP loss is the same.
It is a higher percentage loss for a 100 HP engine.

Marty, they said that they found a way to bypass the WOT A/C cut-out feature on the Subie.

It's easy, there is a parameter in the tune...

[martyo]

Marty, they said that they found a way to bypass the WOT A/C cut-out feature on the Subie.


I can not look at the link -- it is banned on my network.

[RR|Suki]

I believe that the clutch on the AC unlocks at WOT, so I am not sure how valid that test is.

Now, as far as even sitting in the staging lanes with the AC on, that is a bad idea. The condensor drips water and that water gets on the track. I am sure you know where I am going with this....

Oh I know, it was more of a brain fart than anything else. A/C had been on in the pits, I got distracted, put my helmet on and didn't notice it was on.
P.S. I part throttle 1st and the A/C off delay function in my tune is off . . . I should prob change that >_>


The loss isn't static based on engine rpm...the highest loss is at the highest rpm the engine attains.
The loss is static based on a given vehicle.
That vehicle's alternator and A/C compressor use a certain amount of HP to run at that vehicle's maximum engine rpm.
Regardless of whether that vehicle's engine makes 100, 200, 300 or 400 HP, the alternator & AC HP loss is the same.
It is a higher percentage loss for a 100 HP engine.

Marty, they said that they found a way to bypass the WOT A/C cut-out feature on the Subie.

Really it should be looked at as a loss of torque. (HP = torque x rpm/ 5252)
It takes a certain amount of torque to turn the alternator and the A/C compressor.
As the engine's rpms increase the torque required to turn the alternator/A/C compressor stays the same, but the HP loss gets greater.
In their test the Subie used 12.2 ft/lbs of torque = 11.5 whp

Certainly the % of loss would be different, I'm not with them on that. I just think that it could have more effect on say our cars higher in the HP. If your Alt. cuts out at WOT still in the tune for example, and the A/C was still on, with a blower I think that would have a lot more effect on power than it would with an N/A car. Plus with my situation I'm sure the A/C compressor kicking on also caused some belt slip. . . A side effect sure, but still a part of the A/C being on :D

[Joe Walsh]

They used the too high percentage loss because it will give the Ricers another excuse when they lose a race...

"Ahhhh Dude!...you beat my Civic because I had my stereo blasting and the A/C cranked to max!...
Otherwise....I would have killed you!" :shake:......:rolleyes:....... :blah: