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Discussion Starter · #1 ·
This may be a perception issue, but SOTP, it REALLY feels like my Zee is faster some days, and slower others. Just yesterday, I was getting on it, and didn't get the "whoa" effect that I usually get. 1st and 2nd just didn't seem as punchy as usual - I shifted perfectly and quickly at 6000, and it just didn't pull like it usually does. It was pretty hot out, so I'm thinking maybe that had something to do with it since cold air is always better for HP.

So, I pose this question: what factor(s) affect HP/Torque (obviously aside from any bolt-ons or engine mods)? Also, how much HP/Torque do you think is gained/lost by each factor. Here are just a few of my perceptions... Remember, I'm not talking about traction issues, or actually putting the HP down.. I'm talking about an actual SOTP feeling of HP gain/loss.

Cold weather: HP/Torque gain, feels more powerful.
Hot weather: HP/Torque loss, feels a little drained.
A/C on: HP/Torque loss, feels drained.
Low/high altitude: I know this affects HP/Torque, but I'm not sure to what degree... it isn't a factor where I live, so that can't be it for me.
Car just turned on and driven: Feels faster
Car already warm, & driven more than 10 miles: Feels slower
Full tank: Feels faster
Empty tank: Feels slower
Fat person in passenger seat: Feels slower. (yah, I'm kidding) :lol:


Are these at all accurate? Did I miss anything? Something must be causing this change in SOTP HP/Torque day to day!! :-?
 

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Car will not feel as fast on a hot day. The hotter the IAT, the less power the engine will make. Simple physics!
Altitude really hurts power. (ask me how I know?) to the tune of 3% per 1000 ft. That equals minus 22.5% where I live.
:(
 

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IMO the ones listed below are incorrect perceptions. :z:

Car just turned on and driven: Feels faster
Car already warm, & driven more than 10 miles: Feels slower
Full tank: Feels faster
Empty tank: Feels slower
 

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Full tank, at about 10# per gallon, should ADD weight and, therefore, SUBTRACT performance (greater overall curb weight-100# generally equals a 1/10 in the 1/4)...if a low tank still properly feeds the fuel pump and isn't too low a level, causing starvation...EXCEPT...
If you have added weight to the nose (supercharger/TT, intercoolers etc., more weight in the back (full tank) may actually help weight distribution/transfer and traction...
As to "operating temp", what exactly is YOURS? Too high costs power...
 

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Discussion Starter · #5 ·
PowerPro01 said:
Full tank, at about 10# per gallon, should ADD weight and, therefore, SUBTRACT performance (greater overall curb weight-100# generally equals a 1/10 in the 1/4)...if a low tank still properly feeds the fuel pump and isn't too low a level, causing starvation...EXCEPT...
If you have added weight to the nose (supercharger/TT, intercoolers etc., more weight in the back (full tank) may actually help weight distribution/transfer and traction...
As to "operating temp", what exactly is YOURS? Too high costs power...
My engine temp usually reads ~195 degrees. I don't know if it's the recent high temps or what, but something has caused a noticeable decrease in power. I haven't added or taken anything away from the engine, so it must be an outside factor. Do you know how much HP the A/C robs, if any? It def feels slower when the a/c is on...

It's pretty ironic, I feel like it has a lot more power to offer when it's cold out, but I can't put that power properly to the wheels because of really poor traction on the cold surfaces, so it never gets translated into HP at the wheels anyway. :mad:

And wouldn't an engine that's just been started be considerably colder, along with the air in the engine bay, hence, producing more HP... in relation to an engine that's been running for a little while, which would be inversely hotter, with a lot more hot air under the hood produced from the warmed-up engine ? I thought that assertion was logical... ;)


:cheers:
 

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What factors affect HP/torque????

The more air+fuel you can ingest and ignite, then the more torque you will produce. The more torque you produce, the more HP you make. More air+fuel can be obtained anywhere from colder air to forced induction.

HP = (T x RPM)/5252 [T in ft-lbs]

Of course, you can also increase T by stroking. And you can increase HP by more RPMs.

Lots of factors affect T and HP. :thumb:
 

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Z06 Rocket said:
Cold weather: HP/Torque gain, feels more powerful.
Hot weather: HP/Torque loss, feels a little drained.
A/C on: HP/Torque loss, feels drained.
Low/high altitude: I know this affects HP/Torque, but I'm not sure to what degree... it isn't a factor where I live, so that can't be it for me.
Car just turned on and driven: Feels faster
Car already warm, & driven more than 10 miles: Feels slower
Full tank: Feels faster
Empty tank: Feels slower
Fat person in passenger seat: Feels slower. (yah, I'm kidding)
Your hot/cold/elevation effects are all wrapped up into density-altitude. The denser the air, the more power you have. Both elevation and temperature (for obvious reasons) effect density. Drive around at 10,000 feet ASL if you want your car to feel like a pig.

Your A/C effect is that it takes engine power to drive the compressor.

Your fuel tank and fat passenger effects are just that the mass of the car is increased, and F=MA, so A=F/M.

novetteyet
 
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