How much do gears really effect dyno numbers??

Blakers01GT · Sep 13, 2003

reading the thread about the pro chamber giving that guy crazy numbers was wierd. but it makes me think, he didn't have gears, and alot of guys come on here posting really good numbers after a few bolt on's, mid pipes and whatever but they don't have gears. I know it affects the HP on the dyno, but how much? lets say a GT puts down 230RWHP and 270RWTQ with stock gears, then lets say i throw some 373's or 410's on there, how much HP will i lose on they dyno? I understand why you lose it because the gears do not let the engine wind out but anyone have any proof or specs on how much you lose? thanks.

Blake

Dark Knight GT · Sep 13, 2003

This is going to become one of the biggest technical threads of your life when guys like TrinityGT, Triblkcobra, mrvax, and white99GT see this. Thats not bad though. Its just gonna get long so I figured Ide warn you.

Anways, its impossible to tell you how much rwhp is lost from a gear change. The average I hear is 5-8rwhp. Some maybe higher. Depending on the car and what steep of gear changer were talking. Its all physics in motion. I cant give the mathematical formulas for explanation. However, I do know the physical explanation in terms of centrifical force flow. To avoid getting technical, just think about the gears. The steeper the gear, the less the splines. The less the splines, the more power is lost across the gap of theese splines as the engery trasnfers from the one spline to the next across the ring & pinion gears in a centrifical manner. The power is needed to turn the gears but the further the gap in splines, the more the loss of power. Many people would assume then that steeper gears would slow you down just by that explanation. Not so. Remember, although power is being lost there are still less splines to wind. Therefore, the less time is needed for rotation of the ring and gear pinions. Thats why you gain in acceleration even though you lost rwhp. Thats just a basic explanation though. Im sure other guys here will have more " in-depth " explanations.

Sam98 · Sep 14, 2003

The dyno takes the gearing into consideration, so unless the gears are adding resistance to the drivetrain you aren't going to see anything.

Dark Knight GT · Sep 14, 2003

Sam98 said:
The dyno takes the gearing into consideration, so unless the gears are adding resistance to the drivetrain you aren't going to see anything.

Hmmm. Ive seen guys on here before who had their cars put on the dyno after a gear change and they claimed they lost rwhp. I guess it does depend on the dyno machine somewhat too. Im sure this thread will have some technical responses to follow.

White96GTinFla · Sep 14, 2003

Dark Knight GT said:
Im sure this thread will have some technical responses to follow.

Im sure it will... its a tech post. Every dyno ive seen it will compensate for the gears, so I dont know why people are losing 8hp. You can lose 8 hp EASILY just by weather conditions, diff. gas, and stuff like that... I wouldnt be blaming it on gears.

trinity_gt · Sep 14, 2003

Dark Knight GT said:
This is going to become one of the biggest technical threads of your life when guys like TrinityGT, Triblkcobra, mrvax, and white99GT see this. Thats not bad though. Its just gonna get long so I figured Ide warn you.

Nah, I'd just recommended the original poster use the Search. This has been hashed out pretty well before and some pretty interesting theories have been put forth.

BTW White96GTinFla, your avatar is hilarious

Venom4.6 · Sep 14, 2003

From what I've read and heard, your #'s will pretty much stay the same. I've even heard that most gain a little torque. Not much though. Gears just put you in the power band alot quicker.

Blakers01GT · Sep 14, 2003

trinity_gt said:
Nah, I'd just recommended the original poster use the Search. This has been hashed out pretty well before and some pretty interesting theories have been put forth.

BTW White96GTinFla, your avatar is hilarious

I would but stangnets search sucks. i think i get the idea though.

Sam98 · Sep 14, 2003

Dark Knight GT said:
Hmmm. Ive seen guys on here before who had their cars put on the dyno after a gear change and they claimed they lost rwhp. I guess it does depend on the dyno machine somewhat too. Im sure this thread will have some technical responses to follow.

Ever watch an automatic on the dyno? You essentially have 3 different final drive ratios, very different torque multiplication in each gear, and yet the HP and torque are very close on all of them...Think about it...

bamf70 · Sep 14, 2003

Sam98 said:
The dyno takes the gearing into consideration, so unless the gears are adding resistance to the drivetrain you aren't going to see anything.

I totally disagree. I have been told by the places I have had my car dynod that a taller gear will lower your overall rwhp/rwtq #s. Nobody could give me an exact %, but for my 4.30 the accepted # was ~ 5%. I have basically every bolt on available. My dyno was 261rwhp 261 *1.05 = 274 rwhp. Now for a stock geared car with all the bolt ons that is right about where it should be.

Sam98 · Sep 14, 2003

bamf70 said:
I totally disagree. I have been told by the places I have had my car dynod that a taller gear will lower your overall rwhp/rwtq #s. Nobody could give me an exact %, but for my 4.30 the accepted # was ~ 5%. I have basically every bolt on available. My dyno was 261rwhp 261 *1.05 = 274 rwhp. Now for a stock geared car with all the bolt ons that is right about where it should be.

Taller gears are lower numerically and have the exact opposite result you are talking about.

bamf70 · Sep 14, 2003

Sam98 said:
Taller gears are lower numerically and have the exact opposite result you are talking about.

Higher, lower, taller, shorter doesn't matter. The point is the gear in the car WILL effect the dyno results. To this point, nobody seemed to understand that.

TriBlkCobra · Sep 14, 2003

lol... Hey trinity, I'm not getting lured into this one again! j/k...

And, again, dont sweat this "lost hp". Its just a measurement artifact. The car will indeed be much quicker and the net gain is much better than the loss of dyno number bragging rights!

jaxter · Apr 23, 2004

Jeez.....well, I understand physics a bit. Changing (lowering) the gearing would most likely increase, not decrease, HP foir a real-world car....lemme 'splain.....less drag on a motor translates to free rev's and less wait 'til peak-hp band (while driving, not on a dyno..). In any event the gain/loss by change of gearing has very little to do with overall RWHp #'s.....a set of gears doesn't 'eat power' or cause a decrease of transmitted power (spline count, my butt). 'Power', at a set rpm, should be identical across any gear range on a dyno if it's calibrated properly. Would love to hear any arguement to this...jaxter@megsinet.net

CottonBurnerz · Apr 23, 2004

try posting this on www.modulardepot.com

they know their stuff

cold96snake · Apr 23, 2004

Does this mean i would've dynoed higher if i didn't have 4.10's? See #'s in sig.

'01 Steed · Apr 24, 2004

I've been told (during my last dyno session) that it has something to do with the amount of time the dyno has to measure the power. The lower gear provides less time through the torque curve to measure. I don't know 'bout all that, but I do know that my 4.10's kick the ****e out of the 3.27's!
A good way to avoid these artifacts (good term for it TriBlkCobra) is to do the gear mod first. It is, BTW, the best bang for the buck anyhow!
I'll hang up and listen for the response.

Jonny'00GT · Apr 24, 2004

I was told that an engine makes X amount of HP and then you can loose HP to the wheals based on efficiency. I just put 4:10s in last weekend and, Dude...all I know is when I mash down on the "Happy Pedal" the tires cry, I gigle and my wife want's to kick my ass!!! (some ***** about whip lash...I don't know...)

Man, just throw some 4:10s in and try not to worry too much about physics...unless you're writing a paper, then have at it!

Before the gears I drove a car...now I own a MUSTANG!!!

'01 Steed · Apr 24, 2004

Tru Dat Jonny!! That's some funny sh#t!! I like the part about the "Happy Pedal"! I'm gonna borrow that, if you don't mind.

How much do gears really effect dyno numbers??

Blakers01GT

Master of the Clubhead

Dark Knight GT

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Sam98

Dark Knight GT

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White96GTinFla

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trinity_gt

Venom4.6

Blakers01GT

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Sam98

bamf70

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bamf70

TriBlkCobra

jaxter

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CottonBurnerz

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cold96snake

'01 Steed

Jonny'00GT

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