Will gears show results on a dyno???
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Will gears show results on a dyno???
I was just thinking, since you are basically multiplying the torque produced by the engine, shouldn't the rwtq also be up by a certain percent? I know that 4'th gear would no longer be 1:1 ratio. How does that work??? Just a curiousity question...
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Re: Will gears show results on a dyno???
Originally posted by 96 WS6
I was just thinking, since you are basically multiplying the torque produced by the engine, shouldn't the rwtq also be up by a certain percent? I know that 4'th gear would no longer be 1:1 ratio. How does that work??? Just a curiousity question...
I was just thinking, since you are basically multiplying the torque produced by the engine, shouldn't the rwtq also be up by a certain percent? I know that 4'th gear would no longer be 1:1 ratio. How does that work??? Just a curiousity question...
Something to the tune of 2 - 4 HP from 3.42 to 4.10.
I believe there was a post on this a few weeks ago... do a search you may find it.
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http://web.camaross.com/forums/showt...ight=dyno+gear
There is a thread about this from advanced tech.
4th is 1:1 in an M6, 3rd for an A4
The below quote is talking about dynoing in different transmission gears, but changing rearend gears is a similar affect. Point 3 is the most relevent to rear end gears. As stated above, a taller gear will show more inertial losses because the rotating mass of the engine and drivetrain is accelerated faster.
There is a thread about this from advanced tech.
4th is 1:1 in an M6, 3rd for an A4
The below quote is talking about dynoing in different transmission gears, but changing rearend gears is a similar affect. Point 3 is the most relevent to rear end gears. As stated above, a taller gear will show more inertial losses because the rotating mass of the engine and drivetrain is accelerated faster.
You can dyno in any gear, i'm not sure what you guys mean by 'torque multiplication being a problem', or not being 'at its full potential'. A dynojet calculates the overall gear ratio in terms of RPM/MPH. You can find that ratio on any dyno data sheet like this. That is why you don't have to tell them what rear end gear you have, or what gear you are in. The dyno measures the drum acceleration and the hp it would take to accomplish that.
Here are 4 reasons to dyno in the 1:1 gear.
1) Most importantly, everyone else dynos in 1:1 so it will make your results more accurate to compare with others.
2) There is the least tranny friction in the 1:1 gear, 4th in a manual or 3rd in an auto. On a side note, lower rear end gears, 4.11 vs 3.42s, with a smaller pinion gear could show slightly higher frictional losses but this is minor.
3) The mass of the engine will accellerate slower compered to dynoing in a lower gear which would wind up faster. This makes the inertial losses in the motor smaller compared to the inertia of the drum.
4) It's closer to the optimum rate for data collection. I don't personally 'buy' this reason, but I was told that by a dynojet operater. I don't think that equipment should have any trouble taking accurate measurements on a motor spooling up 2x as fast, but i didn't design it or operate one regularly.
So you could argue that the OD gear would have more friction, but spin up slower which would partially cancel out. ANother consideration is how fast you really want to be spinning that drum
As to why your car didn't shift, i'm not sure. I don't have an A4, but i thought they don't shift into OD when you are WOT and you had to let off a second when you got to that point??? Is 120 mph in 3rd your redline/shiftpoint, or somewhat less than it???
-brent
Here are 4 reasons to dyno in the 1:1 gear.
1) Most importantly, everyone else dynos in 1:1 so it will make your results more accurate to compare with others.
2) There is the least tranny friction in the 1:1 gear, 4th in a manual or 3rd in an auto. On a side note, lower rear end gears, 4.11 vs 3.42s, with a smaller pinion gear could show slightly higher frictional losses but this is minor.
3) The mass of the engine will accellerate slower compered to dynoing in a lower gear which would wind up faster. This makes the inertial losses in the motor smaller compared to the inertia of the drum.
4) It's closer to the optimum rate for data collection. I don't personally 'buy' this reason, but I was told that by a dynojet operater. I don't think that equipment should have any trouble taking accurate measurements on a motor spooling up 2x as fast, but i didn't design it or operate one regularly.
So you could argue that the OD gear would have more friction, but spin up slower which would partially cancel out. ANother consideration is how fast you really want to be spinning that drum
As to why your car didn't shift, i'm not sure. I don't have an A4, but i thought they don't shift into OD when you are WOT and you had to let off a second when you got to that point??? Is 120 mph in 3rd your redline/shiftpoint, or somewhat less than it???
-brent
Last edited by 94formulabz; Dec 17, 2003 at 03:47 PM.
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