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Technical question about running on the dyno

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Old 07-11-2008, 11:01 AM   #1
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Default Technical question about running on the dyno

Well i had never seen a dyno run in person before i did mine, and i always thought they just threw the car in top gear and ran it to the redline. Well The guy that that ran mine put it in 4th gear, and i asked him why, he said you have to have it in a 1:1 ratio...Now obveously i know this is talking about the gears, but i really dont understand. What gears have to be 1:1?
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Old 07-11-2008, 11:56 AM   #2
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Tranny gears have to be 1:1 because in any gear lower than 1:1 you have torque multiplication, and the exact opposite in any overdrive gear and you'll never have an accurate reading.
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Old 07-11-2008, 12:52 PM   #3
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Oh so since 4th gear is 1.02 with our cars thats what they put it in? I see...
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Old 07-11-2008, 06:24 PM   #4
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'Knowing is half the battle'..........GI JOE!!!!!!!!! Sorry x)
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Old 07-11-2008, 07:09 PM   #5
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A tuner should step in and explain. Maybe I can post a stupid enough responce to get one to respond.

Let see now.

1. Tune in 1:1 rather than x.xxx lower gear because you get better/longer sampling AF data as engine doesn't rev as fast.

2. Tune in 1:1 rather than 0.xxx higher gear beause customer may not have good or correct speed rated tires on car.

3. Not sure about rest of dyno's but the Dynojet can take gear ratio into account when caculating TQ and HP. Now will numbers be the same for 3rd, 4th and 5th? They could be but more often they want be due to tune being optimized for the gear it's tuned in.

It would be nice if one of the tuners would put up a Dynojet dyno graph of car run in 1:1 and OD in three box format on same sheet. Show TQ & HP in box 1, show Engine RPM and and Speed in box 2 and AFR and gear ratio in box 3 and show this in TIME and set graphing option so sampling for runs starts at same xxxx rpm.
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