Dyno'd the GS430
Keep up the modding 
09-24-08, 04:56 PM
#52
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4 Pages, and not one person mentioned he has a different rear end. I'm sure it has some effect of change, because the stock 430 is a 3.26 rear end, and you have a 300 which is a 3.92. This would def show a difference in numbers. I think you are gaining more power by the larger differential.
09-24-08, 05:24 PM
#53
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4 Pages, and not one person mentioned he has a different rear end. I'm sure it has some effect of change, because the stock 430 is a 3.26 rear end, and you have a 300 which is a 3.92. This would def show a difference in numbers. I think you are gaining more power by the larger differential.
09-24-08, 07:29 PM
#54
actually not totally...if you think about the use of rear end gears (torque multiplication) depending on how much or how little the gears either reduce or increase the number of rotations per unit of torque, it could throw the numbers off on a chassis dyno, considering the power needs to leave the engine, go through the trans/driveshaft, then through the rear end and to the wheels. So technically, the rear end gears definitely could effect your numbers by either adding or reducing drag on the engine.
09-25-08, 08:37 AM
#55
Lexus Champion
All gear interchanges have some loss. The best ratio is a 1-to-1 which in a transmission is usually 4th gear. The worst gear is 1st gear. Stock 3.26 differential gearing has slightly less gear loss than the 3.92 ring and pinion ratio.
There are many other factors but on a chassis dyno the load between the tires and the dyno rollers is a substantial factor of the total drivetrain loss. The higher the torque the greater the deflection, slip and friction of the tire/roller interface.
When you change the differential ratio you change the REAL torque that the tire/roller interface must transfer. The higher the numerical ratio the higher the torque load created. Higher load creates a higher drivetrain loss. The net result is a LOWER reading on a chassis dyno when running higher ratio multiplication.
So, in simple terms, the 3.92 ratio will produce a lower reading than the stock 3.26 differential gears. This difference is probably less than 10hp. Not a big factor but is NOT helping the dyno reading for this effort.
09-29-08, 04:47 PM
#57
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Changing rear end gears may or may not change your numbers and every situation can cause different effects and can go either way.
There are times when you don't want to dyno in 4th. If the pull takes to long, you will heat soak the motor and you won't see the peak HP that your car is capable of at the end of a long pull. So on some cars it is better to do the pull in third.
My tbird's 5 speed has almost the same gears as a GS 5 speed auto, but it has 2.73 rear end gears. I do my pulls in third. When I do a 4th gear pull the numbers are down. (see attachment, the pull time was nearly double)
Motor Trend didn't dyno the new Nissan GT-R in the 1:1 gear for the very same reason.
I could put 3.27's in my bird and start doing the pulls in 4th and my numbers should go up.
There are times when you don't want to dyno in 4th. If the pull takes to long, you will heat soak the motor and you won't see the peak HP that your car is capable of at the end of a long pull. So on some cars it is better to do the pull in third.
My tbird's 5 speed has almost the same gears as a GS 5 speed auto, but it has 2.73 rear end gears. I do my pulls in third. When I do a 4th gear pull the numbers are down. (see attachment, the pull time was nearly double)
Motor Trend didn't dyno the new Nissan GT-R in the 1:1 gear for the very same reason.
I could put 3.27's in my bird and start doing the pulls in 4th and my numbers should go up.
09-29-08, 09:14 PM
#58
Lexus Champion
Those gears also slow down 0-60 times because the car must shift twice 1-2 then 2-3 where the stock gearing will allow 60mph in 2nd gear!
09-29-08, 09:43 PM
#59
Lexus Champion
Changing rear end gears may or may not change your numbers and every situation can cause different effects and can go either way.
There are times when you don't want to dyno in 4th. If the pull takes to long, you will heat soak the motor and you won't see the peak HP that your car is capable of at the end of a long pull. So on some cars it is better to do the pull in third.
My tbird's 5 speed has almost the same gears as a GS 5 speed auto, but it has 2.73 rear end gears. I do my pulls in third. When I do a 4th gear pull the numbers are down. (see attachment, the pull time was nearly double)
Motor Trend didn't dyno the new Nissan GT-R in the 1:1 gear for the very same reason.
I could put 3.27's in my bird and start doing the pulls in 4th and my numbers should go up.
There are times when you don't want to dyno in 4th. If the pull takes to long, you will heat soak the motor and you won't see the peak HP that your car is capable of at the end of a long pull. So on some cars it is better to do the pull in third.
My tbird's 5 speed has almost the same gears as a GS 5 speed auto, but it has 2.73 rear end gears. I do my pulls in third. When I do a 4th gear pull the numbers are down. (see attachment, the pull time was nearly double)
Motor Trend didn't dyno the new Nissan GT-R in the 1:1 gear for the very same reason.
I could put 3.27's in my bird and start doing the pulls in 4th and my numbers should go up.
09-30-08, 05:35 AM
#60
Yes, that is what I am saying. Running 3.769 gears will show slightly less RWHP than the stock 3.266 gears. Not a big amount. Now, the ACTUAL RWTQ will be 15% more in any given gear at any given RPM. But, you change gears sooner so stock gears have a slight advantage for the gearing MPH changes as you will be in 2nd gear with 3.769 while stock gears are still in 1st. Again in 3rd for a bit and then 4th... all until the stock geared car changes.
Those gears also slow down 0-60 times because the car must shift twice 1-2 then 2-3 where the stock gearing will allow 60mph in 2nd gear!
Those gears also slow down 0-60 times because the car must shift twice 1-2 then 2-3 where the stock gearing will allow 60mph in 2nd gear!
I could always say, lets race to 70mph. lol
Also, your 0-60 point above is JUST for a stock GS4XX with the addition of the 3.76 gears alone...is this correct? In my case I also have a 3000 stall PI TC...will my 0-60 time still be slower than a stock GS4XX?
I hope not...