is there a differance in the results between dynoing in 3rd compared to 4th

 

in a word....no

 

3rd gear should give you higher hps reading and easier on the engine.
4th gear will give you more accurate reading.

 

You want to be as close to a 1:1 ratio as possible.

 

The most accurate reading will be given in the gear that is closest to a 1:1 ratio. In most cars, this is 4th gear.

3rd gear is usually used when you are tuning so that you can more runs in. It takes less time to do a run in 3rd and the engine load is less in 3rd.

In my experience, 4th gear gives consistantly higher numbers than 3rd gear. I have dynoed my car in 3rd and 4th back to back, and 4th was consistantly 1.5-2.0 HP higher than 3rd. I have the dynos, but no where to host them...

Andrew

 

my old dyno actually shows more power being made in 4th gear. we just wanted to see what the power output would be in the gears i would be running in realtime.

 

3rd gear I had a smooth plot. 4th gear I had a dip at Vtec activation. Both gears within 1 hp of each other. I chose not to fix the dip because is not noticeble when driving and most of the time I will not be in fourth when I go into vtec. Plus trying to fix that dip would be a bitch. Moral of the story is, if I had not dynoed in 3rd I would have tried to fix the dip in 4th and would be more $$$$$$$$$$$$$ for dyno time and a pain in the ***.





[Modified by MPH, 3:03 PM 3/19/2002]

 

I got 3-4hps higher reading when I do the run in 3rd gear. But that was on a B16A!!

 

it's within 1 or 2hp difference on Phil's dyno, Mike.
I did 180/130 in 3rd gear.. 181/131 in 4th gear.

4th gear takes longer. F 4th.

 

When I did my car, I was surprised that 4th would give slightly higher numbers too. I had always thought just the opposite...

Can anyone explain why? Mathematically maybe?

Andrew

 

Funny, 4th always yielded 1-3 hp lower for me, all the time. It was never higher.

But they were always pretty close, so just do it in 3rd ....

The shop I went to typically did FI cars in 4th, and NA cars in 3rd.

I always did it in 3rd, because that is what I had always done. Whenever I DID do 4th, the results were what I just said.

 

4th got me 2hp over 3rd

 

4th

 

on new dynojets (248's) it doesn't really matter that much because the dyno taps off the spark reading (for rpms, etc...) and also reads the wheels rotational mass of the wheels and calculates for it. The difference is very, very slight on most cars however thats only if the gear ratio is close between the two gears your compairing. With type R's for example 3 and 4th gear runs are practically identical. The only time I see a need to dyno in 4th is if you want to see what the engine is doing in that gear for drag racing or track racing where 4th might be used a lot.
With my car however I get a 10whp gain when dynoing in 4th vs 3rd because in 4th my car will boost higher because with the roots style blower running off the belts, in 4th gear they are spinning alot faster and will techincally boost slightly higher by a pound or so which gives me that extra bit of power.