What gear for rolling road

[chazuk]

When I had my dyno done on my bpu I noticed the guy used 4th gear , but I now know 5th gear is 1:1 ratio so surley 4th would show a higher figure due to this am I wrong ? also lower gear it would also take less time as the engine accelerates faster.

[monsween]

Should be 5th for 6speed box, 4th for 5speed box and 4th for n/a i think

[chazuk]

Should be 5th for 6speed box, 4th for 5speed box and 4th for n/a i think

 

Yea I thought it would be so in fact my graph for bpu will be way out but I swear ive seen supra's run at ssr in 4th ,I guess the only way that it can be corrected is if the software uses the road speed measured by the rear rollers to get engine rpm then can scale the power curve I guess once you have got a reading from a set speed the software will work out the revs at any road speed .

[Guigsy]

3rd or 4th post down in tech (sticky)

 

NB: DUE TO THE HIGHSPEEDS INVOLVED IN DOING A 1:1 DYNO SOME DYNO'S WON'T BE ABLE TO DO THESE IDEAL RUNS.

 

If you wish to Dyno your Supra please INSIST on the following;

 

Run your powerrun in the 1:1 ratio gear. This means it's running at the same speed as the engine, not under or over driven. It's therefore more accurate to what the engine is actually doing and you don't get sill conversion factors. Also confirm that the dyno is setup to immitate a straight FLAT road, uphill or down hill will just frig the figures.

 

Manual V160/V161 6speed

DYNO IN 5TH GEAR

 

6 Speed (V160) / (V161)

1 --- 3.827 / 3.724

2 --- 2.360 / 2.246

3 --- 1.685 / 1.541

4 --- 1.312 / 1.205

5 --- 1.000 / 1.000

6 --- 0.793 / 0.818

Rev - 3.280 / 3.192

Diff - 3.266(all TT) / 3.769(NA)

 

 

Manual W58 5speed

DYNO IN 4TH GEAR

 

1 --- 3.285

2 --- 1.894

3 --- 1.275

4 --- 1.000

5 --- 0.783

Rev - 3.768

Diff - 4.083(NA)

 

Auto (A343E) 4speed

DYNO IN 3RD GEAR

 

1 --- 2.804

2 --- 1.531

3 --- 1.000

4 --- 0.705

Rev - 2.393

Diff - 3.769(TT) / 4.083(NA)

 

Auto's are hard to Dyno. You have to my in Manu mode with O/D off. You also need to start at about 3000rpm to avoid kickdown.

[Homer]

Not sure how true this is, but a couple of the dyno operators I spoke to said the speeds high performance cars like the Supra acheieve in 1:1 gears is higher than the RR's limit...

 

Edit - just noticed, it already says that in the sticky

[dude]

Jeans and a T shirt, in winter a Jacket and Hat can be added.

[davej705]

Jeans and a T shirt, in winter a Jacket and Hat can be added.

 

[chazuk]

3rd or 4th post down in tech (sticky)

Thats my bad for not searching then , its annoying how none of the print offs are never filled in which gear etc got a funny feeling allot are done in 4th which would make the real hp allot less than stated once I have finished my build I want to know the true figure not what looks good on paper so will find a rr that will handle the speed of a 5th gear run.

 

Jeans and a T shirt, in winter a Jacket and Hat can be added.

 

Dude I have had a few tonight:) and you've totally lost me ?

Edited November 11, 2010 by chazuk (see edit history)

[Homer]

It won't make any real difference if the dyno is setup correctly and the operator knows what they're doing. The *only* way to get a proper engine output reading is to get it on an engine dyno, but that - at the moment - is very expensive. Hopefully AFR will have a more cost effective solution for that in the future

[garethr]

Apparently the lower gear will give a slightly higher figure, because the power loss in the drive train increases with wheel rpm.

 

Lower gear means the wheels rotate more slowly, so the drive train loss is lower, so the measured power (well, torque...) is higher.

 

(I wouldn't worry about it. Everyone quotes the "flywheel" figure anyway, and that's always a guess - sometimes an educated guess, admittedly, but always a guess. )

[dude]

It won't make any real difference if the dyno is setup correctly and the operator knows what they're doing. The *only* way to get a proper engine output reading is to get it on an engine dyno, but that - at the moment - is very expensive. Hopefully AFR will have a more cost effective solution for that in the future

 

If anyone has seen the Escort Cosworth race car at our place that had its engine on a superflow engine dyno, when the engine was put in the car and it was run on our chassis dyno there was a 2hp difference at the measured FWHP on the superflow and what our DD workrd out AND SRR's DD and ours seem very very close in figures.

 

I would of thought only the RWHP matters as thats whats pushing you forward at the end of the day.