Predictable question :D:D

 

Does anyone know the transmission loss for an auto gearbox? In percentage terms, nothing lightened etc?

 

The RR setup couldn't cope with calculating the transmission loss due to running down in 2nd gear (as opposed to 4th in a manual).

 

As a result I got a flywheel figures of 403 & 397 :rofl: today

 

Had a few goes trying to sort out the losses with the guy, and my best RWBHP was 268 - any ideas what this equates to @ flywheel? :confused: The RR flywheel assumed losses of 135BHP :eek:

 

This was the reason all the autos had unexpectedly high flywheel figures...

 

Cheers

 

Pete

^

|____ owner of the smooooothest curves around :D

Hmmm a search throws up quoted losses of 15% - 30% for an auto.

 

15% loss - gives me 315BHP (loss of 47 BHP)

30% loss - gives 382BHP (loss of 114BHP)

 

Quite a range.

 

With mongoose zorst, decat, Stillen intake, chip and 12psi, I'd expect around 350BHP (23% loss...)

 

Shame the RR guy didn't have a clue about it :rolleyes:

 

Pete

30% is a little high.

 

I would have thought 18%-25% loss for rear wheel automatic.

 

4WD systems can lose 33% of the power in the transmission.

I know what you mean. :(

 

I got 325 at the flywheel, but 248 at the RW.

 

I suppose Id got my hope set a little high.

 

Oh, well. Back to the drawing board. ;)

Oooh just seen that PaulC got the same max RWBHP as me, but in a manual, and was given 346.2bhp @ flywheel.

 

Interesting :) If autos lose a bit more than manwells then I am looking at 350something BHP. I'll take that ;)

 

Pete

Pete, there were problems I believe with the RR handling the rundown on autoboxes, it managed to give it a to high flywheel figure,

 

all that matters is what you are putting down on the road really though :) those figures should have been concentrated on.

IIRC Paul's RWHP was recorded just before the turbo's unleashed the full 16 psi he was running. That was at 4,400 rpm. :eek:.

 

Get some F1's on there Paul and we'll go back and see if we can both bang out a 400 bhp flywheel figure.

Tranny losses are not really a %age, they are pretty constant regardless of power.

 

S13's generally lose 40-50 bhp through the tranny whether it be a std car or a 480bhp car.

 

Mine have always been 44 or 45bhp and I've had a few different diffs adn gearboxes.

 

/jezz frantically searches for RR graph.

 

LOL in fact only 39bhp losses on Gary's car when it was only running 440bhp.

 

Jezz - how did they measure that tho? :confused:

 

Its just believing one RR setup against another... Not having a dig just wondering how they can measure in on a par with manuals?

 

IMO It was the 2nd gear selection that threw it yesterday - unless there's a way of holding an autobox in 4th (is there??) then its hard to compare auto and manual flywheel figs.

 

Nice graph BTW :D

 

Pete

Well it's a manual so you just press the clutch and wait for the rollers to spin down and measure the drag.

 

Auto's must create more drag and therefore bugger the results, but I don't know well enough how an auto box works to say why.

 

I'm a firm believer that RWBHP is the only really important measurement.

Yep me too now :) I guess manufacturers start off quoting flywheel fig so to maintain comparability, the RR guys do too :rolleyes: Plus the numbers are bigger :D

 

Sorry - thought yours was an auto for some strange reason :D