hi all.. had a run done today with a local car club and they used 4th gear.. its a dyno dynamics rolling road .. only asking as the last time it went on the rollers it was done in 3rd.
a bit dissapointed with the result but still goes like fook for me..
cheers
j

 

Mines usually in 4th what power it make guessing it's a fiesta turbo

 

hi no its a 2wd saff.. never got round to changing my username..

 

what power did you get matey ?? whats the set up your running ??

 

Mine was ran in 4th

 

Did the previous place explain why they used 3rd ? That would be strange.

 

Tends to be fourth, but higher gears can be used if traction is an issue and to give more readings to plot the graph.
Still should give same results though.

 

The gear closest to 1:1 should be used.

So in a cossie 4th.

 

As above, most places use the gear closest to 1:1

What power did you get bud?

 

^^ as these to, closest to 1:1 which in most cars is 4th

 

It did 463. Has done 498 before both dd rollers.

 

You will get a little variance in using a different gear but not as much as 35 bhp from what I have seen in the past.
Might be worth checking vacuum lines and boost hoses or inlet gaskets for a possible air leak.

 

Or checking inlet temps compared to ambient temps on both graphs. Sure we have all read how much difference it can make to a final figure.

 

The fan was tiny compared to the one used before and car had been ticking over for ages before this run. Also theit gauge was plumbed into the map sensor pipe I just realised but unsure if this makes any difference

 

The pre graph was shoot 44 so is wrong for power at fly check power at wheels.

Mark

 

I didn't get a at wheels graph the first time round. Would that make much difference.

 

Makes more sense to use wheel figures anyway.

 

From mem it would add about 6% to it.

Mark

 

So the original graph should show 6% less then.
What would you think could be the reason it's making low power.
I'm glad the thing is off the road now.

 

4th gear isn't in fact a gear it is direct drive from the clutch, through in input shaft, through the input shaft dog ring and synchro ( also know as 4th gear. This connect the input shaft to the main shaft and to the prop shaft. ie no actual gear mesh.

Some RR tuners dont like 4th gear because in 4th 1:1 7000rmp is normally 140 mph. there are some tuners that just dont like to have a car on their rollers doing 140.

You can never take any two RR readings at face value. Was the ambient temp in the RR cubicle hotter or cooler. for ever 1dec you can reduce your input temp you can expect a 1 hp increase. ( more on tuned engines).
Was the IAT's monitored, were they the same on each session. smaller cooling fan could have a large effect on power.

Tyre size has a impact on power, the bigger the tyres the more power is lost. Were the wheels and tyres the same.

What fuel was used and how old was it. Pump fuel can be different from make to make. Esso is 98 ron, BP 97 ron, Shell Vpower 99 ron. Was it the same in the Tank as before.

Operator variable can make a difference in readings. two different people can get two different results. not massively different but when your chasing number the loss of 10 or more hp can feel like the end of the world.

Factor in a bad day and a combination of the above and you could end up disappointed.

You can also do Pbox 60-130's to get an idea of your power.

BTW a rwd 3 door standard with 205bhp should show about 155-165 at the wheels on a roller. Been there and done that 25 years ago.

 

Power Enginering rollered mine in 4th, along with all other cossie's on the day.

Steve