OcUK Rolling Road 9: Photos + Graphs

Fuzz · 4 May 2009 at 15:30

I'm not even going to get in a discussion about it to be honest, it's like banging your head against a brick wall and I'm sick to death of explaining it.

DRAG CANNOT BE SAID TO BE XX%
DRAG IS EXPONENTIAL ! The faster you go the more drag you will create.

A run in 3rd gear would show more wheel bhp and less drag than a run in fourth would. but the flywheel output would be the same as they cancel each other out.

As for the rpm measurement on a few cars brought up...
I MANUALLY tell the dyno what RPM the car is at.
The S2000 had a digital RPM gauge so the one bar lit up for 3000 rpm meant it could be anywhere from 3000 to 3200 when it would light up the next bar..
so say I'm 50 rpm out at 3000, at 6000 that's 100 rpm out and 9000 it would be 150 rpm out.
This could affect the flywheel readings SLIGHTLY as Power is a function of torque and engine speed and also give you the impression of it missing its intended rpm limiter.
Which... by the way some cars do, I've had two cars of the same model /age being back to back tested and the limiter is in a different place on each. (or the tacho was out)

Now please go read up on Maha dyno's...
Porsche and BMW both use these types of dyno for their own testing.

Simon · 4 May 2009 at 15:36

Early S2000s hit 9200rpm anyway.

When I had my Rover turbo i ran it at powerstation and another dyno. Both read 260hp at flywheel, one was 225 at wheels the other was about 170hp at wheels.

Wheel figures aren't the be all an end all that a lot of people seem to make out. The fact the dyno is a transient dyno and not steady state means that nothing is ever measured 100%, there will always be a calculation factor involved

The_One · 4 May 2009 at 15:36

Do you run every car in 4th gear?

Car should be run in whichever gear is closest to 1:1 this is not always 4th gear.

Simon · 4 May 2009 at 15:40

The_One said:
Its way out

S2000 should hit around 200 RWHP

And hit 237hp as this is stock flywheel power, this is also what powerstation measured.

Seems you are ignoring the correct information and focusing on something you think is wrong. As for RPM that purely dictates the torque curve.

Power is measured from dyno torque and dyno speed. No need for the operator input.

Simon · 4 May 2009 at 15:40

The_One said:
Do you run every car in 4th gear?

Car should be run in whichever gear is closest to 1:1 this is not always 4th gear.

Why? Would be interesting if you actually understand the reason why

InvaderGIR · 4 May 2009 at 15:45

Unfortunately some people don't take part in things and instead just keyboard worrier bitch about everything.

The fact we had multiple cars running meant we ended up with a good view as to how accurate the dyno was being.

As my car was first up I saw the figure and assumed the rollers were doing what a lot of people say, and reading far too high, but then more and more cars ran and it showed that it was in fact reading about right.

Again I have to say thanks Andy, was a good day and gave everyone a decent idea as to what their car is running (which is in essence all a dyno can do anyway).

The_One · 4 May 2009 at 15:49

Because the gear that gives 1:1 ratio or closest to it is the most efficient gear.

Lower than 1:1 and you give a lower reading over 1:1 and its over reading.

Fuzz · 4 May 2009 at 15:55

The_One said:
Do you run every car in 4th gear?

Car should be run in whichever gear is closest to 1:1 this is not always 4th gear.

Ouch.. my forehead is bleeding now

agw_01 · 4 May 2009 at 16:04

Sorry to interrupt this little discussion but I've just sorted through my pictures. No real difference to anyone elses but thought I'd put them up anyway.

Fuzz · 4 May 2009 at 16:07

haha just spotted your sig..
Looks like you had a bit of competition on being the resident midget at the meet.

Mr_White · 4 May 2009 at 16:07

agw_01 said:

Is this the OcUK Jeans Enthusiast meeting?

Fuzz · 4 May 2009 at 16:08

InvaderGIR · 4 May 2009 at 16:10

Mr_White said:
Is this the OcUK Jeans Enthusiast meeting?

I think I was one of the only ones not in jeans, and was the ONLY one in shorts.

agw_01 said:

I see a NINJA!

Booner! · 4 May 2009 at 16:12

Some good photos, looks like a good turnout of different cars.

Exige is a very cool looking car and I can't help but like that black MX5.....I must be having a funny day or something because I don't really like them in general...nice car.

Any talk of when the next RR is? I will bring the zed as it will be on the road soon, after a long list of stuff going on with it this month

D)

InvaderGIR · 4 May 2009 at 16:18

Booner! said:
Any talk of when the next RR is? I will bring the zed as it will be on the road soon, after a long list of stuff going on with it this month D)

We'll be looking at sorting the next one for late August I think, although I think the organisation of it is going to be changed a bit to avoid having so many drop outs and ensure all the cash is there for the runs as it was sketchy on Sat.

Booner! · 4 May 2009 at 16:20

Cool, plenty of time then. I saw that there was a monthly meet for the south.... any idea if this is still running, as I haven't been to an OcUK meet before

InvaderGIR · 4 May 2009 at 16:24

The mini meets are all dependant on people bothering to organise them, and are mostly a case of "I'm going to the pub, who's coming?".

Booner! · 4 May 2009 at 16:26

I think there should be a mini meet organised for the first weekend in June, not sure if I would be any good at organising one....and I there is nowhere interesting round here

thedazman67 · 4 May 2009 at 17:24

agw_01 said:
Forge actuator and a ball and spring controller.

Would have liked to have tweaked the Forge a bit more... the boost spikes a little bit as it comes in, meaning that it tails off a little bit towards the top end.

Still, doesn't seem to have affected the power too much, heh.

Just picked up a forge actuator myself actually will see how it goes.

Fr0dders · 4 May 2009 at 18:34

The_One said:
Because the gear that gives 1:1 ratio or closest to it is the most efficient gear.

Lower than 1:1 and you give a lower reading over 1:1 and its over reading.

nokin has giving up exlaining so i shall try and explain for you.

It doesnt matter what gear the dyno is run in on the maha. On powerstations dyno, it measures the power at the wheels all the way up to the rev limit, then lets it coast back down again and measures the constantly fluctuating drag all the way back down to rest

If you run in a higher gear than 1;1, it will have higher drag and give quite a low power at the wheels figure. Look at mine, it was run in 5th and shows 195 power at the wheels, a loss of over 80bhp !!

but because it measures the drag on coastdown, it accounts for the fact the drag was high at the time, to calculate the correct power at the fly.

The gear also doesnt matter, as the 1:1 thing is only really of significance if its assuming that 1 dyno wheel revolution = 1 engine revolution, but it doesnt. Nokin enters the RPM into the dyno manually, it doesnt read the RPM of the dyno.

This coast down is also the same reason why the power at the wheel figure is inaccurate. Its not designed to be quoted to customers, as like germany, everybody here works on power at the fly, so the power at the wheels, is just a way to measure this.

You're under the misapprehension that the power at the fly reading is totally and utterly 100 % true, and its alll just random maths used to calculate power at the fly. And this is simply not true as it depends on the dyno.