Boyracer D1-R

Sean · Postby **Sean** » Sun Jun 12, 2011 9:32 pm

Perhaps a confusion in dyno readings between newtons and newtwon metres...
Often mistaken for eachother.

I've often seen the challenge where the diff ration inflates the reading when no correction factor is used too.

In reality though, it's a race car, BR's results at the track will prove it's worth a lot more accurately than any dyno reading.

Postby **NitroDann** » Sun Jun 12, 2011 10:52 pm

Sean wrote:Perhaps a confusion in dyno readings between newtons and newtwon metres...
Often mistaken for eachother.

I've often seen the challenge where the diff ration inflates the reading when no correction factor is used too.

In reality though, it's a race car, BR's results at the track will prove it's worth a lot more accurately than any dyno reading.

So often on aussie forums and in real life I hear people quote ridiculous torque figures that make no sense.
Newtons cannot be converted to Newton-metres, or is a measure of linear force and the other a measure of twisting force.

Unless there is some dyno which measures in newtons like you measure thrust.

Somebody please enlighten me.

Dann

Postby **Boyracer** » Mon Jun 13, 2011 12:14 pm

Dann...I quoted figures on the Dyno sheet from Mania.,,,the car was really fast and thats all I was worried about...did 1.07.2 at Wakefield on semi slicks.

I just do the spanner work and drive the car...leave the technical stuff to smart people....I am always very happy with Davids work and would not take the car to anyone else...

Anyway the turbo engine is gone and the new naturally aspirated engine is in...

Will see what the next Mania dyno sheet says....hopefully the car will be there by the end of the week.

Postby **NitroDann** » Mon Jun 13, 2011 12:24 pm

I never doubted the car is fast. And your work ethic is great.

But the numbers that come off that dyno are always crazy.

Dann

Sean · Postby **Sean** » Mon Jun 13, 2011 1:06 pm

Torque multiplication via gearbox and diff?
Same reason you see stock xr6ts with nothing more than a tune claiming 1000Nm.
Dyno in 3 gears and get 3 different results. If you want true engine torque, get an engine dyno.

Postby **NitroDann** » Mon Jun 13, 2011 1:25 pm

To calculate power you need rpm and torque. The only way to find rpm on a dyno is to know gear ratio and rollout.

Im sure mine makes 500nm in first gear at the wheels, but that proves nothing about the engine torque.

Dann

Sean · Postby **Sean** » Mon Jun 13, 2011 1:33 pm

NitroDann wrote:To calculate power you need rpm and torque. The only way to find rpm on a dyno is to know gear ratio and rollout.

Im sure mine makes 500nm in first gear at the wheels, but that proves nothing about the engine torque.

Dann

Or an inductive pickup on a plug lead...

Hellmun · Postby **Hellmun** » Tue Jun 14, 2011 11:44 pm

As Sean said it's just the gearing, last time my car was run on the mania Dyno I noticed I was about 40kph slower on peak speed compared to other cars. This works out to be that the car was run in 4th gear instead of 5th. Which is 1.25:1 ratio off the gearbox instead of a direct drive. Further compounded by the fact I run a 4.1:1 final drive ratio power figures are lowered and torque figures increased (my car made 90kw but 298nm).

Horsepower = 33,000 foot pounds moved in 1 minute according to Watt. Gearing changes how much you *move* the weight(distance). So assuming a constant RPM this means you will see a reduction in torque on tall gearing but more power. Power = change in work divided by time. Change in work is further broken up into distance * weight (feet per pound). Hence assuming RPM was constant Torque = (5252 * Power)/RPM and with Power and Torque being the only 2 variables it proves they have a direct relationship.

The 5252.1 constant is just a different formula method for getting there. It's 33,000/(2*3.14 ) or 1hp/ (2*pi) which is the mathematical point where you reach a 1:1 relationship. In the above formula Torque = (5252 * Power)/RPM if RPM = 5252 it's cancelled out.

I never liked Physics until I got into racing... it comes in so useful now though. Good timing as I was only just reading up about exactly this subject in an engine airflow book and it explained why I've seen such different dyno outputs over the years.

Apologies if it's difficult to read, there's only so much you can do with ubb code to display formula's :cry:

Postby **NitroDann** » Wed Jun 15, 2011 12:56 am

I understand all of that. But what your saying is that these stupid torque figures are just uncorrected figures? If you dont give final drive correction how is the figure useful? I could do all my pulls in first and make 90 kw and 800nm.

Dann

Sean · Postby **Sean** » Wed Jun 15, 2011 2:45 am

NitroDann wrote: But what your saying is that these stupid torque figures are just uncorrected figures?

298Nm with 90kw in Hellmun's car on the same dyno would suggest there's an issue there, correction error is the most likely explanation. I'm sure I already thought that.

I don't think anyone thinks these are genuine engine torque numbers, like I said, want those, get an engine dyno. I think we are all agreeing the figures are high, the question is simply why? I still think it's correction errors.

Mania may not understand it all (or at least not as well as you) or they may just not really care and simply use the dyno to help tune cars where run on run comparisons mean more than the number itself. Again, I've never seen them tune or use the dyno, so they may be great and know the answer.

Maybe one of them can chime in and solve it. We've taken BR's topic way off track, but interesting. Maybe we should get a mod to split topic it?

Postby **Boyracer** » Wed Jun 15, 2011 7:07 pm

Had a big day today...finished fitting wiring and plumbing, made intake...engine is all done.

Also fitted locked diff and it's ready to go to MX5MANIA tomorrow.

Hellmun · Postby **Hellmun** » Wed Jun 15, 2011 7:23 pm

The passenger side of the engine bay is so empty in that car, it just cries something is missing but I guess that's the benefit of no ABS, Strut brace or CAI on that side. Goodluck on the Dyno, should be a blast on the track. Where's the CAI go down to?

Dan - I never got asked my final drive ratio so I assume it's just the correction factor. Maybe with the original 3.606 diff the 6 speed in 4th is better comparable to a 5 speed with a 4.1. Regardless of the logic I'd say it's a safe bet you have your explanation and most of the NSW cars all have dyno outputs from there.