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crazydiablo · 17th November 2010, 07:56

Just consider the rally car to be a reference point, nothing else. If they had a curve for a stock car I would have preferred posting that. I couldnt get anyone with a stock baleno to come with me.

Anything this will be again a reference point for the next run, so all in all good.

Sutripta, am not really sure about dips, which I am yet to discuss with Ron. The first dip seems to be because of the way they dyno the car I think. Am not too sure about that also, but it seems to be there in all the dyno charts. Check out the charts of Red rage.

Avinash_R · 17th November 2010, 11:00

nicely modded car.. If you are still bent on selling it, please post your ad in the new classifieds. The old one is not present anymore.

Sutripta · 17th November 2010, 20:30

Quote:

Originally Posted by crazydiablo

...
Sutripta, am not really sure about dips, which I am yet to discuss with Ron. The first dip seems to be because of the way they dyno the car I think. Am not too sure about that also, but it seems to be there in all the dyno charts. Check out the charts of Red rage.

Hi,
Yes, you are right. The first dip seems to be a dyno artifact. Still, the difference in rpm is puzzling.

A couple of questions since you were there:

Was the car jacked up on the lower arm, or the chassis?
What was done to the other wheel? (How do you ensure no differential action)
OT: The brake- was it a Telma, or something else?
OT: Did anyone get a bike dynoed? (Incidentally, how do you dyno a non CV carb bike on an inertial. Would like to compare brake and inertial type readings in that case.)

Regards
Sutripta

crazydiablo · 17th November 2010, 20:53

The car was jacked on the chassis. Both the front wheels are connected to the dyno and matched for rpm.

I am not sure about the brake.

Its a car dyno, I doubt a bike can be dynoed on this.

Sutripta · 17th November 2010, 20:58

^^^
Wonder how much of an effect driveshaft angles will have.
How is rpm matched?

Bike:- adapter at drive sprocket?

Regards
Sutripta

Vid6639 · 17th November 2010, 21:27

Sutripta, car was jacked only to remove the wheels, once wheels were removed the hubs were bolted on then connected to the dyno on both front wheels. Once locked to the dyno jacks were removed.

Sutripta · 17th November 2010, 21:49

^^^^
OK. That means the dynos supported the front weight of the car.

There is no mechanical lock between the two units. How were the speeds matched? Only through the control software?
Does anyone know the powerloss in a differential?

Regards
Sutripta

Vid6639 · 17th November 2010, 22:06

Quote:

Originally Posted by Sutripta

^^^^
OK. That means the dynos supported the front weight of the car.

There is no mechanical lock between the two units. How were the speeds matched? Only through the control software?
Does anyone know the powerloss in a differential?

Regards
Sutripta

There is no lock in between the 2 units. What do you mean by speeds matched? The speeds have to be matched by the car itself. If they weren't the car wouldn't drive straight.

The dyno first performs a calibration to determine the drive ratio at a controlled 2000rpm. After the drive ratio is found and rpm calibrated, the run is started.

Sutripta · 17th November 2010, 22:18

^^^^
Open differential. Same torque (not speed) to both hubs.

Regards
Sutripta

Vid6639 · 17th November 2010, 22:31

Quote:

Originally Posted by Sutripta

^^^^
Open differential. Same torque (not speed) to both hubs.

Regards
Sutripta

That's if the steering is turned, not when dead straight. Anyways if there's no lock what's the issue I don't understand? Like I said they are calibrated by running the setup at 2000rpm.

pranavt · 17th November 2010, 22:33

Quote:

Originally Posted by vid6639

That's if the steering is turned, not when dead straight. Anyways if there's no lock what's the issue I don't understand? Like I said they are calibrated by running the setup at 2000rpm.

Torque steering - Wikipedia, the free encyclopedia

Vid6639 · 17th November 2010, 22:40

Quote:

Originally Posted by pranavt

Torque steering - Wikipedia, the free encyclopedia

Yeah, that's the only way I figured as well, torque steer. In 4th gear even if there is torque steer on the dyno, how will it affect the reading? Just trying to understand.

kutlee · 18th November 2010, 10:44

Quote:

Originally Posted by vid6639

The dyno first performs a calibration to determine the drive ratio at a controlled 2000rpm. After the drive ratio is found and rpm calibrated, the run is started.

The run is done at 4th gear since it is closest to 1:1. There is no drive ratio taken into consideration (to make matters simple lol). also i think the losses were input based on the dyno fellow's discretion

.
the only thing the guy did was match the eninge rpm to the rpm on the dyno at 2000. That too based on the stock tacho on the car which is not accurate.

Sutripta · 18th November 2010, 20:40

First of all, CrazyD, sorry for hijacking your thread. Logically these discussions should belong to one of the dynamometer threads, or to to the Red Rooster thread. Maybe the mods can move it there.

@vid, pranavt. No not talking of torque steer.

Take the case of the dyno attached to one hub with load set, and two extreme cases for the other hub: A) Hub free, and B) Hub locked.

In case A) the free hub will rotate (at 2x), the dyno hub remaining stationary.
In case B) the dyno hub will rotate (at 2x), the free hub remaining stationary.
This is what we see in real life, and is easy to envisage.

If we now attach a dyno to the previously free hub, but with the same two loadings (no load, very high load), we will get the same results.

Because of the open diff, the result will still be the same even if dyno loading is SLIGHTLY higher or lower. Theoretically both hubs will turn at the same speed only if the loadings are exactly the same. Otherwise, one hub will stop turning. Practically we do have a slight spread.

Total power output is the sum of the outputs of the two dynos, so hub speed should not matter. But the differential will come into play, and will absorb some power. Also, a machine constantly trying to correct its braking torque will not be stable. Neither will make for consistent (let alone accurate) readings.

Regards
Sutripta

Jaggu · 19th November 2010, 11:19

Isn't this what they try to rule out with the initial set up run? i saw that rpm of both the wheels were almost same when that reading was taken. They do this couple of time and was done for all cars and the machine calibrates itself and check all parameters like drive ratio etc, after this the actual runs start.

17th November 2010, 07:56	#301
crazydiablo BHPian Join Date: May 2004 Location: Bangalore/San Francisco Posts: 854 Thanked: 24 Times View My Garage	Just consider the rally car to be a reference point, nothing else. If they had a curve for a stock car I would have preferred posting that. I couldnt get anyone with a stock baleno to come with me. Anything this will be again a reference point for the next run, so all in all good. Sutripta, am not really sure about dips, which I am yet to discuss with Ron. The first dip seems to be because of the way they dyno the car I think. Am not too sure about that also, but it seems to be there in all the dyno charts. Check out the charts of Red rage.
	() Thanks

17th November 2010, 11:00	#302
Avinash_R BHPian Join Date: Aug 2008 Location: Bangalore Posts: 404 Thanked: 1,255 Times	nicely modded car.. If you are still bent on selling it, please post your ad in the new classifieds. The old one is not present anymore.
	() Thanks

17th November 2010, 20:53	#304
crazydiablo BHPian Join Date: May 2004 Location: Bangalore/San Francisco Posts: 854 Thanked: 24 Times View My Garage	The car was jacked on the chassis. Both the front wheels are connected to the dyno and matched for rpm. I am not sure about the brake. Its a car dyno, I doubt a bike can be dynoed on this. Last edited by crazydiablo : 17th November 2010 at 20:57.
	() Thanks

17th November 2010, 20:58	#305
Sutripta Senior - BHPian Join Date: Jul 2009 Location: Calcutta Posts: 4,668 Thanked: 6,217 Times	^^^ Wonder how much of an effect driveshaft angles will have. How is rpm matched? Bike:- adapter at drive sprocket? Regards Sutripta
	() Thanks

17th November 2010, 21:27	#306
Vid6639 Team-BHP Support Join Date: Jul 2006 Location: Bangalore Posts: 17,728 Thanked: 43,463 Times View My Garage	Sutripta, car was jacked only to remove the wheels, once wheels were removed the hubs were bolted on then connected to the dyno on both front wheels. Once locked to the dyno jacks were removed.
	() Thanks

17th November 2010, 21:49	#307
Sutripta Senior - BHPian Join Date: Jul 2009 Location: Calcutta Posts: 4,668 Thanked: 6,217 Times	^^^^ OK. That means the dynos supported the front weight of the car. There is no mechanical lock between the two units. How were the speeds matched? Only through the control software? Does anyone know the powerloss in a differential? Regards Sutripta Last edited by Sutripta : 17th November 2010 at 21:51.
	() Thanks

17th November 2010, 22:18	#309
Sutripta Senior - BHPian Join Date: Jul 2009 Location: Calcutta Posts: 4,668 Thanked: 6,217 Times	^^^^ Open differential. Same torque (not speed) to both hubs. Regards Sutripta
	() Thanks

18th November 2010, 20:40	#314
Sutripta Senior - BHPian Join Date: Jul 2009 Location: Calcutta Posts: 4,668 Thanked: 6,217 Times	First of all, CrazyD, sorry for hijacking your thread. Logically these discussions should belong to one of the dynamometer threads, or to to the Red Rooster thread. Maybe the mods can move it there. @vid, pranavt. No not talking of torque steer. Take the case of the dyno attached to one hub with load set, and two extreme cases for the other hub: A) Hub free, and B) Hub locked. In case A) the free hub will rotate (at 2x), the dyno hub remaining stationary. In case B) the dyno hub will rotate (at 2x), the free hub remaining stationary. This is what we see in real life, and is easy to envisage. If we now attach a dyno to the previously free hub, but with the same two loadings (no load, very high load), we will get the same results. Because of the open diff, the result will still be the same even if dyno loading is SLIGHTLY higher or lower. Theoretically both hubs will turn at the same speed only if the loadings are exactly the same. Otherwise, one hub will stop turning. Practically we do have a slight spread. Total power output is the sum of the outputs of the two dynos, so hub speed should not matter. But the differential will come into play, and will absorb some power. Also, a machine constantly trying to correct its braking torque will not be stable. Neither will make for consistent (let alone accurate) readings. Regards Sutripta
	() Thanks

19th November 2010, 11:19	#315
Jaggu Team-BHP Support Join Date: May 2004 Location: Bangalore Posts: 20,215 Thanked: 15,904 Times	Isn't this what they try to rule out with the initial set up run? i saw that rpm of both the wheels were almost same when that reading was taken. They do this couple of time and was done for all cars and the machine calibrates itself and check all parameters like drive ratio etc, after this the actual runs start.
	() Thanks