https://drive.google.com/file/d/1hbLI9DBikD4t9hSfEVFO2tGfPsHl7lz_/view?usp=sharing

Sorry I couldn't find the attach file button so I linked it this way.

Cheers,

Rich.

it is all about how you tie the car down, alot of dynos dont have a proper vertical pull down system, if you look at dyno dynamics on youtube and you will see their rear bar pull down system, i went to that type of system and no more issues

I 2nd what boz race engines said about the way you strap the vehicle to the dyno. Did that back in  year 1995 no issues with big horsepower cars.

For chassis dynos DD's tie_down system works the best.

I have shared the information on here before easy to find do a few searches on here.

Cheers for your replies.

I'm in the process of doing something similar to DD's method that you mention at the moment.

Any advice on strapping down decent powered IRS cars? This is also an issue for me I believe.

One more thing, can someone please shed some light on where the "attach file" button is on this forum?

TIA

Rich

https://yourdyno.com/community/questions-and-answers-questions-and-answers/an-other-bosch-fla-203-conversion/paged/4/#post-3653

How to use the Dyno Dynamics HP Traction Control!

https://m.youtube.com/watch?v=Z_k9mu3Q_1I&t=183s

For wheel spin a (counter intuitive) trick is to use WD40 on the tires. Still need good tie down though. 

WD40 = cheap PJ1 TrackBite sticky stuff

Select " chooce file " is what i use on my mobile telephone your display might be different.

IRS   is a bit tricker .... i have made various bolt_on brackets for the range of vehicles i have tested over the many years , only use it on high horsepower  vehicles. Still utilising the DD's tie down pull down method.

IRS rear ends are a pain in the but!  BUT still possible to control the traction on the rollers.

Thanks to everyone for their input.

I will try a few things as suggested and report back.

Thanks again

After doing some more testing and strapping correctly I have eliminated wheel slip as a problem, thanks all for the advice.

Can someone shed some light on the attached picture?

I'm getting RPM errors which seem to spike at the same time I have a torque/power dip.

I will also attach a .csv of the runs when I was testing, one of the runs was inertia only and the rpm errors were not present.

Any help would be greatly appreciated, I'm pulling my hair out atm.

Cheers

As mentioned above.

Hi,

Just a clarification first. RPM error is not really an error, it is just the difference between the target RPM and the actual RPM. There will always be a difference, it is what drives the PID controller. We tune it to be as small as possible. 

A few observations:

You have a drop in power/torque between 4000 and 4200 RPM. Is this something the engine does? If not this looks like slip. The RPM vs time looks fine, so it is the load at the load cell that drops off. 

Your PID parameters seem a bit off. The RPM curve is without oscillations (unless masked by have heavy filtering, which filtering did you use). Kp is low I think, but it is hard to say without knowing more. What are your parameters? 

The RPM error you see is not really a problem for a Power sweep, as we only need a smooth sweep without oscillations. You don't get a better result when RPM error is less, it is much more important to have a smooth sweep. 

Hi,

Thanks for your reply, the torque dip at 4200 I'm pretty sure is not engine specific. I had another car on the dyno and similar issues were occurring at a similar rpm.

I will attach the config at the time of testing, I have tested so many different combinations of PID settings and I really am confused at this point.

The rollers and tyres are so grippy atm I really don't think its slip, that and the fact the car is on 8-9 psi it really is not making huge amounts of torque.

Thanks again for the help.

Cheers

Please see attached Power sweep to 5k

Posted by: @radics1

You can clearly see on the video,that under boost the car is coming out of the rollers and driving only the front. This will make a measurement error,because the inertia of the rear rollers become 0,but the software still calculates them. Do you have a rear strapping as well? 

Is that the case if they're unlinked idler rollers?

I only have a speed sensor on the load roller so I thought it was acceptable for it to climb a bit, as long as not to go past the apex of the roller.

I have replaced the speed sensor recently as I was using an encoder, I'm now using the gt101 hall effect and on closer inspection my trigger wheel may have a damaged tooth.

Does it look acceptable or am I better off getting a new one?

Cheers