Race Technology AP-22 Performance Meter

[danwhiley]

Great toy and very good for assessing how your driving is. Not the most accurate device for plotting speeds / position if the circuit you are on is not flat, but I've used mine in particular for:

 

G-Circles - are you really taking that corner as fast as you can?

Testing brake pads - did the new pads stop the car quicker?

0-60mph runs - for impressing people down the pub.

 

Full details on the web-site at Race Technology

 

New one costs £160+VAT = £188. Mine is complete, in a case, with cables - yours for £125. Hell, I'll even throw in the 9v battery for free

 

 

Dan.

[Chris K]

you have mail

[Jason Plato]

If anyone has missed out on this they can also by the one I have - same price / spec etc

 

07771 891947

 

dave

[KenEvans]

Dave - I've left a message on your mobile. How inaccurate is the AP22 as regards speeds on, say, a 1 in 15 hill (ie hillclimb)?

 

Ken

[danwhiley]

For a Hillclimb, the errors will be considerably less. The problem occurs when you let a sample run at lower frequency sample rates over a longer period of time, when the small errors compound.

 

Depends on what you want to do with the data on the Hillclimb? Are you trying to get absolute numbers, or just see if your top speed down a straight is better or worse than previous run? In this latter case, then it's very useful. As I said in the first post, also great for seing if you took the bend to the maximum of the tyres' potential (i.e. how many Gs did you pull, and were you staying near the outer edge of the g-circle?)

 

btw - my logger is still up for sale.

 

Dan.

[KenEvans]

I'd be hoping for a speed trace for the whole course eg 60 seconds are so (albeit downloaded at home) and the G forces would be useful too. It would be used for comparative purposes, however it would be nice to have the actual speeds +-1mph on hills with varying gradients including downgrades. Can it do that?

[danwhiley]

You can sample at 50Hz for 2 minutes - enough for a hillclimb and a bit. This should improve the accuracy quite a lot. However, the issue is one of gravity (!)

 

When going up a hill, the car obviously tilts upwards at the front, so adding a component of gravity to the acceleration figures (think about if the car was stood up on end, the accelerometers would think that you are accelerating at 9.8m/s/s!!). Of course, this is countered somewhat when going downhill and gravity has the effect of slightly reducing the acceleration figure.

 

From my maths calculations, every second you spent going up your 1 in 15 hill would increase the speed by about 1.4mph. Every second you spend going down a similar slope would reduce the speed by the same amount.

 

I guess that by the end of the run, the absolute speed measurement would be much more than you +- 1mph requirements. Comparables would be, eerrm, comparable, as you would be experiencing the sale gradients each run, and the G-forces would still be your best gauge of how well the run had gone.

 

[KenEvans]

Thanks for putting the time into the calcs and your e-mail Dan but I'd too interested in absolute speeds attained (being a fairly shallow sort of bloke) and it sounds like hillclimbing would introduce far too much error. So I don't think it's for me.

 

Somebody buy Dan's or Dave's AP-22 - they sound ideal for sprinting and trackdays