JoeMag

Any had their AIM dash setup to read the stock wheel speed sensors on 993?

John H

No. We used the sensors you mount on the inner CV joint on my old 993 for the Pista.

Would you finish the car already? Are you going to the April NASA event? I think I am going to volunteer and watch.

JoeMag

Unfortunately no... I'm pretty much done with the pumping planning/layout having hoses made and moving on to electricals soon.

I did just get a punch in the face today on cage rules in something I caught on the gts forum yesterday for a rule that could be clearer, and am probably going to need to take a trip back to cage shop. Just finished painting the interior too.

Gary R.

NASA GTS Joe? Mind enlightening me, i'm installing my cage in the next couple days..

Sean F

Joe, before you jump off the ledge what was the issue? The scruts don't go nuts on cage construction when they issue a log book.

APKhaos

Joe,
Most loggers expect to see one pulse per revolution from wheel speed sensors, and have their analytics set up to reduce this pulse rate to equivalent speed. The ABS sensors deliver 60 or so pulses per revolution [count the teeth on the ABS sensor ring for the actual number].

First question is, "Can the MXL wheel sensor channel handle 60x the design pulse rate?" If yes, then its a fairly simple matter to add math channels to pre-process the pulse rate data to produce wheel speed. This is going to require some research on the MXL analog channel capability, and if that's OK, some custom work to add the appropriate math channels to Race Studio.

Given that deriving speed from wheel sensors has inherent innacuracies to begin with, you might want to think about adding the GPS option to your MXL setup as an alternative. This will give far more accurate speed data, and may be a better option than fiddling with wheel sensors.

Geoffrey

Tony, its not that simple, You do not want to tap directly into the ABS sensors IF the ABS system is still retained. The sensors are voltage producing sensors and require a 0v (floating ground) to reference against. You can't put two devices, each with a 0v reference on the mag sensor and expect it to work properly. So, the answer is, if the ABS sensors are used, BUT the ABS system is not in place, then IF the AIM can translate analog to digital AND can handle the high frequency it produces with 45 or 48 teeth, then it can be used. If not, then some other method will be required, like using hall sensors measuring CV bolts or a magnet on the axle, or something like that.

This is not necessarily a true statement, depending on how many wheel speeds are monitored, and how accurate you calibrate the sensors, and what algorithm the data logger uses, it may be very accurate.

MoTeC for instance is extremely accurate when using wheel speeds, especially if you measure all 4. It can receive either mag (analog) or hall (digital) input to count the number of teeth up to 3200hz. With that, it can measure 48 teeth on an ABS ring no problem.

Gary R.

Well, I added the cross brace from drivers head to floor and also am adding a 2nd driver's door bar and a halo to my Kirkey seat. Hope that cut's it as far as the diff between NASA and PCA...

FredC

Magnet on axle is simple and seems to work great.

APKhaos

Geoffrey, thanks for that clarification. Must admit most of our work is now GPS, so we rarely play with wheel sensors. Using the ABS speed sensors seems an unlikely alternative.

FlyingDog

corrected below.

JoeMag

Sean, my experience (or what I've seen from my colleage's), is now the cages are looked at pretty close (at least in our region). ...know several folks who were denied log books because tube wasn't 360 welded (like 1/8" short). I can say that in the beginning cages were not looked at that closely as I raced in some of nasa's first races here in Ohio.

Gary, my issue is the diagonal main hoop brace. It must be one continueous piece and horizontal brace (seat belt bar), must be two.

Regarding the AIM Dash, I talked with AIM and it's definately not fast enough to use the abs sensor. It can read 50hz and a 25" wheel at 180mph (yea, i will not get going that fast), is going at 41 rev's/sec so we're talk'n single pulse per rev to get below 50hz.

I do have the AIM gps setup, but I want to monitor all 4 wheel speed for detection of wheel lock up. I have a call back to AIM to see how how fast this thing does the speed calc.

Circuit Motorsports

Which dash are you using. I am assuming the MXL Pro.

JoeMag

Regarding dash, I know where you're going but, you probably already know this, AIM is coming out with 4 wheel multiplexer for pista. good price to ~$200. that is also in my question to the gent who owns AIM sports in CA of how it's time slicing data.

Circuit Motorsports

Yeah that's where I was going. So you are using a MXL Pista?

The only data I've seen on an AIM dash that has had four wheel speed inputs was on the MX-5 cup cars and 'i think' they were pulling that info from the car's computer not from AIM sensors.

The differences some of the wheels were showing, for example the inside rear tire would get a 2-3mph spike over a 1 second period from spinning through the kink at Road America. I think the rate it will collect the data from all four wheels will be more than enough to notice.

The guys in CA will be able to get this sorted out for you. They are top notch.