Front wheel pulse sensing

[Euen]

Not sure if this is the right place for this question but I guess it is sort of suspension related.

Has anyone who is rallying an MX5 on Targa or similar events gone to the trouble of mounting sensors on the front wheels to drive Terratrips or similar trip meters.

The ABS front uprights have a sensor mounted which senses a sprocket on the hub. I was thinking of doing something similar but wasn't sure if the ABS sprocket would generate too many pulses. The more pulses you have the more accuracy you can get but I suspect there may be a limit to how far the counters and processors in the trip counters can go.

I would be interested in hearing any info on how you have set things up.

Thanks
Euen

[zorruno]

Has anyone who is rallying an MX5 on Targa or similar events gone to the trouble of mounting sensors on the front wheels to drive Terratrips or similar trip meters.

Hi Euan, from memory, I think you can get pulses directly from an input to the ECU. Not sure where the pickup is though - likely from the drive train.

I assume you need front wheel measurements for accuracy?

cheers

[Euen]

Your assumption is correct. Wheelspin can create significant inaccuracy, particularly if the distances between "instructions" are long.

An accurate trip meter and a good co-driver can make a significant difference to stage times.

But on the point about using the gearbox as a source of the pulses, is there a model of MX5 that uses an electronic sensor for the speedo drive.

E

[MN]

I'm obviously not driving hard enough as the difference between the Terratrip distances and route instructions is insignificant

On gravel I would agree, I recall when rallying in the 70's when stages were 30-100 km (even did a 160 km stage near Gisbourne on one rally!!!) the intermediate distance counter would be 1/10's out.

I run the terratrip from the gearbox but I think it is electronic not a cable drive and I don't have any issues with the distances so maybe it is pulses? You can ses my mechanical ability extends to changing a wheel and that's about it. There again I'm not F/I but even so heaps of wheel spin isn't going to make you go faster.

[Euen]

Thanks Mark

I agree about the discrepancies on gravel. I was also rallying in the mid 70s using a mechanical Halda off the gearbox. The top guys had drilled their front stub axles and were running the cable drive off the front hubs, locked into the bearing dust-cap to overcome the problems caused by wheelspin. I think my longest stage was about 80ks somewhere behind Taihape.

I guess the thing that emphasised to me the importance of having the accuracy was spectating on the recent mini Targa near Pukekohe and seeing the number of competitors, including those at the top end of the entry list, who overshot the 90 left near the end of stage 4. Fortunately there was plenty of run-off and the spectators enjoyed it.

If you are running an electronic sensor on your gearbox, I would be interested in knowing what type it is as I will also be running an electronic speedo in my car so will need something to drive that as well.

Cheers
Euen

[MN]

Sorry Euen I have no idea what sensor is used. I just took the Terratrip to the garage and they installed the connection then took it to an auto electrician for final installation. I know it took quite some effort to install in the gearbox because of the limited working room.

In the Targa Tauranga last year the only time we overshot an intersection (about 3 of them) was when it was cautioned !!! Perhaps thats what happened on the Bambina you watched. In each case we could see there was plenty of run-off and just overdrove and in each case there were plenty of spectators around as well. Funny old thing spectators, somehow they upset the drivers self control and suddenly we think we can out drive Leob!!

What did you drive in the 70's and where? Our first event was in 1974 in the 30 hr Canta Rally which banned service crews - try doing that today!!

[Euen]

We're probably getting a bit off topic here Mark and may incur the wrath of the great Zorruno.

I had a Mk1 Escort 1300. The engine was a little "different" and it revved like stink. I don't think push rods were supposed to rev that high. I started in 76 and did most of the National Championship in 77. Was based in Lower Hutt. Drop me a PM if you want to know any more.

Cheers
Euen

[zorruno]

LOL, I was enjoying this thread too

Incidentally, I have a trip meter that I have never installed from a hobbiest electronics guy in oz - oztechnics. Was in Practical Electronics or something I think originally. Does time/dist/fuel/$$/revs etc & reads off fuel injector and a pulse sensor of some sort. Has 16 char 2 line LCD. Can do logging to a PC too I believe.

I built the buttons etc into my original factory stereo for stealthiness... another unfinished project (raw unit works though)....