serieslandy
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| posted on 6/12/13 at 06:13 PM |
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Race Technology Problems Wheel speed and rpm
Hi Guys, I'm having problems with my race technology dash 2 (everyone seems to)
I've installed a hall effect sensor to do the wheel speed, working off the 4 diff-prop bolts.
The problem I'm having is the calculations them not displaying correctly. I think I've worked it out correctly as follows:
Tyres 195/50/50 = 1.80956m circumfrence
4 bolts on the prop
3.92 ratio diff
1609(rt figure)/1.8m = 889.1 x 4bolts = 3556 (which reads about 50mph at 10-15mph)
x 3.92 = 13942
Which is great (gave a roughly correct reading) but the dash only goes to 12000. Are my calculations correct and if so, am I going to have to move the
sensor? (push in diff btw so can't take it off the drive shaft bolts)
My other question is about the rpm sensor. I'm running a totally stock pinto, I know I can't take the tacho output from the coil to the
dash 2 without damaging it. Is my only real option a hall effect sensor and a tigger wheel? or is there a more cost effective way of sorting it. This
bit is kind of holding me up from finishing my dash wiring.
I hope someone can help, you did last time.
Cheers, Steve
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v8kid
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| posted on 6/12/13 at 06:42 PM |
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Intuitively shouldn't you divide by diff ratio?
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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serieslandy
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| posted on 6/12/13 at 06:44 PM |
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That's what I first thought but I was doing 50mph pulling out of my garage so I guessed not!
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Dave Bailey
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| posted on 6/12/13 at 06:54 PM |
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Not going to help much but I picked up off the front right wheel using an abs sensor and mine is pretty much spot on... From memory it is about 3600
pulses I entered...
Probably worth mailing the guys at Race Technology to see if there is anything they can do or have.. I have found them very helpful.
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AndyW
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| posted on 6/12/13 at 07:40 PM |
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quote:
Originally posted by serieslandy
Hi Guys, I'm having problems with my race technology dash 2 (everyone seems to)
I've installed a hall effect sensor to do the wheel speed, working off the 4 diff-prop bolts.
The problem I'm having is the calculations them not displaying correctly. I think I've worked it out correctly as follows:
Tyres 195/50/50 = 1.80956m circumfrence
4 bolts on the prop
3.92 ratio diff
1609(rt figure)/1.8m = 889.1 x 4bolts = 3556 (which reads about 50mph at 10-15mph)
x 3.92 = 13942
Which is great (gave a roughly correct reading) but the dash only goes to 12000. Are my calculations correct and if so, am I going to have to move the
sensor? (push in diff btw so can't take it off the drive shaft bolts)
My other question is about the rpm sensor. I'm running a totally stock pinto, I know I can't take the tacho output from the coil to the
dash 2 without damaging it. Is my only real option a hall effect sensor and a tigger wheel? or is there a more cost effective way of sorting it. This
bit is kind of holding me up from finishing my dash wiring.
I hope someone can help, you did last time.
Cheers, Steve
1609(rt figure)/1.8m = 889.1 x 4bolts = 3556 (which reads about 50mph at 10-15mph)
isn't that sum that you show here multiplying by the diff ratio, should you be dividing? 3556 divided by 3.92 = 907.14
just a thought??
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jeffw
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| posted on 6/12/13 at 07:41 PM |
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OK.....
1609meters in a mile/1.809m circumference = wheel revs per mile 889.44
(wheels revs per mile*diff ratio) = propshaft revs per mile
889.44 * 3.92 = 3486.6
propshaft revs per mile x 4 = 13946.4
Brain in a jar first time. Prop revolves 3.92 faster than the wheel .
You need to remove 2 of the magnets
[Edited on 6/12/13 by jeffw]
[Edited on 6/12/13 by jeffw]
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daviep
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| posted on 6/12/13 at 08:15 PM |
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I agree with your maths, obviously the prop is going faster than the wheel speed so you do indeed need to multiply by the diff ratio.
If there isn't a simple solution how about fitting tabs under two of the diff bolts and moving the sensor so that it only sees the tabs thus
halving the number of pulses.
Cheers
Davie
“A truly great library contains something in it to offend everyone.”
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avagolen
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| posted on 6/12/13 at 08:31 PM |
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Beaten to it.
I would do what Davie suggests and add 2 tabs.
Get some repair washers and cut them to size and then make them 'L' shape.
Have fun.
The Answer for everything, but never the last word....
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serieslandy
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| posted on 6/12/13 at 09:33 PM |
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Cheers guys. I like the simple solution. I'm guessing by repair washer you mean the same as penny washer?
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serieslandy
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| posted on 6/12/13 at 09:40 PM |
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quote:
Originally posted by jeffw
OK.....
1609meters in a mile/1.809m circumference = wheel revs per mile 889.44
(wheels revs per mile*diff ratio) = propshaft revs per mile
889.44 * 3.92 = 3486.6
propshaft revs per mile x 4 = 13946.4
Brain in a jar first time. Prop revolves 3.92 faster than the wheel .
You need to remove 2 of the magnets
[Edited on 6/12/13 by jeffw]
[Edited on 6/12/13 by jeffw]
I had the same original thinking Jeff but came to the same conclusion. No magnets just prop bolts so don't exactly want to remove them,
I'm going to have a go at extending 2 forwards with washers so the sensor only pics up 2.
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jeffw
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| posted on 6/12/13 at 10:05 PM |
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Or move the sensor to the front disc....Don't Race Technology do a magnetic pick-up as well? I epoxyed a rare earth magnet to the inside of
the rear wheel and ran the sensor next to that....worked fine.
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Dave Bailey
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| posted on 6/12/13 at 10:37 PM |
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I attached mine to the upright and picked up on the rear of the wheel studs... Works a treat....
Dave B
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serieslandy
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| posted on 6/12/13 at 11:13 PM |
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Dave, did you have the sensor at 90deg to the wheel studs or parallel?
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Dave Bailey
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| posted on 7/12/13 at 08:41 AM |
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Parallel... Can send you a picture if you want... Actually did me a favour at Iva because they didn't check the speedo I just had to prove I had
it set up correctly. I am not saying this would be ok for all testers....
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serieslandy
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| posted on 7/12/13 at 08:45 AM |
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If you don't mind that wouldbe great. I'll be using Southampton as well so possibly the same guy.
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Dave Bailey
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| posted on 7/12/13 at 08:48 AM |
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O didn't see you were in Portsmouth... I'm only in Horndean...
[Edited on 7/12/13 by Dave Bailey]
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serieslandy
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| posted on 7/12/13 at 09:14 AM |
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It's a small world. I live in rowlands and work at keydell.
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Dave Bailey
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| posted on 7/12/13 at 09:17 AM |
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:-).... I'll pop over at some point... You can have a look....
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Dave Bailey
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| posted on 7/12/13 at 09:18 AM |
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How far are you off going to IVA?
Dave B
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serieslandy
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| posted on 7/12/13 at 10:02 AM |
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Not too far off iva. Aiming for early spring but have run out of money at the moment.
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jeffw
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| posted on 7/12/13 at 12:14 PM |
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Of course if you use the wheel bolts you are 3.92 times lower so will easily get a figure that will work.
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serieslandy
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| posted on 7/12/13 at 01:41 PM |
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Cheers guys, I'm going to have at getting it to pick up only 2 prop bolts with the use of some washers, (around 6500 pulses). If that
doesn't work I'll move it to the front upright.
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serieslandy
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| posted on 7/12/13 at 08:10 PM |
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Well I solved one problem and created another!
I installed 2 tabs on the prop bolts tonight and took the car for a spin. The dash was reading roughly the correct speed but when it got to 25mph just
stopped working.
I've put a post on the race tech forum but it seems kinda dead. Has anyone else seen a problem like this?
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Dave Bailey
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| posted on 7/12/13 at 08:14 PM |
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Do you mean it still reads but only up to 25 or it is dead completely?
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serieslandy
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| posted on 7/12/13 at 08:27 PM |
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It will do 1-24mph then nothing and picks up 24mph when you drop down again.
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