Vehicle Speed Sensor Problem with Gear Ratio Upgrades
07-10-2001, 04:33 AM
#11
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In addition to the J's & ATS increased gear ratios, I believe Spoon has a "close gear ratio" set of transmission gears. This would also get us moving quicker and, with the shorter gearing, make it easier to stay in v-tech.
I'll e-mail Mingster (Import Development) to see if he has the ratio information to post. Then maybe Luis, Sev, DavidM and others can compare Spoon's ratios with the ratios they've been developing.
I'll e-mail Mingster (Import Development) to see if he has the ratio information to post. Then maybe Luis, Sev, DavidM and others can compare Spoon's ratios with the ratios they've been developing.
07-10-2001, 09:14 AM
#12
Not that I have time to work on this now, but you might be able to get by with a simple "pulse remover" circuit. If you build a digital counter you could set it up to ignore every N'th input pulse. The stock speed sensor puts out about 44 pulses per second per mph, removing one pulse out of every 10 or 11 would almost assuredly not be missed by the speedo - it responds so slowly that the "hiccup" wouldn't be a problem.
The only problem I could forsee with this simple fix would be if the ECU reacts too quickly to speed input changes. With this fix, the speed output would read (for example) 40 mph for 1/10 second, then 20 mph for 1/100 second, then back to 40 mph. As long as the ECU averages over time you'd be alright.
The only problem I could forsee with this simple fix would be if the ECU reacts too quickly to speed input changes. With this fix, the speed output would read (for example) 40 mph for 1/10 second, then 20 mph for 1/100 second, then back to 40 mph. As long as the ECU averages over time you'd be alright.
07-10-2001, 09:20 AM
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[QUOTE]Originally posted by 4373
[B]In addition to the J's & ATS increased gear ratios, I believe Spoon has a "close gear ratio" set of transmission gears. This would also get us moving quicker and, with the shorter gearing, make it easier to stay in v-tech.
[B]In addition to the J's & ATS increased gear ratios, I believe Spoon has a "close gear ratio" set of transmission gears. This would also get us moving quicker and, with the shorter gearing, make it easier to stay in v-tech.
07-10-2001, 12:19 PM
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Originally posted by mingster
You don't want the Spoon's final gear set. The ratio is 4.3, but I can't justify charging what I have to charge for the Spoons. Get the ATS or J's.
You don't want the Spoon's final gear set. The ratio is 4.3, but I can't justify charging what I have to charge for the Spoons. Get the ATS or J's.
http://www.spoon-sports.com/
but I was not sure if this was for our car or only Integra.
07-10-2001, 01:13 PM
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*remembers EE classes thru the haze in his brain*
basically you're using the pulse from the sensor to "tune" a secondary frequency transmission to the engine. you need a pulse generator and a DLC to transmogrify the sensor's pulses into the right signal to tune the pulse generator to the proper frequency. assuming it's a digital transient, not an analog from the sensor. if it's analog then you do some other funky stuff related to FM (Frequency Modulation) radio transmission.
remember, this will slow down the speedo signal to your display by some fraction of a second.
basically you're using the pulse from the sensor to "tune" a secondary frequency transmission to the engine. you need a pulse generator and a DLC to transmogrify the sensor's pulses into the right signal to tune the pulse generator to the proper frequency. assuming it's a digital transient, not an analog from the sensor. if it's analog then you do some other funky stuff related to FM (Frequency Modulation) radio transmission.
remember, this will slow down the speedo signal to your display by some fraction of a second.
07-10-2001, 03:21 PM
#16
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The pulse dropping idea sounds interesting. Simple, if not necessarily elegant (I tend to favor simplicity).
In terms of the frequency shift model, there are a couple ways to do it. Since the output from teh sensor is essentially a variable frequency square wave, we could use that a trigger for a simple op-amp circuit. The other possibility would be to treat the signal as a digital output and convert to analog. It would then be simple to scale that output and reconvert to digital.
Either way, there will be a slight degradation in response time, but as the stock speedo seems to take nearly 1 second to catch up when you stop accelerating at low speeds, it would probably be unnoticeable.
UL
In terms of the frequency shift model, there are a couple ways to do it. Since the output from teh sensor is essentially a variable frequency square wave, we could use that a trigger for a simple op-amp circuit. The other possibility would be to treat the signal as a digital output and convert to analog. It would then be simple to scale that output and reconvert to digital.
Either way, there will be a slight degradation in response time, but as the stock speedo seems to take nearly 1 second to catch up when you stop accelerating at low speeds, it would probably be unnoticeable.
UL
07-10-2001, 05:32 PM
#17
Ultimate -
If you just took the input square wave (3.5 v p-p) into a frequency-to-voltage converter ($4 IC) then fed that to a voltage-to-frequency converter (another $4 IC), you might have something workable. And not too expensive. I used one of these for my shift indicator and auto-volume control.
Question - does the ECU really need to know the true speed? Would 10% error make a significant difference? I'm sure engine rpm, airflow, and throttle position are more significant factors than actual vehicle speed. Speed doesn't give any indication of engine load (weight of vehicle, uphill or down, headwind etc). Point is, if the ECU is not that picky, we are only adjusting the speedo, and we KNOW it doesn't give a rat's ass.
If you just took the input square wave (3.5 v p-p) into a frequency-to-voltage converter ($4 IC) then fed that to a voltage-to-frequency converter (another $4 IC), you might have something workable. And not too expensive. I used one of these for my shift indicator and auto-volume control.
Question - does the ECU really need to know the true speed? Would 10% error make a significant difference? I'm sure engine rpm, airflow, and throttle position are more significant factors than actual vehicle speed. Speed doesn't give any indication of engine load (weight of vehicle, uphill or down, headwind etc). Point is, if the ECU is not that picky, we are only adjusting the speedo, and we KNOW it doesn't give a rat's ass.
07-17-2001, 09:19 AM
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This mod will make or break my decision to get J's final gear. I'm sure alot of you are thinking the same thing...has anyone had a breakthrough in developing a circuit to fix the odometer/speedometer? I'd try it, but it's not my field and I don't really have a clue about where to begin. I'd be willing to purchase one that works from anyone that can make it though. 
07-17-2001, 07:30 PM
#20
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Wake et al,
I believe I've found a very simple circuit that will do the job with off-the-shelf, readily available ICs.
I need to pick up some parts and dig up my breadboard to try it. I'll take some measurements this weekend on the VSS output (others have posted the basics, but I need to get specifics with my own two hands - o.k., multimeter).
If all goes well, I should be able to put together a little box that will allow you to select the rear end ratio, or just a stock correction factor (4-5% taller?). I could always throw in an extra large correction factor for those with lease mileage issues :-).
UL
I believe I've found a very simple circuit that will do the job with off-the-shelf, readily available ICs.
I need to pick up some parts and dig up my breadboard to try it. I'll take some measurements this weekend on the VSS output (others have posted the basics, but I need to get specifics with my own two hands - o.k., multimeter).
If all goes well, I should be able to put together a little box that will allow you to select the rear end ratio, or just a stock correction factor (4-5% taller?). I could always throw in an extra large correction factor for those with lease mileage issues :-).
UL