speed sensor

[jhanner]

hello everyone im new to the tuning world and im getting my but kicked and any help would be much appreciated my first and main issue is i have an 84 chevy 4x4 with a pulse generator and cant figure out how to get the speed signal accurate

[Taz]

Hello jhanner,

A little more information would be helpful in trying to assist you. What engine & transmission are you using ? If possible, post your current tune.

“Pulse generator” – from Dakota Digital, JTR, or who ? Set to 4K, 8K, or how many pulses ? Mounted on the transmission, transfer case, drive shaft, or where ?

Is the pulse generator wired directly to the PCMs VSS input ? Or the instrument cluster / speedometer ?


Regards,
Taz

[jhanner]

Sorry about the lack of info i installed a 5.3 with a 4l60e and a 208 transfer case the sensor is from abbott enterprise and its connected to the speedometer gear on the output of the transfer case through the speedometer cable and i believe its an 8k pulse. im getting a reading but its showing way too low and its not shifting properly. ill try to post the tune as soon as i can figure out how. thanks for any help

[Taz]

This is from one of Joecar’s posts …

How to attach files:

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Regards,
Taz

[ChipsByAl]

Did this transfer case come with the 1984 truck or the 5.3 combination?
Al

[jhanner]

9290

[jhanner]

it came with the truck and it uses a gear to run the cable

[jhanner]

this is the best ive gotten it the speed reading is close to actual speed and it shifts now but you have to back off the throttle for it to shift and any increase in in throttle will make it down shift im also having issues with it idling it stall out all the time
thanks

[Taz]

OK .. just so I’m clear … you’re running the vehicle speedometer via cable from the transfer case – which also triggers the 8K pulse ?

Is the cable speedometer mechanical calibration reasonably accurate (i.e. correct drive & driven speedometer gears - for tire diameter and differential ratio) such the speedometer readout in the dash is close to actual vehicle speed ?

The mechanical speedometer is 1000 revolutions per mile (OEM) ? This triggers 8000 pulses per mile ?

What is your tire size and manufacturer ? What differential ratio is in the truck ?

Also, you have a 5.3 L engine – your tune is a 2002 OS with a 2001 Camaro VIN – cylinder volume is still 5.7 L – hasn’t been reset to 5.3L – didn’t look much deeper into the tune than that.

Is the 5.3 L stock ? Are you using a Camaro wiring harness ?

If the engine is stock, I have a 2002 5.3 L 4L60E 4 x 4 tune that you’re welcome to – might make tuning a little easier.

My apologies for all of the questions – a lot a mixing and matching in your setup !


Regards,
Taz

[jhanner]

ok ill start from the beginning and again i greatly appreciate all of your help. i bought an 02 4x4 with 4.8 that rolled over. i had a core 5.3 and rebuilt it, i raised the compression a little and some minor port work and a 224 on a 112 cam. i completely rebuilt the transmission and it has a transgo shift kit and a 2500 stall. i used the computer and wiring harness from the 4.8 and just i used the 02 camaro os from holden crazy because it was the closest thing to my mods i could find. ok so since the my front end uses a passenger side drop transfer case i had to use the 208 which came with the cable drive speedometer so i used the pulse generator to get my signal and keep my speedometer cable. the speedometer in the truck is off by 10 mph and i am unsure of the pulses that it produces but the pulse generator produces an 8k signal. the tire size is a measured 38 inches and the gear ratio is 5.13. i would be glad to give your tune a shot cause this thing runs like crap, thanks again.

[Taz]

Thanks for the additional information ... helps to sort things out ... mentioned your speedometer to not accurate .. this will effect the pulse generator output. Mentioned it was out by "10 MPH" ... looking for a percentage to figure out proper values ... 10 MPH at 60 MPH (ie. shows 60 MPH when the actual vehicle speed is 70 MPH) ? Tire diameter is exactly 38 inches per the manufacturer ?

Will then try and come up with values to improve VSS accuracy.


Regards,
Taz

[jhanner]

the speedometer in the truck is 10 mph fast so when im doing 60 according to my speedo im actually doing 50 and the actual tire size is 38 inches tall and 40-14.50-17 is the size written on the sidewall

[Taz]

I attached several tunes below … potential for none of them to be accurate, until you arrive at an accurate displayed speed of the cable driven speedometer.

When properly calibrated (drive & driven gears) the cable speedometer will receive 1000 cable revolutions per mile. Your “pulse generator” is driven off the speedometer cable – designed for 8000 pulses per mile – but only if the cable accurately provides 1000 revolutions per mile. This is equivalent to 8 pulses per revolution, or an 8 tooth VSS pickup.

Displayed speed (or error) is a ratio - if the speedometer reads 10 MPH too fast at 50 MPH, it will read 20 MPH too fast at 100 MPH. For your speedometer to read 10 MPH too fast at all speeds, as you described, is unusual. If true, then there is a problem within the speedometer itself in the gauge cluster.

The next issue is that the software won’t accept 8 pulses per revolution (H0102) - 10 pulses appear to be the minimum acceptable value. While maintaining a tire diameter of 38 inches, this meant adjusting the gear ratio to 4.11 to correspond to 10 pulses per revolution (same output as 5.13 gears with 8 pulses per revolution). “Fudging” this data should provide the PCM with an accurate VSS input - but you can no longer use the speedo calculator function to appropriately adjust the transmission shift points - have to calculate these values externally and import them.

Took a quick look at your tune - “spikes and holes” in your Main VE Table (B0101) and in your MAF Sensor Calibration (B5001) - these would benefit from further tuning.

The tunes below:


2002 Camaro OS - VSS & shift speeds reset.tun

this is the tune you posted (truck 3)
modified VSS parameters (to work with cable driven 8K pulse generator)
modified shift speeds from a base Camaro tune - to work with 5.13 gears and 38 inch diameter tires


2002 Silverado OS - VSS & shift speeds reset - Z06 VE.tun

this was a stock tune
modified VSS parameters (to work with cable driven 8K pulse generator)
modified shift speeds from a base Camaro tune - to work with 5.13 gears and 38 inch diameter tires
added a 2002 Z06 VE table - definitely not a perfect match for your camshaft – but closer than the stock table


Stock - 2002 Silverado 1500 LM7 5.3 L 4L60E 4 x 4.tun

stock tune - as a reference
In the end none of these may work right for you … hopefully one will, or hopefully this assists you in finding a solution.

Regards,
Taz

[jhanner]

ok i didnt get a chance to try it till late last night, it is still getting a slow signal whereas its only reading maybe 5 mph when the truck is going about 20 mph. it also runs whole lot better but its still stalling out. i wonder if there is a diferent setup i should try maybe a diferent pulse generator? im not sure though and thanks again

[Taz]

Sorry to hear VSS speed is still way off ... looks like a magnitude of 4 ... had to set it to 10 pulses ... any possibility that your pulse generator is a 40K setup ?? May want to double check with the manufacturer regarding the exact number of pulses per speedometer cable revolution. If it ends up being a number different than 8 pulses per revolution, or 8K per mile (1000 cable revolutions) ... let me know and I can adjust the settings.

You mentioned it ran "better" - what tune did you end up using ??

Once you get an accurate VSS speed, the idle should improve - then you could move on to tuning the idle.

Regards,
Taz

EDIT: applied the math in reverse - if VSS speed was 4 times too fast then 40K generator. Given VSS speed is 4 times too slow, perhaps 2K or 4K generator.

[jhanner]

ill give them a call just to double check to make sure and i ended up using the tune with the z06 ve table.

[jhanner]

ok i talked to them and they said that it was defenitly 8k pulse generator

[Taz]

Give this tune a try ... the solution may have been in logic, not tuning ...


Regards,
Taz

[jhanner]

ok ive been working on it all day i have the speedometer in the truck within 2 mph of the actual speed and i had to put the h0104 to 1000 and now its shifting but it is showing a very low speed signal for example at 50 mph the computer is showing around 25 mph. its shifting but its not quite right. its also still stalling out while coming to a stop unless you keep on the throttle, but seems to do it with which ever tune i try im wondering if its something wrong with the truck ive checked for vacuum leeks and didnt find anything. does a 4.8 have the same injectors as a 5.3? what books anyone recommend for a beginner? thanks for all the help

[jhanner]

ok ill that one a try tomorrow thanks taz

[jhanner]

i got a chance to try it out this morning and it worked great, it shifts right and showing the speed almost dead on. i really apreciate all of your help

[Taz]

Great to hear it worked. Sometimes I get so focused on entering precise data for the PCM to work with, that I forget to use my own brain !

When you mechanically calibrate your cable driven speedometer (drive & driven gears), it should cause the pulse generator to output 8K pulses per mile – if the mechanical calibration is accurate.

The solution ended up being painfully simple – set pulses per mile (H0101) to 8000. This can’t be done directly, so I left your tire diameter at 38 inches (needed to use 37.99), and adjusted the final drive ratio (H0103) until the calculated value of H0101 was 8000 pulses per mile (or 4971 pulses per Km).

On previous tunes, where various gear and tire values had been entered, had caused the software to “calibrate” the speedometer a second time – after you had already done this mechanically.

The current tune values for H0101 through to H0106 should never be changed or updated – for as long as you use the 8K pulse generator. Future changes to gear ratio / tire diameter must be calibrated mechanically by changing the drive and / or driven gears that turn the speedometer cable.

You can still use the Shift Point Correction function (to make global changes to transmission shift values) - but only if you enter a percentage – do not alter tire diameter or diff ratio values as shown.

I still learn something almost every day !!


Regards,
Taz