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BA XR8 Speed limiter..

10K views 32 replies 8 participants last post by  FordTech65 
#1 ·
Hey all,

well, I know that the speed is limited to 230kms... in my testing of the car, I cant seem to get the car over 210-215km/hr... is something wrong with the speed limiter?! whats the deal?! Any suggestions welcome....

cheers.

Thought: I changed the wheels to 19's and havent recalibrated the speedo... could this cause the 15-20km/hr speed difference?!
 
#5 ·
Wheel and tyre diameter is irrelevant. The computer senses wheel speeds meaning the indicated speed on the speedo, the speed seen by the PCM etc are all the same. Unless you're measuring the lower speed via a separate source?
 
#6 ·
If you replace wheels on the car for a different size, you actually need to recalibrate the PCM configuration. The transducer is the primary source of speedo output. Different sized wheels compared to what the PCM is configured to, affects transmission output/ wheel speed sensor, only slightly but if you were hiking it over 200, then you would notice it. Only Ford technicians can adjust this with there WDS (portable computer unit).
 
#7 ·
Most Fords are like this now with there PCM's.
The larger the diameter of the wheel the slower the speedometer reads in relation to the vehicles actual speed (unless PCM is reconfigured) because there is more surface around the tyre to contact the road.
 
#8 ·
will have to get the speedo recalibrated then... cause its a 1cms - 1.5 cms difference overall... Ford said it wouldnt do it and that i have to go to someone private to get it done... will let you know how the second round of testing goes once I get the speedo recalibrated....

Thanks for the resposes, Muchily appreciated.
 
#9 ·
Kypez said:
will have to get the speedo recalibrated then... cause its a 1cms - 1.5 cms difference overall... Ford said it wouldnt do it and that i have to go to someone private to get it done... will let you know how the second round of testing goes once I get the speedo recalibrated....

Thanks for the resposes, Muchily appreciated.
Did you read what I said? The speedo is irrelevant because what you're seeing on the speedo is supposed to be what the PCM is seeing. So if you put on larger wheels you'll get over 230km/h but still seeing 230 on the speedo. :be:

If you want the speedo recalibrated go to that place at Silverwater. I think it's called General Instruments - they used to (still?) do the cop cars.
 
#10 ·
I didnt mean any disrespect Pete... I'm just trying to figure out whats wrong... the thing is that I cant get over 210 - 215... so are you saying that there is a problem with my PCM??!! I'm trying to follow here....
 
G
#11 ·
Aussie Pete said:
Wheel and tyre diameter is irrelevant. The computer senses wheel speeds meaning the indicated speed on the speedo, the speed seen by the PCM etc are all the same. Unless you're measuring the lower speed via a separate source?
It is irrelevant only if the PCM calculates the speed from the received VSS pulses and then passes this information on to the Instrument cluster. If the received pulses are conditioned by say the ABS module first, then transmitted via CAN to the PCM module and the Instrument cluster it will be relevant because the interpretation of this speed signal will be different.
Try hitting 230 with your std wheels back on. It’s a simple way to confirm this.
Anyone got wiring diagrams for this model yet?

Pete.
 
#12 ·
All BA models fitted with ABS use the ABS Vehicle speed sensors for speedo operation.The signal is recieved by the PCM then transmitted along the CAN network to the modules that need it(ICC for volume control as vehicle speed increases,BEM for speed sensitive wiper operation,TCM for traction control operation,ICM for speedo)The only BA's that have the transducer in the extension housing of the transmission are all non ABS.My sugestion is to have your car checked on a dyno(Most dyno's are capable of this without stressing the car too much and it's legal and a lot safer)Then go to your dealer and tell them how far out it is(if it is).They can then reset the speedo offset to compensate for the difference with thier dignostic equipment.But be advised,if you have been driving on the speed limiter they will know,because your vehicle logs a diagnostic code P1270.
 
#13 ·
cant the logs be errased if i disconect the battery?! Doesnt really bother me though... changing the ECU anyway.... a motec will piggy back it....
 
G
#16 ·
FordTech65 said:
All BA models fitted with ABS use the ABS Vehicle speed sensors for speedo operation.The signal is recieved by the PCM then transmitted along the CAN network to the modules that need it(ICC for volume control as vehicle speed increases,BEM for speed sensitive wiper operation,TCM for traction control operation,ICM for speedo)The only BA's that have the transducer in the extension housing of the transmission are all non ABS.My sugestion is to have your car checked on a dyno(Most dyno's are capable of this without stressing the car too much and it's legal and a lot safer)Then go to your dealer and tell them how far out it is(if it is).They can then reset the speedo offset to compensate for the difference with thier dignostic equipment.But be advised,if you have been driving on the speed limiter they will know,because your vehicle logs a diagnostic code P1270.
FordTech,
Does the PCM just filter the speed signal before sending it out on the CAN or is it converted to an actual speed before being sent on the CAN? It sounds like the former.

Cheers,
Pete.
 
#17 ·
The PCM recieves the signal from either the wheel speed sensors or transducer as a square wave frequency signal and transmits it along the CAN as the same type of signal to the other modules.
 
#19 ·
FordTech65 said:
The PCM recieves the signal from either the wheel speed sensors or transducer as a square wave frequency signal and transmits it along the CAN as the same type of signal to the other modules.
Isn't the CAN a digital bus? Wouldn't it be sent as like a binary word? I don't doubt ur right, just want to know how the CAN differs from the old school wires?
 
#20 ·
Kypez, If a Ford delearship said they wont do it, say your taking your business to another ford delearship. Its bulls*#t they cant, they obviously dont want 5 mins of not making a buck. If they have a WDS, they can, and should do it, its piss easy for someone there who knows what their doing.
Listen to Fordtech65's information, its all exactly correct and usefull.
I wasn't aware transducers werent used in ABS models.

*To save your self the dyno money though, just go to the dealer for them to recalibrate it in the PCM, if your cars got different sized wheels, this should be all you need to do.*

Your PCM may even need a software update when they do this.
The PCM wouldnt have a fault. You also wont be able to change the PCM, you need this for your car to function, can add a chip onto it but thats it.
 
#21 ·
yeah... found out that even if I did piggy back a motec, it would only run engine management... cant make it do any other thing... stock ecu has to run speedo, etc...

I think Brad Garlic are messing around with me... They lied to me about the GT (my XR8 came up to be $200 cheaper than the base GT and I asked them repeatedly that I wont get an XR8 if the difference between the 2 was less than $3000)... They broke my drivers seat adjuster and havent bothered getting the part for me... they say, "oops, we ordered the wrong part!"... and that was 5 weeks ago!

Will check out some other dealers and see what happens... Thanks for the tips guys... i really appreciate it...

Kieran.
 
#22 ·
Cancerman said:
Isn't the CAN a digital bus? Wouldn't it be sent as like a binary word? I don't doubt ur right, just want to know how the CAN differs from the old school wires?
I stand corrected.The PCM recieves a square wave signal(Digital) and re transmit's it to the CAN controller in the PCM which converts it to a binary signal or "frame"(I think thats right,but dont quote me) and then transmits it along the CAN Bus.
 
G
#24 ·
Sounds like the speed signal comes from the VSS if it's a square wave? The ABS encoders are indeed Variable reluctance sensors. The waveform from these is not quite a sine wave but certainly not a square wave like the hall effect VSS.
Have you got any wiring diagrams Ford tech?

Pete.
 
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