Hey all, got a problem that I think is the car thinking it is not moving and thus enabling the anti-lag once it gets a change to get warm. If you haven't driven the car overnight it revs cleanly, but once warm the problem is back for the day. The problem also manifests if the car is sitting in the sun for a few hours, even if the engine is dead cold. Today I put a stock ECU in and the problem instantly disapeared. Then I used a totally different ECU to mine with anti-lag enabled and the problem was back. The speedo works fine during all of this. Are there any speed sensors that talk to the ECU that don't effect the actual speedo reading. I don't have any idea how the speed data gets to the ECU. Does the cable drive the speedo and there is a sensor off the back of the speedo that feeds the ECU? That could explain it.
Anti-lag all the time when warm
- Thread starter LumpyVR4
- Start date
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BMGTZ
Grumpy old man from the school of hard knocks
cable drives speedo...speed sensor is in the speedo.
on a gsr there is screw that a lot of people remove as it is the speed cut for 180. If that is out it can affect the speed signal
on a gsr there is screw that a lot of people remove as it is the speed cut for 180. If that is out it can affect the speed signal
Marc
Pre Staged
Sounds very odd that the varient here is heat, the speedo should be sending a signal wether it be ice cold or scortching hot, only thing i can think of would be a shitty join with solder between the ECU and the speedo, but given it's a VR4 i doubt that would have been cut/modified, unless like BMGTZ said the cluster has been toyed with to remove a speed cut.
I had this issue except i had the launch control on 100% of the time cold, hot or indifferent, spliced in some wire from the speedo to ecu (traps for young players) and BOOM, the problem solved.
I had this issue except i had the launch control on 100% of the time cold, hot or indifferent, spliced in some wire from the speedo to ecu (traps for young players) and BOOM, the problem solved.
I had the speedo apart yesterday. There is just a simple reed switch in there that detects the speedo not being on zero. I have a spare J spec dash too and there is a extra contact attached to enable the speed limiter. All you'd have to do to disable it and still have launch control is remove the extra contact. I'll pop up some pics when I get a chance.
I'm waiting on a logging cable to turn up. Then I'm going to check wether I have a speed signal when the car is OK that disapears when it plays up and go from there.
I'm waiting on a logging cable to turn up. Then I'm going to check wether I have a speed signal when the car is OK that disapears when it plays up and go from there.
So, I was too impatient for the logging cable to turn up, took a look at the circuit and figured it out.
There is a set of rotating magnets on the back of the speedo that open and close a reed switch. When the switch is open there is 5 volts from the ECU and when closed it's grounded. That 5 volts is on the base of a transistor in the ECU. As the magnets rotate, openning and closing the reed switch, the transistor base voltage goes up and down. This produces a frequency on its output that the ECU uses to figure out how fast the car is going.
The actual cause of my problem was one of the dash connectors, that get nice and toasty in the sun under the dash pad, had a few contacts that are getting physically weak with age. Once they are warm they are even more flexible and lose good contact. The earth for the speed sensor was on this. No earth means no voltage change on the transistor so the car thinks it's stationary.
Next on the list, new belts because I have no idea about the age of these ones, and some cam gears to get my 272's dialed in properly.
There is a set of rotating magnets on the back of the speedo that open and close a reed switch. When the switch is open there is 5 volts from the ECU and when closed it's grounded. That 5 volts is on the base of a transistor in the ECU. As the magnets rotate, openning and closing the reed switch, the transistor base voltage goes up and down. This produces a frequency on its output that the ECU uses to figure out how fast the car is going.
The actual cause of my problem was one of the dash connectors, that get nice and toasty in the sun under the dash pad, had a few contacts that are getting physically weak with age. Once they are warm they are even more flexible and lose good contact. The earth for the speed sensor was on this. No earth means no voltage change on the transistor so the car thinks it's stationary.
Next on the list, new belts because I have no idea about the age of these ones, and some cam gears to get my 272's dialed in properly.
croket
Well-Known Member
was some nice cam gears forsale in parts the other day , fidanza ones i think . Im yet to dial my cams in yet even tho i have the gears to do it
