I was out giving the EB a bit of a hard time today, and noticed (first time I've ever noticed it) that the tacho dropped straight back to 0 for a fraction of a second. The actual RPM was way up in the red, It has a fuel cut / rpm limit at 5750, but i think the ecu took too long to respond and it reached a second stage of rpm limit (ignition cut?)
I actually heard a tick noise as it swung all the way back (obviously hit some sort of stopper in there somewhere), and then I knocked it into 2nd and it went straight back up to around 3700
Has anyone seen this before, this is on an EL fairmont ECU
Would I be right in sugesting that the ecu has a soft limit (fuel cut) at 5750? and a hard limit of 6000 (ignition cut)
Nothing to worry about... sounds like you hit the magical overload cut off point on the actual guage. I'm pretty surprised you actually got that guage that high... good job
You get the same type of guage overload protection if you have corroded terminals on the fuel sender and you fill her up with petrol... she goes all the way up, past the Full mark and then clicks and goes plummeting to empty until you use some of the petrol up.
If it worrys you too much, fit an aftermarket monster tacho... it should be good for about 8000RPM
The tach dropped to 0 for a bit, soon as i dropped into 2nd it went back up, so i'd say its a hard rev limit in the ecu that cuts spark. As the soft limit will only cut fuel at around 5750. There is no aftermartket engine control in the car.
I might advance the cam a slight bit later on at some stage, as it hits 5500 quite easily, so advancing the cam should bring the power down in the range, and taper off slightly earlier.
....I'll have to try get it up that high again, to see if the same thing happens - but its the 1st time i've ever seen that happen in an e-series -- weird...
By the way, if i can scrounge up an extra 50 this week, i might stick it on a dyno just to see what it pulls.
If your running the standard tacho guage in the dash, I seriously think you will that it's the guage thats the problem and the ECU isn't cutting off the spark at all. As i said.. if any of your guages go over their limit they will turn themselves off so they don't become damaged, hence the "clicking" noise you heard.
If you hooked up a aftermarket tacho then you will probably find she's still got ignition and is up around 6000RPM.
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