Data log do we think this is transmission slip (Auto)

[scoobydo123]

Hi, not sure if best section of maybe electronics any way onto the question. I have a people carrier that I have datalogged and it looks like the transmission slipped? Trans was locked in 3rd via a inhibitor switch for mapping but OD was on. Now not sure if that would disable full lockup as it is a bit of a fudge.

So below is my data log of a pull that went a bit haywire I think. Pull started at 29mph(40.095) at 47.358 rpm stopped climbing @ 4660rpm at dropped to 4560rpm 48.279 (was this perhaps the lock up on the torque converter engaging)? Then rpm rapidly increased to 6806rpm (current rev limit)
between rev 4580rpm @ 48.393 to 6806rpm 49:917 72mph to 79mph. My vehicle speed sensor is from the tail shaft of the transmission.

Anyone got any ideas? Happy to share the datalog with anyone. It is AEM v2 ecu software is a free download.

I think there is some slip going on as the transmission is only medium duty.

Have plotted a trimmed data log in virtual dyno and that requires loads of smoothing (5 points) when the engine starts making power.


Thanks

[Olas]

what is the gear ratio and diff ratio and tyre circumference? we need to know these to calculate the road sped and see if it matches with the report.

looking at the shape of the curve there does seem to be *some* slippage - engine speed rises faster than road speed.

have you done the maths yet? what does it tell you?

[scoobydo123]

Hi, to confirm that the VSS is logged via the aem2 that has been calibrated against GPS. The graph is plotted via AEM data. Can export any channels as csv or supply the log. Do you think it looks like slip before the obvious slip of some description. Conditions on the day were slightly damp but if it was wheel spin wouldn't we see the road speed drop when it hooked up and the speed increase quicker? Seems odd that the rpm dropped mid pull can only guess that was either the lock up engaging and trying to give me full transfer. Transmission is re4r01a.

Was in 3rd but OD on should have been 1.0 but as OD was on it will be slightly different. Final drive 4.64:1 iirc.

Tks

Edited by scoobydo123 on Tuesday 3rd March 11:10

[eliot]

cant see what car/box this is - but some lockup clutches aren't that strong and are more for reducing revs in the cruise rather than WOT.

[scoobydo123]

Nissan largo people carrier. Not strongest trans in the world re4r01a not the HD version. So same as in the 300zx NA. Do you think from what is in the log that it was the TC slip as it attempted full lockup. May be partially caused by my fudge to lock it in 3rd. Suppose do another run and have a lamp on the lockup solenoid? The fudge is a switch that goes to a mechanical selector maybe this confused the logic of the tcu perhaps in real world driving it would not be an issue.

Edited by scoobydo123 on Tuesday 3rd March 13:28

[scoobydo123]

Ok would you say it is strange how the rpm and tailshaft speed don't track each other and overlap @ crica 3000rpm? Trying to get it straight in my head what is happening.

[GreenV8S]

The Y axes don't seem to use the same origin so it's hard to tell what the relationship is between the different inputs, but the step changes in 'vehicle speed' surely can't be right.

[scoobydo123]

Hi y axis is coloured to the same as the trace and legend. Obviously only have 3 on there which are rpm, load and mph via the vss on the tail on the trans. Can upload a Google link to the log. Tks

[scoobydo123]

@GreenV8S apologies you was correct the scaling was not correct on the y axis. Have provided a new screenshot below.

Not sure if for some reason the converter tried to lock on hence the 100rpm drop.

[LimSlip]

GreenV8S said:

The Y axes don't seem to use the same origin so it's hard to tell what the relationship is between the different inputs, but the step changes in 'vehicle speed' surely can't be right.

It just means the sample rate for road speed is much lower than for RPM.

[scoobydo123]

@LimSlip the first picture the Y axis was not referencing a useful scale. VSS data logging was set to "low" speed the actual resolution of the VSS on the tail of the automatic transmission is not that great but maybe worth me upping that channel to see if that smartens it up.