Question about the SRM

theDreamer · 05-31-2013, 01:23 PM

Quote:

Originally Posted by IDZRVIT

This can turn out to be a good discussion on how SRM works. Yes, I can see where the computer could be programmed to add fuel (increase in engine speed) if left in neutral for a small period of time during the upshift process or anticipating such but is that true? I know the purpose of SRM is to eliminate heel-toe for downshifts but you don't heel-toe for upshifts. There is no reason to. If I'm already at say 3500 rpm and for ready to upshift and the computer detects this as I move the shifter into the next higher gear, why would it want to increase the rpm? If the revs drop several hundred rpm (foot off gas, clutch in.....) and the shift is completed at say 3100 rpm without SRM, why would the computer want to increase the revs to say 3900 rpm if I wasn't planning on accellerating any more because I've reached my cruising speed? To me, that would cause a slight unwanted surge in speed. If that is what this discussion is about and I have explained this scenario correctly for SRM interaction in an upshift, then this would be a safety issue, no?

Yes, it is true that the system will increase RPM on a shift up. I am trying to locate a few articles but it was discussed with Nissan and they said the Revmatch works on both up & down shifts to help 'smooth out' shifts.
Now the questions we would have to look at is how it determines this smoothness factor and what issues it could cause on an upshift.
I would presume the upshift rev is more of a safety net for the transmission. Meaning that it keeps the parameters inline with what it wants to be around so if you are off by 100 it will do a slight bump to bring it up for you but this could cause the driver to have some jutter if not prepared or ready.

This would be a fantastic test on a bone stock car.
Do some slow 1-2 shifts and 3-4 and record the RPM gauge and OBD2 readings/logs and then some faster higher RPM shifts and do some data comparisons. The shift speed factor can come into play and can be controlled a bit but will just need a driver who is steady.

Quote:

Originally Posted by SS_Firehawk

Dreamer, you are my hero, I thought the same thing... but you were sooooo much nicer about it than what was in my mind

I seem to be the nice guy on the forum.

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