VDHx is pissing me off - hidden pulsewidth multiplier

Pocket · #1 (**permalink**) 04-23-2011, 02:21 PM

Somewhere in the VDHx calibration there is a hidden pulsewidth multiplier that I cannot find. When my engine is fully warm (was playing around yesterday with EOT's at 190 degrees), something is adding nearly a full ms of pulsewidth at WOT. I've been kinda tuning around it for a while, but I'm getting new injectors (bigger injectors) soon, and I'm tired of my pulsewidth not being exactly what I'm asking it to do.

For example, playing around yesterday I'm in a tune that calls for a max 3.3 ms of pulsewidth. Instead, I was getting 4.2 ms of pulsewidth, and it hit that the instant I went from a throttle position holding 3ms of pulsewidth at 2800 psi ICP with duty cycle well under 40%, to full throttle. Of course, holding 4.2 ms I watched my ICP plummet and duty cycle go sky high. The thing is, pulsewidth went sky high first, THEN the ICP started to drop. So something is tell my injectors to stay open much longer than I'm wanting them to, rather than my tuning adding pulsewidth because ICP is falling.

Problem is, I have the EXACT same values on PMT1 pulsewidth multipliers and adder maps and functions (all the pulsewidth multiplier and adder tables that I know of are exactly identical), yet whatever I set for pulsewidth in the PMT1 tune, that's exactly what I get. No if's, and's, or but's.

So there's some undefined table in my VDHx definitions that's multiplying my fuel injection pulsewidth, and I don't know where it is.

Any ideas?

***907DAVE*** · #2 (**permalink**) 04-23-2011, 03:00 PM

Could it be the Multiplier to Pulsewidth Adder in the functions menu?

This should not make a difference after 72*....... but I am not sure what temp this is based on.

Compare this to the PMT1 and there is a pretty significant difference.

Pocket · #3 (**permalink**) 04-23-2011, 03:11 PM

Quote:

Originally Posted by 907DAVE

Could it be the Multiplier to Pulsewidth Adder in the functions menu?

This should not make a difference after 72*....... but I am not sure what temp this is based on.

Compare this to the PMT1 and there is a pretty significant difference.

Yeah I saw that table too, but after 17* C, there's no difference between VDH5 and PMT1. So I'm not sure how that would make any change. Could change it for gits and shiggles.

Shaw · #4 (**permalink**) 04-25-2011, 10:00 AM

Ive been fighting the same thing with PMT1. With all adders and multipliers zeroed out I still get a little over 1ms of PW at full throttle. Ive tried everything I can think of to no avail.

***cleatus12r*** · #5 (**permalink**) 04-25-2011, 10:56 AM

It's not a problem with any hidden multipliers. It's a definition divisor error in the base pulse width map that will be fixed with the new definitions when they are available (obviously, current MDFs that you have would be replaced at no charge).

Pocket · #6 (**permalink**) 04-25-2011, 11:41 AM

So Cody, is this currently available for the VDHx definitions?

A few months ago Bill sent me an updated PMT1 definition, and I don't have the same issue as I do with the VDH5. Also the scaling is different on the PMT1 than it is with my current VDHx definitions. I much prefer the PMT1 style.

Shaw · #7 (**permalink**) 04-25-2011, 12:13 PM

Quote:

Originally Posted by Pocket

So Cody, is this currently available for the VDHx definitions?

A few months ago Bill sent me an updated PMT1 definition, and I don't have the same issue as I do with the VDH5. Also the scaling is different on the PMT1 than it is with my current VDHx definitions. I much prefer the PMT1 style.

Hmm, wonder how I would go about getting the updated PMT1 definition?