Another Rich Decel Thread..Need Help

[WeathermanShawn]

Here is a couple of quick snapshots of a log run I did this morning.

One is with the 2002 Camaro M6 B4309 'zeroed' out. The second log I simply re-loaded the stock 2002 Camaro B4309 Table.

The first decel shows External Wideband readings well below 14.63 AFR. The second shows stoich was hit on decel very rapidly, compared to the first. A few disclaimers. The Pids I selected were primarily for another tune/log goal. Willing and able to log identical IAC DMA pids and do one run down a hill with no TC, another with.

Perhaps the IAC function is simply allowing the RPM/MAP to fall slow enough to allow for adequate STFT switching?

Anybody else had a similar experience?

[5.7ute]

WeathermanShawn, all you have done is add air via the IAC valve to bring your AFR into line. This has not addressed the issue just masked it.

[jetblast]

with a h/c mod, seems to me that your condition would be expected especially, if while in decel., you have altered the ve tables in that particular region. if you are not getting any poping noises while on decel perhaps all you need is a slight adjustment in the mininum pulse tables. remeber that injector pulse width is now greater than stock at any given egine running state, so the injector should be comanded to closed a bit quicker and/or to a shorter time for decel, hence minimum pulse width tables.

[WeathermanShawn]

WeathermanShawn, all you have done is add air via the IAC valve to bring your AFR into line. This has not addressed the issue just masked it.

Whats wrong with that? Isn't that what we are doing with RAFIG with idle?

I think I understand your point though, but why would my minimum IPW be to rich for a stock injector?

Not saying I have discovered anything new..but isn't the idea of adding air an acceptable tuning method to address problem fueling areas?

[5.7ute]

Whats wrong with that?

Isn't that what we are doing with RAFIG with idle?

I think I understand your point though, but why would my minimum IPW be to rich for a stock injector?

Not saying I have discovered anything new..but isn't the idea of adding air an acceptable tuning method to address problem fueling areas?

Appreciate the replies(s),..just wanting to learn to do it right.

Thanks.

..WeathermanShawn..

If you are running rich under decel it is obviously caused by too much fuel for the conditions. Adding air will make the AFR read right but as you have found it will prevent the engine from decellerating properly, may as well hold your foot slightly on the gas.
The problem you are seeing is the inability of the injector to inject a small enough fuelmass. Whether this is in the tune or a characteristic of the injector is what you will need to find out. You will need to back calculate the actual commanded IPW to see this.(Not IBPW as this includes small pulse, offset modifiers etc.)
FWIW camming an engine will also lower the VE in the lower RPM/MAP areas adding to these problems.

[redhardsupra]

(Not IBPW as this includes small pulse, offset modifiers etc.)

where did you get this info? i've been looking for it for ages!

[WeathermanShawn]

5.7, thanks for the explanation.

The more I think about it, what you said makes a lot of sense. You are correct in that I would not be happy with that type of deceleration.

I will try that out.

[5.7ute]

where did you get this info? i've been looking for it for ages!

I worked it out when trying to make a pid for transient fuelling. I had noticed a discrepency when back calculating IPW from airmass. After further investigation by using a lookup() pid for the voltage Offset tables I could get values to correspond as long as the calculated IPW was above {B4006} small pulse threshold.
I then made a calc pid using the IFF() function & lookup() using {B4005} values which then had the rest of the values come into line.
This also confirmed my theory that the {B4005} small pulse adjust should not be linked to GM.IBPW but my new CALC.IPW pid.
thoughts?

[joecar]

Mick, can you post that calc pid... thanks.

[5.7ute]

No problems Joe. It takes a succession of pids that are all tune related.(They need specific info from your tune file to work)
CALC.IPW
*CLC-00-015
ms 0.00 30 0.3 "({GM.DYNCYLAIR_DMA}/{GM.AFR}/{GM.INJFLOW})*1000"

This one works for you lucky people that can use GM.INJFLOW to give CALC.IPW
CALC.IPW
*CLC-00-018
ms 0.00 20 0.3 "({GM.DYNCYLAIR_DMA}/{GM.AFR}/lookup({GM.MANVAC}, 0,8.7266, 5,8.7813, 10,8.8359, 15,8.8906, 20,8.9453, 25,9.0, 30,9.0547, 35,9.1016, 40,9.1563, 45,9.2109, 50,9.2578, 55,9.3125, 60,9.3594, 65,9.4141, 70,9.4609, 75,9.5156, 80,9.5625))*1000"

This is for us poor buggers that need to input our IFR into the equation to get it working. Again this would give CALC.IPW. You can obviously use only one or the other. The colored numbers are the ones that need to reflect your tune file.

CALC.COM_IPW

*CLC-00-019
ms 0.00 20 0.3 "iff({CALC.IPW}>0.699085,{CALC.IPW}+lookup({CALC.IPW}, 0.426,0.167173, 0.4860,0.136778, 0.547,0.121580, 0.608,0.106383, 0.669,0.091185, 0.729,0.075988, 0.790,0.060790, 0.851,0.045593, 0.912,0.030395, 0.973,0.030395, 1.033,0.045593, 1.337,0.045593, 1.398,0.030395, 1.581,0.030395, 1.641,0.045593, 1.945,0.045593, 2.006,0.030395, 2.553,0.030395, 2.614,0.015198, 4.012,0.015198),0.881456)"

In red is the value from {B4003} minimum injector pulse width. Blue is the values from {B4005} small pulse adjust. Yellow is the value in {B4004} default minimum pulse width
CALC.OFFSET
*CLC-00-016
ms 0.00 20 0.3 "{GM.IBPW1}-{CALC.COM_IPW}"

This pid will work out what is left of the GM.IPW that can be attributed to either transient fuel or the voltage offset table. I then made another pid using the "average" values of the voltage offset table as it is too large to fit in a custom pid. I only used between 13&15 volts as this is where you should be operating 99% of the time.
CALC.TRANSIENT_FUEL
*CLC-00-017
ms -10 10 0.3 "{CALC.OFFSET}-lookup({GM.VOLTS}, 13,0.3647, 13.5,0.3343, 14,0.3191, 14.5,0.3040, 15,0.2736)"


I need to clean all this up but you get the idea.