Strange pArk to idle condition...

[ski_dwn_it]

ok guys...

Whats up. Car has a pretty big cam in it 715 lift ~270 on the duration. At idle in park or in drive it idles fine. Had the idle at about 1100 anything below that shakes the car pretty bad, there its fairly smooth. Well smooth at a big cammed car idles.

Now the problem is when I go from park to drive or reverse. The MAP values drop WAY down from high 60s into the high 80s and low 90s (lower left corner).

It "appears" that its going lean, but I have dumped a TON of fuel at this thing and it just gets worse....went the other direction with no salvation either.

It feels like the converter is too tight, one of those deals. But the converter is a race 8" converter with a 5k stall speed.

The car does it EVERY time I do it, regardless of closed loop or forced open. Spark has been set to high, lower and even played with the idle spark to try to save it that way.

Is it added AE from the TAU table with the large jump in MAP?

If I tap the gas or every so slightly give it a VERY VERY small amount of throttle, it drops in and will idle for hours without a problem.

All VE tables are right around 0 correction for idle. Tough to see what is happening at the time of dropping it in gear, since the car shuts off almost immediately if I do not intervein with some throttle, then it stays running.

Some questions;

(1) What do you want your IAC to be at in idle park? And drive? I know with the stock ECMs if you got the IAC too many counts it could cause some of these problems. Not sure on these setups....any advice.

(2) closed loop MAP setting in configure controls screen? Seems this does not work real well to activate and disable like the RPMS setting does.

I also played with the proportional and intergral gains since the manual says the intergral is what is is used for pulling the car into gear. It doesn't like it high, doesn't like it low nor in the middle. Same result.

Norbs, craig....any thoughts. Starting to think its just because of the little vacuum I have.

Target idle A/F is 13.6-14.0....exhaust is clear and clean smelling.

Thanks anyone that can offer some help.

 

[tuner]

To deal with that same problem with a 500” BBC with a Gen7 the cure was to open the throttle for the neutral idle speed desired until the IAC was completely closed, so it could only add air, not reduce it.
With a cam with that much overlap a richer mixture (12.5-13/1) might help.

(Good choice, by the way, sounds like you’re serious about making power.)

 

[aDFIguy]

Sounds like IAC. Your counts should be around 5-6% @ warm idle.

If that doesn't do it, the ECM has a secondary idle control strategy that can be tied to the Self-Test input (STI). You can wire that input to a park/neutral type of switch that can be activated on the gear shift to compensate for the load change. Program the same idle speed with a bump in IAC counts to make the shift smoother.

 

[ski_dwn_it]

Sounds like IAC. Your counts should be around 5-6% @ warm idle.

If that doesn't do it, the ECM has a secondary idle control strategy that can be tied to the Self-Test input (STI). You can wire that input to a park/neutral type of switch that can be activated on the gear shift to compensate for the load change. Program the same idle speed with a bump in IAC counts to make the shift smoother.

GUys thanks for the comments. Played around quite a bit last night with it and got it a little better. Still would like to have it where I did not feel the need to put my foot into the gas on shifts. Its livable now and actually I am in the habit of doing it now.

You mentioned 5-6% warm idle, is that in or out of gear?

I agree that the IAC should be only controlling a very small percent of the idle air flow, that is the way I have always done stock ECMs.

Is it possible that the AE is getting added in during the drop in MAP?

I hate to mask the idle problem with more fuel, since I can now run the car and not smell to high heaven of fumes.

In the power department it has TONS - fun car to drive around - best of both worlds. Got great handling ability and in the straight-aways peels the skin back on your face.

 

[aDFIguy]

5 - 6% out of gear.

To check if AE is the problem, do the following:

With the engine running, open up CalMap and connect to the ECM.

Press the F12 key to view the Acceleration Threshold table.

Watch the screen as you drop it into gear. You will be getting Acceleration Enrichment if the Asynch Fuel Request value goes higher than the table setting for Acceleration Threshold %.

You probably can't correct your problem by changing this particular table, but it will tell you if you are getting additional fuel or not.

 

[ski_dwn_it]

Thanks for the tip.

 

[tuner]

In the 500” BBC experience I referred to above, a major improvement in everything about idle quality and transients in driving was when the TAU table got crowded toward the top. By that I mean the lowest row (87.5%) is no lower than 75. I don’t know if this is the right logic, but there is no 100% row and the MAP goes to 100%. Since the amount of enrichment or clamping depends on the ratio (spread) between adjacent cells to me that implies there is another enrichment from 87.5% to 100%. With the valve timing I was dealing with (not quite as radical as yours) the vacuum would wander around and drop when it went into gear and (I guess) the TAU bumped the fuel delivery around with it. In this application, it seemed like it didn’t want much transient meddling with changes in vacuum in the 25% to 75% area, but it was hungry as it got close to 100% MAP.

This was my first experience with a Gen7 so I don’t know if it's right, but it has 600HP and gets 22 MPG in a `65 Impala. Runs great. An Innovate LC-1 was the key to happiness. At first, I would have rather used a MoTeC. They have 4 functions to control the transients where Accel rolls them into one. My inexperience with the system caused my initial frustration but I’m happy now. The TAU is a major sensitive area, or it was in my case.

 

[norbs]

Well, running 14.0 with a 270~ duration cam is simply amazing first off. You should set the ve map to maintain about 13.7 ish in gear with no correction, and have some negative correction when in park. Also you could try a higher iac attack rate, which is a lower number actually. and see if it helps any. Please update us.

 

[ski_dwn_it]

Well, running 14.0 with a 270~ duration cam is simply amazing first off. You should set the ve map to maintain about 13.7 ish in gear with no correction, and have some negative correction when in park. Also you could try a higher iac attack rate, which is aower number actually. and see if it helps any. Please update us.

Actually in Australia at the present moment on business/pleasure trip to GM Holdens.

Helping them out with some problems they are experiencing, so I will have to wait till next weekend to try anything with the car. Before I left I had made some progress with the car....but it was still dying when you drop it in gear....weird because the slightest amount of gas peddle you don't even notice that you put it in gear.....this leads me to believe the car wants more AIr that time of gear shift - maybe to offset the fuel that is being added.

I am going to watch that AE table and see if anything is being added upon the shift, which is what it seems like its doing. The MAP drops quite a bit, with each shift....

But that is all speculation until I can get that table up and watch the values at the time of shift.

Well, back to starting another day (really night for my body) here in Australia.....going to take a trip to the coastline today per the recommondation of a few Australian girls- that said it was a beautiful drive along the southern coastline.

Will report back to you guys when I return. thanks for the suggestions.

Regards,