Maximum Desired Idle Area?

[ArKay99]

Can someone explain this ID? {B4350} Maximum Desired Idle Area. Description: "This calibration limits the desired idle effective area."
Has anyone altered this and discovered it's impact and what it's use would be?

[TAQuickness]

Can't say that I have. I re-did my idle keeping all the IACEA tables/values stock. IIRC, the only time I've seen this value vary is from car to truck.

As far as it's purpose, best I can tell it's an upper range limit on the IAC. This all goes back to PID control stuff.

[ArKay99]

Ok, then. I won't touch. I was just wondering if it would help any on a LSX90/90 car.

[TAQuickness]

what's your idle doing?

Edit: is this along the lines of the un-even trims at idle?

[Bruce Melton]

FWIW, I ran a Fast 90/LS2 setup with LS6/Shaner settings and really noticed no difference in idle characteristics. Stock B4350 in both cases.

[caver]

I did play with it once on a heavily cammed car to get it to idle when cold.
Had to raise it a fair whack.

[ArKay99]

what's your idle doing?

Edit: is this along the lines of the un-even trims at idle?
No, the trims are fine now, since I swapped the rockers.
Idle is great. 800 rpm's with a nice little lope and no misfires. It's my transitions. The motor drops to around 500 rpm's when I blip the throttle when standing still in P/N. Also when rolling the idle will drop to 500 rpm's then surge to 1500, then drop to 400, then surge to 1600, then drop to 300, etc. If I let it go long enough it will stall. I'm going after the Throttle Follower and Throttle Cracker when I get home from work today and see If I can get those to help. I was wondering since I had more blade area if a trim on the B4350 would help. I'm for leaving it as you sayand going after it with the other tables.

[ArKay99]

FWIW, I ran a Fast 90/LS2 setup with LS6/Shaner settings and really noticed no difference in idle characteristics. Stock B4350 in both cases.
I've always had this issue after the h/c swap, though it's a little worse now using an LSX90 and NW90. I haven't touched my throttle follower and cracker yet. I'm going to lengthen the delays and play with the air. If I can find a trend then I'm thinking I can get it from there. I have done the idle transition as outlined in the sticky and the RAF and MAF are within .10 at all ECT's, my transistions need work though.

[Bruce Melton]

Fast 90 intakes are famous for leaking and of course the MAP sensor mashing issue. Could that be your problem or part of it?

[ArKay99]

Fast 90 intakes are famous for leaking and of course the MAP sensor mashing issue. Could that be your problem or part of it?
I thought that might have been part of my original problem, I had uneven LTFT's at idle. It turned out to be rockers rubbing on the retainers. I had done this to my manifold to try and seal it better, if indeed it was leaking. http://www.ls1tech.com/forums/showthread.php?t=457355&highlight=FAST+manifold+le ak (http://www.ls1tech.com/forums/showthread.php?t=457355&highlight=FAST+manifold+leak) I also have the MAP sensor sealed with RTV (sensor safe Permatex). It actually was a little frayed around the sealing ribs.
Anything is possible at this point. I'm going to try and tune it out. If I can't do it easily, The manifold is coming off and I'm going to re-seal it, or send it back to FAST and have them do it.

[TAQuickness]

sounds like you are on the right track. I had to increace the decay time on mostly the follower, and some cracker to get my transistions. At the moment, it hangs about 200 rpm over desired idle before making the full transition. I can live with it for now.

[SSpdDmon]

No, the trims are fine now, since I swapped the rockers.
Idle is great. 800 rpm's with a nice little lope and no misfires. It's my transitions. The motor drops to around 500 rpm's when I blip the throttle when standing still in P/N. Also when rolling the idle will drop to 500 rpm's then surge to 1500, then drop to 400, then surge to 1600, then drop to 300, etc. If I let it go long enough it will stall.

Did you try changing the "Filtered RPM Airflow Correction" table (B4512 in my OS)? I would think the first half of your problem lies between this table and the Throttle Follower. The second part of your problem sounds like it has to do with the idle correctors (both spark and airflow). That points you towards the Direct Airflow Correction table (B4515) and the Idle Overspeed/Underspeed Error tables (B5935/B5936).

My only question for the software gurus would be, how does the pcm calculate the rate of change for the rpms in the B4512 table?

[ArKay99]

Not sure if this is the problem, a contributor, or has nothing to do with it but, I just discovered my head gaskets are seeping. Now I have to pull the heads and go from there.:bash:

[Bruce Melton]

Not sure if this is the problem, a contributor, or has nothing to do with it but, I just discovered my head gaskets are seeping. Now I have to pull the heads and go from there.:bash:

Strange- internally or externally?
I read the gaskets are slighly different causing slight external oil seep?

[ArKay99]

Strange- internally or externally?
I read the gaskets are slighly different causing slight external oil seep?
Slight external oil seep I can deal with. However, I was riding around doing a little logging and smelled coolant. When I got in the garage I checked it out the best I could with a hot engine but saw nothing. Later on I was adjusting my driver's side exhaust and had my face close to the exhaust pipe and smelled w slight scent of coolant wafting from it. The passenger's side did not have the odor. I checked the gasket at the bottom of the head and it was wet with what looked like water, not oil, but I couldn't pick up a scent from it, it wasn't enough. I removed my plugs and they were clean and on the white-gray side. They weren't tan, but I removed the #2 plug and it was the same. What does DexCool residue look like on a spark plug? I'm getting no visible smoke out of the exhaust, just a slight coolant smell. I don't want to run it until I get this resolved. I don't want to compromise my bearings if coolant is getting in the crankcase.

[Bruce Melton]

Slight external oil seep I can deal with. However, I was riding around doing a little logging and smelled coolant. When I got in the garage I checked it out the best I could with a hot engine but saw nothing. Later on I was adjusting my driver's side exhaust and had my face close to the exhaust pipe and smelled w slight scent of coolant wafting from it. The passenger's side did not have the odor. I checked the gasket at the bottom of the head and it was wet with what looked like water, not oil, but I couldn't pick up a scent from it, it wasn't enough. I removed my plugs and they were clean and on the white-gray side. They weren't tan, but I removed the #2 plug and it was the same. What does DexCool residue look like on a spark plug? I'm getting no visible smoke out of the exhaust, just a slight coolant smell. I don't want to run it until I get this resolved. I don't want to compromise my bearings if coolant is getting in the crankcase.

Yuck! You should be able to pressure test that? Shouldn't it show on dip stick if there is water in pan?

[ArKay99]

Yuck! You should be able to pressure test that? Shouldn't it show on dip stick if there is water in pan?
Yes, if there is enough. I checked the dipstick and the oil looked clear and honey colored, not emulsified caramel. I've only got about 200 miles on it, so it is still very clean. However, when I change the gaskets, I'm sending the oil for analysis. I believe this to be a seepage problem, not a cracked or blown head gasket. That's why I believe the coolant is getting into the combustion chamber, and it's only a tiny bit. Oh, also when you start the car and let it warm up it doesn't smell. Only when you put a load on it and run up the revs a bit.
Also, I checked the water pump gasket area at the front of the motor the best I could and didn't find any there. The thought behind that was a leak at the bottom of the water pump/block junction could wick around the side of the block and travel along the small feathered edge of the head gasket. I am going to pull the alternator and PS pump off before I yank the heads to be absolutely sure, but the sticker is the coolant odor in the exhaust. The interesting thing is it smells like raw coolant not burned coolant, not that I would know what burned coolant smells like...

[joecar]

Did you check for bubbles in the coolant by looking down the radiator fill neck...?

Also, as Bruce mentioned, do a pressure test (pump fits over radiator neck with seal, pump up 20 psi with engine/coolant hot, see if pressure holds for several minutes, look for bubbles in radiator).

Also when cold, mark the coolant dipstick, do several heating/cooling cycles, and when cool again check level against mark, this will show any coolant loss.

Dexcool and some emissions have a similar smell and can be confused.

Edit: also check that the TB coolant hoses are not leaking;
and also and the coolant tube connections under the manifold.

[Bruce Melton]

I don't want to presume where you are in this process but this is a good tread:
http://forums.corvetteforum.com/showthread.php?t=634479&highlight=head+gasket

[ArKay99]

Did you check for bubbles in the coolant by looking down the radiator fill neck...?

Also, as Bruce mentioned, do a pressure test (pump fits over radiator neck with seal, pump up 20 psi with engine/coolant hot, see if pressure holds for several minutes, look for bubbles in radiator).

Also when cold, mark the coolant dipstick, do several heating/cooling cycles, and when cool again check level against mark, this will show any coolant loss.

Dexcool and some emissions have a similar smell and can be confused.

Edit: also check that the TB coolant hoses are not leaking;
and also and the coolant tube connections under the manifold.
Joe, I have a C5 vette and only a reservoir for the coolant. I suppose I could use the pump on the reservoir filler cap. However, I did notice the radiator return line to the reservoir, I think it's a 2 1/2" hose, could be squeezed easily and it doesn't appear like there is pressure in the system.
Also, I use a Nick Williams 90 TB and have a coupler in place, no leaks there. Also, I am NOT seeing any MEASURABLE coolant loss. I have to do several heat cycles with a mark on the reservoir to do this and I'm a little hesitant if I am getting coolant into other parts of the engine for obvious reasons.
One point of note. A good friend of mine with a modded 2000 FRC was talking to me about this and reminded me I have Kooks headers with an X-pipe and I should be smelling coolant from both pipes if it was in there.
So, here is my latest track. I recently removed and replaced the intake manifold and am wondering if I messed with the coolant block-offs at the back of the head. With the fact that all the plugs look the same, and I'm not smelling 'coolant' out of both pipes gives me encouragement. I don't mind pulling the heads, but I don't want to do all that work on a hunch. Thanks for the insight guys, I'm giving your suggestions a try and will determine the cause of this precisely before the heads come off.

[joecar]

'Vette's trick me everytime...

[ArKay99]

'Vette's trick me everytime...
It's doing a pretty good job on me too right now! :lol:

[Bruce Melton]

You do have a conventional radiator pressure cap on top of the rt side of the radiator. It is under the plastic panel that is on top of the radiator. The top line from the reservoir tank leads to it.
If you run a pressure test as suggested you will answer many questions.

[ArKay99]

You do have a conventional radiator pressure cap on top of the rt side of the radiator. It is under the plastic panel that is on top of the radiator. The top line from the reservoir tank leads to it.
If you run a pressure test as suggested you will answer many questions.
Thank you Bruce. I will do that. I never noticed it. I even had my radiator in and out twice.

[ArKay99]

Ok, I pressure checked the cooling system. FWIW, there was no cap on my radiator so I purchased an adapter for my tank. I first ran the car in idle to 190*F, I have a 160*F thermostat, and pressurized the system to 22lbs. for 20 minutes and didn't loose a kPa. Then I started the car and ran it and didn't see any pressure buildup. Then I used a coolant test kit for combustion gases and the liquid stayed blue. Also, I marked the tank and am not loosing any coolant, so I guess I am confuing my exhaust smell for something else.
On to the tune. I set all my idle parameters and IAC Parked and Desired Air to stock. Then I set my ETC to .0320. This worked wonders for the car at idle, just a little dip. So I added 2 g/s overall to my IAC parked and saw my RAFIG at -2, so I added -2 to the Desired Air overall. This fixed the throttle blip, but the car still wanted to surge and hunt incorrectly while rolling to a stop. I mulktiplied my throttle cracker table by 100% and this cured that. I now have a car that is very docile at idle and slow speeds, doesn't hunt and surge and idles almost like stock. I have some tweaking to do because at times it will drop idle rpm's and hunt a bit to recover, but at least I can drive it now.

[TAQuickness]

you've been busy. glad you got it worked out.