charge temp inverse temperature term

[V8hilux]

Hi,

Heat soak engine still running lean after hot restart.
vn v8. with delco 808. $12P

I changed the figures in this table as shown and it seems to fix the problem. It's more evident lean hunt at idle and just above idle.

What is this table actually doing to richen the mixture? am i on the right track ? will this cause any problems? was thinking about moving the air temp sensor into intercooler pipework instead of the manifold to see if that will fix the issue. or will this fix do the same thing?

chargetemp.jpg

[vlad01]

Fark! - 24 K. that colder than physics allows

Sorry I had to

yeah I am interested to see what that means too.

[VL400]

That table allows small adjustments to the mixture by adding some correction to the charge temp term. It allows you to adjust say when the ECU reads 56 degrees treat it as 49.58 degrees as per your table. There is more info here on all the charge air temp terms but it points to your threads https://pcmhacking.net/forums/viewtopi ... gas#p28618

What you have done to the table is not correct though, when the charge temp is genuinely at temps 80 and above the ECU wont be calculating fuel very well. There are some tables that allow for post start enrichment but these are for the few seconds after starting.

Got anymore info on the lean problem? How long does it run lean for? Got a log of it? Fuel pressure ok post start?

[VL400]

Fark! - 24 K. that colder than physics allows

Sorry I had to

yeah I am interested to see what that means too.

The table has an incorrect label. It got changed to degrees C in later 12P versions to make it easier to read but must have missed updating the XDF

[V8hilux]

First thing I thought it may have been was low fuel pressure caused by either hot wires or bad regulator... went out and bought all the efi fuel pressure testers and all looks good. I mucked about with this same table last summer and it seemed to help with the leanout apon a hot restart. If I drive the car till operating temp on the highway and pull over, I can start it straight away and the afr's are good. if i wait say 2 minutes, then restart it, the afrs are still good. If I wait say 5-10 minutes after hot shutdown. Thats when I get the lean afr's. 18-19:1 at idle and light throttle. It will stall the engine and is a pain in the arse especially if i want to duck into a shop to get something.

If I wait say, 30 minutes when the coolant temp goes back down to around 70C it will start fine and the afr will be back where I want.

The lean condition will continue untill I get out on the open road with the coolant temp comes back down to 92C

I know by looking at the mechanical coolant temp gauge if the lean hot restart will occur or not. If the coolant temp gauge is showing 90C or under, it will start fine.
however If I take too long in the shop and jump back in the car and if the coolant gauge is showing 95C-110 C I can virtually gaurantee it will run lean apon restarting. I usually have to just go for a walk up the street for half an hour to save the embarasment of the stalling/hunting etc of the lean hot start. Haha. POS.

I ordered a new intake air temp sensor a couple days ago and it will be interesting to see if this thing is the source of the problem or not. I have an idea of leaving the original in the manifold and running this second one in the intercooling pipework with a toggle switch in the car so I can choose which sensor the ecu reads off at the flick of a switch.

I was also suspecting that the battery may have been losing volts due to the heat in the bay affecting the injectors or ecu but the compensation tables for volts vs pulsewidth have been tweeked and I think I have that eliminated. Only thing I haven't done is probe the ecu with the multimeter to check volts at high temps.

[V8hilux]

Delco wizzid posted this in another thread and maybe he is onto something here.:

if i remember right Charge Temp - % Coolant contribution for calculating charge temp Vs RPM & MAP is a table to adjust what % of its charge temp calcs are performed by coolant temp sensor and air temp sensor so it makes the ecu use more of the air temp sensor as charge temp value or more coolant temp depending on % in the table.youll see at idle in the table its useing nearly 100% coolant temp as the value its useing for the calcs as the manifold heatsoaks and would give incorrect charge temp figures as the sensor pretty much reads coolant temp at idle from the heatsoak . edit and at revs high map its using the air temp sensor reading more due to it being the best way to work out the charge temp with mass flow of air going over it

The problem is more at idle so I might get brave and have a play with this awkward looking table and try to steer the intake temp more toward the iat sensor at idle rather than the coolant temp. I'll have a go tomorrow and report back.

[VL400]

Any log of it happening? Being turbo its got bigger injectors right? Could it be that on hot restart the inj PW are too small and its not actually injecting as much fuel as you think? This could be due to the injector opening and voltage bias settings not matching the inj.

You also mention coolant temp but what's the mat reading through all this? Should be able to see in a log of two restarts, one hot with the issue and one hot without, what (if any) difference there is with the ecu.

[antus]

Could it be a bad or wrong type of MAT or CLT sensor?

[V8hilux]

as far as I'm aware the mat and coolant sensors are original and factory. they appear to work fine in the logs.

The manifold is aftermarket (come racing ttb) and they say that it delivers cooler charge than factory banannas due to the more open design.

I'll do a couple of logs and see what that shows.

I'm also starting to get excited about welding in my new "accessory" for the ute. Check out this bad boy:

2013-06-06 13.25.45.jpg

2013-06-06 13.29.07.jpg

[VL400]

That should get some air flowing!!