Cold and hot idle setting strategy ?

[Jaso74]

Hey all .

My idle is giving me the shi'ts and feel like going no where with it .
Originally wasn't bad other than a slight tendency to want to stall at idle in drive at intersections . At that time my ve table was standard and afr all over the shop so obviously getting it within the realm of not stupid lean or rich was priority . Well I have done that and now drives and runs pretty well, I've adjusted the accel enrichment a little and that worked well, adjusted timing table and stopped some pinging under accel roughly in the middle of the timing map, now putting a smidge back in at spots.
But , after around 8 drive and log cycles my idle sucks , well not that bad but yes crap .

So last night I reset all the idle iac tables back to std and plan to start again . I'm running 424 and $11p by the way on a 355.
Is there a logical route to get to a good cold start /warm up cycle idle , and of course normal op temp ?
I have seen multiple times get the spark turned up at idle to get the idle vac as high as possible , is that the critical step to do first ?
Is it worth while disconnecting the battery to undo any learn idle issues as far as iac behaviour ?
Any more tips ?

[vlad01]

I have not much problems leaving the setting stock, but a bigger cam with lots of overlap likes lean and will abruptly stall if too rich at cold and during warm up. Bigger cams also like heaps more timing at idle and light loads. You can just adjust the idle table and overlapping main table spark cells until the cleanest idle and highest vac is achieved. (closed loop idle indicator on the dash tells you when it's using the idle table and not the main table)

It is also extremely important to have the true injector voltage bias and linearity data entered in the tune, fake injectors don't cut it either, they must be quality and genuine items of what ever brand you have chosen. So far, only The1 on this forum can generate the data for them with the equipment he built specifically for that. Some manufactures of motor sport injectors have the data available/provided with them, but it's still not a common thing but slowly the pressure from the market is pushing this to become standard with the rise of engine tuning at the OEM type of level being the norm now, no longer the ex. carpenter who bought a dyno kind of idiot starting a tuning shop market.

If you don't have real quality injectors and the data for them, the AFRs will be all over the shop and it will be impossible to tune out.

I hope that helps. Best to start at the basics with the setup and make sure all of those things are right before going into the nitty-gritty of tuning, otherwise tail chasing ensues.

[Jaso74]

Thanks Vlad .

I'm making an assumption that the injectors are the standard factory item due to the shape and very aged look of them, it is by all account possible that assumption is wrong but that is what I have been doing so far. I really haven't touched it idle wise until last few revisions of ve table using spreadsheet data after logged drives.
Drive wise now I'm pretty happy with it and to be honest I really don't think I've done a lot .

From what you have said though I will check out and see if I have it too rich at idle and will punch up the timing too see if it is happier and can get good vac .

[vlad01]

Whats the PN on them and colour of the tops?

[Jaso74]

Black tops , part number 280 150 960 , well pretty sure that's the correct number ?

[vlad01]

Yeah, that's the stock late VP and VR injectors, 11p/12p stock data is for those as well as the 917s from earlier cars. So that should be all good then.

What are the cam specs? The stock injectors would be borderline big enough for anything more than the basic baby/"stage 1" upgrades, especially after a stroker kit. Something to keep in mind. But at the end of the day, as long as it can still tune in the VE at WOT and not tip the duty cycle to max (always good to aim for 80% or less to allow wiggle room for the closed loop fuelling), it should be fine.

[Jaso74]

Cam is a Mace 8180 -same same as a Crow 4503 , calculated 10.2 :1 compresion, 355 , std manifold, bit of a restrictive exhaust currently , single 2.5 inch. Honestly to start with more than happy for injectors to be just ok, most of the time just going to be a drive to work and around town ute . If it needs more will go that way if have to.

I have just had a go with all settings back to stock in idle settings, I lifted my idle spark advance and got my map kpa back to around 50kpa from previously 60kpa ish , I leaned out idle and no load area around it . Seem to have a much better warm up high idle already which makes me happy. I have backed off the idle screw on TB to get around 850-900 rpm idle and seems pretty happy there .
I think I will go for a drive and log some data shortly , see where I am at .
Thanks heaps for your help Vlad , good to have experienced help when it was starting to get on top on me a bit .

[Jaso74]

Ok got it 98 percent better all round for idle.
Wasn't going into closed loop idle before for some reason , probably something I had played with , my bad .
Anyway did some rt tuning to- in drive idle, park idle, fuel map and man it is sooooo much better now.
Thanks again Vlad !

[vlad01]

That's a decent enough cam, would need some 35-40 lb injectors, L67 ones should be enough but no harm going bigger.

With the idle screw, it needs to be set so the IAC steps in TP once fully warmed up and settled to be about 20 steps. Using the screw to adjust the idle is a no no as the ECU will try to compensate the IAC to get to the set idle speed in the tune, if the screw is adjusted too much out of range the ECU will have all sorts of issues trying to control the idle speed. To adjust the idle speed, first fix the screw to get the 20 steps and then set it in the IAC desired rpm vs battery voltage table. In 12P there are 3 tables, one for auto park and drive and manual trans, but 11P should be the two but I haven't touched 11P for years.

[Jaso74]

The max duty I've seen so far is a flash to around 85 percent, from memory that was at around 5000 rpm and the matching afr reading was about 13 so not too bad I thought.
Mind you I don't have much WOT data and heavy driving type data from the duty of injectors as yet . Sounds like it is something to look at in the future though .

I'm not sure on the 20 iac steps and how I get it there to set the idle screw afterwards ?