dimented24x7

iTrader: (2)

Ive still got the same ol' issue of the rpms suddenly dropping right after the motor starts. Ive also noticed that as soon as the engine speed gets high enough for the ecm to recognize it as being running, the IAC immediatly moves from its park position to the run position specified by the steps vs. coolant and such.

EDIT: I thought it might have been an issue with the park to run delay but even with the IAC unplugged it still seems to have a slight dip. Ive noticed that with the later $61 mask the dip isnt present. It comes up smoothly and when it first catches. Any (more) suggestions? With the help so far its staring pretty good but those first few 10ths of a second arnt quite as good as Id like. Maybe Im being a bit **** but it would be nice to get a nice fluid start as soon as the engine catches. Taking fuel out and tweaking the IAC counts helped alot but it still has that nagging dip that its had since I bought the car.

dimented24x7

iTrader: (2)

Heres a short snippit of a datalog taken during a cold start. There is .125 secs between each frame of data.

dimented24x7

iTrader: (2)

Hmmm... wondering if its maybe the sudden jump in timing when it first starts. The 0 (or whatever the starter turns it at) to 1100 rpm really is that fast. Almost like a huge fist punching one of the pistons and after that it drops off before it can gather it up again.

Grumpy

Look at the K/Pa.
Starts in the 90, during crank drops to the 70s then at first run is 50 then drops into the 30.
Initially there is no manifold vac.

Now look at the timing. During crank your on the module at what 6d timing?. Then the instant the engine starts, you have all sorts of timing at the high K/Pa low rpm area. Or a bunch of timing to decay out, either way you jump from 6d to 20+ instantly.

Me, I'd try closing the IAC a lil, adding a lil fuel, and work on the timing.

The stock strategy is to warm the engine up as fast as possible, which means lean and alot of timing.


The hint is, that without there being much vac the fuel stays in droplet form and just doesn't want to evaporate. It's heat, and the low pressure in the manifold that gets the fuel into vapor form.

dimented24x7

iTrader: (2)

The leaning out the fuel and closing the IAC a tad so it would pull more through the tbi was somethign I did last winter becasue it kept wanting to stall and flood right after it would fire. Major irritation when it was snowing and all I wanted was to get going. The timing is a definate problem. The start, idle, and drive all overlap eachother on the tables. That 20-25 degrees is necessary jsut to get that low compression pig of mine going, especially in OD. W/o it, it wouldnt even be able to maintain speed below 60 mph in OD. I guess its time I put together a seperate table for start and idle so I can run less timing. I did try the ANLU and whatever was in there, it started real nice... Didnt run good at all once it was going, but it started the way I wanted it to. Ill have to see what was used in there. Probably more gas and less time.

dimented24x7

iTrader: (2)

Experimented a bit with ramping the timing up on startup from the value of the main SA bias, which equates to zero, to the full timing in thats in the main SA table over about a quarter of a second. The warm and hot starts where quite nice. Smoother and not so abrupt. I wasted my one cold start for the day from having it take too long to bring in the full timing. Ill have to try again tommorow. Anyone agree/disagree that this is a good way to control startups, in addion to the things already mentioned?