cold/hot idle transition

[Ricky]

I'm probably going to get flamed for making another thread like this, but never mind

Also, sorry for the essay that follows

Had a proper mess around with my Bosch the other day, whacked up the max fuel quite a lot, way too much in fact for a car with no better cooling than tmic.. Anyway removed hot idle screw, unwound the idle screw to sort the idle, but my car never seems to have set hot/cold idles, like when I adjust it on the driveway it will idle ok, but once i've driven literally half a mile, the revs will nosedive, then shoot up, basically all over the place.

Now today I turned the max fuel down some, mainly because I am worried about EGT's and the like, and have kind of sorted the idle out, but again it's fine on the drive, soon as I move away it drops and buggers about again. Had another play and it seems much better idle wise, it will drop sometimes like if i touch the steering whilst standing still the revs will drop and require and tap on the throttle to get them up again. I just don't understand why it's fine idling on the drive when I first adjust it, but soon as i'm moving it will bugger about again?


Also, for people running T2, how much have you generally turned your max fuel up? Because when mine was wound in a lot, it was awesome to drive, so responsive lower down in the revs, but is the max fuel the only way of getting it to be this responsive, because now I have turned it down, it completely sucks to drive, even with a lot of LDA adjusting.. I just don't want to have it turned up if the EGT's are going to rocket out of control if people have found a better way of getting it to drive nicely.

[Ruan]

Have you removed the coldstart spring from inside the pump?

If not, I would disconnect the thermostat cable, set it right, then you know it's not going to arse about when it gets warm. The reason it goes into that wierd mode where at a guess it drops to about 500rpm and just shudders and jumps around? That's because the governor speed slows enough that it can't control the throttle enough to bring the idle back up... That's your antistall not working properly...

Have you tried putting in the throttle min stop just to bring the throttle off the stop, that can often help just having the throttle held up a bit - from there you can adjust the hot and cold idle adjusts on the back of the pump.

[Ricky]

Have you removed the coldstart spring from inside the pump?

If not, I would disconnect the thermostat cable, set it right, then you know it's not going to arse about when it gets warm. The reason it goes into that wierd mode where at a guess it drops to about 500rpm and just shudders and jumps around? That's because the governor speed slows enough that it can't control the throttle enough to bring the idle back up... That's your antistall not working properly...

Have you tried putting in the throttle min stop just to bring the throttle off the stop, that can often help just having the throttle held up a bit - from there you can adjust the hot and cold idle adjusts on the back of the pump.

Haven't touched anything inside the pump yet, not gov modded or anything yet.

I have screwed the min. stop screw back in so it's now resting on that, and it seems ok-ish now, the cold idle still needs sorting I think though. The only time it dropped down is when I tried rolling forward a bit just on the clutch, it was low enough to almost stall, but tapped the throttle and it raised back up again. Is the anti-stall to do with the screw that the throttle rests on?

I just don't know how much to turn the max fuel on average to get enough fuel for around 28psi, i'm thinking that just whacking up the max fuel will just damage things.

[Ruan]

You can tell by the smoke output, if you want a SAFE tune at 28psi, you need to ease off the max screw, you might even find that if you drop the max fuel, it'll carry on smoking, but boost will drop - that's because the hot, burning fuel that didn't combust completely in the cylinders is actually spinning the turbo faster, but because of various inefficiencies, it's still smoking it's ass off... Smoking on boost is NOT a good thing, you're likely to break and melt things - a puff of smoke as the turbo spins up is fine...

And yes, the throttle stop screw is known as the antistall screw... As I said, IMO remove the coldstart cable, and just run it fixed, so there's no difference between hot and cold, if your engine is healthy it'll run fine in this country without any need for the coldstart lever.

[Ricky]

The next thing I was going to ask was can I remove the cable and fix it at a decent rpm so that it wouldn't be too high for when its hot or too low for cold starts. Might try that tomorrow.

Need to fix a boost leak, get an EGT gauge and probably water injection before I turn it up again.. Now i've had a taste of what it goes like turned up that much I want it back! It's boring now it's turned down Thanks for helping by the way, I know this sort of question is probably asked day in day out

Anyone else with turned up Bosch pumps, is your idle set solid, or does it still have a few funny moments when under alternator load for example?