After deciding that I will require a vacuum pump to do the adjustments I was hoping to do to the warm-up cam (which the waxstat moves), thought I should do something while it was nice out. So I decided to look at the 'fast idle' speed, the nominal 3000rpm (on my EZ engine) that never really makes itself known during normal operation, but is important to the cold-start system. I knew that the 'sheared-off-head' screw that adjusts this had been tinkered with 'cos I played with it when I was having probs a year or two back, mislead by an ill-thought-out illustration caption in Haynes 1081 which made me think it was something it wasn't. It's not that hard to get this back to how it should be . First be confident that your timing/ignition components are all set up right/fault-free. Then warm up the engine until the fan has run once. You need to be able to read the revs reasonably accurately, so ideally hook up your 'widget' to the coil, if not you can just use the rpm gauge. Also, the vac hose which needs to be unplugged/reconnected is invisible without a mirror, so use one, or consult the books, or diagrams on this site until you're happy you can find it by feel. It's the very lowest attachment point of any vac hose on the whole carb, I believe. Be careful of hot manifolds! The procedure, as set out in Haynes 4177, (maybe also in 1081), is (with engine idling) to unplug the vac hose, colour-coded brown from the lowest port on the 3-point unit (3PU), and see what the engine revs go up to. Don't be tempted to stop the engine with the key after noting this rev reading, 'cos it will tend to run-on with this hose off; instead just slip the hose back into its correct position. This will bring the idle back down to how it was. Then, unless the result was a pleasing agreement with the specified 3000rpm (according to engine code), you'll need to adjust the 'sheared-off-head' screw in the appropriate direction for more or fewer revs. The right-angle bracket it screws through could be bent instead, but I felt small adjustments to the screw with a pair of small grippy pliers was more 'controllable'. Screwing it in towards the actuator of the 3PU will increase this fast idle speed, and vice-versa. Obviously the 'normal' idle speed will be thrown out of kilter by doing this; but that's pretty easy to get back right with the 13mm hex-head on the back of the 3PU. On first disconnecting this hose my fast idle speed was about 2700, not far out, but I thought i'd get it closer. Overadjusted and got 3600! Typical me. Got it back down in stages to the desired 3000, then readjusted the 'normal' idle to the 950 I believe to be right, with the 13mm hex-head. (Though there's a conflict of opinion for EZ between Haynes 4177 (750rpm) and Haynes 1081 (950rpm)). If your CO level was right at this idle speed before this tinkering, it should still be the same after you've reattained it. Easy really, should have done it ages ago... I should just emphasise that this adjustment/set-up has nothing to do with the waxstat. As long as the engines at temp. and the sheared-off-head screw is actually pressed up against the throttle actuator of the 3PU, the waxstat's irrelevant. Also, if you're not absolutely sure you know which bits I'm referring to here, don't attempt this. My usual apologies for lack of piccies, and wordiness...
I've a mind you'd be happier with a weber and a manual choke. Can you delete the duplicate of your post
Tried! I'm as happy as Larry with my Pierburg, but I know what you mean. Tried to find how to delete the duplicate, dunno how. Asked the mods to in an edit to the top one. Got a 'fatal eror' message on the first attempt, so assumed it hadn't gone through. Sorry folks. Edit: Kind of done it now... Anyone think there should be a separate 'Carburettor' forum? Edit: And this post is for info only, to those with Pierburgs, let's not have a debate about Pierburg/Weber, think everyone's heard enough of that.
I still reckon revving an engine at 3K from start can't be good for the engine. But then what do I know? Maybe I'm trying to justify my starting revs of 200
It doesn't though! Funny thing is that this 'fast idle' speed is completely hypothetical. It doesn't rev the engine to 3000 from cold, that's what it does with the 3-point unit at max extension when the engine's warm. But it does affect the early stages of the cold start system by determining the primary throttle angle while the TTV makes the 3PU stay at the full thrust position. Sounds like a foreign language dunnit?
Que?! So what idle speed would you expect from cold then? I expect that would depend on how cold it was though. In the same way mine idles at 900 when warm, but at 200 when cold. I think I'll read that chapter again....
Yeah, colder it is, the harder it is to turn the engine, so a throttle angle that would result in 3000 rpm warm, causes a much lower engine speed when cold. According to the guy that used to do refurbs on e-bay, the correct behaviour is around 2000rpm while the TTV is cold, which will be a very short time (second or two) unless really frosty, or the wiring to it is duff; then drops down to around 1600 as the waxstat takes over the rev-holding function, then progressively down to normal idle speed as the waxstat warms and the choke goes off. I've yet to hear a truly convincing argument that this sequence isn't right, though I know one or two dispute it. Correct functioning of the pull-down unit, and choke electrical heater are also critical to this sequence working as designed.
Mine would idle to 2.5-3k ish when REALLY cold for a second or 2, then drop straight down to 900ish and stay there. Rock steady. No matter what. I believe this is the correct sequence of events for a fully working and healthy 2e2 carb Of course I've never tried driving a brand new MK2, and unless someone who did own one from new says otherwise I'm sticking to my theory! Mine ran faultlessly this way no matter what the weather was like, never stalled, never missed a beat. Milage was out of this world, 300miles to 20 was easily achievable, sometimes more! I think 750rpm is too low, unless this is some uber base idle setting with a load of stuff disconnected The abattery light starts flickering at around 800 on my GTI! gbk: The VW owners manual tells you to rev the engine to no more than 3k when cold, so no problems there Mike: I'm sick of people going on and on about how much better webbers are than the 2e2, this is simply not true
Can't argue in terms of 'if it works let it be' w.r.t. start-up rev situation . But I don't see what the guy on e-bay ("golf_2_specialist" I think he called himself) had to gain by describing a detailed wrong sequence? The vast majority of his feedback said things like 'runs like new again', and no-one said anything about him having got the cold-start stuff wrong. I suppose I might be able to get a response direct from Pierburg, if they can be ahst. Mine did idle fine at 750 (really quiet!), and the dash light stopped flickering once I'd cleaned up the volt-reg ground connection. Then I took it to a garage to get them to set the CO level up right, their machine (with VIN number/registration or whatever keyed into it) said it should be 950, so they adjusted it to that, and the CO level to 1%, again as the machine 'thought' was correct. It seems perfectly happy like this so I'm leaving it, though a bit reluctant to be told what to do by a machine! Edit: It would be really helpful if a few others with Pierburg carbs that work OK would chime in here and describe what their revs do from cold-start. I'm just as happy to be in the wrong here, just want to know what 'normal' behaviour is...
tbh I wouldn't worry what it does from cold, as long as it runs right! I'd prefer it to idle at 950rpm rather than 1600rpm though, that seems quite high to me!
It does rev a little higher than 1600 for a minute or so, but then comes down nicely, and then does indeed run fine, smashing mpg and running nicely up and down the rev range. I've sent a query to Pierburg, but not too optimistic about getting a reply As I hope you (all) realise, I'm not out to prove I'm right and rubjonny's wrong, that would be enormously ungrateful of me after all the assistance he gives us, across the technical spectrum; just want to get to the bottom of what Pierburg intended this carburettor to do, from cold, rev-wise. Edit: oh, and golf_2_specialist's no longer a registered user on e-bay, so that might indicate something...
Am I right in thinking that the waxstat is adjusted when warm? So wouldn't this be the same situation as the fast idle, i.e that it's adjusted to give 1600 (or whatever) using the tool when the pin is withdrawn when warm but when cold will be less, say 900?
so what would be the logic of waxstat after overtaking rev-holding function. let say if idle is 900, if you drive car really crazy at higher revs and temperure of coolant goes to about 110 C, then if you stop car and leave it at idle, idle should be more than 1300 caused of temperature of coolant and pin will extend more and rpms goes higher. so as coolant is cooling temperure let say fall to 70 C, and pin goes back and idle rpm goes to 600, 700 right. i have played with waxstat, cam and its function, really hard to get back warming position when car is just started at cold temperature. my car works totally different. after i start it, revs goes to 2000 for about less than second and goes downt to about 700, and after few minutes goes up to about 1400 1500 and after car is at working temperature goes back slowly to 900 a stay there. crazy right ?!
if temperure is about less then 10 C in the morning after i start it revs goes to 2000 for a second and goes even lower at about 500. and after car is warming goes up to 1500 and before working temperature indicator is at working possition revs goes down 900. so as much temperature is lower indication from 2000 to lower revs, goes even lower to about 500, if temperature is at about 25 C, revs goes to 2000 for a second and goes to 900 and then upin' to about 1400 and then before wokring temperature back to 900 crazy.
Almost the opposite gbk: Nah, mate. The waxstat is minimally extended when cold, which leads to higher revs, via the cam, and a return spring, and it's interaction with the primary throttle. It sticks out further as it warms, lessening it's influence on the primary throttle to zilch at full operating temp. The Pierburg setting tool actually sits in the spot where the waxstat would be (you take it off), and has projections 2.0mm one way round (to set up the adjustments in imitation of a 'cold' waxstat), and 8.15mm the other way (you unbolt it and turn it round) to set up things for the warm condition. There are two caphead screws which move in slotted holes, and another sheared-off-head screw, which all conspire to put things in just the right spot. I think the warm-up cam even has a shape such that when the waxstat's fully warmed up and extended the counteracting spring pressure is taken off it, to de-stress it; that's speculative though, 'cos it's all very confusing down there...
I think that's what I meant When the wax is cold, the pin is withdrawn, which would give rise to higher revs because of the springs and stuff and when warm and extended would 'push' the revs down. What I meant was that the revs are measured when the car is warm, even though you're simulating a cold waxstat. Shexuel: I'd get a weber.
shexual, sounds like you arn't getting enough coolant flow to the autochoke & waxstat, just like I told you on msn
I think you're confusing the waxstat adjustment with the 'fast idle'. They're quite independent. The waxstat setting is done with engine off, possibly even carb off the car. You never look at revs, it's just the physical positions of the stops/cam/throttle-angle etc. that get set with the 'tool'. Shex: I agree with rubjonny about the coolant issue, but also think the symptoms you describe could be down to the pull-down unit not doing the right thing. If you start the engine from cold, with the airbox removed so you can see what the choke flap is doing, it should move immediately to an angle so that there is a 2.8mm gap from the bore of the venturi; then more slowly (over a few seconds) open further to make a 5.6mm gap. I doubt that yours is doing this.
