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Post by clifford on Sept 13, 2020 17:51:35 GMT
Trying to sort out a carb for my engine, a 998cc A+. From the 'GuessWorks' de-coder I get "HS4 FZX1415" so that's what I've got myself! When I started to strip it for a refurb I noticed the vacuum-advance take-off is downstream of the throttle butterfly, so on the manifold side! Never seen one like this before so looked into it and it seems this was done late in the HS4's life to meet emission regulations (apparently the HIF has it this side too). Surely this means you get maximum advance at idle, which just doesn't seem right to me. At least, it's not what I'm used to with any other classic I've owned.   I also discovered that it's not uncommon for mini owners to blank this off and drill a new take-off the 'correct' side. ie. air inlet side of the butterfly. Hoping someone on here might be able to enlighten me on what's best to do for an auto. Cheers, Clifford. |
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Post by jockduck on Sept 14, 2020 11:10:55 GMT
Hi, I think you are right in your observations, I used to own a 1967 Holden HR(Australian G.M.) , when it first came it was a manual but the vacuum take off was that for an auto and the idle was all over the place, I drilled a new hole and plugged the old one, later I put an autobox on the car and found I had to change over the vacuum take off again to improve how the car idled while in gear. You may have to experiment to get things running right, sometimes getting the emissions right compromises drivablity.
Jock
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Post by notamini on Sept 15, 2020 15:05:27 GMT
So just to be clear, the auto has the vac port on the manifold side and manuals have it on the intake side?
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Post by jockduck on Sept 16, 2020 11:06:02 GMT
Not on the early cars they are the same as manuals, the problem seems to be when emissions are being chased then normal engineering goes out the window.
Jock
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Post by notamini on Sept 16, 2020 15:10:51 GMT
My car was built with California pollution specs. It has the large pump on it. So where would the port be placed? What results would I get if I moved it from where it is to the other spot?
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Post by clifford on Sept 20, 2020 17:48:29 GMT
Hi, I think you are right in your observations . . . . . . . You may have to experiment to get things running right, sometimes getting the emissions right compromises drivability. Thanks Jock, experiment I will, your experience has reassured me. From what I've been able to glean from various websites and forums, the HS4 was available in a multitude of variations, certainly some had manifold side take-offs and others with air filter side (known as 'ported') take-off. Apparently the later mini had this HS4 with 'manifold' take-off, then went to the HIF, which again had the manifold side vac. take-off. These minis would have had either Lucas 41882A or 41907A distributers, which have a maximum vacuum advance of less than 10". Earlier minis would have a different vacuum advance unit fitted to the distributer with a much greater maximum advance. So, it's not simply about changing the position of the take-off, the dizzy would also need to match the new setup. One of the problems is, as Jock said, the manufacturer was seeking lower emissions, something which doesn't concern me as it's a kit-car on a 'Q' plate so only gets a basic test at MOT time. The other problem is that advice on various forums and specialist tuning sites is generally from those seeking maximum performance, and invariably from a manual too, so is also of little or no relevance to me. I'm after that elusively perfect blend of driveability and economy. One site I visited did mention that with manifold take-off you get maximum advance at idle, giving a lumpy idle but greater economy, which reduces to zero advance as soon as you open the throttle, thereby providing more torque for pulling away. Not sure if the theory behind this is sound but it would be nice if it were true. However, I would have thought an auto at idle but in 'drive' would need more power than a manual and so wouldn't be happy running even a little bit lumpy. Not so sure where this leaves us. As I haven't even got my carb. rebuilt, let alone fitted, and I'm a long way from being ready for the road, (I don't even know if it runs yet!) I shall take the easiest option and leave well alone. Plenty of other things to keep me occupied in the mean time. |
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Post by jockduck on Sept 21, 2020 11:01:22 GMT
Just to confuse the issue further, a modern programmable ignition system is a great thing, very flexible makes a great difference to how the car goes, much better than fiddling around with a worn distributor.
Jock
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