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MG Midget and Sprite Technical - Running hot....
| Chaps Tried various things at the weekend to overcome my annoying pinking problem. Basically trial and error in rotating the distributor body one way or t'other slightly, then giving it some beans up a conveniently situated mile long hill close by. On settling at this optimum setting, it was still pinking slightly at around 2/3000 under load, but any further retardation compromised performance. Performance by the by is very good.... Driving about further o'er Beinn and Glen, I discovered a relationship between engine temp and the propensity to pink. This was partially negated by pushing in the heater flap knob - in this weather, it was half out. This lowered engine temp a little and pinking reduced. My feet did start to broil a bit though....foot flap still a little open to disperse heat. In summary, I think I have done all I can to optimize the ignition timing - bar mess about further with the settings - it's a 123. I think the answer lies elsewhere - notably in reducing engine temp further. To that end Flush radiator and block and renew coolant Check thermostat Check for any air leaks at carb and elsewhere - weak mix could lead to slight overheating Anything else???? Thoughts welcome as ever Mark |
| Mark O |
| Mark... I think you have it as good as it can get At this point it would appear you need to schedule a 1/2 day on a rolling road/dynomo... for a final dial in I would get someone tyat knows what there doing, if they can set it up in 3 hours is alot cheaper then someone thats just playing and spends 2 days Id recommend peter burguss... there is not much he dosnt know Money well spent ...id at least drop a dime and have a chat with him about what he can do Prop |
| Prop and the Blackhole Midget |
| Prop I am at the other end of our fair land to Mr Burgess. It would cost an arm and a leg to get there and have the work done - and I am not convinced much improvement would ensure - given I have a 123. Also my time is free... It appears timing is not the root cause here anyways..... Thanks Mark |
| Mark O |
| Maybe prop can have himself shipped to your address... He can stock up on food and plant himself in a box while awaiting to arrive at your house. Then he can drive your car to Peters for a new head for his car. Solve your issues and you can ship him back home! Maybe if it turns out you like having him around you can keep him as a pet! LOL! |
| Steven Devine |
| Steve May I state here and now that my address is No 1 Kiwi Terrace Ruggerborough Auckland New Zealand NZ 23434 Cheers Mark |
| Mark O |
| it's a bit concerning if you're having to use the heater to cool the engine if you're going to clean out the cooling you might as well also do the heating at the same time ready for winter if you want my method of thorough cleaning for cooling/heating systems email me don't forget the simple solutions just because they're simple on the cooling system - internal or external blockages, water pump, cooling fan, pressure cap (seals, springs), fan belt and tension, etc. |
| Nigel Atkins |
| Warm weather driving, pinking and running hot - all most likely a slightly weak mixture. When it happens again, cut the engine, Freewheel to a stop and check the plug colour. |
| Guy W |
| Alright Mark. When he gets sent we will put a plastic bag in the box so he can poop in it. Or maybe a man diaper? I assume thats what your getting at! You may have to keep him as pet,as it may not be cost effective to ship him back. I think guy might be on to something with his diagnosis! Kiwi Terrace.... What a great sounding exotic name for a street! |
| Steven Devine |
| I just dont think this is a cooling problem/issue... I think the pissability that.its a carb needle and jet issue is a real possabity but I have to say at this point I really think this is still an ignition timming (0ver advanced) issue (most likely mid range)... it has all the classic symptons, over heating, pinking, and running rough If its not then its definatly as guy suggest ..carbs are 2 weak aka... it needs a new needle and jet re-profile...about 600 to choose from The reason im holding to the ignition issue and not joining in on the carbs at this moment is you have gone thur the entire fuel system several times and you made it clear, that its set up correctly snd have passed all the checks and test Before the 123 ignition was installed there was no issue with the cooling system...it operated fine...so its not a cooling blockage /wear issue... The only odd duck that dosnt fit and seems to be front and center with a smirk on its face is the 123 ignition system... surlock holmes has a popular fitting phrase, that says much better then what I can explain Being that peter burguss is not an option ...my next recommendation would be to re-install the old lucas dissy adjust "DYNAMICALLY" not statically and retest If the engine smooths out, runs cooler, and pinging is reduced... then you know its the timing, if there is no differance and it still runs hot, pinks and.drives rough then its safe to assume the issue is with the fuel/carberation system....thats how I woukd approach this issue for better clarity If I can make another suggestion if your going to be going back to fuel and carberation... Get a copy of danial stapletons most recent midget performance book, he has a chapter that is liquid gold on SU carbs, and determining what needle / jet profile is needed and how to modify the needle for situations like your in... if the carbs are the issue It really is a must read before you go any further with the carbs Prop |
| Prop and the Blackhole Midget |
| Here is a link to danials most "valuable" book. plus its on sale...LOL Prop http://www.amazon.com/gp/aw/ol/1845841425?c=n&qid=1373912876&sr=1-3 |
| Prop and the Blackhole Midget |
| Im begining to think that when you crack the whip on Prop he really does step to the plate! Look at that! He has done the research and has helpful tips to boot! Maybe Ill have to strap on the Man diaper and send myself to be kept as an American man pet! Wow! What the hell... Hmmmmm...... Its going to be tough talking my way out of this one. |
| Steven Devine |
| whilst it could still well be an issue of carb needle (singular), float, plugs, ignition or timing - if the coolant needs renewing or system cleaning then this will help even if it has nothing directly to do with the existing problem if the engine compression is high then the previous plugs may need to return now the timing is at or nearer what's required or it may be that the 123 needs to drop back one step (or more) on the adjustable switch setting, once it's about running well a rolling road session should hopefully tie up the variables and see if or what needs changing or adjusting for best (compromise perhaps) |
| Nigel Atkins |
| I mis-read Mark's first message and thought that the list at the end, already including flushing and renewing the cooling system, was of things already done. I now see it is a "to do list", so Nigel is right, makes sure the system is properly cleaned out. And whilst the system is drained, check what temp value your thermostat is. My suggestion of checking plugs and possibly richening the mixture was intended as a new thing to try. Just an easy 1/4 to 1/2 turn of a single screw, and as easy to reset if it doesn't improve things. I am not familiar with the 123 dizzy (well, I know what they are, but not how you adjust them). But if it is pinking I would be very wary of relying on a trial and error setting of the timing just by rotating the dizzy a bit. It is fine for getting started but very subjective and you don't really want to be blowing holes in piston crowns if you get it wrong! You really need a dynamic strobe and check it isn't going beyond 34 Deg at maximum. |
| Guy W |
| Chaps Obliged for replies. I too thought weak mix, and yes twiddling the airscrew in a little further may assit, but on load the main jet takes over so fiddling with the screw may have a limited effect. You may know I have the HIF 44 fitted - with the recommended needle BDL I think....so that is maybe an area for investigation. That said, it seemed fine before this warm weather, maybe it's just on the cusp, but warmish weather really should not make that much difference. Changing coolant and flushing may well assist in reducing running temp - also have electric fan so again twiddling here may be beneficial. Plugs, they look OK, are relatively new, so I'm not going to fiddle about. Thermostat also pretty new and standard setting. Ignition. Think I will reset the static and start again from there with a slightly more retarded mid range..... All in all though, not bad at present, climbs hills in 5th and plenty of low down grunt. A joy to drive really... |
| Mark O |
| << twiddling the airscrew in a little further may assit, but on load the main jet takes over so fiddling with the screw may have a limited effect>> Pretty sure that on my HIF44 the screw I am thinking of lowers the jet, so would richen throughout the rev range. In summer I change to a 82 Deg thermostat (Winter 87 Deg) Suggestion on checking plugs was to look at the colour, not see how new they were! ;-) |
| Guy W |
| Guy Many thanks, deeply obliged. Wasn't aware of that. I take it you mean the mixture screw - see attached image......Plugs look OK by the by |
| Mark O |
| Guy Image attached this time!  |
| Mark O |
| Yep, that's the one. The mixture screw. It operates a little forked plate inside which raises and lowers the jet position. Depending on the specific body design of your HIF (they do vary) the screw can be a bit awkward to get at as it is angled behind the air cleaner. Or maybe that is just with the rather over-sized air cleaner I use! I had to make a little angled head screwdriver to allow adjustment without removing the air filter. |
| Guy W |
| Guy OK good - I have a K&N cone air filter fitted. Access is not an issue. I shall fiddle away and see how the engine burns! |
| Mark O |
| The "little forked plate" Guy describes, bends as the fuel temp changes. The method of fuel temperature compensation, bi-metal blade aka -- little forked plate -- may be why you are having a problem. http://sucarb.co.uk/technical-carburetter-maintenance-settings-hif Type HIF Carburetter Introduction The type HIF (Horizontal Integral Float Chamber) carburetter has been designed primarily to meet the requirements of exhaust emission control carburation systems. Functionally similar to previous S.U carburetters, the HIF uses the variable choke/constant depression principle to achieve the precise induction of mixture required to control the toxic elements of exhaust emission to within statutory requirements. Float Chamber The float chamber is incorporated in the main body casting (see fig.2) ; access to the chamber is obtained by removing the bottom cover-plate (9). The moulded float (2) is shaped so that it surrounds the jet tube and is pivoted along a line parallel to the inlet flange. The float is retained by a spindle (6) which screws into the body casting. Entry of fuel into the float chamber is via a brass tube (7) in the side of the carburetter body to a needle valve assembly is of a spring-loaded design to prevent engine vibration affecting seating of the valve. The jet is pressed into the top of an aluminium tube which is in turn pressed into a plastic moulding (3). This hollow moulding known as the jet head is open at its lower and allowing fuel to enter the jet tube. Mixture Adjustment The jet tube of the HUF type carburetter is moved in the vertical plane to provide mixture adjustment only. Unlike previous types of S.U. carburetter the jet tube is not lowered down the jet needle to provide cold start enrichment. The jet adjustment assembly is comprised of a right-angled adjusting lever of unequal length arms riveted to a bi-metal blade (1. fig. 2). The blade is cut out to accept the jet head (3) and the shape of the jet head is formed so that any movement of the bi-metal blade is transmitted to the jet head, moving it in the vertical plane. The right-angled adjusting lever and bi-metal blade (1) is attached to the body casting by a spring-loaded retaining screw (5) positioned in the short arm of the lever. This attachment lever to be pivoted at the outer edge of its short arm and is loaded by the spring towards the jet adjusting screw. (4) The jet adjusting screw (4) is located at the outer end of the long arm of the adjusting lever; screwing the adjusting screw inward will lower the jet, enriching the mixture and unscrewing the adjusting screw will allow the spring to return the lever together with the jet, weakening the mixture. After the mixture has been set the jet adjustment can be sealed by fitting a plug into the jet adjusting screw recess of the carburetter body. Fuel Temperature Compensation (Viscosity Compensator) This device alters the jet position in relation to the metering needle to compensate for changes in fuel viscosity which takes place with changes in fuel temperature. When the fuel temperature rises, the viscosity is lowered, and in an uncompensated assembly, this would allow more fuel to flow for a given jet/needle relationship. In the HIF jet assembly the jet head is attached to a bi-metal blade (1). This bi-metal is immersed in the fuel in the float chamber and will move in the vertical plane in response to changes in fuel temperature. The jet will be raised to a weaker position on the jet needle when the fuel temperature rises and will be lowered to a richer position when the temperature falls. From this it will be seen that once the jet position has been selected by adjusting the mixture screw, alterations of fuel temperature will bring about slight alterations in jet position to compensate for the change in fuel viscosity. The effect of this device is that drivability is improved over wide ranges of temperature, and the exhaust emissions can be kept within closer limits during cold starting and the warm-up period. Temperature compensation also allows carburetters to have the mixture setting pre-set and sealed before a vehicle is delivered. |
| Lawrence Slater |
| Your profile says you have a "Fast road Kent cam" --. In addition to my previous post about the fuel compensation device, you may also want to check out your vacuum advance take off. Read this from http://www.minimania.com/classic-mini-cooper-diy-articles.cfm?id=726 Vac pipe take-off - There's always something to spoil the party! On some HIF carbs, the vac take-off sighted just after the butterfly - that's between the butterfly and the carb to manifold mounting flange - has been eliminated. Instead, the engines these carbs are fitted to use a vac take off in the manifold. The reason for this is again wholly idle emissions orientated. The higher vacuum that exists in the manifold area can be used to pull more advance. Theoretically this will reduce emissions at idle. Unfortunately it's exposed to induction pulsing. In the A-series, this is UGLY. The pulsing and high manifold vacuum causes rough idling. Particularly where anything 'sportier' (ANYTHING) than a bog-stock-standard cam profile is used. Classic example - the MG Metro. Its adventurously sporty cam makes for a slightly lumpy idle. This increases idle speed emissions, so Rover use manifold-sourced vacuum to increase idle speed ignition timing via the vac advance. We're talking 28 degrees of ignition timing here! Doesn't work because the pulsing created by the cam causes erratic ignition timing, culminating in running on. So an anti-run-on valve was fitted as a modification. Vicious circle. After messing about trying to solve the emission problems this caused, it was found that changing the originally quoted valve clearances to 0.014"inlet /0.017" exhaust (effectively reducing the cam over-lap) helped dramatically. And, like I said earlier, the sportier the profile, the worse it becomes. Even worse - when running, this system can cause ignition advances in the order of 50 degrees on lift-off and on again - an absolute sure-fire recipe for savage detonation. The solution is easy - remove the vac take-off from the manifold and fit it back to just in front of the butterfly where it should be. |
| Lawrence Slater |
| Lawrence All good stuff, many thanks. I think my first port of call is correct mixture adjust - slightly rich if need be. As regards vac advance, my take off is on the mounting flange - just in front of the butterfly - so no probs there... |
| Mark O |
| Interesting points you have squirrelled out there Lawrence. I never realised that the metal fork was connected to a bi-metal strip. My engine spec is very similar to Mark's. Same cam, same carb, big valve metro head, 10:1 compression (well it was once, before the wear took over!) I run my cam at 14 and 16 thou settings. My HIF still has the vacuum take off on the right side (intake) of the butterfly - I didn't realise that they weren't all like that. |
| Guy W |
| Guy, as your car is a similar set up to to Mark's and you drive in a spirited way and have a few hills around you what have been your experiences during this hot weather with pinking and, allowing for gauge reading variances, temp gauge readings as a comparison of similar |
| Nigel Atkins |
| Why Nigel? Mine is a similar spec, but a different car. There is more than enough scope for the sort of adjustable variation that might cause a bit of pinking! Would a photo help do you think? |
| Guy W |
| true Guy I think a good rolling road person (almost put guy) with their equipment and knowledge may well be able to find the cause and hopefully get round it and have the engine running at it's best sometimes even you mighty engineers with your cerebral imagery and problem solving skills, experience and knowledge (nay intuitive reasoning) leave somethings to other experts to sort or do a photo - well the one Mark posted of the carb drawing did ! Mark put up photos previously at the start of the threads/problems so no another one now probably wouldn't on this particular occasion at this particular juncture probably wont help more but generally yes photos help no end and the sooner they're put up the better - no they wont always help but many times will |
| Nigel Atkins |
| Nigel I think the basic nub of the issue is that the dork behind the wheel of my car fiddled about too much without completely understanding the consequences. It is only due to the enlightenment provided by this wonderful forum that aforesaid dork now realizes the error of his ways, and will thus venture forth sub-bonnet, armed with the true knowledge of exactly how a wee screw can b*ugger things up! |
| Mark O |
| I'd never bothered to properly read all that stuff about the mixture and vacuum take off either until yesterday. Very interesting. I do seem to remember reading somewhere about disabling the fuel temp compensation device too, but I can't find it now. |
| Lawrence Slater |
| Hard to imagine how you could disable it if it is a metal strip. Other than to remove and replace with a plain brass alternative. |
| Guy W |
| The bottom line is, its near inpossiable to dial something like this in without a rolling road All you can do is guess and flip coins The only other option is to pull the bonnet, sit on the engine with tools and test equippment and get someone almost as stupid to race up and down the road at various speeds while you dial and fine tune everything in Its almost impossiable to recurve a dissy with the engine sitting static and no load put on it... like going up hill Thats why most dissys get proper recurved at a shop that has the equipment and not under a shade tree Granted... you can dig up alot of dirt, smelt it, and create your own iron ore then recook it with carbon then press roll it then shape and bend a fender out of it,, or you can just buy a fender...a good rolling road man can set this up in no time...1/2 day tops....esp because its a single carb Even if it only $600 ... what will it cost to have new pistons and rings and a basic rebuild done if you burn a whole in the top of the pistons from trying to sort this with alot of detonation taking place The bad thing is, you cant just send this to a pro and have them recurve on a machine because its so electronic...once you unplug the power you loose all your settings But I really think you have dialed it in as.far as you can go without a $500,000 rolling road, to finish the detail work. Prop Prop I |
| Prop and the Blackhole Midget |
| Mark, you have discovered the most troublesome part of the car, the nut behind the steering wheel and as Guy would no doubt point out theses are different in almost all cars |
| Nigel Atkins |
| Nigel et al You are indeed correct, but perhaps overall I have done more good than harm. In this particular case, my assupmtion that mixture was OK based on adjustment being confined to low range only was incorrect....Throwback to being used to older motorbikes I guess - pilot jets etc..... I have yet to adjust the mixture screw, but I am confident it will solve matters...richer mix, cooler engine, no more pinking... I have to take issue with those who are insistent that some sort of rolling road test is necessary for correct ignition. It isn't. With a bit of trial and error, and a basic understanding of what advance the car is at a particular rpm - easy for me using 123 tables - I believe you can get pretty close to the optimum setting. Again, I would re-iterate that due to the configuration of the engine and all other variables, the correct advance at a particualr rpm is unknown anyways. Tuning shops may improve matters for me, but I think to such a slight extent that it really is not worth the effort and cost. |
| Mark O |
| Mark, "AHHHH the pupil has become the teacher!" Good for you. I see your brain is in gear. It looks like you are getting some good Ideas on this discussion. |
| Steven Devine |
| Mark is right. For much of the life when these cars were in production very few would have had access to a rolling road. That didn't mean that they couldn't be set up perfectly well with a bit of care and thoughtful adjustment. And yes, my car has been on a rolling road but needed very little adjustment at the time. And yes, a rolling road may be a good thing where available but it is as much down to the experience of the operator with your type of engine as it is to do with the equipment. But it certainly isn't the only way of setting a car up properly. |
| Guy W |
| Actually... the dissy pros had machines to recurve the dissy...it was more art then science The problem is her, this is fully electronic, you cant simple fill out a form and send it with the dissy to a dissy shop and have it recurved Mark does make a point... you can recurve using simply trial and error, eventually you will hit.the sweet spot... but how many combinations plus how many needle/jet combinations ... ive got to guess at least 15,000 combinations...just the needles alone im guessing 200 differant needles I think finding the correct combination code by trial and error on a 56 numbered lock with 4 key hits would be far easier Prop |
| Prop and the Blackhole Midget |
| Here is a stupid idea that might work What about jacking the rear end up, starting the car, but it in gear, and set.the parking brake....its crazy enough it just might work if it dosnt catch fire 1st At least you would be able to put the engine under Load... to get a some what of a closer spec. Prop |
| Prop and the Blackhole Midget |
| ******I have to take issue with those who are insistent that some sort of rolling road test is necessary for correct ignition. It isn't. With a bit of trial and error, and a basic understanding of what advance the car is at a particular rpm - easy for me using 123 tables - I believe you can get pretty close to the optimum setting. Again, I would re-iterate that due to the configuration of the engine and all other variables, the correct advance at a particualr rpm is unknown anyways.***** Hahaha...now thats funny The obvious retort is.... cool, go do it....what are you bothering us for. Hahaha Prop |
| Prop and the Blackhole Midget |
| One thing you might be able to do Jack up the rear end run the engine and set the parking brake so that its fairly locked but still.able to allow the wheels to roll... If you have enough rear brakes it would certianly place enough load on the engine Its a thought... I dont know how well that would work... the good news is, you wont actually attempt to try this as your very resistant to anything that people in the know here have to say... this has been going on 6 months, I dont understand what it is your looking for...you have gotten sound advice,not just the advice your looking for. Case in point... are you going to re-install the old dissy ... set dynamically and test to see if the issue is a carb problem or an ignition problem ??? Just curious.. have you even called a local shop with a rolling road to see what the cost would be ??? But yeah... its still fun ... and hoping for the best for you Prop |
| Prop and the Blackhole Midget |
| there is absolutely no need to go for a rolling road tune up unless you have a problem and can't find the cause or solve it yourself or you want the tuning spot on or bettered (or ego sheets of course) and if you go to the wrong tuner or when they're not at their best you will get very poor or no value but if you're able to go to Peter Burgess then the value is so good that even small gains are a benefit plus if you go to a tuner their experience and/or equipment and could pick up other areas of variations/faults/problems Rylan didn't complain about the performance of his car but taking it on a rolling road saw big improvements (and it wasn't even at Peter's great value and results but elsewhere) I'm sure Guy and Mark and their like can get to 97%+ (97-100%(?)) performance without a rolling road if all components are working as they should I'd be happy if I could set the carbs just to make it to the tuner not on a flatbed :) |
| Nigel Atkins |
| Sorry for my last post...it was supposed to be deleted....back from the grave like a zombie Prop |
| Prop and the Blackhole Midget |
| Nig... I sort of disagree....if this was a convdntional dissy ... then no you would not need a rolling road... you could simply fill out a form and mail it with the dissy to a recurve guy, and get it back in a week and your ready to go Because this is fully electronic it has to be set up on a rolling road On a mild engine... sure you can get away with just an adjustment here and there and be done But marks car is vary high performance iirc his CR was 10+ This is not goig to be a case of running the rpm to 4500 rpm and setting the timing at 32 degrees Prop |
| Prop and the Blackhole Midget |
| other way round Prop, if the dissy is mechanical there is more variation because of wear, I remember Peter putting that refurbed dissys seemed to last about 3 years before they start to wander off again (I don't know if that includes the ones from Dissy Doc), where as Mark has a pre-set 123 (not 123Tune) |
| Nigel Atkins |
| Must admit, I wasn't talking of re-curving a dizzy, electronic or otherwise. But of doing the standard settings of tappets, timing, carbs to get the car running at an acceptably good standard. With experience (owner/driver or good garage mechanic) I think this can be perfectly acceptable for normal fast road driving and decent fuel consumption. If you are racing, then a rolling road may get you the few extra percent in the HP needed to be successful. But on the road that really doesn't matter and overall drive ability is probably more important anyway |
| Guy W |
| c'mon then Guy would you get it to 97%, 98% or 99% I think one of the main elements to performance is usually forgotten - driver training and/or ability (or like in my case lack of it), back to the nut behind the steering wheel |
| Nigel Atkins |
| Trick question Nigel? How would I calculate whether it was 97%, 98% or 99%, without knowing what the 100% measure was? I have not argued that rolling road checks and adjustments are not a good thing. Just that the cars were designed for maintenance by low-tech methods 50 years ago, and that for normal day to day use this should still be sufficient today. Not everyone lives within convenient distance of an RR experienced in A series engines, and not everyone wants to spend the £100+ that I understand to be a typical cost. |
| Guy W |
| Guy, you flatter me, I didn’t even think of the maths part, just wanted to see if you’d rate yourself I’m also with you that many can get by very well without a RR tune but again example the huge improvement on Rylan’s car from taking it to a RR tune up/problem solving the cost depends on where you go and how accurate the reputation for A-series expertise remains – with my present Midget I’ve been to two A-series RR tuners, one was a very high priced visit and low outcome and the other was - Peter Burgess, much lower priced visit, excellent outcome so really excellent value for money (incredible value for money compared with the other expert) I’ve also been to another low value RR tuner - and with my previous Spridget to an excellent old skool RR tuner who sadly died many years ago now |
| Nigel Atkins |
This thread was discussed between 15/07/2013 and 18/07/2013
MG Midget and Sprite Technical index
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