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Engine Runs Only With High Ignition Advance


Best Answer MichaelH , 30 October 2013 - 03:52 AM

Hi everyone,

 

finally I have some good news to tell!

 

This time, I strictly followed ACs recommendation and chose advance curve #6 (10°@1000, 19.7°@2000, 30°@4000rpm)

Afterwards, the engine ran better but still not very well. So out with the current needle and in with an AAU. I've chosen to adjust the jet two turns as a start. The engine ran better but still not very well… I've adjusted the mixture slightly and it got better. But there still was a lot of hesitation at acceleration… :-(

 

Then I went for the gas station and filled up the gas tank - afterwards, the engine ran perfectly fine!!!

So what happened?!? Obviously, it must have been caused by degraded fuel or I've filled up the tank with poor fuel the last time… I did fill up this year already but possible not enough to even out any degraded fuel?!? :-( :-(

 

Readjusting the mixture and the engine ran perfectly fine, no sign of any hesitation at acceleration any more :-)

I even was brave enough to go back to the other needle, adjusting the jet to my dealer's recommendation and the engine immediately runs perfect!

 

So I was obviously fighting two problems: wrong advance curve on the dizzy and poor, maybe degraded fuel…

 

So in the end, the engine runs very smoothly, picks up very strong in every situation with correctly set advance curve and a needle that does a very good job.

Thanks to the 123ignition and a static timing at ≈TDC, the engine even starts way better. You remember, at the beginning I ran something like 10° static advance which made engine start very awkward. Now it starts on the first turn even when cold :-)

 

I'm very happy now, even though I have to put the Mini into hibernation now (not forgetting to put fuel stabilizer into the tank ;-) ) until next year - but then the fun will begin! :-)

 

 

 

Thanks a lot for all of your help and best regards,

Michael

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#1 MichaelH

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Posted 13 October 2013 - 07:40 AM

Hello everyone,

 

I'm facing a problem that is very strange and which I cannot solve.

The engine in question is a 99H small bore, A+ engine. Slightly modified with a stage 1 kit, needle supplied by local dealer, type is unknown as declaration has been removed by grinding it out...

 

The engine basically runs very nice, pulls very strong although it suffers slightly lean mixture when accelerating for the first second or so - "thicker" engine oil in the dash pot helps for this problems.

 

My main problem is that I have to set ignition advance to ≈15° at idle speed!

Using the std. setting of 8° at 1500, the engine simply won't run, driving is nearly impossible, only using a lot of choke.

Advancing that much makes the engine run very nicely and it pulls strong.

So far, I've checked nearly everything:

  • Spark plugs, HT leads, distributor cap, finger and condensor, coil is all new
  • Valve gap is set correctly
  • leakage test was 12-17% (which indicates ≈40k miles engine in good mechanical condition according to my garage), compression test was fine, althought I forgot the figures :-(
  • Distributor was tested by the same garage and found to be working perfectly fine, mechanical advance worked as expected
  • I've recently checked the camshaft timing, inlet is on full open at 106° which is correct as per Vizards book. (As the problems good worse after some time and no cause good be found, I've assumed valve chain lengthening and a change in chamshaft timing, that's why I've checked this, too.)

I *could* go away with the high advance, especially as my local mechanic told me that every now and then some 99H pops up which refuse to run with std. advance - even in std. trim - and requires a similar high advance.

But - the engine is very close to knocking. Especially at low speed with very little throttle - where vacuum advance is active - the engine knocks. I'm pretty sure that it doesn't do so at higher revs as the total mechanical advance of the distributor is only 12° in total, so it does not even reach 30° in total. (I can't hear it knocking at high revs but given the loudness in a Mini, this of course is no real prove...)

 

There might be something wrong in general with this engine which I might miss but I really have no more clue... Maybe someone is having an idea what to do/check next?!?

 

 

Thanks for any input!

Best regards,

Michael

 

 

 



#2 Pigeonto

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Posted 13 October 2013 - 07:50 AM

15 deg with or without the vac advance ?



#3 ACDodd

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Posted 13 October 2013 - 08:26 AM

Is the mechanical advance working as it should? Is the tdc mark accurate?

 

AC



#4 MichaelH

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Posted 13 October 2013 - 11:27 AM

15 deg with or without the vac advance ?

Without vac advance - forgot to mention.

 

 

 

Is the mechanical advance working as it should? Is the tdc mark accurate?

 

AC

Mechanical advance is working, garage tested it on a test bench. Albeit I believe the maximum advance of 12° is a little bit lame. I need to look up the dizzy number again if needed but the total advance of this type was given as 6° (camshaft degrees) which I can confirm by measurement. The data sheet for the 99H engine confirmed the dizzy number to be correct but in my opinion, 12° total advance sounds a little lame?!?

 

TDC mark is correct, I dialed it in myself, using a dialer gauge on cylinder 1. Head was taken off, dialing in I did by measuring both rotation directions to achieve most accurate results.

The resulting mark I made was ≈130° off in respect to the original one but this might be explained by me using a large bore damper pulley where the alignment groove on the crankshaft is possibly on a different position?!?

 

 

Thanks for your responses and taking care of my problem!

Cheers,

Michael



#5 Pigeonto

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Posted 13 October 2013 - 01:17 PM

There was something like this recently-it may come up in a search.   I don't believe it actually is a problem nor that there is anything wrong. Every Mini I've had anything to do with will give a far better idle the more you increase the advance. So it's probably running at over 20 deg with the vac connected?  Don't forget that a part filled cylinder (idle) needs more advance than a full one. Sadly you can't do that with a dizzy as it's going to pink further up and at load conditions. I gave up and went over to Megajolt to get round this problem.   I see that AC is on the case and he'll confirm that when he saw mine it was at 33deg on idle. It will idle better if that is increased too; but he also informed me that the hc is high if you do that. Do carry on checking other stuff but I doubt you'll find anything. You can get into trying out locking off the mechanical advance but ultimately you may want to look into something like the Aldon Amethyst if you like distributors as you can set exactly what you want.** ps, otherwise it's a matter of setting as much advance as you can without pinking and then winding in the idle stop screw to get an idle.


Edited by Pigeonto, 13 October 2013 - 01:24 PM.


#6 ACDodd

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Posted 13 October 2013 - 02:45 PM

Most fast road engine need about 20 degrees of crank advance built into them. If you only have 12, then there is your problem.

 

Easy fix, have your dizzy advance curve adjusted such that;

 

With 10 degrees of static advance the dizzy swings in 20 at 2krpm and full in at 30 degrees at 3.5 to 4krpm. You also need a vacuum can with about 11 or 12 degrees of extra advance.

 

 

AC


Edited by ACDodd, 13 October 2013 - 04:43 PM.


#7 MichaelH

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Posted 13 October 2013 - 03:51 PM

Hello AC,

many thanks for your quick response!
That basically means that I've compensated the restricted advance curve by increasing the static advance...

So my next step will be fitting the 123ignition I recently came across. I wanted to fit this independently of the outcoming of this thread. If it solves my problem: great :-)
Its datasheet shows exactly the same figures you are telling, 10* static, 20* at 2k and 32* above 4k. By reading this, I already got doubts whether the current advance of 12* could be right..

So I'll give it a try and will report the outcome.

Cheers,
Michael

#8 ACDodd

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Posted 13 October 2013 - 04:42 PM

Hehe thats because I submitted alot of the curves!!!

 

AC



#9 MichaelH

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Posted 18 October 2013 - 04:25 PM

Hello AC,
 
yesterday, I've fitted a new distributor - a 123ignition.
The result after doing so? Well, I can see some improvement but the engine still behaves very strange.
 
After fitting, I went along with the std. setting of 8° at 1500rpm (vacuum hose disconnected) to be on the save side for the first start.
The engine did run as bad as always at the first drive. I then went on to adjust the timing whilst test driving until the engine ran fine.
When checking, the timing was set to 20° advance at ≈1000rpm (idle speed at that time) - again.
 
I did some more test driving, played a bit with the mixture (enriching it a bit) and I have now reached a point where the engine actually ran very good but hesitated a lot at acceleration - even when pressing the loud pedal very gently the mixture went lean for a second before recovering.
An indication that the damper rises to quickly in my opinion. I could solve that by using thicker engine oil (15W40 instead of ATF)
I still played a bit with the timing, advancing more help a lot, the engine becomes much more lively and picks up even a low engine speed in higher gears.
I again ended up having set the timing to 20° at roughly idle speed. At this point, I tried checking the engine's need for timing and turned the distributor until the engine ran best at idle speed - ≈20° of advance @1000rpm again!
 
I though about the mixture just being too lean and the huge advance needed to compensate - but then, at idle the mixture is rather slightly rich and the engine still wanted to have this massive advance...
 
I thoroughly listened for pinking, which is close to not present - it happens only at very light throttle, for example keeping 20mph in third gear (3.76 diff means 2000rpm) makes the engine slightly pinking. This was the same with the old distributor.
Currently, I've used setting number 4 on the 123ignition which means 10° advance at 1krpm, 17° at 2k and 30° at 5k 
I need to measure the timing at 2k and 4k when having a helping hand, but based on calculated values, I should experience 27° at 2k (which probably explains the pinking at this engine speed) and 40° at 5k - which seems a little high at the moment.
I possibly can eliminate this high advance by using a less step advance curve on the 123ignition, maybe.
 
I believe the next step should be trying a different needle which is slightly richer than the current one to ensure that the huge advance is not required to compensate a lean mixture...
I don't know if I can find the time to do before the season ends (seasonal number plates from april to october), having two kids limits time on the Mini :-) If not, this will be the next task for the 2014's season.
 
Many thanks for the help so far, I'll give feedback as soon as I've some new results.
 
 
Cheers,
Michael 


#10 lrostoke

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Posted 18 October 2013 - 04:39 PM

your messing with timing but are you sure the needle is correct.

 

You mention stg 1 kit, most stage one kits have been around for years and there are a number of needles which work straight out the box with no messing

 

AAU is standard one I had flat spots with this almost like turbo lag so went with the AAA, runs like a dream

 

instructions for stg 1 say 5 degrees BTDC @ 1000 rpm

 

personally I set at about 30 degrees @ 4000 rpm



#11 ACDodd

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Posted 18 October 2013 - 04:53 PM

Have you checked to ensure the TDC mark is accurate?

 

It is very likely the needle profile is anything but what is required!!

 

The AAA needle is usually too rich, a custom one is the most likely requirement to get a stg1 kit equipped engine to run right.

 

If the TDC point is correct set the timing at 10 degrees at idle. The get the needle profiled to suit the engine. Running too much advance can and does melt pistons!!! The worst situation you can run is too much advance and too little fuel.

 

DO NOT attempt to compensate for lean running by winding out the mixture nut. This will bore wash the engine and it will need a rebuild. The ONLY way this will run right is if the engine has the right advance curve and the right fueling curve to match.

 

AC


Edited by ACDodd, 18 October 2013 - 05:36 PM.


#12 jaydee

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Posted 18 October 2013 - 07:44 PM

imo your TDC mark is wrong. Not uncommon on these engines.

I'd try also curve D and curve 1 if i were you.



#13 KernowCooper

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Posted 18 October 2013 - 09:09 PM

Weak mixtures require more advance, I'd be doing some plug readings



#14 MichaelH

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Posted 19 October 2013 - 09:18 AM

Hello everyone,

 

Have you checked to ensure the TDC mark is accurate?

Yes, I've checked it twice now and the TDC mark is accurate - I know that all symptoms indicate a wrong TDC mark, so I recently even removed the cylinder head to be able to measure as accurate as possible and this only confirmed that the mark is correct.

 

 

It is very likely the needle profile is anything but what is required!!

The needle is the weak point at the moment as I don't know which type it is. It is one provided by Mini Mania Germany, Andreas Hohls which he sells for the stage 1 kit.

I trust Mr. Hohls a lot, having something like 40 years of experience in Mini business. So the needle shouldn't be too false. The only problem is that there's no identification left anymore so I can't compare to other needles. I've got an AAU needle at home, so will try this one next.

 

 

 

 

I'd try also curve D and curve 1 if i were you.

Based on what AC told me, I've chosen 0 or 1 as well, this should be very close to the figures given by him.

 

 

 

I'd be doing some plug readings

Very good point - I totally forgot to do that after all the testing. Checking the plug color is what I usually do but sometimes one forgets the most obvious things... :(

 

 

 

This engine totally puzzles me - in my 23 years of Mini driving, I've set up quite a few engines with stg. 1 kit and I never struggled that much to make it running properly... :( :(

 

I'll keep you updated!

 

Cheers,

Michael



#15 MichaelH

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Posted 30 October 2013 - 03:52 AM   Best Answer

Hi everyone,

 

finally I have some good news to tell!

 

This time, I strictly followed ACs recommendation and chose advance curve #6 (10°@1000, 19.7°@2000, 30°@4000rpm)

Afterwards, the engine ran better but still not very well. So out with the current needle and in with an AAU. I've chosen to adjust the jet two turns as a start. The engine ran better but still not very well… I've adjusted the mixture slightly and it got better. But there still was a lot of hesitation at acceleration… :-(

 

Then I went for the gas station and filled up the gas tank - afterwards, the engine ran perfectly fine!!!

So what happened?!? Obviously, it must have been caused by degraded fuel or I've filled up the tank with poor fuel the last time… I did fill up this year already but possible not enough to even out any degraded fuel?!? :-( :-(

 

Readjusting the mixture and the engine ran perfectly fine, no sign of any hesitation at acceleration any more :-)

I even was brave enough to go back to the other needle, adjusting the jet to my dealer's recommendation and the engine immediately runs perfect!

 

So I was obviously fighting two problems: wrong advance curve on the dizzy and poor, maybe degraded fuel…

 

So in the end, the engine runs very smoothly, picks up very strong in every situation with correctly set advance curve and a needle that does a very good job.

Thanks to the 123ignition and a static timing at ≈TDC, the engine even starts way better. You remember, at the beginning I ran something like 10° static advance which made engine start very awkward. Now it starts on the first turn even when cold :-)

 

I'm very happy now, even though I have to put the Mini into hibernation now (not forgetting to put fuel stabilizer into the tank ;-) ) until next year - but then the fun will begin! :-)

 

 

 

Thanks a lot for all of your help and best regards,

Michael






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