Measuring distributor max timing advance

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Brit01
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Re: Measuring distributor max timing advance

Post by Brit01 » February 18th, 2013, 11:25 pm

Been out for a test with the 150 mains. No improvement. But no loss of power, in fact very good (when it wasn't pinging!) so it's not getting too rich. Maybe even more power than the smaller mains.

Really quite impressive especially with the straight trumpets, just wants you to push the gas down more and more after 3500 rpm. Torque is impressive for a 25 year old engine! Great fun!

I've retarded it a bit more and will try another day.
Also with a smaller plug gap.

With vacuum advance connected: great off idle acceleration
without vacuum advance: poor off idle acceleration in comparison but just a tiny bit less pinging.

Still leaning towards altering the upper advance curve with the springs.

Brit01
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Re: Measuring distributor max timing advance

Post by Brit01 » February 19th, 2013, 12:40 pm

Regarding the smaller spark plug gap I was thinking about the flame kernel.

The larger the spark the fatter the kernal I believe.

If i decrease the kernel size with a smaller spark wouldn't this slow down the burning rate and possibly assist in reducing the knocking?

Thanks

Brit01
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Re: Measuring distributor max timing advance

Post by Brit01 » February 21st, 2013, 12:06 pm

Ok well I managed to get to the distributor last night.

The new springs that were ordered twice have not arrived again. I think they may be they are putting the wrong country on the pack! Got some Alfa keys from Bulgaria in 9 days! 99.9% of my stuff arrives in 2 weeks.
What are the chances of a small jiffy bag failing to arrive twice!

Anyway I decided to add some preload to the spring as recommended by another Alfa owner for weak worn springs.

Will test it tonight as it's been raining for 2 days solid.

Brit01
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Re: Measuring distributor max timing advance

Post by Brit01 » February 21st, 2013, 10:29 pm

Well I seem to be getting somewhere now at last.
I had no knocking today!!!

I adjusted the slack/pre-load on the second spring last night.

The first spring is under tension normally and is good up to 1500 rpm.
The second one has about 6/7 degrees of slack and comes into play after 1500 rpm, Then the sum of both control the total advance after that.

I modified the second spring(I have a spare), and took out this slack to pre-load the total more. I knew this would have an effect on the off idle acceleration though.

When fitted and started her up she was very retarded. I adjust this round to 8 degrees static, factory mark on flywheel.
With the vacuum pipe disconnected and revved she advanced visibly slower which was the idea.

With vacuum attached she advanced nicely above 36 degrees fast. Good.

Warmed her up and took her out.
Gave her a thrashing and NO PINGING!!

Advanced a little more, 5mm or so ( 1 degree more approx). and pinging came back, backed it off to 8 and all good so far.

What I would like though is to have this slack back in the second spring but a stronger spring. (H&H have failed to deliver again - maybe they are addressing it incorrectly - very unusual).

I also notice one of the spark plugs ground electrodes looked a bit hot. You know the change in colour around the ground electrode can indicate the heat rating, well this change in colour was more near the thread on one of them.
maybe go to a colder plug.

Also maybe just because I was thrashing her about the coolant was a few degrees hotter which was strange and a bit disturbing. Thought without the detonation she would have been cooler. ??

Regards

Guy Croft
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Re: Measuring distributor max timing advance

Post by Guy Croft » February 21st, 2013, 11:44 pm

some good intuitive work here Chris, so..

MODEL POST!

GC
Guy Croft, owner

Brit01
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Re: Measuring distributor max timing advance

Post by Brit01 » February 22nd, 2013, 12:49 am

Guy Croft wrote:some good intuitive work here Chris, so..

MODEL POST!

GC
Thank you guy. That's a nice compliment.

Of course it was inevitable I'd feel a little loss in power due to the reduction in advance but there is always a compromise as you do not want detonation.

Still some tweaking to be done as this was a test to see if retarding the mid range advance would eradicate the detonation.

The slack in the second spring is important I see to get good advance up to 1500 rpm approx for good off idle acceleration using the first spring only until the 2nd kicks in. Now there is no slack so it had been compromised.

So I believe a stronger second spring is needed but with that 6/7 degrees of slack for the static-mid range rpm timing.

Guy Croft
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Re: Measuring distributor max timing advance

Post by Guy Croft » February 22nd, 2013, 12:52 am

to be honest Chris - I know of no-one who has explored this in the way you have, it is laudable to say the least..



any other member share my opinion?


G
Guy Croft, owner

Brit01
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Re: Measuring distributor max timing advance

Post by Brit01 » February 22nd, 2013, 12:58 am

Guy Croft wrote:to be honest Chris - I know of no-one who has explored this in the way you have, it is laudable to say the least..



any other member share my opinion?


G
I have felt very alone with this issue to be honest. (not much interest from other members - I had a similar thread on 2 other Alfa forums also and very little interest) although I have had good contact with Tommi here (some pm's also) which have been motivating and useful also.

I am really suspecting the Uruguayan made fuel E10 with low MON level that was introduced here a couple of years ago. I believe the burning rate/properties have changed with this modern fuel that the original distributor was not designed for.

I know in Europe and USA you can buy good fuel so maybe I am alone with this issue.

Best regards and thanks again

Chris

Brit01
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Re: Measuring distributor max timing advance

Post by Brit01 » February 22nd, 2013, 3:39 pm

Fingers crossed that my AFR will work again tonight.

The company just informed me that I need to calibrate the device OUT of the exhaust!!! It did not state that on the instructions and most calibrate in the exhaust.

Invaluable piece of equipment I hope will start working again.

Urbancamo
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Re: Measuring distributor max timing advance

Post by Urbancamo » February 22nd, 2013, 7:43 pm

Yes Chris, every single lambda calibration instruction has said that you must calibrate your lambda sensor with same air you breath 24/7.

Dear blokes, the main issue here is very low quality fuel Chris is forced to use. I was surprised how low quality it really was when Chris sent fuel datasheet to me. European 92 RON pump gas is similar. Most fuels we have are much better. Many countries doesn't even have 92 RON fuel anymore!
So bit complicated situation but I think Chris has managed to solve this issue masterfully.

Even you have not extreme skills, you can overcome them with careful studying and great interest. Life is nothing but learning from birth to grave.

-T
GC_25

Guy Croft
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Re: Measuring distributor max timing advance

Post by Guy Croft » February 22nd, 2013, 10:12 pm

hi Chris and Tommi

believe me, if I wrote everything I knew - incl, here - observations about low grade fuel - I would never do a stroke of work.

And then there would be NO forum!!

The reality is that some - here - are experienced and write about their knowledge, some are not exp and tend to read rather than post, or are reluctant to post because they feel they may something wrong and be criticised, and some are very experienced and could write but don't take time to.

Anyone who knows GC will know that I encourage everyone to take part - unless I specifically say not to.

This is forums for you!!

Thank you both for your very significant contributions.

Your only payback may be that some will learn from you! You never get paid and usually never know!!


G
Guy Croft, owner

timinator
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Re: Measuring distributor max timing advance

Post by timinator » February 23rd, 2013, 12:24 am

Hi Chris, you have learned a lot in getting to this point. The process of engine tuning requires more effort than most are willing to expend. I didn't want to jump in before now because you were doing so well. I have had my Sun 400 model 51-1 distributor tester since 1978. It doesn't do anything more than let me document the curve. Knowing where to adjust the curve goes pretty much as you have done so far. So well done.

Because you have determined that your existing advance curve is very close to what you need I would suggest that you bend your heavy spring back to it's original shape. Instead of putting on heavier rate springs try grinding a small amount of weight off the big end of the secondary weight. Your experience has been an over advance at a very precise point in your curve. So tune that point instead of changing the entire curve. I install heavier springs when the rpm range of the engine is increased.

Remember that each gear is it's own tuning system. !st and 2nd gear can usually stand more advance. 3rd is where the engine can stay long enough at rpm to show problems.

Brit01
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Re: Measuring distributor max timing advance

Post by Brit01 » February 23rd, 2013, 6:31 pm

Thanks very much gentlemen. It's good to receive compliments.

I had a 100 km run last night, various conditions.
All good in all gears except on the highway at high speeds in 5th when under load up a steep hill, just a slight pre-ignition at high speed when pushed very hard.
I think the plugs were getting too hot.

Plugs showed up too hot IMO. Almost whitish, very very faint brown. Not even any colour change on the ground electrode. Usually there is a mark indicating whether the plugs are too hot or too cold.
I have changed them to B9ES today and will test tomorrow.
I have a photo of the plugs to show later.

Not sure if I'm ready to shave off metal from the weights yet. Maybe if I had a spare distributor to play with. But good suggestions thanks.

Got to go.

Regards

Chris

Brit01
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Re: Measuring distributor max timing advance

Post by Brit01 » February 24th, 2013, 11:34 pm

Well just got back from a 100 km run. A lot of traffic and wife and kid in the car but felt better in 5th gear (couldn't hear that well due to kids music playing!!). Colder plugs may have done the trick.
Had a couple of opportunities to try WOT under load in 5th and it sounded smooth.

But most definitely my engine prefers the projected type of plugs. Better off-idle acceleration and in the idle circuit in general. The P plugs also ran a little cooler, I mean the coolant.

One thing I noticed is the oil pressure at idle was a little lower than normal.
I'm suspecting the larger main jets are diluting the oil a little at higher speeds on the motorway.
I need to go back to smaller mains maybe unless the oil has sheared and needs changing but I doubt that very much with only 3500 kms on it.
Last thing I want is bore wash with oversized mains.

Brit01
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Re: Measuring distributor max timing advance

Post by Brit01 » February 25th, 2013, 6:24 pm

As promised photos of the BP8ES plugs.
For me too hot. (ignore the black on the 2nd 3rd thread, carbon from previous run some months ago)
Or just on the limit as they are a nice tan colour. So better off with a slightly colder range.

I changed them to B9ES and haven't heard any pre-ignition yet.
But I do want to change them to BP9ES (projected) as they did feel more responsive especially 1-2000 rpm.

Regards
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