Measuring distributor max timing advance

Post pics of your car in here
Urbancamo
Posts: 317
Joined: August 8th, 2011, 1:04 pm
Location: Finland
Contact:

Re: Measuring distributor max timing advance

Post by Urbancamo » February 6th, 2013, 11:32 pm

Chris

I'll start from the top. Factory timing marks are factory timing marks. Usually not 100% accurate. I've seen them throwing off by 1-3 degrees from reality. If that's gonna be issue - I don't know.
If detonation still occurs with modified distributor, I would simply retard the ignition advance until detonation goes a away. Detonation is some serious issue which should be solved.
And I always trust my timing light when looking at timing. Advance should be checked with that even you have all programmable FI and ignition. I know one bloke who blowed his engine because laptop said ignition advance is around 30 degrees when in reality it was 60 degrees!!!!!

Do you have possibility to test any other, higher octane fuel or maybe octane booster if that's gonna change a thing? Like a have spoken in the past, I don't know how good quality the fuel in your country is. And trust me - there is difference between fuels.

Also how hot your engine coolant runs? Hotter the coolant, more prone to detonation. That why race engine always run cooler than factory engines.

Emulsion tubes. Coudn't find the table with all dimensions and drillings but I found a picture of all 9164 emulsion tubes. Tubes you quoted seems to be similar, but .4 has extra drillings just in the middle.
.4 tube might lean midrange a bit more than .2. But until I found the factory table for 9164 tubes, this is just guessing.

And finally, are you 100% sure that the noise you hear is really detonation? Cars with dual carburettors usually make very weird noises depending on throttle position, load etc...

There are really 1000 and 1 variables. Bit of long shoot really but interesting topic for sure. Guy, could this be in Road-section?

T
GC_25

Brit01
Posts: 825
Joined: June 28th, 2011, 4:54 pm
Location: Uruguay

Re: Measuring distributor max timing advance

Post by Brit01 » February 6th, 2013, 11:59 pm

Urbancamo wrote:Chris

I'll start from the top. Factory timing marks are factory timing marks. Usually not 100% accurate. I've seen them throwing off by 1-3 degrees from reality. If that's gonna be issue - I don't know.
If detonation still occurs with modified distributor, I would simply retard the ignition advance until detonation goes a away. Detonation is some serious issue which should be solved.
And I always trust my timing light when looking at timing. Advance should be checked with that even you have all programmable FI and ignition. I know one bloke who blowed his engine because laptop said ignition advance is around 30 degrees when in reality it was 60 degrees!!!!!

Do you have possibility to test any other, higher octane fuel or maybe octane booster if that's gonna change a thing? Like a have spoken in the past, I don't know how good quality the fuel in your country is. And trust me - there is difference between fuels.

Also how hot your engine coolant runs? Hotter the coolant, more prone to detonation. That why race engine always run cooler than factory engines.

Emulsion tubes. Coudn't find the table with all dimensions and drillings but I found a picture of all 9164 emulsion tubes. Tubes you quoted seems to be similar, but .4 has extra drillings just in the middle.
.4 tube might lean midrange a bit more than .2. But until I found the factory table for 9164 tubes, this is just guessing.

And finally, are you 100% sure that the noise you hear is really detonation? Cars with dual carburettors usually make very weird noises depending on throttle position, load etc...

There are really 1000 and 1 variables. Bit of long shoot really but interesting topic for sure. Guy, could this be in Road-section?

T
thanks for your input.
Today when I was looking at the marks on the flywheel with the timing light it did jump to the second mark pretty fast which is just shy of the max 36 degrees.
As you mention factory marks can be fairly inaccurate.

I want to try the original airbox again to bring in more cold air.
99% sure its detonation - like a can of nails being shaken. Luckily its an old school engine and very robust with wide bearing journals minimizing the damage that can occur. I always let off the throttle the second I hear the noise when testing.

Under normal acceleration it is fine. But its an Alfa and designed to be driven hard with no issues using WOT.
I know the carbs sound different at varying rpm. When at 5500 they really sing!!

Yes very true about the 1000 and 1 variables.
I'm determined to find the root cause of this.

btw - retarding it more than 7 degrees static has a horrible effect on the performance. First it heats up very fast when idling and acceleration is slow and lumpy.

8-9 degrees makes a great difference

Coolant (when 8 degrees static) is cool and stays cool. When stuck in traffic with 30+ degree temps the fans will kick in every 2-4 mins approx. just a guess but pretty stable.
High speeds it will maintain nice and cool at about 82-83c. (thermostat opens at 83-86)

Brit01
Posts: 825
Joined: June 28th, 2011, 4:54 pm
Location: Uruguay

Re: Measuring distributor max timing advance

Post by Brit01 » February 7th, 2013, 12:26 pm

One variable I want to rule out tonight is the air temp coming into the carbs.

It gets very hot under the hood and the filters are currently sucking in this air. (I know you will be frowning at this set up)

I will install a different sealed airbox and funnel in the air from in front of the grill.

I've had other friends with the same filters as my current ones with no issues but every case/engine/set up is different.

Let you know later tonight or tomorrow.

Brit01
Posts: 825
Joined: June 28th, 2011, 4:54 pm
Location: Uruguay

Re: Measuring distributor max timing advance

Post by Brit01 » February 7th, 2013, 10:54 pm

Big big improvement with the sealed airbox with a routed tube going in front of the grill to bring in cool air.
Couldn't test it fully due to heavy traffic but almost solved I think. Still a hint of detonation but getting there.
The cooler air most definitely helped a lot.
I think some forced air induction from the front grill will also help at higher speeds, please correct me if I'm wrong.

But I need to route another tube into the box as it was slower to respond and I felt it was lacking a little air under WOT and higher revs. It wasn't as responsive. Bit restrictive I believe as I had to force the flexy tube in between the rad and cross-member.

I would also still like to experiment with the springs once they arrive, especially as I spent some effort trying to locate them.

I really want to set the static timing at 9 degrees because it does make a difference when accelerating and also when idling in hot traffic keeping it cool.

I think nothing wrong with your distrib ... and resist
N: I did a test with the vacuum advance attached to the manifold port (car stationary with no load) maybe it was idling at about 10/11 degrees of advance, I blipped the throttle with the timing light and it went way past the max timing mark extremely fast, maybe past 42 degrees. No pinging as it wasn't under load but the springs allowed it to advance way over its max mark of 36 degrees.
I guess this was due to the strong vacuum advance still maintaining its hold as it wasn't under load.

Brit01
Posts: 825
Joined: June 28th, 2011, 4:54 pm
Location: Uruguay

Re: Measuring distributor max timing advance

Post by Brit01 » February 8th, 2013, 11:32 am

This is what I'm thinking of making next week.

You can see the original air intake to the box. I compared this with the other K&N oval filters and short trumpets. The oval filters rev much faster and have more response at mid-high revs. But at the cost of sucking in hot air.

When I tested it again with the original airbox on I noticed a loss in throttle response and mid-high rev response BUT the detonation had almost disappeared.

I'm proposing to add an extra air intake tube from the other side of the box to bring in more cold air and hopefully make the throttle response better (less restriction).

I've seen other boxer engine owners do the same mod.
Attachments
filter small.jpg
filter small.jpg (168.89 KiB) Viewed 5380 times
air intake mod.jpg
air intake mod.jpg (158.46 KiB) Viewed 5380 times

Brit01
Posts: 825
Joined: June 28th, 2011, 4:54 pm
Location: Uruguay

Re: Measuring distributor max timing advance

Post by Brit01 » February 9th, 2013, 1:58 am

I'm trying to think when the detonation started to appear.
I'm guessing but it may well have started when I bought new cams and tappets. Could these have altered the timing and conditions?
The tappets were not original Alfa ones, they were INA. Maybe giving a different lift.

Maybe just a worn out distributor which i heard from my Alfa forum does happen. A quick fix is to bend the spring pegs to pre-load the old springs.

Well a lot of variables discussed here and ones to try altering.
Air intakes, distributor springs and fuel mixtures.

Brit01
Posts: 825
Joined: June 28th, 2011, 4:54 pm
Location: Uruguay

Re: Measuring distributor max timing advance

Post by Brit01 » February 10th, 2013, 11:29 pm

Another thing to consider is that the detonation occurs in 3rd gear between 3300-3600 rpm WOT (not 3/4). Other gears no.
This appears to be causing the right conditions.

Maybe an increase in a size of the main jet is required.

I get back to my car on Tuesday evening so first I will try the original airbox but with extra air intakes into the box.

Next test can be with the short trumpets and filters (which give a better throttle response) and the larger main jets. Maybe its just going lean in this small range and needs 150's or larger.

Brit01
Posts: 825
Joined: June 28th, 2011, 4:54 pm
Location: Uruguay

Re: Measuring distributor max timing advance

Post by Brit01 » February 12th, 2013, 10:32 pm

I changed the filters back to the original airbox with an extra big cold air intake tube to rule out the detonation occurring due to hot air soak.

No improvement!

It doesn't occur under load at any other rpms in any gears other than the range between 3200 ish to 3600 WOT.
Mostly in 3rd, a little in 2nd but none in any other gears.

So next variable could be the secondary distributor spring? (hasn't arrived yet!)

Brit01
Posts: 825
Joined: June 28th, 2011, 4:54 pm
Location: Uruguay

Re: Measuring distributor max timing advance

Post by Brit01 » February 13th, 2013, 12:31 pm

One of our kind members on the forum may have hit the nail on the head here.

My fuel here has a MON level of just 83! (97 RON)

I read for an engine of my compression a MON level of 87 min is required.

I have tried bottles of standard additives here with no effect. Maybe the low level of MON needs a significant boost.

So if it is MON related how do we go about rectifying this?

A different distributor curve to retard the timing between 3-4000 rpm?
2-3 bottles of additives per tank?
A quantity of racing fuel?

A new car with ECU?

Brit01
Posts: 825
Joined: June 28th, 2011, 4:54 pm
Location: Uruguay

Re: Measuring distributor max timing advance

Post by Brit01 » February 13th, 2013, 1:41 pm

What is your knowledge on adding toluene?

Brit01
Posts: 825
Joined: June 28th, 2011, 4:54 pm
Location: Uruguay

Re: Measuring distributor max timing advance

Post by Brit01 » February 13th, 2013, 3:24 pm

Think I may have found a source for aviation/race fuel. 99.6 MON 100 RON.
And it's only 15% more in cost!

Still investigating but if I can get this and mix it with premium problem solved I think.

OK my brotherinlaw adds 50% of this juice with regular fuel with this Ford Shelby with Holley Carbs/MSD iginition.
Hope I can get a sample to try a tank.

Brit01
Posts: 825
Joined: June 28th, 2011, 4:54 pm
Location: Uruguay

Re: Measuring distributor max timing advance

Post by Brit01 » February 14th, 2013, 12:01 pm

I think getting the race/aviation fuel is going to be too impractical. I don't think I'll find a supplier/outlet in the city here. I know they have it at the race track to buy but it's not close.

Will try the bigger main jets. I understand using ethanol mixed fuel can oxygenate the mixture slightly. This may not be helping.(unfortunately I think my jetting man is on carnival holiday this week - not answering!)
I will try a high dosage of octane booster.
Also strengthening the secondary spring to retard the curve above 3000 a little.

Apart from these variables there is not much else I can do (last resort is installing thicker head gaskets to reduce compression which will not happen unless we invest in a second car!)

Regards,

Chris

Brit01
Posts: 825
Joined: June 28th, 2011, 4:54 pm
Location: Uruguay

Re: Measuring distributor max timing advance

Post by Brit01 » February 14th, 2013, 7:39 pm

I guess it could be possible to also grade the crank pulley myself with a protractor.
Line it up at BTDC. Attach a pointer and mark in white paint this mark.

Then using a protractor mark in 5 degree increments white marks on the pulley. Then I can see how quickly it advances at 3300 rpm (the pinging zone) with the timing light because on the flywheel it only has the 3 marks, very basic.

Brit01
Posts: 825
Joined: June 28th, 2011, 4:54 pm
Location: Uruguay

Re: Measuring distributor max timing advance

Post by Brit01 » February 15th, 2013, 3:06 pm

A local here has found suppliers of Toluene and made his own additive with good results.
Next week I'll be looking for some quantities of this.

Apparently this is the correct formula:
Maybe start of with a litre or 2 per 30 litres and go from there. It's anti-knocking properties like TEL are more important than the actual octane level I believe.

Toluene has octane rating of 114. So use this formula to figure what octane you get when you mix toluene with gasoline:

Litres of gasoline x Octane (eg.95 or 98) + (Litres of toluene x 114)
Total Litres of Gasoline & Toluene
exampleThe fuel tank capacity of an EVO 8MR is 55 litres. Based on a 30% toluene mixture, filling it with
16.5 litres of toluene and 38.5 litres of 98-octane gasoline will yield a fuel mix of:
(38.5 litres x 98) + (16.5 litres x 114)
55 litres
= 102.8 octane

Brit01
Posts: 825
Joined: June 28th, 2011, 4:54 pm
Location: Uruguay

Re: Measuring distributor max timing advance

Post by Brit01 » February 18th, 2013, 2:03 pm

Just got back from my local carb specialist.

I have had my mains enlarged to 1.50 (from 1.45). (didn't even charge me again but I gave him a tip of a few bucks!)

I want to see if a little extra fuel will help eliminate this frustrating knocking in the narrow range of 3300-3600 rpm.
I did try some smaller ones(1.42's) the other week and the detonation was in fact a little worse so I may be on to something.

Post Reply

Who is online

Users browsing this forum: No registered users and 5 guests