89 HC NA 2.2 timing issue

[Tonibilly]

Hello all,

First post here, can anyone help?

Car is Esprit Stephens 89 HC N/A with Constant Energy Ignition system.

Static timing I set the crank to TDC then the two cam sprocket dots are together and aligned, so that's good, no valve contact with pistons!. So far so good. Then I set the crank to 10 degrees BTDC, this is the static timing stated in Lotus Notes. At 10 degrees the contact breaker pips should be aligned and rotor arm pointing to No1 HT lead, thus firing the spark plug. Great all is well. I start the engine and point the timing light to the window provided on the flywheel cover, lo and behold 40 degrees appears in the window. This means the engine is running at 30 degrees static advance at tick over. At 10degrees advance you should see 20 in the window since at TDC it's the pointer next to the window that points to TDC on the flywheel and you see 10 in the window. At 20 advance you see 30 in the widow and at 30 advance you see 40 in the window.

In my case I see 40 in the window so that's 30 degrees advance at tickover, correct. I didn't even think an engine would run at that much static advance.

My problem being that if I back off to 10, the engine is running way too retarded at tickover and is impossible to drive on the road as it just won't accelerate cleanly. I reset to 30 advance (40 in the window) hey presto all is good, car runs a dream.

So currently I'm running with 40 in the window so 30 degrees advanced at tickover, but it can't possibly actually be that, because I'd be be at something like 60 advance at 3,500 rpm, impossible i'd say.

Oh, I've used two timing lights and both say the same.

wots appenin!!!!!****????

[hilly]

Has you dizzy got vacuum advance/retard????

If so did you unhook the vac line while checking the idle timing????

At idle your engine will be running at pretty high vacuum which will be pulling in the vacuum advance, as soon as you try and drive it you will be running at ambient air pressure when accelerating and the advance will be taken out,hence if you adjust the timing with the vac line attached it will drive rubbish.

Hilly

Edited August 3, 2009 by hilly

[910Esprit]

Bear in mind that the static setting is not an exact science as its a magnetic trigger (not a contact breaker), its only an approximation to get the engine running. Once its running, the flywheel represents the actual situation and there is no need to be adding or subtracting anything.

Maybe worth checking the flywheel maks are accurate (e.g. you could drop a rod through a plug hole and check with a dial gauge to get true TDC)

Whilst performing your checks, have you revved from tickover to 3500 revs? (to prove the mechanical advance is working).

May also be worth checking you have the correct distributor with the correct advance curve.

As its an NA car, I would not be too worried about your current method of setting the timing (i.e ignore the flywheel marks and set as far advanced as possible without pinking under load).

cheers Steve

[Tonibilly]

Hi again,

The dizzy has just one vacuum line attachment, i'm pretty sure this is a multi advance / retard. This doesn't move the timing marks at all when i disconnect or connect it at idle. Lotus notes states 22 crank degrees vacuum, but is that advance or retard? Funny thing is, that 22 degrees would account for the 20 odd degrees of advance that i'm seeing, so maybe that is the answer. Should I see vacuum retard of 20 degrres which I'm not getting at idle?

Slowly increasing the revs puts more advance into the window reading, so the auto advance weights in the dizzy are working, smoothe and even with increase in revs, so dizzy appears working good. Haven't checked the vacuum operation yet tonight as I need more hands, one to hld the light, one to increase the revs and one to disconnect and connect the vac tube. I'll try to get to that tomorrow.

Thanks for your inputs Hilly and 910esprit, I did think of checking TDC by feeling a piston rise / fall but again need more hands.

I'll post again when more info available.

There can't be anything major at fault since the engine runs nice under load, even if it does show 30 degrees advance in the window.

It can't actually be 30 degrees advanced because it runs good, but why is it showing 30 degrees.

Hot from the garage,

I have zero vacuum from the Thermal Ignition Control Valve, which means I'm missing out on 20 degrees of advance at idle, consequently it will run good at 30 degrees setting because it would be at that anyway if I had the vacuum.

One thermal ignition control valve should cure the fault, plus reset to dynamic 10 degrees with vacuum disconnected, then when i reconnect, hey presto 30 degrees at idle.

Why didn't I think of that.

Thanks again Hilly and 910Esprit, you jogged me into it. Fantastic stuff.

I'll let you know the final outcome.

Cheers for now.

[hilly]

Good stuff

Hilly

[Tonibilly]

Hello again,

89 2.2 HC N/A with Constant Energy ignition and vacuum advance only on dizzy.

After some further investigations today and this evening, it becomes apparrent that there is only vacuum to the dizzy advance at tickover when the engine is cold below 60 degrees temperature.

Once over 60 degrees temperature, the thermal ignition valve switches the vacuum from manifold (very high vacuum so lots of advance) to the front carb throttle edge, very low vacuum until the throttle is opened some, then you get vacuum pulses because of the piston suction on the inlet stroke.

So, my theory about getting no vacuum advance at tickover is blown out of the water and I'm still running at 30 degrees at hot tickover instead of specified 10 and I can't understand why.

There is a restrictor valve in the lotus notes vacuum circuit diagram, anyone ever seen this, there is nothing in my vac pipe run from the dizzy to the thermal ignition valve which is the location shown.

That's the only thing I can now say for sure is not there and working.

With the crank at TDC the two cam dots line up so the cams are definately in time with the crank. Good no contact then.

At cold idle full vacuum comes from the manifold and gives 22 degrees of extra advance, so with the timing set to 10 (specified in Lotus notes) you get total advance of 30 degrees at COLD tickover.

When the engine reaches 60 degrees temperature, the Thermal ignition valve switches the vacuum over from maifold to the throttle edge port which only gives very minimal vacuum and advance until the throttle is opened, then you get some advance according to how hard you tread on the gas.

My car will only drive with a setting of 30 degrees at hot tickover, at the recommended 10 it won't drive because its too retarded.

My only hope now is that this restrictor which is missing, provides some sort of continuous vacuum rather than pulses of vacuum from the throttle edge port.

I've borrowed a very expensive SUN model timing light today, and that shows the same as the other two lights, so can't blame the timing lights, 3 say the same.

At hot tickover 40 can be seen in the round flywheel window which means 30 is in line with the timing pointer next to it, that's 30 degrees of advance at tickover, yes?

Can anyone add anything more, suggest something I'm missing??