35 replies to this topic

[gaspen]

Hello

 

Could someony describe me what happens at a rolling road tuning ? How they check/setup ignition timing, mixture ? Is this a "manual" process or is there a machine which measure the values - timing for example ?

 

Let the test car be a 998 with standard dizzy.

 

Thanks

[Steve220]

They'll set base fuelling using a lambda probe and a gas analyser. Timing they can use a light gun to set advance.

[timmy850]

But they’ll check the timing initially and set it to what they expect. They’ll start to increase timing and see if any extra power is added while checking for pre-ignition. It’s a manual process to add/remove timing and then run it up to check.

Then there is specific distributor tuning is your current one isn’t right
The initial timing is set using a timing light
The total timing is set by choosing the advance cam
The timing curve is set by the advance springs

The same concept is used for tuning the mixture, the air fuel ratio (AFR) is read from the exhaust and used to guide the operator to choose a different needle or modify yours

[gaspen]

It looks like a long process 😀

I would like to check my ignition timing for the whole rpm range. It seems i will need a good stroboscope and some time.

[timmy850]

If you get a “dialback” timing light you only need a TDC mark on the flywheel. The timing light has a display and buttons to adjust the timing

For example you set the light at 8 degrees, and line up the TDC mark. This will be 8 degrees at the crank

You can raise the rpm using the idle screw to check the idle over the rpm range

[sonscar]

In my only dyno distributor experience the mechanical advance was locked off and the timing optimised at 500rpm intervals and plotted.The dissy was then put on a machine which spun it and measured the curve with new weights and springs to mirror the curve a longish job.Fuelling and timing are interlinked so it makes exact tuning lengthy.Experience with the car type is probably essential.Just my experience with a twin webber equipped lotus twincam.Steve..

[gaspen]

Both on CSI and 123ignition website I can find the pre-programmed curves. Should I use them to compare for my settings ?

 

I don't have an adjustable strob now but I plan to buy or borrow one.

 

My Mini has a Femsa DF4-58 dizzy but there is no information about it anywhere.

[Spider]

Usually on a Rolling Road, they'll set the mixture up first, then the timing, then they should go back and forth a bit between the two to get it spot on.

 

I have not even heard of a Femsa Distributor, let alone have any data on them.

 

Typically for a factory 998 that has 8.3:1 CR, the dissy curve would be (in engine degrees / revs);-

 

0 - 800 RPM    No Advance

900 RPM         1⁰

1500 RPM        8⁰

2400 RPM        11⁰

4000 RPM        16⁰

 

The Vacuum Advance starts at 6" Hg and finishes at 14" Hg where it gives 16⁰

[gaspen]

Usually on a Rolling Road, they'll set the mixture up first, then the timing, then they should go back and forth a bit between the two to get it spot on.

 

I have not even heard of a Femsa Distributor, let alone have any data on them.

 

Typically for a factory 998 that has 8.3:1 CR, the dissy curve would be (in engine degrees / revs);-

 

0 - 800 RPM    No Advance

900 RPM         1⁰

1500 RPM        8⁰

2400 RPM        11⁰

4000 RPM        16⁰

 

The Vacuum Advance starts at 6" Hg and finishes at 14" Hg where it gives 16⁰

 

Thanks Moke

 

Your data is at CRANK indeed ? They seem low values for me.

 

My Femsa dizzy looks like the one on the link. It is a pretty oldschool stuff. My Mini is a spanish made Authi, so it has spanish parts 

 

 delco encendido femsa df4-58. mini 850-mini van - Buy Spare Parts for cars and motorcycles at todocoleccion - 214939401

 

The red label shows 16°+5°

 

I believe 16° is for the full mechanical advance measured at the dizzy. I checked it today. It gives 32° on crank.

 

5° is a mystery. Could be the vac advance, or the static timing (?)

 

 

[Spider]

214939401_tcimg_09D4E931.jpg

Usually on a Rolling Road, they'll set the mixture up first, then the timing, then they should go back and forth a bit between the two to get it spot on.

 

I have not even heard of a Femsa Distributor, let alone have any data on them.

 

Typically for a factory 998 that has 8.3:1 CR, the dissy curve would be (in engine degrees / revs);-

 

0 - 800 RPM    No Advance

900 RPM         1⁰

1500 RPM        8⁰

2400 RPM        11⁰

4000 RPM        16⁰

 

The Vacuum Advance starts at 6" Hg and finishes at 14" Hg where it gives 16⁰

 

Thanks Moke

 

Your data is at CRANK indeed ? They seem low values for me.

 

My Femsa dizzy looks like the one on the link. It is a pretty oldschool stuff. My Mini is a spanish made Authi, so it has spanish parts 

 

 delco encendido femsa df4-58. mini 850-mini van - Buy Spare Parts for cars and motorcycles at todocoleccion - 214939401

 

The red label shows 16°+5°

 

I believe 16° is for the full mechanical advance measured at the dizzy. I checked it today. It gives 32° on crank.

 

5° is a mystery. Could be the vac advance, or the static timing (?)

 

Hmm,, fair enough, but what was your static / initial setting ?

 

The book isn't clear on it being crank or dissy speeds and advance, but, if those are dissy numbers, that then is 32⁰ (crank) @ 8000 RPM + a static figure of 7⁰, brings us to 39 degrees + if on the cruise, that adds a further 32⁰ brings us to 71⁰ advance. I think at that, it would be popping from the Carb !

 

Cheers for the pic and the link. Delco seemed to have a hand in Femsa.

[gaspen]

Moke, I think you are right with those numbers, sorry    I assume they are the static settings without vac, right ?

 

As I don't have clear data I "kneaded' togehter what I found. Now I set the timing to 10° at 1000 rpm. 

 

I put new springs into the dizzy and I set the dwell to 54° which I checked with a dwell meter (0,4mm clearance at the points) 

 

Dwell was 60° before, but now the car runs better.

[gaspen]

I purchased an adjustable stroboscope, here is what I measured today :

 

Idle 1000rpm / 8° BTDC without vac

 

Vac connected :

 

1500 rpm 12-13°

2000 rpm 29-30°

2500 rpm 34-35°

 

Further increasing the rpm does not change timing, remains 34-35°

[Spider]

I purchased an adjustable stroboscope, here is what I measured today :

 

Idle 1000rpm / 8° BTDC without vac

 

Vac connected :

 

1500 rpm 12-13°

2000 rpm 29-30°

2500 rpm 34-35°

 

Further increasing the rpm does not change timing, remains 34-35°

 

I'd suggest doing the test again, with the Vacuum Advance disconnected (and the carb side plugged up). It's not really possible to distinguish in those numbers how much is from the Mechanical Advance and how much is from the Vacuum Advance.

Also, try to see what your static (initial) timing setting of the distributor is.

Do you know what the specification of your engine is ? I take it that it's standard from the factory (?), but they did come in different compression ratios and with different carbs and also if you can confirm what the cylinder head is.

[gaspen]

I made the test without vac, but forgot to note the numbers and I do not remember  I'll repeat the test today.

 

The engine is a basic 998cc with single HS4. Needle is ABX. During the restoration I re-bored the block for the 1st oversize and installed Nüral dished pistons.

 

It is the original engine from the factory but from the engine number I can't find out the whole spec. The head is a 2A609 for small bores.

 

 number.jpg   52.75K   1 downloads  head.jpg   74.16K   0 downloads

 

 

 

 

[Spider]

Cheers for that. I asked so I could look up what the specs were for a similar Lucas unit.  It is as I guessed earlier;-

 

0 - 800 RPM    No Advance

900 RPM         1⁰

1500 RPM        8⁰

2400 RPM        11⁰

4000 RPM        16⁰

 

I have looked a little deeper in to these numbers to be certain and they are Crankshaft RPMs and Angles.

 

The Vacuum Advance starts at 6" Hg and finishes at 14" Hg where it gives 16⁰

Unless you have a small hand Vacuum Pump and a Vacuum Gauge, it's not really practical to test the Vacuum Advance Unit. As it doesn't really impact on the engine's performance, I wouldn't worry too much about testing it for where it starts and finishes, but that it does provide advance when vacuum is applied and that it doesn't leak. The other RPM related numbers are on the mechanical centrifugal advance unit and these you can test with your dial back strobe. Check them with the Vacuum disconnected.

The centrifugal numbers are actually measured on a decelerating speed, so, start at say 4300 RPM (a higher speed than where it gives full advance) and work back from that.