Hello,

earlier I tried to bring my distributor advance mechanism to specs but without proper equipment it's such a pain to do... so I settled to 'something close'.

Now I am talking to a specialist, who is suggesting instead of tuning to specs to use different curve, which will advance timing earlier and to bigger extent.

Anyone played with it? Without changing anything else(intake, filter, fuel map...) does it make sense to use custom advance curve?


Thank you.

P.S. I have AJ6 3.6 engine.

 

The 3.6L does not have distributor advance. Ignition timing is controlled electronically by the ECU, There will be a timing wheel on the front of the engine.

The only way to adjust the ignition curve will be re-programming the ECU or replacing the ECU with an aftermarket.

 

what he said!!.

i use a standalone ECU, SDS,, warron is going to use an MS unit , both slightly different but kinda do the same thing!

mine is early type fuel adjustment only.

for ignition timing i was able to use an old sun machine for advance curve in distributor , and for my V12 i'm using a simple generic chevy curve.

been 20 odd yrs works good enough ,and gets the job done, small tweaking as i felt required.

but you need a distributor on the engine!

 

Mine does, here is how it looks...

 

It would be nice if someone here in NJ had one of those machines with box of spare springs next to it :-)

 

A couple of ideas. Having an old Sun to bench test and customize the advance curve
is old tech, but still works as long as the distributor has adjustable internal guts!!


In olden days slots were adjusted, shortened r lengthened. Springs were changed.
At times relying on SOP only. "seat of the pants". Or drag strip times.


I've never tried it, none to play with at the moment. But, using a Smart strobe timing light to read off degrees and a tach to plot them.


Off to the Jaguar and the store....


Carl

 

i have altered and changed distributor advance curves since i was around 19/21 yrs old.

it is easy if you just try it, and with a good timing light you can get it close enough for your needs, try to simplfy it, go for a basic curve!

make sure all things inside are clean and movable! sometimes you may add weight with a little spot of weld, or you may reduce weight by grinding off some material.
would help if you have a spare dist. to take apart and grind a different weight cam curve!

any race car supply store can get you a spring kit(summit, jegs,etc), i think mine cost $10. bucks, a GM kit with fits all stuff.

Cadjag gonna do it,hehe,LOL

 

If he had a car or truck with an old tech distributor, yup!!!


Carl

 

I do have a strobe, and played with my distributor. It is a PITA to replace a spring and then plot resulting curve on the car with the strobe.

Since I am talking to someone with equipment to do changes, my question now is more like 'what curve would you suggest?' .

For example, would anyone do a change like that:

rpm...advance.per...faster
........manual........advance
6400.....22...........30
5200.....21...........30
3500....19.5..........30
2000.....18...........22
1300.....16...........17
1100.....14...........14
<900.....13...........13

(this is dynamic advance only, with vacuum disconnected)

 

Rough goal.


As much and as fast as the advance can be plugged in sans detonation on lots of throttle.


Carl

 

At times messing with critters isn't easy. But, persistence and success is cathartic !!


Way back when, my early flat head Ford V8's ate points. A very sophisticated dual point unit down and under. A Mallory design.


The "book" described a way to set gap and dwell with a rule . Confusing and did not seem to work.


But, one way or another, I found that if IU brought mine in the back door to the local Mercury dealer's shop, a kid friendly tech would set them up on the Sun machine!!!


Carl

 

.

1st what fuel octane do you intend to use?

then drive the car without vacuum advance connected, try different throttle loads to see if you can get light detonation? if not manually advance timing, till it does,make a note of tach rpm, that is where you want to take out some advance ,maybe 2/3* retard!

an NA engine wont hurt anything for just a few seconds,its sustained top speed that can do harm!

most detonation occurs at peak torque usually in mid rpm range.

on that proposed curve you show, i would go for about 25* at 2500rpm full load, then up to 30*, and if all seems ok try after peak torque, go for 34* after 5000 rpm.

it is a pretty generic curve tho!

some thing that interfers is auto trans keep shifting down throwing off your records, i wonder if kickdown can be shut off temperarly?

anyway it'll keep you busy for a while, BUT you will learn a lot!

OOPS, just read you lucky you got a manual transmission, that should make adjustments more accurate!.. using 4th gear.

 

Thank you for suggestions.

Car is designed for regular gas, and I intend to use it (though I am guilty of feeding if plus here and there).

I was hoping that for this engine someone already did all the work on a dyno stand and maps are simply available :-)

 

not many people doing engine mods on that engine!

and i doubt there is a dyno ignition curve already done.

 

No one that I'm aware of in the states does any remapping of the ECU. You'd likely have to talk with Roger Bywater and ship the ECU to England, but probably no point in doing that unless you opened the intake/exhaust.

As to the advance, I played with mine a few years ago. I think the manual calls for 18 degrees for federal spec cars and 21 degrees for euro spec. I doubt there's any benefit to changing it. Check your repair manual.

 

Thank you,

I was not planning to go as far as remapping ecu. Just wanted to hear opinion about changing ignition advance curve from stock to more 'advanced' one.

Right now I do hear pinging at higher rpms when engine is under load (but frankly I do not know what exactly my current curve is, I just know that it is 18 degrees at 2000 rpm and that I am using 'medium' springs from GM distributor). I am planning to take distributor to a shop that will tune it to a curve, and debating if i should tune it to stock curve or not.

Thanks again.