4000 rpm limit 123 distributor

[Grant]

Hi Tom

sorry I've just re read your last post so I will pop the 8 degrees back via the soft where ,
but Im still not sure what to do with the vacuum as this seems to be the problem.
any ideas ?

[christopher storey]

Grant ; the vacuum advance is additional to mech advance and is completely independent of it . It arises only at part throttle , and you should be able to see the effect of this with a timing light, in that when the engine is running under no load at say 2000 rpm there should be perhaps 14 to 18 degs of advance on top of the 25 degs you would expect of total advance ie something in excess of 40 degs in total. A sharp opening and return of the throttle should see the vac element disppear to nothing and then return .

The purpose of vac advance is to provide better part-throttle response and to maximise fuel economy under light load conditions

[Tom W]

That’s good progress.

I think I’m about to repeat what Christopher’s said, but I’ll post it anyway.

The vacuum isn’t a problem, it’s supposed to do what it’s doing, but with it connected, it makes it measuring just the mechanical advance difficult. You can’t put enough load on the engine when revving it on the drive to get the vacuum low enough to not affect the advance.

If the software says you have 0 degrees at idle, and the timing light shows 0 degrees at idle, don’t move the distributor anymore.

Now you need to translate the advance curve from the workshop manual into the 123 software. This is basically Christopher’s curve on your graph.

You can do the same with the vacuum advance curve too. This one is quoted in the workshop manual as distributor degrees too, so you’ll need to convert it to crankshaft degrees (multiply the advance values by 2). You’ll probably need to convert the pressure values from inches of mercury to KPa.

[Grant]

Hi Tom and Christopher thank you so much for your patients ,

but obviously Im being a bit thick here I thought the problem was on the graph I drew it was going up dangerously high ? above the factory curve to ( Red actual to black factory) 38 degrees . but that is now ok ?



I think Steve's post of the factory curve, seems to have kpa on it underneath so I guess I can use those figures?
in the left column kpa right degrees?

thank you

Grant.

[Tom W]

Hi Grant,

I think Steve’s curve is probably a safe starting point.

What you had before was the blue line, but raised up by 8 degrees. So you still had too much advance at higher revs. What you should have, at the crank, is Christopher’s black line.

The green and red lines are a combination of mechanical and vacuum advance, so should now be disregarded. We’re only interested in mechanical advance at this stage.

The important point is that when measured at idle, with the vacuum disconnected, what the timing light shows is identical to what the 123 software and the 123 curve shows.

The 123 software only shows how much advance beyond the known trigger point (the LED) the 123 is applying. If that trigger point isn’t at TDC, you get an error equal in magnitude to the difference between TDC and where the trigger point actually is.

[Grant]

Hi Tom

ok I think I get it , thank you .

I will try a apply Steve 's curve not sure about the figures in the bottom graph I will see if I can copy them straight in as they appear to be KP .

Much appreciated.
I will definitely owe you a drink should we ever be able to meet up with people again !

Grant

[Tom W]

Good stuff. Let us know how you get on when you go for a test run.

[Grant]

Good Morning Tom, Christopher, Steve and everybody else!

I think we are there !

I applied the factory curve and just taken her out and its amazing , she drives so well almost like a modern car she runs well , sounds different and pulls like a train!
she does go up to around 40 + degrees at times with the vacuum but as Christopher said a blip of the throttle it disappears and comes back so Im assuming it is the right sort of advance ! :-)
It was pulling up to and over 4000 rpm and seemed better than before, but the road conditions and screaming girlfriend holding the iPad (for the dashboard app) did not allow me to go much further!
I will clarify she is at TDC exactly as soon as I can, but I think Im very close.
I also may need to increase the tick over a little but i will wait and see on that.

So just incase anyone else like me with no knowledge reads this in the future it seems the Bluetooth 123 ignition wants to be set at TDC and then apply the factory curve on the app,( page one of this topic that is very easy)

thank you all again

Grant.

ps does anyone know what size socket I need for the damper to set Tdc.?

[Gfhug]

1 5/16 socket. Well done Grant, pleased to see you are succeeding.

Geoff

[Tom W]

Well done!

If you take it back on the rolling road, it will be interesting to see what difference it’s made.

[Grant]

Hi Geoff /Tom

Thanks Geoff I will try and find one ,
Hi Tom yes it would but to be honest it was a good hour away and the guy was so grumpy( and the money of course )
I don’t think I will bother but I’m so very happy with the result, thanks again I could not of done it with out yours and the others help .


Grant

[Gfhug]

and screaming girlfriend holding the iPad (for the dashboard app) did not allow me to go much further!
I will clarify she is at TDC exactly as soon as I can

Time for a new girlfriend

For finding tdc (of the engine not your girlfriend!) you may find this helpful:
viewtopic.php?f=3&t=5859&view=previous

Geoff

[Tom W]

Not paying for more rolling road time is understandable. It’s never found it’s that worthwhile paying someone to work on a car if they’re not interested in doing the work, or are going to constantly moan about what they’ve been asked to do.

Pleased you’ve got it working better now.

I wouldn’t rule out trying a different rolling road in the future though. A good operator should be able to fine tune the engine to perfect that very last bit. It’s just not possible to get 100% on the road without investing heavily in data logging equipment.

[Grant]

Hi Geoff,

Very good but she has been very understanding lately ! :-)
I will give that a look thank you

Tom
Yes it’s a shame because they are a really well know classic racing company,
And because I only really got to see she was about 180 bhp but that was only at 4000 revs so I will not know what she is capable of at 5000 which I think would be as far as I wanted to push her
At the moment I’m just happy to have a really nice running car but I know what you mean when you get used to it , I will want to squeeze a little more I’m sure. :-)

With your 123 Do you get to see your stuff on the computer? Does regularly go up in to the 40 degree mark like mine ?
You sound like you really fine tune yours, do you race it ?

Grant

[Tom W]

Hi Grant,

No, I don’t race my car. I might try a track day at some point, but I doubt I have the ability or budget to get into racing.

The 123 in my car doesn’t connect to a laptop, so I can’t monitor what it’s doing whilst I’m driving. It has 16 pre-programmed curves. All I can do is look up the advance curve in the manual, and add that to the static advance the distributor is set to, and hope that’s what it’s actually giving me at a particular rev point. The problem with the pre-programmes one is there are only 16 curves to pick from, and most aren’t suitable. The only other thing I can change is the static advance, and with it the total advance, much like a conventional distributor. The tune version you have is much better. Mine came with the car, and was bought before the tune one was introduced, but if I were buying now, I’d buy the tune version.

I wouldn’t worry about the 40 degrees your seeing, it’s due to a combination of mechanical and vacuum advance. It only goes that high under light load and low throttle openings, and is supposed to. It helps with fuel economy and throttle response. So long as you’re not at 40 degrees when you have your foot to the floor under hard acceleration, you should be ok.

As my car is non standard, most of the tuning I do is trying to get it to work as well as a standard car would, particularly with part throttle drivability, and trundling around town. There’s no factory settings to copy with Webers. The dyno graphs I’ve got are in the rolling road thread, both from the proper rolling road, and from the road dyno box I bought, along with the data from many other people.

viewtopic.php?f=4&t=14449

You’ll get more power if you rev up to 5000rpm. Your torque curve was level right up until the point the engine refused to rev, it doesn’t look like it naturally tailed off. Power will keep climbing with more revs until the rate at which the torque drops off is faster than the rate at which the revs rise.

[Grant]

Hi Tom

It’s a shame that you can’t plug a usb or something into yours and read what it’s doing but to be honest as long as they drive well who cares.
Well it does seem like mine is driving ok now so fingers crossed I will not have to touch it too much , which was the reason I went 123 in the first place, looks like it’s going to be a nice weekend so I will definitely be out putting her through her paces this weekend !

Thanks again

Catch you soon

Grant

[Gfhug]

It is very frustrating that the Jag version of the 123 with its 16 curves only has one that is close to the standard dizzy and even that needs retarding at idle by a few degrees or it’ll be too advanced at high revs All other curves are far more aggressive.

Geoff

[Grant]

Hi Geoff ,

It’s funny you say that I was out again in mine today , and she is still getting very high , well over 40 degrees nearly 50 at times and even when I blipped the throttle it did not disappear ,
And I’m running the jag factory curve so I don’t understand it.
Could it be the carbs , are sucking or blowing too much ?
Does anybody know if I can reduce the amount of vacuum that is being exerted ?
And it still not pulling well over 4000rpm.
I'm going to pull the plugs tomorrow to see if she it running lean.and get a socket and confirm she is at tdc.
Strange because she is running fine apart from that ,

Grant

[Tom W]

Have you programmed the factory vacuum advance curve into the 123 software, as well as the mechanical advance curve?

[Grant]

Hi Tom ,
Yes I did , just as Steve’s graph , I will try it with no vacuum just to check that side,


And maybe look at how to reduce the amount the vacuum is doing. Any suggestions great fully received .

Cheers

Grant