12 replies to this topic

['Chop']

Hi all,
Fitted an accuspark electronic dizzy, leads, plugs and sports coil a little while ago ( bought from them as a complete kit)
Set up the static timing, adjusted the advance/ retardation on the clamp, adjusted the carb, but couldn't get the dwell angle exactly right....
The problem is that while its good up to 55mph, above that, so reasonably high revs, the engine just lacks any more. I know the engine well, having used it in various minis over the years. Its almost like the vacuum advance curve is wrong on this dizzy. The kit was bought for a 998. Its only stage 1 tuned, so nothing fancy.
Completely coincidentally the vacuum pipe came off the other day, and it seemed to run so much better, without the misfiring or juddering.
Has anyone else had this? Is it safe to just disconnect the pipe?
Cheers, Andy.

[Tamworthbay]

I asked them about advance curves a while back for a project of mine. Their own dizzy has a 'one size fits all' curve and is the same for all their A series listings, so 850-1275 gets the same. It could just be that.

[KernowCooper]

It will be a curve for a 1275 and thats not correct for a 998, the vacuum advance wont be affecting the cars performance under power as the vacuum advance make no difference under wide open throttle

[Spider]

I asked them about advance curves a while back for a project of mine. Their own dizzy has a 'one size fits all' curve and is the same for all their A series listings, so 850-1275 gets the same. It could just be that.

 

I haven't actually looked at the distributors on offer from Accuspark - until your post here prompted me.

 

It does look like that is the sad situation.

 

I can categorically say that 'one size' (or one curve) definitely does not fit all. Serious engine damage ca result.

 

I noticed a while back one of our local suppliers also selling new Lcus Distributors. They advertising said pretty much the same thing, 'suits all Mini Engines for 850 to 1275'. I worte to them to ask what the curve was, their reply was that they didn't know! Just to clarify on this point, I have no idea if these are the same ones that Accuspark sell.

[Tamworthbay]

I asked them about advance curves a while back for a project of mine. Their own dizzy has a 'one size fits all' curve and is the same for all their A series listings, so 850-1275 gets the same. It could just be that.

 
I haven't actually looked at the distributors on offer from Accuspark - until your post here prompted me.
 
It does look like that is the sad situation.
 
I can categorically say that 'one size' (or one curve) definitely does not fit all. Serious engine damage ca result.
 
I noticed a while back one of our local suppliers also selling new Lcus Distributors. They advertising said pretty much the same thing, 'suits all Mini Engines for 850 to 1275'. I worte to them to ask what the curve was, their reply was that they didn't know! Just to clarify on this point, I have no idea if these are the same ones that Accuspark sell.

that's the problem, for them it comes down to stock levels I suppose (how many 850 ones would they sell). Personally I would use the old dizzy body and fit a conversion unit (which is what I did). It seems to be an industry standard at the moment sadly. I do know people who have run them for many miles and I think it's fair to say that the chance of engine damage by running a. 1275 curve in a 998 is so small as to be irrelevant if not non existant, but why would you run a sub optimal system when you don't need to?

['Chop']

It will be a curve for a 1275 and thats not correct for a 998, the vacuum advance wont be affecting the cars performance under power as the vacuum advance make no difference under wide open throttle

So it's likely to be another problem then?
Its only above a certain speed and the car just feels like its holding back and sounds/ feels a little misfirey. Could it be a fuelling problem then? I set it up using the old colour tune technique. If not, what's the best degree setting for a 1984 998 A+ and at what revs should the timing be set up as? The manual wasn't very comprehensive.

[KernowCooper]

A 998 cc Mini with engine no 99Hxxxxxxx with a distributor no 41882 will have 16degs of advance at 2000rpm

A 1275 cc Mini with engine no 12HCxxxxx with a distributor no 41858 will have 22.9deg of advance at 2000rpm

 

the longer stroke engine needs a bit more advance in its curve than the smaller engine

 

so you can see that 1 size does not fit all and a 1275 advance curve is to aggressive in a 998 standard engine, generally the large bore engines are not as fussy on curves as the smaller 998s. Putting a 1275 one size fits all distributor into the 1098 would be fatal as that engine is very fussy on advance and detonation would kill it.

 

If I had a 998 standard engine I'd not be putting one of the one distributor does all in it.

 

Re your timing question thats a difficult one if your not using the correct distributor, 8degs at 1000rpm with the vacuum off and plugged, but as soon as you take the revs up its over advancing, send it to H&H Ignitions and give them the full spec of your engine and they will recurve for £30-40 on

 

Tel. 01384 261500

 

Or speak to AC here on the Forum hes done a few for our members

 

Footnote

The reason why your 998 ran better with the vac pipe of is that on a light throttle the vacuum advance was adding more degs of advance to the already over advanced curve of the 1275 distributor, making a total  mess of the engines requirements

Edited by KernowCooper, 22 December 2014 - 09:51 PM.

[Spider]

This is not specifically about the Distributors that Accu-spark are selling.

 

Sorry if this is going a little OT, but I do feel it's relevant to the Topic in general.

 

This is an Exhaust Valve I pulled from the head of an 1100 engine about a year ago

 

 

 

 

 

 

It kinda looks like it's been oxy cut.  It also cracked the head.

 

The owner is a reasonably sedate driver in that while he would keep up with surrounding traffic, he wasn't one for ringing each and every gear out either.

 

The distributor fitted was for a 998 engine.

 

When the Advance Curve of what should be fitted is compared to what was fitted, the reason for the badly burnt valve starts to become clearer

 

 

( a shot of the disc from my dissy tester)

 

 

The RPMs and Degrees Advanced in that Graph ^ are at the distributor, so you need to multiply them by 2 for what's going on at the crank.

 

Looking at the graph, what is clear is that right around 'the normal cruising zone' from 2000  to about 4000 RPMs, the required Ignition timing was quite retarded. Driving with it in this state causes very hot gases to go through the exhaust as the fuel is still burning (or not long finished) as the exhaust valve starts to open, causing the burning of the valve. If it were from a lean mixture, then the valve would have a white appearance.

 

Note too that this particular distributor, as fitted, doesn't have a Vacuum Advance either, which in this case, could have helped.

 

This shows why the correct advance curve is important and just one example of serious engine damage.

 

Just coming to the Lucas Copies that seem to be popping up on ebay and other places these days, most of these don't seem to have a stated Advance Curve. I've been able to test around 30 of these now and no 2 have been the same. I've seen some very wild figures from these as well, in one case 

 

 

Now, remember that is in Distributor Degrees, so that is a total of 40 degrees at the crank + about 6 degrees static, way too much for any A Series Engine I know of!

 

Yes, it was fitted to an engine and it only survived around 2500 km before it too was damaged, in this case, the owner was fitting a Primary Gear Seal about every 2nd day, after a quick check to show him that his fresh engine had some serious blow-by, it was pulled down. We found that the ring lands on the pistons were hammered down, pinching the rings.

 

From the tests I've done on these copies, there doesn't seem to be any rhyme or reason to them, they are just a lucky dip.

 

So, I'd suggest when buying any of these new distributors, asking what the Advance Curve is. If they simply say, "Suits from 850 to 1275 Engines", then I'd suggest leaving it right where it is.

Edited by Moke Spider, 16 September 2015 - 08:00 PM.

[KernowCooper]

My thoughts entirely. Boy its a lucky dip alright from your tests ranging from severely retarded to severe detonation, so there is very poor quality control, I doubt there even tested just reach in a bin and screw them together.

 

This has got to be a major issue and your post needs to be made a sticky in the engine FAQs, once people have caught up with the post we'll move it over for reference

 

 

Best to get yours rebuilt without doubt or risk your engine

Edited by KernowCooper, 22 December 2014 - 11:36 PM.

[Shifty]

I fitted one to my old 1098 clubby and it ran fine.

 

I know the curve won;t be right but it's usually not enough to cause a problem like you describe, they will run ok, just not perfect.

 

Are you tuning by ear or to a timing light?

[KernowCooper]

Your were one of the few who happened to get a good one shifty, Keith Calver mentioned that the 1275 curve will cause a 1098 engine to detonate to destruction, worrying to see they vary so much.

[Spider]

 

I know the curve won;t be right but it's usually not enough to cause a problem like you describe, they will run ok, just not perfect.

 

 

 

 

Fair enough in your case, but how does one know when buying?

 

 

.Boy its a lucky dip alright

 

 

Maybe I'm paranoid, but I prefer to be safe than sorry.

 

I will just add that f your engine compression is low enough (or your engine is just really tired), you could get away with something that is quite wrong, only the engine could go from running rather under-powered (from having LC) to being really gutless (due to timing being way off the mark)

[racingbob]

this info gets you thinking about dizzys

 

I bought a new dizzy the ones that minispares sell for the 1990 cooper

 

for my mg metro engine about stage 2

 

it went on the dyno at slark but I wonder if its ok

 

car runs ok but is it giving the best