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Discussion Starter #1
Hi,
I'm building a 2L liter 512 motor in original form, 9:1 pistons, original cams 10548.
I have to choise the distributor.
I have a new bosch distributor 229 with vacuum advance.
I'd like to lock the vacuum advance plate so to have only the mechanical advance.
Can anybody tell me the curve that I would get with this change?
Thanks
 

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Discussion Starter #2
I believe nobody has tried this change.
do you think it is possible to open a tread where to share ideas for the creation of a test bench for distributors?
for the reading of the advance degrees I thought to use a strobostropic gun, I do not know how to manage the rotation control
 

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I have measured distributors by running them on engines and collecting data from a good tachometer and an adjustable timing light. It is simple if you have a helper to hold it at a certain rpm while you read the timing light.

Maybe you have no replies because no one knows what a Bosch 229 is.
 

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What would be the reason for deleting vacuum advance on a standard engine?
Vacuum advance helps on partial load (lean mixture) and has no effect on full throttle.

I would use your new 0231170229 as intended, it's set for your standard 2L Nord.
 

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I have fully mapped ignition on my GTV6 and I tried adding advance to correspond to vacuum advance and I could not find any effect. In theory additional advance will help leaner mixtures burn but I run AFR's of 15 to 16 at part throttle and the additional advance was of no benefit. I now run a simple advance curve, like a distributor with no vacuum advance and the engine runs very well throughout the range of RPM and load.
 

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Sorry for the delay. I first had to find the curves, that were in text form only, and then draw the graphs.
The information comes from Petrol Engines Workshop manual #3469B dated 09/84.
 

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Thanks for posting the curves, I had not seen them before.
The mechanical advance curve is slow. Performance engines usually have all of the advance in by 4000 rpm and some earlier. I would not choose this distributor for a motor that is intended to make good mid range torque.
 

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Discussion Starter #9
Hi, thanks for information.
My original distributor was 0231110045, I think his curve is more aggressive of 229.
I don't know the conditions of the old distributor.
I''m trying to find somebody with a distributor tester but it's not easy.
 

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Hello, this topic's interesting to me as well. I've got a 1750 GTV with the 045 dizzie (non vac advance), and while the car goes well, I don't think the fuel mileage is good. it's only used for long trips and only makes about 30 mpg. We also have a couple of 1700 Alfasud boxer Alfas, with twin 40mm downdraught carbs, similar HP, but these cars do 35 mpg or more on trips, even though they're driven harder than the GTV. All the engines seem in pretty good condition. The GTV's carbs are well-tuned I reckon.
I know that vac adv can improve fuel mileage a lot, and I'd like to try a vac adv dizzie on the GTV.
I've got a spare 229 Bosch lying around, off an 1800 Alfetta, but as noted above the centrifugal advance curve on these is not much good for performance. Can anyone suggest a decent alternative that was used on some other Alfa with vac advance?
Thanks all,
Graham H, NZ
 

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Are your gallons US or imperial. 30 mpg from a GTV with Webers in the US is outstanding and 24 is not bad. I would be surprised if vacuum advance changed it much but carburetor jetting can.
 

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The 60s Alfa cams, particularly the 10548, were more performance oriented than economy. RJ has done some interesting development on cams involving reduced overlap, with increased lift, the result being improved horsepower with improved low AND high RPM torque, with improved fuel economy due to reduced waste during overlap.

However, 30 MPG is excellent for the Nord, regardless of whether it’s Imperial or US gallons.

I’d leave well enough alone and put the time and money into something else.
 

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Thanks Ed, and thanks Don. (Don, are we the same Don P from the Sidedraught Central group conversation?)
Interesting to hear what you both say about GTV fuel consumption, with 30 mpg regarded as quite OK. (Note- we do have 10548 cams.)
My figs are with Imp galls, so with US galls they'd be about 20% worse I believe. But to counter that, I just now went to the car (it's stored off-site at present) and actually checked my log book, and found that in fact I was getting about 35 miles per Imp gall on recent trips, not the 30-ish I had in my mind. That would be close to the 30 miles per US gall that's regarded as OK.

So maybe things aren't so bad at all !!! Nonetheless, if I had a quick and easy way to add vac adv without losing the good adv curve of my current dizzy, I'd love to do it. In my mind, there's plenty of practical evidence to be found that this often gives 15-20% better cruise-mileage. But since I don't do a lot of miles, I'd be doing that really just for the hell of it, so as Don says, if it cost any significant amount there are better things to spend money on. If there's no suitable Alfa vac-adv dizzy that I could pick up cheaply from a parts-car, then I might still look at modifying the curve of the spare 229 unit I've got, to look more like the non-vac 045. Thanks Ed for the curves you've published for us, and thanks JK for an example of what I'd need to do.

Also referring to Don's posting, a while ago I did indeed have an email discussion with RJ about his cam-upgrade options for the GTV. Came to the conclusion that he certainly does have some very tempting and very suitable offerings, but the pretty solid cost (especially with shipping to NZ) was rather more than I could justify for our purposes. Pity!

Thanks again all,
Graham H (1750 GTV, Alfasud x3, 156 TS)
 

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Crikey, I can't leave this alone, although I should be doing something more useful! Have just been looking at the curves Ed's provided for the 229 (vacuum-type) dizzy and seems to me that it could be made rather like the favoured 045 curve if we simply altered it by limiting its max adv to whatever it's reached at the 045's max-point which is 4,200rpm, then setting our initial advance so the 4,200 value is whatever max adv we want (which for me would be the same as Alfa specified for the 1750 with an 045 dizzie). I.e. we're simply offsetting the raw 229 curve upwards and cutting it off early, just as seen in the JK book where he modifies an 006 dizzie.
That'd give a dual-slope curve, nicely steepened to begin with, with same end-point (degrees and revs) as the 045, and without needing a silly amount of initial advance. Nothing to do to make this mod except change an end-stop (if the 229's got one).
Worth a shot?
Best regards,
Graham H
 

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Yep, me again - more queries...... After a lot of reading heaps of posts on Alfabb, and finding lots of adv curves there, and drawing more curves on the graph paper, I do reckon (as above) that I could have the 229 dizzie giving say 37 deg max adv at around 4200, which seems to be a good starting point for a standard GTV from what I've read, and similar to the favoured Bosch 045 maximum. However to reach this I'd need to set initial adv at around 13 degrees, which is getting on the high side I expect. Might be OK - I think Ed uses this much OK.

As a result of that high initial setting, the advance curve from idle rpm to the 4200 max is not as steep as the favoured 045 - can anyone suggest if that's a big deal or not?

Interestingly, I noted that above 2,000 rpm the slope of the 229 curve is much the same as the "JK" curve - well well, maybe we're on to a good thing!
Does anyone have an opinion on whether that rather gentle slope is a good fit for a standard road car?

Of course, I could just go ahead and refurbish the scruffy old 229, fit it, time it, and do lots of road testing - but if more experienced people can suggest whether it's worth the effort or not, I could save a lot of wasted effort.

Keen to hear all opinions,
Many thanks,
Graham H
 

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The slope is not necessarily a bad thing. Compare the advance at 2000, 3000, 4000. If you have significantly more than the JK or the Bosch 045 then you should be alert to detonation. It is easy to hear at those rpms. If you have significantly less then you may have inferior throttle response and/or higher fuel consumption. Most importantly you do not want a steep curve between 800 and 1200 rpm or you will have problems getting a stable idle. The Shankle curve is a good (bad) example of that.
 

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Thanks Ed. Well, given your comment above, the plot has thickened........

Looking at the curves to make your suggested comparisons, and getting myself in a tangle, I concluded that I first really needed to know where to place each curve on the graph, in terms of its intended initial advance setting in actual use in a GTV. (Since I guess that's the only placement that we know is safe from detonation, and I guess is thus a useful point of comparison.)

So I placed the JK curve where he designed it for, 12 deg initial giving 34 max (at 4,000 revs).
And I placed the 045 curve at about 6 deg initial, to give the 39 max specified in my 1750 owner's handbook).
And there's also an 006 curve which JK (on this forum and in his book) recommends as a good all-round curve for 2L GTV, and I placed that at 4 initial to give a 34 max, as per JK's book note on how it was used.
(Of all these curves, the 045 is the most advanced one, at any RPM above abt 800.)

Anyway - with these three curves positioned on the page, now I can offset my raw (un-advanced) 229 dizzie curve up and down the graph until it sits at whatever max advance I need, and at what revs, and compare with the above presumably known safe curves.

And I found - to stay below all the other curves, I find I can obtain anything up to 38 max out of the 229 curve, although not until 5,000 revs (where the 229 dizzie maxes out). This would be done with an init adv of 9 degs (it flat-lines at 9 degs from 0-1000 rpm).

Alternatively, if it's the case that the 38 max should be reached at some lower revs, say 4200 (sim to where JK and 045 max out), then the 229 raw curve would need to be offset upwards to about 15 degs initial timing. This would force it up to 5 degs more adv at 2,000 than the highest of the other curves (the 045), reducing to 2-1/2 more at 3,000.

So, to see what can be done with this 229 dizzy, I'd be keen to know what people reckon is the RPM by which we should reach max adv, on a std 1750 Euro GTV. There seem to be a massive range of settings in use for standard GTVs - apparently max adv comes at 4200 for the 045 dizzie, but not until 5,400 for the 006 ! How much does it matter?

Regarding this 229 ex-Alfetta dizzie, I noticed that the 229 curve (the raw distributor curve) is actually very much the same as that of the Bosch 006, one which I've seen recommended (as above). Only real difference is that the 229 has a smaller total span, maxing out at 5000 whereas the 006 keeps on going up, at the same slope.
So the 229 could be a good dizzie for me, depending on the RPM by which I need to reach max adv.

Thanks again,
GH
 

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When I compare curves I normalize them for max advance because that is the most important number. The 045 will not be more advanced than the JK "D" curve when you compare them that way. If the D curve gives too much initial advance for your desired max advance then it is unsuitable for your motor. The 006 curve is slow compared to them and in my experience it gives inferior performance compared with 045.

I would shoot for getting all of the advance in by 4000 rpm.
 

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Ah yes, I see that that's right (advance of 045 vs JK), looking at the normalised curves for around 36 degs - the curves are very very similar at all points above about 1,000rpm. And I can be pretty sure that the 045 is OK to use even more advanced than that, assuming the pulley M mark on my GTV (Mk II) is indeed located for the 37-40 degs max adv that my handbook says the car should have. That's the mark I've set to and I know that car never knocks with our driving, not that we're ones to labour the engine on purpose.

Given that, I think I could in fact safely try the 229 dizzie, as when it's offset to give 36-37 by around 4,200 (sim to the 045), its curve would never be more than 3 degs above the 045 curve, and even that would be only around the 2,000 rpm area, and we'd never be labouring our beloved engine in that region. (I'll check that I've drawn my graphs correctly, mind you.....)

We may well find that the flatter slope of the 229 above 2,000 revs dulls the engine, but then, it's not quite as flat as the 006 which some writers (clearly not yourself, though!) reckon is a good curve, so who knows how it would perform, in our particular car....... I guess there are as many opinions as there are writers!

I might as well try it, since I've got it lying around doing nothing, and if it's significantly different from the existing 045 it shouldn't take too long to feel if it's any good or flat as a pancake. At least we now believe it's safe to try and we won't be driving to Detonation City.

In any case, whether I end up using the 045 or the 229, do you agree that I might as well try different max advance settings, to optimise for our particular car? In the most simplistic way, I'd propose to do the foot-to-the-floor detonation-test, in all areas of the rev range, in a suitable high-ish gear in each case. And settle for the max adv that passes these tests (less a safety margin). Sound reasonable, for a rough and ready job?

Oh, and lastly, on the RPM for the max advance knee, roger re your 4,000 recommendation. Since this is supposed to be a rough-and-ready exercise, I won't be looking at modding my 045 unit to that figure, but if it's working to spec it should already be maxing out around 4,200 which isn't too far off the mark.

Thanks for all the help,
and more comments appreciated,
GH
 
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