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PostPosted: Tue Apr 26, 2022 10:49 pm 
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Does anyone have any info or suggestions of what sort of advance curve would be needed to safely use 95 RON E10 fuel in a Sprint with standard compression, cam, and carburation except for K&N filters? It's on BDQ needles, but I'm near halfway to fitting new jets and needles, so I can change them then.

I know I'll lose power with less advance, but I'm down to two places where I can get 99/100 RON fuel locally, and the cheaper one of them ain't that local.

I'm assuming I want an asymmetric spring set. So I'm looking for advice on where to set the start of advance, what advance angle and rpm the knee should be at, and what maximum (stop) advance to have, and what rpm it should get there. I've got a fair selection of springs, including some that are well stronger than the secondary in the 41655 44D4 set. And I should be able to calculate advance rates from their dimensions - I've got the data from the ROM and the specs of the 3 types of spring specs. So I can calibrate the rates I calculate with the dimensions of the symmetric sets and the primary of the 41655 set.

I have a choice of distributors with stops at about 14, 24, and 26 degrees of centrifugal advance at the crankshaft. And I'm in the process of repairing worn bob-weight posts on another. So I could get the stop on that welded up and filed to any reasonable value - 18 crankshaft degrees would be easiest.

Graham

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PostPosted: Thu Apr 28, 2022 11:10 pm 
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I'm 8 miles south of the nearest 99RON and nearly 14 miles north of the next nearest. Neither are even vaguely cheap. It's the price I willingly pay for an octane hungry car. I carry a 2 gallon can of Esso 99 in the boot for emergencies and cycle it through the car when I fill up to keep it fresh. And I now always fill it, no matter what the previous level. It used to be my habit to put £20-30 in when the tank got down to 1/4 full, turned out to be a hard habit to break, but i've done it!

Even the Dolomega's engine, built in late 2000, doesn't like E10, it loses power and does less MPG (about 3 on average)

If I were to be running a Sprint engined Sprint, I'd do exactly the same, why emasculate it by running it on rubbish fuel?

Probably not what you wanted to hear!

Steve

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'73 2 door Toledo with Vauxhall Carlton 2.0 8v engine (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
'72 Triumph 1500FWD in Slate Grey, Now with RWD and Carledo powertrain!

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PostPosted: Fri Apr 29, 2022 10:21 am 
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You right, not what I'm looking for.

But having spent all this time writing a spreadsheet to go from spring dimensions to advance rate - using Marcel Chichak's data on the effect of spring rate to advance rate, with the ROM data for a check -, and having got a significant box of springs here and there (it's sometimes amazing what you can get off eBay for £6.50), I should be able to get sufficiently close to any advance profile I want. So, obviously, I want to set a profile.

The obvious one for me is one to run on that gnat's micturition of 95 RON E10. But I admit I might be being a bit retarded there.

So, while I understand where you are coming from, and have been there, I'm so past it I don't mind the loss of power. I, for one, quite enjoy driving a Herald!

Graham

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The 16v Slant 4 engine is more fun than the 3.5 V8, because you mostly drive it on the upslope of the torque curve.

Factory 1977 TR7 Sprint FHC VVC 697S (Now all of, but still needs putting together)
B&Y 73 Dolomite Sprint UVB 274M (kids!)
1970 Maroon 13/60 Herald Convertable (wife's fun car).


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PostPosted: Fri Apr 29, 2022 11:25 am 
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A std sprint does run perfectly on 95.

I think you don't even have to change the ignition curve. A curve is a result of the induction and the camshaft and that doesn't change.

98 is harder to ignite than 95 but 95e10 is harder to ignite than the 'old' 95 so I guess not much changes.

A std sprint curve and timing will be ok then.

Jeroen

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PostPosted: Fri Apr 29, 2022 12:25 pm 
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Your bigger problem will more likely be the effect the ethanol might have on rubber, plastic and even metal components within the fuel system...and you may only find out what critical parts become affected adversely through trial and error.

Potentially not insurmountable, I understand Brazil's flexi-fuel system has some vehicles running on 100% ethanol rather than our rather meagre, and in my mind pyrrhic, 5 or 10% by volume.


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PostPosted: Fri Apr 29, 2022 1:33 pm 
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If Jeroen is right (not much of an "if" with his experience) then you may be OK, a bit down on power and MPG but if you are willing to accept that......

My concern with building a new, shallower advance curve was to do with the risk of pre ignition, it'd be like setting the static at 4 degrees instead of 10 and driving it like that. It's my experience that the Sprint's "sweet spot" for timing, between pre ignition (too retarded) and pinking (too far advanced) is pretty narrow. I've even experienced badly coked up examples that exhibit both symptoms simultaneously!

There is a 3rd factor beside induction and cam to consider and that is compression ratio. The higher the ratio, the higher the octane rating needs to be avoid those nasties of pinking and running on. When you think that most Sprint heads have by now experienced a skim or two which raises the compression ratio further.........

When I think of all this work and research and planning and faffing about to make the car run WORSE and give WORSE gas mileage I sort of wonder "Why would you?" Especially when you are limiting yourself to a standard design, basically stone age, mechanical distributor. A megajolt and EDIS would be a lot easier, more reliable and is programmable to any curve you fancy. That's if you don't want to go the whole hog and opt for the lovely but very expensive 123 dizzy.

But you are not me, it's your car and if it keeps you happy, sincerely, good luck to you! You may have the last laugh, If Vlad the Impaler nukes us, your car will keep going after the EMP and mine won't!

Steve

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'73 2 door Toledo with Vauxhall Carlton 2.0 8v engine (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
'72 Triumph 1500FWD in Slate Grey, Now with RWD and Carledo powertrain!

Maverick Triumph, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
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PostPosted: Fri Apr 29, 2022 1:34 pm 
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Quote:
A std sprint does run perfectly on 95.

I think you don't even have to change the ignition curve. A curve is a result of the induction and the camshaft and that doesn't change.

Jeroen
I take it you mean the ignition centrifugal advance curve that is required "is a result of the induction and the camshaft".

But then, if they don't change, why did BL change the centrifugal advance curves by changing the spring rates and advance stop values so dramatically over the production run? I am aware of the needle changes between the carb sets, AUD 545, AUD 661, AUD 680, AUD 663, and FZX 1257, but aren't sure which goes with what advance curve.

It has been suggested that the change from the curve in the 41402 to that in the 41458 was because of the loss of 5 Star at about the time of launch, and that seemed logical. But I see that change was to reduce the spring rates (keeping it a symmetric pair with no knee in either curve), and to increase the stop limit, which increased the advance at all levels, and I thought it would need to be retarded for lower octane. I have run a Sprint engine (in a TR7 with s tube exhaust manifold) on 2 Star, and it did pink. But I have no idea which version of the 44D4 distributor was in it, how worn that was, or where the static timing was set. Fairly sure that the needles would have been BCM - since I already knew that BDQ didn't stand for Bloody Damn Quick.

BL then switched to the 41655 with asymmetric springs and a primary stronger than the symmetric pair in either the 41402 or the 41458. That reduced the advance over much of the mid-range of rpms. They also put in what Martin Jay (the Distributor Doctor) described as "a huge" secondary spring, and increased the stop limit again. I reckon, if the new springs I got from Martin are right (and I'm sure they will be), that F.O.B. secondary won't let the advance reach that limit before the revs reach bloodline at 6500rpm. It won't even let it rise above the advance from a 41402 till 2600 rpm (camshaft) or above that from a 41458 till about 3000rpm. In which case, I wonder if the increase in limit had any real value unless it let Lucas supply parts that were common to some other car - many 44D4 subcomponents fit the 45D too, and they tend to larger advance values.

So I'm well confused about why the changes to the advance curves, and which is better, best, or needs improving in the case of 95 RON.


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PostPosted: Fri Apr 29, 2022 3:11 pm 
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Quote:
My concern with building a new, shallower advance curve was to do with the risk of pre ignition, it'd be like setting the static at 4 degrees instead of 10 and driving it like that. It's my experience that the Sprint's "sweet spot" for timing, between pre ignition (too retarded) and pinking (too far advanced) is pretty narrow. I've even experienced badly coked up examples that exhibit both symptoms simultaneously!
In the Wikipedia entry on pre-ignition, two of the cause are given as "Ignition timing too far advanced" and "Too much air/too little fuel (octane) to withstand pressures (too much air causes too much pressure for the octane to handle, too little fuel reduces the octane to handle the pressurized air)".

It also says for pinking that it can be prevented by "retarding ignition timing" and "the use of a fuel with high octane rating, which increases the combustion temperature of the fuel and reduces the proclivity to detonate.

And that goes with what I understood: that there's no real issue, beyond power loss, to retarding the ignition timing.

I'll go and do some more research, as even I don't see Wikipedia as definitive. But this one is news to me.

But my thoughts were to keep the static timing at about 10 degrees and use a 41655 with standard 12 degree (24 at crank) stop and std 41655 primary spring, but with a shorter secondary spring. That secondary spring would be set to come in at about 2500 rpm (13 degrees crank), not the 2900-3000 (18 degrees) as std. I was also considering an even stronger secondary to hold back on the advance at higher revs. I've a selection of springs that are bigger even than the 41655 secondary (the std 41655 set should give, roughly, 1.6 degrees per 1000 rpm once the secondary comes tight, if Marcel Chichak's and the 1980 ROM data are right). Some of the more monstrous ones I have should give near half that advance rate.

I was thinking about those settings because the only problem I've seen in the last 35 years daily driving something with a Sprint engine - one at over 200bhp; IIRC 155 at rears* - is pinking with too much advance or too low an octane petrol, mostly at about 2500 rpm with big throttle openings. The first time the timing had slipped to about 20 degrees static (that engine had issues from about day 7 after I got it fitted, cos it had been round Oliver's Mount too many times), and I took it up over Bishopdale between Kettlewell and Aysgarth - not exactly like Hard Knot, but some bear steep slopes. The second time, just fast driving between Brough and York on 2 Star. Both times it cost me a set of pistons and then a set of big ends cos I didn't know better than to put new shells on the crank without taking it out to regrind it. Yes, I should have known better the second time, but I thought that the Sprint, with the timing set at 10 degrees BTDC, was okay on 2 Star and I still didn't know that re-shelling an un-reground crank could lead to it failing soon after.

But it wasn't okay on 2-Star at all, even though the timing was set right - it's been a habit of mine since the Bishopdale incident to keep an eye on it.

It might be that with a 41402 and it's fairly mild centrifugal advance stop, it would be okay. But seeing that both the 41458s I have give much more than the 18 degrees (crank) advance they should - near 30 in one case - that may be a systemic problem with that version of the 44D4. And that Sprint could have had that issue - so maybe as much as 40 degrees of advance at about 3000 rpm, even on a 10 degree static. But it's a sodding expensive mistake to make with pistons the price they are!

So, if there is no advice to be got on what max advances I want at what rpm values, then I'll stick with 98-99 RON Supers as long as I can. But I have been told often enough that the dissy rebuilders can modify the curve to make it safe to run on ordinary unleaded (before E10, perhaps before E5). But, obviously, I can't ask someone like Martin how to do that: it's his living.

So, I've worked to be able to set the advance rates from the physical dimensions of the springs - wire diameter, coil diameter, coil count, with estimates for Young's Modulus and Poisson ratio for music wire. And checked the results against the specs for the springs and the advance data from the ROM. And that's why I came here.

Graham

*And I admit that's a Dave Bogg Standard measurement.


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PostPosted: Fri Apr 29, 2022 6:46 pm 
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Wise not to trust Wikipedia, I think they got their info from an old Haynes manual. When they SHOULD have consulted an old mechanic! They've got pre ignition confused with detonation (the posh name for pinking) But i've often heard this repeated, usually from similar uninformed and unprofessional sources and it makes no sense, if pinking is the result of too much advance, how can "running on" (pre ignition) have the same cause?

I'm not really surprised people are still getting it wrong, pinking and running on are largely things of the past, modern computer control makes them effectively impossible. I grew up and learned my craft when EVERY car on the road was susceptible to either/both by bad tuning and/or excessive coking in the combustion chambers.

But don't take my word for it, you have a running car, set it to 2 degrees BTDC static, run it up till nice and warm and switch it off. But have it in gear with your foot on the brake, ready to stall it out when you do!

Steve

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'73 2 door Toledo with Vauxhall Carlton 2.0 8v engine (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
'72 Triumph 1500FWD in Slate Grey, Now with RWD and Carledo powertrain!

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PostPosted: Fri Apr 29, 2022 8:15 pm 
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Well, Wikipedia do have two separate articles and make it clear that pre-ignition and pinking are different things.

I did have a Sprint that had the bad habit of running on after switch off. It was bad enough that, sometimes, it would spin backwards for a bit - I'm not sure it actually ran backwards, as such, but it turned that way. And that's not great considering the water-pump design and the LH threaded setscrew holding the impeller down.

But I spoke with the guy who had built that engine and used the car for himself for a couple of years. He said he'd had the same problem with it, and the fix was to retard the ignition from 10 to about 8 degrees. No problems after that. I may have lost a little power as a result, but I don't think I noticed.

And, even when it ran on, it never showed any sign of damaging the pistons; unlike too much advance or too low an octane definitely will.

So I'm convinced I want to limit the advance to run on 95 RON. I just don't know how much by. But there's no way I'm going anywhere near 2 degrees of static.

So, I think the relevant question is, what happens where static is set 10 degrees, and the centrifugal advance is stopped from doing anything?

Graham


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PostPosted: Fri Apr 29, 2022 9:15 pm 
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A bit of research suggests the problem I had that broke the pistons was actually "detonation induced pre-ignition". But it also seems that the way to avoid that is with a rich fuel mix and retarded ignition.

Graham


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PostPosted: Fri Apr 29, 2022 10:36 pm 
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Quote:
A bit of research suggests the problem I had that broke the pistons was actually "detonation induced pre-ignition". But it also seems that the way to avoid that is with a rich fuel mix and retarded ignition.

Graham
There's no doubt that pinking is a lot more destructive than running on, melting and holing pistons being the worst case effects! Though you can make a good case for extra lean mixture being a more major contributor to melting pistons. The SAAB 9-3 Turbo that donated me so many valuable parts, ended up in my yard because it had melted a piston purely from a malfunctioning injector in that cylinder. At least running on is not AS major problem on most engines! The Sprint's design quirks makes running on less desirable than most. And yes, running on does indeed mean the engine turns backwards (anticlockwise) for however long it goes on for. BUt I ALWAYS advance an engine that runs on and it's always worked unless the advance makes it pink, in which case I pull the head and decoke it!

I picked 2 degrees static to make sure it would run on and prove my point, not as a serious suggestion for regular running! The engine will still RUN if timed after TDC but the side effects are not much fun to see, like the exhaust manifold glowing cherry red!

A helpful (or more helpful) suggestion is that, if you fear allowing the car to run on like this or even the possibility thereof, there is a cure at hand, half inspired, half bodge! Made by Ford in the 80s to stop rampant running on in later MKII Escorts with the 1300 Kent Crossflow engine, you could buy (or sometimes get free under warranty) a thing called an "anti diesel valve" ("dieseling" is the American name for running on) Typical Ford, don't fix the design error, just mask the symptoms! What it did was to put this valve into the inlet manifold with a solenoid that held it closed when the ignition was on, when you switched off the valve dropped open, spoiling manifold vacuum to atmosphere. About all I can say about it, is that it worked in all but the most extreme cases. I have one lying around here somewhere, which I took off a 1500HL Dolomite I scrapped a couple of years ago. I used to fit loads back in the day, was a lot cheaper than a decoke for hard up customers with 70s and 80s bangers (which are, of course, now hugely valuable collectors pieces)

Steve

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'73 2 door Toledo with Vauxhall Carlton 2.0 8v engine (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
'72 Triumph 1500FWD in Slate Grey, Now with RWD and Carledo powertrain!

Maverick Triumph, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
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PostPosted: Sat Apr 30, 2022 11:19 am 
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It is only the risk of piston damage that I'm really worried about. And I still believe that having the timing over advanced is much more likely to lead to damage to the engine than having it a bit retarded would be. Also, I understand that lower octane fuel demands less advance or risks that same damage. So, if I'm pushed down the path of using 95 RON E10 without octane boost (and that's such a can of worms they should paint the cans vermilion), I would need a distributor with an advance curve of a lower profile.

Maybe I would need to back the static off a bit as well; maybe I wouldn't. Jeroen's assertion that the Sprint can be run on 95 RON without adjustment suggests there's no need to change the static. But without knowing which version or versions of the 44D4 that relates to, there's still a risk that some of them give more advance than is safe - I bet on a worn 41458 being most likely to cause trouble. And that's especially a concern as the ROM allows up to 4 degrees variation in advance at any given rpm; and I've got one that has the stop worn or modified to give 6 degrees more advance, yet is otherwise is in usable condition.*

I just wish I could get some numbers from someone who's had that mod for 95 RON done, or had it done for them in having a 44D4 reconditioned.

Given I can get from spring sizes to advance rate, I can work from just the wire thickness, outer turn diameter, and number of turns on the springs in the distributor. And if the springs are asymmetric - like the 41655 44D4 set, but not 41402 and 41458 -, and so there's a knee in the advance curve, then any estimate of where the longer secondary spring comes tight, e.g. as a fraction of the distance moved towards the stop from static (and the stop value stamped on the beak below the cam) would be a big help.

*The bob-weight posts are a bit worn and there's some marking of the baseplate beneath the weights where they catch it cos they're floppy. But there were no obvious noises from the distributor in use. I'm looking at fixes for that post problem - either replace the posts, replace the baseplate with the posts from a good/better 45D (it's splined on the main shaft), or sleeve the bottoms of the posts and drill the holes in the bob-weights bigger.

Graham


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PostPosted: Sat Apr 30, 2022 5:26 pm 
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In my book pre-ignition and detonation and pinking are all the same and caused by the same. Pre-ignition is the self combustion of the mixture before the spark arrives. So actuallly detonation.

Running on is caused by a too retarded timing and that's not the actual cause. When the engine is running on, the ignition is already switched off so the actual timing doesn't matter during running on. When you turn the dizzy to more advance at idle the revs rise most of the time a bit and when you retard the revs drop. When advanced you close the trottle valves a bit to drop the revs to idle area again and too retarded you have to open the throttle valves more to idle. This too open causes the engine to suck in enough mixture where the hot engine can run on a few seconds when switched off.

Running on is an engine running when the igntion is off, the same symptoms at detonation, an cumbustion without a spark on the plug. The rattling noise you hear is both combustion without a spark. you have to find a way there's no combustible mixture getting into the engine when switching off. That's a harder to ignite fuel so a higher octane or less mixture getting in when switching off so the throttle valves as closed as possible of like Steve said an airvalve only sucking air in. Some Triumphs had this airvalve also. USA spec TR6 with the dual vacuum advance/retard systems. At idle these have the timing ATDC to be able to idle on a very enviromental friendly mixture but being that retarded at idle these do alway's run on when such a valve isn't there.

So both the same but at different timing settings.

Jeroen

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