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thunderbolt
United Kingdom
11 Posts |
 Posted - 19/03/2007 : 10:09:29
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I have been using my PA so little, that it seemed Ok to keep using unleaded, but I am now getting to think that both it and My British bikes would be happier if I made some effort to recreate something more like four star.
I have a friend with vintage Austins who adds paraffin to the unleaded( I don't know the quantities). And others who use off the shelf additives.
Could the panel please advise on the best fuel or recipe for a PA that is infrequently used. 
1935 PA 4 seater |
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Rodney Collins
United Kingdom
424 Posts |
Posted - 19/03/2007 : 13:55:41
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Rob,try TETRA BOOST, It ain't cheap but it works, and if you do not use the car to often it won't cost a lot.
Rodney |
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George Eagle
United Kingdom
3246 Posts |
Posted - 19/03/2007 : 20:01:07
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I have been using Castrol Valvemaster plus, which has an octane boost, in my supercharged NB without any problems.
George
NA0960 |
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Bob Stringfield
United Kingdom
854 Posts |
Posted - 19/03/2007 : 20:58:14
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The P-type was designed to use pre- WW2 petrol which had no - or minimal - lead, this feature arriving post-war after succesful use in piston-engined aircraft. A lightly-used P should run well without trouble on unleaded. The pre-war additives were benzene or alcohol.
Some old-car owners add a small quantity of paraffin ( Mr Brown, that grasping Scot, would regard this as illegal so vote for him - not. ) to lower the present-day high octane rating better to suit softly-tuned sidevalvers. A 1916 3 1/2 hp Sunbeam which I owned would, in common with all of those used in France, run well on paraffin if warmed up on petrol, to which end they were fitted with a petrol/paraffin two-compartment tank. |
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Old Grey M
United Kingdom
52 Posts |
Posted - 20/03/2007 : 10:19:36
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Leaded fuel is still available at several outlets. Have a look at bayford.co.uk for list of locations. Whatever science tells us, we have a hunch that the M runs cooler on it than unleaded, with or without additives. Be warned it is expensive but if you're not doing a high mileage does it matter?
Mike |
Edited by - Old Grey M on 20/03/2007 10:20:13 |
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Terry Andrews
United Kingdom
546 Posts |
Posted - 21/03/2007 : 11:12:34
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I agree with the comments of Robert Camp. Both our PA and TF 1500 ran hot with out any changes to timing etc with unleaded fuel. The addition of paraffin does cool the engine down this was particularly noticeable with the TF. I was advised to add paraffin by Colin Tieche and it worked in cooling the engine down without changing any settings. I later changed both engines cylinder heads to run on Lead-free but on inspection the valves and things were fine.
The changing to harden valve seats does not change this situation at all. However, by adding water wetter etc the P type runs cooler without adding paraffin. The TF is on SORN at present so cannot comment as I have not tried water wetter in it.
When I used additives, Valvemaster mainly, it did not make the engine run cooler but was just protecting the valve seats. Even this could be debatable as old cylinder heads have ôlead memoryö and I understand that this takes time to wear off once one uses lead free petrol.
Once using Lead-free only, you may find it necessary to experiment with the timing as I found everything was better if I retarded the ignition a little. With these old cars you need to adjust them to suit what is available now and not stick solely to the settings stated manuals etc.
One final thing, Lead-free seems to go ôstaleö very quickly. So needs to have ôfreshö fuel added to the tank after a winter lay up. More that 3 months old and the cars can be difficult to start and the fuel and carburettor etc get ôgummyö. So best use the car little and often!!!
Terry
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Bob Stringfield
United Kingdom
854 Posts |
Posted - 21/03/2007 : 18:48:00
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Terry, it is Champ as in 'The greatest' rather than Camp as in 'A row of tents'.
Certainly the risk of modifying a cylinder-head to provide lead-free seats should not be taken until it is unavoidable |
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Terry Andrews
United Kingdom
546 Posts |
Posted - 22/03/2007 : 10:12:03
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[quote]Originally posted by Bob Stringfield
Terry, it is Champ as in 'The greatest' rather than Camp as in 'A row of tents'.
Bob, Sorry about the spelling. I have had a operation on my right hand which has gone wrong so to look up people's real mame is a click too far!...... I may also need a new pair of glasses.....Sorry again...... Grumpy Old Man |
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Gordon
United Kingdom
693 Posts |
Posted - 25/03/2008 : 10:11:26
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I note from the Feb issue of the MGOCC Bulletin that there is an explanation on modern fuel type and engine design. The suggestion is that modern high compresion high running temperature engines are designed to burn fuel relatively slowly since fuel burn rate depends on cr and temperature. The suggestion is that our lower compression engines need a faster fuel burn rate. If you burn too slowly it reduces efficiency and with standard timing the fuel does not have time to fully combust during the power stroke. This, it is suggested, results in more heat being deposited in the engine and cooling system. Adding keresene makes the fuel burn faster and cooler in the low compression engine.
Any experts out there care to comment and does anyone know how much keresene to add? I gather that you can get a permit from HM Customs to do this as it is legal for pre 1940 engines!
Gordon |
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David Allison
United Kingdom
665 Posts |
Posted - 25/03/2008 : 11:33:33
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Gents
I run the NA on either standard unleaded - backed of the ignition by 5 degrees or on Tesco 99 superplus.
Neither effects the cooling although the standard unleaded does make it knock if you try to use too much advance.
The radiator on the NA is very large so probably takes the overheating into account and it could do with running a little hotter anyway (I blank the rad most of the year round).
The car has always run on castor oil and this is supplied as an upper cylinder lubricant via the blower - through the carb on the over-run.
The NA has always had issues with ignition advance and pre-ignition - the state of tune in the 1970's contributed to this.
The car now has about 12 lbs of boost and a 7:1 compression - I spent a lot of time last summer getting the car to run cleanly on superplus unleaded only to find very little advantage over the standard unleadeds.
I do use fuel as a coolant - the car runs rich and this extra fuel is used to cool the combustion chambers.
I run about 3 % CO - but have cooling issues and tuning issues below this figure - the only problem is fuel consumtion which is around 20 mpg - if you enjoy driving it the fuel economy drops still further to around 10 mpg at the very worst (this is normally twisty roads with lots of slow corners and showing off areas).
My boss has a Triumph ST Sprint bike and introduced me to the Tesco 99 octane - it transformed his bikes performance and that of my colleagues Honda CBR 600RR.
I tried it in the NA and the car runs much cleaner and noticably more power without any flat spots or pre-ignition.
My brother in law (Tim Metcalfe) introduced me to a 115 octane racing fuel he uses - and the car loved it.
Unfortunately the rate at which the car uses said fuel and the cost is more than my wallet can stand.
The best octane boosters are the Aldon and Putolene products (most good retailers) - these are Lead Substitute rather than oil based additives.
Based on Toluene these fules can raise standard unleaded fuel up to 100 octane allowing the ignition to run at full advance.
You can go green and convert the car to run on bio-ethanol - although the fuel useage will be much greater (upto 30% more fuel used)and the alcohol can rot the fuel pump.
there are more and more retailers offering bio-fuel and it is certainly worth consideration.
Unblown cars (and some blown ones) run happily on the kerosene and parrafin based lead substitues although for racing and hard road use you could ultimately run into overwarm piston crowns and pre-ignition.
All of that said - in comparison to the awfull fuels available pre-war - we have nothing to worry about!
Hope this helps
Regards David
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ags
United Kingdom
275 Posts |
Posted - 25/03/2008 : 20:14:53
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Hi all,
I do support David A. on the poor quality of Thirties fuels. About twelve hours before his posting I was writing myself on a related subject, compression ratios. At intervals I have looked into fuel quality, and so I quote myself;
"My best guess about the low value in Blower ( ie of recommended compression ratio ), which does reflect Thirties' experience, is that it was the result of running on Thirties' fuels. My reading around this subject suggests that all road fuels then were in the 80 octane bracket, possibly even the low 80s, but certainly much lower than is expected today."
I was also interested to see David's figure for CO, presumably at idle, which by my calculations equates to an air/fuel ratio of 13.4:1. This is not excessively rich, but I should guess that at higher throttle openings his mixture did go richer ie towards more CO. His figures also confirm that though our cars have many good points, fuel economy is not one of them. The PB always turned in 28 mpg, more or less regardless of type of use, and war time correspondence in the motoring journals is illuminating, 40 mpg being out of reach for this under 1 litre engine!
Oh well, keep paying the bills,
Andrew Smith MMM571 |
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Bob Stringfield
United Kingdom
854 Posts |
Posted - 25/03/2008 : 21:26:15
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The RAF officer driving a MMM car is almost a clich? in films about WW2 flying.
PA 0603 in its original, blown, form was certainly in the possession of an RAF owner during 1939 - 1943. Aviation spirit of the period might easily (accidentally?) have found its way into the tank to help out with the rationing and at 100 octane or so would have suited the engine. What lead content did that have?
I have heard it said that a total ban on leaded petrol would result in the end of historic piston-engine flying.
The MMM car was designed to run on un-leaded but, like most cars of the period, suffered from valve-seat recession, later alleviated by 'leaded'.
I stick a gallon or so of this in the tank in every so often, having a localish garage which sells it, and compression remains good so far. |
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