Crossflow Engines - Unleaded Fuel

[TANGO7]

Does anyone know if crossflow engines supplied by Caterham (as part of a complete kit) were modified to run on unleaded petrol. If so, when is the approximate date from which such engines were supplied?

Does anyone have any experience of using "lead additives" or devices such as a Fuelcat to utilise unleaded petrol in older engines designed to run on leaded petrol? 

[Jonathan Kay]

There's quite a lot in the archives on individual conversions, including who did them and how much it cost, and on what the factory did, with a repeated suggestion that the latter only consisted of resetting the distributor. 

Jonathan

[Golf Juliet Tango]

I an

I don't think so. My Crossflow has an AX block and is in a 1996 Scholarship car, so right at the end of Crossflow supply. I had it modified to accept unleaded at about 55,000 miles.

Prior to that I used leaded four star afterwards unleaded. It's a long time ago but I never used additives.

[Jonathan Kay]

... and on what the factory did, with a repeated suggestion that the latter only consisted of resetting the distributor. 

Weale:

Jonathan

[Bricol]

Quite a number of years ago I simply had hardened inserts fitted to the exhaust seats by a local company - as it was a Vulcan "stage 4" head they were quite big!  Ran with no issues on unleaded with suitable retarding of the distributor.

Currently running the standard head on a xflow in my Dutton trials car on Texaco additives bulk bought a decade ago randomly thrown in the tank in random amounts - doesn't do many miles a year, a few hundred at most, but on the road, and on some classic trials, thats at valve bounce revs as its so low geared.  10 year or more of such abuse and it hasn't required tappets adjusting, so I'm assuming the valves haven't recessed into the head (much) .

[sylvaman]

I also have been running modified crossflows with standard seats for years without problems. Using leaded and Octane boost in one additive ; Castrol valvemaster.  

Did have one head fitted with valve inserts twenty years ago (still have that engine too) amazingly they are fitted by cooling (shrinking them) and pressing in. 

[garybee]

As nobody's jumped on this yet, don't waste money on 'Fuelcat' or similar items (can't even bring myself to refer to them as devices).  There are dozens of these scams around, from mesh bags full of monkey metal to drop into your fuel tank, to inline tubes the fuel passes through.  Aside from being mildly amusing as the adverts explain how magnets will magically make your fuel higher octane they do absolutely nothing.  The 'science' in the adverts bears a remarkable resemblance to that you see in shampoo commercials.  

Obviously if you're one of those guys that wears a copper health bracelet ignore the above and fit the Fuelcat  

[Bricol]

Luckily it's not too amazing - standard engineering practice.  You know what materials you have, you know what temps you have to cope with, so decide on the interference and surface finish needed.  We have a tank of liquid nitrogen here, as well as several ovens for when we want a REALLY good fit.

Which is why your engine person will usually stick a temperature indicator on the head - so when you take it back with an insert banging around on the end of a valve, and swear you never overheated it . . .

[Bricol]

 A mate used to flog those magnets - for use to cure medical ills, to purify water, improve your gas bill and make your car more efficient.

I think I used to upset him when he did the speil about animal collars - and I used to complain my cat keeps getting stuck to my radiators as she walked past . . 

Interestingly though, he used to do a demo with a cigarette lighter.   Spark it up, and get you to hold your hand over the flame at a distance that was comfortable - you could feel the heat, but it wasn't burning.  Then he brought his magnetic bracelet up to the lighter . . the flame grew longer/stronger and rather heated your hand.

[Jonathan Kay]

... to purify water...

I wouldn't put that in the same category. It sounds implausible and I'm not at all convinced but there are some observations that do need explanation.

Jonathan

[HendrixsWhiteStratReturns]

To the OP

 

I have a Xflow (1990 Supersprint) not been modified but I use unleaded with Castrol Valvemaster (have done for 10 years) with no issues whatsoever

[Sooty]

I had standard Supersprint head up to 2006 using Valvemaster additive. No sign of any damage when I replaced the head with a big valve Vulcan head with hardened seats

[Roger King]

Here's a straightforward explanation.

There are two possible problems with unleaded fuel - valve seat wear and potential damage from detonation. The latter is solely an issue with the octane rating of the fuel because initially, unleaded was only available at an octane rating of 95ron compared to the 4* rating of around 98ron. This lower octane could theoretically cause detonation and has nothing whatever to do with the fact that the fuel happens to be unleaded. In any case, superunleaded has now been available for decades if this is an issue for your engine.

The "unleaded" Caterham engine modifications consisted solely of a distributor change, which drastically reduced the ignition timing at full advance; this was done to prevent the above mentioned detonation, but reduced performance because the engine was running sub-optimally  Merely changing to a distributor with a normal advance curve is worth around 10bhp and experience has now shown that this is usually absolutely fine on standard unleaded fuel with an unmodified engine. I think there was originally a sort of paranoia about detonation due to the drop in octane rating between 4* fuel and standard unleaded and, perhaps, enough testing wasn't carried out. You can always run on superunleaded if you want to be bulletproof.

The real issue with unleaded is accelerated exhaust valve seat wear on engines (such as the Crossflow) that do not have hardened exhaust valve seats. Caterham did nothing to address this, I suspect for two reasons.

1) The average Caterham does a much, much, lower mileage than most cars and damage would therefore not appear for some time. A cynic might say that this would push such problems out of the warranty period.

2) The Crossflow is actually fairly OK (not perfect) with unleaded fuel because it breathes reasonably well and therefore there is less build up of heat around the exhaust valve seats. By contrast, the A-series engine (Mini, Marina, etc) suffers from unleaded within a few hundred miles because it doesn't breathe so well and the exhaust valve seats get much hotter.

As commented by several, they have been able to run with just an unleaded additive such as Millers VSP for fairly long periods without damage.

However, the real solution is to fit hardened valve seats to the cylinder head which will provide a permanent answer with no additives required. It is also advisable to make sure that the exhaust valves themselves are suitable for unleaded (most will be these days).

[eric]

In France the 95 is a 10% alcohol when the Super 98 is only 5% . I am not sure this alcohol is good for a crossflow. I personally runs with Total Excellium 98