XFlow and Super Unleaded

[cskip]

Can a Crossflow that is setup for standard unleaded be run safely on Super Unleaded? Is there a possiblity of damage to the engine? Will performance be improved if not setup for Super?

 

I have a '94 1600 Crossflow that has not had the unleaded conversion.

 

Thanks,

 

Clive.

[oilyhands]

Super unleaded has a higher RON rating so it will be more resistant to knock at higher combustion pressures, if your engine runs happily on regular unleaded then its pretty sure to be OK on super, higher octane fuels generally have a marginally lower calorific value and tend to burn marginally more slowly so pinking is less likely than with regular unleaded. Performance is unlikely to improved unless the engine is currently pinking or detonating , if it were you would know.

 

Oily

 

Edited by - oilyhands on 6 Sep 2001 12:50:35

[Jam Mad]

mine runs on super unleaded all the time.. but oops... actually now i think about it, i don't think it's had the conversion...

 

so ignore me !

 

wink.gif

[Tony]

Clive

You say that your car is 'set up for unleaded' but then say it has not had the conversion (?). Anyhow, I am presuming you have not had hardened valve seats fitted, in which case the higher combustion temperature of unleaded fuel (and lack of lead which actually cools and lubricates the valves as well as raising the octane level of the petrol) MAY cause damage to the head or/and valves. You may not be able to detect that damage is occurring until it's too late.

If in doubt (and this whole area is hallmarked by dodgy and differing information from both government and oil companies) why not have hardened valve seats fitted. I had my x/flow head done as part of a larger project by Chris Wheeler/Roger King at the 7 Workshop, but if I remember rightly, the basic conversion of the head for unleaded could be done for as little as £250 (maybe less) if you are prepared to dismantle and refit yourself.

Why not give them a call? Then you can drive with confidence into the unleaded future!!

Tony

[oilyhands]

Going rate for your local machine shop to fit 4 hardened seat inserts and remake the seats will be around £100-120. Valve seat recession can be a problem if you are running plain iron seats, keep you eye on the tappet clearances, if they start to close up, then you could have a problem. If you do a realtively low mileage then it may not affect you for a good while.

 

If you want to know the full affect of lead and lead halides and their role in combustion and valve and seat protection and exactly how lead molecules prevent premature propagation of the flame front I have a paper on it kicking around somewhere, it gives the definitive whys and wherefores.

 

Oily

[cskip]

Tony, Sorry I wasn't very clear. The engine has been setup on the Rolling road using Unleaded, but has not had the seats replaced.

 

The previous owner of my car (from New) was told by Caterham that the Engine would run on unleaded without any problems. I have been told this is not necessarily true. Something to do with South African built engines. Can anyone clarify?

 

Also does anyone know of a good place to have the unleaded conversion done in the Southampton/Bournemouth Area. Don't fancy going all the way to James Whiting/Roger King. Plus I will be tempted to part with even more money and have a 1800cc fire breathing monster!

 

Clive.

 

Edited by - cskip on 6 Sep 2001 16:27:51

[Roger King]

There is a number of issues with converting a Caterhem Crossflow to unleaded.

 

Basic fitting of unleaded exhaust seats and recutting would generally be around £100. Inlet seats are often slightly distorted when the exhaust inserts are fitted, so these may need recutting too.

 

If you have a Supersprint or any other head that has been gasflowed you will need to allow for the cost of reworking the new inserts to match the port shape.

 

You may well need to change the exhaust valves as well unless they are unleaded compatible.

 

There may be an issue of valve/guide wear. Frankly, the Supersprint often suffers from this anyway, irrespective of fuel. Some of the valves used in these engines really should have had a bronze guide, so material imcompatibility is to blame here.

 

You need to allow for the cost of a new set of stem seals.

 

It is important that after the inserts have been fitted and cut, you have the same installed height for the valve springs. This is especially important for a tuned engine with a high lift cam.

 

Caterham engines in standard form will need about 1 in 4 tankfuls of leaded fuel to be safe. The only changes that seem to have been made for unleaded fuel were drastically to alter the advance curve (which I don't understand, because every Caterham spec engine we've tested so far on a 'leaded' advance curve has been fine with 95 octane unleaded - note that this implies no guarantee that any individual engine will be OK) and possibly to drop the compression ratio a little.

 

 

 

Edited by - roger king on 6 Sep 2001 17:13:07

[cskip]

All,

 

Thanks for the info.

 

I can feel a winter project coming over me. If the head is off why not have some work done! (What did I say about being tempted!)

 

Clive.

[eric]

Hi clive

 

For Caterham, ok for unleaded means that you have an Aldon 103 FXYS UL(for 95 unleaded) but nothing made on your head (seats and Guides)

If you use 97 or 98 unleaded you can have more( a little) performance by using a distributor Aldon 103FXYS (not UL) which curve is better for this ron.

 

Concerning the valve seat recession, don't panic many people tell us now, if you car run for many year on leaded, it is self protected. In another hand, many specialist can explain you that

X-flow is not design for unleaded, so...

 

Mine is 1600 sprint with A2 cam and a burton stage 2 unleaded head. They send me the head ready to fit, and the car runs better

than before.

I use an aldon 103 FXYS distributor with 98 super unleaded

10000 miles/year, AX block standard piston....

 

I live in Marseille, in France, no Caterham specialists there

and it was easy, so for you...

 

regards

[eric]

hi

 

Some specialists advise fuel catalysts, it is easy to fit, not expnsive and may be work well.

I saw an advertise in low flying : juno sportscars

 

If it can help

 

Regards

[John Whyman]

 

I considered having the head on my 1990 supersprint done, and then considered the cost and the alternative. I went for the alternative. I use Millers VSP fuel additive with standard unleaded all the time, and when I can get it, which I can easily in Somerset (See Bayford Thrust web site for participating garages)use genuine leaded 4*. I make no adjustments to timing or anything, and it all works just fine. (You do notice a slight performance improvement with the 4*, but its marginal).

 

 

 

Happy Motoring. thumbsup.gif C7 WJW.

[Psycho man]

Just want to iron out one thing - LRP 4* - where does this fit in between unleaded & the real 4* - Good, bad, indifferent or a waste of time?

[Robster]

I am a bit concerned to see people suggesting fuel catalysts. Tetra Ethyl Lead IS NOT MADE BY LEAD BALLS IN THE PETROL, as fitted in these catalysts. Lead does not dissolve in the fuel, so will not deposit on the valve seats, and I have heard of no evidence suggesting that these catalysts work...the chemistry part of the argument is just wrong!