fuel additive

[seniorchristo]

Having recently purchased an '67 Elan SE with what I believe is a modified engine, I am wondering what fuel additive I should use. I don't know what modifications were made or what type of valve seats I have. Any suggestions?
Thanks,
Chris

[Elanconvert]

hello chris and welcome to the world of elan!
I bought my S4 last year .....fitted with sprint spec engine, and the PO used and recommended Tetraboost......which I tried along with others...
however, i have found that using Shell Nitro [99 octane] [with castrol valvemaster just in case] gives even and reliable running...........all you can ask for really.....
I'm sure you will find plenty of other opinions on here!!! [have a look at the archives on the subject!]

fred

[AHM]

Standard unleaded (Premium 95 RON) without any additive.

From memory the concern over valve seat recession due to the removal of lead was for high mileage use and cast iron heads. The minimal recession that you will notice on the elan is adjusted out with tappet shims.

recently I've gone from not fussed about ethanol in fuel to undecided, but nothing that any additive will cure.

[elansprint]

Chris I have hardened seats but use Castro valvemaster for the octane boost
Ian

[seniorchristo]

Three responses and three different suggestions. I appreciate them all but I like the one using just standard unleaded fuel. It is cheaper and easier . Seriously, if I don't have to worry about valve seats is 93 octane unleaded sufficient? I haven't heard any detonation even under load at low revs in 4th gear. I guess the issue is since I don't know the compression ratio or other changes it's difficult to predict octane requirements. Thanks all. l
Regards,
Chris

[StressCraxx]

Super unleaded, no "mouse milk" additives. The octane is what is important, so you don't have detonation. If your engine has higher compression pistons, put it on the chassis dyno and run it to check for detonation and optimum timing on the fuel you use. You won't hear detonation when driving.

The lead additive (TEL) was for soft cast iron seats and added some octane. All Lotus Twinks have steel valve seats, plenty hard for unleaded fuel.

I used to work in an oil refinery, including the Octane Lab and the Fuel Blender unit.

[rgh0]

You don't need to worry about the valve seats. Most engines by now have new seats which will be harder and even if not replaced the original seats where hard enough and have no problems with unleaded especially given the mileage most Elans are driven these days.

Unless the engine was built with a compression ratio significantly above 10.5:1 you should be OK just on straight 93 Octane USA pump fuel. Test it on that with full throttle accelerations from low revs and if no pinging your OK. If your getting pinging look at what your ignition advance curve is doing it may just need a little retarding or it may need the advance springs replacing if its advancing to fast.

If you have to excessively retard the ignition versus the normal curve to stop the pinging then you need to try Octane booster additive.or delve deeper into the engine to understand what modification may have been made.

cheers
Rohan

[seniorchristo]

All good advice. I think I'm good to go!!
Later,
Chris

[AHM]

Don't be afraid of using the standard advance setting at 2500rpm - If you are too cautious it is a bit flat below 2000rpm.

I'm using 95 RON supermarket fuel with a 40953 distributor (most advance of the standard ones) with -2 degrees from standard for c-type pistons, low octane fuel, good luck, day of the week etc. No pinking and goes like a rocket up to 6000 rpm

[Elanconvert]

my take on it is........the twink was designed to run on 5 star leaded, so try to get as near to that as poss......
all the additives I tried [including tetraboost, millers cvl, etc.] left a brown deposit on the plugs with resultant eventual misfire......I'm sure standard unleaded is ok though!!

fred

[AHM]

For anyone interested in additives there is a good page here
http://www.fbhvc.co.uk/legislation-and- ... formation/

Does anyone have any detail about the characteristics and composition of modern Fuel?
Apparently modern fuels burn slower which may explain why they tolerate more ignition advance - I can't find anything to verify this.

And as far as I can ascertain ethanol boosts the octane rating but reduces the calorific value. So you will get knock resistance but not necessarily a proportionate increase in mpg.

I would never have dreamt of putting 2 Star in, which got me thinking so I looked-up the old octane ratings. 4 Star was 98 and 2 Star only 92 so current 95 isn't as bad as I imagined it to be.

My take is that we don't need the lead, and the octane isn't worth the ? / $ spent.

Current fuel composition must be quite different to the 1960's

[TroonSprint]

Beware of octane ratings, they differ depending on where you are. There is a Wikipedia article here http://en.wikipedia.org/wiki/Octane_rating but a succinct precis of the difference between the USA and the UK is given in this forum response from Pistonheads.

"In the UK, Octane on fuels is quoted as ?RON? or ?Research Octane Number.? Without going into great detail as far as methodology, there is another common measurement system called ?MON? or ?Motor Octane Number.? MON typically yields a numerical value 10 points lower than RON from the same sample of fuel.

The Octane number quoted on the pump (PON or Pump Octane Number) in the USA and Canada is an average of RON & MON (RON + MON / 2.) So if you are comparing UK & USA fuel, you typically need to add 5-6 points to a USA Octane number to get the EU equivalent."

Mike

[RogerFrench]

"Standard Unleaded" over here (USA) is 87 octane, typically. That's about 91, UK equivalent.
Just be careful whose advice you heed, unwittingly it mightn't be the best.
I run mine, and the TC Europa, on Premium.

[AHM]

Roger,

I've edited my post above - When unleaded was introduced here it was called premium but was less good than 'normal' 4-star - never could understand that.

We have:
BS EN228 'Premium Unleaded' 95 RON
BS EN7800 'Super unleaded' minimum 97 RON can be 97/98/99/100 depending on marketing
BS 4040 '4-Star' 98 RON

They can be called anyting from unleaded to millennium / momentum / V-power Nitro+ so I called it standard to try and avoid the confusion!

se here for Tesco fuel specs. - well done Tesco!
http://www.tescopfs.com/our-fuel/testing_results
and here for Shell
http://events.imeche.org/docs/default-s ... f?sfvrsn=2

[Hawksfield]

Chris

I have been running my 1971 big valve on normal pump petrol for about seven years now since I stopped using Castrol additives.
I have found no problems with pre ignition and still use standard ignition settings maybe around 11 degrees
QED rebuilt my head around 1993 so I have had a long assessment of running on pump petrol with and without additives.
I am rather surprised with the running of the big valve engine as my first +2 I had in 1975, I had to run it on the five star which was available then, as anything less caused pre ignition, Just goes to show the difference in petrol today.

John