LRP or Premium?

[Shant Fabricatorian]

I've been using LRP for about three months, so that's about 5 tankfuls, but I read an article recently which said that it doesn't have to conform to the same standards as other petrols, and so the active components aren't added to the quantity they should be.

Does running the car on premium (super) unleaded cause valve seat recession (VSR)? If so, should I be using an additive?

Otherwise, the car's running just beautifully, although it sounds like a tractor when it's cold now that we're well into the depths of winter.

[Hamish]

There's been quite a lot of posting on this subject, and views vary around the globe quite considerably.... :wink: My advice is to run top quality unleaded with an octane booster/lead additive combined (such as Millers VSP 8) ) but you'll probably see/get reponses suggesting otherwise - the above combinbation worked very well on my VX coupe and a couple of fellow VX owners now also run this combination with similar pleasure :twisted:

[Shant Fabricatorian]

Cheers for that.

Went back and had a look at previous posts, seems like premium is perfectly respectable for normal driving though an additive is useful if you're of nervous disposition...

[peter_coupe]

I was watching DWTV last night and Shell have developed 100 octane fuel....

I'm not sure when it will be for sale, but I will be really keen to try it.
Test calim that new fuel gives 5% more torque,, uuuuuuuuuuuuuuuuuuuuuuuhhmm more torque.

Is that fuel for sale in UK yet?

Ciao Peter

[Hamish]

Sounds like Optimax - although don't remember the specific octane rating off the top of my head :wink:

[Duncan]

Optimax is claimed to be 98.6 RON. But apparently it "goes ff", so it'll turn into ordinary superunleaded if you leave it too long in your tank.
I thought the Japanese already had 100RON fuel? That's why lots of Japanese cars have knock sensors, so you can set them up for 100 RON, and if you put the ordinary stuff in the electronics retards the timing for you.
And what RON is race fuel? Higher than Optimax for certain...
Cheers
Duncan

[peter_coupe]

F1 race fuel used to be 107 RON, but I think they limited F1 fuel to 100 now, not sure,
There where several scandals long time ago, some companies where supplying race fuel over 110ron.

Peter

[Wallace]

Call me a pedantic s***t - but I've read several bits about high octane petrol doing b-all for engine power UNLESS it's been set up to suit. And this can be "basic" such as ignition timing to something a lot more complicated like compression ratio, carb jetting etc etc.
I suppose one advantage about a turbo engine - you can vary the boost easily to suit the octane rating for a particular type of petrol.
But I can't see how just adding an octane booster or using different brand of juice will change much .. .

Comments anyone ?? !!

[peter_coupe]

I fill my car with regular Shell LRP once in 3 months, other times I use only Shell Optimax.

With LPR engine idle is rough and at 850rpm, while with Optimax idle is steady at 600rpm.
Power delivery is smoother with Optimax but overall acceleration and top spped remains same to me.

I run timing at 14 deg all the time and 2x 42 DCNF on Alquati inlet, Breda cams,10.1 pistons, flowed head and 2inch exhaust.

Ciao

[Will]

In response to Wallace's post, yes, the point of additional octane is that the ignition can be advanced to capitalize on the burn better- and a higher compression ratio can be used as well. Correct that an octane boost won't enhance performance much (if any) in a stock motor.
Here we can get 110 octane racing fuel no problem, usually VP locally. You can do a web search for VP fuels for more information than I can tell you for sure.
-Will

[Wallace]

Exactly that !

[Will]

Most fuels will yield more or less the same amount of heat per weight burned, hence the measurement of horsepower as BSFC (Brake Specific Fuel Consumption).
The only way to get more power, is to burn more fuel. The Octane simply retards the tendency of the fuel to promote spontaneous ignition, controlling detonation or "pinging".
So why not just jet up the carbs? Because fuel needs air to burn, about 13~14:1 by WEIGHT for our cars. That leaves two choices:
a) get more air into the engine
or
b) find a fuel that consumes less air in the burn

A is the most common route by far, including forced induction, porting, big valves, cams, etc.
B is only undertaken by those who are willing to deal with the inherent problems of alternative fuels, but can yield good results, especially for short- duration running, i.e. drag racing, etc.

In this camp, the most popular route taken is Nitrous Oxide, which allows roughly twice as much fuel to be burned, the nitrous oxide contains a much higher oxygen content than air does. The other choice is nitromethane, which breaks down in such a way as to require less than half the oxygen from "outside" to aid combustion- I think nitromethane burns stoichiometric at something like 6.5:1. Unfortunately, it also contains a lot of water, but that's a seperate issue.

Unless you are burning one of these fuels, your main concern is getting enough AIR into the engine, not fuel.
Too much air for a given compression (and ignition timing) is when you need to start worrying about upping the octane.
There's no benefit of running high octane gasolines in a stock compression, normally aspirated motor EXCEPT some of these fuels are also treated with detergents and anti-varnish agents that may help clean out a dirty jet of an injector with a poor spray pattern.

One thing I would recommend is the use of a fuel STABILIZER if the car will be sitting over the winter (STA-BIL or equivalent). This will help. I'm not sure about draining the tank, some say it preserves linings, others say it accellerates thier decomposition. Personally, I don't know. Anybody have opinions/experience on this issue?
-Will

[Wallace]

I've heard that as well - which is a bit of a pisser as I've a full tank of the stuff in the monte which is 5 years old .. . .the plan is to get it out a bit at a time, use in in my everyday car, then fill up with new stuff when I EVENTUALLY start (or try to) the new engine.

Point though - if it is brimmed up, then there's b-all surface area for the fuel to oxidise (I assume this is what happens.. . ). Personally - I'd be tempted to leave the tank full for the same reasons - with no air in contact with the tank walls, it's not going to rust .. .

[garethwd]

There are still fuel stations around the uk that still sell real leaded petrol.
I know of 2 theres one in telford by forrows (a ford dealer) and one in the mount shrewsbury! there used to be website with all the stations listed but I cant rember the url sorry! :roll: I'll try to find it and post it on this thread

[garethwd]

Here's the link hope its of use to uk forum members!

http://www.leadedpetrol.co.uk/