MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Shell V Max fuel etc.

I don't know if this should be in the tech section or general, but here goes.
Does anyone have any thoughts on the advantages or otherwise of fuels such as Shell V Max in our cars for road use.
I currently use 97 RON unleaded with Valvemaster Plus which has an octane booster and the car goes OK. I was wondering if a bit more power could be squeezed out of the engine by using one of the higher octane fuels and still use Valvemaster.
I read on another forum that Imprezas and Evos are getting an extra 20 BHP by using Shell V Max. I realise of course that they have modern engine mapping and turbos etc. I also read that Shell will shortly be making available in the UK their 102 RON fuel. Or would that just blow the old girl up?
Anyone got any ideas?

Bernie.
b higginson

Extra octane rating allows the engine to have more compression and more advance to produce more power.

As you say with modern engines that have the benefit of knock sensors and lambda they can make use of this extra octane. Unfortunately your humble engine can not adjust itself so would need to be done at the build stage. You need to build in more CR to make use of the octane, so purchasing it now IMO would be a waste of money.

I try to make my cars all run on simple unleaded then I can have cheap motoring. :)
Bob Turbo Midget England

On the normal turbo Impreza, the 225 bhp one, the 97 octane fuel makes no difference over normal unleaded. Well one difference, it's more expensive.

On the WRX STI, 280 bhp plus, the advance curve is so aggressive at high revs you have no choice but to use it.

There have been a good number of 2008 and 2009 model WRX STI engine failures caused by an over aggressive ignition map. These cars have been reflashed by the Subaru dealers when they are serviced.

There are battles going on at the moment as Subaru UK are refusing to replace some STI engines under warranty.

So even newer cars have their problems.

eddie

Eddie Cairns

Octane makes a difference

All the other aditives don't
It has just been the topic of a hot discussion here in Holland with several consumer organisations tesing and checking.

The aditives made a difference of about 1% fuel economy far less than the added cost of the fuel.
Anny claims of cleaning the engine could not be replicated in real life.

I run my midget on RON 98 because i run a high compression
I avoid the big brands and get my fuel at the cheap un manned stations
Onno Könemann

Additionally, you'll need to set your advance curve to make use of the higher octane fuel - this will need up to 1/2 day on a RR (easier if you have ECU with mapped ignition); but you should benefit slightly in terms of power and mpg.

But if you use ordinary fuel, your engine will pink as it can't detect knock and wind back timing like a 'modern'.

Kseries Midgets can have up to 3 maps on later Emerald ECUs to allow for different octanes and so on; driver selects map according to fill.

HTH

A

Anthony Cutler

I used Tesco Super unleaded in my MGB. I was able to advance the ignition by about 4 degrees and got another 2mpg (7%), which was a greater saving than the price difference between the grades of fuel.
Geoff E

Bernie,

My "standard" 948 cc is very octane sensitive. High speed knocking was a big problem till I gave it BP Utima or added tetra ethyl lead (teraboost.com). Changing the advance curve to 28 degrees max did help as well. I think that the non standard flat AE pistons are one of the reasons for squeeze and knocking. Our engines are made for RON 100. With Ultima it makes much more miles a gallon.

Flip


Photo: original instructions in Dutch


Flip Brühl 948 frog 59

Exactly as described by Flip

His engine had already been built with too much CR for normal feul so using high octane allowed him to make use of the extra Compression already built into his engine.
Bob Turbo Midget England

And there's the difference in Shell V-power fuels. In Germany it's 100+ octane, here in holland it's 95. Because all we do here is stand in queu on the motorway so there's no use for the higher octane (statement by Shell!)
Alex G Matla

So live in the Netherlands, dive into Germany with and empty fuel tank and fill it uo with 100 octane. Take the car to a German rolling road.

Get it set up there, go home to the Netherlands and blow a hole in your piston over time on 95 octane.

eddie
Eddie Cairns

Mh, I live on the west coast of Holland.
Alex G Matla

Hi, I don't know if its psychological but I find that the car runs smoother on the higher octane fuel (mainly V-Max) than on regular fuel.

Thanks
Mark
Mark Whitmore

My Midget is still not back on the road, but 99 octane Shell V-power makes a big difference in my MGB. With lower octane, I have to retard the ignition way past original spec. Like Mark, I also feel that the car runs smoother on 99 than even on 98.

My 3 main MGB engine now has a modern replacement distributor, probably with a wrong timing curve. I am having the original 25D distributor rebuilt, and expect the engine to be a lot less octane sensitive next season.

Tore
Tore

Ive seen the programma "Kassa" on the Dutch television and that could be the same as Onno is referring too.

They had BP Ultima and Shell power and others tested on their "special" qualities on motorways and towntraffic.
Like the so called cleaning the engine - more km's per liter and so on.
Turned out the special fuels did nothing like they are advertised.
They werent bad but just didnt do the thing what they were so special in/for and you get charged extra for.

Despite knowing this I still prefer fuelling Shell and BP as I had some very bad experiences with Texaco on a RollingRoad.
Arie de Best

Funnily, I read today about Shell putting ethanol in their V Max fuel, and what it does to older fuel lines etc
neil munn

Arie
Watch "de keuringsdiens van waarde" on uitzending gemist about fuel verry funny.

Flip
You do no that BP only sels RON 98 and not 100?


The level of ethanol in fuel is a big problem with our older cars
Though it is now at a level that is not yet a problem plans to increase it are ready.
The fuel lines are the least of your problem since they can be replaced.
The casting of you float chamber is a big problem since ethanol eats the protective oxidisation layer.....
Onno Könemann

There are 3 ways to calculate octane: the RON the MON and RON/MON (or RM2?).

So when comparing one octane against another you need to check which method of calculating octane has been used.

There are books with this stuff in ... but not written by me...
Daniel Thirteen-Twelve

Thanks for everyone's input. It certainly made interesting reading.
When I first got my car(1967), we could get 5 star petrol which I believe was 100 octane. (I stand to be corrected on that.) Slightly tweaked cars always seemed to run better on it and if you used lower octane fuel you could experience pinking, but I suppose it was a different mix to today's fuels and it had lead in it.
My freind has a WRX Impreza and as Eddie says, he has to use the Shell stuff because his car is mapped for it and if he uses anything else it doesn't run as well. But I'm talking about a very expensively modified car.
I may do a back to back economy test. ie. normal fuel against higher octane fuel.
I must say that whenever anyone posts a subject on this BBS, besides getting an answer to a problem it always seems to spark an interesting debate which is why I personally think this is the best car related forum on thr net.

Bernie.
b higginson

Not fuels, but "fuel additives" for extra power (aka snake oil) - 5th Gear test http://www.youtube.com/watch?v=VG3j0g88kXs
Geoff E

Bernie

A back to back test with low and high octane fuel is useless

If you car runs on low octane fuel without pinking or running on than putting high octane in it will not show anny difference.
If you want to make the best of high octane fuel you have to adjust your ignition timing (or CR)

so if you want to test go to a RR put in low octan and see what you can get out of the engine.
Then empty the tank and put in high octan fuel and see what that delivers when tuned in.

then decide if you want cheap and easy or expensive and hard to get fuel
Onno Könemann

Bernie,

I agree with Onno on evaluating the effect of the extra octane.

In the mid-80s I was driving a 1970 Saab 99 that was supposed to use premium (high octane) fuel. By the mid-80s, premium was not what it had been in 1970.

The static timing was supposed to be 9* before TDC. With that timing and premium fuel it would knock unless driven carefully.

I had a friend who made anhydrous ethanol to sell to the gasoline companies. I got ethanol from him and ran a mix of 75% regular gasoline and 25 % ethanol. With that blend, I was able to move the static timing from 9* to 18*, and boosted the fuel mileage from 24 to 29 mpg (US) with no knocking.

Charley
C R Huff

There's a thread on the MGB BBS about HIF floats atking on fuel, which is believed to be caused by ethanol in fuel.

Burlen do an ethanol-resistant float for the HS carbs...

http://www.sucarb.co.uk/ProductDetail.aspx?Id=33997
Dave O'Neill 2

I have just read something in the Vintage Japanese Motorcycle publication about the amount of ethanol in fuel aggravating problems of corrosion with mild steel petrol tanks.
Dave O'Neill 2

I just watched the 5th Gear test clip that Geoff E refers to. It is indeed "Snake Oil". These people surely should be looked at by Trading Standards as it appears we are being well ripped off.

Bernie.
b higginson

This thread was discussed between 07/12/2010 and 11/12/2010

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.