Which petrol??

[james123]

Just a quick one.... Which petrol is best to use???
A mechanic told me the cheaper 95 Ron stuff is better to use as it's what these cars are designed for... I've had no problem running the 99ron stuff

[AdamP]

Just a quick one.... Which petrol is best to use???
A mechanic told me the cheaper 95 Ron stuff is better to use as it's what these cars are designed for... I've had no problem running the 99ron stuff

You're paying extra for something that is offering no advantage. It wont damage anything but you arent gaining anything either.

[Lauren]

You can use 95 Ron/premium unleaded fine. No point paying extra for Super when it gives you no advantage.

When I had an NA I used to run it on Super when I took it on track but didn't bother for the road. The only reason being that Super will offer better protection when you are thrashing the nuts off it.

[pk_090]

Little extra. I remember reading a paper by engineers who dyno tested exact same cars in exact conditions on standard 95 RON shell fuel vs shell v-power (optimax at the time). i can remember 3 of them there was a peugot 206 on a 1.6 petrol engine a scooby on the boxer turbo and there was a ferrari 360. All ad the tanks drained and put with 10 litres of 95 ron and then v-power, exact same ambient temp etc. and v power gave slight power gains depending on the engines. Obviously if the car is remapped to 99 ron then you will get more and the benefits of v-power over 99 are so much better, i get better mpg from it also.
Alex

[SuperRedMR2]

I agree with Lauren no advantage what so ever unless you have money burning holes in your pockets!

V-power did sweet FA for my MPG, it made it worse.

[elbon50]

If compression ratio was such that it wouldn't run without detonating then a higher RON could be useful James

For a stock engine 95 Ron is the one to use

Peter

PS did you get the engine problem sorted ?

Was it ignition timing

[james123]

Ok thought as much..
And yes Peter I was just the one tooth advanced, Cheers for your help, she's running sweet as now!

[Jimbo_Jet]

I suffer noticeable pinking in mine with 95 RON if accelerating hard while the engine is under 3000 revs, especially if going up hill and so adding extra stain. I switched to Tesco 99 and the problem vanished and the car certainly 'feels' a bit more perky on 99 but that could be in my head

However, I've noticed no benefit in MPG to speak of. I generally mix 99 and 95 now to get a similar result.

[elbon50]

I suffer noticeable pinking in mine with 95 RON if accelerating hard while the engine is under 3000 revs, especially if going up hill and so adding extra stain. I switched to Tesco 99 and the problem vanished and the car certainly 'feels' a bit more perky on 99 but that could be in my head

However, I've noticed no benefit in MPG to speak of. I generally mix 99 and 95 now to get a similar result.

Is your ignition timing a little too far advanced I wonder ?

Peter

[Lauren]

I admit, that I run only on Super for the AE86, but it is an import and RON ratings in Japan as I understand it are different, so car is timed differently.

[SuperRedMR2]

When I was at the silverstone classic with the mk1 club when we did a retro run I chucked about £15 worth of 102 ron at the special BP station they had within the circuit for a tidy sum of £2.50 a litre! Made no difference lol

[PW@Woodsport]

Quite surprised by some of the comments made, my experience has always been that using 95 ron on a Mk1 with stock timing makes it pink, switch to 97 and the pinking goes away. I only use 97 or 98 in my Mk1, i can feel the engine running better, maybe that's the mechanic in me, but when i've had to use 95, when there was no other choice, it pinks.

In my opinion 97 is the one to use on stock timing.

[AdamP]

Quite surprised by some of the comments made, my experience has always been that using 95 ron on a Mk1 with stock timing makes it pink, switch to 97 and the pinking goes away. I only use 97 or 98 in my Mk1, i can feel the engine running better, maybe that's the mechanic in me, but when i've had to use 95, when there was no other choice, it pinks.

In my opinion 97 is the one to use on stock timing.

Interesting. I have no trouble on 95 RON. I'd be surprised if anything from the 80s that was designed to run on unleaded needed more than 95 RON as until the 90s and the disappearance of 4 and 5 star, unleaded was inherently low RON! Most cars were designed with the capability to run on 91-92 RON fuel.

[PW@Woodsport]

Well it greatly depends on your ignition timing, a degree or two can make a massive difference, the difference between pinking and not.

The pinking is also very subtle when it happens, it's not something obvious, like i said on any Mk1 i've had on 95 i can feel the engine pink on stock timing, but it would probably be missed by most.

[oukie]

This is one of those threads that pop up every now and then and prompt the same arguments

I get 20 miles more from my tank on V-power its not just the higher octane level remember, the V-power has additives to help clean your injectors and all sorts

Without doubt my car runs way better on V-power, its all I use but hey my car is a toy so cost is not a problem as I don't use it for work etc.

The best way I can describe how my car runs on 95 ron is a can of nails rattling around, the V-power on the other hand just makes the engine so much smoother and the power delivery is much improved

Chris

[JMR_AW11]

Just to complicate things even further, the ignition timing map is more advanced on a mk1a at high rpm/load. This is the 'little' ECU 89661-17030.

So if I had a mk1a I'd be tempted to run the higher RON fuel.

My late 1989 red mk1b seems to show little preference for either fuel but when I had a second mk1b as a daily driver (same year and ECU type) it was more prone to pinking at around 4000rpm and seemed better on the higher ron fuel. So a bit strange...

However, I did find that driving it hard on regular long trips made it seem to pink less. But that could have been just differences in fuel between fillups I guess.

I don't know why they softened the timing on the later ECUs. They also shrank the map sizes so the later cars lack the fine tuning of the mk1a above 5600rpm for ignition timing. i.e. they are only mapped for ignition to 5600rpm on the later mk1b and 5200rpm on the crossover cars.

Above these rpms the mk1b ECU uses the same ignition timing as 5600rpm (for a given load) right up to the limiter at about 7600rpm.

The mk1a therefore boasts extra mapping points in 400rpm increments from about 5600rpm right up to 7200rpm.

[JMR_AW11]

The other thing to watch out for is that the ECU also adds about 3 degrees of ignition advance when the TVIS kicks in (after a tiny time delay).

However, the ECU has a kind of hysteresis on the TVIS so for example on a mk1a if you exceed 4350rpm the TVIS kicks in and you get a 3 degree step in timing. But it will hold this timing (and the TVIS) until you drop below 3950rpm so you can have a 3 degree difference in timing at 3950-4350rpm depending if the TVIS offset is still active or not.


For the mk1b the rpm figures are 4250rpm and 4650rpm.

So you have to be wary of this when testing for pinking across these rpm ranges

[Jimbo_Jet]

Without doubt my car runs way better on V-power, its all I use but hey my car is a toy so cost is not a problem as I don't use it for work etc.

I've only ever used V-Power once but even I noticed a difference pulling out of the garage after running a tank of 95 out, it really did feel eager. I personally would use V-Power all the time if it was cheaper and I could collect Tesco points with it like Tesco's 99

Last year's Tesco points got me and the missus a free trip to Amsterdam!

[Jimbo_Jet]

Just to complicate things even further, the ignition timing map is more advanced on a mk1a at high rpm/load. This is the 'little' ECU 89661-17030.

Well mine's a MK1a and I didn't notice a real V Power benefit in my old MK1b so that makes sense. I always knew the mapping was different between A and B revision cars but it's not until you dive an A you realise how they like to Rev that little bit more than a B.... IMHO

[SuperRedMR2]

I do put in 99 ron sometimes to clean the injectors out n get about 3mpg more. Ill chuck a tank load in tomorrow. Iv never noticed mine pinking. Sorry for chav spelling I'm using my blackberry to reply.