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The mkiv Supra Owners Club

Shell v-max or your own additive - na/t. ?


herbiemercman

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I have mixed views on this subject, re are all fuels the same? i have a friend who was involved in the Isle of Man TT races as i was, and his job is delivering petrol to outlets. He claimed that they all fill up at the same place and deliver to everyone.

 

With diesel i dose my own fuel with straight 2T oil and cetane, works out at 80p / shot and far less than redex etc at £5.

 

With petrol i am not sure about the situation and post my NA/T conversion i was advised that Shell V Max was a must?

 

My question is, if i buy standard unleaded and add a dose of redex additive am i using a suitable fuel for my car? Herbie.

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Hi Bignum & JJZ, My car was mapped on Shell v-power, round my way they call it V-Max, just thought i would see what other members think about trying the standard unleaded with your own additive like Redex etc, may be its best to stick with the Shell V-power. I do not want to compromise the way the car is running, perfect tick over, very smooth driving gently and lots of smooth power on tap.

Some of my friends use the Shell V-power and there cars are designed to run on standard unleaded, but they claim the car runs better, is it the case with my NA/T that standard unleaded would not be good for my level of tuning? I ask this as my compression ratio is still stock. Herbie.

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Don't run regular unleaded! If it's been mapped on vpower, stick with that, or BP ultimate if you need to.

 

If you're ever on a trip etc and get caught short, it is okay to use regular unleaded, but don't thrash the car at all until you put higher octane fuel in.

 

Google image search 'det damage' and you will see why :)

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Redex is an upper cylinder lubricant, an oil. Adding oil to petrol reduces it's octane rating, not something you want to do. Does the engine management respond to knock? if not, even more vital to keep the best fuel you can in the tank and not inadvertently reduce octane with inappropriate additives. If I have an engine that is right on the limit with super unleaded (and NO ONE should map a road car engine so that it NEEDS SU unless it has sophisticated knock control), I would add toluene at 10% by volume to the fuel.

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My syvecs is mapped to Vpower Nitro.

It's absolutely hates BP.

Tesco momentum is great however.

 

I'm running 600bhp

 

FYI - BP ultimate is only 97 RON, compared to V Power and Momentum being 99RON

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Mines a Jspec N/a so I'm guessing it wont have ever been mapped here, so always stick in V-power or Momentum.

 

I've always used standard unleaded in my NA. AFAIK it's fine for an NA, but definitely not for a JSpec TT. For an NA-T or single turbo, I've no idea idea, they're bespoke cars with bespoke mapping.

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I've always used standard unleaded in my NA. AFAIK it's fine for an NA, but definitely not for a JSpec TT. For an NA-T or single turbo, I've no idea idea, they're bespoke cars with bespoke mapping.

 

Ok but wouldn't it have been setup for Jap fuel originally or does that not matter on a N/a?

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Ok but wouldn't it have been setup for Jap fuel originally or does that not matter on a N/a?

 

It will have been set up to use Japanese fuel. However, in NA supras it's not necessary to use high octane fuel, there's no detrimental effect. Maybe detonation/knock is hard to trigger without turbos.

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Boost, be it a supercharger or turbo charger, adds air and fuel *under pressure* to the chambers and dynamically raises the static compression ratio. More boost, higher the dynamic rise in CR is. hence too much boost = detonation, just like too high a static CR in an N/A engine.

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It will have been set up to use Japanese fuel. However, in NA supras it's not necessary to use high octane fuel, there's no detrimental effect. Maybe detonation/knock is hard to trigger without turbos.

 

Ok - so in that case if it has higher octane fuel in it, it should improve it's performance slightly, but not a long term problem if not used.

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Ok - so in that case if it has higher octane fuel in it, it should improve it's performance slightly, but not a long term problem if not used.

Correct. If you do change the type of fuel you use, you may want to reset the ECU so it re-learns the trim levels for the new octane rating.

Edited by stevie_b (see edit history)
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Correct. If you do change the type of fuel you use, you may want to reset the ECU so it re-learns the trim levels for the new octane rating.

 

Cheers Steve, thanks for the responses, does having the battery disconnected for some time reset the ecu as in a few weeks? If not then wouldn't know if it has ever been changed since its former residence in the east :)

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Cheers Steve, thanks for the responses, does having the battery disconnected for some time reset the ecu as in a few weeks? If not then wouldn't know if it has ever been changed since its former residence in the east :)

 

Disconnecting the battery for about 1 minute will reset the ECU. There's a neater way though: there's one or two fuses you can pull for a minute or two to reset it. I forget exactly which ones, but searching on here should give you that info. Pulling the fuses will probably mean the radio and clock don't lose their settings.

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Ta, its been jump started every month for a year or so now to keep it ticking over for 1/2 hour or so, so it's had a good reset then :)

 

Not necessarily. Jump-starting the car won't reset the battery. If you mean that the battery on yours is dead (hence why it needs jump-starting!) therefore the ECU will have been reset, I don't think you can assume that. The car battery might have enough power to keep the data in the ECU, but not enough to crank the engine or turn on the lights.

 

In short, from what you've described, the battery would have to be very dead in order for the ECU to reset.

 

It might be that the ECU adjusts the trim levels over the course of time anyway, in which case it should be adjusted to whatever fuel you've been putting in it by now.

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Not necessarily. Jump-starting the car won't reset the battery. If you mean that the battery on yours is dead (hence why it needs jump-starting!) therefore the ECU will have been reset, I don't think you can assume that. The car battery might have enough power to keep the data in the ECU, but not enough to crank the engine or turn on the lights.

 

In short, from what you've described, the battery would have to be very dead in order for the ECU to reset.

 

It might be that the ECU adjusts the trim levels over the course of time anyway, in which case it should be adjusted to whatever fuel you've been putting in it by now.

 

Very dead! Has a pita immobiliser that drains batteries, so I think we can say it'll be reset by the time I put a new battery on soon. Cheers again.

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Many thanks for all the comments from members, especially Chris Wilson who i know personally and he sorted my brother's 2tt when no one else had a clue what to do, we need to be aware of the knowledge he inputs to this club. He does not come cheap, but the best never do. Herbie.

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