Running a 98 RON tuned engine on 95 RON

[mikey k]

Guys

I'm sure there is a simple answer to this one!
But I not sure
I have a supercharged S2000 with a few extra mods taking it to 419 BHP.
It has an aftermarket ECU (AEM EMS1052) that was tuned on 98 RON.
I'd dearly love to have a hoon around NW Scotland but the complete lack of 98 RON north of Inverness has put the mockers on it.
It also means I have to keep a can of 98 RON in the boot for when I run out!

So a couple of questions!
1) Am I being a muppet considering Octane booster for such a trip?
2) What are the risks of running it on 95 RON?

Please help me get to those areas 98 RON won't reach!

[Vixpy1]

Octane booster works, but really only as an added boost to 98.

It ultimately depends how harshly its been tuned, I suspect it will probably knock its tits off on 95 and you will do a piston. Most of the AEM's do have knock control, But its not great to be relying on it to pull the timing back all the time.

[mikey k]

I suspected that was the case running it on 95.
The AEM does have knock control and O2 feedback but the tuner turned them both off because he does not trust them!

Edited by mikey k on Tuesday 17th March 17:58

[stevieturbo]

If driving normally, then it would be fine. If your intentions are to have a bit of enthusiastic driving, then ensure you do use a quality octane booster, in the specified amounts.

Its sad in todays world, when we cant even get decent fuel. SUL ( 97RON ) Isnt common place here in Northern Ireland, but fortunately it is obtainable. If you can trust it is SUL.
In Southern Ireland....its all but impossible to get hold of.

When I as in Denmark last year...I dont recall seeing it anywhere, in fact, they seemed to be selling 93/95 octane !!!

[mmm-five]

I know there's a Tesco petrol station in Inverness and another just north of Inverness, however I can't remember if they do their 99RON fuel there, as the last time I visited either I was in a car that only required 95RON.

Depending on the size of your tank and how your fuel economy is with 400bhp+, it may be best to plan your trip withing distance of that.

I got 22mpg on my last 250 mile blast around North Wales and just about made it to a garage that had 97+ available.

[chuntington101]

How about a meth injection kit? not a cheap solution but might be an idea. would add octane and reduce charge temps helping proventr the dreaded dept. or you could use a water injection system. this wouldn't give you any performance gains but would add some safety.

or why not get it re-tuned?

sounds like a very nice car. is it a vortec supercharger??

Chris.

[mikey k]

Cheers guys

I did contemplate getting a 95 RON map done and keep a net book in the car to swap maps as nesessary! It is a Comptech SC @ ~ 12 psi boost WOT.

Edited by mikey k on Wednesday 18th March 10:22

[stevieturbo]

IMO dual maps based on octane is silly, unless the ecu also has knock correction available.

How can you ever be truly sure, your tank is completely empty of the lower octane fuel before trying the car flat out.

I know I wouldnt want to be taking that risk, unless Ive put a couple of empty-full cycles to ensure....and having to do that almost makes the dual maps pointless.

[tristancliffe]

Retard the ignition. You'll lose a bit of power, but you won't blow your engine. Retard it by about 4° everywhere on the map and will almost certainly be fine. If it starts to pink then lift off and be a bit gentler (or retard it a bit more).

[aatekkie]

Hi

I'd be very worried about running this car on lower octane fuel. If you go to this site:
http://www.petrolprices.com/

and type in the name of the town or postcode of the areas you intend to visit you should be able to see if and where the higher octane fuel is available

[anonymous-user]

OK I'll start a debate, I'd suggest there's no such thing as 98 RON, theres 98 plus or minus a percentage, and 95 the same plus minus. I bet the 95 plus the percentage is near as dam it 98 minus the percantage, (it would only need 3.5 percent each way) and for one tank full driven easy you'd see no differnce on the road.

We were in Thailand last week and had to run a VFR 750, a VN 900 a BMW 100GS and a ZXR9 on 91 octane for one tank full, and all 4 performed faultless.

[Marf]

Berw said:

OK I'll start a debate, I'd suggest there's no such thing as 98 RON, theres 98 plus or minus a percentage, and 95 the same plus minus. I bet the 95 plus the percentage is near as dam it 98 minus the percantage, (it would only need 3.5 percent each way) and for one tank full driven easy you'd see no differnce on the road.

We were in Thailand last week and had to run a VFR 750, a VN 900 a BMW 100GS and a ZXR9 on 91 octane for one tank full, and all 4 performed faultless.

It all depends on the engine/mapping that we're talking about here. I had a turbocharged car which had been mapped to run on Shell V-Power, got caught out in the sticks and had to put in Total Excellium 97 octane. As soon as I brought it on boost there was audible pinking.

Standard engines with standard OEM fuel/ignition mapping are generally far more tolerant of lower octane fuel than something tuned to run on a specific grade of petrol.

[anonymous-user]

Interesting you quote V Power I wont use it, don't use the bikes or the car that often, and if left to stand with V power in them they wont start. My theory is that the benzin evaporates off and leaves the ditergent to block jets. On the bike if I have to use v poer I drain the carbs by turning the stop cock and running to a stop.