Optimax, yes or no?

[tez1978]

I've read somewhere that you can't use optimax as it damages a little plastic part in the engine in rover engined Lotuses, does anyone know if this is true. i've got a 340r.

[Mark Benson]

I know that there's no point in using higher octane fuel in the K series as it doesn't have a knock sensor, but I haven't heard of additives that cause problems for plastic engine parts, sounds a bit fishy to me....

[Mr_C]

I thought the 192bhp VHPD in the 340R needed Super Unleaded to run right cos of the advance in the timing??

Paul

[Mark Benson]

I've got a VHPD in my Sport 190 and was told by Cos at Sportomotive that it runs on 95, so that's what I've been using....

[Janitor]

Well, the debate will rage eternally on this

Placebo effect, absolute bolox, scientific fact, mechanical impossibility will all be strongly voiced and believed in equal amounts

Personally, I have a new Elise 111R and use Ultimate / Optimax / Excelleum everytime... not that I believe any performance gain, but there is a strong view on an extra economy return justfying the extra cost per litre. I buy into that... and also, only the best for my new baby!

[piooly]

The higher octane fuels also have more cleaning agents in them and help keep the engine in better shape so they say. I usually use 99 ron Tesco super unleaded in mine. Placebo or not, the sport 160 loves it !!

[GTRene]

My BMW Z3 M coupe S54( E46 M3 engine) loves it too it does more miles the gallon and feels a bit more responsive also a bit more expensive but still cheaper at the end of the year because of the more miles the gallon! and with tango no seals but shell does, so I save those and at the end of the year I let pay them out for cash so cheaper again
GTRene

[andysv]

my 340 runs worse on lower octane, i'm sure dave at emerald recommends optimax, especially if he's fitting the upgraded ecu that i hope to have soon.

>> Edited by andysv on Wednesday 29th March 22:26

[RIXGE]

Don`t listen to all the hype, once and for all lets clear this one up and put it to bed, Chavsda`s own is good enough, as is Tesco`s too. Wasting your hard earned on any thing else.

[cej]

unless you have the engine management system tuned for the higher octane fuel it's a waste of money, and if it's too high octane you might even loose some hp.
It makes sense if you have the Emerald system and then tune it for the higher octane..

[matrs]

Run My S2 Sport 190 on Optimax, fifth gear run a test a few months back
http://fifthgear.five.tv/jsp/5gmain.j

[jitsukadave]

Dave Walker (not me the other one) said last month in Circuit Driver that he can tell the difference with K-series engine when they run different fuels.
He said he thought Optimax was the best (for power) over Ultima from his experience.

However, not sure how that applies to a VHPD engine.

[RobM77]

jitsukadave said:

Dave Walker (not me the other one) said last month in Circuit Driver that he can tell the difference with K-series engine when they run different fuels. He said he thought Optimax was the best (for power) over Ultima from his experience. However, not sure how that applies to a VHPD engine.

Interesting. Dave Walker's the man for K series engines.

[dragstar]

Gents, Optimax is much like a post-coital fag. Let me elaborate:

They both sound right, both look right. However, once they've finished, you wonder why you bothered

[shangani]

Do you smoke after sex?






Actually, I never thought to check.

[Nick J]

Not smoke, just burning

[beachbum]

shangani said:

Do you smoke after sex? Actually, I never thought to check.

Look behind you next time

[Trixster]

So how much extra fuel economy are people getting using higher octane fuels? I'd need to get an extra 20-25 miles per tank to justify the cost and break even over normal 95, assuming a regular K series isn't going to see any other measurable increase in performance.

[Mark Benson]

RobM77 said:

jitsukadave said: Dave Walker (not me the other one) said last month in Circuit Driver that he can tell the difference with K-series engine when they run different fuels. He said he thought Optimax was the best (for power) over Ultima from his experience. However, not sure how that applies to a VHPD engine. Interesting. Dave Walker's the man for K series engines.

True, and having just looked up the CD article, he does say that the K Series seems to work better with Optimax. However I assume he's talking about when he's mapping an Emerald ECU (since that's what he does) rather than on a standard ECU. I would have thought (but am happy to be proved wrong) that a standard ECU, even on a VHPD will be set with it's timing suitable for the lowest common denominator, 95 octane.
However (and here's where I start to get confused), he mentions MBT, Minimum Best Timing, advancing the timing only as far as you need to to get the best power, not as far as possible which is the reason I was always told that higher octane fuels gave better power, the timing could be advanced right up to the point of detonation and power would increase proportionaltely.
So, an engine, to advance timing appropriate to the fuel would need a knock sensor, which the K doesn't have.

What DW seems to be saying however is that MBT will most likely not be possible with 95 octane in a K series (assuming again he's talking about mapping his own ECU) but that Optimax makes it possible.

So, the question still remains, assuming a standard ECU, what did the engineers map for in a VHPD engine? It's unlikely they could have mapped for MBT with 95, so did they assume 98?

I need a lie down.

[jitsukadave]

My current car shows no change between 95, 97 and 99 RON fuels (slightly off topic as it's not a K-series). The owners club say not to use 95 too much as it's on the edge of the ECU range as it's a Japanese domestic market car, and programmed for 95-108 RON fuel. Still, it's not concked out yet (touch wood).

My parents also had a Seirra with a de-tuned Cosworth engine in it about the time everytihng went to unleaded (1992-1994?). They were told to never put super in; if normal unleaded wasn't available stick 4 star leaded in instead. Not sure how much myth is in that though.