Shell Optimax or BP Ultimate???

[Tom]

Nice to see at lease SOME people can read around here

Yes, the power increase DOES come from the CR increase BUT you need higher octane fuel to stop it pinking and destroying itself due to the higher CR.

When I say 'build an engine' I don't mean 'slap some bolton thing on the side of it and hope for the best'. I mean (at the minimum) take it apart, recalculate the CR, make/buy new pistons to increase the CR, put it back together and then rolling road tune it to suit the new engine.

 

[SteveH]

Still not convinced that would make such a big difference over building the same engine but tuning it to run on standard 95RON.

 

[Tom]

You don't build the engines the same. You can't 'tune' an engine with a high CR to use normal petrol, it simply does not work.

Upping the CR is a bit like turning up the boost on a turbo engine. Higher pressures and higher temps mean more power. Its a simple and well proven fact of life.

 

[Tom]

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930091271_1993091271.pdf

Admittedly its a bit old

"The report shows that an increase in brake horsepower and a decrease in the pounds of fuel used per brake horsepower hour usually results from an increase in compression ratio."

"CONCLUSIONS
From the investigation described herein, it is concluded that ovier the range of ratios investigated an increase in compression ratio produces an increase in power and thermal efficiency provided such a fuel is used that there is no preignition or detonation. The gain in indicated horsepower and indicated thermal efficiency is very nearly that which would be anticipated from a consideration of air-cycle efficiencies. The gain in brake horsepower and brake thermal efficiency should be as great or greater, as there is no consistent evidence that friction horsepower
increases with increase in compression ratio. What compression ratio is best for a given engine depends very largely upon what fuel must be employed to avoid preignition or detonation. As has been explained, the disadvantages incidental to the use of some fuels may offset the gain
due to an increase in compression ratio."

So even in the 1920s they knew that a CR increase would give more power.

 

[Buzz]

SteveH, i think you'll find that for the most part, Tom is like a textbook. If you read what he said, you'd understand that he's not the type to believe in an Ecotek

Buzz (formerly LightWarrior)
The champion of the Bravo 1.4
Owner of the Bravo 1.8
Member Page

 

[Anonymous]

Yes, but forced induction engines do not have high compression ratios unless they are highly tuned race engines with forged pistons etc., but even then they are not excessive otherwise longevity will be measured in minutes as opposed to days. The boost from the turbo would blow the head gasket or a piston if the CR is too high. Typically CRs are 7.5 to 8.5:1 on forced induction road cars.
andy

 

[JOsh]

Now i know i'm gonna get shot down for saying this but i do have an ecotek, before eveyone says i wasted my money i have found to gain from it.

standard engine = about 380miles tank
induction kit and exhuast fitted = 280 - 310 miles a tank (at very best)

ecotek valve fitted = around 340 miles

ok its not a massive difference but with prices these days it helps.

Also i didnt pay full price it cost me about five pints from a mate so had nothing to lose, esp not having to pay for the drink (perks of running a bar) LOL

now i know i've left myself wide open to be slated, this is just an honest account from me

 

[Tom]

Andy, the turbo acts to INCREASE the CR by filling the cylinder with more air to begin with. The effective CR is higher.

The CR may be 8:1 with no boost but when you're running 1 bar of boost its filling the cyl with almost twice as much air as before. The effective CR is more like 12:1 now.

 

[Stu R]

I never thought me asking a simple question on fuel would get such a debate going

Only two more responces and I hit the 50 mark.

"Old enough to know better, Young enough not to care"

 

[Anonymous]

Tom, which means if the off boost CR is 10.5 or 12.1 as in a normally aspirated engine then when the turbo comes on song BANG goes the engine. So engines have pistons shaped to give lower compression ratios and tuff head gaskets not that they aren't tuff anyway. I new some one who tried to run a normally aspirated CR engine 10.5:1 with forced induction, solid copper head gasket. The engine's longevity was under the hour. I think we agree. Then as has been mentioned there is the timing, degrees of advance and wild cams to help destroy a weak bottom end. oooohhh.

So what's the exact physiology of this ecotek valve? each doin our bit to see your post hit the magic fifty.
andy

 

[Tom]

Exactly, thats why you don't put forced induction on an N/A engine. You have to build an engines internals to suit the application.

An ecotek tries to lean out the mixture by introducing air after the MAF. Amazingly it doesn't work. They've been done over by the ASA a couple of times now for false claims on their adverts.

 

[Stu R]

Hey I hit the 50 mark

So to close off, the moral of the story it:

Don't use optimax unless you have a Jap car inparticular a jap import as they run on higher octane or you have heavy modded car that needs the use of high ron fuels, because a normal car doesn't really benifit that much.

Don't buy an ecotec valve as they don't do what they say on the packet.

Never turbo a N/A car as the CR ratio plus the forced induction is too much for the engine to take. Always go for a turbo engine conversion as this probably be the cheaper option and would be safer in the long run.

Cheers guys

"Old enough to know better, Young enough not to care"

 

[Pete McK]

Everyone has their own experiences and opinions with Optimax, Tescos and BP Ultimate. Here's mine for what it's worth:

On the Marea (2.0 20v) I get 26-27mpg on plain unleaded. On Optimax, I always get 29-30mpg. It feels a little more lively, but this might just be the placebo effect.

If I use a couple of tanks of Optimax, then run it right down and put plain 95 RON in, it will start up ok at the petrol station. Drive a couple of miles home, next day start up again, and the ecu warning light will come on for 30-40 seconds. Just for the first cold start with 95, mind.

BP Ultimate in my own experience is no good. My turbo cinq (and as friend's) absolutely hate it and won't run well at all, even worse than on plain Supermarket 95 RON. I don't use BP petrol unless I'm absolutely stuck.