Engine mapping - 95 or 97/98 RON fuel ?

[skydragon]

My 1.6K EU3 car was upgraded to DVA K05 spec recently (flow ported head, larger inlet valves, 285H cams, Jenvey TB, larger injectors, Emerald ECU).

 

It's due for it's rolling road mapping session at Emerald in a few weeks time and will hopefully deliver 180-185bhp.

 

Whats the general concensus for fuel for upgraded engines like this? standard 95 RON or super 97/98 RON?

 

(I obviously want to make sure I've got the best fuel in the car for the mapping session and usage thereafter)

 

 

1.6 K Series EU3, 2003, with DVA K05 and a few other goodies...

website here

[Mick Day]

Why not ring Dave Andrews/Dave Walker & ask their advice?

 

AFAIK using higher octane will enable greater spark advance. However beware if you use 98 octane (or something higher) as you will have to use this all the time or risk detonation.

[6speedmanual]

95 octane is good in a K as I understand that detonation is not usually the limiting factor in getting the best power out of them. 95 octane fuels have higher calorific value so for any given amount of fuel introduced to the cyclinder, there is more energy available and theoretically gives more power.

 

R400 K series on RBTBs mapped to run on 95. (200bhp)

 

 

Peter

 

 

 

BRAWNGP green SUPERLIGHT

FCITW 2009 😬

[skydragon]

Spoke to Dave Walker, he says there is little practical difference between the two grades, so says 95 RON is fine.

[Z3MCJez]

95 octane fuels have higher calorific value so for any given amount of fuel introduced to the cyclinder, there is more energy available and theoretically gives more power.

Is that right? I've always thought that one of the benefits of 98 over 95 was better calorific content, and although that might not mean more power, it does seem to be borne out with improved efficiency ...

 

Jez

[6speedmanual]

The calorific value difference between 95 and 98 is small, maybe only circa 1%. It's quite hard to find exact MJ/Kg info for fuels and not all fuels of the same octane rating will have the same calorific value..

 

The main issue is that if detonation is not the limiting factor in getting the optimum power output from an engine, then there is no point in using a higher octane.

 

Many factors such as combustion chamber design, compression ratio, sensitivity of the power curve to spark advance, etc determine whether a high octane fuel is beneficial.

 

If there is no advantage to be gained from 98, then one may as well use 95 and save the price premium.

 

I wonder how many people run their K series R400s on 98 to no advantage?

 

Peter

 

BRAWNGP green SUPERLIGHT

FCITW 2009 😬

[FatVik]

The little book I got with my 400 states that it should only be run on 98RON. That's what I have been doing...

 

ETA: Not that I am capable enough to know the difference between 95 or 98 😬

 

-FatVik

 

Edited by - FatVik on 12 Mar 2010 20:23:48

[6speedmanual]

Vik

 

The CC may suggest 98, however Minister Power who built the engines (see their website) and a guy I know who was involved with the development and mapping of the high performance K engines say all the tune work was on 95 octane.

 

Peter

 

BRAWNGP green SUPERLIGHT

FCITW 2009 😬

[FatVik]

Ah cool, so I get to buy a bit more petrol with my pocket money by sticking to 95RON :D

However, do you (or any other BCers) know if its better to run 98? I seem to recall reading somewhere that 98 or 99 have more detergents in them that help the engine a little bit....

[The Old Boy]

My Minister data sheet for 208bhp unit says use 95 RON.

 

Should add this was for Superlight 'Road' MAP.

 

Edited by - The Old Boy on 13 Mar 2010 12:51:36

[Nick Chan]

There was recent thread here on the same subject and the general consensus was to have the uprated fuel to maximise the potential of your engine after the upgrades otherwise why spend the money.

 

Personally I would still stick with 95 as the car is mainly road use and use 98 when its on track and the benefit is to be gained otherwise its just a waste of money unless you are looking to drive at 10/10th on the road which I wouldn't have thought is the case!

 

HTH

 

Nick

 

PS Speaking to CC about the new R500 and what fuel to put in, Andy Noble said stick in 95 as that was absolutely fine for road use

 

-----

Back in a BEC! - but done alright in Class 1...

[6speedmanual]

The more "detergent" and other additives in the petrol which are not petrol, the less calorific value!

 

If the super-duper upgraded engine specification does not require 97/98 or does not actively adapt its tune depending on octane, it will not produce any more performance from 97/98 over 95. This is applicable whether on track or road.

Skydragon refers to Dave Walker saying there is little practical difference. He almost certainly means that the spec of engine you were discussing would probably not produce any more power for running it or mapping it with 98 octane on the dyno.

 

All modern pump fuels have complex additive packages to keep various elements of the fuel system, combustion process and cats clean. The petrol companies make more of a 'song and dance' about it for their super grades as it helps to justify the 10p/l premium.

 

Where the high octane fuels are beneficial is in engines which are prone to detonation due to the combustion chamber design, the compression ratio, etc, etc... and to some extent the ignition timing (if running more advance gives access to more power and higher octane facilitates this).

 

Where the super-unleadeds come into their own is where engines have ecus which can adapt by controlling fuelling, ignition timing and turbo boost to take the combustion process right up close to the detonation limit without actually going in to it.

 

It is important to know what fuel your engine needs and if critical to use higher octane in a particular engine then so be it. But where 95 delivers the job required of it it's fine to stick with in all situations. The "Oooh, I'm doing a trackday, I'd better put in Super" is just an expensive comfort blanket and won't make anything better.

 

Peter

 

BRAWNGP green SUPERLIGHT

FCITW 2009 😬

[Simon Owen]

Pete !!!

 

I'm off to Emerald on 23rd April to finally get the jigger mapped and been thinking about this for some time.

 

Think I'll fill 'er up with 95 and save myself a few notes

 

 

[Rust Red Seven]

Go to Germany and buy 105 octane and stop dicking about that makes them move

 

2l zetec tweeked by Dunnell

 

Good old 5 star

 

RRS

[Graham King]

When I had my K-Series (213BHP) mapped by the 2 Steve's they advised to run it on 95 for road and 98 if taking it on track. It was mapped on 95.

 

Graham.

[prangerman]

Reading this, I could turn into Wavy Mavis from "Open All Hours" unsure of what to do and end up filling up alternatively with 95 RON and 98 RON.

 

Peter

[eric]

98 will always be better than a 95, however if your right foot is light, 95 can go well.

 

My advise is: put good coolant, good oil and good fuel in your nice engine.

This will be always cheaper than a new engine ...

 

[Roger King]

If the car is mapped for 95 octane then anything higher is a complete waste of money, with the sensible exception of track use where the probable higher temperatures and increased wide open throttle running mean it is no bad thing to have a little more 'headroom' before disaster strikes.

 

The one thing higher octane won't give you though is any more power than 95 octane (unless you have a management system that adapts to suit differing octanes). In fact, as has been said already the higher octane fuels theoretically have a lower calorific value and therefore contain a little less engery, although the difference is tiny.

 

While higher octane fuel will give you no more power in itself, what it does allow you to do is increase the state of tune of the engine so that the engine is then more efficient and produces more power. The most obvious change would be to increase the compression ratio to a point beyond where 95 octane fuel would detonate as it burned, causing major damage. You can potentially increase the ignition advance too, but there is something of an old wives tale that more advance = more power - WRONG! What increases power is having the CORRECT ignition advance and if your engine is capable of running at optimal settings on 95 octane you'll do more harm than good by mapping more in. In fact if you increase the compression ratio to take advantage of higher octane fuel you theoretically then need less advance.

 

Turbo engines are a different case. They have to have adaptable advance curves to take into account different levels of boost and fuel octane.

 

 

[Steve, Carol and little Cl]

What Roger said.

 

The point about track use leads me to think about the various threads I've seen concerning fitting different temperature thermostats. It might be worth noting that coolant temperature has an effect on the det limit of an engine, whereby the higher the temperature the more retarded is the det limit. I seem to recall a figure of around 1 degree change in det limit for around 5 degrees difference in coolant temperature, although that's just a rule of thumb, and the det limit of each engine reacts differently to a change in operating conditions. It's just worth bearing in mind that if your engine is set up for a certain RON rating of fuel, and the ignition is det limited at higher engine loads, then fitting a hotter thermostat may cause more knock to occur. Even if you have an active det sensor, knock will occur before the ignition is retarded (it needs to be detected, and for it to be detected, it must occur in the first place). Also, no det sensing system is 100% reliable, and there is always the risk of larger detonation events slipping not being detected (anything above 10-15 bar can be critical). So if you are running with any changes which may cause a rise in engine temperature, such as track day use (as Roger suggested) or running with a hotter rated thermostat, you may want to give yourself a bit of a safety cushion to avoid engine damage. You can do this, obviously, by using 98 RON when the engine is mapped for 95 RON, or using 99 RON or 102 RON if the engine is mapped for 98 RON. If, however, you are not running in these adverse conditions, then, as Roger said, putting anything else in the tank is a waste of money.

 

P.S. Please don't all go assuming that 1 degree shift of det limit for 5 degree change in water temperature is also the case for any of your engines, as it really is just a rough rule of thumb. The manufacturers will test their engines during the development process to see how sensitive they are to different operating conditions. And don't forget that the det limit is also affected by inlet air temperature, valve timing, etc, and will change as these parameters also change.

 

 

Steve