Hanslow

Hypothetical question.....

On a Jap Import (turbo car, not necessarily a Scoob ), can the ECU be remapped to accomodate normal 95 ron UK petrol? I know there will be power loss, but I was wondering if a) it was possible, b) it's safe, c) the long term effects on the engine if it's possible?

If poss, would it give less stress on the engine?

Just wondering

john banks

If you stop it detting when it was before on inadequate octane you will preserve the engine better. However, solely from the mapping point of view to stop it detting in a given load/RPM zone you have to do some or all of richening the mixture, retarding the ignition or reducing the boost. This will usually result in a loss of torque in this zone, unless there is a way of finding a combination of fuelling, timing and boost which results in more torque. This may occur if for example the boost was very conservative indeed for the turbo fitted (say 6 PSI for example on a turbo that is far more capable) but the timing was very aggressive. Reducing octane could cause detonation, but you may be able to get more back by increasing fuelling and boost and retarding timing. It all depends on the individual spec of the car. Rarely do you find on a modern car that there are massive reserves out of the box that can be exploited by mapping. Cost limitations are obvious, engineers also don't put a 500 BHP capable turbo and intercooler on a 200 BHP engine because the car would be slated for being laggy. What you give away in one department you can gain in another, or conversely you can reach situations where it is all lose-lose - for example trying to run too much boost and weak fuelling with retarded timing can result in a very hot, poorly performing engine.

In general, with accessible fuels on turbocharged cars running any decent level of boost, you will always lose power for a given octane if you are mapping optimally in each zone.

Rather than kill performance by mapping to a lower octane level which is always very depressing, why not think about other ways around the problem - eg bigger turbo, intercooling, water injection, better breathing etc.

Turbocharged engines running any decent specific power output hate 95 RON. It is very demoralising mapping them, but it can be done.

[Edited by john banks - 11/07/2003 23:26:44]

Hanslow

Thanks John

Just wondering if it was possible, which from what you say it is, but probably just better off going down the proper fuelling route and fork out for 97+

Was thinking about possibly getting a turbo MR2, and wondered if it could be detuned to just run on normal 95 unleaded without much hassle, but with the obvious loss in power. I thought it might simply be just ECU stuff which could be remapped with no issues other than power loss.

Cheers

Steve

greasemonkey

Look at it this way:

As John says, if you're going to remap for the lower octane rating, the fuel maps will most probably need to be enriched. Thus, you're going to burn more of the stuff.

Ergo, while 95 RON is cheaper by the litre, you're very likely to end up using more of it than you would SUL or Optimax. How much more of it would you need to use before any cost savings are wiped out?

To be honest if your primary reason for asking this question is one of fuel cost, the only turbocharged cars you should be considering are diesels! At end of day, any quick car is going to go through petrol, and, IME, using decent SUL or Optimax more than justifies itself.

Hanslow

Cheers, just one of my hair brained schemes I was wondering about .....

... I'll stop wondering now

Thanks guys