038 | Configuring and tuning acceleration enrichment on a Link G4+

Hello Andre,

I am trying to set up accel enrich on motec m800.It's an older ECU type and it's more difficult to understand some parameters on it.So I have some questions for you:

1)Miscellaneous Setup->1 for TP

2)Accel Threshold->50 units/sec(Is it the same as the 0.5 TP for Deadband?)

3)General Setup->Fuel->Setup->Fuel Accel Mode 0(for enrich on accel)

4)Fuel->Accel Enrich->Fuel Accel Clamp(% of IJPU)->A map that has to be tuned like you did on the webinar

5)Fuel Accel clamp comp->0 unless I want to compensate anything like temp

6)Fuel Accel decay.Here is my main problem.You used 80% but on motec the default value is 5.0 (% of IJPU/Rev).Can you help me with that because I cant understand what value I should enter on that table.

7)Fuel Accel sensitivity->It contains the default values and as you said on the webinar I will not need to change the default values a lot if the main fuel table is correctly tuned.

8)What about decelaration maps?Do I follow the same procedure?From 100% throttle to part throttle and to check the lambda again?

9)What about acceleration advance?

Thanks a lot mate

2. The accel threshold could be considered a deadband. It prevents any accel fuel being introduced if the rate of change of TP is less than the threshold.

3. You would want to be using mode 0

4. The clamp table defines the maximum amount of fuel that will be applied under an accel event. This works in conjunction with the sensitivity table.

5. You would normally add a comp based on ET so the response is crisp when the engine is colder.

6. This dictates how quickly the accel fuel will be removed. You can adjust this based on the input from your lambda sensor. If the initial response to throttle input is good but then the lambda tracks lean, you can reduce the decay. If on the other hand the enrichment is initially good and then drops rich you could increase the decay. Start with the recommendation of 5% IJPU/rev

7. As above, the sensitivity and clamp work together. None of the accel parameters can be tuned until the main fuel table is accurately calibrated.

8. Decel enleanment is essentially the opposite of accel enrichment. All of the same options are available to help reduce the richness after a throttle lift.

9. In my experience I can only think of two cars where I needed to retard the timing during tip in. Unless you have an engine that knocks during accel you shouldn't need to worry about this function.

Your reply Andre is more than helpful to me.Thank you very much mate

Would direct injection engines need Accel enrichment ?

That's a great question. Considering what is going on with wall wetting which is the driving factor behind the requirement for accel enrichment, you would think that DI would be immune to this need. My experience here is limited as the only DI engine I've tuned on a standalone ECU is the FA20 (which is an oddity due to the PI/DI system) which does seem to require accel enrichment even when solely running DI.

I'll go out on a limb and assume that there is still some fuel wetting involved with a DI system but instead of the port this becomes potentially the bore and piston. I'd also guess that the requirements would depend on the injection timing, injection volume and the spray pattern and aim of the DI injector. I don't have sufficient experience with dedicated DI engines to confirm further at this point sorry.