Emerald base maps

[Lesliehedley]

Does anyone have a base map for an Emerald ECU to run a standard 400SE? I was given a base map by Emerald but I can't help thinking the ignition map is backwards. The advance starts low at idle and gradually builds towards the higher load sites. I thought that just above idle on small throttle openings you got high advance that gradually decreased as the throttle opened to full throttle. Isn't that what the vacuum advance is for? to produce high advance on small throttle openings? Can anyone help or suggest typical advance figures for various loadings and revs. P.S. I don't have a vacuum advance, the ignition is all done by the Emerald. I wonder if the map they sent me was from a car that used the distributor to trigger the ignition and still had vacuum advance. That would make the map settings much lower at low load sites. I think I've just figured that out. But I could still do with some useful figures to try, or a map if anyone is running a similar setup. Thanks for any help and sorry about the long posting.

[ed_crouch]

Hi.

The dissy gives you 2 sources of advance. Vacuum, and centrifugal.

Total advance is the sum of these 2 at any point on the Throttle Vs RPM map.

You'll start off with about 8-10 degs at idle, and as you say, as the throttle is opened a small way, the vac advance rises up, and as the throttle goes to full, it wil back off again. This is because a weaker fuel mixture burns more slowly, so you'll have to set fire to it earlier to acheive peak cylinder pressure just after TDC (i.e. longer lag-time).

As you get towards full throttle, the ECU starts bucketing fuel into the engine, youre hopefully hitting 14.2 AFR, and the vac advance drops off as the charge is now burning more quickly cos its richer. Reduced lag-time, so it gets ignited a smidge later.

The other source of advance is your centrifugal advance. This increases as engine RPM increases. The bob-weights in the dissy begin to push outwards against the springs (one will be loose when stationary, the other slightly tight: this gives the required curve rather than just a straight line which will not work for normal RV8).

The lag-time is simply the time it takes between spark and peak cylinder pressure. AFAIK peak cylinder pressure wants to be just a gnats nadger after top dead centre in order for the piston to feel as much pressure as possible for as much of the power stroke as possible. There is a constant amount of time taken for the charge to develop peak pressure after its been ignited. Whether the engine is doing 6kRPM, or 1500RPM, for a given AFR, the lag time is constant.

Hence, as the engine spins faster and faster, we still want to spark X milli-seconds before it hits TDC, and hence we need to gradually increase the number of DEGREES advance: the engine rotates thru that number of degrees faster and faster as it accelerates.


Oh god, Ive carped on again havent I...

Sorry! Still, thats everything I know about advance, and hopefully if any of it is educational, it might help you...

Ed.

[combine]

I will volunteer you Ed for a tech talk at the next fest or did I miss it a this one ?

[rev-erend]

Ed,

Blimey - you know you stuff.. or are you reading from a book

Lesley - 2 choices - either contact (Leoni) at Emerald .. or you could email 350Matt on PH as he runs emerald.

Mine is still on order .. blimey they take a long time.

Edited by rev-erend on Tuesday 14th August 09:49

[TVRleigh]

Other option you could speak to the people who are using mega squirt, as they do there own maps.
and a Map sould be a Map if you get me.

[rev-erend]

Leigh,

That is partly true for the ignition map but with the Emerald you can choose the RPM setting for each load point .. and you can have 'more or less' as many as you like..

So you can bunch them up for the drivability area for instance (more useful for the fuel map)..

[TVRleigh]

Is the Emerald the best ECU you can get or is there better.
Also how much better is the Emerald compared the the Mega.

Sorry to take it a big of topic.

Thanks
Leigh

[rev-erend]

I think it's pretty good..

Quite like the MegaSquirt but the focus of the product is on the building of it.. and it does not seem to have the user friendly interface / features that Emerald has.

Others like DTA and Omex also seem to be good - a bit more expensive but all have similar features.

[ed_crouch]

Rev, not reading from a book, but I do have a couple of damn good reference books:

Hilliers fundamentals of motor vehicle technology

They cover just about EVERYTHING, and theres a dedicated book for powertrain electronics. It covers just this sort of stuff, and its thoroughly recommended.

Main book:
http://www.amazon.co.uk/Hilliers-Fundamentals-Moto...

Engine management etc:
http://www.amazon.co.uk/Hilliers-Fundamentals-Moto...

Ed.