Difference between sequential and batch fire fuel table values?

[Mechanicaldan]

We ran a DTA ECU last year, that only allowed us to run batch fire with the fuel injectors. We have the AEM ECU this year, and have our engine running with last year's parameters.

How do the fuel map values differ when going to a sequential fuel injection, assuming same injector size and fuel pressure?

I think I see a problem with multiplying a value of 12 ms by 4 for the sequential map. If in the batch fire system, the injectors are fired 4 times during 720 degrees, why I don't sum the values and use it when the fuel injector gets fired 1 time in 720 degrees?

Cyclone Racing
www.cyclone-racing.com (http://www.cyclone-racing.com)
Iowa State University
Project Director

[Mechanicaldan]

We ran a DTA ECU last year, that only allowed us to run batch fire with the fuel injectors. We have the AEM ECU this year, and have our engine running with last year's parameters.

How do the fuel map values differ when going to a sequential fuel injection, assuming same injector size and fuel pressure?

I think I see a problem with multiplying a value of 12 ms by 4 for the sequential map. If in the batch fire system, the injectors are fired 4 times during 720 degrees, why I don't sum the values and use it when the fuel injector gets fired 1 time in 720 degrees?

Cyclone Racing
www.cyclone-racing.com (http://www.cyclone-racing.com)
Iowa State University
Project Director

[B Lewis @ PE Engine Management]

Hi Dan,

Where did the 12 ms come from? Was that just a general example, not specific to your engine I hope?

Your assumption about adding up the total "on time" per cylinder is mostly correct provided that you take into account exactly what units each of the systems is using (ms/rev, ms/inj firing, ms/cycle, ???). The only wildcard in the equation is the dynamic response of the injector. A batch fired system will need to stay "on" longer than a sequential system to get the same flow because it takes a finite amount of time for the injectors to get to the fully open position. Hope this helps.

Brian Lewis
Performance Electronics, Ltd.
www.pe-ltd.com (http://www.pe-ltd.com)
"Complete Engine Management Systems for $798"

[Dan Deussen @ Weber Motor]

I assume your old batch fire system fired a pair of injectors every 180 degrees of crank shaft revolution:

cyl # 1 --- 2 --- 3 --- 4
0deg on off off on
180deg off on on off
360deg on off off on
540deg off on on off
720deg on off off on


where on a sequential system with firing order 1-2-4-3 it would look like this:

cyl # 1 --- 2 --- 3 --- 4
0deg on off off off
180deg off on off off
360deg off off off on
540deg off off on off
720deg on off off off

To get you started you should be able to just take your batch injection values and double them to put in the sequential system. This should at least get your engine running somewhat okay.

I hope this helps.

Daniel Deussen
www.walbro-italy.com (http://www.walbro-italy.com)