I am quite confused as to what the negative and positive numbers in the start of injectionmaps on my edc16C34 bosch ecu.

for example at 4500 rpm @ 50mg/stroke of fuel the map reads -26.51???

This surely means 26.51 before top dead centre and not after top dead centre as it relates to Crank Angle Degrees???

Please can somebody help as I have turned egr off and the timing needs retarding in the egr area. Therfore on screen shot attached between 6.80 - 28.20 you will notice positive values which must mean atdc crank angle degrees so i must make those figures smaller???

Or am I totally wrong as usual???


Please help me lol!

Many thanks

SOI values are BTDC.
If you take negative values as a reference, then the positives one are ATDC.
If you want to retard soi in egr area, you need to increase positive values.
I am not sure if it is a good idea.

Thanks for your reply mate.

I thought that - are btdc and positive atdc.

My egr is now off and the engine seems like its pinking on low throttle, is this the egr to far advanced or retarded?

I would say too far advanced so I need to retard the timing in the egr area e.i where the positive figures are a postive number (15)
Any help much appreciated.

The soi is retarded because of the egr gasses but now there are no egr gases so does soi need further retarding? This is the million dollar question?

You will kill your engine in no time.The SOI are RETARDED because of EGR, not advanced.Also DO NOT ADJUST SOI with more than 2 degrees, never,ever!!!

Thanks Major,

I will not alter them more than 2 degrees thank you.

So to get this clear can I retard the engine more in egr area by say 1 degree?

Zaccyboy wrote:So to get this clear can I retard the engine more in egr area by say 1 degree?

Am I speaking french, chinese or ?
As i told you.SOI are retarded because of EGR.Once you remove your EGR and give high values, YOU NEED TO ADVANCE YOUR SOI IN THIS AREA,NOT RETARD IT (IT'S BEEING ENOUGH RETARDED BEFORE YOU) BECAUSE YOU HAVE NO MORE EGR AND NEED SOME SORT OF POWER AND FUEL EFFICIENCY AND THAT'S WHY YOU NEED TO ADVANCE WITH UP TO 2 DEGREES.

Sorry I dont really understand egr I am new to this sorry! :oops:

No need to be sarky mate I am trying to learn thats why I am asking these questions and why I have joined this forum so members like yourself can help out noobs like myself :thumbup:

Would you recommend to alter just the egr area of the map and leave the rest of the area.

I have attached the soi maps and original map that I have identified with help from a kind member on here- what map relates to what is it engine coolant temperature if so where is the map that selects the maps depending on engine coolant temp?

Any help greatly appreciated!

Many thanks and sorry for all the questions just trying to learn :clap:

With EGR open, less oxygen enters a combustion chamber as if it would with EGR closed. Therefore start of ignition is more delayed as if there would be more oxygen.

On the other hand, air mixed with exhaust gases are warmer as if there was only intake air, so start of ignition is less delayed as if the EGR would be closed.

Anyway, less oxygen also means slower combustion process, so with EGR active, ignition delay is still longer than with EGR closed.

That means you should RETARD SOI with EGR closed.

But becasue an ori file is a very good and optimised compromise of settings for the cleanest emmissions possible, you could still advance SOI a bit in mid-range to get the best efficiency possible (but with more NOx in exhaust and far more work for a catalyst converter) and lower fuel consumption for a bit...

...but because you get start of ignition advanced a bit just by closing the EGR, if the rest of software is left in original state and you have no intention of doing a whole bunch of dyno runs while trying different SOI setups, then a very good option is to leave SOI maps intact.

I know, seems funny. :mrgreen:

But it's not. :geek:

p.s.: you get a lot more NOx also because of a closed EGR.

Thanks Zoc much appreciated 8-)