I am using the Bosch 280 155 868 design 3 injector on my new build and am having trouble finding the low PW and battery offsets.

These are commonly refered to as 36# injectors but Bosch rates them at 34.5# so that is what I am using as my IC. I'm running 43.5PSI vac disconnected. I have found 1 listing on the net so far but my motor is running super lean with it. I can tune to it but would like to know if it's right first. It has been difficult to find any good info.

 

I believe they are published by Bosch. Check theirr website.

GearHead EFI may have them at their site. I recieved my offsets from FIC when I purchased injs.

 

Injector Data Sheet: 280-155-868, 34 #/hr Skinny

Fuel Pressure: 44
Flow rate: 35.5 #/hr
Minimum PW @ 44 psi: 729 usec

Offset Compensation versus Battery Voltage:
6.4 Volts: 3105 usec
8.0 Volts: 2046 usec
9.6 Volts: 1521 usec
11.2 Volts: 1204 usec
12.8 Volts: 970 usec
14.4 Volts: 785 usec
15.0 Volts: 752 usec

Short PW Compensation versus Pulse Width:
0.015 msec: -192 usec
0.244 msec: -152 usec
0.488 msec: -109 usec
0.732 msec: -67 usec
0.976 msec: -24 usec
1.220 msec: 0 usec
1.460 msec: 0 usec
1.708 msec: 0 usec
1.950 msec: 0 usec
2.197 msec: 0 usec
2.440 msec: 0 usec
2.685 msec: 0 usec
2.929 msec: 0 usec
3.170 msec: 0 usec
3.410 msec: 0 usec
3.660 msec: 0 usec
3.900 msec: 0 usec

RBob.

 

Thanks Bob. I looked and looked but couldn't find much.

Should I enter the negative values or zero out? I'm using the APYP bin as a starting point and the values are way different. I suppose for the multitec injectors.

 

Just zero out the short PW table, can't enter negative values.

RBob.

 

Ok on the short PW's- thanks.

I noticed using the batt offsets above my motor ran wayyyy lean in the lower airflow/rpm range. (BTW I'm currently running in open loop) so I tried raising the values around 12-13volts, but in the same proportion. I also had to raise the settings in MAF table 1 around idle. Seems to be really close according to wide band.

Am I going about this correctly or should I leave them exactly as recommended and change MAF tables?

My plan here is to get it close in open loop and then return to closed loop and see what happens. My previous attempts in closed loop get pretty close then seem to go hay-wire. I suspect it has something to do with the offset tables since I've changed injector type & size.

Any suggestions? Running open loop seems to give the best results so far. Smoother and more consistant. Although I really want to return to closed loop at some point. If I can't get there with this system I am planning to go EBL.

 

The offset compensation was likely higher for the Multec injectors. Which is why the lower PW areas are now leaner. Leave the correct values in the table and tune via the MAF tables.

Open loop does have advantages, such as a lack of proportional gains and being able to run on the richer side of things.

RBob.

 

I'm sorry Bob I said it backwards. The Bosch Pw corr vs batt made it run rich. I had to lower the levels down to the stock levels to lean it out. The stock tables were steeper and the Bosch offsets were more linear, although higher at "normal" voltage range. Regardless, I presume the recommendation is the same, leave the PW vs battery corrections alone (as provided) and tune with MAF tables.

 

Yes, same as before, use the correct offset values and tune via the MAF tables.

RBob.