Injector duty cycle over 400%

[All4wd]

I have a Jeep CJ7 with a slightly modified 258ci 6 cyl with a Howell EFI system. I thought I read that the injector duty cycle should never go over 85%. In this engine it is consistently over 100% and in the higher rpm ranges (2800-3200) and higher MAP values (70 -90) I have logged over 400%. In this higher range the engine stumbles and I assume it is due to the injectors being very unhappy with the work load. The fuel pressure never drops from 12 psi and volume test of the pump showed approx. 42 gph. According to Howell this is within specs. This EFI kit reportedly uses the injectors from a 4.3 engine. It would seem the injectors can't flow enough fuel. Can they be too small for this application? Any guidance here would be greatly appreciated.

[Six_Shooter]

It's a calculation error.

To have a DC of truly over 100%, would require bending space and time.

You may be maxing out the injectors or you may just not have the tune close enough in the upper RPMs. What is the injector PW (pulse Width) when the stumbling occurs at what RPM?

[EagleMark]

If your using TunerPro? We fixed the Injector Duty Cycle calculation. May want to update your file to $42-1227747-V5.2.adx
http://www.gearhead-efi.com/Fuel-Inj...Information-42

Or read the numbers on injectors to make sure they are correct.
http://www.gearhead-efi.com/Fuel-Inj...d-part-numbers

There are a lot of other possibilities with conversions or even stock applications, like fuel pressure dropping off at higher RPM.

Can always attach a data log so we can analize.

[All4wd]

I am using TunerPro and using the current $42-1227747-V5.2.adx file and the current $42-1227747-V5.9.3.xdf file. This is the current log and bin I am using. Still stumbles in the 2800-3200 range in the 70-90 MAP range. I don't see a log value for pulse width. I have a fuel pressure gauge on the Jeep as I drive and pressure never changes.

[All4wd]

Also, I am not using the spark control, just vacuum and mechanical advance. It has and EGR but it also is mechanical.

[EagleMark]

Also, I am not using the spark control, just vacuum and mechanical advance. It has and EGR but it also is mechanical.

Not using spark control is a big mistake, but can be done. Not sure why anyone still does that?

Mechanical EGR? It's not turned off correctly in bin, so I'm not sure if it's always on or off? But BLM fueling looks good in history table.

Error code 13 for O2 sensor is disabled so we don't know if it works right. Looks OK on data. Not sure why it is off?

IAC does not seem to be working correctly, it never opens up up high RPM, usually the throttle follower opens IAC for extra air at RPM. And there is no IAC counts at idle so no ECM control of idle.

None of that really matters though as the mask ID has been changed to AA to disable checksum AND you have an Error code 51. So nothing in data counts as correct. There is also a error 33, but the big part that effects data is you are in ALDL mode. No need for 10k switch on cable to be on to record data in these.

So clear codes and record some data again without the 10k switch on cable.

Injector Duty Cycle is calculated by BPW, so it's not correct. This does not work with stock chips until the patch or hack is applied to bin to replace that part of data stream with this information.

The bin looks to be a V6 bin with some changes, only 144 bytes to entire bin, most of which is the VE1 fuel table. It runs Async fueling all the time, I've found running a SYnc fuel bin is a huge improvement to these I6 engines because of the long unheated intake runners, they just get soaked when idling and low RPM off roading. BLM history shows good though and all within ball park of O2 sensor Closed Loop feedback.

So I don't think your original issue is fuel related with data I can see. What is the drivability issue that you are looking for?

[All4wd]

I am trying to reply to your last post in a format that can be understood. When I press "enter" on my keyboard it does not drop down to a new line/paragraph. What am I doing wrong? I feel like an idiot, I have never had a forum do this before! Everything can only be typed in a run on paragraph with no separation.

[ony]

need to apply bpw an spark advance hac in the scalers.

[All4wd]

If it matters at all I am using the Moates autoprom and emulation. Thanks ony, applied the bpw hac but I am not using spark advance. Does that matter?

[ony]

probly not I never had any dealings with your dizz setup.

[ony]

in your #2 ve table I would add 5 or sow where thay have 20.

[EagleMark]

I am trying to reply to your last post in a format that can be understood. When I press "enter" on my keyboard it does not drop down to a new line/paragraph. What am I doing wrong? I feel like an idiot, I have never had a forum do this before! Everything can only be typed in a run on paragraph with no separation.

Go to Settings at top right of page, scroll down to General settings and click, then look for

Message Editor Interface:
Enhanced Interface - Full WYSIWYG Editing
Basic Editor - A simple text box
Standard Editor - Extra formatting controls

It's probably set to Enhanced and your PC does not have some Java updates. Choose Standard or Basic.

[All4wd]

Not using spark control is a big mistake, but can be done. Not sure why anyone still does that?

If it were mine I would integrate this. This is a customer of mine and I am just trying to fix his drivability problems of stumbling at high RPM/load and smooth the idle out a little.

Mechanical EGR? It's not turned off correctly in bin, so I'm not sure if it's always on or off? But BLM fueling looks good in history table.

Vacuum operated EGR. I don't know how to turn this of in the bin but would it matter if it is not being used?

Error code 13 for O2 sensor is disabled so we don't know if it works right. Looks OK on data. Not sure why it is off?

I don't know why this is either, I turned it back on though

IAC does not seem to be working correctly, it never opens up up high RPM, usually the throttle follower opens IAC for extra air at RPM. And there is no IAC counts at idle so no ECM control of idle.

I noticed the idle was a little high and I couldn't seem to get it to come down so I thought I would take it one step at a time and deal with this later. Any suggestions would be appreciated

None of that really matters though as the mask ID has been changed to AA to disable checksum AND you have an Error code 51. So nothing in data counts as correct. There is also a error 33, but the big part that effects data is you are in ALDL mode. No need for 10k switch on cable to be on to record data in these.

Should I change the mask ID to enable checksum? I must admit I don't know what that does other than what I googled. Is it just the computers way to check for errors in the data?

So clear codes and record some data again without the 10k switch on cable.

Attached a new log file with the 10k switch off but forgot to clear codes before this run. It would seem things have move more towards the lean side with this log.

In this log I enabled the BPW and I think the injector duty cycle fell in line now.


The bin looks to be a V6 bin with some changes, only 144 bytes to entire bin, most of which is the VE1 fuel table. It runs Async fueling all the time, I've found running a SYnc fuel bin is a huge improvement to these I6 engines because of the long unheated intake runners, they just get soaked when idling and low RPM off roading. BLM history shows good though and all within ball park of O2 sensor Closed Loop feedback.

How do I change it to sync fueling? This Jeep does have a heated manifold via heater hose traveling though the manifold.

So I don't think your original issue is fuel related with data I can see. What is the drivability issue that you are looking for?

The whole reason for this endeavor was to get rid of the stumbling at high RPM / loads and smooth the idle if possible. According to my customer, this Jeep has had this problem since he put the Howell EFI system on in 2001! The only things different than a stock Jeep 6 cyl, is that it has a Clifford Intake manifold, headers and an RV cam.

When it came in the O2 sensor was very close to the header collector leading me to believe it was sampling only 2-3 cylinders. I moved it about 6" downstream of the collector but it made no difference.

The heater hoses were routed incorrectly and the ECM temp sender never saw more than about 160 degrees. Fixed that, no improvement.

.75 volt difference between battery voltage and ECM voltage. Fixed that, no difference.

Checked fuel pressures and volume. 12 psi with no drop at high RPM. Checked fuel pump volume capacity - 42 Gph.

Checked for proper vacuum advance and mechanical advance and they were in spec (it has been so long since I checked this I forgot what spec was)

I have tried different ECM (with same prom) and different ignition control modules - no change

I figured it had to be in the tune, so here I am. It is long past the point of making any money on this repair as I have countless hours into this and the learning curve is too steep. I just want to make an improvement and not run away from this with my tail tucked.


P.S. Thanks for the settings info, that worked!

[Six_Shooter]

There's one thing you haven't done, and it will help both idle and upper RPM/load.





Integrate the spark control.

Also how is the vacuum operated EGR being controlled, that could be a LARGE part of the issues right there, if it's opening at the wrong times.

[All4wd]

Doh!! My mistake, working on too many Jeeps at once. NO EGR on this one, sorry!

Thanks Six Shooter, you made me look again.

If I thought adding the spark control would surely solve this, I would do it. It just seems that every other Jeep I have this system on doesn't have this problem or spark control.