exhaust change on fuel injected bike

hey guys. I am not sure how smart DFI on my GPZ is.... I understand that on a bike with carbs, you must rejet if you change the exhause.

my GPZ has DFI, if I change the exhaust, do I need to anything to the injection system? will it automatically detect a change and adjust?

Yep:) That is the beauty of the system. On my first GPz, I'd run straight pipes at night (when I was drinking and bar-hopping) and during the day, just slide the muffler back on the Kerker. I was too young and stupid to realize I should have been doing it the other way (straight pipes when I was sober). :woohoo:

i guess the good is that everyone could hear you and avoid you.... bad thing i suspect is that the cops could also very easily hear and find you....

did you run any kind of injection cleaner in your gas? my engine was sputtering this morning on the way in, I am thinking I need to check and probobly change the fuel filter, airfilter, and was hoping that it would not be somthing that would involve the dfi...

To answer your question first, no I never ran any injector cleaners through the system. The system ran well virtually all the time. However, the few times that I did get hesitations, they were due the DFI trying to continually adjust fuel/air mixtures while I was literally blowing the packing out of my Kerkers (and not realizing it). You also might just check the balance on your injectors (same as carbs).

that would make sense. In another thread I have talked about my kerker issues. (basically spit out the cap and all innards as I was moving down the highway). I have a cap on the kerker now that was not designed for my can.... occasionaly my dfi light will blink but only intermittantly, and the hesitation is ussually during accelleration or decelleration.

I am still looking for a suitable replacement for the kerker(that is reasonably priced)

Nope, the fuel injection system is not going to automatically compensate for the exhaust changes, now if you had an airflow sensor (and I don't believe the B2 does) then it would compensate for additional airflow.

When Kawasaki did away with the airflow sensor they went to the Alpha N system, at X rpm and X throttle position and X engine temp at X intake air temp then inject Y fuel. No MAP or Airflow sensor so the engine load is calculated based upon those parameters.

Some newer bikes use a MAP sensor for idle and low rpm, then switch to Alpha N at a certain point.

I just realized that you have an 83 GPz1100, and it does not have an airflow sensor, so nope, it's won't compensate.

Post edited by: steell, at: 2006/04/06 16:12

Well, not to be argumentative, but I went from a stock exhaust to a Kerker on my 1982 GPz1100 and made no adjustments to the DFI system. After installing the Kerker, I would occasionallly remove the muffler and run with the collector only. Never made any DFI change then either.

steell wrote:

Nope, the fuel injection system is not going to automatically compensate for the exhaust changes, now if you had an airflow sensor (and I don't believe the B2 does) then it would compensate for additional airflow.

When Kawasaki did away with the airflow sensor they went to the Alpha N system, at X rpm and X throttle position and X engine temp at X intake air temp then inject Y fuel. No MAP or Airflow sensor so the engine load is calculated based upon those parameters.

Some newer bikes use a MAP sensor for idle and low rpm, then switch to Alpha N at a certain point.

I just realized that you have an 83 GPz1100, and it does not have an airflow sensor, so nope, it's won't compensate.<br><br>Post edited by: steell, at: 2006/04/06 16:12

If I am not mistaken you may need to modify what I think is the fuel pressure regulator. There is a way in which it can be modified from a set position from factory to adjustable. Not very familiar with the fuel injection system on the GPZ'z but I worked at a wrecker and their mechanic used to charge 60$ to modify the part. I seem to recall seeing something out on the web about it too. This post will sure to prompt an applicable guru to correct me or exp-and properly.

Well, not to be argumentative, but I went from a stock exhaust to a Kerker on my 1982 GPz1100 and made no adjustments to the DFI system. After installing the Kerker, I would occasionallly remove the muffler and run with the collector only. Never made any DFI change then either.

That's understandable, you simply never exceeded the range of the current programming, so it's still injecting the same amount of fuel. Get the head ported and run pods and see what happens

It's easy to refute my statement, just show me how the computer determines airflow, if the computer can not measure airflow then how does it know it needs to compensate for the additional airflow?

Electronic fuel injection is a hobby of mine, and I enjoy arguing, so do your best

steell wrote:

That's understandable, you simply never exceeded the range of the current programming, so it's still injecting the same amount of fuel. Get the head ported and run pods and see what happens

It's easy to refute my statement, just show me how the computer determines airflow, if the computer can not measure airflow then how does it know it needs to compensate for the additional airflow?

Electronic fuel injection is a hobby of mine, and I enjoy arguing, so do your best

Well, if the bike never exceeded the range of the existing programming with a set of Kerkers and ran the same, isn't that what I said regarding changing any of the DFI parameters?:blink: It apparently didn't matter whether you are running stock or aftermarker exhaust (they are both within the range of the programming...which is what the Kawasaki dealership said when I went to Kerkers in 1983. Besides, in those days, the technology wasn't there to re-map. Nothing else was changed...airbox was stock. When I went with the Kerkers, I wasn't after performance enhancements (and it ran the same, with or without an aftermarket exhaust), merely looks and I wanted it to sound faster:laugh:

let me add my ride home yesterday experiance to see if this gives more fodder for the fire....

the bike 83 GPZ1100a started and ran great for about 10 miles.... then would stutter, not hold idle and then totaly quit.... I pushing my way out of the intersection after stalling at the light. I after it sits for about 10 min. starts right up and runs great... for about 3 more miles and then I start to bog again... runs like crap the rest of the way home, about 6 more miles... almost did not make it up the the bridge next to my house. the DFI light did not blink at all this time, however my battery light did.... if I have a low battery will this affect the injection system or the ignition? The gas tank is full, oil level is good, all headers are hot (hot as they should be anyway..) just trying to give the circumstances. I do have a leak at the valve cover (this was giving the smoke from the headers that I mentioned in a previous post)... any ideas?

Most Fuel Injection computers will shut down when the voltage is around ten volts, so if you have a charging system problem it is entirely possible for that to happen, "But" you said the bike restarted after a few minutes so obviously the battery had enough juice to cramk it over, so the battery must have been above 10 volts.
I suspevt an electrical problem, probably an intermittent short or open, either one could reduce the voltage to the computer. I suggest check all grounds and making sure you dont have a wire shorting out against the frame. A good ground is critical for an EFI system, the injectors have power applied any time the key is on, the computer controls the injectors by controlling the ground (- wire), it opens and closes the injector ground wire to turn the injector on and off. A bad ground on a computer controlled vehicle (motorcycle or automotive) will drive you nuts