I have a leaky injector and am thinking about replacing them with Bosch 24lb injectors instead of the stock set. Will I need the chip reprogrammed to the new injectors or will they work at the stock setting for now?TIA :cheers:

 

I'll take a shot at this one, the stock injectors are 22# in the 92 and 93 from what I have read. I'm not going to swear to this thought.

In tunercat the injector constant for the DA2 (92 bin) is 23.8.

What does all that mean???
If they are 22's and the constant is set a bit high already (to lean out the fuel) then the 24's will be rich, but the ecm should be able to ajust for them.

Now the only real way to know is to do some scans with datamaster or some other logger and see where the BLM's are after the new injectors.

Hope that helps, and if anyone has the size on the batch fire 92 and 93 LT1's please chime in :)

 

I have the same injectors and constant, it seems you add 1.8 to the base number. Probably some type of HEX conversion to keep the ECM constants happy and within a specified limit to allow for inductive pulse time reactions for the ECM to drive the injectors high and low.

I am speculating that because the injectors take time to open and close and the electrical time transients on the injectors lines, it's better to have the leaner release so that when the mechanical catches up with the electrical, and closes again that the overall release is a 22 lbs release.

I used to do this on a robotic machine that dispensed chemicals 24/7 and had to deliver 3 mL of chemical +/- .1 mL, the volume was off from source to load and electrically you had to allow for less to get more out of the nozzle. It was verified with a volume tube measurement for accuracy and weighed to ensure volumetric displacement and sure enough the electrical didn't jive with the mechanical due to inherent losses within the mechanical system, thereby, the "offset" factor was used to dial in the proper volume required for the application

I suspect that is what is happening here for the fuel injectors. I'm sure the engineers looked very very closely to find the right combination to get the injection time pulse width and release volumes correct. This is also done by the aftermarket guess who give you results of all eight of your injectors. X amount of time will release X amount of fuel, if not injector fails and is rebuilt etc etc

When I go to 26 lbs injectors for my SC I'll be putting the constant in of 27.8. Seems like you add 1.8 for the "production" settings and wire harnesses, and the dyno will determine the rest.

Hope this helps

Kitt

 

So I will more than likely run rich until I finally get a chip with all of the bs little things that I need done. Thanks fellas

 

:cheers:

 

Not exactly.
When your car is in closed loop the ECM/PCM will adjust for the larger injector size based upon the O2 sensor readings and bring your mixture back into factory spec. During startup cold idle and WOT (Wide Open Throttle) the ECM/PCM will is in open loop and you will be running rich. Startup and cold idle probably won't be different enough to notice. WOT accelleration may not be as crisp as before and may be noticable. If the old injectors were really bad, the improvement due to the new 24# units may make it feel better at WOT than it did.

 

I changed the 22lb injectors over to 24lb ones on my 91.
I program my own eproms BUT I didn't have to make ANY changes for the injector swap. I also have an AFPR and didn't have to make any adjustments or compensations in the FP for the 24lb injectors.
Cranked up and ran great. My Integrator and BLM values are still in spec.

BTW I used the FORD 24lb injectors

 

:iagree: :iagree:

 

Well i know i had my old 24#Bosch in my vette for about 4 months and they never gave me a problem in my 91 vette...my computer did fine and under NOS (150 wet shot) it did fine never ran lean always a little rich! but i know my stock was 22's and 24's i didnt see no different in idle or performance? i actually still have them if interested?

Thanks Kevin


[Modified by krivera, 2:45 PM 8/4/2003]