Injector Offset

[mystery bird]

I purchased some Bocsh 33# flow matched injectors and changed my injector constant to match, where do I find the correct injector offsets for these injentors? or do I just leave them stock?

[n0dih]

You would need to contact the supplier for those injectors to let you know what they are.

If they are OEM injectors, find the application they came from, look up a cal from it, then you can find them pretty easy.

GM L67 V6's (Buick 3800 Supercharged) had 36 lb injectors. Delphi or Bosch, forget which, think Bosch though.

What is the PN on the injector?

Originally Posted by mystery bird

I purchased some Bocsh 33# flow matched injectors and changed my injector constant to match, where do I find the correct injector offsets for these injentors? or do I just leave them stock?

[mystery bird]

BOSCH PART # 0280150431, I looked on Stan Weiss' site but I don't see offsets anywhere.

[Programmer]

The table offsets are 'voltage' vs...manifold vacuum.

So if your vehicle has an 'unstable voltage', which most don't--you shouldn't have any issues. I know some people 'preach' offsets like it's gonna save their tune, but in reality--if your car doesn't have a stable operating voltage, you've got other issues that need attention.

[mystery bird]

That's the answer I was looking for, thank you.

[Team ZR-1]

'unstable voltage' is not the issue, Ohm's Law is

The PCM has to consider all conditions that effect voltage, resistance and temperatures that effect the latency of the coils in the injectors.

Start with engine startup, there is no alternator output thus cold cranking the voltage is lower and that effects how long the injector coil reacts.

Cold weather has different voltage effects then hot weather, add current loads, ie, is headlights, A/C, fans, radio, etc, on or off effects voltage loads.

Add the electrical system today is too small for the amount of electronics in cars today ( thank Japan for their normal crap in delaying 48 volt systems) and smaller gauge wire to safe weight and it all effects voltage levels.

In 2003 GM had to use a higher output alternator in the Corvette thus the voltage levels are different from one model year to another.

As seen here, LS2, LS7 and LS9 - even though the injectors are from the SAME vendor and only the flow is different you see below that they all have different offset voltage delay times



Now add a total unknown of 3rd party vendor and not knowing the latency times and you can bet using the stock GM values will cause injector to be commanded at the wrong time and incorrect pulse width on times

I have seen incorrect offset values using 6-9% more fuel then really needed and lost cylinders due to injectors flowing too late to when sparkplug was commanded on.

There is a big difference when even at idle with full current loads when voltage is at 12.5 versus 14.5
Add load changes with a supercharger and there will be a voltage difference.

As shown before a ton of testing I did with captured data results at

http://www.teamzr1.com/ubbthreads/ub...er=3147&page=1

The injector voltage offset delay existing and having many values in it's table was not put there for no reason and makers of fuel injectors do not state where the offset is for no reason

[mystery bird]

Wow...I liked the answer Programmer gave better. Now I'm back to not sleeping at night again. Seriously though team ZR-1 thank you for the in depth explanation. I emailed the company that sold me the injectors and asked for the offsets, the reply was "1.5% or less." That doesn't make any sense to me. I found by the part number that these injectors came from a 2000ish Saab turbo. Guess I'm back to searching the web again.

[mystery bird]

I can't find information about injector offsets anywhere, not even a formula to make a calculated guess. I suppose that is why most people leave them alone.

[n0dih]

Contact the supplier, see who made them, the PN and ask them for the info, they should have all the data.

Originally Posted by mystery bird

I can't find information about injector offsets anywhere, not even a formula to make a calculated guess. I suppose that is why most people leave them alone.

[Programmer]

I'm sorry...are we talking 1995 LT1 or 2010 Corvette ?