Injectors and Spark Timing Relationship

[Isaiah48]

My question is just how much do different size injectors play a part in the amount of Spark Timing you can run. I run a pretty big cam in this car and previous to upgrading my injectors I could run as much as 23 degrees of timing at WOT at 7,000 rpm, now I cant run more than 17 degrees...

Can the injectors amke this much difference in the amount of timing you can run?

I'm assuming it is probably the fact that all I did to setup these injectors was rescale the Flow Rate vs KPA to 48# at 58psi. I know I probably need to do more in the line of tuning such as modifying the Short Pulse adder and Min Ijector Pulse but I'm throughly confused as to how to go about it. I've read quite a bit on it in here and haven't been able to get my head around as yet. Any to the point help would be appreciated...

The injectors I used are: Delphi/Lucas 42# High Impedence Fuel Injectors
http://www.thunderracing.com/catalog...oduct&pid=3645

I edited my past timing from 29 to 23 degrees...

[madvette08]

My question is just how much do different size injectors play a part in the amount of Spark Timing you can run. I run a pretty big cam in this car and previous to upgrading my injectors I could run as much as 29 degrees of timing at WOT at 7,000 rpm, now I cant run more than 17 degrees...

Can the injectors amke this much difference in the amount of timing you can run?

I'm assuming it is probably the fact that all I did to setup these injectors was rescale the Flow Rate vs KPA to 48# at 56psi. I know I probably need to do more in the line of tuning such as modifying the Short Pulse adder and Min Ijector Pulse but I'm throughly confused as to how to go about it. I've read quite a bit on it in here and haven't been able to get my head around as yet. Any to the point help would be appreciated...

The injectors I used are: Delphi/Lucas 42# High Impedence Fuel Injectors
http://www.thunderracing.com/catalog...oduct&pid=3645

Hi,

Do you have a scan file that you can post and your tune file?

Ian

[Isaiah48]

Hi,

Do you have a scan file that you can post and your tune file?

Ian

I edited my first post to include my current log and tune.

[madvette08]

Im having a look at your scan and tune file. What is stopping you from running 23 degrees of time, are you getting a lot of knock? I did find one problem that is the power enrichment delay rpm is set to 4500 rpm and it should really be set to 0 rpm.

Ian

[Isaiah48]

Im having a look at your scan and tune file. What is stopping you from running 23 degrees of time, are you getting a lot of knock? I did find one problem that is the power enrichment delay rpm is set to 4500 rpm and it should really be set to 0 rpm.

Ian

Yes knock is the issue, I"ll make that change and see if I can run more timing. Thanks

[EC_Tune]

Although that limit is in there, it's really not actually used on the Corvettes. The TPS setting is the major influence on when PE takes effect. You're entering PE <0.2 seconds after the TPS requirement is made.

And no, changing injectors should not skew your spark tables if the injector calibration is correct.

[RWTD]

As usual, Doug is absolute correct!

[Isaiah48]

Although that limit is in there, it's really not actually used on the Corvettes. The TPS setting is the major influence on when PE takes effect. You're entering PE <0.2 seconds after the TPS requirement is made.

And no, changing injectors should not skew your spark tables if the injector calibration is correct.

I think the injector calibration needs work then, I only changed the "Injector Flow Rate vs KPA VAC" to set up these injectors. If someone could help me with settting these up I think it might resolve my issue...

Again my first post has the injectors I put in for reference.