Does injector pop pressure influence ignition timing?

[Full Monte]

I've been thinking about injectors lately. If an injector pops at a lower pressure than the others, will the timing on that cylinder be more advanced than the other injectors? If an injector is installed in a low-compression cylinder, will the timing be more retarded?

 

[OLDBULL8]

I've been thinking about injectors lately. If an injector pops at a lower pressure than the others, will the timing on that cylinder be more advanced than the other injectors? If an injector is installed in a low-compression cylinder, will the timing be more retarded?

Low pressure pop: Say all the other 7 are at 1850 psi and one is at 1200 psi.

The injection time of that cylinder is determined like all the other cylinders. Depending on how low the pop pressure is, the "misting" would not be consistent with the other cylinders in HP output, and all the fuel injected would possible not be completely burned resulting in probably some black smoke. Injection time is in micro seconds. Say at 2000 RPM and 8.5 BTDC the injection time is 23 thousandth of a second. At a low RPM it would act like a miss.

Compression has nothing to do with timing. It would be more like a miss.

That's my thought's on your questions.

 

[icanfixall]

A cylinder with low or no compression will have the same timing as a cylinder that has plenty of compression. An injector pressure controls when fuel is pushed into that cylinder regardless of cylinder pressure. If any injector is loe on pop pressure it will be injected early. If one injector is poping higher than the others it will be injected late only id the timing was set by the cylinder that has a low poping injector. For the terminoligy used her early injection is advanced timing on that cylinder... And late injection in a cylinder is retarded in that cylinder. this is why we need all injectors to pop as close to being the same as we can get. Usually that 50 lbs. Some like to say 200 lbs is close enough... And Fram filters will work just like any other filter.....

 

[Full Monte]

Thanks! I'm thinking then that pop pressure DOES influence timing of ignition because the compression of the spring in the low-pop-pressure injector would happen quicker than the compression of the spring in an injector with a higher pop pressure. I notice in your videos that your rig idles pretty smooth while many other IDI's seem pretty rough at idle. Is this the reason?

Fram Filters. Yuch!

 

[Full Monte]

Low pressure pop: Say all the other 7 are at 1850 psi and one is at 1200 psi.

The injection time of that cylinder is determined like all the other cylinders. Depending on how low the pop pressure is, the "misting" would not be consistent with the other cylinders in HP output, and all the fuel injected would possible not be completely burned resulting in probably some black smoke. Injection time is in micro seconds. Say at 2000 RPM and 8.5 BTDC the injection time is 23 thousandth of a second. At a low RPM it would act like a miss.

Compression has nothing to do with timing. It would be more like a miss.

That's my thought's on your questions.

I should have been clearer...I meant timing of the ignition rather than the timing of the pressure pulse from the IP.

 

[icanfixall]

Well my engine idles so smoothly because of two reasons. The injectors pop at almost the exact same pressure of 1850 lbs. Then there is the balancing I did to the rotating parts of the engine. No piston weighs more than 1/4 to 1.3 grams differance in any of the others. Thats really not necessary but thats what I wanted. If you recall when I built this engine I did plenty of research. I found my new Mahle turbo pistons were as much as around 12 oxs differance between them. So I contacted the head engineer at Mahle named Eric. He attempted to tell me these pistons can be as much as 14 grams differant in weights and the engine wil run fine..... Note.... He didn't say run smooth... I told him that was not good enough and wanted a much better matched set of 8 pistons. So I paid to ship back my set and waited a long time for a differant set. 6weeks later I got a differant set of 7 pistons... So more contacts were made and a bunch of I'm sorrys came flooding in to me but hell with that. Just send me my damn parts... So I got them finally and did the balance to all 8 of them myself. Then all the rotating parts went to the balance shop. Thats why my engine run smoothly. You actually usually hear it run but you don't feel it run. Kinda spooky too...

 

[Full Monte]

That explains a lot. I was amazed when watching your video how smooth it idled. How did you weight-balance the pistons yourself? Did you shave metal off the heavy ones? Where did you take it off? I'm going to remember this if I ever rebuild. Thanks!