Injector pop pressures. Bar to PSI.

[bgilbert]

What are the pop pressures for stock injectors in bar and psi? Intercooled vs. non-intercooled injectors pop pressures the same? Lucas POD's, 185's, 190's pop pressures? If one was to have the pop pressures set, what would be the best pressure to have it set at for best performance/power? How would an engine run/not run with pressures set too low/ or too high?



Is there an equation to convert Bar to PSI?

 

[Mcarcerano]

this is a link with a conversion calculator



http://www.funsupply.com/airguns/psibar.html



1 bar = 14. 5038 psi



hope this helps

 

[JLEONARD]

Bill, Higher pressure would effectivly advance the timing a bit, lower p would retard it.

Then there is the spray pattern difference and that would affect volume and the burn rate.

So having unevenly set pressures would give the engine an unbalance with cylinders burning differently.

Those could all be relatively minor and maybe not noticable by most of us , but you are in the HP range where you need to optimize it and have them all as close as possible.



Jay

 

[dpuckett]

Jay,



Hate to pick on an old geezer here, but a higher pop pressure would hold the injector shut longer, retarding the dynamic timing a hair. But within a given pressure range, the improved atomization of a higher popping would offset any timing retard. Plus, you can always move the pump up a hair to make up for any timing.



Bill- Brian Toscano's injectors are popping in the 3800-4000psi range- right up there with a 24valve, and it kinda sounded like one as he pulled out up my street that night. I believe the general consensus here in this forum is around 250bar or 3626psi. That allows you a good atomization; fuel from a higher flowing injector gets it all in there at once, so to speak, instead of keeping the tip open for more degrees of engine rotation like a lower pressure would. But with your timing, you might even try 260 or 270 bar. Careful, though. You can get TOO high, and start having problems with volume, as the VE pump is only capable of 10K or so psi.



Back to the original question- stock pressure on non-IC is 245bar, or 3550psi. Mine are set at 3650psi, I think. That's what I asked for anyway when I had the stockers redone.



Daniel

 

[BushWakr - RIP]

Well, I have to agree with Daniel... the higher the pop off pressure the more effective "retardation" of timing... . ok it's almost milliseconds but it will be retarded.

Then normal operating bar of our "stock" injectors is 245 bar ( 1 bar= 14. 7psi) so, 245 bar= 3601. 5psi.

Now I understand our pumps will peak out at about 8000psi but I have never confirmed that figure and personally don't believe it's that high.

I have run "performance" injectors with a pop off pressure as high as 270bar= 3969psi.

They made more smoke, they made more power (did not dyno with them) and they generated about 7-8psi more boost without any other tweaking/changes... .

At that level of pop off you could really hear the pump hammering hard to supply the pressure for opening... it sounded just like WAY too much timing... very metallic and "knocky" sound.

On another related issue, it's my understanding that Bosch consider a set of injectors "ok, or with in spec) if they are are within 8bar of each other. I guess that's not too bad really (117. 6psi) but I'd like my injectors alot closer than that, particularly when we are tweaking timing for max performance... .

Just my thoughts here...



pb... .

 

[bgilbert]

I knew Bob would step in here. Thanks. I did the search and it seemed you always gave out the info. Just wanted to cover it again for all the new readers, plus have my guns ready when I pick up my new sticks and ask them where they set the pop pressure.



Sounds to me, having the pump hammering/working hard to supply the pressure for opening, it would shorten the life of your pump and not be that good of an idea??



I'm sure I'm just being paranoid, since diesel injection is Scheid's bread and butter. Just not too many 1st gen dinosaurs come in and want $$$$ injectors built. I asked where he set them, but he wasn't exactly sure off the top his head, but thought they set 1st gens to 3800psi. This was end of business day on Friday before Christmas. So maybe they check the book prior to setting it... .

 

[JLEONARD]

That assumes it takes more time to build the extra pressure than you will gain by the added velocity of the spray generated from that increased pressure. So I'm not necessarily convinced.

Time to dig out the reference books I suppose. Perhaps it depends upon the particular pump?

Good food for thought anyway. Maybe it's even a wash?