I understand that you test injectors to 100 psi as a part of servicing. Are there any Miata or miata-sized injectors that will handle 300 psi? Is it common for injectors to be able to work at that pressure but just aren't tested there because fuel systems don't operate up there so it's pointless to check it?

I am looking at adding liquid propane injection as a second set of injectors in the manifold and I need the injectors to be able to function at 300 psi working pressure. Liquid to gas transition pressure is 174 psi at 70*F, up to 250-ish pressure at high ambient temps so some companies that produce kits pressurize to 300 psi as they know they are safe and it won't go to gas in the lines regardless of ambient temperature.

The second set would be run by the second map in Megasquirt so I will have both gasoline and propane as options at any time by switching maps.

Also, due to the higher pressure, I wouldn't need anything larger than a 250-300cc injector in a turbo application so a set of stock Miata injectors would be perfect. Any chance they will hold and function at 300 psi?

 

Direct injection (diesel & petrol) injectors run at the 1000's of PSI.

 

I understand that, but I didn't know what, if anything, was different. The kits that I have read about say they use "standard automotive injectors" but I wasn't sure if that meant certain types or styles or brands or if any injectors will handle that rate.

 

I was kinda half-assed looking into this recently... All I was really able to find was that rc injectors has some injectors rated for gaseous injection (not what you're talking about, I know...) And they're lo-z and look almost exactly like old school bosch injectors. They're all just solenoids, I would think the biggest issue you'd have at 300psi might be injector o-rings, and/or inconsistent opening/closing times.

That said, stock injectors are cheap, rig you up a test station and see what happens. Worst case you're out a few bucks and it'd be an entertaining thread for the rest of us to read


http://www.rceng.com/Peak-Hold-Injec...tor-P19C5.aspx

 

This gets my vote, obviously. (but if you do it, stand behind a blast shield, as the injectors are likely to blow apart. film would be required, but we don't want you getting hurt )



But in all seriousness, a buddy of mine used to run a 650whp vr4 with propane. I'll drop him a line today and ask how he had it set up.

 

Thanks

The charge cooling benefit from the phase change would be huge on a turbo car. I wouldn't be surprised to see 40* drop in IAT. Not to mention the fuel consumption goes up 10% but I have a 500 gallon tank of the stuff at all times at home and it's $1.69 a gallon so a very large decrease in cost per mile.

 

Yeah, on his car it was a pretty massive difference in power when the BBQ grill tank in the trunk was full versus empty. :-)

 

2 concerns I'd have without consulting the brain trust here at DW.

O-rings/seals being able to maintain that pressure and the injector coils being able to overcome the resistance from those kinds of pressure.

I don't even know if we have a rig here that would be able to test at pressures that high, be it gas or liquid.

 

Now, we do have a new to DW injector that we just released a comple weeks ago that start out life as a Natural Gas injector. They are quite big, flowing 2200cc/min of fuel, but they do have excellent low pulse-width characteristics.