injectors
- Thread starter ericrapp
- Start date
redrocketz
Member
they aren't normal injectors that you can just swap with a set from RC. These are direct injection injectors a totally different style.
My concerns are realized. Please feel free to pm with more detail if you find time. I see this as a necessity for the near future. and details if you choose. Thanks Roc
AutoXRacer
Member
I've been reading that the stock injectors are not even being pushed to 1/2 their limit...supposedly, we don't need to upgrade our injectors any time soon...
That isn't necessarily true because there is a lot less time for the injector to operate with direct injection. Rule of thumb, is about 1/2 the amount of time as a normal port injector.
Maxx Mazda
Contributor
- :
- Stock P5
Correct, and you can always bump up fuel pressure to increase volume as well. An EMS system would allow you to increase injector open time if you were running insane boost and needed to, but that's basically tuning. I think the stock MZR injectors are more than enough.
also, I know on diesel motors with direct injection (pretty much all of them have this I am pretty sure) changing the injectors out is not as easy. you have to reprime the fuel system... I am pretty sure you'd have to do the same if you swapped injectors on this car too. or I might be way out in left field.
Maxx Mazda
Contributor
- :
- Stock P5
I re-prime my fiel system anytime I have air in it from swapping injectors, fiuel rail whatever.
i know that there has been a set of injectors sent out to a reputable fuel system company to be flow tested. no news has come back yet, but i'm sure the person who sent them out will let us know when the results are in. (yes i know who it is) also i can tell you now, for 99% of us modders the injectors will never be a problem. the injectors are capable of sucking the fuel system dry, the ECU wont let them though. even with my CDFP i can see in my data logs that the pressure will drop slightly when the injectors start commanding more fuel.
to me, that sounds like a fuel pump problem. maybe not "problem" but when the injectors command more fuel, of course the pressure is going to drop, because there is a higher volume flowing out. I'll bet it eventually starts catching back up though.
the stock fuel pump is a big problem. it is MUCH better with the new CDFP though. the pressure will drop slightly during spool-up with a lot of boost. my point was to show that the injectors can even out flow an aftermarket pump if they have too. the injectors react faster than the fuel pump, thats all. the ECU demands fuel so the injectors dish it out. the fuel pump is left playing catch up, which the PG pump does much better than stock. my stock pump let the pressure drop to below 900psi on hard pulls from a roll. the new pump has yet to fall below 1300psi. even with 20+psi in freezing temps ! i will see a quick drop during spool up and then the pressure levels out at 1600-1700 psi all the way to redline.
you just described an inherant flaw in the fuel system. the fuel pump upgrades do a lot to compensate for it, but there is always going to be a drop in the fuel system pressure when the injectors demand more fuel until the fuel pump catches up.
There is no inherent design flaw. Consider the following:
1) The ECU is controlling the "on time" of the injectors. Obviously the fuel pressure must be factored into the equation since the amount of fuel injected is a function of the fuel pressure and the on time.
2) The ECU always knows what the fuel pressure is.
Maxx Mazda
Contributor
- :
- Stock P5
Does the MS3 have a returnless fuel system?
mrlilguy157
Member
- :
- 07 mazdaspeed 3
there is a return line from the rail back to the cam driven fuel pump, but nothing back to the tank.
the injectors are close to 800-1200cc. I mailed out a set to be flow tested at 125bar (1800psi or so), so I'll have numbers for that hopefully by the end of the week. Its been a struggle for these guys to get to me, but I was rather aggressive and imperative last Friday afternoon on the phone with them.
In my opinion - you'll never really need new injectors for this car, for typical power goals. The upgraded pump keeps pressures up which keeps maximum volume of flow up, through the injectors, as 'maxx mazda' said.
If you're looking to upgrade the fuel system, the fuel pump is the place to start.
the injectors are close to 800-1200cc. I mailed out a set to be flow tested at 125bar (1800psi or so), so I'll have numbers for that hopefully by the end of the week. Its been a struggle for these guys to get to me, but I was rather aggressive and imperative last Friday afternoon on the phone with them.
In my opinion - you'll never really need new injectors for this car, for typical power goals. The upgraded pump keeps pressures up which keeps maximum volume of flow up, through the injectors, as 'maxx mazda' said.
If you're looking to upgrade the fuel system, the fuel pump is the place to start.
That is a very large injector for a stock car isn't it? What do you consider typical power goals? Thanks
If the ecu always knows in realtime psi why would it be allowing the drop on the stock supply? As mentioned by Tru-Is. Is it poor math on the ecu, an improper signal or a mechanical limitation? thank you
You guys really went to work today! I still have more questions. Especially with hard #s. I have read some odd statements elsewhere that has created some confusion for me and others I suppose, the direct injection factor. I will have to talk more to my diesel friends. I am still looking at theory here and the info sure helps. Send that flow test result to us Mr. Please, Who makes the oem and does anybody know model#. I am open to all methods or combinations thereof to be sure i have access to all the fuel I might ever need. Anyone using pressure regulators? peace and happy motoring!
i dont think there is any "poor math" i think it is just the nature of the beast. the pump in question here is cam driven. what that means is it can only do so much, based on your engine RPM. the higher you rev, the more fuel it can supply. thats why the pressure loss is seen in the low/mid range during boost spool-up. the ECU knows how much fuel pressure is available in the rail and will determine how long to hold each injector open based on that pressure. the stock pump runs out of steam HARD on increased boost levels, and even stock boost if the temps get low enough. my car on high boost in the cold had horrible pressure drops in the mid range during spool up. the PG/MRLILGUY cdfp helps out a lot with this issue. this pump allows more fuel pressure to be made across the full RPM range. sure there is still a drop in pressure, but it is stays at least 400 psi higher during those same conditions. it is much faster to " catch up " after the dip in pressure too. i had my MBC set very aggressive the other day at the track and forgot to turn it down for the drive home. i was holding 26PSI in 5th gear !! i data logged a pull from 3k RPM up to 6500 with boost holding 26psi dropping to about 20 at 6500. there was a small dip down to 1390psi fuel pressurebetween 3200-4000RPM after that the prussure stayed above 1600psi. the AFR's were also in the low 11's-high 10's !!! the pump works, there is no question in my mind. i think anybody with lots of mods and/or raised boost would be a fool not to have one.
mrlilguy157
Member
- :
- 07 mazdaspeed 3
400whp should be no problem with these injectors at 125bar. I PM'd you some links to stuff that will help you understand a bit more; you're still looking at this car as if it was regular ole port injection, not the case!
