INJECTORS

[KimoYogi]

Has anyone successfully installed and used 75lb/hr Delphi injectors on the Aussie MultiPort manifold setup? If so how are they working out?  Their price is right, $65 each, if the injectors performance is good and they mate up with the fuel rail and manifold.  Replies welcomed!!

[89tsi20g]

sup, i got them and will install them next weekend, should be no problems, i got mine

from Precision Turbo, rob NJ.

[Joel]

I'm using them with a Haltech/Magna without issue.

 

I have another set that I'm selling (friend bought them for his miata but they dont fit). Never been used, $235 + shipping, or $250 shipped (your choice). Let me know if you interested.

 

Joel

[89onaquest]

with the computer controlled cars now, injector size it mute. At least going big.

 

Once the computer gets involved, it will adjust the pulse length to suit the needs of the engine.

 

typically, once you go larger, you will naturally, eliminate a few small flat spots in the fuel curze.

 

But, say for example, a car has 17 lbers stock. You replace with 19 lbers. You will gain some power, cause that little of a boost(along with going higher) do nothing but eliminate some low fuel pressure issues. It will not "over richen" the mix, cause the computer will see it, and cut the pulse time of the injectors.

Now, besides getting rid of some flat sopts, you will have extra fuel availible for future mods.

[mikec]

There is a "too big" injector size though.  At idle and low RPMs the fuel demand is fairly small.  To meet this small demand using a large fuel injector requires very short pulses.  Depending on the type of injector (pintle vs. deflected disk) it's possible it won't respond fast enough to the short pulse - sometimes it'll open and other times it won't open far enough.  Ergo, unsteady fuel flow at low RPMs/idle.

 

Also, a lot depends on the programming in the ECU.  How much "range" can it's "learn" mode handle?  If you over-size injectors, the ECU has to "learn" to command a shorter pulse.  Some can adjust their computations quite a bit and will adapt.  Others though limit how large the adjustment can be so they may not be able to reach the correct point.  

 

mike c.

[89onaquest]

There is a "too big" injector size though.  At idle and low RPMs the fuel demand is fairly small.  To meet this small demand using a large fuel injector requires very short pulses.  Depending on the type of injector (pintle vs. deflected disk) it's possible it won't respond fast enough to the short pulse - sometimes it'll open and other times it won't open far enough.  Ergo, unsteady fuel flow at low RPMs/idle.

 

Also, a lot depends on the programming in the ECU.  How much "range" can it's "learn" mode handle?  If you over-size injectors, the ECU has to "learn" to command a shorter pulse.  Some can adjust their computations quite a bit and will adapt.  Others though limit how large the adjustment can be so they may not be able to reach the correct point.  

 

mike c.

Good points.

 

I will say that the ECU on my cars have more then handled a 10Lb increase over stock with no consequences, other then it has a better recorded fuel curve now. At least that is going by data logging. The dead spots are completely gone, and there is a few spots where power definatley increased.

 

As far as the injectors being too big at idle, I typically use GM pintle style, very fast reaction time Typically 20-30 NS is the slowest. Now at a pressure of 45 PSI that equates to roughly 1-2.5 CC of extra fuel at the most.

 

Now for somps learning... totally depends on car, and computer. However, MAF systems can learn much better then MAP systems. They adjust F/R by shear air mass recorded. MAF is also much more efficent at this. MAP have variables that it goes by. While, yes MAF has similar tables, it can go beyond its maps, and keep the same curve IF IT'S A DECENT COMP.

I will always say that programing your own chips is always better. Cause, well... It is. You can hook the laptop, record data, go back home and review it. You cnan then make adjustments as neccesary.

[Joel]

An interesting thing to note is when making changes on the Haltech (and I've heard others claim the same with the same or other brands of ecu/injectors) is the base idle time.

 

For instance, you can make percentage adjustments... say across the board to the fuel maps in the haltech. When you increase injector size by 25%, you "lean" the map out roughly 25% to get you in a similar ballpark (you of coarse have to retune still, as that method isn't perfect). However... You should not do that for the idle settings, as there usually is little change. Injectors don't like to low of open times, or they start to fail. 1.2-1.6MS seems to be the general "rule" as the lowest PW MS settings you can run.

 

Anything about 1000cc's and up on this motor is going to idle real nasty. My 787cc (75lb'rs) are cutting it close, but I've not had to much issue running low PW times, and getting the mixture right for low timing settings like you have at idle.

 

Joel

[89onaquest]

I like the % capible comuters, but sometimes there is nothing like going right down to staright timing.

 

The times I was posting was about the issue that was brought up about low idle richness, and how larger injectors flow more fuel, need a decent close/reation time as to not simply "dump" fuel into the intake.

 

I just posted my personal dealing with a certain type of injector, the GM Pintle style. Which I have yet to run into big injectors(55Lb+) reacting slowly.