RJ IROC

Greetings Readers!

After a whole year of running MOSTPLUS 42lb/hr injectors, I thought I would share my experience for those looking for a good review.
I'll start by saying, DO NOT BUY THESE INJECTORS. YOU WILL REGRET IT.
Some background: I was a college student on a very tight budget when I was building my 383. I had been tuning (EBL) for a short time on the former powerplant, so I knew the basics. I was a bit overzealous when I decided to get 42lb injectors, but I had no idea what path I would take in the future for the engine. Given the situation, I decided to buy these injectors as opposed to spending the $300+ on a good set of Bosch IIIs. The most popular 42lb/hr injector on Ebay couldn't be THAT bad could it? How did it get that way if it is a terrible product? Long story short, I was able to get my engine running OK, but I ran into tuning loops with fuel. Just couldn't get repeatable AFRs during similar conditions, and the engine behaved poorly at lower loads (jerking, bucking). After graduating school and landing a job, I'm pulling the plug and swapping to Bosch IIIs. Here's why:

1. ZERO injector offsets of any kind are available for these, or any china injector. The specs provided are mostly useless. On an injector that almost certainly needs a tune, this is a warning flag.
2. Unreliable performance at operating temp, as described above.
3. (See first photo below) The construction of the injector is laughable. Look at the gap between the top O-ring and inlet. I have removed the entire set of injectors twice, and more often than not, the top o-rings come off and stay in the fuel rail. Just a sloppy copy job.
4. This is the big one, the pintle caps. 7 of 8 pintle caps fell off as I removed the injectors for the first time. 7 of 8 pintle caps tried to weasel their way past the valve and into the cylinder. 7 of 8 pintle caps were removed with surgical-like precision using a bent coat hanger and some sticky goop. The second and final time I removed the injectors, I was ready for it. I only lost 4 of them this time, but I had blocked the injector bosses with a rag-on-a-rod (Stealth Ram intake mind you). I was able to reach down with tweezers and retrieve them. Bottom line, the pintle caps are poorly made, like everything else on these injectors.

These dumb injectors have caused me so much agony, and that is why I have written this up. Don't buy cheap injectors. I've been there and it isn't worth it. Learn from my ignorance, and please stay away from these Amazon or Ebay injectors. Thank you for reading this!

anesthes

iTrader: (12)

I have several sets of these, in different vehicles and they all work fine.

The biggest problem I found with large injectors + stock ECM's is the injection strategy used. I've also run actual, real, Ford SVO 42# Bosch III injectors on '730 hardware and had the same low speed issues because you just can't command a pulse width low enough reliably. The '730, '165, and so on doesn't support the quasi fuel mode that is supposedly supported on the '749.

On aftermarket ECM's, you can change your fueling strategy to deal with this.

I have a thread on this from a few years ago.

-- Joe

RBob

iTrader: (1)

But the $32B, $6E, and $8D code will go single fire on short PWs. There are PW values that can be changed to control the transition between double fire and single fire.

RBob.

anesthes

iTrader: (12)

True, but it has the issues you noted in the thread the last time we discussed it. Also, only 1 injector driver. It simply never seemed to work properly for me, even on $58/59 code.

I've found that alternating bank to bank works best with big injectors. (Fire bank #1 one revolution, bank #2 second revolution).

-- Joe

RBob

iTrader: (1)

What thread?

$58 code doesn't use single fire. It uses the quasi-async mode.

Alternating bank-to-bank, isn't that the same as single fire?

RBob.

anesthes

iTrader: (12)

This one:

https://www.thirdgen.org/forums/dfi-...-strategy.html

That thread died, probably because not many people here have control over their injection strategies and just don't care. I spent a lot of timing going back and forth and found alternating to work best with large injectors.


Alternating isn't the same at all. You fire one bank per revolution. On single fire you fire both banks every 2 revolutions, so you're injecting a ton of fuel at once. So on alternating, you still have a larger base pulse width because you are only firing 1 bank at a time, but you are not dumping all of your fuel at once per cycle.

How does qusi-async differ from single fire vs double? It has a minimum pulse threshold, and changes the injection events to 1 per cycle instead of two, but doubles the pulse width. That to me seems like switching from double fire to single fire, and just calling it something else.


-- Joe

RJ IROC

RBob

iTrader: (1)

I had very little input to that thread. Mostly to explain the hows & whys of single fire (S/F) versus double fire (D/F).

A ton of fuel in S/F mode? How so, the ECM is in S/F because the injector PW is so small.

Because you don't understand what quasi-async actually is. Learn that and you will see that it is nothing like S/F or D/F.

RBob.

RBob

iTrader: (1)

That is good news, thanks for sharing.

RBob.

anesthes

iTrader: (12)

The PW is too small to be reliable if in double fire mode because the open times. I don't know if you have access to an ASNU and have tested the older rochester injectors, the open times are typically quite long.

You could actually build a diy injector test machine for short money these days, and using a microsquirt or speedduino and some measuring tubes and verify injector data.

A ton of fuel as in it dumps it ALL at once. The engine may require the entire volume of fuel over the operating cycle, but the rate that the fuel is delivered should be controlled.

I know exactly what it is, and it's ultimately the same thing. If the injection pw is below a threshold, it skips an injection event and adds the pulse width to the subsequent event.

If you want to argue the symantics of adding up pulse width time and firing it every other revolution, vs simply doubling injector pw and firing it every other revolution fine, you win! I don't care. I'm aware that the code is functionally different, but achieves the same objective, and ultimately the end result is the same. It either fires once every 4 reference pulses, or once every 8.

My point was simply that, bank to bank works better. My other point was, the cheap MOSPLUS injectors work fine and you can adjust the calibration to make them work just as good as the Bosch injectors. They do have absurdly high dead times, I won't dispute that, but they work perfectly fine if you have the ability to adjust your perimeters.

BTW, my 60# authentic expensive Siemens deka injectors have absurdly high dead times too.

-- Joe

anesthes

iTrader: (12)

Glad to hear it's running well. What are your idle pulse widths in double fire mode ?

-- Joe

RJ IROC

Apologies for the delayed response. I guess I missed the notification. Idle PWs are in the 1.7 to 1.9 ms range. It runs pretty strong, stronger than it ever has before. It feels much more effortless to accelerate now.

anesthes

iTrader: (12)

Interesting...

Years ago, on a 560hp supercharged combo, when I was running Ford 42's my idle pulse widths were more like 1.1-1.2, which is where I had issues. It seems your idle fuel requirements are much higher. I wonder why.

-- Joe

RJ IROC

It could be attributed to injector offsets. I'm not sure if the offsets are added to the pulsewidth that is displayed on the EBL's WUD, or if that PW doesn't reflect the offsets. The 36s i'm using now are much smaller that the 42s, so that could also account for some difference. Fuel pressure differences between the two could result in a difference as well. My WB displays 16-17:1 AFR at idle. I believe this is due to overlap introducing fresh air into the exhaust. Idling at 14:1 resulted in watered eyes from overly rich combustion. Open loop idle BTW.

anesthes

iTrader: (12)

Oh, I missed that you went down a size too. So what were the idle pulse widths with the 42# injectors ?

When I ran 42's back in the day, I just couldn't get them to idle reliably with double fire.

-- Joe

RJ IROC

In single fire mode, the PWs were in the 2.6-2.9 ms range at idle. I also had drivability issues at part throttle and idle unless I used single fire mode. Probably a combination of PW resolution and any mismatch in injector flow.