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Astrodokk 09-11-2011 12:19 PM

Mopar MPFI kit engine compartment pics
I have a Mopar Multi Port Fuel Injection system installed in my 1985 CJ7. It was installed in 2000, and I bought it this way a few months ago.
I would like to see any of your engine compartments (front view is best) so that I can compare and perhaps change mine to look better. The funky air cleaner that's in there now looks pretty bad to my eyes.
Let's see what you all have done with yours!
Here's mine.

andresesquire 09-11-2011 07:50 PM

I have some pics from my build Post 148

This is with the MPFI kit setup.

Astrodokk 09-11-2011 09:27 PM

That's very clean. I see that your filter is on the driver side. Does it matter what side it goes on? Mine, as you can see, is on the passenger side but I think because there's more room there. The PO took out most of the after market AC stuff. I may just put one back in.

fredrok 09-12-2011 12:19 AM

1 Attachment(s)

Astrodokk 09-12-2011 07:27 AM

OK, there's one on the passenger side. Nice bracket holding the filter. What company makes that?
I see the hydraulic hood lifts are pretty slim there. Do they hold up the hood pretty well? I was considering doing that too.
Is that a 4.0L valve cover?

fredrok 09-12-2011 08:06 AM

They do a fine job holding the hood up.

Yes, 4.0 VC, but it's also a 4.0 head.

Astrodokk 09-12-2011 08:38 AM

I see. Thanks for the link.
The PO kept the 4.2L head on mine and only did the FI upgrade. I read that it's better with the 4.0 head, but mine runs very well as is. The only problem I have is buying 92 octane gas for it. I'm running 87 right now, but it pings on the freeway. My retired mechanic buddy questions why it needs 92 octane. What is the reason?

fredrok 09-12-2011 08:43 AM

You may find that with the stock head and MPFI, it will ping even with 92. That's the primary reason I went to the 4.0 head and a side benefit is a little more HP.

Astrodokk 09-12-2011 08:48 AM

If you don't mind, what's the rationale for using the smaller head? How does it reduce ping, or better yet, why have to use 92 octane with this FI kit?
Since I didn't do the upgrade, and the PO never expalined anything to me, I'm learning as I go.

fredrok 09-12-2011 09:00 AM

The head is a much better flow design and more efficient at getting air into and out of the combustion chamber. Don't be confused by the numerical engine volume (4.0, 4.2). Particularly, the head with casting # 7120 is the most deireable.

Trying to simplify, higher octane fuel has a higher flashpoint. It takes a bit more compression to light it off in the engine and thus is less prone to pre-ignition (ping). The MPFI system is so much more efficient at getting more atomized air/fuel mixture into the cylinder and thus raises overall combustion pressures and with that an increased risk of ping in poorly engineered head designs (read 4.2). Much head flow technology is focused on volumetric efficiency and combustion "swirl" which is the ability to cram as much air/fuel mixture into the combustion chamber and do so in a way that does not create "hot spots" which result in pinging (lighting off of fuel well before the piston is in a position to receive the ignition). The 4.0 head does all of that better (more efficiently).

Try 92 octane, but if that does not help, you will need to go to a 4.0 head or find someone with a DRB II diagnostic computer and associated cable and decrease the timing. But that would be a band-aid and decrease overall power.

fredrok 09-12-2011 09:04 AM

I would also suggest searching eBay for a set of Bosch 0280155703 fuel injectors. They are a direct replacement and a MUCH better design than the original injectors. Whether it helps your ping issue or not, they are a nice improvement on an already great system. They have a 4-hole (EV6) newer pintle design where the stock injectors are a 1 hole pintle design. It sounds counter-intuitive to what I was explaining above, I know, but the even better atomization could eliminate your pinging before changing the head. Doesn't hurt to try because I'd recommend them either way even if you have no pinging issues.

Please follow up on all of your findings.

PERK 09-12-2011 09:37 AM

this is an OBD 1 system you can not adjust the timing, it's pre set in the computer. If you follow that link I sent you (installation) to Hesco, theres days of reading on their MPI board as to how the system works and other peoples problems and fixes. Hesco is great to deal with.

PERK 09-12-2011 09:46 AM

this may help explain the head design

fredrok 09-12-2011 10:05 AM


Originally Posted by PERK (Post 12159296)
this is an OBD 1 system you can not adjust the timing, it's pre set in the computer. If you follow that link I sent you (installation) to Hesco, theres days of reading on their MPI board as to how the system works and other peoples problems and fixes. Hesco is great to deal with.

Sorry, that's incorrect. At the same Hesco site, you'll find plenty of info on DRB II computers and the ability to retard timing with it.

Astrodokk 09-12-2011 10:16 AM

That was a good read. I'm not even sure now if the head is 4.2 or 4.o, since the valve cover got changed to an aluminum with no engine size on it. I'll call the PO to ask about that.

The time now is 12:23 PM.

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