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4.9 Less Power at WOT than Part EFI Question

Moderator: Mod Squad

94f150rules
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Joined: Wed Nov 29, 2017 5:17 pm

4.9 Less Power at WOT than Part EFI Question

Post #1 by 94f150rules » Tue Apr 09, 2019 2:16 pm

Hey guys I have a 94 F150, I recently rebuilt the engine it has a crane cam stronger springs, and I milled 30 off the block and 20 off the head so im guessing my compression is 9 1/2 to 1, other than that it's bone stock. Back when I was building the engine all the guys in the Forum that knew what's going on said I may run out of fuel on the EFI system. I wanted to rebuild the engine the way I wanted it, and then try to solve my fuel issues at a later date if possible. I have to admit the truck has so much more power from part throttle to almost half throttle than it ever had, my only complaint is that at wide open throttle it barely does anything if I step out of it a little bit the truck starts pulling again. I was thinking of buying the moates quarterhorse and installing it, does anyone have experience with it? I'm hoping to use it to see real-time data and look at my fuel trim then try to raise my fuel pressure and stop the truck from leaning out. I'm not sure if I'll be good enough to try and retune the computer myself so I thought maybe that's the easy way out. I started pricing a carb, manifold, and distributor and it's well over $1,000 so maybe I can sink that much into my fuel injection system and have a really good running truck. What do you guys think?

pmuller9
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Location: Columbus, Indiana

Re: 4.9 Less Power at WOT than Part EFI Question

Post #2 by pmuller9 » Tue Apr 09, 2019 4:22 pm

Once you go past a certain throttle position and absolute manifold pressure the system goes into open loop mode and no longer looks at the O2 sensor for compensation.
Instead it just reads off the original fuel map which will be too lean for the cam.
The fuel pressure is already near 60 PSI.
If you do reprogram the fuel table you should get larger injectors rather than over running the stock injectors and having them fail.

At this point a lot of people look at replacing the stock ECM with an MegaSquirt 2 that plugs into the same connector and will let you go to a wide band O2 sensor for closed loop operation up to WOT.

94f150rules
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Re: 4.9 Less Power at WOT than Part EFI Question

Post #3 by 94f150rules » Tue Apr 09, 2019 6:22 pm

pmuller9 wrote:Once you go past a certain throttle position and absolute manifold pressure the system goes into open loop mode and no longer looks at the O2 sensor for compensation.
Instead it just reads off the original fuel map which will be too lean for the cam.
The fuel pressure is already near 60 PSI.
If you do reprogram the fuel table you should get larger injectors rather than over running the stock injectors and having them fail.

At this point a lot of people look at replacing the stock ECM with an MegaSquirt 2 that plugs into the same connector and will let you go to a wide band O2 sensor for closed loop operation up to WOT.



If you remember you were one of the guys that told me this was going to happen, and I'm glad that you're trying to help me out I appreciate that. I thought a lot about the megasquirt, but I can't find anybody who's actually completed the swap, and I'm afraid to get in really deep and have nothing. Its not a cheap swap anymore. It's difficult to be in Uncharted Territory. That's why I was considering the quarter horse board because it seems to have a following. But it's still something I really know nothing about. Once I get my combination right though I want to start looking into buying one of your cylinder heads.

Harte3
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Re: 4.9 Less Power at WOT than Part EFI Question

Post #4 by Harte3 » Tue Apr 09, 2019 7:43 pm

viewforum.php?f=51

Try that Forum for your MegaSquirt and other EFI fueling systems.
'83 F150 300, 0.030 over, Offy DP, Holley 4160/1848-1 465 cfm, Comp Cam 260H. P/P head, EFI exhaust manifolds, Walker Y Pipe, Super Cat, Turbo muffler, Recurved DSII, Mallory HyFire 6a, ACCEL Super Stock Coil, Taylor 8mm Wires, EFI plugs.

pmuller9
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Location: Columbus, Indiana

Re: 4.9 Less Power at WOT than Part EFI Question

Post #5 by pmuller9 » Tue Apr 09, 2019 8:47 pm

No matter which direction you go with EFI you will need larger injectors.
The injector should be sized so the duty cycle isn't greater than 80% at peak power.

If you go with larger injectors before you change anything else it may be possible to get the open throttle response OK because you deliver more fuel for the same map once the computer goes open loop.
However guessing at the problem doesn't work.

My next step would be to get a Air/Fuel ratio meter and look at what it really happening.
It comes with an wide band O2 that can be used if you go to a MegaSquirt system.

If you go with one of our heads later the stock computer will definitely need to be replaced.
To take full advantage of the Jr or SR head the cam should have a minimum .050" duration of 220 degrees.

Phase3
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Location: Pittsburgh pa

Re: 4.9 Less Power at WOT than Part EFI Question

Post #6 by Phase3 » Wed Apr 10, 2019 9:07 am

I have used the microsquirt system by megasquirt on 2 mustangs. One 4 cyl turbo bought microsquirt from stinger performance. Another microsquirt and connector harness from efisolutions. Both are very user friendly and not too bad to set up. The auto tune takes most of the fueling guess work out of it. Will need a good wideband. I like innovate because the o2 sensors are the same as 2011 ford oem. Will need to register with tuner studio and thats 60 dollars on top of it.
With moates quarter horse, ive read there is a battery in those j port chips and if the battery depletes and goes bad it will lose your tune. This is not verified by myself just relaying info. Also im not sure yoh can tune on the fly which is really nice to have.

www.diyautotune.com
Type in search bar microsquirt to piece together a kit reasonably
1996 f150 turbo 4.9 OBD2 M5OD 4x4 12 lbs on 93
1997 f350 351w cclb

88F15088
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Re: 4.9 Less Power at WOT than Part EFI Question

Post #7 by 88F15088 » Wed Apr 10, 2019 12:56 pm

I Megasquirted my truck and it has been my daily for a few months and a few thousand miles with no major issues.

Here's where I bought my kit:
http://www.poweraddersolutions.com/mega ... connector/

It does NOT come with the harness connector, you will need to either buy one or go to a junkyard and find an ECU to salvage one off of.

The kit took me about a day to assemble. There are several resistors, capacitors, and transistors that need to be soldered to the board. You can find a complete write-up online, and everything comes bagged with numbers, so it's actually not too difficult (you want to have good soldering skills!)

You also need a good wideband O2 sensor, I went with the AEM and wired it directly into the Megasquirt.

The software to program the Megasquirt is free, but for $60-70 you can buy the premium version that comes with AutoTune, which I think is totally worth it. You plug in your target AFR values and it tunes the fuel input to reach the target AFR. When I swapped to larger injectors, I simply changed the injector flow on the software, and was back and running in 5 minutes, no kidding!

You can do so much more than just fuel. You can setup ignition tables, control relays, have knock control, boost control, etc.

I don't claim to be an expert, and it took some trial and error, but I can probably give you some more advice if you are looking to go this route. I hope to put together a full write-up someday to make it easier for people in the future.

Expect to spend anywhere from $700-1,000 between buying the Megasquirt, connector, wideband, software, and any other pieces.

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