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I recently swapped from 300 (4.9L) I6 with M5OD to 351W (5.8L) V8 in my ’91 F150 2WD, single cab, short bed.
The 351 was out of a ’95 Bronco. I used GT40 heads, JBA Shorty Stainless Steel Headers, 1.7 Ratio Crane Roller Rockers on Stock Roller Cam, 5.8L lower intake ported to match 5.0L upper intake. It’s pretty much a copy of Scndsin’s build except for the cam. (Scndsin’s build details here https://www.ford-trucks.com/forums/1...5-8-build.html).
To swap a ‘95 351 into my ’91 300 equipped truck I needed engine perches, motor mounts, A/C Line, both power steering Lines, ECU, ’91 V8 engine wiring (to match truck wiring), distributor with wiring to match ’91 wiring (distributor mounted ignition module), but with steel gear to match the roller cam (Spectra Premium part number FD19), 351 flywheel, clutch, pressure plate, radiator, and wiring to use the 95 amp 3G alternator on the ’95 351 in my ’91.
I originally planned to run it using a rebuilt Ford ECU, but eventually decided to take the $200 I was going to spend on a rebuilt Ford ECU and put it toward the $800 for a PiMPx ECU from www.stinger-performance.com . Unfortunately, this means I won’t be able to tell how big of a difference it made since I never ran it with a Ford ECU.
In hindsight, if I had known from the beginning about the PiMPx ECU I probably would have gone with long tube headers (since I wouldn’t be worried about retaining EGR) and I might have gone with a different cam (since I wouldn’t have to choose one that would play nice with the Ford Speed Density ECU).
Stinger Performance offers the following ECU options for our trucks:
PiMPx – Batch fire, no transmission control
PiMPxs – Batch or Sequential fire (based on jumper setup), no transmission control
PiMPxShift – Batch or Sequential fire (based on jumper setup), E4OD control
This writeup is for the PiMPx ECU since my truck is batch fire and I have a manual transmission.
PiMPx Contents (Note: I bought the Spartan 2 Wideband O2 controller with my PiMPx, but other options are available).
The first thing you have to do is install the jumpers required for your setup. These are described in detail in the PiMPx Startup Guide. I installed Jumpers 1, 2, 14, and 19 (jumpered to 12v side). I also installed Jumper 3 since I wanted to use the ECU to run my Electric fan.
The next thing I did was wire the Spartan 2 Wideband controller to interface with the ECU.
In order to avoid cutting my wiring harness I cut the pigtail off of my old O2 sensor and wired the Spartan 2 to the old O2 sensor pigtail, which could then be plugged into my truck’s wiring harness.
I used my digital meter in DC voltage mode to find the Keyed 12v first, then switch to Ohms to check for continuity to the other ECU pins.
Spartan Red wire – Power - Keyed 12v
Spartan Green wire – Wideband Signal to ECU – ECU Pin 29
(Note that the Spartan 2 has a wire for narrow band output as well, so you could use it to run an AFR gauge with your stock ECU if you wanted to.)
On to making the new ECU physically fit in the truck.
I had to drill a hole in my firewall for the vacuum hose for the built in MAP sensor nipple.
I wanted to put a grommet in this hole to protect the hose and keep water from running in. Unfortunately the hole was so close to the ECU opening that I wasn’t able to find a grommet to fit. I ended up cutting the bottom off of a large rubber washer to make it flat to fit the top of the ECU opening. Then I stuck it in place with black RTV
I had to cut a notch in the lower bracket of the ECU support to allow room for the USB plug to plug into the ECU.
I discovered that there are only a few bolts holding this plate in. If you remove it you can take it to the workbench to cut this notch much easier than trying to do it in the truck.
The 90 degree USB cable is from www.L-com.com part number CAA-90LB-2M . The 2M = 2 meter length. 3M, 4M, and 5M (3 meter, 4 meter, and 5 meter) are also available if you want a longer cable.
The expansion port of the ECU is partially obstructed. This didn’t matter to me as I wasn’t planning on using the expansion port.)
After that I installed Tuner Studio (provided on the USB drive).
(I think you can download Tuner Studio for free, but you will want to pay for the licensed version in order to us the “Auto Tune” feature). This is a purchase option when buying PiMPx from www.stinger-performance.com .
I turned my key on, heard the fuel pump prime, and had Tuner Studio communicating with my laptop in no time.
I was now ready to load the based tune provided by Stinger performance on the USB drive, and after setting a few basic settings I was ready to start up my engine for the first time. It started right up, but my O2 sensor was reading super lean (19.9) and never moved. I learned that this was because the only exhaust I had was a down-pipe, which had the O2 sensor near the end of the pipe. Apparently, this causes fresh air to get sucked back into the pipe between pulses causing a false lean reading. I stuck some temporary exhaust on just to get me to the exhaust shop. With the temp exhaust in place, I started getting some readings besides just 19.9, but they were still erratic due to a leak where the temp exhaust was attached. I believe real exhaust welded in place will solve this issue. It ran well enough that I was able to drive it to drop it off with my exhaust guy. He said he should get to it today or tomorrow. I babied it because I don’t want to really push it until I know that I can trust the AFR reading and get some “Auto Tune” time in to make adjustments for various driving conditions. I will report back after further driving and tuning.
To get an idea of what the setup in Tuner Studio looks like and to see the settings that need to be set prior to startup check out these videos from Stinger Performance.
Not all of these videos applied to me since I’m not using transmission control and I didn’t have to move any wires, but I included them here for those of you that may have interest in those things. I do plan to add a wire to pin 55 to control my electric fan eventually, so I guess the video on moving wires applies somewhat.
Also, I found these videos to be very helpful even though some of his screens in Tuner Studio look slightly different.
They give you an idea of how to get started tuning. They are essentially the same video, except one is a screen recording instead of just trying to record the laptop screen with a camera. The screen recording is easier to see the details of Tuner Studio, but I like the other one as well, because you get to see him actually setup a base tune from scratch, start the car, and the adjust his idle by adjusting fuel and timing.
Fantastic write-up, Mikulh! I'm going to order a couple of those 90° USB cables, the straight ones that used to be provided are less than ideal for the position. Next time I'm in the shop, I'll take a picture of the expansion plug to add to this thread for reference.
Update after tuning and driving for a couple of days:
Exhaust cured my erratic AFR reading, and after doing a small amount of tuning and some driving while running Auto Tune the past couple of days I'm very pleased with the PiMPx ECU.
At first I had a little bit of off-idle stumble, but I noted where the dot moved to on the VE table (fuel table) when that happened, added a little fuel there and the problem was solved.
At this point the only issue I have is with cold starts when it's below about 40 degrees outside. I'm pretty sure I have a bad IAC (one of the few items I didn't replace on this engine when building it). I can see that ECU is commanding the IAC valve to open up to 70%, but the engine never never idles up... so the problem doesn't appear to be the fault of the ECU. The IAC appears to be the same from the 300 to the 351. I'll have to double check part numbers to be sure, but if it is the same then I'll just grab the IAC from my old 300 sitting in the corner of my shop, swap it on and see what happens.
(EDIT: I just checked and it appears that the 300 and 351 use different IAC valves...guess I'll have to buy one.)
Even with this very small problem, I can hold the throttle down slightly for about 5-10 seconds and then get off of it and it will idle. It hasn't caused any driveability issues, and I really believe a new IAC will correct this problem.
Prior to this I had absolutely zero tuning experience, so I'm pretty pleased with how easy it has been so far.
However, in the interest of full disclosure, I should probably mention that I work in IT, so I work with PCs daily... I've just never used one to tune an engine before.
Thanks for the picture of the packaging, I ordered a couple of those cables last night.
Glad to hear you've got it running and driving.
Tuning the cold start is probably the most frustrating thing to do, because you really only get 1 shot to do it before you need to wait for the engine to cool back down again.
I ran into an IAC issue when I swapped motors in my '89 as well. I had the PimpX on the previous motor, but had it tuned well enough that the IAC was hardly doing anything, so when I tried to tune the new motor, I couldn't do anything to keep it running. Used the laptop to trace down the issue, much like you. Really shined a light on the diagnostic ability of the Megasquirt ECU and Tuning Studio.
Thanks for the picture of the packaging, I ordered a couple of those cables last night.
Glad to hear you've got it running and driving.
Tuning the cold start is probably the most frustrating thing to do, because you really only get 1 shot to do it before you need to wait for the engine to cool back down again.
I ran into an IAC issue when I swapped motors in my '89 as well. I had the PimpX on the previous motor, but had it tuned well enough that the IAC was hardly doing anything, so when I tried to tune the new motor, I couldn't do anything to keep it running. Used the laptop to trace down the issue, much like you. Really shined a light on the diagnostic ability of the Megasquirt ECU and Tuning Studio.
Honestly, it's so minor that it took me a couple of days to even realize the IAC isn't working. It's not even a problem if its above about 40 degrees. I could probably turn in the Idle screw to give it a little more air, then re-calibrate TPS, and tune around it... But I think I'll go ahead and replace it just so the ECU has a little more idle control.
When you mentioned before that you had been driving your truck for a while with an IAC you didn't realize was bad I didn't understand, but I get it now.
I'm using the AFR reading in the Tuner Studio Software. If I decide to add an AFR Gauge in the future I can add any AFR gauge that uses 0v-5v by hooking it up to the Spartan2 signal wire.
PiMPx offers the AEM X-Series Wideband O2 Controller as one of the options when purchasing PiMPx, and TunerStudio lets you put in custom values for Wideband Controller to allow you to use most Wideband Controllers... So if you ever decided to go PiMPx you should be able to use your existing AEM Wideband.
Out of curiosity, where/how did you mount your gauge?
According to the diagram on page 4 of this document it has a 0v-5v output, which is the same as the Spartan2 I'm using.
I don't think you're going to have a problem.
01-11-2021, 11:20 AM
