TBI to TPI conversion (MPFI)

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pro17

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Attached are cold startups of the old TBI vs first startup of TPI. Notice how quicker TPI starts up vs TBI (I hear a piston hit top of the stroke 15 times with the TBI, and possible 2 in TPI). I assume this is because fuel is injected much closer to the cylinder than way above the intake like a carb or TBI.
Weather conditions are not exact. For example, with the TBI, it was about 75 or 80, and TPI was at least 100. But even at 50k miles, in the middle of summer on a cold start, the TBI will still take a couple of seconds to start.
 

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pro17

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I decided to rewire and get new conduit for the majority of the work, and while at it go ahead and see if I could figure out a solution for the heater core.
The f-bodys (and i think early model trucks) had the heater core outlet hose go into the radiator. My 95 doesnt have that - it has the port on top of the water pump (to get the cab hotter quicker so that the driver doesnt have to wait for the thermostat to open up?). But the problem is that the TPI intake has the core outlet right there next to the water pump inlet.
I couldnt find molded hoses to that would make it over to the passenger side like I wanted. But I found online 90 and 45 degree nipples that should work on amazon/ebay. With some modified cushon clamps and the existing plastic piece that holds down the overflow hose I think these hoses should stay put.

Also - since I cant edit my first post, i wanted to clarify that all of the equipment i purchased came from a 91 transam, not an 89.

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pro17

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The home depot oil 1/4 to 1/8 back to 1/4 conversion tubing piping (whatever) junk that i did started to leak as expected, so I threw that out. So I moved the sensor to above the oil filter like the camaros/firebirds have them. Put a 1/8 NPT steel plug in its place on the china wall.

So if you look above your oil filter you will find plug.JPG. It's a 14mm head with 1/4 NPT threads. From there, you can put in an oil sensor.
Below are 2 pictures - camaro.jpg and truck.jpg. The camaro's sensor has a longer neck. The longer neck is required If you plug the sensor straight out. The longer neck though, makes the harness hit my truck's headers. So, I had to purchase some sort of elbow (similar to what is on the back of the motor). So from Veneersupplies.com I bought a long brass street elbow 1/4 NPT (its the only place I could find a 1/4 - 1/4 elbow of the correct length that would not hit the header).
The wiring needs to be extended from the back of the engine to the oil filter 2 or 3 feet.

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pro17

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Ever since day one, its been a little slow to start. I discovered it was being flooded a lot. It was due to a parameter in the ECM (something like Cranking BPW). Its how often to keep the injectors open when cranking. Since 1 TBI injector has to feed 4 cylinders, the BPW is high. Now that MPFI puts an injector in each cylinder, there's no reason to keep every injector open that long. So I cut the BPW value by 4 and it starts up perfectly now.
 

pro17

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What was the ball park cost and time it took to complete this?
I'm sure someone could knock it out over the weekend if they had all of the parts. But for me it was a learning process so it took weeks, ordering parts and tuning.
You'll need a chip burner and chip, the intake, throttle body (LT1 or TPI doesnt matter), higher pressure fuel pump (from 96-98 vortec truck if you want), throttle/cruise cables, accessory brackets, and modify your fuel lines at a minimum. But I also got a drivers side battery holder so I could move the battery over and use a 99+ air filter box. Also powercoated some stuff. Youll find some random pictures of the stuff here:
https://www.flickr.com/photos/137252704@N03/albums/with/72157668068712113
In all it cost me about 1400. But there are some things I did that you dont have to or could do yourself. Like tig welding the bungs on new fuel lines and the powdercoating. I had to get new injectors - a couple of them weren't spraying correctly. Also relocating the oil sensor.
 

JesusM

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Hi there, I just replying to this thread I know this is 2020 and I know i can go with different route on this swap. But after collecting parts for a tpi swap for so many years and still collecting parts I'm going to do the same in my 94 sierra. I can always go with a ls swap but my budget wont let me. But I like the looks of a tpi. My question to you is did you used the tbi ecm or you used a tpi ecm. If you used the tbi ecm can you explain to me, if you can and you have time, how did you do it step by step. Your help would greatly appreciated . Thank you very very much looking forward to read from you!!
 
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