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Old 03-08-2008, 08:10 PM
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Stock TPI system on mild 383

I'm wanting to rip off this carb and intake on my 383 and just swap on the Tuned Port Injection EFI system from the 80s-90ish small block chevys.

I was wondering if a motor built to make 400ish HP had a stock L98 MAP or MAF TPI system, stock fuel injectors installed using a MegaSquirt ECU can be tuned to be drivable? Will switching to this system have any ill effect in idle quality, hesitation in part-throttle/WOT. I know it will decrease the overall power and peak power but by using stock injectors will the engine be fine with just less power or will run too lean and ping like crazy?

I will imagine there will be a big decrease in power, dropping this TPI system that was originally designed for the breathing characteristics of a bone stuck 302 or 350cu engine? But my concern is just getting the basics of EFI down and making sure it can pass smog in the process. I already know what this motor feels and sounds like when it is running decent so that may help as well. I haven't gotten into the tuning aspect yet but I saw this as a good possible starting point. I'm not sure what the maximum power output of the stock fuel injectors are capable of but that is something I need to do research on as well. But I would greatly appreciate your opinions, experiences, tips what have you thanks.

This started off as a crate motor and then I've changed out a few things but here are the basics nothing special I can get more info if needed just have to scuffle through a few things hidden in some abyss.

-Hi Tin block 4 bolt main
-3.75" Eagle steel crank
-KB hyper-eutectic pistons 0.060" over
-GM 5.7 "pink" rods ?powder-forged?
-Trick Flow 195 alum. heads 64cc chambers, I was told making about 9.6 to 1 c/r
-I really don't know much about valvetrain but I know the camshaft has 226/228 degrees duration at .050", i'm not sure what the advertised measure is, I believe it is a hydraulic roller setup.
-1.6 rockers
-Clevite tri metal 77 - rod and main bearings
-Dyna gear oil pump and pickup
-EMP Stewart Stage 2 water pmp (will be installing soon).

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Old 03-08-2008, 08:23 PM
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stock TPI setup won't be able to flow enough air for a healthy 383. it was designed for 305s
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Old 03-08-2008, 08:33 PM
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Decide MAF or Speed Density..

The earlier TPI systems used MAF (mass air flow) and the later used MAP (manifold air pressure). High Performance motors tend to do better with the MAF, they require alot of tuning like the MAP. However if you go the Megasquirt route it will have to be tuned reguardless. As for running lean, you can battle those problems with bigger injectors and using a adjustable fuel pressure regulator and turning up the pressure.
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Old 03-08-2008, 09:04 PM
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Quote:
Originally Posted by va4cqd
stock TPI setup won't be able to flow enough air for a healthy 383. it was designed for 305s
right i'm not looking to make the power it should be right now though... I'm looking to just make it run so it can be drivable and pass smog so I can still drive it while tuning the ecu and all that good stuff. I don't want to have to use 3 day passes everytime I want to test it out. I can always try to give it more power once it is running but I just want to know simply if it can be drivable. Or and then give the power it needs one piece at a time as I am learning the basics of tuning the ECU and throwing in bigger fuel injectors, larger runners, better flowing plenum and intake manifold eventually and whatever. But I am just trying to find out some options as my basic entry to attack this project.
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Old 03-08-2008, 09:11 PM
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Quote:
Originally Posted by DV8
The earlier TPI systems used MAF (mass air flow) and the later used MAP (manifold air pressure). High Performance motors tend to do better with the MAF, they require alot of tuning like the MAP. However if you go the Megasquirt route it will have to be tuned reguardless. As for running lean, you can battle those problems with bigger injectors and using a adjustable fuel pressure regulator and turning up the pressure.
Alright cool yeah I need to read up on the MAF MAP thing. Which one is less expensive, which one is more reliable, which one is realistic and how interchangeable are their associated sensors and parts that is pretty much what I am looking for
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Old 03-08-2008, 10:01 PM
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Difference

I myself am putting a TPI in my 54 pickup so I've been doing alot of research. Most Rodders like to use the MAP (speed density) due to the fact that it frees up the intake, you dont have to plan for the MAF sensor pluming in the intake. The MAF if more plentiful to find due the MAP was only used for about 3 years. A excellent source of info is www.thirdgen.org they also have a classified section that is a virtual goldmine for tpi parts. Plus lots of people with a passion for the TPI system.
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Old 03-08-2008, 10:04 PM
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Quote:
Originally Posted by DV8
The earlier TPI systems used MAF (mass air flow) and the later used MAP (manifold air pressure). High Performance motors tend to do better with the MAF, they require alot of tuning like the MAP. However if you go the Megasquirt route it will have to be tuned reguardless. As for running lean, you can battle those problems with bigger injectors and using a adjustable fuel pressure regulator and turning up the pressure.

everything he said....
the MAF is the way to go, it is more tolerant of modifications. just get all the sensors, wire harness, computer etc off the donor car. try and find one off a 350" motor. PCMforless can retune the stock computer for your engine, just give them all your motor specs. i have a vette with the MAF TPI and it is great, smooth idle, great low end torque (that's what the TPI is known for) great mileage (i get 28-29 MPG on the freeway at 70) it's pretty much done just below 5000, but i don't see it as a problem with TPIs on the street--you a going to be running most of the time right in the max torque range and that's what makes it nice. last year i rebuilt my TPI, new injectors, adjustable AFPR, ported the plenum, runners and intake and that helped it in the upper RPM range. if you want to learn about TPI go to corvetteforum/C4 gen and do a search for TPI. you will find a lot of info about operation, repair and mods. there are some real sharp TPI people there.
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Old 03-08-2008, 10:18 PM
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Sweet good stuff, what makes the MAF system more tolerant to other modifications? And how intricate is this plumbing sensor intake thingie?
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Old 03-08-2008, 10:37 PM
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Quote:
Originally Posted by Drewnashty
Sweet good stuff, what makes the MAF system more tolerant to other modifications? And how intricate is this plumbing sensor intake thingie?
the MAF actually reads actual airflow and feeds the info to the computer, the MAP reads manifold pressure (vacuum pressure) and the computer calculates the airflow off of a set of programmed tables. change the airflow characteristics and the MAP could get fooled, of course when the engine goes into closed loop the O2 sensor will try to compensate.
as someone mentioned above, the MAF sensor is in the tube just in front of the throttle body and provisions have to be made to plumb it in. tha MAP is in the plenum so you could just put a filter in front of the throttle body.

GM started with the MAF system for a few years, then switched to the MAP system, then switched to back to the MAF system--what does that tell you!!! i'm not saying the MAP is bad, you probably could't tell which was which by driving the car.
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Old 03-08-2008, 10:44 PM
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Maf

MAF is a plastic piece about 3 inches across that is part of the ducting after the air filter box and before the throttle body. Its a piece of cake to install, alot of people use exhaust pipe to fabricate a nice looking cold air intake and just plumb the MAF into it. It's more tolerant of changes because it basically gets its information from incoming air and exiting exhaust and doesnt really think about what going on inside. While the MAP tries to guess what going on inside, then make changes It's a pretty lame explanation I'm sorry it's late. But I love my TPI IROC TPI may not be the best but it is beautiful!!!!!

EDIT ok i like TECHRON's explanation better
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Old 03-09-2008, 03:09 AM
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Quote:
Originally Posted by DV8
MAF is a plastic piece about 3 inches across that is part of the ducting after the air filter box and before the throttle body. Its a piece of cake to install, alot of people use exhaust pipe to fabricate a nice looking cold air intake and just plumb the MAF into it. It's more tolerant of changes because it basically gets its information from incoming air and exiting exhaust and doesnt really think about what going on inside. While the MAP tries to guess what going on inside, then make changes It's a pretty lame explanation I'm sorry it's late. But I love my TPI IROC TPI may not be the best but it is beautiful!!!!!

EDIT ok i like TECHRON's explanation better
hey deviate (DV8) you sound like you know your stuff too. you can also bypass/disconnect the hot water thingie running through the throttle body--cooler air=more power. you can also descreen the MAF to improve airflow. even though the MAF is a little more trouble to set up due to locating the MAF sensor ahead of the throttle body, you do have the advantage of plumbing a cold air system--cool air=more HP. also pull your throttle body, there are some serious restrictions at the front of the plenum right behind the throttle body. you'll see them.

to the OP, you need to use the stock computer, not an aftermarket. the distributer has no advance curve, the dist. advance curve is controlled by the computer. as stated in a previous post of mine call PCMforless, they will also set up a performance advance curve while they match the computer to your engine.

DV8, my TPI also has the cold start injector, i think it was only used it for 2 years but it makes "start up and go performance awesome"

to the OP, also don't use multec injectors if you buy a TPI with them, they are absolute crap. the bosch injectors are the best, but they are now obsolete. if you buy a TPI with bosch's they can be rebuilt (check riches injectors) or do what i did, go with 22# FMS (that's right, ford motor sport, oh the blasphemy) it is a popular swap with us vette guys, and you get modern injectors for cheap, and they bolt right in. stay away from accel injectors too, they are defective SOBs.
i don't know what else to say except learn all you can on the internet about TPI, they might seem scary when you don't understand them, but they will pretty simple when figure it out, they are simple to me, but most efficient!!
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Old 03-09-2008, 07:05 AM
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You will experience an appreciable drop in performance with the TPI on a 383. The stock TPI as mentioned will not flow enough air to feed a 383. Rumor is it is only good for about 300hp max.

Vince
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Old 03-09-2008, 07:15 AM
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As for a the intake running out of breath this is true. But with enough air flow a EFI systems will make as much power as a carb. Actually most people tend to use the speed density system (MAP sensor) which is more tunable and doesn't have a MAF as a restriction. Regardless you will need larger injectors, adjustable fuel pressure regulator and a custom tune.
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Old 03-09-2008, 07:18 AM
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Quote:
Originally Posted by techron
GM started with the MAF system for a few years, then switched to the MAP system, then switched to back to the MAF system--what does that tell you!!! i'm not saying the MAP is bad, you probably could't tell which was which by driving the car.
Since the LT1 came out GM has used a MAF and a MAP sensor together.
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Old 03-09-2008, 07:48 AM
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Quote:
Originally Posted by RippinRon
As for a the intake running out of breath this is true. But with enough air flow a EFI systems will make as much power as a carb.
Not doubting that, but using GM's 80 to 90ish TPI system on a 383 is pointless from a performance stand point.

Vince
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