I've been mulling over the EFI article and was wondering, on an EFI turbo set up would you put this MAF sensor on the turbo inlet or outlet? If you put it on the outlet, are the GM ones air tight under pressure? Will a Ford one for a 5.0 liter work (same values)? Larger diameter would equal better flow and the Mustang boys swap them for bigger ones regularly so they're of little value to them.
motorhedfred

motorhedfred@yahoo.com

You would want to put the MAF before the turbo. I don't think that the MAF is calibrated over a wide enough temperature range to work on the turbo output side. Don't forget that the MAF measures the amount of air that the engine is consuming by determining the rate that the incoming air cools an internal heated component.

There are two types of GM MAF sensors. The output of the Delco MAF used with the 3.8L is a frequency, while the other, Bosch, has a voltage output. I don't know what type Ford uses, but even if it is the same as the Delco I'm quite sure that it wouldn't be compatible with a GM ECM. If the stock 3.8L MAF isn't large enough for use with a turbo, then I would think that the one used with the 3.8L turbo would be the way to go. I've got to find out if these sensors are different. Does anyone know?

I've done some planning for a turbo installation but have a long way to go. I bought some used 3.8L turbo 28 lb/hr injectors and I even scored a 3.8L turbo ECM from a 1985 Buick Regal for $10 at a local swap meet. The ECM is for a sequential set-up (I'm quite sure that all 3.8L EFI turbo engines are sequential) but I reasoned that without a signal from a cam sensor the system would probably go into a "limp home mode" and work like a batch fire system. So, since the wiring is essentially the same, I plugged it in place of my ECM and tried it. The car started and ran very well until I put it into heavy acceleration. Then there was a distinct miss. (Just don't call me "miss fire Bob")! Initially I thought "well that's that" and put my original ECM back in. Later I got thinking about it though, and it occurred to me that perhaps since the ECM is calibrated for the larger turbo injectors, that that had caused the engine to run lean at WOT. I haven't been able to investigate further but will eventually.

The biggest problem I'm going to have installing a turbo is figuring out how to fit it in. The car has power steering and I've installed an aftermarket AC. I also installed power brakes when I converted to disc brakes. I could certainly live without the power steering and power brakes, but replacing them will just add to the task. I'll probably relocate the battery as well. No way am I going to get rid of the AC! That was too difficult to engineer and install and I love it; even in a convertible! Ya, I know, I'm spoiled rotten and I can hear you all groaning!

Bob D



BBobbias@aol.com

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Sorry, Bob....I gotta argue this one. If you put the MAF on the intake side of the turbo, you'll be measuring the amount of air the TURBO is ingesting. What you want to do is measure the amount of (compressed) air the ENGINE is ingesting. I would think the MAF should be between the turbo and the throttle body.
:
: I bought some used 3.8L turbo 28 lb/hr
: injectors and I even scored a 3.8L turbo ECM
: from a 1985 Buick Regal for $10 at a local
: swap meet.
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GOOD score, Bob !!
:
: The ECM is for a sequential set-up (I'm quite
: sure that all 3.8L EFI turbo engines are
: sequential) but I reasoned that without a
: signal from a cam sensor the system would
: probably go into a "limp home mode" and work
: like a batch fire system.
*************************************************
Hmmmmm. Bob, if the ECU uses a cam signal, is it multiple signals, or just one signal, that tells the ECU where #1 is at? I'm thinking along the lines that you (may) have the makings of sequential EFI in your hands.
If it uses a cam position signal, why couldn't it use a signal from the distributor for the same thing? That may work whether it's a single signal or multiple signals. It might only require an ECU and harness change.
:
: The biggest problem I'm going to have
: installing a turbo is figuring out how to
: fit it in. The car has power steering and
: I've installed an aftermarket AC. I also
: installed power brakes when I converted to
: disc brakes. I could certainly live without
: the power steering and power brakes, but
: replacing them will just add to the task.
: I'll probably relocate the battery as well.
: No way am I going to get rid of the AC! That
: was too difficult to engineer and install
: and I love it; even in a convertible! Ya, I
: know, I'm spoiled rotten and I can hear you
: all groaning!
**************************************************
Sheesh, Bob!! No wonder you want the "booster"! With all the "garbage" hangin' off your engine, you gotta be losing a third of the horsepower, plus the additional weight. As for the spoiled comment, no biggie. That's what I got my '95 V-8 Dak for. Bells and whistles and horsepower, oh my!

Roger

GTS225@aol.com

Roger,
One other thing to keep in mind is that when the turbo compresses the air, it gets hot, real hot.
(that's why intercoolers are such a nice addition to a turbo system)
My guess would be to start by installing the MAF sensor in the same place as it was in the doner system and try to duplicate the incomming air path, (cool outside air vs BBQed underhood air) then adjust the new system from there.
DD

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DRAT!! The simplest of physics, and I get tripped up.....not thinking far enough into it!
:
: My guess would be to start by installing the
: MAF sensor in the same place as it was in
: the doner system and try to duplicate the
: incomming air path, (cool outside air vs
: BBQed underhood air) then adjust the new
: system from there.
*************************************************
Ok, I'll concede. This makes me think about it a little more, and conclude it wouldn't work worth a hoot. A MAF sensor works on the principal of airflow cooling off a heated wire, the ECU then monitors the amount of energy, (current), required to maintain a constant temp on the wire. Heated airflow would make the MAF/ECU think the car was pulling less air than it actually was, and the ECU wouldn't feed the needed fuel for the conditions. YOU GO, BOB!! I may not fully understand EFI, but I'm pretty decent with basic physics.

Roger


GTS225@aol.com

Roger,
Remember also that the MAF sensor is measuring the weight of the air, and that the engine can't ingest any more pounds of air than what goes through the MAF sensor, whether it's compressed air or not. This reminds me of the question "what weighs more, a pound of feathers or a pound of lead". You can't get more pounds of air out of the turbo than you put in. The air just takes up less space on the output side, but the weight is the same. I'm not trying to beat you to death with this but I'm just trying to fully explain it.

With respect to your cam position sensor question, I think it is just one signal that the ECM receives, but I'm not sure. With the one signal, (say when the #1 intake is opening), and the engine's RPM, the computer should be able to fire all of the injectors sequentially at the right time. A distributor is in fact a cam position sensor. It's just that you have to incorporate all of the necessary electronics to properly signal the ECM. In fact, they seem to have done something just like this in the most recent issue of Mopar Action magazine. It's part of the article "DFI Dynamite" which I haven't fully digested yet.

Bob D



BBobbias@aol.com