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 Post subject: MFI or Tbi with Turbo
PostPosted: Sun Jan 26, 2020 1:30 pm 
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Car Model*: 1965 PLYMOUTH FURY
Hello all,

I am new to the group and have a 65 Fury with the 225. I am trying g to balance price and effectiveness. I am trying to decide if I want to use a mfi manifold from Gill welding or use a tbi system again either way it will end up with a small turbo. I am not looking to make a hot rod /6 here I'm just trying. To make it reliable and trying to make it go when the gas pedal is pushed. Later on down the road I will worry about tryin to kill V8's with it.


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PostPosted: Sun Jan 26, 2020 6:06 pm 
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If you have later on down the road in mind i would say get the mpfi. The gill piece is nice from what I have seen. I would like to get one sometime.


Greg

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PostPosted: Sun Jan 26, 2020 6:20 pm 
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That's kinda what I was thinkin. Everyone that I have seen that used the Gill manifold really likes it and has some major fuel millage bump. Although I dont know if the milage will go up all that much with a turbo on there.


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PostPosted: Mon Jan 27, 2020 2:29 am 
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It can if you keep foot off floor.


Greg

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PostPosted: Mon Jan 27, 2020 4:21 am 
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I would spring for MPFI. You can also have an aluminum 4bbl intake modified for injectors. Gill can do that for about $450. Maybe with low boost (4-8 psi), you would be OK with a manually tuneable TBI system, but I would avoid it for higher boost.

My turbo Dart gets the same MPG as before the turbo, yes, as long as I keep my foot out of it. Turbo is rather large, so it doesn't spool up unless you mean it. That helps with the MPG, I am pretty sure. I have a port-EFI-modified Offy 4V on that, and will likely go to a larger port manifold like a Clifford later.

Lou

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PostPosted: Mon Jan 27, 2020 4:55 am 
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Dart270 wrote:
I would spring for MPFI. You can also have an aluminum 4bbl intake modified for injectors. Gill can do that for about $450. Maybe with low boost (4-8 psi), you would be OK with a manually tuneable TBI system, but I would avoid it for higher boost.

My turbo Dart gets the same MPG as before the turbo, yes, as long as I keep my foot out of it. Turbo is rather large, so it doesn't spool up unless you mean it. That helps with the MPG, I am pretty sure. I have a port-EFI-modified Offy 4V on that, and will likely go to a larger port manifold like a Clifford later.

Lou



That makes sense and was kinda what I was thinking. The only real advantage I could see with doing TBI is the cost but if ya have to do it twice it's not really cost effective in the end


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PostPosted: Mon Jan 27, 2020 6:27 am 
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Bingo.

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PostPosted: Mon Jan 27, 2020 10:02 am 
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moparih wrote:
Dart270 wrote:
if ya have to do it twice it's not really cost effective in the end



Yep! I was thing that bu didn't type it!


Greg

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PostPosted: Mon Jan 27, 2020 2:07 pm 
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The test results I've seen with TBI on several naturally aspirated engines almost always had lousy fuel distribution, like what you'd see if you took an intake manifold designed for a Holley carburetor and bodged a Quadrajet onto it. I wouldn't trust a TBI to keep all the cylinders fed correctly under boost.

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PostPosted: Mon Jan 27, 2020 2:17 pm 
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In my view, the whole point of fuel injection is more accurate fuel delivery, and that includes fuel distribution. TBI essentially replaces the carb with a computer controlled pair of injectors contantly spraying fuel. The TBI system does nothing to correct the inherent fuel distribution problems of a "wet" or carbureted intake manifold.

Slant sixes have long been recognized for have a better intake manifold from a fuel distribution perspective than comparable six cylinder intakes from the 60s, but it has also been recognized for decades that the slant six intake has inherent fuel distribution problems.

If you are going through the trouble of a fuel injection conversion, I say go straight to multi-point injection. Even batch fired injection with wasted spark is an improvement over a carb or TBI.

I also hope, someday, to built a turbo MPFI slant for my daily driver truck. I intend to build it with an eye towards fuel efficiency rather than performance.


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PostPosted: Mon Jan 27, 2020 5:25 pm 
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Reed wrote:
In my view, the whole point of fuel injection is more accurate fuel delivery, and that includes fuel distribution..
That is a fundamental problem. If the end cylinders are lean you can never get maximum performance or fuel economy, and exhaust valves may burn. I've been hanging out on BMW forums, as engineered as their inline sixes are they can run warmer on #6 because of the long path the coolant makes ( only an issue when the cooling system is in bad shape ). I'm sure variances in heat and fuel distribution can be an issue on the slant six. TBI is a stopgap cost savings technology that works on my Geo Metro, but there's only three cylinders - 9.8:1 CR and works fine on 87 octane. TBI probably won't work well on an inline six.


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PostPosted: Tue Jan 28, 2020 3:27 am 
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I ran TBI on my 64 Dart for 16 yrs. No dramatic fuel distribution issues, on a cammed up 250 HP NA motor with a Clifford 4bbl intake. I could notice differences in plug readings, but they were quite minor. Speaking from actual personal experience on a 225, I would run TBI at low boost and I would be conservative with the tuneup. You would still have a huge advantage over a carb as you can tune mixture under boost in seconds or minutes with a laptop instead of swapping jets, air bleeds, sealing ports, etc...

All that said, I will be converting that car to MP-EFI when I put it back together. MP-EFI is better, of course, but more expensive and complex.

Lou

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PostPosted: Tue Jan 28, 2020 9:03 am 
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Dart270 wrote:
MP-EFI is better, of course, but more expensive and complex.


And that, really, is my point. If one is going through the trouble to convert to fuel injection,one might as well go directly to MPFI and skip over TBI. From what I have found, the Microsquirt system looks to be about the simplest and cheapest system to get MPFI. Batch fired, wasted spark, but true MPFI. I don't know if it is compatible with forced induction. Other more expensive systems have true sequential injection and can be used with boost.


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PostPosted: Tue Jan 28, 2020 9:09 am 
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Reed wrote:
From what I have found, the Microsquirt system looks to be about the simplest and cheapest system to get MPFI. Batch fired, wasted spark, but true MPFI. I don't know if it is compatible with forced induction.


It is - just pick a MAP sensor that reads up to your intended boost level.

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PostPosted: Tue Jan 28, 2020 10:17 am 
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MadScientistMatt wrote:
Reed wrote:
From what I have found, the Microsquirt system looks to be about the simplest and cheapest system to get MPFI. Batch fired, wasted spark, but true MPFI. I don't know if it is compatible with forced induction.


It is - just pick a MAP sensor that reads up to your intended boost level.


Cool. Once I start the project in earnest I will get more into the Microsquirt options.


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