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Ford Six Forced induction FAQ

Moderator: Mod Squad

Linc's 200

Ford Six Forced induction FAQ

Post #1 by Linc's 200 » Sun Feb 05, 2006 10:33 pm

Hello Folks, welcome to the Ford Six "Forced induction FAQ"

In this thread, we'll try to expose some basic engine combos and mods that others running forced induction on their Ford six have experience with. All first hand experience is welcome here so that others can follow from example, but if you have any specific questions, please use the PM feature or start another thread.

We will try to keep this thread CLEAN and CONCISE so that there isn't the need to wade through 20 pages of info, of which only three or four pages are actually technically helpful.
Again, if you have questions that will spawn an entirely new realm of discussion, Please post in a new thread so we can keep this one simple.

Where to begin?
Knowledge is power....and the more you can learn, the more power you will make!

There are two main turbo books available: "Turbochargers" by Hugh MacInnes (a little outdated but still excellent reading) and the book by Corky Bell (which I haven't yet read).
Another book has gotten good reviews by a reader, "drag-200stang":
drag-200stang wrote:The best book on I've found on turbocharging is "Forced Induction Performance Tuning" by A. Graham Bell, published 2002 by Haynes Publishing.
I have Hugh's and Corky Bell's books which are very good but this one at 464 pages covers everything and is easy to read. Turbo header construction, engine building, EFI, intercoolers, cam shaft specs on cars that have actually been raced are explained in detail. It covers all forced induction systems.

Of course, the good members of message boards, like the fine one you are reading now, are always standing by to help, if they can.

I will begin with my combo:
High-mileage (123,000) 1982 Ford 200 (3.3 liter), engine is stock from valve cover to oil pan. The bulky pre-cat style exhaust manifold has been removed for the much simpler, 1970 version.
From the ex manifold is a "U" shaped pipe to a Garrett TO4B turbo with an "O" trim turbine, .68 A/R turbine housing, and the compressor side is a "S-3" trim. I bought the turbo new, in the box off of ebay for $260 (with a 1.00 A/R housing), and had to buy the .68 A/R housing from Majestic Turbo for $130

(You can see the whole build in the thread titled "Another turbo 200 nears completion": )

Which Turbo?

(O.K. I need to clear up something. I get a lot of emails asking: "Hey some guy on eBay has a turbo with a .60 A/R, will it work on my engine?" A/R DOES NOT TELL YOU ANYTHING ABOUT WHAT SIZE THE TURBO IS!!! You have to look at trim numbers, or at the very least the diameter of the compressor inducer, to get an idea of what size it is. And that is just a starting point!)

The biggest hurdle for most beginners is trying to decide what turbo to buy. There are SO MANY out there to choose from, and one size DOES NOT fit all!!

In fact, turbos are kind of fussy about what size engine they are installed on. Every turbo compressor "trim" has a turbo "map" that will show how efficient the turbo is under various pressure (in BAR, or "number of atmospheres") and flow (amount of air measured in "pounds per minute" or "kilograms per second"). The closer you can get to the center of the efficiency "islands" on the map, the better the turbo will work for your engine.

The following chart is from an article by Hot Rod:

The entire article can be found here: ... 312_turbo/

The above chart is a good starting point, but is NOT an "End All" for selecting a turbo. There are many designs available, most of which are more efficient than the relatively obsolete TO4B trims listed above, but cost and availability all play factors when selecting a turbo.

Reading a compressor map can be a daunting experience for the uninitiated, but there are three basic criteria you will be looking at:

1) The amount on air (in pounds per minute) the engine will be moving
(read along the bottom line of the map)
2) the pressure (boost) you will run
(read along the vertical left side)
3) where on the "efficiency islands" these two points meet

To determine the amount of air the engine is flowing, you have to do a lot of density and temperature calculations. Older maps used "CFM" (cubic feet per minute, like a carb) but as the air is colder or warmer, or at different barometric pressures (running at sea level versus running in the mountains) CFM will change too much to be used as an accurate tool for measuring air.

However, the "mass" of air (whether measured in pounds or kilograms) is a lot easier to measure because it is independent of temperature or barometric pressure.

Thankfully, this is the computer age, and there are many different places you can go to find how many "pounds of air" your engine will be moving.

For example, one such calculator exists at the Ray Hall turbochargers site:

Lets look at an example compressor map (courtesy ... r_maps.htm

This is the "S-3" trim I built my car around:

I used the Ray Hall calculator with these input data:
Bore: 3.68
stroke: 3.13
cyls: 6
RPM: 5000
Temp: 24* C
V.E. 70%
Press 15 psi
comp eff 72%
intc eff 75%
(You can fine tune the data later, just plug some conservative numbers in for now....and remember, NOTHING is 100% efficient :wink: )

The answer came up with about 26 pounds per minute.
Hold that thought.... :D

Now, 1.00 Bar is equivalent to atmospheric pressure of 14.7 psi at sea level on a standard day, so naturally, 2.0 Bar is 14.7 "psig", or psi on your boost gauge. I chose 15 psi for the calculator because that is pretty darn close to 14.7 (2.0 Bar) so you don't get so confused, so quickly.

Now, Lets look at the map again. Find 26 pounds on the bottom line and go up - - - find 2.0 Bar on the left and go to the right. Where the two lines meet is about here:

Now, we are TRYING to find a turbo that would put us smack-dab in the very center of the highest efficiency island....but for now, it looks like we'll have to settle for 72%. That's actually not too shabby!!
Getting farther out into the outer rings means the turbo has to work harder to move the same amount of air....and harder work means hotter air temps. (Another reason why turbo size matching is important)

A LOT of factors determine the efficiency numbers on that calculator (for instance, the stock log head doesn't flow particularly all) so volumetric efficiency will suffer. Just use it as a guideline.

That's up to you to decide. "New" is easier to find, since you just order the size you want. "Used".... well, you are at the mercy of what you find in the junkyard, classified ads or eBay. Even if you DO find the RIGHT size (of all used ones you run across, most will be too big or too small) it may not be in good shape. Unless you have it in your hands, you won't know if it has been damaged or worn out.

I hear a lot of "I found this turbo from a Romanian-made diesel tractor, will it work on my car?" Chances are excellent there is no published map for it....the closest you can get will be to measure the diameter of the compressor wheel and try to compare that measurement with the diameter of a known turbo. At best, it is still a crapshoot. Stay away from "weird" sources.

Which carbs will work?

Answer: any one that can be made to!

After examination, I decided to use the stock 1982 Mustang carburetor that came on the engine, known as a Holley model 1946. I decided this carb would work for blow through for several reasons:

1) It has a solid black "Nitrophyl" float already installed. These do not collapse under pressure like a hollow brass one will. Many carbuertors can have a ready-made Nitrophyl float ordered, or some need to have one custom made.
2) It has an annular booster venturi. Not critical, but annular venturis tend to go rich under high airflow/airspeeds. This is a tendency that is helpful for turbo engines, since an air fuel ratio for a forced induction engine needs to be richer at full power (around 11:1) than naturally aspirated engines (around 12-12.5:1) at full power.
3) Its a Holley uses Holley jets!! Holley jets are readily available to accomplish tuning. Another alternative is drilling a stock jet, or soldering a stock brass jet closed and re-drilling as necessary to obtain correct flow rates.
4) The steel "bridge" that holds the air cleaner stud is a very solid design. Any weakness in this area will allow the "bonnet" or "hat" to blow off of the top of the carb when under pressure.
5) Numerous screws hold the top to the body. Very necessary for the same reasons - - - boost pressure tries to blow the carb apart. It needs to be sturdy.

Any carburetor can handle boost, but whether it can handle 2 psi or 20 psi will depend on its design features and stengths/weaknesses.

FUEL SYSTEMS - You need lots of fuel flow. Period. How do you get it?

My first set-up used a stock mechanical fuel pump that is "boost referenced". There is a vent hole above the fuel pump diaphram that needs to be drilled to 1/4" and have a short piece of 1/4" steel brake line epoxied in to make a mechanical fuel pump work. Mechanical pumps differ a little bit by manufacturers - - some only have a small square vent hole...these won't work. You need one with the round tubular vent. Pics will come later...

I found that a mechanical pump was pretty reliable up to around 10 psi of boost before the little plastic disks inside used as check valves started to get hurt.

Later, I went full electrical as far as fuel pumps go. The current set up has a 5 gallon fuel cell, then a Holley "Red" fuel pump draws fuel from the tank, sends it to an E2182 fuel pump (from a 1986 F-150 "frame mount" or thereabouts) and then to an Aeromotive fuel pressure regulator.

DO NOT cheap out on your fuel system unless you enjoy having problems. I will venture a guess that 40%-50% of the time I spent setting up my turbo package was getting all the bugs worked out of the fuel system. It is VERY embarassing to be tearing down the dragstrip, just to have your engine fall flat on its face 150 feet shy of the 1/8th mile mark! (ask me how I know....)
Also, it looks really bad when you are trying to show your friends how fast your "New Turbo" makes you car!!

INTERCOOLERS - Do I need one or not? What size?

An intercooler is a device that is mounted in between the turbo compressor outlet and the carburetor/throttle body. The old rule of thumb used to be anything over 10 psi needed an intercooler, but that isn't true for everybody. I honestly believe that the cooler you can get the air going into the engine, the better the car will perform. I elected to run an intercooler on my car, since turbo outlet temps can exceed 300* F when runnin' at full boogey. I figure the carb will be exposed to enough heat on its own being so near to the turbo, that I need to do everything I can to keep the carb a little bit cooler.

Most common intercoolers are "air to air". There are front mount intercoolers (exposed to the air in the front of the car), side mount intercoolers (usually in the front fenderwell area...not all cars have room in front) and even some "water to air" intercooler setups (much more expensive, and require a separate water tank and pump)

ALSO, the cooler the fuel/air charge.....The less tendency for the engine to detonate! So cooler inlet temps mean you can get away with lower octane fuel. More on that later....

Let's talk a little bit about WASTEGATES.

If you have ever seen a water wheel on an old flour mill or lumber mill, you will see that water flow will dictate how much work the wheel can do, and at what speed. There is a small gate that allows more or less water to reach the wheel.

The turbine on the exhaust side of the turbo is pretty similar, except instead of "shutting off" flow to the turbo, we'll allow the exhasut to go around it (or bypass) the turbine. Less flow to the turbine will let it slow down so it stops doing so much work and making so much boost.

The wastegate has a rubber diaphram that senses pressure, and a spring to hold it closed. You can adjust you boost pressure by either using a softer (less boost)or stiffer spring (more boost)..... or you can use a device called a "boost controller" that limits the amount of pressure that the diaphram will sense (more on that device later)

As boost rises in the intake, a rubber line leading to the underside of the rubber diaphram in the wastegate senses pressure, and pushes pressure against the spring. Once that pressure is high enough, the spring collapses a little bit, allowing the valve to open, and let some exhaust past.

The wastegate is similar to the float in a carb, in that it seeks "equilibrium" and stays in one, stable setting (doesn't open and close rapidly, it stays in one place - AS NEEDED)

Key note: The harder the engine works, the more exhaust it makes. As the revs climb, more exhaust volume is created as well. The wastegate will slowly continue to open, as needed, in order to keep boost at the level you have selected - - - even though the engine makes more power and the revs climb higher.

We need to integrate this knowledge with the turbo map again. It is the KEY. As revs climb, so does airflow in "pounds per minute". See the arched lines on the map? (82,000, 96,000, etc) Those are "turbine shaft speeds". Notice that if you want more pressure or more airflow, you need a higher shaft speed. The way the wastgeate controls boost is by allowing the shaft speed to climb, or allowing shaft speed to slow down - - - all by adjusting how much exhaust is allowed to flow through the turbine, and how much is allowed to "Bypass" around it.

I will add more over time as I have the chance. PLEASE give me feedback (by PM) if you have suggestions for additional information or nreed more info added ... I don't ever claim to know it all, and I would like for the information to be from a strong collective.
Last edited by Linc's 200 on Thu Nov 29, 2007 3:45 am, edited 2 times in total.


Post #2 by kitabel » Wed Oct 25, 2006 6:43 pm

I have a few comments on superchargers for smaller engines here - directed at bikes, but the basics are similar:

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Post #3 by XPC66 » Wed Jul 25, 2007 5:36 am

O.K. I need to clear up something. I get a lot of emails asking: "Hey some guy on eBay has a turbo with a .60 A/R, will it work on my engine?" A/R DOES NOT TELL YOU ANYTHING ABOUT WHAT SIZE THE TURBO IS!!! You have to look at trim numbers, or at the very least the diameter of the compressor inducer, to get an idea of what size it is. And that is just a starting point!)

I tend to disagree with that statement. The A/R will give an indication of the turbocharger size, for offshelf units. For instance if I said I had an A/R 1.2 you'd know it isn't for a 1.6 litre engine and conversely if I said it was 0.35 you would know it won't be in the 5.0 litre donk application.

I guess what you were trying to say is that the combination of trim, wheel size and A/R all affect performance and can't be considered in isolation for accurate selection?


turbo sizing

Post #4 by joe » Sat Jul 28, 2007 12:56 am

Unless you have found the pefect combo its hard to say what size you need,there are so many diffrent things to consider so ask around i have found that a single turbo off of a diesel twice the size of your motor and half the rpm is a good place to start for an oddball combo that you cant get any info or help on,further more if it does wind up being close you can almost always change parts to fit your project.If it spools too late you can put a similer but smaller exaust housing,or the opposit to make it spool later or not falloff the power as soon.Same with the compresser,the t3 turbo came on lots of diffrent things cars trucks boats etc... with very diffrent needs ,look around and see what other people are using this goes for almost all turbos i have ever seen.

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Post #5 by TCIC 300ci superbeast » Thu Nov 22, 2007 7:05 pm

hay guys im building a turbo300. i got all the parts to rebuild it and chromoly rings, stock 91 9.1:1cr piston. t would like to know how much boost i can push with out doing to much damage to the piston?
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Post #6 by sabre694 » Tue Mar 04, 2008 1:20 am

thank you for some excellent info
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How much boost willa 4.9 with cast crank take

Post #7 by brnwaxa » Mon Jan 05, 2009 4:13 pm

I am building a turbo 300, forged pistons, shot piened rods. I am guessing the cast crank will be the weak link. I am hoping for someone with experience either first hand or a link to someone who has been there. So all other things aside I an looking fro the safe boost for street use and the cast crank.

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Post #8 by big blue » Sat Jan 31, 2009 12:14 pm

TCIC 300ci superbeast wrote:hay guys im building a turbo300. i got all the parts to rebuild it and chromoly rings, stock 91 9.1:1cr piston. t would like to know how much boost i can push with out doing to much damage to the piston?
You can run as much boost as you want as long as you don't experience abnormal combustion, but the general rule is to keep it around 5-6 pounds and it will live (cast piston), hypereutectic pistons can handle more, but they can shatter. It all comes back to how the tune is and how risky you are. As long as you don't tune the motor to the edge and run a high enough octane fuel, you'll be ok.

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Re: Ford Six Forced induction FAQ

Post #9 by ryan11 » Fri Jan 29, 2010 8:25 pm

also turbos sometimes need a oil psi restrictor, for the oil in line, some you need to by it and some come with them in the stock fitting on the oil inlet.

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Re: Ford Six Forced induction FAQ

Post #10 by MEvans043 » Tue Jan 21, 2014 11:07 am

Question, why is there no discussion on turbo size other than T3 or T4? I mean, on the Mustang forums I'm a member of they discuss turbo size in mm. You have 60mm twin setups to 76mm single setups and so on. T3 and T4 doesn't mean jack to me. How big is the GM turbo that a lot of guys are running?
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