'76 F250 Turbo Build

[Ultra]

For starters, is there much more science behind selecting a throttle body other than not making it excessively large and making sure it's not the smallest diameter restriction on the intake system? In my case, the smallest diameter is the 2" outlet from the turbo and I'll have 2.5" in the intercooler, so it stands to reason I'd be looking around the 60-65 mm range for a throttle body. But I could be off base.

Secondly is more along the lines of intake design theory - My initial idea came from a turbo intake I saw on a 2JZ that wasn't much more than a welded up tube with plates on the ends and runners to the intake flange (first photo below). I started sketching something up that was a similar idea, but instead of having tube runners down, I just have it going straight onto the lower intake. This is based on using a 62mm throttle body, though as I sit here I would probably want 65mm since 62 is smaller than the intercooler piping... but I digress



View attachment 14241

I was trying to think of something that would be easy to fabricate out of simply produced parts, so the manifold flange and TB mount/end cap are just laser cut and welded up to the 4.5" diameter tube.

But back to the more theory question, does TB placement relative to the runners have much of an impact in a turbo build? I.E, is having the air coming in one end of a 28" long manifold going to cause issues with air distribution to the rear cylinders compared to the front? Would there be more benefit to having the throttle body more centrally located on the intake tube?

Keep in mind that post intercooler your charge air becomes more dense. There was an overwhelming trend in the datsun s30 world years back where guys were really eager to put 60mm throttle bodies on their L28's mean while the main intake restriction was the manifold runners. But porting is work and the throttle body was a visible "upgrade" I guess. You should be fine with a 62 or 65mm TB.

Whatever you do for a plenum make sure you have a generous bell mouth radius shape leading into the runners, it helps. Take a look at what plazmaman does for their intakes. Somebody ran some flow models years back (I couldn't find the thread) it showed having the TB angled with a generous short side radius toward the #1 cylinder and the throttle body angled so it kind of points at all the runner ports really helped flow disribution vs the log style intake with the TB mounted 90deg to the runner inlets like your cad model shows.

https://plazmaman.com/product/billet-ba-bf-fg-retro-conversion-manifold/

Also look at the nissan skyline rb20/25 upper intakes. They bolt to the stock lower plenum half just like the stock ford lower you have and are converted to a forward facing TB.

https://plazmaman.com/product/rb25-det-r33-skyline-inlet-plenum/

You can see the distance they put between the TB and first runner. I think some of this is for underhood packaging but it also keeps the air from having to do a hard 90 turn right after getting past the butterfly. How much impact throttle body orientation has on flow in a turbo setup is definitely debatable but the 90deg log definitely was not better than the contoured plenums that guys were testing.

 

[Frank]

Whatever you do for a plenum make sure you have a generous bell mouth radius shape leading into the runners, it helps. Take a look at what plazmaman does for their intakes. Somebody ran some flow models years back (I couldn't find the thread) it showed having the TB angled with a generous short side radius toward the #1 cylinder and the throttle body angled so it kind of points at all the runner ports really helped flow disribution vs the log style intake with the TB mounted 90deg to the runner inlets like your cad model shows.

https://plazmaman.com/product/billet-ba-bf-fg-retro-conversion-manifold/

Ultra, the proportional dimensions of this intake look exactly like the intake on the Detroit Diesel 60 series engine. The first of the new-generation electronic fuel control diesels (circa 1990), this engine was incredibly better than the previous inline 6, 4 cycle designs in use. This engine made just shy of the power of the 3406 Cat, with 118 less cubic inches, and got nearly double the fuel economy. Reduced fuel consumption an average of 11,900 gallons per year, per truck. With or without a throttle, I know first-hand that is an excellent shape for an inline intake.

 

[jgavac]

Thanks for the information Ultra and Frank, this is really helpful!

As far as a specific throttle body, this was what I had in mind when I started in on the manifold design effort. 65mm cable operated, with TPS sensor for the ecu. The only thing I'm not familiar with is what the extra flat bit on top with the gasket is for, but my guess is EGR, so I can make a block off plate for that

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[Frank]

The only thing I'm not familiar with is what the extra flat bit on top with the gasket is for, but my guess is EGR, so I can make a block off plate for that

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Looks like idle air valve location. It will need one.

 

[jgavac]

Looks like idle air valve location. It will need one.

That makes a lot more sense. I'm not super well versed in my EFI stuff yet, but getting there!

I assume I'm going to have outputs on the megasquirt to control that, but I don't have the i/o chart in front of me right this second

 

[Jmustang_65]

What ECU did go with? I would change to a GM TPS senser and IAC. Readily available and work better.

 

[Jmustang_65]

Like this one.

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[Ultra]

Finding something that uses GM sensors would be a bonus. Another option would be a skunk2 throttle body off a honda. Honda stuff is everywhere and cheap for a few franklins you could step up to a billet one. There are a lot of options out there seems like all the GM specific TB's have big butterflies.

Pick your poison,
https://skunk2.com/induction/throttle-bodies/alpha-throttle-body.html

Bit more spendy but accufab has bolt on ford TB and an adapter run gm sensors
https://accufabracing.com/product/mustang-5-0l-1986-1993-65mm-throttle-body/

https://accufabracing.com/product/idle-air-control-adapter-early-late-gm/

 

[jgavac]

What term x did you go with?

I'm using a Megasquirt MS3X for my ecu.

Finding something that uses GM sensors would be a bonus. Another option would be a skunk2 throttle body off a honda. Honda stuff is everywhere and cheap for a few franklins you could step up to a billet one. There are a lot of options out there seems like all the GM specific TB's have big butterflies.

Pick your poison,
https://skunk2.com/induction/throttle-bodies/alpha-throttle-body.html

Bit more spendy but accufab has bolt on ford TB and an adapter run gm sensors
https://accufabracing.com/product/mustang-5-0l-1986-1993-65mm-throttle-body/

https://accufabracing.com/product/idle-air-control-adapter-early-late-gm/

Appreciate the links, I'll check those out. Is the GM sensor design better in some way?

 

[guhfluh]

Not really, just more common and commonly known settings and tuning. Ford stuff works fine though, plenty people use it with success and the PWM IAC is more simple to wire.

Your MS3X will have plenty of options to wire a Ford 2 wire IAC. You can use the IDLE circuit, FIDLE, one of your 2 unused Injector circuits or a Medium Current Driver circuit.

A GM 4 wire stepper will require different wiring, but it can also be easily done with MS3X.

 

[Frank]

If the GM TB posted by Jmustang_65 has the IAC incorporated into it, you're better off there money wise, as the BBK does not appear to have the IAV included.

 

[guhfluh]

If the GM TB posted by Jmustang_65 has the IAC incorporated into it, you're better off there money wise, as the BBK does not appear to have the IAV included.

None of the throttle bodies posted come with the IAC or TPS included. The Summit link picture shows it installed, but the description states it comes without, as do the questions and reviews. The Ford BBK throttle body linked also takes a Ford IAC. The linked Accufab adapter converts a Ford IAC to a GM IAC and can be used on any Ford TB with that style Ford IAC provision.

P.S. A stock 4.9L 6cyl IAC from 87-96 should fit any of the Mustang throttle bodies linked I think.

Many in the MS community even used Jeep/Dodge (4 wire stepper)IACs, though I'm not sure why they were more popular than the GM. And diyautotune.com even sold universal adapters for hose connections.

I say pick your poison. GM is usually cheaper and easier to find, but requires more wiring and eats up more outputs(needs a half bridge push pull?) on the MS3X. Maybe sit down and go through all of the inputs and outputs you need and want to have on the MS3X and make sure they will all work where you want them to and you have enough. I'm pretty sure you will, as many people run a 4 wire IAC, but it's good to check and see where you're at.

 

[jgavac]

I had been trying to get some information on the MS extra forums about sensor inputs, but it's a bit quiet over there so I'll bring up the discussion here.

Here's I have figured at the moment. For sensors in:
-Crank trigger (36-1 wheel)
-Cam sync signal (hall effect off cam fuel pump lobe, or distributor)
-TPS on throttle body
-Wideband O2 sensor
-Coolant temp sensor
-IAT after Intercooler

The MS3X has an onboard MAP that I can use, but what I wasn't sure on was adding another MAP that is open to atmo for altitude correction.

 

[guhfluh]

I had been trying to get some information on the MS extra forums about sensor inputs, but it's a bit quiet over there so I'll bring up the discussion here.

Here's I have figured at the moment. For sensors in:
-Crank trigger (36-1 wheel)
-Cam sync signal (hall effect off cam fuel pump lobe, or distributor)
-TPS on throttle body
-Wideband O2 sensor
-Coolant temp sensor
-IAT after Intercooler

The MS3X has an onboard MAP that I can use, but what I wasn't sure on was adding another MAP that is open to atmo for altitude correction.

Constant baro correction isn't a requirement, as plenty of vehicles never came with such, but it may be useful if you live in an area where you drive through large elevation changes without ever shutting the engine off and restarting. Baro calculations are done with the primary MAP sensor at key on and engine off. Normally when MS user's want a constant baro, they install an internal 4 bar dual sensor, aka "Mapdaddy", or you can wire in an external to one of the analog inputs and I believe you can choose which MAP sensor you want as baro and which one as primary.

 

[jgavac]

The though behind a baro sensor was just for driving in the mtns. I live at sea level, but mountains are close to me. When off roading a couple summers back we were going in cycles from ~1k feet up to 4 or 5k then back down a couple time a day. Or if I ever take it to the rockies

 

[guhfluh]

That makes sense then. You should be able to use any external MAP you want and use the internal as a baro sensor, or vice versa, just set it up in the menus.

 

[jgavac]

While digging around and cleaning up my parts pile of old engine parts over the weekend, I found the distributor that came in the 1980s era junkyard 300 that I slapped in my truck a couple years ago so I could start this engine project. I had originally snagged the gear off it when I was looking into using the v6 cam sync sensor, but didn't pay much attention to it otherwise. As luck would have it, turns out it's the later model TFI distributor with the hall effect sensor. This is good news, because at this stage in the game I decided to stop trying to shove a v6 sync-sensor-shaped plug into an inline 6 distributor shaped hole, and just run a distributor body with a modified cap to get the oil pump drive, and use the fuel pump lobe as my cam sync.

 

[jgavac]

Looking good!
Install the motor mount on the passenger side to see what type of clearance you will have with the exhaust system.

The quality of the motor mount set I got is a little questionable. Passenger side fit fine, but one of the holes on the drivers side is in the wrong place so 1 hole never lines up. I'll need to see about an exchange with rockauto...

Regardless, the mount is a bit in the way but I don't think it's unworkable. Will make getting to the stud on that side interesting...

 

[jgavac]

I'm starting to get a bit restless on this project, if I'm being honest. My plan going into this was to get as much done out of the truck as I could to reduce downtime, but I'm realizing there's some things that are going to be better to do with the new engine installed in the truck - for example, there's a throttle bracket at the back of the engine where it switches from linkage to cable to would probably get in the way of coil #6 if I mount them to the side of the VC. Also, where the intake sits relative to the firewall is different than what I thought, which might influence the upper manifold design. And I think I'm ultimately going to build the harnesses I need in the truck, rather than trying to do them on the bench.

At this point though, I think I'm just delaying cracking into the truck because right now everything works.. There isn't much left to do on the engine for getting it physically installed other than adding some gaskets. I'm notoriously good at kicking a problem down the road when I don't want to deal with it (or am scared of things going sideways), which I think is what is happening here.

I'm tempted now to just start pulling the front clip apart and yank the old motor out, since then I'll be committed and I won't want to keep it out of commission for an extended period of time. Ideally, I'd like to have the new motor running by the end of the summer, since it's been 2 years since I started building it! And truthfully, I'm not sure how much more my $100 junkyard motor in the truck now has to give. It's felt down on power for a while, and I've already gotten *way* more mileage out of it than I planned.

Anyway, just rambling a bit here. My garage situation isn't ideal because the truck doesn't fit inside, so I'll be doing all this work in my driveway, and I'll be dodging the infamous Seattle rain until mid June. And I also have to decide what other work I'm going to do (if any) while the nose is apart - clean and paint frame? Re-dip or replace the inner fenders? Clean up and powder coat the core support? Lots of questions I need to answer for myself.


(pic unrelated, just wanted something in here)

 

[jgavac]

Ever wondered how much power an unknown condition 198something Ford 300 with no tuning makes? No? Well, I was curious lol






This was the best of 4 pulls, and exactly what I was expecting out of this pooch. Hopefully shouldn't be too hard to beat!