ITB project failure leading to 75mm throttlebody install on a C3.2

[Tippy]

I spent many months compiling parts to do a Suzuki Hayabusa (52mm) ITB project. It was a very exciting project, but the more I learned, the more I found it was difficult to actually execute as nearly everything is custom made, and the fun ran out. Beings (at the time) I didn't have access to a machine shop to make a lot of things, I knew I needed a backup plan.

That backup plan came in the form of a 75mm throttlebody from a 96-04 Mustang V8.

Why did I need bigger induction? I am turbocharged, and knew the 63mm TB was a huge bottleneck. Also, Chris Carroll from Turbo Kraft had posted 2 dyno runs comparing the 3.2 intake to ITB's with no other changes to the engine, turbo, etc., and the ITB's made additional power virtually everywhere throughout the range with a huge mid-range bump in torque. Like 50ft/lbs!

But, the ITB project was fully stalled, and I knew the Mustang TB would have to prevail.

Looking at various TB's, the Mustang TB looked really close to the C3.2's. The more I looked at the pictures online, the more I felt this wouldn't be too bad to put on the 3.2 intake.

So, on eBay, I found many for only $65 (obviously not made in the USA!). I figured I had nothing to lose......

Got it in, and it was fairly well made. No issues. And get this, the TPS adapter piece works with the same BMW TPS that I was using! It's has the same "D" shaft size as the 3.2 TB (also the 930 and IIRC, the 3.0?)!

I did have to figure the angle of the BMW TPS to the Mustang TPS drive adapter, and then mill a new 1/16" slot.

So, there were a few things that didn't work right away. The shaft was very low in the TB housing, where the 3.2 was quite higher. Right off I knew the throttle geometry would not work. Next, the bolt spacing was narrower on the Mustang vs 3.2. No big deal, just elongate the holes. The biggest challenge was the throttle bracket. Figured I would have to make a complete new piece, but later on I explain how I used the original Mustang one.

I spent many nights trying to figure the geometry of the 3.2 linkage. After finally calculating out the proper angles and lever arm distance from center to center, plus understanding where the 3.2 linkage would attach to the Mustang piece, I knew I was good to go.

The calculations I determined were 36* and ~1.206" distance center to center for the 3.2 linkage. The awesome thing is this, and it was twofold is below.

1. The tab on the Mustang lever that stopped the lever at WOT, when bent flat from the 90* angle, at this crease, was right at the angle and dimensions quoted above!

2. Once I put the 3.2 linkage from the bell crank on where the Mustang WOT tab was located, the linkage socket became the stop! Awesome!

One thing I have to add is, I had to remove extra tabs not used on the Mustang TB so they'd clear the intake. Simple Dremel cuts took care of these as it's just thick sheetmetal.

Ok, I knew I was in the clear, and I just needed to get the rest done to execute.

The throttle shaft on the Mustang TB sits about 0.715" lower than the 3.2. I figured I could use a 3/4" aluminum plate to take up the spacing difference, bore a 75mm hole, and put through holes for the bolt holes. After deliberation, I determined I would make the bolthole pattern the same as the 3.2 (2.75" center to center) through the adapter, and simply elongate the Mustang bolt holes.

I had access to a CNC, so I had this piece made after making it in SolidWorks. Took 10 minutes on the machine, and I was in business.

Prior, I determined since I was putting a 0.750" adapter spacer under the TB, I'd need to lop off the same amount on the bore of the TB to keep the height the same as the 3.2. I did this on my fathers mill at his resto shop, then chucked it in his lathe too, and redid the recessed area where the silicone hose seals against reforming the lip. Came out nice.

Last part was porting the 3.2 intake. I found that the casting would not allow a full 75mm bore in the areas at the most fore and aft. I simply made a chamfer leading to the thin areas the most I could take without fear of porting through. In one area, I must have taken nearly 3/16"!

Bolted all this together, and retuned my MegaSquirt to go out for a spin. All I have to say is wow! This thing is so peppy now. A different car! It feels like a true sportswear.

It was a PITA to say the least, but I am super happy with the outcome.

Obligatory pics below.

[Tippy]

[Tippy]

[Tippy]

[Tippy]

[Tippy]

[Tippy]

[JohnJL]

Want to sell the remains of your ITB collection?

Also, be very very very careful with that Mustang tb. I have the BBK version of that exact one and it lunched my supercharger. There are a number of "freeze plugs" which are interference-fit FROM THE INSIDE OF THE TB. As soon as the TB sees any serious vacuum (like closing the throttle) it sucks those bits directly into your intake.

I hope that saves you some unnecessary pain...stake those plugs, or refit them from the outside...

[Tippy]

Originally Posted by JohnJL

Want to sell the remains of your ITB collection?

Also, be very very very careful with that Mustang tb. I have the BBK version of that exact one and it lunched my supercharger. There are a number of "freeze plugs" which are interference-fit FROM THE INSIDE OF THE TB. As soon as the TB sees any serious vacuum (like closing the throttle) it sucks those bits directly into your intake.

I hope that saves you some unnecessary pain...stake those plugs, or refit them from the outside...

Holy crap, John! Sorry to hear.

Fortunately, this one has no plugs in it. It's just a barrel with a butterfly.

To your point though, the butterfly screws were NOT staked. I did stake them. Thanks for the concern.

PM your email address about the ITB's.

[kenikh]

Pretty dope. Cory, I still owe you a hotside for a K27. PM on the way.

[pkabush]

Wow! That's super cool. The spacer came out sweet. It's funny how easy these kind of projects look when I'm sitting on my ass looking at photos.
What inter cooler are you using ?

[Tippy]

Originally Posted by kenikh

Pretty dope. Cory, I still owe you a hotside for a K27. PM on the way.

Sure. How do I get the dimensions of the turbo of choice? You have dimensions?

If so, I'd love to try it.

[Tippy]

Originally Posted by pkabush

Wow! That's super cool. The spacer came out sweet. It's funny how easy these kind of projects look when I'm sitting on my ass looking at photos.
What inter cooler are you using ?

Funny you ask, I'm going to make a 30" wide by 5" thick one.

Never ending flow and heat dissipation will never be a problem with this one. One and done is the end goal.

Haven't found a welder yet that I'd let touch it. It's going to be 100% fabricated from scratch minus the core.

[Tippy]

Installed on car shot:

[boosted79]

Nice job. Is the 431 hp w/o an IC??

[kenikh]

I think I see a water meth port.

[puddy]

Wow thats really cool Tippy, one day i'm going to go EFI on my 3.3 turbo and its threads like these that i'll be referring back to.

[Tippy]

Originally Posted by boosted79

Nice job. Is the 431 hp w/o an IC??

That was with a 60-1 HiFi turbo and intercooler peaking probably at 1.2 bar many years ago.

It's a helluva lot more powerful now with a Borg Warner S366 and 1.4 bar.

[JohnJL]

Very nice.
Gerhard at Bell made me a nice custom intercooler that fit my cut-and-turned 3.2 intake for a very reasonable price and it supports 425+ hp.

[Tippy]

Originally Posted by kenikh

I think I see a water meth port.

I have a kit, but will not install it.

Intercooler for me only.

It's the IAT/MAT (inlet/manifold air temp) sensor.