42mm ITB install with dyno

[bullettdsm]

Wanted to get this on here for future searchers (forgot to do it before);

Started with a set I got off a member of 2gnt. Didn't like the runners for race, so I altered them to the shorter intake. Did some machining work with my buddy Steve and came up with 5 1/2" runners for higher power range;

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Compared to this;

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ON THE DYNO:

I was concerned about the size of the TB's (42mm) and apparently for good reason. These TB's would make a super excellent street set-up, but not so much for a high reving strip car. The throttle response is outstanding, the torque curve is higher (than my 219.4whp pull with a single Mustang TB), the power curve is higher, and the power curve is straighter. Sounds great right? Nope, read it and weep; (This is a comparison of the ITB run vs the 219.4whp, 65mm throttle body run);

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The red is the ITB's (hp and tq). While the blue is the 219.4whp, 65mm TB run. You can see how the ITB run stays well above the 219.4whp run by plenty at first (in both power and torque). But as we approach the 6k mark, the ITB's start choking out. By the 6500 mark you have the cross over for the 65mm single TB to take over. The ITB's just fall on their face. They are too small. Oh well, all in the name of science. Though we did gather a bit of information. If I still had a daily 420a, I would be all over these for the street. Look at all the torque and power and throttle response you would have in the range that you would normally drive your car around. And you know what else? These idled. Were talking right about 900rpm with Crower 3's and they idled nice and smooth. Sweet. And obviously, if you change to the C shaped original intake, you should see even more down low.

Just for of research.

MB

 

[Ricardo18]

Very good data. I have a question however. Was this using the same intake manifold? To which TB is it port-matched? Thank you.

 

[GsXdSmKingGsX]

Thats a first! Great job

 

[VelocitàPaola]

Cool stuff, Mark. Thanks for sharing it!

 

[bullettdsm]

Very good data. I have a question however. Was this using the same intake manifold? To which TB is it port-matched? Thank you.

When this set-up was made and dyno'ed, the intake was matched to the 42mm ITB's. When I did the 52mm ITB's, the intake was match ported (and "flute ported") accordingly.

MB

 

[black cotton]

So mark why not come up with a quad 48 or 50mm variation, and try to find the sweet spot? Where your linear curve starts high and ends high? The IDT will in my experiences yield better low end response, so if you were to increase bore diameters to not choke out but not too much where you loose your low end, maybe you might have something!...

 

[doggietom]

This is a awesome article, good job!

 

[bullettdsm]

So mark why not come up with a quad 48 or 50mm variation, and try to find the sweet spot? Where your linear curve starts high and ends high? The IDT will in my experiences yield better low end response, so if you were to increase bore diameters to not choke out but not too much where you loose your low end, maybe you might have something!...

Money, money, money, mooooney..........money

Yup 48's or 50's may "hit the spot". I originally did the 42mm's because (1) they came with the intake I bought and (2) I had heard so much "noise" about these TB's being too big and those TB's being too small, blah, blah. blah. But all these people were arguing was theory. I really wanted to put it down in hard facts. I felt that the 52's would be best for the race car (which seems to be pretty close to the number - after doing a couple of 1/4's with them) so I used that size for the next step up.

MB

 

[polosas]

nice ITB, will need to manufacture that one my self. Good to see that i'm not only one going non turbo