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Discussion Starter · #1 ·
Hey everyone.

In the ongoing process of this NA build of mine, I'm at the point where I'll be assembling the parts I've most recently acquired.

To recap, I have an NA d16z6 making 156whp on a Mustang Dyno. I need to decide if I'm going to use a 68mm throttle body or a 60mm given the upcoming setup.

I don't want to restrict airflow but I also don't want to make it too large.

I'm likely going to use 2.5" intake tubing either in short-ram or CAI format.

Here are the important details.
Current:
- d16z6
- 75.5mm P29 pistons
- ported and polished z6 head
- Rocket Motorsports stage-4 camshaft
- Rocket Motorsports springs and Ti retainers
- 255lph Walbro fuel pump
- tuned on Neptune

What's going in:
- Skunk2 intake manifold
- Skunk2 air filter with velocity stack - 3.5"
- K-Tuned 410cc RDX injectors
- 1320 4-1 RMF header with 2.5" collector
- Vibrant 2.5" metal core catalytic converter
- Vibrant 2.5" Ultra Quiet resonator
- Vibrant 2.5" Ultra Quiet resonator (as muffler)
- 2.5" mandrel bent exhaust piping

The car is used almost exclusively for open lapping but it is street legal - for now.

So.,.. wutcha think?
 

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I'm admittedly not an expert or egg head. In fact, I'm total noob, but from the info I've seen online I would think 60mm will probably be adequate and I would wager it's possible you'd loose hp going to 68mm

Haven't seen a Dino graph that proves otherwise
 

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Discussion Starter · #3 ·
I'm admittedly not an expert or egg head. In fact, I'm total noob, but from the info I've seen online I would think 60mm will probably be adequate and I would wager it's possible you'd loose hp going to 68mm

Haven't seen a Dino graph that proves otherwise
Wonderful response!

My research (including here on the most invaluable of sites) suggests the same.

Cheers!
 

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hey man. im sure you already have, but if you havent, go check the last page or so of my thread.

cliff notes-ported skunk2 mani 70mm skunk2 tb vs. ported z6 mani, 62mm inlet, 60mm outlet b series tb.

smaller set up made a bunch more low, mid and high power with the same exact peak power. dyno sheet is in the thread.

id say go with the 60mm, its cheaper, will make more power most likely everywhere.

you could also back to back dyno test things, as i have, as we all make educated guesses, but back to back is a sure fire way to see for sure !

gl.

stratton.
 

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I saw a forum on here that said for our motors it's best to go with 2" intake piping (that's what I'll be using and I'm going for 250whp turbo), I think 2.5" is overkill and will reduce velocity. Then port (bevel? Idk the word) your TB inlet to to make a smooth transition to your intake piping and have your TB smaller than the inlet of your intake manifold. That way when air transitions from the TB into the manifold it has a step down to prevent reversion.

That's the route I'm going, with stock Z6 TB. It will be cheaper and should flow plenty for my HP goals, which will require a lot more flow than yours.
 

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Found it!! And ddd4114 SERIOUSLY knows his stuff.

A smaller throttle body will act as an anti-reversion step and capture the pressure waves due to intake valve closing. Otherwise, the energy is lost, and efficiency will drop. If the pressure waves are captured and returned to the engine at the correct time, more air/fuel will be packed into the cylinders. Also, as stated, the cross sectional area and the air velocity are inversely proportional ( AvΔt = AvΔt ). If the flow rate of the engine has not changed enough to justify a larger throttle body, it will merely reduce air velocity and lower efficiency.

The stock intake manifold inlet diameter is 57mm (I hope I measured it correctly :-?), so any throttle body with a larger diameter will be counterproductive. An aftermarket manifold will have a larger plenum and a larger inlet diameter. Since it has the larger plenum, it is still beneficial to use the stock throttle body. Ideal throttle body diameter and intake manifold plenum volume also vary inversely. A smaller throttle body diameter will also create a larger boundary wall at the mating point between itself and the intake manifold (which establishes the aforementioned anti-reversion step).

Overall, there is no "ideal" throttle body diameter that can be applied to all setups. It must work in harmony with the other components in the system. Most often, 56mm is more than enough for our engines.
 

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~62

Stop thinking so hard

Keep it subsonic


@animag, Does he? or do you believe in the turbo encabulator.

All you did is discredit yourself. You didnt need to though





Stratton and Danz are on point
 

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a 56 or 58mm throttlebody would probably suit the setup better, unless you are religiously past 6k rpms
 

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~62

Stop thinking so hard

Keep it subsonic


@animag, Does he? or do you believe in the turbo encabulator.

All you did is discredit yourself. You didnt need to though





Stratton and Danz are on point
Hey, I'm not afraid to admit I don't know it all. Sadly much of my education on engines is from the internet, which we all know is FULL of misinformation. There is still much to learn. Care to explain the reasoning behind your statement? I'm always in for more knowledge :) If I've misunderstood something, I would like to know what.
No clue on the turbo encabulator stuff... Sounds like blinker fluid to me.
 

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Discussion Starter · #11 ·
hey man. im sure you already have, but if you havent, go check the last page or so of my thread.

cliff notes-ported skunk2 mani 70mm skunk2 tb vs. ported z6 mani, 62mm inlet, 60mm outlet b series tb.

smaller set up made a bunch more low, mid and high power with the same exact peak power. dyno sheet is in the thread.

id say go with the 60mm, its cheaper, will make more power most likely everywhere.

you could also back to back dyno test things, as i have, as we all make educated guesses, but back to back is a sure fire way to see for sure !

gl.

stratton.
Awesome info.

I was already leaning toward the 60mm.

Thanks!

Found it!! And ddd4114 SERIOUSLY knows his stuff.
Currently using a stock d16z6 56mm on a y8 IM with the inlet ported to 60mm. The inlet on the Skunk2 IM is 68mm. Previous owner was using a 68mm TB with his turbo setup. I have both the 60mm and the 68mm and gaskets for either.

~62

Stop thinking so hard

Keep it subsonic


@animag, Does he? or do you believe in the turbo encabulator.

All you did is discredit yourself. You didnt need to though





Stratton and Danz are on point
Hard thinking. It's what I do.

a 56 or 58mm throttlebody would probably suit the setup better, unless you are religiously past 6k rpms
The car is really only ever taken out for track days - open lapping mostly. So yup. It likes to live above 6000 :)
 
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