NA Power: Intake Manifold Volume Solution?

[majjbjohn]

Originally Posted by MurderousPandas

Shifts the powerband back about 500rpm and adds some midrange torque and a pinch of hp. It's good for those who want to keep NA and close to stock, but in the long run not too great. After so many mods, the BPB doesn't do much besides raise the manifold up an inch. I still have mine on as i am too lazy to remove them, no need to at the moment.

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curious what mods do you have currently?

[SuperTom]

Originally Posted by MurderousPandas

Shifts the powerband back about 500rpm and adds some midrange torque and a pinch of hp. It's good for those who want to keep NA and close to stock, but in the long run not too great. After so many mods, the BPB doesn't do much besides raise the manifold up an inch. I still have mine on as i am too lazy to remove them, no need to at the moment.

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Well that's mostly what I want is to boost up the middle. I guess what I was asking if there were actually gains, just not the power from uptop being shifted back. Im OK if there are no top gains and only gains in the mid, Just don't want a loss. If I remember from studying years ago lengthening intake runners gives more low end, shortening runners gives more top end in "General".

[Teseo]

Originally Posted by SuperTom

Well that's mostly what I want is to boost up the middle. I guess what I was asking if there were actually gains, just not the power from uptop being shifted back. Im OK if there are no top gains and only gains in the mid, Just don't want a loss. If I remember from studying years ago lengthening intake runners gives more low end, shortening runners gives more top end in "General".

We have same thoughts regardless of useful power, i guess crawford fill the bill but its hella expensive for what it is. I would rather use the money on final gear swap

[MurderousPandas]

Originally Posted by majjbjohn

curious what mods do you have currently?

GFB pulley kit, tune, E85, BPB, KN filter, SuperTek tube, catless UEL headers, catless over/front pipe, and i think that's it in terms of power mods.

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[majjbjohn]

Originally Posted by MurderousPandas

GFB pulley kit, tune, E85, BPB, KN filter, SuperTek tube, catless UEL headers, catless over/front pipe, and i think that's it in terms of power mods.

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how much of a difference is there with out e85

[SuperTom]

Originally Posted by Teseo

We have same thoughts regardless of useful power, i guess crawford fill the bill but its hella expensive for what it is. I would rather use the money on final gear swap

Ive seen used for half that but right now my dilemma is finding out if they will line up with the new '17 red manifold. I know someone had issues with the TB spacers

[MurderousPandas]

Originally Posted by majjbjohn

how much of a difference is there with out e85

Not too much, just a little difference until 4th gear. 4th gear pulls just like 3rd and 2nd on corn, but dies on 93.

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[wparsons]

Originally Posted by CSG Mike

It's a volume vs flow issue. I can verify that the IM is indeed the limiting factor.

For the torque dip, or across the RPM range? I was simply saying I don't agree that the torque dip is caused by it.

[Williampreza]

Originally Posted by wparsons

For the torque dip, or across the RPM range? I was simply saying I don't agree that the torque dip is caused by it.

The high rpm loss of VE is my primary concern, but some suggest that the torque dip is influenced by the same. This is possible too, if the pulses from intake valves closing, piston action, and exhaust begin to interfere with each other in that rpm range.

The fact that the dip is "nearly" eliminated and not completely gone is a further indicator that it is a function of airway harmonics and not just a simple flow issue. That is, free-flow exhaust is boosting exhaust scavenging in that range, but not resolving a fundamental loss of harmonic supercharging effect at that point.

I can't back this up with data, but my suspicion is that the "dip" is not a dip at all, but rather an indicator of a bimodal torque boost, with one wave in the low rpm range and one from 5000-7400.

All of this is still purely speculative, and that's the point of my post. It would be EASY TO TEST whether the plenum is the problem or not using the method I described.

[guybo]

The proof that it's not the plenum causing the torque dip is that a lot of people have gotten rid of the torque dip by messing with the exhaust, tune, or fuel and never touching the plenum. If the plenum was the problem than getting rid of the cats tuning the car wouldn't help.

Other flat NA engines suffer from a Tq dip as well
http://www.ft86club.com/forums/showthread.php?p=1667154
http://www.planet-9.com/987-cayman-a...orque-dip.html
http://cdn2.bigcommerce.com/server61...0.1280.jpg?c=2
http://www.caranddriver.com/reviews/...al-test-review

This is an inherent trait with boxer engines. If the solution was to strap on a bigger plenum don't you think Porsche or Subaru would have done this a while ago? It's too simplistic.

[Williampreza]

Originally Posted by guybo

The proof that it's not the plenum causing the torque dip is that a lot of people have gotten rid of the torque dip by messing with the exhaust, tune, or fuel and never touching the plenum. If the plenum was the problem than getting rid of the cats tuning the car wouldn't help.

Other flat NA engines suffer from a Tq dip as well
http://www.ft86club.com/forums/showthread.php?p=1667154
http://www.planet-9.com/987-cayman-a...orque-dip.html
http://cdn2.bigcommerce.com/server61...0.1280.jpg?c=2
http://www.caranddriver.com/reviews/...al-test-review

This is an inherent trait with boxer engines. If the solution was to strap on a bigger plenum don't you think Porsche or Subaru would have done this a while ago? It's too simplistic.

That's fine and reasonable, but still a side note. My main interest is getting air into the engine at higher than stock rpms. I'm sorry I didn't make that as clear as I intended, since people seem to be getting hung up on it.

To clarify, again, I'm looking at a simple way to explore the possiblity that at high rpm's (above 7400) the reason the engine is running out of air is that the plenum is not large enough. My rationale for why this is a possibility is explained in this article which greatly simplifies some parts, but overall presents an accurate description of tuning an intake manifold as a Helmholtz resonator.

[CSG Mike]

Originally Posted by wparsons

For the torque dip, or across the RPM range? I was simply saying I don't agree that the torque dip is caused by it.

Flow up top, past the torque dip range. For a stock engine, 5500+ RPM.

[Jrdad]

Originally Posted by CSG Mike

Flow up top, past the torque dip range. For a stock engine, 5500+ RPM.

Have you seen any difference between the black and red IM?

[wparsons]

Originally Posted by CSG Mike

Flow up top, past the torque dip range. For a stock engine, 5500+ RPM.

I'm 100% with you on that! I'm only skeptical on the dip being caused by the intake manifold.