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Discussion Starter #1
Morning fellas,

Hopefully this thread is as successful as my on from yesterday.

I'm using a b16 throttle body on my y8 intake manifold. I never ported the manifold to match the intake so I pulled it off 2 nights ago to do exactly that. So before I went crzy with a dremel I did some research first and now I'm confused.

I stumbled upon this thread: Porting and polishing y8 intake...any science behind yes or no? - Honda-Tech

If you go down to post #10 Owneyboy states that for all motor/boosted setups you should leave the lip after the TB for anti-reversion (which is new to me, yay learning!).

Then I find this thread: Throttle Body boring / intake manifold port matching - Honda-Tech

And that guy also brings up anti-reversion but what he does is the exact opposite from what Owneyboy is talking about. He makes a lip at the entrance of the throttle body going reverse of the natural flow of air. Take a look at his pictures to see what I'm talking about.

So do I port match or not? I was just planning to match the plenum to the TB and remove the "wall" at TB inlet. And MAYBE gasket match the intake where it meets the head.

Can someone please set me straight on this before I send an entire evening tonight reading old threads?!?
 

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A Captiva Blue Si Ha
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seems like it would be a good idea to go slightly bigger on the manifold. like opening up the intake manifold to 61 or 62 mm to give any reversion a slight lip to fight against trying to go back out of the 60mm throttle body.
 

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Discussion Starter #6
Thats a good question. What first came to my mind was cam overlap. Maybe you can add some information since it seems like you know something?
 

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MuthaFuckaUppa
2009 Civic Si Sedan
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It is a combination of things.
When the cylinder is exhausting the pressure can still be higher in the cylinder than the incoming air when the intake port opens. Overlap can help reversion, but it is mostly caused by poor scavenging on the exhaust. As RPM can affect the tuning of both exhaust primaries and intake runner length, reversion is also affected by RPM. You may only “see” it at a certain RPM.
Ideally you should only see slight reversion near the intake flange on the head, if you have it further up, you have bigger issues in the exhaust that the throttle body won't help.
 

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Think of the pulses like people trying to move foreward in a line, they are not directly connected, but they all influence each other. Think of the anti reversion steps as stairs going down and foreward, which make it easier to move forewards than backwards.

So even if someone at the front of the line is on flat ground, and they themselves dont have to immediately climb "up" the steps if they try to reverse direction, the steps still make it harder for the entire line to move backwards, which makes it harder for anyone at the front to reverse direction.

Hopefully that made sense.
 

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Discussion Starter #9
That does make sense, thanks.

So would I want to make the plenum opening larger than the TB exit?
 

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The Great Weldini
91 civic
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do not enlarge no bigger than 1mm

 

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You can do them at every connection. TB to intake, intake to head, head to header, then for the exhaust joints you want the later pipe to slip over the earlier pipe, in fact some header companies make a few connections in the header primary tubes to act as anti reversion steps.

As Remoer said, these do not have to be a big difference, nor does the taper have to go a long way in.
 

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Discussion Starter #14
I don't think I'll be doing it at the runners since I'm not looking to pull the head off so I'll just port match the runners for now.

As far as the exhaust I know hytech has those antiversion flares in their headers, I just didn't know what they were for until now lol.
 

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Anti-reversion is very important for exhaust - exhaust gasses moving back in the cylinder don't create power. Anti-reversion for the intake is not very helpful for an NA intake - the main goal is to allow this movement to help set up pulses that bounce back from the plenum to literally ram air past the valves.

If you want to see how Honda applies this, look in their TB's. Everyone seems to miss this, but they all have a 0.5mm step just past the throttle plate. Their plenums are also slightly larger than that TB step, but mostly to allow for slight misalignment of the TB since there are no locating dowels.
 

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The Great Weldini
91 civic
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You can do them at every connection. TB to intake, intake to head, head to header, then for the exhaust joints you want the later pipe to slip over the earlier pipe, in fact some header companies make a few connections in the header primary tubes to act as anti reversion steps.

As Remoer said, these do not have to be a big difference, nor does the taper have to go a long way in.
thank you, and yes just small changes, did it for me in my build.
I don't think I'll be doing it at the runners since I'm not looking to pull the head off so I'll just port match the runners for now.

As far as the exhaust I know hytech has those antiversion flares in their headers, I just didn't know what they were for until now lol.
its hard to explain on how it changed but in the long run, for all the small steps, and adjustments i did, it really, really goes a very long way. whats funny was that other car people used to say my car does not sounds like most Honda. it had its own distinct tone and it felt very good. and most of all there was really no tune and it ran amazing. just a smooth fuel mappings
 
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