VTiR Intake Manifold Question

[jko2]

Hey guys,

I've been told a good mod to do on a B18C VTiR motor is to change out the restrictive intake manifold.

Looking into it, I'm seeing things like "variable length runners" - "seperate throttle bodies" or something related like that to, designed to improve low end performance but maintain high end as well..

What are they talking about? what is so special about the VTiR manifold as is it a pro or a con? I read the Type R intake manifold was "simplified" but yet "flows a lot better".

Can someone help me out?

Thanks

[blk_shadow]

Hey guys,

I've been told a good mod to do on a B18C VTiR motor is to change out the restrictive intake manifold.

Looking into it, I'm seeing things like "variable length runners" - "seperate throttle bodies" or something related like that to, designed to improve low end performance but maintain high end as well..

What are they talking about? what is so special about the VTiR manifold as is it a pro or a con? I read the Type R intake manifold was "simplified" but yet "flows a lot better".

Can someone help me out?

Thanks

Variable Length intake manifold will be found in Integra, Legend, Prelude and NSX.

it is designed for fuel economy and yet optimizing better power and torque.

this 'variable' concept is explained for the "pressurization" of the air entering the intake manifold, the variable here means that the IM can actually create several types of pressurized air to create that power for the engine. this all depending on how fast of the air been flowing thru the IM, thus create different pressurization according to that speed of air and resulting in the engine power output.

the second one is about the rpm that you are at. at low rpm, the air will be flowed thru longer passage of the IM into the combustion chamber, while at high rpm, the air will be flowed thru a shorter and larger passage, therefore more air can be flowed thru.

but more so with the swirling of the air that's been created to distribute the fuel into a mixture to ignite the engine.

While type R's IM has already come with larger plenum and shorter passage. maybe that's why they call it 'simplified'

[B18cEG]

an easy mod to do is to disconnect the vacuum line on the short runner butterflys actuator next to the manifold that way the long and short runners will be used, try this for a while and see wat you think, then put it back to normal and see what you reakon with the differences.

[jko2]

So changing out the VTiR manifold isn't recommended?

[blk_shadow]

if you already have a VTIR integra intake manifold, might as well keep it that way, change the TB if you want to.

but its good if you want to upgrade to integra VTIR intake manifold.

[T-onedc2]

I believe the main reason for the variable length IM is to improve air/fuel mixing at low rpm to achieve more efficient combustion hence improving power and torque as stated above.

I'd expect changing to a Type R IM to decrease driveability in low rpm, so unless you have bigger cams than stock or spend all your time at high rpm then don't bother.

Low down torque shouldn't be so much of an issue in a Type R as it has a lower final drive anyway.

[spoondc2]

The dual runner design is to provide more low rpm torque, and Vti-r do have stronger torque than type-r on low rpm. You may disconnect the vaccum line to make the 2nd runner to open all the time but then you'll lose torque. Try to do a search on honda-tech.com. Ppl compare the difference on dyno and claim that it does lose torque(quite abit) and car actually run slower.

They had also tried to open up the 2nd runner earlier, from 5800rpm to 5500rpm and the car goes faster(Stock Integra GSR). It's something to do on the ecu signals. Try to do a search on honda-tech.com and you'll find heaps of info about it

Hope it helps

[jko2]

Okay, sounds like i'll keep the VTiR manifold as I do like the torquey drivability of the car.

Searching through hondatech didn't get me very far, is there a diagram showing this system and the "IAB"?

So the 5500-5800rpm engine note change is not so much the VTEC cam coming in, but more the IAB butterfly opening for the shorter runner (?)

[T-onedc2]

correct, although when the cam timing switches at 4400 it can be heard very slightly but hardly noticable.

[jko2]

And the type R vtec point? I remember being in a mates type R - vtec was about 5500-5800 and the engine note change was very similar to mine at 5500 or so... surely it is the VTEC cross over? as the Type R IM doesn't have the variable runner lengths (?)

[T-onedc2]

no, ITR has a single short runner manifold, and yes you would have heard the vtec crossover onto the big lobe profile at 5700 rpm.