Type-S Intake

Honda puts a lot of time into the design of its air intake systems, and on their performance models it is not un-usual to find a very sophisticated set up. It is common practice in the aftermarket scene to replace the factory system with 3" intake pipes and a large cone filter. If it was that simple, and far superior, why didn't Honda leave it that way you may ask? Well, because there is a better and more efficient way.

In some circumstances these aftermarket intakes do offer some gains, particularly in colder weather. It is usually in the higher rpm's and at the expense of losing some torque and throttle response at the lower end of the power band too.

Honda tries to optimise both the low end performance and the high end, with the use of a variable length intake tract. A longer intake tract helps torque at lower rpm's, whilst the opposite is true in the high rpm's where a short least-restrictive route is optimum. 

Take a look at the following pictures of the intake pipe and resonator from a 95 Prelude VTEC. Remember this is the part of the intake you cannot see. It is mounted under your air box and inside the inner wing.

What you see here in the picture is an upswept double channel intake pipe which connects to the bottom of the air box in the engine bay.

There is a bottom section which is the resonator, which performs two functions. One thing it does is quieten down the intake roar (which is desirable for a road car) and the other is it acts as an air buffer or air reserve for sudden throttle openings which would otherwise disrupt the air flow impulses. 

The clever part of the design is that under normal driving conditions one of the channels in the intake tract is closed off with a plate (a bit like a throttle body), hence providing good low end torque. When the throttle position is fully open and the rpm's approach the point where VTEC is about to switch over, the plate in the intake tract is opened to allow both intake channels to supply air for the higher power bands.

It's a very clever design, which is what Honda are great at.

You can see in the middle of this next picture the device situated on the intake trumpet where it joins to the oval section which forms the bottom of your air box when looking from the engine bay.

This device is driven by air vacuum created from the intake manifold and controlled/activated by the ecu. The plunger is drawn in under vacuum which operates the mechanism to open the plate inside the intake pipe.

 

 

Let's now look at the upper section of the air box and intake ducting as fitted to the Prelude, in particular the improved version as fitted to the latter Prelude's and the Type-S.

I was looking for the type of air box fitted to the Prelude Type-S in Japan. This is what Honda did to the intake to try extract the maximum performance for the Type-S. If it is good enough for the Type-S then I wanted it to fit on my Prelude.

This is what one write-up had to say... 

" Honda felt that it would need to improve on the intake path to compliment the increased high-end performance of the Type-S. The air intake box was made into a funnel shape -- utilizing what Honda calls dynamic chambers ." 

Here are the differences between the standard Prelude air intake and the one developed for the Type-S and used on 1999+ models...

Here are the parts I acquired ...

I found out that 99+ Prelude VTi's had this type of air box, so I enquired of someone who had bought an aftermarket intake, and offered to buy their redundant air box and piping. This I managed to do ( thanks Kevin ), and now I have fitted it to my 4th Gen Prelude.

 

I have since fitted a K&N panel filter to the air box to improve the breathing.