Changing the route into the airbox

[Jesus-Ninja]

I'm looking to improve the feed into the airbox by replacing the trumpet / snorkel that draws air from the lip of the bumper.

I know that there are issues with cone filters as they screw with the flow of air into the MAF. On the basis that I keep the stock airbox / filter and just change the feed of air into the box, am I likely to encounter similar MAF problems?

[kiteman]

http://www.clubvr4.com/forum/showthread.php?t=47157&highlight=engine+cut
Have a read of the above link. I spent a lot of weekends converting my air intake, only to have to reverse it eventually.
I'll try and locate pics of the end result and put them up here.

[kiteman]

http://www.clubvr4.com/forum/showthread.php?t=45279
heres a link to the work I carried out over christmas just gone, and I eventually had to revert back to the original air intake system.
I have to admit I was chuffed with how the pipework looked each time I lifted the bonnet.

[Jesus-Ninja]

Thanks Kiteman :) That's not really what I'm intending to do though. I intend to leave the stock airbox, filter and MAF exactly where they are already, but change the trumpet thing that currently runs from just above the rad (where it's wide and flat) to the airbox (where it's changed shape into an oval).

[kiteman]

Thanks Kiteman :) That's not really what I'm intending to do though. I intend to leave the stock airbox, filter and MAF exactly where they are already, but change the trumpet thing that currently runs from just above the rad (where it's wide and flat) to the airbox (where it's changed shape into an oval).

Any chance you can put together a sketch of what you intend to do, I'd be interested in it.

[Wodjno]

Some Peeps have just left the stock airbox and trumpet. Then drilled extra holes underneath the airbox and attached airfeed pipes to direct air from the front of the car.

[chris g]

IIRC Mazda 323 GTR owners did similar thing and got some benefits and no problems...

[Jesus-Ninja]

There's no room for my stock trumpet, so it's gone. I've now put some pipe work in to feed it from the lower front grill, next to the FMIC. Pipe work is a little narrower than I'd have like, but it's semi-experimental, and if it's all fine, I'll look to do something better.

The CSA of the pipe wotk I've used is about the same as the CSA of the flat end of the stock trumpet, so I've no huge worries about it. It's also the same CSA of the hard pipe coming up from the cold side of the IC, and will be carry air that its both cooler and lower pressure, so it should be OK.

If it's OK, I may look into blanking off the hole in the airbox for the trumpet and put something bigger feeding up into the box.

Will get some pics up in a bit.

[Davezj]

Try these threads mate.

http://www.clubvr4.com/forum/showthread.php?t=43919&highlight=inlet

http://www.clubvr4.com/forum/showthread.php?t=9196&highlight=inlet

sound like this is what you are needing.

[Turbo_Steve]

It's mainly about having nice stable airflow into the MAF, and I'm not convinced the airbox itself forms much of a restriction....the FILTER might, especially as it starts getting dirty, but not the box itself. As has been mentioned, opening up the airbox intake is a really good idea. If you can force positive pressure into th airbox, then so much the better.

[Jesus-Ninja]

Try these threads mate.

http://www.clubvr4.com/forum/showthread.php?t=43919&highlight=inlet

http://www.clubvr4.com/forum/showthread.php?t=9196&highlight=inlet

sound like this is what you are needing.

Good stuff, Dave! :)

[Jesus-Ninja]

OK, here's what I knocked up in a spare 45 mins this morning.

[elnevio]

Looks promising, Nick! :afro:

[Jesus-Ninja]

Looks promising, Nick! :afro:

Thanks, Nev. :) My only concern is that it's maybe a little narrow, so there's not much ramming positive pressure into the airbox. The system will rely more on the tubs drawing the air in with not much assistance.

That said, I don't think there was any ramming in the stock set up, so perhaps it will be fine :) Bear in mind that this wasn't intended as a performance upgrade, more a way of getting round the problem that suddenly appeared when my big rad got in the way of the stock item.

I did consider cutting a hole in the bonnet and drawing from there, and I may yet do so, but whilst I could do a very nice tidy job, I have to keep reminding myself that this is a nice family car and not a track slag! Subtle is the order the day!

[Turbo_Steve]

That pipe is way too small. Sorry, but it's going to limit your power, and possibly increase spool: the factory trumpet is tapered for a reason, and this tapers the other way. Sorry: not meaning to rain on your parade, dude.


Cutting a hole in the bonnet is a continual fantasy of mine: I would love to get a custom one made up in Carbon fibre with an air intake vent, a subtle outlet for the radiator, and ideally either a vent or scoop to cool the rear bank of the engine.

More cooling = more timing.

A nice vent at the front of the bonnet with some large pipework into the airbox = positive pressure, which is always a good thing.

[bradc]

Ferrari 575 style, just offset to one side :)

[Jesus-Ninja]

That pipe is way too small. Sorry, but it's going to limit your power, and possibly increase spool: the factory trumpet is tapered for a reason, and this tapers the other way. Sorry: not meaning to rain on your parade, dude.

Although I measured the CSA of the factory trumpet and it's narrower at the front than it is at the airbox. The narrow flat end is about the same CSA as my pipe


Cutting a hole in the bonnet is a continual fantasy of mine: I would love to get a custom one made up in Carbon fibre with an air intake vent, a subtle outlet for the radiator, and ideally either a vent or scoop to cool the rear bank of the engine.

How do we think that cutting the bonnet to feed the air box might affect the airflow into it? I know there's been much discussion about straightening the air out before the filter. If I were to cut the bonnet, I'd feed straight into the airbox by blanking off the front of it and dropping vertically into the box from the bonnet. No scoop, just a hole with some trim and mesh.

[scott.mohekey]

As far as I know, as long as the stock filter is in the same location and angle in front of the MAF sensor, it should be ok.

[Jesus-Ninja]

As far as I know, as long as the stock filter is in the same location and angle in front of the MAF sensor, it should be ok.

Then let the butchery begin!

[Jesus-Ninja]

Right - not a very empirical test, but went out for a drive today. Air temps are higher than they have been for some time, but the car feels good on initial pick up and responsive on the transition from steady partial throttle to WOT. RUns out of puff a little over 4.5k, but then it always did.

So, not fixed anything but not broken anything, and I can now close my bonnet without removing the trumpet all together!

[Turbo_Steve]

If you decide to go through the bonnet, you have to have a scoop, otherwise the air flowing accross the surface will usually generate negative pressure...not positive.

Interestingly, there is a positive pressure area at the bottom of the windscreen....perhaps an intake here would be beneficial.

Have to confess that I think we really need to get scientific and measure which components are restrictive, and which aren't. I think the biggest issue is the inlet to the front turbo, which will annihilate any benefits earlier on in the intake system.

[Jesus-Ninja]

If you decide to go through the bonnet, you have to have a scoop, otherwise the air flowing accross the surface will usually generate negative pressure...not positive.

Interestingly, there is a positive pressure area at the bottom of the windscreen....perhaps an intake here would be beneficial.

Have to confess that I think we really need to get scientific and measure which components are restrictive, and which aren't. I think the biggest issue is the inlet to the front turbo, which will annihilate any benefits earlier on in the intake system.

Do you mean the wierd wiggley one? In one of the posts that Dave made, someone did manometer tests and found that that wasn't nearly as restrictive as it looks.

[Turbo_Steve]

Just re-read them all, and nobody has tested the turbo inlet pipes for restriction. Yes, I mean the weird wiggly feed into the front turbo: it's FAR from ideal.

Whilst I am a big fan that everyone is trying stuff with intakes, and trying to push the envelope, unless you're actually monitoring the MAF value from the ECU (i.e. EvoScan) then you don't know whether you're flowing more air or not, or how the ECU is reacting in terms of duty cycle / load determination etc.

Unless you've run a manometer over the factory setup (and to my knowledge, nobody has and posted it) and then measure the pressure loss across their new setup....it's not going to achieve much.

I appreciate you're just trying to replicate the factory trumpet on the cheap, and that's fine: you're not looking for a hidden 15bhp.

But changing the inlet for performance gains means detailed pressure analysis of the whole system and detailed ECU logging. An ideal setup would be to have the MAF in between two chambers, both with filters in, and then big 2.5" piping from each turbo to the rear chamber, and a huge 5" inlet to the front chamber.

By the time you've gone to that amount of effort, it would be easier to stick a MAP2 in there and delete the MAF, and run simpler pipe work. See BradCs setup.

The problem is that MAP based load calculation is simply inferior to MAF.