At this point in my Coupe experience I've decided to try and enjoy my car in its standard form for as long as possible. The last owner fitted a larger exhaust, which I don't mind as it makes the most of the engine note, but it also has a K&N cone air filter. Someone has suggested these filters zap the lower down torque, so I'm thinking of changing back to the original. Would be nice to hear the engine note without the whoosh too. Or will I be making a mistake?

This is quite a interessting topic, im sure people will be along to discuss
My opinion is that less inntake resistance only is a good thing. Its the exhaust resistant that can play into effect at lower range.
That said, im aiming for 350bhp using the stock airbox with sport filter and some extra holes.

I did find a noticeable difference when I swapped back to the airbox after running a cone filter for many years. Better low end with the airbox. Not sure how it affected the top end in return, but nothing noticeable...or maybe i'm just not running that much power to make a difference in top end performance anyway.

I agree

When I put the airbox back on my car it was a lot less sluggish off the lights

I put a k&n on my coupe and it killed the low down power , I installed a gtec chip and it was back to normal but with a lot more kick .

so yes they do .

I would be wery interrested in getting an explanation on how and why this happens. As i see it the only explanation is that it throws the mapping wrong due to the increased amount of air entering the engine at the same vacuum. So not because of less ressistance in the airfilter. Could even be that it sucks hotter air.

I can see that some exhaust back pressure can help to stop fresh gas/fuel mix to exit via the exhaust and therby up the low end efficiency. But i cant find one good explanation on why it would benefit the engine to get less air in..

And yes i know im being difficunt

I found mine spooled a bit faster but can't recall any low down power loss

Also curious to know, because just not sound logical to me.

I asked a similar question when deciding whether to drill the air box on my Vis (n/a), how can more air getting in make performance worse?
Barnacle gave a great explanation on this here thread.
I drilled four discreet 1" holes in the sides of the box anyway. A little loss of low end power but a gain in lovely noise and mid and top end power.

Yes, saw the thread, great post and very well explained! How ever that is on a NA engine. These have resonators that is finely tuned along with the rest of the stock intake system. The turbo dont have this feature.

I'd have thought that the turbo engine would be in the same position as the n/a before the turbo starts to spool up, coupled with the fact that you're running lower compression so the air will be coming in even slower than an n/a at idle/ low rpm.

However, they sound sooo much better than a stock filter box that any low end power loss is well worth it

Will let you know Huw, we're going back to standard with a K&N panel filter on Rosa, keeping the Cybox exhaust and Flea plug & play chip, now that makes one heck of a difference.

John

Heck of a difference to what? And because of a good chip or stock af box?
And why?

Flea's Plug & Play chip for a 20V NA, improved acceleration, certainly improved the MPG.
We changed the air intake to a cone, certainly seems to have reduced the lower end torque, so going back to a full system with a K&N panel filter.

Below is taken from Flea's website.

http://www.fcperformance.co.uk/fiat-coupe-bravo-hgt-20v.php

John

Ok i see.. Yes, Flea does exelent work! But again, yours are NA with the resonance system mentioned above. Im interessted in the topic on a turbocharged car:)

A year after posting this thread, I have finally replaced the K&N cone with an original airbox. What an improvement. The car is much more responsive, and I clearly hadn't realised what a pig the car had been to drive recently. The old K&N one had started to make whimpering noises, despite me cleaning and re-oiling it. It was clearly also hindering performance. I now have more torque at the bottom and mid range, which to me is what matters. Suppose the aftermarket stuff is really only beneficial for remaps.

Only thinking this morning about switching my cone back to original box, then I saw this thread.

A friend of mine tested his 20VT (with GT28R) at a RR last year.

Run 1,2 and 3 was with original airbox. Max WHP: 255
Run 4 and 5 was with apexi cone filter. Max WHP: 268