Air box trumpet with or without?

[rab60bit]

Originally Posted by Dorchester2

Very interesting informations but rather a bit too far from my down-to-earth initial questions...

Ah, got carried away with nostalgia, sorry. Me, I would stick with OEM since I would like to believe it was a system designed with parameters i.e. a nice flexible petrol cruiser car with acceptable fuel consumption and a bit of umph should you require it and use the gearbox (manual for me).

[the dutch guy]

Originally Posted by Dorchester2

Thank you for your explanation.
Hence in other words I assume you think it's better keeping the trumpet than taking it off? Am I wrong?

no, you are not wrong. the engi-nerds that did the math know what they are doing.
but any restrictions (especially sound baffels) are reducing the effect so airflow restrictions before the venturi should be removed as much as possible.

I’d leave it how it is, it is was designed to run that way. I’m always suspect of people saying things are better after modding without any concrete evidence other than saying it is better. Is it actually better or are they just convincing themselves it is?

mostly convincing themselfs.

this idea that the car gets faster or "more responsive" is just between the ears. its driven basically by sound. you hear the engine make a noise that people think means that it is actually doing something before its actually doing something. its especially noticable with turbos, you hear the spool up if you remove the sound supression and that makes people think its gotten faster but not realizing that the spool up time has not changed, you just hear a new sound to fill in the wait time and makes you think more is happening then when you could not hear it.

its a clever mind trick that aftermarket air filters manufacturers are basing their whole sales on as most filter replacement dont do shait in terms of power, especially not on proper desinged intakes. if you do get a measureable difference then you know the engineers effed up.

[Dorchester2]

Well I'm easily keen to change when I'm proved I'm wrong.
Another chap years ago arrived at the same conclusion, I quote:

'Mine is an automatic car,taking out the 'trumpet' seems like have less low end torque,but revs past 3500 rpm,seems more lively then before,fuel consumption is noticeable higher...sound level almost the same[i admit i partial deaf].'
'I have decided to put back the 'Trumpet',my fuel economy went up this 2 weeks of trial,from an average of 7.2Km/L drop to 6.7Km/L,also the low end torque is not so good in stop & go traffic,actually the MGR's engineer put a 'trumpet' there has it purpose....not just noise reduction.'

https://forums.mg-rover.org/mg-zt-ro...68/index2.html (#24 & 25)

And it was in... 2008!
I should have read that wise advice before because I've made exactly the same observation.
Hence I've put back in place my trumpet.

Nevertheless the 7 holes drilled in the box bottom are an astute trick which works perfectly & increase the throttle response: it's not at all a 'placebo effect' and has nothing to do with noise which doesn't sensibly change.

[COLVERT]

You would only need the extra holes if your air box was working at its limit and the engine at maximum revs.

If you notice improvements at low revs your standard air box has a restriction.--( maybe a dead pigeon.----)

[Dorchester2]

Originally Posted by COLVERT

You would only need the extra holes if your air box was working at its limit and the engine at maximum revs.

If you notice improvements at low revs your standard air box has a restriction.--( maybe a dead pigeon.----)

I guess the main difference with a 'standard' KV6 is that mine is 100% fuelled with E85 which first is octane 105 & then needs much more fuel at any second to drive (around + 25%) hence the usual calculations & assumptions are biased.

To ease the ECU giving more fuel without any error on the dash, the well-known trick among E85 users is to fool the ECU with a resistor on the air sensor giving a minus result (in my case 24 kOhms = - 29°C) instead of the actual temperature. Hence you are right: in my case air box & engine are working at their limits.

I'm only a pragmatic tester experiencing a different balance between air & ethanol in my 75. I may be the only mad driver in France to do that on a Rover 75 V6 2.5!
And I am definitely sure that more air in the box is the only way to get the best of the KV6 engine with ethanol.
For example one evidence (among others) is that before drilling the 7 holes, when kicking down, with E85 I'd always experienced a short but sensible 'blank' just before the powerful acceleration. Immediately after, the kick down began at once & better without any kind of idle time. That's it.
I leave the experts finding out the technical explanation but it can't be called into question.

And even I've got a nice she-cat at home I haven't got any pigeon in the car!