17 replies to this topic

[John Clayton]

Anyone had any success getting more power via a bonnet scoop?

I accept that the Ram Air effect is likely to give a negligible power increase (although I gather that sports bikes gain some benefit at very high speeds), but a bonnet scoop to pull Cold air in and straight onto the Air Filter (rather than hot less dense air from under the bonnet) has got to make a difference, hasn't it?

http://en.wikipedia....wiki/Hood_scoop
"The high operating temperatures in the engine compartment result in intake air that is 28°C (50°F) or more warmer than the ambient temperature, and consequently less dense. A hood scoop can provide the engine with cooler, denser outside air, increasing power."

On rolling roads the engine's usually tested with the bonnet up/removed, and so plenty of cold air's available -not necessarily the case when the car's being driven with the bonnet down.

Details on my rally car's spec are here, FYI:
http://www.theminifo...x...=129848&hl=

[skoughi]

Always wondered if you could make a scoop that sealed onto an airbox so when the car was driven it would create a positive air preasure, thus helping to force air into the carb. Probably would need something like the size of a bucket and would need to be doing 250mph+ before it made any difference!

[bmcecosse]

Vizard records some success with a long 'tuned' inlet pipe which just happened to start at the grille. Cold air is obviously a good idea - but on a rally engine it's more important to keep the dust and stones away!

[Carlos W]

You also want to keep water out, it may do huge amounts of damage if you go through a water splash in your rally mini and it swallows a load

[Dan]

The problem doesn't exist in the first place in a Mini, so doesn't need to be fixed. This has been asked here a great many times. Once a Mini is travelling faster than 9 to 12 mph the air at the back of the engine bay is the same temperature and a higher pressure than the air outside. The car has a massive grille, which is mainly open to the air. Many other cars have a more or less sealed engine compartment, Mini doesn't. To make any difference at all you would have to create a very well flowed solid duct, many Miglia cars run them but they take a fair bit of development and cash to get right.

[new_zealand _minis]

best way i recon is the era turbo bonnet scoop . letting hot air vent at the back . thats what i will be doing along with wraping my lcb

[charie t]

best way i recon is the era turbo bonnet scoop . letting hot air vent at the back . thats what i will be doing along with wraping my lcb

Dan has just explained it is not needed, as the engine bay is vented very well, another reason why heat wrapping is not needed

[MRA]

best way i recon is the era turbo bonnet scoop . letting hot air vent at the back . thats what i will be doing along with wraping my lcb

The bonnet scoop on an ERA or MG Metro turbo was there to cool the carburettor only...... just look at the position of the air intake on both

The cool air over the carburettor helps to stop the fuel from evaporating due to the heat of the turbo, evaporation of the petrol causes starting issues....

Edited by mra-minis.co.uk, 25 April 2011 - 10:11 AM.

[kenzie22]

http://www.eurodrags...notes/pic16.jpg
that should do the job.

[Dan]

Also I seem to remember the ERA scoop causes a depression at the back of engine bay which will have the opposite effect of what you are aiming for, less air will be available at the carb inlet. The ERA of course has its air intake down by the grille, not behind the engine.

[John Clayton]

best way i recon is the era turbo bonnet scoop . letting hot air vent at the back . thats what i will be doing along with wraping my lcb

The bonnet scoop on an ERA or MG Metro turbo was there to cool the carburettor only...... just look at the position of the air intake on both

The cool air over the carburettor helps to stop the fuel from evaporating due to the heat of the turbo, evaporation of the petrol causes starting issues....

Why does my MiniSport inlet manifold have the coolant running through the centre of it? I assumed the heat was there to either stop the carb icing up or to help the fuel to vapourise

[Dan]

The same reason all isolated alloy manifolds should be heated, and are as standard on almost every car in the world. To prevent fuel condensation inside the manifold. It's fuel vaporising in the float chamber and jet that is a problem (hence why the ERA turbo drains its float chamber when you turn the ignition off) not any heat further through the system.

[Ivor Badger]

I reckon the bonnet scoop works. Removed a glass fibre front one day and the car seemed to go better, so fitted a bonnet scoop. The bonnet scoop must be some distance in front of the rear edge of the bonnet as there is a low pressure area at the base of the windscreen at speed. Whether it is a viable road option is debateable.

[Dan]

Did the car have inner wings when it had a GRP front?

[Ivor Badger]

Did the car have inner wings when it had a GRP front?

No, nor support bars on the subframe. Oh blastphemy .