Raised Bonnet to Clear ITB's

Hi,

Just looking for some advice please.

I am thinking to raise the bonnet at the back in order to accommodate my long ITB's setup as I currently can't fully shut the bonnet due to the air filter getting in the way, so its being driven (minimally) with the bonnet not clicked in fully.

Will the raised bonnet cause any issues?

I've done some research and some people say that it can cause reduced air flow over the radiator - not sure how much of an effect this really is or whether people make a big deal out of it since some people do the 'raised bonnet' mod purely for better cooling, and so it can actually have the opposite effect!

My ITB's setup is currently around 415mm long which is supposed to be the ideal length for a car that revs to 7.6k (according to Jenvey lol) so I'd rather not shorten the inlet length.

Any help is appreciated.
 
Aerodynamically the base of the windscreen is an area of high air pressure, this is why cabin air vents are often put there, to improve airflow through radiators you'd want low under bonnet air pressure so given this a raised bonnet is unlikely to assist cooling whilst moving at any sort of speed, it could help by letting out hot air whilst stationary.
I've been using a raised bonnet on my mini for a few years now with no effect on cooling although the mini's radiator placement is unusual.
The high pressure area would help feed a set of ITBs with cold air, but I think we've talked about this before...
 

pollyp

Club Member
no cooling issues with mine when it was turboed after lifting the bonnet, especially since I upgraded to a 26mm thicker automatic radiator.
I tested the aero and at high speed the middle bit was stale turbulent (probably blocked by the large TB elbow pipe) while the outer edges around the A-pillar had very high flow

https://www.micra.org.uk/threads/pollymobiles-rebuild.35251/post-683082

my main purpose was to allow the heat off the turbo to easily escape when stationary, yet still shield the bay from the elements. both factors were fulfilled.

it's important to fit a plate or seal to the exposed RH side of the rad so that the high pressure incoming air is forced to flow through it rather than around it.
 
Aerodynamically the base of the windscreen is an area of high air pressure, this is why cabin air vents are often put there, to improve airflow through radiators you'd want low under bonnet air pressure so given this a raised bonnet is unlikely to assist cooling whilst moving at any sort of speed, it could help by letting out hot air whilst stationary.
I've been using a raised bonnet on my mini for a few years now with no effect on cooling although the mini's radiator placement is unusual.
The high pressure area would help feed a set of ITBs with cold air, but I think we've talked about this before...
I think @pollyp has raised his bonnet. I have done this to out ZR and it works fine.
no cooling issues with mine when it was turboed after lifting the bonnet, especially since I upgraded to a 26mm thicker automatic radiator.
I tested the aero and at high speed the middle bit was stale turbulent (probably blocked by the large TB elbow pipe) while the outer edges around the A-pillar had very high flow

https://www.micra.org.uk/threads/pollymobiles-rebuild.35251/post-683082

my main purpose was to allow the heat off the turbo to easily escape when stationary, yet still shield the bay from the elements. both factors were fulfilled.

it's important to fit a plate or seal to the exposed RH side of the rad so that the high pressure incoming air is forced to flow through it rather than around it.

Thank you to everyone for the help, really appreciate it.

I've read through the blog with your link Paul, very interesting experiment, thank you for the advice as well :)

I'm going to go ahead with it now.
 
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