Porsche 911UK Forum

Welcome to the @Porsche911UK website. Register a free account today to become a member! Sign up is quick and easy, then you can view, participate in topics and posts across the site that covers all things Porsche.

Already registered and looking to recovery your account, select 'login in' and then the 'forget your password' option.

I need to vent!!!

Eldavo

Well-known member
Joined
21 Aug 2013
Messages
307
So I picked up a replacement bonnet and dropped it off alongside Igaffz' and Mr Bacchus' cars:

 
Intriguing plan. What is the objective?

Just wondered as I played around with vents on my Westfield and we found that the high pressure area in front of the screen was sufficient to push air into a vent if it was high up the bonnet, rather than extract it. Just a thought.
 
Plan is to suck some of the hot air and pressure from underneath the bonnet by placing the vents in a low pressure area between points 13-16.



The vents sit directly over the exhaust manifold on the driver's side and the Turbo on the passenger side too.
 
Gary was telling me about the vents the other day, should look cool 8)
 
I'll be keeping an eye on this Dave, should do the job :)

Is Gary pressing the vents in or cutting the bonnet and trimming over with a pre-formed part?

I see you've been sketching the outline of a NACA dust too? Are you going with both?

Chris
 
Haha - I wondered who'd spot the Naca sketch. No, there's no Naca duct going in this bonnet - I want air out not in. The 924 Turbo had a Naca duct in the bonnet as did the 968 RS but they're no use on a '44.

The sketch is there from somebody explaining how he used to make Naca ducts with a Dremel.

The vents are fibreglass, Garry is cutting out the vent areas as they're supplied uncut. He'll be cutting holes in the bonnet (hence the spare bonnet) and dropping the vents in but they don't sit flush, they sit a few mm proud of the surface. The instructions advise against fitting them flush as the lip helps create a low pressure zone over the vents.

My car is still at D&G and is nicely mucky so I could measure up where the vents need to go and draw them in (don't worry Chris, I'll be machine polishing the bonnet before storing it!).

Garry has all the measurements now, so will be on it (like a car bonnet?) next week :)

 
Should end up like this, just not red!

 
Will watch with interest. Should look neat.
 
I'm a big fan of the uncluttered lines of the 944 and prefer it without the shouty vents. However, the engine generates a lot of heat - Porsche dropped the under-bonnet insulation on the later cars to try and alleviate the problem somewhat.

Coming off track and opening the bonnet is like opening the oven door and sticking your head by it so I'm hoping that when painted and fitted the vents aren't too obvious as it is function over form on this occasion.
 
Great attention to detail as per usual Dave! Very impressive.

How will you monitor any difference? Will this be just on oil and water temperature 'before' and 'after' with static ambient air temperatures?

I assume you are running without undertrays?

Have you seen anyone wrapping the exhaust manifold in order to minimise heat gains under the bonnet?

Looking forward to seeing the finished article.

Cheers, Keith.
 
You know you want to paint it and the whole car red :puh:

You could always fit one of these for track? I built one years ago from a knackered headlight, for the 1/4 mile, but never got round to fitting it before the 'box and clutch went. Wasn't a Skyline tho :nooo:

Chris
 

Attachments

  • httpphotoscakfbcdnnethphotosaksnc1hs262snc18929_135983759546_502209546_2467602_4528715_njpg_166.jpg
    httpphotoscakfbcdnnethphotosaksnc1hs262snc18929_135983759546_502209546_2467602_4528715_njpg_166.jpg
    64.3 KB · Views: 10,179
It's imperative that all 3 undertrays are in place to create a low pressure area at the bottom of the firewall, if they're not then you create more front end lift by the air under the car going up into the engine bay.

This is why the Turbo also has the two plastic undertrays behind the front wheels that direct the airflow under the car to the rear splitter too.

I've not really thought about how I'll monitor the temperature difference and not sure I'll bother either - McDonald's spend a lot of money modelling people flow to ensure that their stores get maximum footfall, so opening up next door is never a bad idea. Similarly Patrick Garvan's 944 Turbo competing in th Australian Time Attack series is pretty much the fastest '44 in the world and he's spent a lot of time and money on aero. If he has the same vents in the same place (and he suggested them to me) then that's good enough for me :thumb:

Whilst I've seen the exhaust manifold wrapped it's generally not a good idea on the stock system as you can get localised hot spots and this causes cracking in the manifold.

My last 944 was red, been there and done that - Zermatt Silver isn't my favourite colour, if I ever went for another colour I'd either get it wrapped Riviera/Monaco Blue or Alpine White with big feck-off Martini logos and stripes.

There is an evolutionary long term plan whereby the car will move to a MAF system and the air filter will move back to the cold air feed from the wing, this will free up the area behind the intercooler which would allow me to fit a 968 RS-style central vent to increase intercooler efficiency and further reduce under bonnet pressures and temps. This would probably require a fibreglass bonnet though as the original one has a strengthening bracket right down the middle. So, ram-air feeds or ducts aren't needed, plenty of air gets into the engine bay via the intercooler ducting and radiator - it's getting it out again efficiently that's the tricky part.
 
Brilliant explanation Dave!

I was half expecting you to say that dataloggers were going to be used to measure the improvements to engine bay temperatures.

Btw, I like your car colour. Chris is just biased (understandably).

Cheers, Keith.
 
Holes have been cut and the vents have been test fitted:



Now they need opening up and a bit of prep before being glued into place. Then a shoot of paint and finito!
 

New Threads

Forum statistics

Threads
124,357
Messages
1,439,489
Members
48,717
Latest member
Atlas.997
Back
Top