Engine bay cooling

[Eldavo]

It's pretty apparent that the engine bay on a 944 gets hot, especially on a turbo.

The reason I've been thinking about this is that I've been offered a vented badge panel cheaply. The general consensus seems to be that the scoop inside the bumper cutout does a better job than a vented panel as it's in a high pressure area and that a vented badge panel just increase airflow under the bonnet, airflow that nowhere to go.

So, with this in mind I started to have a think and a research. The D9 vented panels look quite good a good idea as they vent heat from the exhaust manifold and the turbo area: http://www.deutschnine.com/mm5/merchant.mvc?Screen=PROD&Store_Code=porsche-transaxle&Product_Code=D9-944II951S2-EV&Category_Code=porsche-transaxle-944-turbo-s2-aero-dynamics

These, combined with a vented badge panel would move cool air in (and more importantly) hot air out of the bonnet. With the undertrays removed, the engine bay is noticeably cooler and the oil runs cooler too (I have a temp sensor in the sump plug). The undertrays greatly reduce high speed lift so are definitely needed though, I plan to address this with another oil cooler. I have another factory oil cooler and plan to fit it on the opposite side in series with the original at my next oil change. I may also fit a thermostatic valve too and some more pipe work if it's straightforward so that the second cooler isn't in play until it's needed.

The other thing I've looked at is some way of removing hot air from from the bonnet post-intercooler. I've read some of Patrick's old thread on Rennlist with interest, the 968 turbo vent idea is a good one but not that tenable on a 944 turbo. Perhaps something like this: http://www.carbonmods.co.uk/Products/Carbon-Fibre-Bonnet-Vent---12andquot-__CMBSC10001.aspx mounted backwards to vent the air would be good (or would look crap, not sure yet).

Am I waffling or does any of this make sense? Perhaps it's not really an issue and I'm seeing problems where there aren't any!

 

[Lowtimer]

Why do you think you have a problem? You don't actualyl describe anything that could be described as one.
What oil temperature do you have?

 

[Masher]

A bit of my experience in case it's helpful.

I bought my car (2.8L turbo) with S1 front bumper, vented badge panel and 924 Carrera GT bonnet scoop. It consistently lost power on long straights... intercooler not working.

Looked into the whole cooling thing and ultimately the car ended up at EMC for an aftermarket turbo-look bumper to be fitted along with ducting to force the air into the intercooler.

I was advised the vented badge panel did nothing because low pressure air simply skimmed over the vents and as for the Carrera GT bonnet bulge - it was described as an air brake at best! Perceived wisdom was that with the Turbo bumper letting lots of air in the front the bonnet scoop would only let cool air in the back and create an area of trapped, hot, air in the middle.

Now running with turbo bumper, new radiator (though only single fan) and never a hint of overheating (and I've pushed hard on track for 30 min + trying!).

Key to me was the ducting taking air from the low slot in the turbo bumper up to the (high mounted) intercooler. i.e. efficient use of the air coming in through the intercooler slot.

There is a school of thought that forcing air into the intercooler and then ducting it straight out the top of the bonnet aids overall cooling with high performance engines (400+HP). The idea being one flow of hot air (intercooler) is isolated from the other flow of hot air (radiator / turbo). I can see the logic but understand significant modifications are needed to make this work (not least the air filter relocation).

Hope this is of some help,
Mick

 

[Eldavo]

I haven't experienced a decrease in power or a "problem" per se. I tend to see about 120 degrees C on track, but do a cool down lap and leave the engine running with the bonnet open when I come in.

The under bonnet temperatures just strike me as being very high and anything that can be done to diffuse them someway is a benefit in my book. I'm very much of the school of thought that you sort the cooling, etc. out before chasing more power. Before I fitted the DPW and chips etc. I replaced the radiator and made sure the cooling system was spot on.

As I mentioned I've been offered a vented badge panel and I do quite like the look of them but basic physics tells me that the air needs somewhere to come out as well as to go in!

 

[DavidL]

Have a chat to Jon Mitchell. I'm sure he has spent some time working out what does or doesn't give any beneficial changes to temperatures.
Things like the 924 turbo style cut outs are more form than function it seems, certainly on a 944 turbo.

 

[944 man]

A pair of vents on the edges of the bonnet towards the rear will allow the engine bay to breathe. whether a standard car needs it or not is debateable...

 

[T3rra]

If going with the vents I would fit them flush, maybe get cut out from a spear bonnet and have the area pressed in to vents then fit flush.

Engine bay will keep heat in it. My intake temps can increase from 8degs 2 50degs if I pull up at a shop and leave the car still for ten mins. Then takes speeds over 40mpj 2 start bring them down below 24 deg or there about. Even after hours shopping there's still high heat.

What about a cut out in the top off the fire wall letting heat out and over windscreen?

My turbo runs much cooler then my 16v ever did, you could open the bonnet and feel the heat hit you in the face

Personally I would wrap the hot housing off the turbo and try coating discharge pipe and cross over b4 I started putting vents in unless you like the look

 

[Eldavo]

The D9 vent placement is spot on, to near the back of the bonnet and the pressure is positive, where the D9 vents sit is above the turbo and manifold whilst also being in a negative pressure area to suck the hot air from under the bonnet. Similarly, venting from the firewall to the front of the bonnet isn't a good idea either due to the positive pressure in this area too.

My car isn't standard and I plan to develop it a bit further over the next few years! having the exhaust manifold and turbo pipes (and turbo) zircotec coated is something I may do in the future.

I do like the look of the D9 vents but agree that an intercooler bonnet vent would be a bit OTT. Ideally I'd get the vents louvred in with a punch but that seems easier said than done!

 

[944 man]

I wouldn't get the manifold and up pipe coated. Ceramic coating is like wrapping, only better - and wrapped manifolds work better but their life is exponentially shorter.

Not a big deal on an Impreza where manifolds are cheap and plentiful, but a massive financial PITA on a 951.

 

[Eldavo]

Interesting to hear. I've steered away from wrapping as it can create hot spots and problems.

I'd love to get new equal-length manifolds made but that's a long long time away.

I'll start with the oil cooler and some better brake ducting and work my way up to bonnet vents.

Am torn between the mounts that pipe cold air into the brake rotor or the 968 scoops as a cheaper option. I don't really think the standard ducts and deflector plates do much now the car is lowered.

 

[edh]

968 ducts should work just fine and are definitely a cheaper option. You do need the 968 lower arms to fit them properly. Worked well on my turbo (with pf97)

On my s2 I've got 9products ducts to the inside of my discs and stuck some ducting to the fog light holes in the pu.

 

[Eldavo]

I feel a bit of DIY coming on!

http://m.rennlist.com/rennforums/showthread.php?t=354434

 

[chrisg]

Some cooling thoughts/ experience of mine based on visits to the Ring in June/July witth the turbo - I fitted an oil temperature probe into the sump plug to measure temperature. On a very hot day it would get up to 120c even with the fast running on sections of the ring. IMHO you don't really want the oil above ~ 100C so you've a margin of error before it starts to breakdown/ fracture.

So, I did the following - fitted a 13 row oil cooler in series with existing factory oil cooler which sits in front of the water radiator just above the bat wing. At the same time I removed and binned all the AC cooler/ radiator bit ( I know there's a proper name for it...).

I then dropped the drivers side radiator fan off completely thereby providing straight through cooling through the oil rad, into the water radiator and out to the engine bay.

In this way there is straight thru cooling on one side, fan cooling where necessary on the other side.

The way I have the pipe work set up is so that should there ever be an issue with the additional cooler, I can simply unbolt it and plug the factory one back how it was.

Other things to note:

1. On the Turbo (and probably S2 with AC) when you press the AC button on the dashboard it kicks both the fans on a low speed - rationale being youre most likely to use this sitting still in traffic on a hot day.... So you can use this to cool the car in my configuration when stationary.
2. The whole Oil cooler system is thermostatically controlled from underneath the oil filter so you don't need to fit any thermostat - porsche built one in already !
3. On the turbo model, the oil from the turbo is gravity fed into the sump so in effect although the sump gets a lot of cooling at speed (finned aluminium) it also receives the hotest oil from the turbo and oil draining from the block/ crank etc IMHO its a good but not hugely accurate way of checking oil temp as by the time the oils been through the standard or additional coolers and is higting the turbo bearings/ Crank etc it will be MUCH cooler.

Yours

Chris

 

[edh]

I'd suggest you monitor oil temps via a sandwich plate under the oil filter. (I ended up with two oil temp senders in my turbo - sump and oil filter)

There is always a little flow through the cooler, but as Chris says it's thermostatically controlled.

 

[Eldavo]

Good point on the cooler being thermostatically controlled anyway, I should've realised that.

Aircon has been deleted anyway so shiny new radiator has unobstructed air flow.

I'll fit the second factory cooler that I have and get it plumbed in in series, the extra oil capacity will be no bad thing either. I'm guessing as there is always some flow through there as Ed says then I won't need to get the engine up to temp to get oil into the coolers and lines when refilling?

I've steered away from sandwich plates so far after your mixed success Ed, if I find a good one then I'll stick one in and have the temp gauge switchable as you did.

Ordered my 968 brake ducts this morning so will be interested to see how they work although my first trackday of the year is in March at Cadwell so a snow plough may be more useful if the weather reporters are to be believed!

 

[edh]

The coolers fill as soon as the oil gets pumped around the system. You can see that when you do an oil change on a turbo - the lovely clean oil gets contaminated by the residual oil in the cooler (unless you drain the cooler as well). The unions on the cooler (big spanner needed) can be very tight.

 

[chrisg]

Although you've already got a second factory oil cooler, as oil coolers go they're not hugely efficient as they're narrow cross section and deep.

IMHO if you want serious cooling you'd be better off paying out ~ £95 for a flat thin wide 'standard' oil cooler to place in front of the radiator. If it helps I'm happy to take photos of my set up and give you details of the cooler i bought.

Chris

 

[Eldavo]

Pics would be very useful Chris, thanks.

 

[Eldavo]

Fitted the 968 brake cooling scoops tonight, I bought some aluminium from B&Q to make the brackets but lucked out as my car's wishbones already had the mounting lugs and holes in them so they must've been changed at some point at somebody else's great expense!

I already had the turbo vents from the bumper but with the car being lowered the air from these didn't seem to go anywhere near the deflector plates:

Deflector plate vs scoop:

Terrible picture but hey ho, 10 mins to fit either side. I can see how the air is scooped from under the car and directed straight into the back of the disc, the air from the standard bumper vent will also be channeled more effectively into the brake now as well:

Less than £45 for the bits and just by looking at them I can tell that they'll be much more effective

 

[944Turbo]

great, have you got the part numbers handy? something I have been meaning to do for years!
cheers,
Tony