924 Turbo Bonnet on 944T

[J.C944TurboMan]

Have had a 924 Turbo Bonnet fitted recently not just for looks but serves a purpose , allowing cold air to flow downwards onto the hot exhaust manifold . I do think it gives the 944T a more sportier look. Not the best picture , due to heavy down poor the day I collected the bonnet from the body shop , so I drove the 944T with the new bonnet straight back home and into the garage . Any feedback welcome thanks. Best regards J

 

[RC18B 911 turbo]

I really like it very understated but adds a bit of a sportier look at the same time.

Try and get a better pic when/if it stops raining.

 

[944 man]

Not ideal: the early 944/924 bonnet differs to that fitted to the Turbo and late 944s. That said Porsche only offer the later part now, but the internal bracing that matches the firewall is different.

 

[pauly]

ORIGINAL: J.C944TurboMan


Have had a 924 Turbo Bonnet fitted recently not just for looks but serves a purpose , allowing cold air to flow downwards onto the hot exhaust manifold . I do think it gives the 944T a more sportier look. Not the best picture , due to heavy down poor the day I collected the bonnet from the body shop , so I drove the 944T with the new bonnet straight back home and into the garage . Any feedback welcome thanks. Best regards J

Why not just fit a vent on your original bonnet, and I'm guessing but didn't the 924T have the vent there because the turbo was under it ?.

 

[944 man]

IIRC, the 924 Turbo's bonnet differs structurally, which is why people dont simply fit a NACA duct onto a standard bonnet.

 

[Fen]

Sadly it's in totally the wrong place for the 944. You want to keep all the heat in the manifold between the head and the turbo; that's what gives you your boost and why people lag or thermal coat the manifold.

If you want to use a NACA duct it should be on the other side where the turbo itself sits as that is the component with heat rejection issues and that is what warms the inlet manifold, which you want to be as cold as possible. You should also have some means for the air to escape the engine compartment to create an air stream not just a high pressure area. I don't know how the 924 Turbo addressed that but I expect that it did, although it was a very early attempt at turbocharging so maybe it wasn't sophisticated enough.

If you're pleased with it then that's all that really matters, but if it was a performance improvement loads of us would have done it already.

 

[944 man]

ORIGINAL: Fen

Sadly it's in totally the wrong place for the 944. You want to keep all the heat in the manifold between the head and the turbo; that's what gives you your boost and why people lag or thermal coat the manifold.

Agreed: you should be lagging your manifold and up-pipe, not chilling them. Better still you could have them ceramic coated first. The purpose of this is to retain as much heat as possible: that was why Porsche applied (the first ever in a production car, I think) a ceramic coating to the exhaust port in the Turbo's cylinder head.

 

[J.C944TurboMan]

Alright Fen , Firstly thanks for your opinion and very opinionated you seem to be in all areas of the 944 like a Guru , from now on I will refer to you as O Worthy Guru ! Anyway I have removed the cruise control unit so the air duct intake streams the hot air rising from the extremely hot exhaust manifold and channels the air downwards under the car , therefore maintaining the engine compartment some what cooler . The intercooler at the front of the 944T as you know allows plenty of cold air to stream into the engine compartment , hopefully this cooler air under the bonnet will follow the air flow produced from the NACA Air duct and improve the temperature in the engine compartment , but again I like it and do things to please my self not others thank you O Worthy Guru ! I have already fitted some thermal rap on the exhaust manifolds , but after pushing the 944T at night , I opened the bonnet and I could still see the exhaust manifold glowing bright Orange through the Rap so any cooling in this area is very welcome , if anything to protect the exhaust manifolds from cracking again , common fault on the 944T due to again the extreme heat been omitted from them .But what do I know O Worthy Guru . Thanks best regards J

 

[Fen]

ORIGINAL: J.C944TurboMan


Alright Fen , Firstly thanks for your opinion and very opinionated you seem to be in all areas of the 944 like a Guru , from now on I will refer to you as O Worthy Guru ! Anyway I have removed the cruise control unit so the air duct intake streams the hot air rising from the extremely hot exhaust manifold and channels the air downwards under the car , therefore maintaining the engine compartment some what cooler . The intercooler at the front of the 944T as you know allows plenty of cold air to stream into the engine compartment , hopefully this cooler air under the bonnet will follow the air flow produced from the NACA Air duct and improve the temperature in the engine compartment , but again I like it and do things to please my self not others thank you O Worthy Guru ! I have already fitted some thermal rap on the exhaust manifolds , but after pushing the 944T at night , I opened the bonnet and I could still see the exhaust manifold glowing bright Orange through the Rap so any cooling in this area is very welcome , if anything to protect the exhaust manifolds from cracking again , common fault on the 944T due to again the extreme heat been omitted from them .But what do I know O Worthy Guru . Thanks best regards J

Very little it would seem, on this subject at least.

Firstly you're rude. You asked for feedback and you got it, but because it wasn't positive you decided to be sarky.

Secondly the exhaust manifolds on the 944T don't commonly crack. Usually on those occasions they have done it's been because of the engine mount collapsing and allowing the weight of the engine to bear down through the manifold because it comes into contact with the steering column. Nothing to do with heat, except in an incidental way as that accelerates the failure of the mount. An engine mount cooling system is a bit OTT though, surely?

Thirdly how exactly does the intercooler allow air to stream into the engine compartment? Yes there are holes in the front to allow air in to the intercooler, radiator and air-con condenser, by which time it's quite restricted as well as turbulent. I'd be surprised to hear how it does anything once through the holes than create a mess of high pressure areas and that it escapes where it can, leaving several hot spots. It will be far from a structured flow or stream I can assure you. In any case isn't it you rather than me who has added an extra hole to let more in?

You say you do things to please yourself, and that's great; everyone should, but if you invite feedback after doing so then don't be surprised if you get it. If you want a bunch of sycophants to tell you how great everything you say is then (thankfully) this is the wrong forum for you, but there are plenty of others to choose from in my experience. From an aesthetic perspective I actually think the 924 bonnet looks quite good, but when I looked into it and quickly established it is pointless for any practical reason I didn't fit one to my car, which is my choice, about which I am not soliciting other's opinions because it's truly my choice so they don't matter.

At the end of the day if you're happy then great, and it does look quite good. What I am keen to correct however is your mis-information that it's a performance modification of some sort to cool the exhaust manifold of a turbocharged car, because nothing could be further from the truth.

 

[sawood12]

Wasn't it the case that in the 924T the NACA duct was there to channel air into the intercooler rather than for cooling purposes as the 924T used the a different engine with the intercooler in a different place than on the 944T?

 

[Fen]

I'm pretty sure it didn't have an intercooler at all, but the turbo was on the other side of the engine to the 944T's, hence they put the NACA duct.where the bit that needed the most cooling was.

 

[Diver944]

924T afficionado's will correct me if I'm wrong but I think the series 2 Turbo's (as well as Carrera GT) had a horizontal intercooler mounted under that NACA duct. It is definately wrong to cool the exhaust manifold (which is why so many people wrap them - it keeps the heat and energy in)

I like the way the 968 Turbo S uses a NACA duct to directly feed the air intake box [8D]

 

[andyslade]

Only the Carrera Gt had a intercooler,and that was fed by a bonnet scoop,not a naca duct.Also if i remember rightly,there was something on the underside of the car to encourage airflow out of the bottom of the engine compartment.Also the naca duct let hot air out when the car was stationary.
I think these details are correct,its been 10 years since i owned a 924 turbo!
Andrew.

 

[sawood12]

I've even seen people wrap the hot side of the turbo to retain heat there. Though you want to be cooling the compressor side. It is a misconception that turbos work like windmills, it is the process of thermal expansion of the exhaust gasses through the turbine nozzles that drives a turbo. The greater the temp and pressure difference between the turbine input and output the more efficient the turbo.

I like the idea of two small NACA ducts in the badge panel to feed the intercooler, or even to channel air into the turbo airbox instead of the sideways snorkel.

 

[TTM]

ORIGINAL: sawood12
I like the idea of two small NACA ducts in the badge panel to feed the intercooler

I believe the original opening in the bumper is well located as it faces the airstream perpendicularly, so you would probably have to fit a badge panel with opening(s) big enough to drastically "cut" the airstream in order to force enough air into the IC.

I must say these badge panels with a huge opening do not quite improve the aspect of the car as far as I'm concerned ... [&:]

 

[geoff Ives]

The 924 turbo does not have an intercooler (unfortunatly) that was first fitted to the 924 CarreraThe duct is to allow heat to escape when the car is stationary.
The above applies to both series 1 and series 2 925 Turbo (931).

 

[J.C944TurboMan]

I thought this Forum is for people who own Porsche vehicles in the UK ! Not for righteous Ex Pats on the other side of the world ! Who keep stating how great it is there ! I love GB and would not abandon such green pastures ! (Fen highlighted in Blue)
Very little it would seem, on this subject at least.
( J.C Well Fen I do all the work on my 944T myself Pal , do you ?)
Firstly you're rude. You asked for feedback and you got it, but because it wasn't positive you decided to be sarky.
(J.C you have more or less be Sarky with your replys to my posts , when I asked over that different boot lid you said go on give us all a laugh ! So who is rude Fen me or you !)
Secondly the exhaust manifolds on the 944T don't commonly crack. Usually on those occasions they have done it's been because of the engine mount collapsing and allowing the weight of the engine to bear down through the manifold because it comes into contact with the steering column.
(J.C My car Fen is a left hand drive and the steering column feeds under the Turbo and mates under the brake servo , I have replaced the steering with a manual rack , did it all my self Fen !)
Thirdly how exactly does the intercooler allow air to stream into the engine compartment?
(J.C The air flows through the intercooler and I have fitted a K&N induction so then the air flows directly onto the air filter , so I did not want any unnecessary air to flow forward towards the K&N , so I do believe this small 924 Air duct helps to keep the hot air towards the rear of the engine bay and it also keeps the fuel pipes cool .Also when stuck in traffic the hot air can escape through this Naca Air duct and help prevent overheating .)
At the end of the day if you're happy then great, and it does look quite good. What I am keen to correct however is your mis-information that it's a performance modification of some sort to cool the exhaust manifold of a turbocharged car, because nothing could be further from the truth.
(J.C If this is the case why is it so important to have an Intercooler system to cool air and the performance intercoolers are all aimed to cool the air down . Why is it so important to allow cool air to be drawn in by the air filter , why do they even fit special inlet manifolds that spray water to mix with the intake air so it is more dense to some high performance cars Fen ? I do believe that the 944T needs to be kept at a good working temperature . And this small duct is not just for looks and helps keep the temp. down .The water pipe that runs over the exhaust manifold is in a strange place , do you think it serves a purpose being there , apart from the obvious ! Fen ?) I have posted another more clear picture of the bonnet but the colour is slightly out a shade so will have to buy some new front wings as my ones have the usual rust , then get a full paint job ! When out in the sun light the colour match is not to bad .
I would like to thank you Fen for your opinion and believe me when I say like the Murphy's I'm not bitter !I bet Fen you can not go out on a Sunday and get a top roast lunch over there ! Best regards from J.C

 

[pauljmcnulty]

Fen, Juan, please don't let this deteriorate into "I live somewhere nicer than you and am more knowledgeable than you"? You're both valuable forum members and old enough to be able to chat without falling out over a little bonnet hole! Consider your heads banged together! []

I dunno, you don't get these sort of arguments on Pistonheads....[][]

 

[sawood12]

In the interests of objective engineering with total impartiality, intercoolers are not intended to cool the air before it enters the air filter. It cools air that has been warmed up through the turbo. And the air is not heated in the turbo due to heat from the engine or exhaust manifold - it is heated up due to the process of compression.

Parts of the engine want to stay hot, others cool. I don't believe there is anything wrong with the under-bonnet temps in a 944. The only improvement I would make would be to add some vents behind the intercooler to help drawer air through the intercooler to improve the efficiency of the stock intercooler, other than that I don't see the necessity - other than asthetics - which is as good a reason as any for mods.

 

[944 man]

It is an aesthetic modification and nothing more. Fit it because you like it if you wish, but dont try to persuade us that it has some higher function, because it doesnt. Also, whilst it bolts on, any early bonnet does not fit a series two 944 properly. Personally, I do not think that it suits a later car any more than boxed sill extentions or slotted rear valences.