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Posted: Apr 05, 2009 8:07:20 pm
Pete



Unlike front engined cars the 911 has more difficulty in getting cold air into the engine bay and more importantly into the intake system.  The GT1 has an air scoop incorporated into the roof panel and RUF with its yellow bird cut an air intake into the rear quarters to feed the intercoolers.

What ideas or solutions have you all heard about?

Posted: Apr 10, 2009 1:37:45 pm
Dirty Fuchs



Hi Pete
Here?s something I put together a while ago on the 911 - I?d been trying to get as cold air in the inlet as possible. When we drive we all appreciate how much better the car goes when its cold outside so I have been trying to get as much cold air into the airbox as possible - trying to replicate that feeling but all of the time.
This is mine trumpet stands well high up in the spoiler and is in direct cold airflow. Iinitially thought about smooth outer piping but apparently use this as cold air drawn over the 'fins' on the piping cools it even further.

I have carried out some temperature measurements to see if there is any difference with my mod attempt.
I was quite shocked by the low(ish) temperatures under the engine hood when travelling with the air being deflected down into the bay by the counter directional vanes in the spoiler/lid - made me think about the intake idea. When the car is stationary the bay temp gets a little warm with the hot air rising up (to get out of the grills no doubt) but is dragged back down by the cooling fan.
911 engine bays are quite well 'sealed' between the top (bay) and bottom (underneath) and the only real way out of the bay for air is via the forced air fan. Once you start motoring the whole story changes - colder air rolling over the back of the car and down into the spoiler/grills really drop the temps and to a limit I suppose the faster you go the more cold air is available through the lid......
When you think about it - the faster you go the hotter everything would get - but balanced by the more cold air being taken/rammed in to the bay the laws of physics really work here.
I don?t know about the actual intake temperatures but the inner of the airbox has dramatically dropped with the piping fitted (measured with my fluke probe taped in the water exit hole in the box and cable in through the open window) - I suppose the more cold air being inducted plus the cooler bay temps at speed must drop the inlet track a bit maybe????

The water 'outlet' is in the airbox (cover - pre filtration side) right at the back in the lowest corner - original. Only a very small hole but just enough to get the probe in and then taped on so the measurements should be in reasonably 'still air' but is within the box itself.
My ultimate aim was to get the 'trumpet' just touching the inner side of the bottom of the spoiler intakes (trumpet upright) so the air would be fed directly into the inlet track you know - depression in the pipe - colder atmospheric eagerly wanting to replenish depression maybe with a bit of force behind it.

As you can see the upright trumpet is deep into the spoiler and hopefully directly in the airflow. This is the deepest into the spoiler it could go and it still leaves about 25mm so could take advantage of not only direct air but the circulatory air from the rear end of spoiler over inner lid.
Trials.
I put the original 'snout' back on the airfilter box for comparrison and tried the 911 out - got everything up to working temperature and then put the temp probe into the stock filter box pre-filtration side.
The ambient air temperature was measured at +6 degrees away from the car - no direct sun at all. Standard air box standard snout.
Once the probe was fitted I drove slowly around our village (stop/start in traffic) and the intake temperature varied between 38 - 40 degrees. I then went on the open road and opened the car up and as expected the intake temperature dropped (quickly) as soon as the car was motoring. Strange but there was little difference between 30 and 70 MPH (expected more of a drop) but it sustained a temperature of 24 - 26 degrees. Anything above 70 gave no real difference.

I returned and refitted the trumpet/pipe arrangement as in the picture. Fired the car up and drove through the same circuit through traffic etc. This time the intake temperature was lower measuring 20 - 22 degrees (positive!) then I hit the open road. As I started to accelerate the temperature started to drop (almost like a speedo in reverse) and at 30 MPH the probe registered 12 degrees and the faster I went the lower the temperatures dropped. I never registered ambient temperature at any speed but at about 65mph it measured 8 to 9 degrees - much better.
Did it make any 'power' difference? not too sure if it did really however the car did seem a tad 'snappier' quicker response feeling sound's incredible though - high drawing sound from the rear through the spoiler.
Regards

Dirty Fuchs ;)
You only live once so enjoy it.

Posted: Apr 11, 2009 8:38:09 am
Pete



Nice work.  Thats exactly what we need on here - more technical stuff.

Given the size of the temperature drop I would say there must be more BHP.  It would be interesting to see a before and after dyno.  My estimate would be a 5bhp increase. 

Posted: Apr 30, 2009 10:41:58 pm
andyb



I have been playing about with methonol and windscreen wash additive for quite some time now and have injected the stuff into the air intake of the 911 turbo - I would recommend a squirt every now and then but dont over do it! (gets expensive!) Side scoops can improve air intake performance but it is difficult to pipe up inside the rear wheel arches to retain the air volume. This would be another reason to remove the oil thermostat on the right right hand side of the car!

Posted: May 05, 2009 9:15:32 pm
Pete



Hi Andy

Welcome to the forum.

What sort of power gains are getting with that mod?  Sounds interesting.

Posted: Jun 09, 2009 4:42:30 pm
Dirty Fuchs



Hi All,
been tinkering again..... The cold air induction system I built needed more 'uncontested' air 'force'. I removed the original Carrera tail spoiler and looked at the flat lid. What I noticed was that the very air hungry cooling fan was the dominant draw for spoiler inducted air and when you look at the standard cut away in the lid (when shut) you can plainly see that all air for the cooling fan has to be drawn down through the vent, over everything and down passed the tight fitting lid etc - probably robbing what I was after - the intake air, at atmospheric and uncontested.
I was fitting a turbo spoiler and noticed the vast amount of fitment down the lid. I marked out the size of the new spoiler and saw I could cut a large hole in it to give the cooling fan its own section of the spoiler innards to feed from - thus giving the intake uncontested air, It works really well, it even performs better at the higher end of the revs. The sound is also much better - an uncluttered cooling fan drawing sound, sort of whooshing, but very nice sound.
Here is a picture after cutting and before the spoiler fitment. You can clearly see the difference and what I mean. Now there are two seperate systems - one for engine cooling feeding from the rear of the spoiler counter directional vanes and the top for the intake,,,,, works a treat.
Why didnt Porsche do this in the first place? they do it now with the later models on the induction.
Hey-ho.


With spoiler fitted.


Regards

Dirty Fuchs
You only live once so enjoy it.

Posted: Jun 10, 2009 1:10:15 am
Pete



Hi Kev - You rock buddy.  Totally hardcore. 

What a great idea.  I have a turbo spoiler on mine and air is a much need accessory to my set up.  I think I'll get out there and do the same.  What did you use to cut the hole?

Have you done any more with the temperature proble to see if there is a difference in general engine bay temperature?


I think the turbo boot lid had a bigger apperture?  I could be wrong, and your intercooler :agree: reminds me of the the 935 setup.  Great work Kev.....

Posted: Jun 11, 2009 8:05:50 am
Dirty Fuchs



Hi Pete, et al
Firstly I mounted the turbo spoiler on and marked out the inner mounting. I then checked out the exact location of the fan relative to the lid when closed. Marked that up (plus just a tad more) then drilled one hole in the corner of the mark up. I have a great tool which is an air nibbler,,,, goes through steel like a knife through butter and very accurite (bought from Machine Mart some time ago). This tool doesnt 'cut' the steel (as in a scissors) but punches sort of crescent moon shaped slices as it cuts along - brilliant, but the little bits go everywhere. (wallbash)
Once cut, I then sprayed the whole under lid and top (within the spoiler outline) in matt black - didnt want any shiny bits viewable through the spoiler and also rust prevented the cuts-holes etc.
I havent done too much more on temp measurements, but one thing is definite - the whole thing performs better and although it runs just that tad cooler the big thing I have noticed is the fluctuation of the temperature has almost dissapeared. Yesterday drove down the M5 (quite quickly) and then got stuck in the town traffic/hills in Cornwall, a prime usual up and down of the guage, but not now just an almost constant needle ID.
I suppose the oil cooler ducting from the new front helps also.
I am very pleased with the turnout though - sounds awesome too.
Regards

Dirty Fuchs. :agree2:
You only live once so enjoy it.

Posted: Aug 13, 2009 5:36:48 pm
Pete



Kev -

I think the cut out is a great Idea.  Im set to do the same.  Youve convinced me.

Next time you have the lid off, maybe take a pic with a tape measure in the pic so I can scale it off the picture.

Nice work mate  :happy013:

Posted: Aug 13, 2009 5:51:13 pm
Dirty Fuchs



Hi Pete,
I am picking the car up tomorrow from TT (twin outlet a,la CTR) been built. When I get the old girl home I will do some shots with the tape, from the underside of the lid it will be quite easy to see.
Regards

Dirty Fuchs. :agree2:
You only live once so enjoy it.

Posted: Aug 15, 2009 9:17:09 am
Dirty Fuchs



Hi Pete, et al.
Here are the pictures you requested with regards to the cut out in the rear lid, under spoiler.
You will have to disregard the Wife's freshly tanned skin, but I think you will get the dimension info you are after - you can go a little wider but I wanted to keep some metal around the cut-out and it is just slightly wider than cooling intake and works great.
The new exhaust is cracking by the way - I will be updating the Blackbird thread shortly.
Regards

Dirty Fuchs.


You only live once so enjoy it.

Posted: Aug 15, 2009 11:57:40 am
Pete



Nice tan  :cool:

Im definitely going to do the air mod to mine.

What tool did you use to nibble it out.  Im gonna need to get myself one of those to do the job.

Im also going to get myself a finbreglass relica turbo spoiler.  They weigh in a 30kg, so I'll do it all in one go......

Did you notice a differnece in power or just sound, or both?

Posted: Sep 19, 2009 10:00:41 pm
Pete



I definitely think your onto something Kev.  Look at the intake for a 997 turbo.  Porsche have put the cone filter further back to where your new added ventilation would be.



Maybe the next step is to divert a pipe to the area infront (or as close as possible) of the engine fan?

Posted: Sep 21, 2009 7:37:28 am
Pete



Here's another opition to get some cld air into the engine bay.  Not sure I like the overall look of the spoiler but you can see how you can get some RAM air effect and then channel it on the underside direct to the vici nity of the intake.


Posted: Oct 06, 2009 2:14:12 pm
Dirty Fuchs



Pete, not such a bad idea is that spoiler, though a tad on the dear side. :blush:
Mate has one on his and we piped both sides (used drain pipe across the rear inside the spoiler) and both side intakes feed off into one flexy pipe on the inlet on the o/s of engine. Does it work??? I dont know really as Greg doesnt go fast enough and he wont let me drive it.
The theory behind it works though - I have yet to see a race car without some form of cold air or rampipe system fitted. I am positive if you can seperate the engine temp from the intake temps your onto a winner - nearly every new Porsche (and others) have some sort of similar system.
Mine seems 'snappier' since the mod but I have done several all at once so hard to tell.
Regards

Dirty Fuchs :agree:
You only live once so enjoy it.

Posted: Dec 08, 2009 10:42:16 pm
Pete



Quote: Dirty Fuchs at Oct 06, 2009 2:14:12 pm
Pete, not such a bad idea is that spoiler, though a tad on the dear side. :blush:
Mate has one on his and we piped both sides (used drain pipe across the rear inside the spoiler) and both side intakes feed off into one flexy pipe on the inlet on the o/s of engine. Does it work??? I dont know really as Greg doesnt go fast enough and he wont let me drive it.
The theory behind it works though - I have yet to see a race car without some form of cold air or rampipe system fitted. I am positive if you can seperate the engine temp from the intake temps your onto a winner - nearly every new Porsche (and others) have some sort of similar system.
Mine seems 'snappier' since the mod but I have done several all at once so hard to tell.
Regards

Dirty Fuchs :agree:



Im totally with you on that one Kev.  It has to be right tat if you can seperate the two air temps as well as prove a cold air charge to the intages you have to see an improvement.

Posted: Mar 23, 2010 12:36:40 pm
Steve



I think the GT3 dual cone layout with the positoion near the rear of the engine is the better option, especially given the ram effect of the rear engine lid.  Must be worth a few BHP.


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