XJ6 & XJ12 Series I, II & III 1968-1992

Cool air intake S3 4.2L

 
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Old 05-31-2016, 05:50 PM
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Default Cool air intake S3 4.2L

I've been considering a cool air intake set-up for my S3 4.2L. It's not that she needs any more "go" really, but an engine that breathes better should logically produce some benefit.

I know there are mixed views about the worth of air intake mods in general, and I understand that air being sucked through a cone filter may not be all that "cool", even with heat shields in place, but FWIW I fitted one to my (now gone) X300 3.2L and it definitely made for a livelier engine (anyway, my brain thought it did, so therefore it did!).

Does anyone have any experience on cool air intakes specifically for the 4.2L? Also, if you are running one, any pics of your set-up would be much appreciated!
 
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Old 05-31-2016, 06:01 PM
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The first step is measuring the temperature of the air at the inlet with the present intake set up. You might find that while it's quite high while sitting idling on a hot day, it will soon drop as soon as the car is in motion. You might actually find that the temp is only a few degrees above ambient, making any sort of cold air intake system a waste of effort.

I measured the effectiveness of the factory cold air intake on my old Corvette and found that it gained me a neck snapping 0.47 HP increase.
 
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Old 05-31-2016, 07:18 PM
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I've done this on two cars, Tony, and I liked the result. But that's just me, purely subjective. Numbers be hanged!
(';')
 
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Old 05-31-2016, 07:22 PM
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Thanks Mikey. Although we refer to these things as "cold" air intake I am aware the drawn air won't be that cold under the bonnet. But they also have the effect of being a more "direct" air intake i.e. less constricted than the stock narrow pipe. Logically, considering more is better when it comes to oxygen, I would see the cone positioned as far forward as possible, on the widest possible pipe.
 
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Old 05-31-2016, 07:28 PM
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Originally Posted by LnrB View Post
....purely subjective. Numbers be hanged!
(';')
Thanks for your thoughts Elinor. It was also my finding on the last car. If your brain is registering a positive result....then the mission is a success!
 
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Old 05-31-2016, 07:33 PM
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And I've just noticed - I'm now a Veteran!! (do we get to wear a medal?? )
 
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Old 05-31-2016, 08:08 PM
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Originally Posted by jagent View Post
Thanks Mikey. Although we refer to these things as "cold" air intake I am aware the drawn air won't be that cold under the bonnet. But they also have the effect of being a more "direct" air intake i.e. less constricted than the stock narrow pipe. Logically, considering more is better when it comes to oxygen, I would see the cone positioned as far forward as possible, on the widest possible pipe.
Again, the stock setups aren't really as restrictive as we might think. The cone filters (all the rage with the Honda f*rt-pipe set) might just be more restrictive than a stock filter.

If you're thinking ram air effect by pointing it forwards, that really has no effect below about 100MPH.
 
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Old 05-31-2016, 08:11 PM
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Just to be a pendant, the jag already has a cold air intake system. That's what the snout on the air filter enclosure is. Adding an exposed open cone under the hood is a hot air mod. It may sound better but it will produce higher intake charge temps than stock.

There's also no restriction in the default system until you reach ludicrous speed and rpm. If you want to improve the flow ( which is of questionable benefit imho ) then remove the snoot and use an extension the diameter of the air filter box opening and run it straight to the firewall opening. Add a K&N in place of the original filter if you like.

There's no room to pipe through the firewall at that diameter and the inboard light cups impinge on the opening so you also can't pipe to the opening in front of the firewall. I did add an extension from a right angle elbow just inside the grill opening that dumps out at the end of the radiator just short of the light cup. This was just to provide a path for cool air to dump at the snout. No high speed pressure on the air filter or anything like that.

The real added benefit of a K&N at the opening of the AFM is auditory. And, as you already said, if it makes you feel faster it works!
 

Last edited by JigJag; 05-31-2016 at 08:13 PM.
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Old 05-31-2016, 09:18 PM
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Tony,
I copied this from my thread, did it last week. Maybe helpful.
I believe it makes a difference. Better sucking cold air from above the radiator than sucking heated air from behind it.
It is also about twice the size opening to suck air.

Cool air intake S3 4.2L-images.jpg

Originally Posted by o1xjr View Post
Dr Phill hooked up this cold air intake for me today, since I had the series 3 top panel on the radiator with the intake tube above the radiator. I picked up an air cleaner cover for $20 that we chopped to suit. Keeping the original with the stickers intact.

Got to be better than the original sucking hot air from behind the radiator.
Cool air intake S3 4.2L-dsc_6465.jpgCool air intake S3 4.2L-dsc_6466.jpgCool air intake S3 4.2L-dsc_6467.jpg
 

Last edited by o1xjr; 05-31-2016 at 09:23 PM.
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Old 05-31-2016, 09:32 PM
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Thanks Clarke, just what I was visualizing, not sure how I missed this!
 
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Old 05-31-2016, 09:55 PM
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Tony, the cold air intake was a simple task. using a piece of 2" flex pipe allows fitment inside the intake tube above radiator panel and the cut the trumpet intake at air filter box to suit sizing. allow a small amount of slack to counteract engine movement. very simple task. has to give more positive benefits than a intake system drawing warm stale air.
 
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Old 05-31-2016, 09:56 PM
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Originally Posted by jagent View Post
Thanks Clarke, just what I was visualizing, not sure how I missed this!
It was tagged onto the "Preparation for track day" thread, I didn't think it was worth a new thread. But now is in yours to be found.
 

Last edited by o1xjr; 06-01-2016 at 02:44 AM.
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Old 05-31-2016, 10:30 PM
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Originally Posted by Dr Phill View Post
. has to give more positive benefits than a intake system drawing warm stale air.
But the numbers don't lie. Somebody please measure the intake vs. ambient temps on a stock system, then measure the temps at the planned intake location, all under the same driving conditions.

Remember, it takes an 11*F drop in intake temp to realize a 1% gain in power. Most drivers don't notice a 5% change in power.

In my tests with the Corvette, I achieved a 1*F drop in temp comparing the 'cold' air intake vs. 'hot' engine air.
 
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Old 06-01-2016, 12:18 AM
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Originally Posted by jagent View Post
Thanks Clarke, just what I was visualizing, not sure how I missed this!
If ya had a V8 ya could do something like this:

Uses the hole for the OEM snorkel slightly enlarged. Perfect fit (after husband reamed it out a bit).
(';')
 
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Old 06-01-2016, 01:20 AM
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Originally Posted by Mikey View Post
Remember, it takes an 11*F drop in intake temp to realize a 1% gain in power. Most drivers don't notice a 5% change in power.
Its not noticeable powerwise, but more the cleaner idle and smoother take off.
When we used to visit the MIL in the colder part of Australia the cold air made the same difference. Always got home saying to my wife how much better the car felt when driving down south.
 
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Old 06-01-2016, 02:27 AM
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Originally Posted by o1xjr View Post
Its not noticeable powerwise, but more the cleaner idle and smoother take off.
When we used to visit the MIL in the colder part of Australia the cold air made the same difference. Always got home saying to my wife how much better the car felt when driving down south.
Yep, that pretty much sums up the gain I had in the X300. I don't delude myself that HP will actually increase! If I get even a slightly smoother idle, that alone will be enough to make it worthwhile.
 
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Old 06-01-2016, 07:56 AM
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there is a cars and coffee happening around my area soon, its at a performance place, and they are letting people do free dyno runs! its first come first served, with limited spots, if i get to be one of the spots i will make tuns with and without the shnoozle, to see if it makes a difference! I am running a k and n filter and i know that with the snout removed, it sounds more aggressive, but not really sure it makes much of a difference!, stay tuned...

http://flacarshows.com/events/event/...f-cars-coffee/
 

Last edited by Darrenmb; 06-01-2016 at 07:58 AM.
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Old 06-01-2016, 08:15 AM
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Tony:


I can claim to be a veteran on several levels. Medals, haven't seen any!!


All:


Cold vs warm intake air is a slightly complex topic. Adding in the sound complex makes it even more so. Add in K & N style vs various paper pleat filters adds some more complexity.


And, most will accept as fact that cool air is more dense than warm air.


Oh, a lot of folks, including factory engineers build in warm air to improve drivability.


So as to provoke thought, I'll stop there.


Carl
 
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Old 06-01-2016, 08:56 AM
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Originally Posted by JagCad View Post

And, most will accept as fact that cool air is more dense than warm air.
Of course it is, nobody disagrees there. 'How much cooler' is the topic.

Originally Posted by JagCad View Post

Oh, a lot of folks, including factory engineers build in warm air to improve drivability.
True again, but that's only used during engine warm up.


Is there nobody that wants to measure some actual temperatures on their car?
 
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Old 06-01-2016, 09:06 AM
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Mikey:


One more. Warm air intake yields cleaner exhaust and better
gas mileage.


Carl
 

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