Cooling Options

B6/7 S4/RS4
#1

We all know that the 4.2 loves cooler air so I started thinking about what other mods there are to decrease IATs while naturally aspirated.

The JHM Intake Spacers have been shown to help keep the manifold cooler, but what other mods are available?

I’ve heard of people deleting the SAI and routing tubing to make a sort of CAI, but how does that hold up in the rain/snow? How much of a difference does it really make? Does the ben3fit decrease significantly once the intake manifold heats up?

I have mixed feelings on vents in the hood. On one hand, it’s an Audi. On the other, a ram air/hood scoop type setup straight into the intake would be pretty interesting to try (in my head at least).

Is there a sort of choke point for cooling? ie: is there no point in routing in cooler air if a hot manifold will significantly negate any cooling (as a hypothetical example). If so, what would be some other ways of cooling off this choke point?

Are there any other mods out there to decrease IATs on a NA setup?

#2

JHM experimented on the B67 S4 with a ram air setup utilising the auxillary flap on the airbox (the one that opens up at certain RPMs, that many people just delete so it’s always open) and routing down to the passenger side foglight grille.

On supercharged cars this might be tough of course, but on NA cars it’s a little better.

There’s lots of discussion regarding the flap on the airbox. Some say to leave it in place only opening at 5500 RPM. Others say to rip it out and leave it open all the time, but then some folks will say that this causes the car to take in hot air from the engine bay at low RPMs

The problem with that logic is that the air in the engine bay doesn’t get cold at 5500 RPMs, yet you allow it to open, so why not allow it to open earlier? The answer they give is 'the car is moving too slowly below 5500 RPM but once it’s over 5500 RPM, it’s moving fast enough that the engine bay air is cool.

OK…but even if it is true, that only counts in first gear. 3nd gear at 3000 RPM the car (and thus the airflow through the engine bay) is same as 1st gear at 6000 RPM so there goes that theory. To that end, perhaps we should have that open fulll time. The other side of the naysayers is ‘but Audi did it so it must be good’. Yes, and Audi also puts a throttle restriction below 5500 RPM, yet I don’t see any of you asking your aftermarket tuners to leave that in.

So, there’s that blown to shreds.

#3

Has anyone debunked or proven the flapper formally with data? If not then what is a good set of tests?

I would think the following blocks at least:

  • rpm
  • maf
  • iat
  • timing
  • timing retardation
  • speed (to easily see what gear you were in when you crunch the data)

A pull in each of the gears (probably just 1,2,3 since 4 would get pretty fast on public streets)

Both pre and post deflap

In relatively cold and warm ambient temps with the engine at regular operating temps.

What’s involved with just deflapping? I’m assuming pulling the airbox out and capping off the lines? I vaguely recall reading that this flap doesn’t have a position sensor so it shouldn’t throw a CEL.

#4

Also would be interesting to compare this between stock and tuned (how it correlates to the throttle restriction).

Also googling around a bit, it seems like its not just rpm based but speed based as well? I’ve seen 50kph thrown out there as the lower limit for when it’ll open.

#5

That would make more sense. Got a link?

#6

http://forums.audiworld.com/showthread.php?t=1611645&styleid=6

BTW the mobile theme for AW is weird. People apparently like to make their posts in the post title section (QW style?) which doesn’t appear on the mobile theme.

#7

I think you’re gonna have a hard time proving the flapper theory with quantitative data just bc of how tiny the difference will be.
After all, the flapper is only a hole about 1.5" in diameter. And the majority of the air is coming in from the top ram scoop.
It’d be fun to see, but it’s not too much to really fret over imo. I’d just say your time and energy is better spent on other things.

If you got rid of the secondary aux cooler and had a direct flow to the airbox, I think that’s where the advantage would be. But then again, JHM went through all the testing and product development for this, and at the end of the day never released a product (maybe to costly in their opinion, who know why).

#8

JHM said it didn’t make sense because expensive, cumbersome, and modest results. That was on the b67

Koolade9 did this on his rs4 but never posted any acceleration results of any kind for this or any of his other mods unfortunately. His car should be the quickest na rs4 as he has loads of great mods done and lw stuff too. Hopefully he can change gears and drive better than mick. Although roadrace guys love to say the car isn’t made for the dragstrip and virulently rebel against taking it there for some absurd reason, so we will likely never see a result from him.

#9

2000s4 also had this done on his didn’t he? (Tubing to the foglight area). I’d be curious to know how it stands up to snow and rain down there.

I guess it might be a fun cheap little project if the bumper is off anyways. I’ve been meaning to delete the sai this summer so maybe its something I could try then. I just haven’t been able to source any block off plates and I’m not that handy with metal work nor have the tools or contacts to fab them up.

So looping back to my original question, is there anything else that would help lower the iats?

#10

I removed mine when I had my airbox out. Didn’t get any codes or anything. A lot of cars have a tube that runs off it to the front of the bumper as well so the whole sucking in hot air is not different then the upper intake IMO. But as Maddog stated, its not a super large hole, likely the difference would be negligible.

#11

I just reread maddogs post and realized the secondary rad is there. So I’m assuming opening that flap below 50kph would get slow moving hot air coming out of the rad unless you pipe around it or relocated the rad.

#12

Id relocate it. It opens up a ton of room. For reference…

http://i103.photobucket.com/albums/m151/65vetteC6/D532BF12-3BA0-4A7B-B019-2DBB71443925_zpstnv1fm0y.jpg

This is the pipe I was talking about that mounts to the hole.


http://i103.photobucket.com/albums/m151/65vetteC6/S4%20part%20out/IMG_1622_zps352aa452.jpg

#13

Wow that’s a heck of a lot of room.

Could probably fit a supercharger in there :wink:

#14

You know I’ve never seen that part of the engine bay without the supercharger!

#15

That’s a B5 thread.

And audiworld used to be the biggest audi site. It was in that horrible kawf format like quattrofail currently is. When Internet Brands bought audiworld , they switched over to the normal vbulletin format 99.9% of the world prefers, and all the nerds who loved the 1990s dial up forum format whined, left, and started quattrofail.

#16

I removed the flapper on my S4. It was one of those things that everyone just did without questioning. In hind sight, it probably does cause the car to take in lots of warmer air than it needs to, and I bet the extra volume isn’t really necessary.

I WONDER. The air is coming in through the ram air when the car is moving. What if audi puts the flap there to bleed off excess positive pressure in the air box caused by the RAI affect? Do we really know what Audi’s true intentions with the flapper were? Could be some weird NVH or emissions thing.

How much timing does a JHM tune pull when the IAT gets warmer. On the Cobra, my tune pulls one degree for every ten degrees over 100 degrees. That’s charge temps, but you can see that even a ten degree difference means power must be sacrificed.

#17

Not sure; The study guide shows the arrows going into the airbox.

http://www.imgur.com/FcqB9Iu.png

#18

so we’re back to my comment above that the 5000 RPM thing makes no sense from a heat point of view, since it’s not above a certain speed, but a certain RPM.

I guess it’s where it is necessary, but my feeling is that I’d like it to be open all the time that the car is moving. When it’s idling, sure, close it. The rest of the time? Open it.

Wonder if CV does anything with it in the tune.

#19

Interesting discussion.

Is Audi trying to find a balance between cool air (flap closed) and total air (flap open)? The engine doesn’t need as much air at low RPM, so the primary (cooler) intake path is not a restriction and Audi programs the flap closed. At higher rpm, more air is needed, the primary path becomes a restriction, and Audi programs the flap open.

And the “open at road speeds higher than 200kph” is again a balance of cooler air (due to high road speed) and the engine air requirements (more air required under heavy load when floored in high gear at low rpm)?

#20

[quote=“sakimano,post:8,topic:5386”]
Back-handed as it may be, I’ll take that compliment ;D

I never actually tried just removing the flap itself, I went straight to a cold air snorkel to the front grille, I’d definitely recommend it though as one of those ‘how could it possibly hurt’ mods… It gets pretty freakin hot here in the summer, so anything I can do to keep temps down…I’ll do it.

I’m stealing this idea (charcoal can breather)…I’ve been looking for ways to remove more vac lines and crap from the back of the motor…gracias!