Pointers to interesting new airbox mod.
08-16-2005, 08:41 AM
#1
Rennlist Member
Thread Starter
Pointers to interesting new airbox mod.
I'm posting this just in case there are participants here who don't frequent the other principal 968 discussion forums.
Bob Larson and David Greimann have developed and documented a simple, inexpensive modification which greatly increases incoming airflow to our cars' engines, resulting in substantial increases in HP and torque.
The mod is detailed in the current issue of 9Magazine, available in .pdf form at nominal cost here:
9Magazine Home Page
Discussions concerning the mod:
@ 968.forums.com
...with more here
and at...
@968.net
It's clear this works, and works very well. No one has posted to challenge the modification's efficacy or safety. So: just in case you missed this, it's well worth checking out.
Bob Larson and David Greimann have developed and documented a simple, inexpensive modification which greatly increases incoming airflow to our cars' engines, resulting in substantial increases in HP and torque.
The mod is detailed in the current issue of 9Magazine, available in .pdf form at nominal cost here:
9Magazine Home Page
Discussions concerning the mod:
@ 968.forums.com
...with more here
and at...
@968.net
It's clear this works, and works very well. No one has posted to challenge the modification's efficacy or safety. So: just in case you missed this, it's well worth checking out.
Last edited by John Etnier; 08-17-2005 at 05:54 PM.
08-16-2005, 02:36 PM
#3
Three Wheelin'
And if you don't want to mess around with your original air box, you can E-mail me and buy mine as a spare!
Actually, I went with another application completely, and don't use my airbox anymore.
Jason
Actually, I went with another application completely, and don't use my airbox anymore.
Jason
08-18-2005, 12:03 AM
#6
Here's my problem.
How can this modification actually result in improved engine performance? After all, if we're only talking about increased air flow, wouldn't the engineers at Stuttgart/Weissach, know how to wring any additional H.P. out of their big 3 liter and simply provide a larger air intake or scoop or some other way to force air into the engine?
Also, why just 4 holes? Couldn't a number of smaller holes (swiss cheese) have the same effect?? Why not cut out the entire front and place a screen there for maximum air flow???
Richard (aka "doubting thomas")
How can this modification actually result in improved engine performance? After all, if we're only talking about increased air flow, wouldn't the engineers at Stuttgart/Weissach, know how to wring any additional H.P. out of their big 3 liter and simply provide a larger air intake or scoop or some other way to force air into the engine?
Also, why just 4 holes? Couldn't a number of smaller holes (swiss cheese) have the same effect?? Why not cut out the entire front and place a screen there for maximum air flow???
Richard (aka "doubting thomas")
08-18-2005, 08:07 AM
#7
Rennlist Member
Thread Starter
Follow this link to purchase the downloadable issue of the magazine. It's only $2.50! Your questions will all but certainly be answered when you read the article.
There is some further discussion at the 968forums links I posted above. (IIRC correctly the thread at 968.net deals more with subscription and delivery issues concerning the magazine.)
There is some further discussion at the 968forums links I posted above. (IIRC correctly the thread at 968.net deals more with subscription and delivery issues concerning the magazine.)
Trending Topics
08-18-2005, 12:35 PM
#9
Rennlist Member
Thread Starter
So many people have either completed the mod or are about to that Dave Greimann ran out of stock on the trim rings he's been making available at his site.
The article itself provides dyno and manometer test results from before-and-after applying this modification. No one to my knowledge has bothered to duplicate this substantial effort in the week or so that has passed since the article's release.
In my personal experience I was most pleased that the modification eliminated the 'sag' which normally occurs at throttle-on befure the engine is up to speed. Off-the-line and similar acceleration is greatly improved in the street driving I do.
All feedback as to performance of the mod has been positive- again: please check the links at the top of this thread.
The article itself provides dyno and manometer test results from before-and-after applying this modification. No one to my knowledge has bothered to duplicate this substantial effort in the week or so that has passed since the article's release.
In my personal experience I was most pleased that the modification eliminated the 'sag' which normally occurs at throttle-on befure the engine is up to speed. Off-the-line and similar acceleration is greatly improved in the street driving I do.
All feedback as to performance of the mod has been positive- again: please check the links at the top of this thread.
08-19-2005, 03:22 PM
#11
Advanced
Join Date: Apr 2005
Posts: 91
Likes: 0
Received 0 Likes
on
0 Posts
I've done it and weather it's any "faster," I think it is. It revs smoother and quicker through the whole range. Throttle response is better, and the sound is a plus as well.
Just my 3 cents worth
Just my 3 cents worth
08-19-2005, 04:14 PM
#12
Three Wheelin'
Richard,
After reading the article in hopes of obtaining additional facts I asked similar questions on 968forums but Flash became angry and responded to my questions negatively. After a few hours all of Flashes negative posts and my additional questions were removed by the moderators.
This is my understanding of the modification. Dave Greimann purchased a "manometer" last year to test for loss of air flow in the 968 intake. He found that four holes of around 2 inches in diameter and spaced as described in the article created a sufficient opening to remove all restriction created by the airbox. The feeling is that this "0 loss" airbox modification produces as much power as can be gained at the airbox. They did test and did not find any benefit of using larger diameter holes. Dave is open to the idea that other designs such as your many small holes could be just as efficient.
The article contains dyno charts showing the airbox did produce horsepower and torque gains on a otherwise stock 968 on a dyno in California. I have not been able to learn whether the quoted stats are measured at the wheels or approximated for BHP. I have asked but have not had a numerical answer as to how much power increase occurs using both the intake modification and a chip but did learn less is gained than the sum of using them individually.
After reading the article in hopes of obtaining additional facts I asked similar questions on 968forums but Flash became angry and responded to my questions negatively. After a few hours all of Flashes negative posts and my additional questions were removed by the moderators.
This is my understanding of the modification. Dave Greimann purchased a "manometer" last year to test for loss of air flow in the 968 intake. He found that four holes of around 2 inches in diameter and spaced as described in the article created a sufficient opening to remove all restriction created by the airbox. The feeling is that this "0 loss" airbox modification produces as much power as can be gained at the airbox. They did test and did not find any benefit of using larger diameter holes. Dave is open to the idea that other designs such as your many small holes could be just as efficient.
The article contains dyno charts showing the airbox did produce horsepower and torque gains on a otherwise stock 968 on a dyno in California. I have not been able to learn whether the quoted stats are measured at the wheels or approximated for BHP. I have asked but have not had a numerical answer as to how much power increase occurs using both the intake modification and a chip but did learn less is gained than the sum of using them individually.
08-19-2005, 04:30 PM
#13
Burning Brakes
Join Date: Aug 2003
Location: Cincinnati, OH
Posts: 889
Likes: 0
Received 0 Likes
on
0 Posts
Very interesting in how the information was deleted from the forum. I thought that the forum was a method to share information. I too have been interested in the questions that you posed Bruce, may be the engineer in me, or the enthusiest. Maybe Dave could better answer?
08-19-2005, 06:49 PM
#14
Advanced
Join Date: Dec 2003
Location: Orange County, CA
Posts: 90
Likes: 0
Received 0 Likes
on
0 Posts
Hey guys. Since the other place is down for some reason, I thought I would get my fix over here 
As far as I know the dyno chart reflects rear wheel HP on an unchipped car. Other testiing combinations were not planned.
To give an insite into the methodology of developing the mod, the first manomater readings were made with just the lid and the air filter alone. This is the theoretical best solution - the filter sucking in the free and clear. The test with just the lid and swapping in the KN filter for the paper filter showed that the KN does provide a reduction in restriction.
The next test was with a full stock box with snorkel. Then the snorkel was removed. The restriction got worse. The wide mouth snorkel improved things a little, but not much. It was becoming apparent that the lower part of the box was the problem because the readings were nowhere near what just the lid and filter gave. I had a spare box and cut some holes in the front to see if I could open things up and voila. 4 big holes in the front were equivalent flow to just the lid. My work here is done! The hole size was made purely to fit the trim rings that are commercially available for a finished look. Anything smaller than 2", however, does start to show a slightly less than optimal solution. Cone filters with a long pipe are not as good as the hole mod.
Out of curiosity I wondered what the lower part of the box was equivalent to in terms of "filter blinding" Back to the configuation with just the lid and filter, I took a piece of newspaper and "blinded" 75% of the filter area. That gave me the manometer number that I got with the stock box and snorkel. Only 25% of the filter is used in the stock box. Look a yours, you will see a black stripe from the snorkel to the MAF inlet. The rest of the filter is clean.
The temperature of the air charge was also measured and found to be not to be an issue when the vehicle is in motion.
Hope that helps clear things up.
As far as I know the dyno chart reflects rear wheel HP on an unchipped car. Other testiing combinations were not planned.
To give an insite into the methodology of developing the mod, the first manomater readings were made with just the lid and the air filter alone. This is the theoretical best solution - the filter sucking in the free and clear. The test with just the lid and swapping in the KN filter for the paper filter showed that the KN does provide a reduction in restriction.
The next test was with a full stock box with snorkel. Then the snorkel was removed. The restriction got worse. The wide mouth snorkel improved things a little, but not much. It was becoming apparent that the lower part of the box was the problem because the readings were nowhere near what just the lid and filter gave. I had a spare box and cut some holes in the front to see if I could open things up and voila. 4 big holes in the front were equivalent flow to just the lid. My work here is done! The hole size was made purely to fit the trim rings that are commercially available for a finished look. Anything smaller than 2", however, does start to show a slightly less than optimal solution. Cone filters with a long pipe are not as good as the hole mod.
Out of curiosity I wondered what the lower part of the box was equivalent to in terms of "filter blinding" Back to the configuation with just the lid and filter, I took a piece of newspaper and "blinded" 75% of the filter area. That gave me the manometer number that I got with the stock box and snorkel. Only 25% of the filter is used in the stock box. Look a yours, you will see a black stripe from the snorkel to the MAF inlet. The rest of the filter is clean.
The temperature of the air charge was also measured and found to be not to be an issue when the vehicle is in motion.
Hope that helps clear things up.