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Re: Filters, intakes etc
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Posted by Vigge [Email] (more from Vigge) on Sun, 25 Sep 2005 04:11:14 Share Post by Email
In Reply to: Re: Filters, intakes etc, Dean, Sat, 24 Sep 2005 22:11:51
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>The resonator and lower air box losses are about the same and one should expect these 'dynamic' >losses to be about the same. The resonator can be removed some how, but this really suggests that >the 3" duct mod would be good. It reduces two dynamic losses to one and the larger flow cross >section means less velocity and then less dynamic losses. So these losses might be reduced by >perhaps 4:1. With that reduction, the reduction of air filter losses then are more significant.

Dean, assumpiton that the losses are the same for after resonator and bottom part of the airbox speak agaist every single measuring result I have seen so far deling with this issue. I dont remeber what the diameter of the pipe is in the T7 system, but I can check it for you.

I think that the K&N filters and other such would show an advantage VS paper after the paper started to accumulate dirt and well before the exhaustion of the paper element service life.

You think? This is one of those marketing slogans feeded to us from various locations, which IMHO is far from the truth. In my test I had a 6 month old paper and a brand new free flow, still nothing. The same conclusion has also been made in various other studies...

The orientation of the 'pressure' ports in the air boxes can have a significant effect. IE one can get incorrect readings, but these would be incorrect in a similar fashion for each. "The pressure port (actually a vacuum port due to pressure loss) was attached to airbox just above the air filter." If the port opening was facing the filter, it would measure dynamic+static pressure, not static pressure.

I was surprised with the lower airbox result also and mainly due to this I also measured the drop in 90 deg angle to the original measurement point. Results where identical.

We do not know if the air filter tests
(Bob's)actually measured the pressure drops at the same air flow. We only know what the engine RPMs were. The only way to do that would be to put two air boxes in series and use a blower. The air mass flow through each would then be the same. In your tests, you do know that the air flow through the MAF and filter were the same.

Yes, I’m familiar with Bob’s measuring method, but that was just a add-on type note, since I could not see any difference in the pressure drop.

>With the small air boxes in the NG900's and OG 9-3's, with the air flows in these turbo engines, >the filters may simply be too small. And with increased HP mods, low restriction air filters may be >all the more beneficial. With the T5's there were no MAFs. So a T5 with a duct mod would be a >lot less restrictive than any T7+MAF could ever be. So the effects for the T5's may be in a >different class.

Dean, the airbox is plenty big and its surely not the first issue to deal with and with the help of a low restiction filter you wont see any results. For instance at autospeed they tested 20 or so airboxes in a flow benc with 1” prssure drop and over 100CFM was measured with the filter in place. With out the filter the resutls increased by only ~10% or so. This, among with the results I posted aerlier speak for the fact that the restriction caused by the filter in very minor compared to the total losses in the intake.

I push my stock box 250g/s and I dont see a need to do anything to the size of it.

>So perhaps the issue is air boxs and MAFs that create pressure drops. I think that too many folks >have had good results with K&N type filters to throw all of that away based on Bob's figures.

What are these results you reffer to with K&N drop in filers, are there any if the mighty old butt dyno is forgotten?


> I do think that we need to address the big picture and tackle the big problem, dynamic flow losses.
>Dynamic losses occur when flow speed change and the kinetic flow energy is lost, then the flow >needs to speed up again, as in the turbo inlet pipe. The shape of the end of the intake snorkle is >also critical and a bad design creates a pressure drop VS one that that attempts to reduce such >entrance losses.

I think this would be a good idea, but a simple study can be made as stated above with costs close to 0 dollars. Also a simple theorectic study of the losses would be interesting, which is the most dominat factor the statistic or the dynamic flow loss?

>There is a pressure drop from the air box (after filter) to the exit duct, created by the pressure drop >needed to accelerate the air from the air box large x-section to the x-section of the duct. I think >that your MAF figure probably lumps two pressure drop sources together.
>How did you implement pressure ports and how did you orient them VS the flow directions?

After MAF the nipple is in a right angle to the flow. In the airbox the nipple is in the end of the box, right angle to flow if the goes through the filter from bottom to up. More nipples can be installed, just tell me where you want it located.

>You have done some very intersting work that quantifies something that has had lots of >discussion, but no hard data.

I dont know which is the better way “assuming and posting theories” or measuring something that is “in” relation with the losses? Autospeed is has also pretty much information on this topic, so it might be worth 15E to get the articles if you want to do some reading.

>And a note that the 9-5 T7 intakes that I have seen do not have a resonator. I do not know if early >production did or not.

9-5 do not have a resonator just like you said, but the snorkle is different, so is the airbox. I will look into my friends 9-5 in near future.

>The screens on MAFs are not to keep junk out, but the screen serves as a flow straightener and it >cuts up large scale turbulance. This allows the velocitys seen in the center of the MAF to be >extrapolated to an overall flow measurement. Some folks have removed the screens on MAFs and >then created some serious problems. Not something that one can do, but there may be some MAFs >designed for performance applications where the screen losses are reduced. Flow screens are used >this way on the intakes to wind tunnels as well. These are in large cross sections and cut the flow >disturbances into small ones, then as the flow cross section reduces going towards the test section, >the small vortex structures are elongated and and these disipate rapidly.

With you on this one.


posted by 80.222.176...

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