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555BCTurbo wrote:

ramathorn wrote: by doing this its essentially the same thing as the velocity stock.

A filter most certainly wouldn't get the same swirl effect that a steel or aluminum velocity stack would

i was refering to a filter like the one that is in this thread http://bbs.legacycentral.org/viewtopic.php?t=31455 its a cylinder style filter but instead of like mine where the one end is completely sealed it has it partially open with an inwards cone. on the the end of the cone there is or some have an aluminum rounded center cap.

i understand the dark spot that is on the air filter is from all of the crap that its ingesting and im not saying that ALL of the air is being forced to that one spot (obviously since its being blocked by gunk). that is the direct path that the air is coming into the air filter then its getting diverted and spread out somewhat evenly arcoss the surface of the filter. like you said the air is tumbling around and slowing down. with open element style filters though its just suck in avoid all the air box obsticals and into the maf. granted my intake filter specifically does not have a velocity stack (which by the way, i like the way you explained what it actually does) the air is being smoothed out another way. the inside of my filters bottom is smooth rubber lined and has a gradual mini grade to it if you will.

i really dont know if anyone has seen this on the rs board so i thought id bring it to your attention over here. i know this is a comparison between and ebay intake and the stock impreza setup but i cant imagine that cheapy ebay intakes are the best so there is room for improvement on this system as well. http://www.rs25.com/forums/showthread.p ... ntake+dyno

That was an interesting read. I'd be curious to see what the dyno plots were like below 4000 rpm.

Legacy777 wrote:That was an interesting read. I'd be curious to see what the dyno plots were like below 4000 rpm.

1500-2100 or so there was a minor drop in torque and then at 3500 there was a small blip. the plot show that the the torque is up though and seems to be flatter a little longer.

a possible reason for the number prior to 4k http://www.rs25.com/forums/showthread.p ... light=dyno

That's not engine rpm, that's speed in mph. Those blips are the automatic transmission shifting.

Dynoing automatic transmissions and comparing the numbers to MT's just doesn't seem worthwhile. The torque converter gives you torque multiplication, and depending on when that occurs you may get different numbers.

not realy comparing the mt, i was just using it as a refrence to see what and intake does. but since you mentioned the intakes were tested on the same car same tranny so its not comparing the tranny manipulation.

I thought I would chime in on the velocity stack issue. They do increase airflow as well as smooth the airflow. In fact that is why they flow more air because the flow is smoother. It is not just for the maf, otherwise why do they put them on all the motorcycles with no maf (carbs and throttle bodies only) and remember the mechanically injected Can-Am cars with the stacks out the top. Velocity stacks increase airflow. Airflow does not like sharp bends and a 90 degree bend at the maf would be horrible without the velocity stack. It is very close to the side of the box which I feel really hurts the flow. That is what I was working on today. Trying to get the later airbox with the 45 degree maf figured out. When I do the changeover I will remove the velocity stack from the old box and put it in the newer one which doesn't have one for some reason. I think there are a couple of rivets holding it in the older box.

Jeff

jefferson wrote:... Trying to get the later airbox with the 45 degree maf figured out. When I do the changeover I will remove the velocity stack from the old box and put it in the newer one which doesn't have one for some reason. I think there are a couple of rivets holding it in the older box.

That's what I intend as well.

I have been exploring options on how to connect the maf to the turbo inlet once I do the new airbox and it looks like it is going to take a custom made piece to fit inbetween in a workmanship manner. The two pieces will be in very close proximity along with a 35 degree bend. Then you have the height difference and the reduction in size to boot. I have scoured a couple of pic and pulls for something off some other car that might help, but as yet have not come up with anything. There is always something that puts the kabosh on it. I did find a place that makes custom rubber intake pieces that may be an option depending on price. It would sure be nice to have one piece that was smooth on the inside for flow, and then all the stock lines would hook up. I will keep things updated on that note.

Jeff

Just my comments on velocity stacks:

I had modified a VW air-cooled engine some years ago. I had read an article on velocity stacks and the fuel "fog" that "sits" up high in the stack. Without this "fog" the VW engines leaned out dangerously, said the aritcle. I experimented with the stock oil air filter, an aftermarket pleated cylindrical filter, a short velocity stack, and the 6 or 8 inch velocity (I don't recall which height it was) stack (which the article that I read highly recommended). There was absolutely no doubt that the high velocity stack contributed to more torque and hp and much smoother acceleration throughout the rpm range.

Anyway, this isn't really comparing apples with apples, but most probably, as in other design areas, a properly designed velocity stack would contribute to performance gains whether it be little or a lot.

Now to get back on topic . . .

$20 worth of 2x 3" PVC elbows (90 degrees). A saws all, and 35 min can get that cone filter in to your fender. LOL

PVC pipe is very heavy, I recommend aluminum drier vent piping. The cost is a bit less too, although the joints cannot be made air tight as easily.

But considering the crap your taking out (stock air filter, and air box), you still wind up with less weight then you started out with. And also the PVC is stronger and smother then dryer pipe.

Legacy777 wrote:That was an interesting read. I'd be curious to see what the dyno plots were like below 4000 rpm.

Josh, I looked over the dyno plots and the last one with the road speed indicates that the engine will run quite lean in first and second gears. So, even if the dyno plot shows good improvement, wouldn't the lean condition be detrimental to the engine?

You can't look at that plot and make that assumption. Those numbers are mostly around stioch, which is where they're supposed to be. Engine load increases in 3rd, which is probably why the afr dropped.

So, even if the afr goes to around 16:1 or over (22-28 mph and 38-48 mph) that's not too lean?