VAP

for the past week or so I've been running the new, longer, one-piece FlowTube and scratching my head as to "how/why?"

I've been swapping between S3/RS3 MAFs and one glaring fact has surfaced. No matter which MAF I use I get a CEL with "any/every" o-ring, yet zero CEL's with no o-ring.

In years of previous testing the S3 MAF always preferred an o-ring to running open sensor orifice. The RS3 MAF has always been less sensitive, ie; it would tolerate an o-ring or it was happy without and there was no other indication performance-wise if it even cared.

With the FlowTube and "any" o-ring in place both MAF's throw almost-immediate CEL's within a mile. I've tried every o-ring that'll fit and that I experimented with initially in finding the o-ring cure for lean conditions when using the S3MAF. All to no avail. Every damn one of em throws CEL's when FlowTube is installed! Given this I'm now leaning towards "velocity" as the primary contributor to this development. That while flow is important the car seems to respond more favorably to enhanced velocity than simply flow or volume. If thats the case then experimenting with a slightly smaller inside diameter flow tubes "may" yield even more favorable results. If that holds true then the goal becomes a "tuned" 12V specific intake tract. From there it's just a matter of what is the ideal length and diameter. In a given ID is shorter better than longer or is MAF-to-TB the best way to go? There could be "street" flowtubes or track flowtubes, low, mid or high rpm flowtubes, high mileage flowtubes for long trips or... infinate possibilities with "quick-change" 30-second swaps using lever clamps.

Multi-Meter shows MAF voltage spikes to dead rich at anything beyond off-idle w/FlowTube and "any" size o-ring in place. This translates to a definate increase in airflow with FlowTube further confirming what the flow bench already demonstrated. And allows for good/appropriate sensor readings without resorting to things like o-rings which dupe the sensor into thinking it's getting more air than it is by reducing orifice diameter which causes air to travel past the 2 sensor wires faster than it would with the stock 10mm orifice.

But I'm no closer to understanding how/why any of this is making the car so much faster/more responsive. The result is far greater than sheer CFM increase alone can allow for or even begin accomplish. And about all I've learned in the past week is that MAF o-rings are about to go the way of the dinosaur.

I'll keep at it...

450exc115

Mance, with all the flow meters we use at work the general rule of thumb is 10 diameters infront of the meter and at least 2 diameters behind.. This allows nice laminar flow through the meter to get an acurate measurement. Those MAFs are roughtly 3" diameter so that would mean I would need 30" in front and 6" behind to get an acurate flow measurement. Since we don't have room for a 30" inlet the VS is a great way to smooth things out (we did this all the time for testing jet engines) in a short distance. SO maybe the added length and size behind the MAF helped the reading become more acurate.. Just thinking out loud.
Tom

VAP

The aluminum sleeve ID has been honed in a micron finish and pattern that I've found most beneficial over the years and is carried out in every "hard" component from the airbox velocity stack intlet, airbox velocity stack outlet, S3/RS3MAF, velocity stack hose joiners, high velocity recovery sleeve and XTB's.

There's been about a 20*F temp drop with the FlowTube installed in the silicone tubing and about a 12% increase in flow. But the car has just suddenly come alive power-wise far in excess of the slight increase in flow or any 20 degree temp drop. And the "only" piece added was the internal aluminum sleeve. Everything else has been on the car for over a year.

Makes me want to risk testing a 2.75" intake system just to see if our cars have some innate affinity for high velocity over volume. Something I contemplated years ago when doing the 3" tubing but was stymied by clearance issues between TB and firewall. I don't have a clue how to transition from a 3.25" throttle body flange to a 2.75" 90 degree elbow within a 3" length in metal, "off-the-shelf" silicone or any other medium.

May be time to take up learning how to make & wrap my own silicone elbows.

450exc115

You know what they say, for every degree of temp drop in the intake is almost 1hp gain.. 20degrees is a big drop IMO.

From in the increase in flow it also sounds like the wall surface friction is way down, which I would expect coming from a soft silicone tube to a hard (relative to silicone) smooth Alum tube.

One thing I always question is while you can have high flow parts, is the velocity of the air charge sized properly to the phyisical volume change in the engine.. Meaning to big is bad and so is to small.. I don't know these numbers but I know there is a general rule of thumb in the auto industry based on advancements made in the last 10-20 years (the covette motor is a good example).

Tom

VAP

vastly more ID's/ODs than aluminum. It's also thicker-walled tubing than aluminum and could drop intake temps significantly further. The primary goal is to make "quick-change" velocity tubes for testing (maybe "flowtubes" was a tad rushed when conceiving a moniker).

But if I have half a dozen inside diameters between 2.5" & 3" ID's (with 3" end caps) of "quick-change" velocity tubes with lever clamps to mount between MAF outlet and first elbow I should be able to nail down "if" this is the magic pill and what is the ideal diameter for a given effect, ie; street, race, high end, low end, increased MPG, etc. And also be able to reduce intake temps further. Then experiment with "slit-walled" roll cage foam tubing to further reduce intake temps. Wouldn't kill me to keep intake temps near 65-70*F in virtually any ambient temp situation.

Smaller diameter wont break my heart when dealing with that pesky friggin ISV harness either!! ;-)

450exc115

Once you nail it down you could always do a double wall tube that was evacuated under vacuum.. More space required but least thermal conductivity..

grnaudi96

If it swallowed your o-ring, why where you stupid enough to put it on the TB side you idiot?!

VAP

thats why they're called o-rings and not ball bearings. Eat as many as ya like... they'll make more!

His account & posts will be history again shortly

grnaudi96

Good... I'm getting sick of him. Good luck with your flowtube, quite a complicated project!

JWG

As I have commented in modern parlance previously, "wicked"!