Stock Intake Piping Pressure Drop Test & Initial Results
 

Much more to follow but I wanted to report my initial findings...

Many of us have looked at the stock turbo inlet system on these cars and surmised that they must pose some amount of restriction based on all of the bends and flattening out. I sought to quantify these losses in terms of pressure drop by building a manometer and doing testing on my own 01 TT. If you are unfamiliar with intake pressure drop testing, please read these articles first:

http://www.autospeed.com/cms/A_107824/article.html
http://www.autospeed.com/cms/A_0637/article.html
http://www.autospeed.com/cms/A_0646/article.html

onward...

My car:
01 6 speed with 36k miles
Stock K16s
Remus Exhaust
Bosch 710N DVs
0.7 Bar of boost (No flash)

I built a simple manometer to measure inches of H2O drop caused by possible restrictions in the intake system. The top of the manometer is at approx 32 inches above the initial water level (I'd use a longer stick but it won't fit in the car). I won the basket o' beer at a holiday party.

http://i49.tinypic.com/29wveqp.jpg

I tapped and mounted a fitting and some vinyl tubing just in front of the passenger turbo.

http://i48.tinypic.com/21dlv7q.jpg
http://i47.tinypic.com/xmtvtg.jpg

Test conditions:
I was limited in space and speed limit so I did 2nd gear pulls from 2500rpm to just under redline. Boost was a solid 0.7bar on the stock gauge. My wife was watching the fluid level in the vinyl tubing while I focused on the road.

1st pull: Fluid began climbing immediately as the turbos spooled and quickly jumped past the 32" of H2O mark on the manometer, through about 4 feet of coiled hose and about halfway out the passenger window towards the turbo before I realized what was happening and let off.

2nd pull: Again, straight past 32" of H2O but I let out sooner so as not to injest water into my poor K16.

To quickly summarize, this is MASSIVE pressure drop for a mostly stock, non-flashed car. I can't imagine what guys with flashes, 16g, 18gs, etc would be seeing.

The question that I will answer with my next test is: "where is this pressure drop coming from?" I will probably tap right after the MAF to see the pressure drop caused by the pancake piping alone and then go from there.

Thanks for reading & standby for updates later next week.

Great stuff. As a P-Car "newb" but long time turbo car owner, this is very interesting to me.

Looking forward to the results.

Wow really cool stuff! Can't wait for the rest of the results!

Awesome....you are quantifying what common sense has been suggesting (which is the basis of all great science).

Love the MacGyver setup! :D

subscribed - interesting

Watching this thread too.....keep the info coming.

I'm going to attempt a better baseline tomorrow -I'd rather have an actual number instead of 32+ inches. I'll try adding some length to the tube support and sticking it out the sunroof, hopefully I can stay out of prison. :)

Then I'll tap behind the MAF.

Edit: Found a Dywer 2050 vacuum gauge (reads up to 50" of water) for $30 on the bay, should make things a bit easier.

very cool stuff !

Awesome. Let see some number. Thanks for DIY exp.

Looks like a great experiment. Subscribed and Rep Point Given

I'm assuming you did expect to get some pressure drop (Vacuum) correct? The turbos are causing a vacuum that exceeds atmospheric pressure.

I think you can only really quantify this if you test several cars ranging from stock to fully modded.

Good Luck

Yes Yes Yes!!! thank you! This is what I have been wanting to know and while I think I'd have used a gauge (lol) this testing really helps prove where the bottlenecks are. I used to have a vac\pressure gauge used for engine troubleshooting - undamped and VERY sensitive it would show me all sorts of interesting things like intake pulses at idle as it jumped around. Something like that would be perfect for this kind of testing and honestly if you can find something like that, undamped would be best I think, I'd be willing to chip in to help buy it! I'm sure your wife would appreciate it too hilarious If you managed to find something that could peak\hold too that would rock! Mind you length of tubing and diameter will "soften" response but I think it's pretty clear you've found a huge bottleneck. It would also be interesting to see say a 4th gear pull where things won't happen so fast. Vac might start out high and then taper off as demand slowed after the intial hit or it might just climb and climb as airflow needs increase with RPM. Lots to ponder here, I really look forward to more data!

Oh, nice to see someone else who reads Autospeed posting here - those guys have the same mindset I do on many things - find the bottlenecks and do simple testing to get good data.

I'm serious Earl, if you PM me your PayPal information I'll shoot you some cash - you're saving me some serious hassle testing and my car is no longer stock anyway. If others did this and you shared the data it would be money well spent IMO.

Ari - he's testing a near totally stock vehicle at stock boost. Testing a more modified vehicle with the stock intake piping will simply display even worse results! His next test, up by the MAF, will help us figure out WHERE the restriction is. If he sees less pressure drop by the MAF then the kinks are the big culprits and systems like the AMS piping would help relieve it up to the power point where THEY become a restriction - and I'd love to know THAT too. If he still sees as much pressure drop up top then it might be the filter - easy enough to check with a short sprint sans filter. If he gets really crazy and tests both sides of the MAF then we'll know what restriction IT makes. This is basic engineering 101 and when you find\eliminate a bottleneck at some power level you make more power - possibly without spending big bucks. Plus since this is intake side of the turbos anything you do to allow them to breathe will increase spool\response. VERY worthwhile!

All - The tapping and fitting of the test ports is the hardest part of this, that the vendors who sell various modded intakes haven't done this sort of simple testing and posted results with their parts is a bit mind blowing. All a vendor would have to do is test the stock with the modified and show a difference in pressure drop to give a VERY good indication as to improvements. The closer to zero drop the better. Even the guys with fenderwell intakes should test this with and without a filter. If you still see a significant drop without the filter at the turbo end of the pipe then the pipe is a restriction, if you see none but see a bunch with the filter on then you need a bigger filter. This is easy stuff once you have test ports built and a meter and it's damned near FREE power as you are simply getting power and spool from the stock turbos as you imporve the breathing.

If he had tested this and seen no major vac then we'd have known that upgrading this early on was a mistake, at THAT point testing more modified cars would have made tons of sense. With a big pressure drop though I'm now wondering how much power just a set of free flowing intake pipes would pickup on even stock vehicles. Why do no vendors test this? Can you imagine sales if just swapping the intake pipes picked up say 30HP? Okay, that assumes the intake doesn't cost a grand+ but still.... :rolleyes:

Major props Earl, you deserve much rep for this testing - thank you!

P.S. Here's an interesting thought - want to bet the X50 cars have the exact same intake piping and that their pressure drop is even WORSE?

Thanks all,
BLKMGK, I'll let you know how the Dwyer gauge works out -its not a peak and hold, but I'll try and video tape it for the time being. Will trim the piping down (probably 8ft instead of 20) and do some longer pulls as well. I'll keep drilling if I don't see a significant delta post-MAF and pre-turbo. Honestly I didn't expect to see what happened -thought it would jump up to 20 or so.

Ari,
An completely unrestricted turbo should show near 0 on the gauge, though its reasonable to expect some pressure drop with a MAF and airbox. Agree that testing a variety of setups would be beneficial. I hope to do tests with a flash and then with modded intake piping. It seems that the common wisdom suggests that the intake system isn't a restriction on mostly stock or flashed cars. While I can't promise massive increases in horsepower or huge bang for the buck by eliminating whatever these restrictions are, it should allow for better response in terms of spool and boost threshold as well as keeping the turbos in the higher parts of their efficiency islands for a bit longer as boost is raised.

IMO there will always be a vacuum in the air intake. If it was 0, then there would be no reason for the air to go into the intake cause it would be same at atmospheric pressure.

So for air to even want to enter the intake, there has to be some sort of vacuum. I think the big deal for this test will see how different intakes size up near the turbo. I think it would be obvious to say that a larger intake and piping would result in less static vacuum than a smaller diameter system.

And the bends and crimps on the piping would also make the air travel more and not in a straight line and should also produce more vacuum.

Anyway, can't wait to see some apple to apples results. I would also think that this could be done on a test bench instead of installed on a car to produce more clinical numbers. Such as hooking up the stock pipes and intake, etc. to a shop vac on the turbo end and then switching out the pipes to an aftermarket version and repeating the test. Then switching out the intake plenum, etc.

Having it on a vehicle would produce many more variables than on a test bench, IMO.

Anyway, just my $0.02, but I think any information at this time is better than nothing!

Remember this is a static differential pressure measurement (referenced to atmospheric), if you go WOT on an NA motor and watch a vac gauge, it will move towards zero (ideally) as the throttle plate is open even though mass flow (and dynamic pressure) has changed considerably. Same concept pre-turbo. Just as positive static boost pressure is a measurement of restriction post-turbo, negative static pressure is a measurement of the restriction pre-turbo.

..at least thats the way I understand it, maybe I'm missing something as I would expect a little static drop right in front of the compressor blades from the flow accelerationhilarious

Decent article on it here: http://www.avweb.com/news/pelican/182081-1.html

Edit: Completely agree on the flowbench for more controlled conditions but I figured this would give at least a relative ballpark as to what's going on. That, and its hard to replicate turbo mass flow amounts on the cheap!