Pressure Testing (Long Post)
#21
09-17-2010, 09:05 AM
^ ditto...
i was surprised by the rear bumper findings as well...
i'm still hoping to get a magnehelic gauge that can read 20-30" of water so i can distinctively test the drop in pressure with mods... we'll see
i was surprised by the rear bumper findings as well...
i'm still hoping to get a magnehelic gauge that can read 20-30" of water so i can distinctively test the drop in pressure with mods... we'll see
#22
09-17-2010, 05:08 PM
Well, I might have some access to some "scrap" aircraft grade sheets of aluminum. All I would have to do is really measure out the entire area beneath the rear and start cutting. I need to get a jigsaw soon!
My next question would be about that wonderful little triangle jacking brace in the rear of the GD3. It looks quite stout and heavy, have any thoughts on it's removal?
My next question would be about that wonderful little triangle jacking brace in the rear of the GD3. It looks quite stout and heavy, have any thoughts on it's removal?
#23
09-17-2010, 07:33 PM
you could... i like having a central jacking point for the rear...
if it's welded on (not sure) you'd have to chisel it off... i don't think you're going to find much weight savings there however...
if you're going to do a diffuser, you can just cut an opening for the tow/jack point to come through... it won't affect the dynamics that much...
if it's welded on (not sure) you'd have to chisel it off... i don't think you're going to find much weight savings there however...
if you're going to do a diffuser, you can just cut an opening for the tow/jack point to come through... it won't affect the dynamics that much...
#24
11-11-2010, 01:20 PM
Nice to see another fan of the Autospeed site, and their interesting work eliminating "negative boost." Inspired by their results, I've acquired some magnahelic gauges as well.
Interested in the entire intake tract, I measured negative pressure at the throttle body with the stock intake, and with a flared piece of 2.5" stainless tube (basically a velocity stack). Not surprisingly, the intake showed far more negative pressure (restriction) than the velocity stack did. What was surprising was that if I removed the bottom half of the stock intake, I also removed most of the restriction. So, my plan at present is to duct from the existing duct in the lower driver's side corner and replace the lower half of the airbox. If I ever get to it, I'll post results.
Thanks for your interesting posts! For folks in the know, data actually matters.
Bman
Interested in the entire intake tract, I measured negative pressure at the throttle body with the stock intake, and with a flared piece of 2.5" stainless tube (basically a velocity stack). Not surprisingly, the intake showed far more negative pressure (restriction) than the velocity stack did. What was surprising was that if I removed the bottom half of the stock intake, I also removed most of the restriction. So, my plan at present is to duct from the existing duct in the lower driver's side corner and replace the lower half of the airbox. If I ever get to it, I'll post results.
Thanks for your interesting posts! For folks in the know, data actually matters.
Bman
#25
11-11-2010, 01:44 PM
Join Date: Sep 2010
Location: Chicago, Illinois
Posts: 4,424
So, while I am looking for the data and associated math that I took on my car here is a post from a private tuning forum:
Here's another explaining the same thing:
So basically smooth transitions and as few bends as possible. If you have to bend, bigger radius is better.
If you have a 2" throttle body and 2" MAF/MAS you want 2" piping. Bigger is not always better, except for the air filters you stick on the end of the 2" pipe that should be as large as is feasible to increase surface area, and decrease intake vacuum but maintain steady, high velocity laminar flow through the pipe.
Logged through an AEM 3.5 bar map sensor, at 6000rpm and around 32psi of boost I am seeing around a 0.37-0.59psi pressure drop (varies due to slight voltage fluctuations). Pressure drop should be pretty linear with rpm as long as boost is kept constant and IAT doesnt increase too much, so you can imagine around 0.55-0.85psi of total pressure drop for that same 32psi at 8500-9000rpm. My air filter is a 9" length by 6" diameter unit on a custom 4" CAI intake that I made. 0.85psi would be a decent amount considering that I'm starting at only 13.7psia here in the mountains, but ultimately it is a PR difference of around .23 for my scenario.
http://www.ncdsm.com/16g-95gsx/Intak...e%20Coated.JPG
http://www.ncdsm.com/16g-95gsx/Engin...ft%20Angle.JPG
I would tend to say that this would be a pretty good representation of what some of the better CAI systems out there as it has about the equivalent bends, 4" diameter, and a pretty new K&N filter. If it were possible to entirely reduce that pressure drop down to 0, then I could see a decent power increase as this PR difference is about the equivalent of running 2-3psi more boost assuming IAT was kept constant. In reality it is impossible to reduce pressure drop to 0, and I would just consider this a part of the downsides that come with running an intake pipe at all. Realizing that I am located 2000ft asl, giving me an automatic 1psi ambient pressure loss, I lose more efficiency just to the fact of me being in the mountains than I do as a total dynamic loss through the intake pipe. When coupled together though you could easily see where being at sea level with no restriction at all into the compressor would net some pretty solid gains.
http://www.ncdsm.com/16g-95gsx/Intak...e%20Coated.JPG
http://www.ncdsm.com/16g-95gsx/Engin...ft%20Angle.JPG
I would tend to say that this would be a pretty good representation of what some of the better CAI systems out there as it has about the equivalent bends, 4" diameter, and a pretty new K&N filter. If it were possible to entirely reduce that pressure drop down to 0, then I could see a decent power increase as this PR difference is about the equivalent of running 2-3psi more boost assuming IAT was kept constant. In reality it is impossible to reduce pressure drop to 0, and I would just consider this a part of the downsides that come with running an intake pipe at all. Realizing that I am located 2000ft asl, giving me an automatic 1psi ambient pressure loss, I lose more efficiency just to the fact of me being in the mountains than I do as a total dynamic loss through the intake pipe. When coupled together though you could easily see where being at sea level with no restriction at all into the compressor would net some pretty solid gains.
I did a little pressure drop experiment. I run a very large new K&N cone filter (9.5" long & 6.6" dia) on a 2g turbo eclipse. This air filter has a flat area of about 168 sq inches, enough flow for 970 cfm or 650 h.p. I basically run a big K&N airfilter, HKS VPC, NO MAF, and a big 4" aluminum pipe tapering into a RRE 2.25" turbo inlet pipe. I used a Magnehelic Pressure Differential Gauge (0-100 inches of water) to measure the air filter pressure drop, ultra accurate. Measured at the little nipple right on the rubber MAF inlet hose. I figure my pressure drop should be next to nothing. My car was run on 20 psi and maybe kicking out 360 crank h.p., according to DSMLINK.
I was expecting maybe 4-6" of water pressure drop thru the huge K&N airfilter which is 1 week old. Boy was I in for a surprise. Light cruise there is no pressure drop, under WOT there is minimal until 4000 rpm then it hits 10" pressure drop. Max pressure drop is at 5000-7000 rpm at 24" of water on 20 psi boost pressure on a 45*F night. For you guys that don't know, 29" of water equals 1 psi.
This goes against every thing I've read, that the air filter has little to no pressure drop. I say bullshit. I'm thinking of running a 14" long cone filter instead. Basically I have .82 psi of pressure drop just thru the airfilter. After the pressure ratio rise in the turbo compressor this would be almost 2 psi lost after the turbo. You cannot go too big on an airfilter.
I was expecting maybe 4-6" of water pressure drop thru the huge K&N airfilter which is 1 week old. Boy was I in for a surprise. Light cruise there is no pressure drop, under WOT there is minimal until 4000 rpm then it hits 10" pressure drop. Max pressure drop is at 5000-7000 rpm at 24" of water on 20 psi boost pressure on a 45*F night. For you guys that don't know, 29" of water equals 1 psi.
This goes against every thing I've read, that the air filter has little to no pressure drop. I say bullshit. I'm thinking of running a 14" long cone filter instead. Basically I have .82 psi of pressure drop just thru the airfilter. After the pressure ratio rise in the turbo compressor this would be almost 2 psi lost after the turbo. You cannot go too big on an airfilter.
If you have a 2" throttle body and 2" MAF/MAS you want 2" piping. Bigger is not always better, except for the air filters you stick on the end of the 2" pipe that should be as large as is feasible to increase surface area, and decrease intake vacuum but maintain steady, high velocity laminar flow through the pipe.
Last edited by DiamondStarMonsters; 11-11-2010 at 01:54 PM.
#26
11-11-2010, 02:05 PM
Join Date: Sep 2010
Location: Chicago, Illinois
Posts: 4,424
For more test data on flow, pressure etc. Check this out:
SDS EM-4: Aircraft
Here is a guy who took a turbocharged subaru power plant and put it in an aircraft, and has more data in his few pages than this entire forum.
SDS EM-4: Aircraft
Here is a guy who took a turbocharged subaru power plant and put it in an aircraft, and has more data in his few pages than this entire forum.
#27
11-11-2010, 06:16 PM
Join Date: Sep 2010
Location: Chicago, Illinois
Posts: 4,424
If you can find one, get a mercury filled gauge, on the face of it, it will look like lower resolution, but I find the added inertia from the mercury makes it read out more accurately. The blue-water ones seem to fluctuate too much, at least IMHO.
#28
11-11-2010, 06:27 PM
Currently, I'm getting some coroplast from the left over campaign signs from the election to mock up some lower triangular pieces for the rear of the Fit.
People look at me weird when i pick up the signs laughing hysterically...hehe
#29
11-12-2010, 02:08 AM
Join Date: Sep 2010
Location: Chicago, Illinois
Posts: 4,424
So what you are trying to say there still might be a chance that a rear diffuser would net some aero gains? I'm just gathering materials first before I even start cutting everything to mock up anything in metal.
Currently, I'm getting some coroplast from the left over campaign signs from the election to mock up some lower triangular pieces for the rear of the Fit.
People look at me weird when i pick up the signs laughing hysterically...hehe
Currently, I'm getting some coroplast from the left over campaign signs from the election to mock up some lower triangular pieces for the rear of the Fit.
People look at me weird when i pick up the signs laughing hysterically...hehe
Well there's theory and there's practice, and only one really matters in the end.
It might be worth while for the population that would use it as a function item! And if it looks good to boot, you've got that going for you.
#30
11-12-2010, 12:21 PM
Nice to see another fan of the Autospeed site, and their interesting work eliminating "negative boost." Inspired by their results, I've acquired some magnahelic gauges as well.
Interested in the entire intake tract, I measured negative pressure at the throttle body with the stock intake, and with a flared piece of 2.5" stainless tube (basically a velocity stack). Not surprisingly, the intake showed far more negative pressure (restriction) than the velocity stack did. What was surprising was that if I removed the bottom half of the stock intake, I also removed most of the restriction. So, my plan at present is to duct from the existing duct in the lower driver's side corner and replace the lower half of the airbox. If I ever get to it, I'll post results.
Thanks for your interesting posts! For folks in the know, data actually matters.
Bman
Interested in the entire intake tract, I measured negative pressure at the throttle body with the stock intake, and with a flared piece of 2.5" stainless tube (basically a velocity stack). Not surprisingly, the intake showed far more negative pressure (restriction) than the velocity stack did. What was surprising was that if I removed the bottom half of the stock intake, I also removed most of the restriction. So, my plan at present is to duct from the existing duct in the lower driver's side corner and replace the lower half of the airbox. If I ever get to it, I'll post results.
Thanks for your interesting posts! For folks in the know, data actually matters.
Bman
i only got a sensitive gauge to test aerodynamics, and never got around to getting a wider range to test the intake system... just from seat of the pants the 2.5" 90* pipe i did from the airbox to tb made a huge difference... good to know there's more to be done!
#31
11-12-2010, 12:57 PM
good info...
i only got a sensitive gauge to test aerodynamics, and never got around to getting a wider range to test the intake system... just from seat of the pants the 2.5" 90* pipe i did from the airbox to tb made a huge difference... good to know there's more to be done!
i only got a sensitive gauge to test aerodynamics, and never got around to getting a wider range to test the intake system... just from seat of the pants the 2.5" 90* pipe i did from the airbox to tb made a huge difference... good to know there's more to be done!
Any updates for the front section of the bumper where the best place to route some tubing to "guide" the air into the airbox? Sorta like a ram air effect thing.
#32
11-13-2010, 11:08 AM
the only place i didn't test from is the fog light...
but so far from what i've seen, the upper grille area is going to be the best place so far... the most pressure is seen there...
no pics... i usually have my hands full trying to drive and look at the gauge at the same time and not hitting anything in the process...
but so far from what i've seen, the upper grille area is going to be the best place so far... the most pressure is seen there...
no pics... i usually have my hands full trying to drive and look at the gauge at the same time and not hitting anything in the process...
#33
11-15-2010, 08:10 AM
I dug up the readings I took on my then-new Fit in late 2008:
Intake in front of the throttle plate:
-0.10” during hill descent
-0.35 – 0.55” during 65-70 mph cruise
-8.0” during WOT in 3rd at 6k rpm
-8.5” during WOT in 2nd at rev limiter (going up a hill)
-3.5” with the air filter removed and lid propped open (so lid and elbow) (also at WOT, under load)
Restriction at maximum air consumption (WOT and redline) is -3.5” with a 2.25” flared “velocity stack” attached directly to the throttle body
This suggests to me that the greatest gains are to be had before the air filter on the stock intake system. If the restriction of the airbox lid / elbow is the same as a flared "velocity stack," then I don't see much to be gained here. It would be interesting to see what numbers folks saw at the throttle body at WOT / redline with an aftermarket intake.
Bman
Intake in front of the throttle plate:
-0.10” during hill descent
-0.35 – 0.55” during 65-70 mph cruise
-8.0” during WOT in 3rd at 6k rpm
-8.5” during WOT in 2nd at rev limiter (going up a hill)
-3.5” with the air filter removed and lid propped open (so lid and elbow) (also at WOT, under load)
Restriction at maximum air consumption (WOT and redline) is -3.5” with a 2.25” flared “velocity stack” attached directly to the throttle body
This suggests to me that the greatest gains are to be had before the air filter on the stock intake system. If the restriction of the airbox lid / elbow is the same as a flared "velocity stack," then I don't see much to be gained here. It would be interesting to see what numbers folks saw at the throttle body at WOT / redline with an aftermarket intake.
Bman
#34
11-16-2010, 12:17 PM
^ good info...
it would be interesting to see what gains/losses could be seen post tb between the stock tb, and a larger aftermarket tb...
those numbers also still make me think that if we pick up air in a higher pressure area it'll further help efficiency...
it would be interesting to see what gains/losses could be seen post tb between the stock tb, and a larger aftermarket tb...
those numbers also still make me think that if we pick up air in a higher pressure area it'll further help efficiency...
#38
05-20-2013, 12:26 PM
Ancient I know... but,Whoa... How did I miss this thread?!
I actually just completed a "fog light delete"... And have an AEM CAI that runs down to the inside of the drivers fender...
I kept the plastic outer housings on as they looked as if they would duct in air... Wonder where I could borrow a gauge...
I actually just completed a "fog light delete"... And have an AEM CAI that runs down to the inside of the drivers fender...
I kept the plastic outer housings on as they looked as if they would duct in air... Wonder where I could borrow a gauge...
#39
05-21-2013, 08:10 PM
If you were closer to me I'd let you borrow mine...
This is ideal, but the molding is beyond what am capable of/hav patience for:
https://www.fitfreak.net/forums/fit-...tml#post995871
This is what I have created so far:
This is ideal, but the molding is beyond what am capable of/hav patience for:
https://www.fitfreak.net/forums/fit-...tml#post995871
This is what I have created so far:
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