When Testing an Intake, Why are People Dynoing with the Hood Open?

Mr. 5 · 07-25-2009, 05:27 PM

This has always made me wonder.
Of course, if there is a filter or 2 filters just sitting in the engine compartment, then of course the intake is going to show more gains if a fan is blowing air on the intake while dynoing.
Better yet, you might as well get some dry ice and put it by the filters so the numbers will get even higher!

It doesn't matter if the hood is open or shut with the stock air box because the engine isn't going to get any more air by the hood being open.

So, I have a word of advice for people that really want to prove if an intake works.
Dyno with the hood closed 3 times with the stock intake.
Then dyno with the hood closed 3 times with the aftermarket intake.
Or, vice versa. I don't care which is done first just as long as there is enough cool down between the switch over.

If i see an increase with the DCIs or other intakes by using the above methods, then I will be sold.
Becuase, I don't know about you guys, but I drive around with my hood closed. Don't you?

Kroy · 07-25-2009, 05:40 PM

+1

oddjob2021 · 07-25-2009, 05:44 PM

i will be testing a prototype closed box system soon mr. 5. i'll post a review for the members here as well. i'll also dyno above like you said however being a "closed system" like stock, i doubt anything will change.

sleepdoc · 07-25-2009, 05:45 PM

+2. I think the Intake made my 335 slower.

OpenFlash · 07-25-2009, 05:49 PM

On the road at say 50mph, underhood temps aren't much higher than ambient. On a stationary dyno, with tiny fans, and no low pressure zone under the car, underhood temps are sky high (over 200f with hood closed). That's we they are better left open. And even with a fan blowing hot stagnant air off the top of the engine. It's just closer to real world conditions. If you are testing with a massive windtunnel fan, that's another story.

Shiv

Zeph · 07-25-2009, 05:51 PM

it is hard to do... I tried it once with hood closed and the SSTT went into overtemp bypass before the 1st pull was done. You really have to have a 140 mph wind-tunnel to do it with the hood closed to simulate real road conditions. It was about 95 and high humidity that day also. I do agree if you are doing open element filter/s intakes with the hood open it is not going to be accurate.

JayKay335i · 07-25-2009, 05:54 PM

Even with a fan blowing into the engine compartment I think you'd be pushing more, cooler air through the engine compartment at 65mph than a fans going to blow.

Mr. 5 · 07-25-2009, 06:10 PM

Quote:

Originally Posted by shiv@vishnu

On the road at say 50mph, underhood temps aren't much higher than ambient. On a stationary dyno, with tiny fans, and no low pressure zone under the car, underhood temps are sky high (over 200f with hood closed). That's we they are better left open. And even with a fan blowing hot stagnant air off the top of the engine. It's just closer to real world conditions. If you are testing with a massive windtunnel fan, that's another story.

Shiv

It would be nice to see the results with hood closed.
Some dyno shops have 70 mph fans.
Also, most people are stop and go driving and doing less than 50 most of the time.

Quote:

Originally Posted by JayKay335i

Even with a fan blowing into the engine compartment I think you'd be pushing more, cooler air through the engine compartment at 65mph than a fans going to blow.

Same as I said above.
Let's say that's true, then going to the drag strip is going to hurt performance when launching?
what about going to the track? I'll guarantee that the under hood temps are much much hotter than ambient.

roozie2001 · 07-25-2009, 06:32 PM

Quote:

Originally Posted by Mr. 5

It would be nice to see the results with hood closed.
Some dyno shops have 70 mph fans.
Also, most people are stop and go driving and doing less than 50 most of the time.

i agree with you as far as the 70mph would probably do a good job simulating a car at say 45-50mph or less. (even though its a 70mph fan). And with a closed
hood test it would be a great starting point to say low range pull. But to really see the full effects u either need a wind tunnel simulator or 3 high power fans. Cuz i think the intake would only be beneficial above 100mph over the stock one. Thats why u dont see any difference in drag times of cars with or without DCI or CAI

Blk07335i · 07-25-2009, 07:14 PM

Quote:

Originally Posted by Mr. 5

It would be nice to see the results with hood closed.
Some dyno shops have 70 mph fans.
Also, most people are stop and go driving and doing less than 50 most of the time.

Same as I said above.
Let's say that's true, then going to the drag strip is going to hurt performance when launching?
what about going to the track? I'll guarantee that the under hood temps are much much hotter than ambient.

Which intake are you running these days? Are you still on the OEM box?

Mr. 5 · 07-25-2009, 07:17 PM

Quote:

Originally Posted by Blk07335i

Which intake are you running these days? Are you still on the OEM box?

Still OEM. I'm currently testing out the AFE drop in with some other things.

Blk07335i · 07-25-2009, 07:21 PM

Quote:

Originally Posted by Mr. 5

Still OEM. I'm currently testing out the AFE drop in.

I'm running the DCIs but I can't decide whether they add that much although I do like to hear the suction. Very cool. BTW, I switched over to the JB3 about two weeks ago.

Mr. 5 · 07-25-2009, 08:39 PM

Quote:

Originally Posted by Blk07335i

I'm running the DCIs but I can't decide whether they add that much although I do like to hear the suction. Very cool. BTW, I switched over to the JB3 about two weeks ago.

Now that's another story.
If someone likes an intake because of the sound then great, but I'm still not convinced that they add that much power (if any).

335iheLLraiseR · 07-26-2009, 12:21 AM

Quote:

Originally Posted by Mr. 5

Now that's another story.
If someone likes an intake because of the sound then great, but I'm still not convinced that they add that much power (if any).

think it depends on how much power you are running. at some point that airbox has to choke the engine.

808AWD325xi · 07-26-2009, 01:12 AM

Quote:

Originally Posted by Mr. 5

Now that's another story.
If someone likes an intake because of the sound then great, but I'm still not convinced that they add that much power (if any).

I didn't get any gains from an intake with a stock tune. Both dynos were done with the hood open.

Run 004 is my baseline, 100% stock.
7/18/2009 1:20:42 PM Run Type: RO Run Conditions: 86.41 F, 30.26 in-Hg, Humidity: 30%, STD: 1.01

Run 008 is with a BMS DCI and a Stett Performance charge pipe w/Tial BOV.
7/19/2009 4:20:12 PM Run Type: RO Run Conditions: 86.28 F, 30.27 in-Hg, Humidity: 32%, STD: 1.01

SoCali E36 · 07-26-2009, 04:08 AM

Quote:

Originally Posted by 808AWD325xi

I didn't get any gains from an intake with a stock tune. Both dynos were done with the hood open.

Run 004 is my baseline, 100% stock.
7/18/2009 1:20:42 PM Run Type: RO Run Conditions: 86.41 F, 30.26 in-Hg, Humidity: 30%, STD: 1.01

Run 008 is with a BMS DCI and a Stett Performance charge pipe w/Tial BOV.
7/19/2009 4:20:12 PM Run Type: RO Run Conditions: 86.28 F, 30.27 in-Hg, Humidity: 32%, STD: 1.01

so what you are saying is that it is better off staying with the stock box?

808AWD325xi · 07-26-2009, 04:49 AM

Quote:

Originally Posted by SoCali E90

so what you are saying is that it is better off staying with the stock box?

At least at stock boost levels, the factory air box appears adequate, YMMV.

Immediately after installing the intake/charge pipe/BOV, without adaptation, it appeared that throttle response had been greatly improved. I attribute that to the intake.

mwahlert · 07-26-2009, 09:43 AM

maybe a better test of performance gains/losses would be timed 20-50mph or similar runs... 50-80mph even.

uberschnell · 07-26-2009, 09:53 AM

I got mine for the looks alone..but sound is nice.

Mr. 5 · 07-26-2009, 10:13 AM

Quote:

Originally Posted by Railgun

Personally, I wouldn't want a dyno run with the hood closed unless it's the very first run and the car JUST got up to op temp.

I don't care if the hood is open between the runs to let it cool off.
I just want to see runs with the hood closed.

roozie2001 · 07-26-2009, 11:04 AM

Quote:

Originally Posted by SoCali E90

so what you are saying is that it is better off staying with the stock box?

Until way more power and bigger turbos I think it is adequate. But what do I know. My car feels fast as can be with just a drop in. It never feels like its being choked and I'm runnin high boost

stealth-twntrbo · 07-26-2009, 11:19 AM

I just really don't believe dynoing with the hood close is ever going to simulate real world driving on the road. I think that as you have air flowing through the engine compartment is much different in real driving than fans blowing on it. I think dynoing with the hood open is a fair comparaison to realworld driving based on air intake temps at the filters themselves. IF you dyno with the hood closed you really heat soaking under the hood even with fans blowing its not the same as real world driving.

07-25-2009, 05:27 PM	#1
Mr. 5 Modder Raider 753 Rep 8,633 Posts Drives: M3 Join Date: Apr 2007 Location: Surf City, HB iTrader: (31) Garage List 2007 e90 335i [8.00]	When Testing an Intake, Why are People Dynoing with the Hood Open? This has always made me wonder. Of course, if there is a filter or 2 filters just sitting in the engine compartment, then of course the intake is going to show more gains if a fan is blowing air on the intake while dynoing. Better yet, you might as well get some dry ice and put it by the filters so the numbers will get even higher! It doesn't matter if the hood is open or shut with the stock air box because the engine isn't going to get any more air by the hood being open. So, I have a word of advice for people that really want to prove if an intake works. Dyno with the hood closed 3 times with the stock intake. Then dyno with the hood closed 3 times with the aftermarket intake. Or, vice versa. I don't care which is done first just as long as there is enough cool down between the switch over. If i see an increase with the DCIs or other intakes by using the above methods, then I will be sold. Becuase, I don't know about you guys, but I drive around with my hood closed. Don't you? __________________ e36 M3 Coupe, e36 325i Sedan e90 335i--SOLD Best 60-130-------------9.15 Seconds------------------WWW.MR5RACING.COM
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07-25-2009, 05:40 PM	#2
Kroy Brigadier General 173 Rep 3,032 Posts Drives: E90 Join Date: Jul 2009 Location: Los Angeles, CA iTrader: (1)	+1
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07-25-2009, 05:44 PM	#3
oddjob2021 ASR Turbos+LSD+Meth= :D 73 Rep 1,517 Posts Drives: E92 335i Join Date: May 2007 Location: Miami, FL iTrader: (0) Garage List 2007 E92 335i [0.00]	i will be testing a prototype closed box system soon mr. 5. i'll post a review for the members here as well. i'll also dyno above like you said however being a "closed system" like stock, i doubt anything will change. __________________ 2007 335i Coupe Mods: Check the Garage
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07-25-2009, 05:45 PM	#4
sleepdoc Lieutenant 258 Rep 475 Posts Drives: 2022 M3CX DG/Blk Join Date: Dec 2007 Location: South Florida iTrader: (1)	+2. I think the Intake made my 335 slower. __________________ Sold 2018 F80 M3 Sold 2010 Nissan GTR Sold: 2008 335i
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07-25-2009, 05:49 PM	#5
OpenFlash 1737 Rep 17,960 Posts Drives: A Lot Join Date: Sep 2006 Location: SF Bay, CA iTrader: (0) Garage List 2018 Ducati Panigal ... [0.00] 2016 Mazda CX5 [0.00] 2017 Aprilia Tuono ... [0.00] 2019 BMW M2 Competi ... [0.00] 2015 BMW M5 Competi ... [10.00] 2016 Ducati XDiavel S [0.00] 2016 AMG GT S [0.00] 2011 Ferrari 458 It ... [0.00] 2017 Charger Hellcat [0.00] 2015 KTM Super Duke ... [0.00] 2016 KTM RC390 [0.00]	On the road at say 50mph, underhood temps aren't much higher than ambient. On a stationary dyno, with tiny fans, and no low pressure zone under the car, underhood temps are sky high (over 200f with hood closed). That's we they are better left open. And even with a fan blowing hot stagnant air off the top of the engine. It's just closer to real world conditions. If you are testing with a massive windtunnel fan, that's another story. Shiv
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07-25-2009, 05:51 PM	#6
Zeph Major 27 Rep 1,410 Posts Drives: 2008 E92 335i 6MT SGM CR/BD Join Date: Jul 2008 Location: Southeast USA iTrader: (0)	it is hard to do... I tried it once with hood closed and the SSTT went into overtemp bypass before the 1st pull was done. You really have to have a 140 mph wind-tunnel to do it with the hood closed to simulate real road conditions. It was about 95 and high humidity that day also. I do agree if you are doing open element filter/s intakes with the hood open it is not going to be accurate.
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07-25-2009, 05:54 PM	#7
JayKay335i Banned 189 Rep 5,046 Posts Drives: ///M323 DCT Join Date: Apr 2009 Location: North Dakota; its best DUHHHHHH iTrader: (1)	Even with a fan blowing into the engine compartment I think you'd be pushing more, cooler air through the engine compartment at 65mph than a fans going to blow.
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07-26-2009, 09:43 AM	#18
mwahlert Lieutenant Colonel 95 Rep 1,659 Posts Drives: 2009 335i Join Date: Apr 2008 Location: NC iTrader: (8)	maybe a better test of performance gains/losses would be timed 20-50mph or similar runs... 50-80mph even.
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07-26-2009, 09:53 AM	#19
uberschnell Brigadier General 675 Rep 4,080 Posts Drives: Wide Body 1 Join Date: Mar 2007 Location: Bay Area iTrader: (48)	I got mine for the looks alone..but sound is nice.
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07-26-2009, 11:19 AM	#22
stealth-twntrbo Captain 139 Rep 717 Posts Drives: 2020 740xi Join Date: Jun 2009 Location: NA iTrader: (3)	I just really don't believe dynoing with the hood close is ever going to simulate real world driving on the road. I think that as you have air flowing through the engine compartment is much different in real driving than fans blowing on it. I think dynoing with the hood open is a fair comparaison to realworld driving based on air intake temps at the filters themselves. IF you dyno with the hood closed you really heat soaking under the hood even with fans blowing its not the same as real world driving.
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