Under hood temps and dynoing with the hood up explained

Tucker

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It seems there is a misconception on the under hood temps with a cold air intake and dyno testing with the hood up vs hood closed.

99% of all dyno shops do not have fans and HVAC to simulate driving speeds and air flow. Most have a simple fan to blow on the radiator tokeep coolent temps down, but that's about it.

NASCAR shops and bigger places like Arrington have full on dyno cells that will keep temps in the room what ever you want and have fans that simulate the speed the car is moving (or would be moving) that flow over the car.

A dyno run is to measure HP, the HP you would have on the street or track. Basicly in a 1/4 mile WOT run. In a 1/4 mile run your car will reach anywhere from 110-130+ MPH and at those speeds your underhood temps are at or near ambient air temps.

So dynoing with the hood up is only getting ambient or close to ambient temps to the filter, just like it would see while driving and that's an apples to apples test.

Dynoing with the hood closed and a small shop fan will increase IAT temps beyond what they are on the street and give a false reading.

Also, yes, when in traffic and low speed driving your temps will increase, but that's not when you need the power. It's when your NOT in traffic and are moving much faster. Plus with the opn filter the higher temps come down faster too.
We have also tested the stock airbox and it also increases temps at idle and low speed.

This is easy to see for yourself as long as you have a tuner to datalog with.

We did some video to show you exactly what we are talking about. Most of the time the IAT's are 4-10 above ambient, not hotter like you would think.
Video: DYNO TESTING WITH THE HOOD UP EXPLAINED - YouTube

Thanks
Jay
 

Tucker

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We're just trying to give some facts.

Underhood temps at speed are not as hot as you think and this is something anyone can do and see.

Datalog your IAT's from 40-120mph just like a run on the dyno. Your IAT's will be ambient at the end of the run, just like a dyno run with the hood up.

So many people think that it's hotter under the hood because they get that rush of hot air when they pop the hood.
Yes at idle everything under the hood is hotter, but there is lots of air flow under the hot while driving.
 

Riptide

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I think kenne bell likes to brag about their dyno results being taken with hood down and no fans. El oh el


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SicShelby09

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I understand your side of this according to the IATs, but what about the simple fact that the filter is going to get much more airflow without the hood covering it up?? Thats always what I was wondering. Take the lid off the stock airbox, add a K&N filter to it and whats that do over stock? I cant see why people would debate the temp thing, as you proved. But the fact that the airflow is much better with the hood open is what I always wondered??
 

Tucker

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I understand your side of this according to the IATs, but what about the simple fact that the filter is going to get much more airflow without the hood covering it up?? Thats always what I was wondering. Take the lid off the stock airbox, add a K&N filter to it and whats that do over stock? I cant see why people would debate the temp thing, as you proved. But the fact that the airflow is much better with the hood open is what I always wondered??

Same answer, air flow at speed.

With the hood closed and your going 40-120 MPH you are ramming tons of air in the airbox or CAI airbox.

Samething. With the hood up your not "ramming" any air, just allowing the filter to breath it. Closed hood and poor fans will increase heat above normal driving and not get equal air to the filter.

Also, to answer your question about lid up dynoing. The car goes crazy, it doesn't like it at all.
 
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TheCPE

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but what about the simple fact that the filter is going to get much more airflow without the hood covering it up?? Thats always what I was wondering.

Exactly.

You are disadvantaging a closed box versus an open filter in an environment not similar to actually rolling down the road with plenty of air being forced into the closed box.

If the dyno and real world environment were the same you would see the same gains in the real world that you do on a dyno but you don't.
 

Tucker

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Exactly.

You are disadvantaging a closed box versus an open filter in an environment not similar to actually rolling down the road with plenty of air being forced into the closed box.

If the dyno and real world environment were the same you would see the same gains in the real world that you do on a dyno but you don't.
a
Actually your wrong, every car with an intake has run faster than it did with the stock box. The best part is all the intake haters are the ones who proved that.
Every time you guys do a test the best runs are with the JLT, not the stock box.
The fastest n/a GT runs a JLT, not the stock box. So good post, but it's 100% false.
The thread is to show underhood temps and dyno testing, so let's talk about that not mud this up about track times, those threads are all over with the same results, they get closed because the proof if there for the intake, but you still want to argue.
 

JC_SapphireBlue_GT

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100% agree with the OP, solid facts that are easily understandable.
again this thread is not directed at CAI's its for IAT's.

CAI's do help a cars performance, just for the record also.
figured i'd just leave that there ha.
 

TheCPE

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a
they get closed because the proof if there for the intake, but you still want to argue.

:nono:

So are you denying that the dyno environment is unrealistic and puts the stock box at a disadvantage that doesn't exist in the real world?
 

TheCPE

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CAI's do help a cars performance, just for the record also.
figured i'd just leave that there ha.

Sometimes I wish I could just say things and that made them facts, would make life much easier!

My testing proved this completely false.
 

TheCPE

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Same disadvantage to jlt has.

Huh?

No.

The JLT is not enclosed in a box and thus with the hood open stationary on a dyno has no unrealistic resistance sucking in air that wouldn't exist rolling down the street.

The stock box on the other hand is enclosed in a box and thus when the vehicle isn't rolling down the street having air forced into the box it is experiencing an unrealistic environment that does not exist when on the street.
 

mikestoyz

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Huh?

No.

The JLT is not enclosed in a box and thus with the hood open stationary on a dyno has no unrealistic resistance sucking in air that wouldn't exist rolling down the street.

The stock box on the other hand is enclosed in a box and thus when the vehicle isn't rolling down the street having air forced into the box it is experiencing an unrealistic environment that does not exist when on the street.

So you are saying the stock air box has the advantage because it benifits from the ram air effect of a sealed system?
 

TheCPE

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So you are saying the stock air box has the advantage because it benifits from the ram air effect of a sealed system?

Hrm, let me re-read what I wrote to make sure I'm not mistaken...

The stock box on the other hand is enclosed in a box and thus when the vehicle isn't rolling down the street having air forced into the box it is experiencing an unrealistic environment that does not exist when on the street.

Nope... I sure didn't say that.

Mostly because that doesn't make any sense.:beer:
 

five.slow

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in my lightning anything over 25-30mph i was seeing ambient air temp at my IAT which was about 1 inch behind the filter so tucker makes 100% sense to me. no way would i dyno my car with the hood shut.
 

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