closed vs open hood dyno/tuning

[zxmarekxz]

anyone that is in the know. what is better, or application specific?

 

[JoshK]

I would think that almost always your hood will be open for a dyno tune since they would want to keep under hood temps down, may also have wires ran to the engine.

 

[06silverbullet]

hood should be open, firstly keeps the car cool while under high rpms as the car isn't moving.

 

[3vs197]

they just hook up a wire to the coil to monitor RPM's.

 

[Rene06GT]

open cause as stated u aint going anywhere so the fan the put in front wont equal what u get under wot on the street. plus it helps cool the motor and comp for the lack of air flow in to the bay.

 

[zxmarekxz]

hood should be open, firstly keeps the car cool while under high rpms as the car isn't moving.

right , but winds can be replicated...

 

[zxmarekxz]

open cause as stated u aint going anywhere so the fan the put in front wont equal what u get under wot on the street. plus it helps cool the motor and comp for the lack of air flow in to the bay.

hmm, ok. i guess. i dunno, i figured Id ask some pros

 

[Chiron]

I guess I'm the minority.. Stick a fan in front and close the hood for the most accurate, true results. How often do you drive around town with your hood up?

 

[NastyStang113]

Hood up. Hood up or not isn't going to effect the numbers.

they just hook up a wire to the coil to monitor RPM's.

And a line for boost if you've got F/I.

I guess I'm the minority.. Stick a fan in front and close the hood for the most accurate, true results. How often do you drive around town with your hood up?

How often do you drive you car sitting still inside a hot building?

 

[Chiron]

How often do you drive you car sitting still inside a hot building?

I was just saying that, to me, it seems like a more accurate representation of day-to-day driving would be done with a giant ass industrial fan in front of the car and the hood down. Sure, IAT's will suffer, as will performance, but I would imagine it could result in a more accurate tune, much like a Mustang Dyno is loaded to represent real-world conditions. No personal experience here, just thinking out loud.

 

[jeff s]

I've never attended a dyno session either but if the point is to compare CAIs I think you should run hood closed.

Otherwise it doesn't matter as long as you are comparing apples to apples.

 

[NastyStang113]

I was just saying that, to me, it seems like a more accurate representation of day-to-day driving would be done with a giant ass industrial fan in front of the car and the hood down. Sure, IAT's will suffer, as will performance, but I would imagine it could result in a more accurate tune, much like a Mustang Dyno is loaded to represent real-world conditions. No personal experience here, just thinking out loud.

Here's the thing. On dyno graphs when the weather conditions create a need for a correction factor to be added it actually results in high numbers a lot of times. Now if you have a cooler temperature, decent barometric pressure and humidity you'll be getting a more accurate number because it won't have to add a correction factor. At the bottom of most dyno graphs, at least it should, will show you what the correction factor is.

Dynojet also has an add on for load control which uses an eddy current. In all reality there is no need for a loaded dyno to tune correctly until you start getting into big numbers and/or turbos.

 

[Zexford]

here's the thing. On dyno graphs when the weather conditions create a need for a correction factor to be added it actually results in high numbers a lot of times. Now if you have a cooler temperature, decent barometric pressure and humidity you'll be getting a more accurate number because it won't have to add a correction factor. At the bottom of most dyno graphs, at least it should, will show you what the correction factor is.

Dynojet also has an add on for load control which uses an eddy current. in all reality there is no need for a loaded dyno to tune correctly until you start getting into big numbers and/or turbos.

but how will we compare ourselves over the internet?

 

[HellsBells]

accurate representation of day-to-day driving

I think this is the key phrase. There is nothing about a dyno pull that accurately represents any specific kind of driving.

With that said, who really cares? I doubt it will make an ounce of difference. If you wanna fudge dyno numbers, do a pull with the engine dead cold. You'll get a higher reading than when the engine is at operating temp.

 

[Big50]

A giant industrial fan can maybe produce 40-50 mph winds, which i doubt that much. A 4th gear dyno pull would put you from around a 100 mph to around 140 mph depending on your gearing. A fan can not compensate for that kind of wind.

 

[Chiron]

I'm not speaking in terms of numbers at all, don't get me wrong. If you're just looking for numbers, open the hood and put a fan on it, lower the IAT's and add some timing. That doesn't seem representative of the actual driving the car will see, hence my bringing up loaded dynos. But, why would a loaded dyno not be important until higher power levels? I would think that all cars would benefit from a more realistic scenario. I'm not disagreeing with any of you guys, I'm just trying to understand where you're coming from.

 

[Marc s]

The big fans might blow at 40-50mph. However, the volume of air is not even close to driving down the road. I tested IAT's last year with my car on the same day. With the hood open, my IAT's were 88 degrees. On the street in 4th gear, my IAT's were 94 degrees. On the dyno, hood shut with 2 48" commercial fans, my IAT's hit 176 degrees.

 

[fdjizm]

but how will we compare ourselves over the internet?

This is one of the more important questions.

 

[3vs197]

A fan can not compensate for that kind of wind

However, the volume of air is not even close to driving down the road

THIS.

 

[NastyStang113]

but how will we compare ourselves over the internet?

The text you made bold has nothing to do with numbers. It has to do with accurate tuning.