Camaro XV

[frojoe]

Originally Posted by mikels

OEM fans are not typically rated in CFM. 850W is simply (volts x amps).

Obviously, that is not enough to design to for cooling requirements, so a volume flow rate vs. pressure drop is required - this is where many fans fall short as they are rated in CFM @ 0 (zero) pressure drop - which is not how you are using them (And some have dramatic loss in flow with pressure drop).

The SRX turbo fan flows:
~1.0 m^3/sec @ 300 Pa pressure drop (2119 CFM @ 1.2"H2O)
~1.5 m^3/sec @ 225 Pa pressure drop (3178 CFM @ 0.9"H2O)

So pressure decrease of 25% results in flow increase of 50%. Now you can see why flow curve (mass flow vs. pressure drop) is what you are really looking for in fan specifications.

If you extrapolate flow curve for SRX turbo fan, flow @ 0 pressure drop is on the order of ~2.5 M^3/sec (5300 CFM). (not 100% accurate as flow rates become non-linear at very high and low pressure drops)

You really need to know what the pressure drop is through your cores to determine flow rate of fans (that combined with heat exchanger efficiency will give you kW heat rejection).

BTW- Modern high-efficiency cores are WAY more efficient than old-school designs - so not as simple as looking at core thickness, size, etc..

Dave

Thanks Dave, this data is literally exactly what I was hoping for, but being the internet, was not expecting it!

I was also asking for core thickness as a reference for the rough resistance that the fan would be working against statically (not including added resistance of IC in front). Obviously dynamically there are added factors under speed such as ram air effect on some of the frontal area as well as pressure differential across the "cooling stack" due to chin spoiler, etc... just looking for a rough idea of if it's a 2", 3.5", or 17.623578" thick core.

Cheers,
Joe

[clill]

I'm pretty sure it's a 17.623579" thick core.

[clill]

What could possibly go wrong.

[PTAddict]

Originally Posted by mikels

OEM fans are not typically rated in CFM. 850W is simply (volts x amps).

Obviously, that is not enough to design to for cooling requirements, so a volume flow rate vs. pressure drop is required - this is where many fans fall short as they are rated in CFM @ 0 (zero) pressure drop - which is not how you are using them (And some have dramatic loss in flow with pressure drop).

The SRX turbo fan flows:
~1.0 m^3/sec @ 300 Pa pressure drop (2119 CFM @ 1.2"H2O)
~1.5 m^3/sec @ 225 Pa pressure drop (3178 CFM @ 0.9"H2O)

So pressure decrease of 25% results in flow increase of 50%. Now you can see why flow curve (mass flow vs. pressure drop) is what you are really looking for in fan specifications.

If you extrapolate flow curve for SRX turbo fan, flow @ 0 pressure drop is on the order of ~2.5 M^3/sec (5300 CFM). (not 100% accurate as flow rates become non-linear at very high and low pressure drops)

You really need to know what the pressure drop is through your cores to determine flow rate of fans (that combined with heat exchanger efficiency will give you kW heat rejection).

BTW- Modern high-efficiency cores are WAY more efficient than old-school designs - so not as simple as looking at core thickness, size, etc..

Dave

Dave,

As a guy with an engineering background myself, I greatly appreciate your analysis of the decisions that go into building a car like this. There's a big difference between building cars that promise on paper to be great real world performers, and cars that can back up the promise. And that difference in large part comes down to the kind of experience and knowledge that you and Mark represent. Thanks much for sharing.

The fan data is very helpful for me - I'm looking to upgrade the track day cooling on my car and I think airflow is one of the major areas for improvement. Trying to figure out the part numbers for the SRX fan, is this it?

http://www.gmpartsnow.com/auto-parts...and-motor-scat

And do you happen to have the part number for the fan controller? I'm switching over to a GM E38 controller, and am very familiar with HP tuners and the PWM fan control settings, so I think that part is straightforward ...

Again, thanks for your contributions.

Scott

[mikels]

Originally Posted by PTAddict

Dave,

As a guy with an engineering background myself, I greatly appreciate your analysis of the decisions that go into building a car like this. There's a big difference between building cars that promise on paper to be great real world performers, and cars that can back up the promise. And that difference in large part comes down to the kind of experience and knowledge that you and Mark represent. Thanks much for sharing.

The fan data is very helpful for me - I'm looking to upgrade the track day cooling on my car and I think airflow is one of the major areas for improvement. Trying to figure out the part numbers for the SRX fan, is this it?

http://www.gmpartsnow.com/auto-parts...and-motor-scat

And do you happen to have the part number for the fan controller? I'm switching over to a GM E38 controller, and am very familiar with HP tuners and the PWM fan control settings, so I think that part is straightforward ...

Again, thanks for your contributions.

Scott

SRX turbo fan part number is 25931645 as you show. PWM controller is built in to fan motor - so no separate module like Corvette fan.

Max PWM duty cycle is 90% positive polarity @ 100 Hz (need this for calibration). Size wiring & fuse appropriately - 64 AMPS peak.

First used this fan on Red Devil and dropped coolant and oil temps ~10F just by changing to this fan from 400W Corvette fan.

Dave

[PTAddict]

Originally Posted by mikels

SRX turbo fan part number is 25931645 as you show. PWM controller is built in to fan motor - so no separate module like Corvette fan.

Max PWM duty cycle is 90% positive polarity @ 100 Hz (need this for calibration). Size wiring & fuse appropriately - 64 AMPS peak.

First used this fan on Red Devil and dropped coolant and oil temps ~10F just by changing to this fan from 400W Corvette fan.

Dave

Thanks much for the prompt response! 10F is a significant improvement when you're at or beyond the edge already. I'm ordering this fan tomorrow.

Waiting to hear how Mark is doing at OUSCI, as I'm sure you are too.

Thanks,

Scott

[SlowProgress]

Originally Posted by mikels

SRX turbo fan part number is 25931645 as you show. PWM controller is built in to fan motor - so no separate module like Corvette fan.

Max PWM duty cycle is 90% positive polarity @ 100 Hz (need this for calibration). Size wiring & fuse appropriately - 64 AMPS peak.

First used this fan on Red Devil and dropped coolant and oil temps ~10F just by changing to this fan from 400W Corvette fan.

Dave

Great information. Would someone copy this over to the PWM cooling fan thread so we don't forget where it is ! Ok, so I don't forget where it is !!