Effects of Rear Spoiler on Engine Temps

[mca]

I've read through some posts where it was stated that a rear spoiler will result in cooler engine temps. Some guys will actually remove the spoiler in the winter and then install it again during the summer.

Is this true? Does the rear spoiler funnel more air across the engine?

[911pcars]

It's been proven that a rear spoiler creates more positive air pressure on its top surface to either create downforce or minimize lift. If there's an opening nearby, I assume more air goes into it.

Others may say that there's also an engine fan at work pumping a sizeable volume of air over the engine surface. Whether this alone controls sufficient air flow through the cooling passages can be debated.

Sherwood

[Wil Ferch]

Porsche factory claims typical 10 degrees improvement over no spoiler......

[DG624]

I think that removing the AC cooling unit at the rear grill would improve cooling.

[mca]

Originally Posted by Wil Ferch

Porsche factory claims typical 10 degrees improvement over no spoiler......

Wow. That is HUGE.

In the summer that would put me at roughly 200F. I'd love that.

[Bob Kontak]

mca - do you have a front oil cooler? My 81 was updated with a non-Carrera type and I have never had a cooling issue,

[911pcars]

Originally Posted by mca

Wow. That is HUGE.

In the summer that would put me at roughly 200F. I'd love that.

If you're only experiencing 210ºF in the summer, you don't have temp. issues, but every little bit helps. What is it in traffic? Many owners see mid 200s and more.

Sherwood

[mca]

Originally Posted by Bob Kontak

mca - do you have a front oil cooler? My 81 was updated with a non-Carrera type and I have never had a cooling issue,

I have the elephant lines and carrera cooler. I'm not having cooling issues at all.

But I'd rather stay lower than 210 in the summer. The humidity is the real killer down here. This time of year I stay between 180-190F. In the winter I might not even see 180 on some days.

I guess I'm curious b/c I might add a tail in summer like others have done. I only have just over 12k on my rebuild and I'd like to try to keep it as cool as possible. Also, my higher compression may cause a slight bump in temps too.

[Flieger]

More downforce and cooling. And it keeps the rear taillights cleaner.

[TRE Cup]

From personal experience: Willow Springs, 85 degrees (yeah a cool day out there )
3 liter cis in a 911 targa. Saturday runs without a rear spoiler 225-240 degrees
Sunday runs with a 75 whale tail spoiler (just the standard grill opening), no other mods, same exact temps 210 max
yeah it helps cool the motor

[hbkramer]

I run a 964 spoiler on my 79 Sc and even in last summers dog days , The temp gauge needle rarly broke above the 8-8;30 mark. It dramatically reduced temps over the stock sc lid w/o a spolier.
I am running the stock trombone cooler up front ,and have postponed installing the 28 row brass cooler that I have,I just don't see the need since adding the 964 spoiler.

[McLovin]

I wonder at what speed it starts to have an effect? With a carrera or duck (or most of the others) the opening in the decklid isn't enlarged, so at idle or low speed (like around town driving), the tail can't have any positive effect on cooling.

[hbkramer]

My guess would be a high pressure vortex swirl at the deck, coupled with engine/alternator fan suction and low positive pressure under the yum yum tins,which creates porshe engine cooling magic like you have never seen before.....Sorry got carried away,but thats what is said in my Hitchhikers Guide To The Galaxy

[Wil Ferch]

Mclovin:
That is probably correct. If you study the aero charts that Porsche publishes, the aero affects don't become noticeable until higher double digit speeds, but even if the aero affect is negligable...the direction of flow into the engine compartment might stilll be improved ( and therefore temps affected)... before the aero affects are felt.

[mickey356]

It's hard to say but when I put my duck on my temps went down by about 10-15 degrees, but I also removed my AC at the same time.

[Canada Kev]

Originally Posted by McLovin

I wonder at what speed it starts to have an effect? With a carrera or duck (or most of the others) the opening in the decklid isn't enlarged, so at idle or low speed (like around town driving), the tail can't have any positive effect on cooling.

Well, if you put your hand out the window and you notice the passing air having some effect on it, then I suspect at those speeds the spoiler will provide something similar to the airflow, however marginal.

[Walt Fricke]

I used to take the duck off for the winter so I could use the ski rack which fit on the stock lid.

[chris 964]

Originally Posted by hbkramer

I run a 964 spoiler on my 79 Sc and even in last summers dog days , The temp gauge needle rarly broke above the 8-8;30 mark. It dramatically reduced temps over the stock sc lid w/o a spolier.
I am running the stock trombone cooler up front ,and have postponed installing the 28 row brass cooler that I have,I just don't see the need since adding the 964 spoiler.

+1 - I have an 88 with the front cooler, I added a 7" fan and it made 'a little' difference, added the 964 deck lid and it made a 'significant' difference..

[Quicksilver]

Originally Posted by McLovin

I wonder at what speed it starts to have an effect? With a carrera or duck (or most of the others) the opening in the decklid isn't enlarged, so at idle or low speed (like around town driving), the tail can't have any positive effect on cooling.

All aero effects increase at a cubed rate based on speed. (Double the speed = quadruple the aero forces.)

[jwakil]

The problem is that cooling is usually not an issue at speed anyway, its the idling and stuck in traffic when mine starts heating up. In those conditions, the tail is not going to do anything.