Rear vs side exhaust exits pros/cons?

[beeman]

I was admiring the new Ford GT and noticed that on the Le Mans car, the exhaust exits were moved from the rear to the side. Did they do this just for the rear diffuser (but the street exhaust is high so it doesn't seem like it would interfere)? What other reasons would there be? Would you ever do this on a street car?
I'm guessing that this would be louder in the cockpit, is that true? What other cons on a street car?

https://cnet3.cbsistatic.com/img/10Ea_fgroIN1EBqopRpbzjwTs2Q=/970x0/2015/01/12/75c273aa-460c-464c-a495-4516f8ee214f/ford-gt-4805.jpg

http://4.bp.blogspot.com/-VMpW1ES-vBM/VotGRwuGuqI/AAAAAAAABck/UwhkLDkoR4M/s1600/Ford-GT-Race-Car-rear-three-quarters-03.jpg

[VRaptor SpeedWorks, LLC]

My guess is that it is more of a serviceability and heat issue. During a race, if they need to access anything in the engine compartment, the exhaust is going to be in the way of almost everything and will be adding heat to the engine bay. Keeping the exhaust as short as possible by bringing it out the sides keeps the heat to a minimum, keeps the runs short for better performance and keeps the exhaust system itself out of the way in case they'd have to do a trans swap or even axle swap during a race.

[beeman]

Great points Shane. Would you ever consider this on a street GTM? I'd consider it to create a storage space at the rear of the car for luggage. My biggest concern would be the noise (especially for my wife), is that a legitimate concern? I have read that one concern is the hot exhaust under the gas filler location, but I could move that.

[Roger Reid]

My guess would be rules concerning blown diffusers.

[crash]

It's all heat. This is typically done on turboed cars because they run hotter and you want the exhaust run as short as possible. No need for long primary headers on a turbo car.

As for a GTM, I would do it if it was a race turbo car, but if it wasn't it would be awfully loud. The car would never be able to run Laguna Seca or the 25 hours of thunderhill because of noise restrictions. Way too loud for the street, even with turbos.

[VRaptor SpeedWorks, LLC]

Great points Shane. Would you ever consider this on a street GTM? I'd consider it to create a storage space at the rear of the car for luggage. My biggest concern would be the noise (especially for my wife), is that a legitimate concern? I have read that one concern is the hot exhaust under the gas filler location, but I could move that.

As crash mentioned, this might not be the best idea for a street GTM. Would be pretty tough to do in a GTM since there isn't a whole lot of room between the rear tires and the back of the fuel tanks.....I suppose you could get really creative and find a way to snake a pipe thru there, but you aren't going to have room for mufflers at all.

[beeman]

Thanks for the replies, probably not worth the hassle.
Here's a couple nice pics of the Ford GT race car, exhaust comes right out of the turbo, I bet that sucker is loud.

http://st.hotrod.com/uploads/sites/21/2016/03/055-2016-Ford-GT-Ganassi-Sebring-Prep.jpg

http://st.hotrod.com/uploads/sites/21/2016/03/116-2016-Ford-GT-Ganassi-Sebring-Prep.jpg\

Here's what they put in place of the rear exhaust tips - rear camera and rear sonar!

http://st.hotrod.com/uploads/sites/21/2016/03/173-2016-Ford-GT-Ganassi-Sebring-Prep.jpg

[Fraser D]

Serious car porn right there!!!!

[crash]

Quit interesting to see the long runner intakes on a turboed car. I don't recall seeing that before on any serious race car that was turbo charged. I'm sure there is a reason. Also interesting that it is not a common plenum. Again, not something I recall seeing on a turboed race car. Maybe it is running like two separate 3 cylinder engines? Double O2s in the exhaust is interesting too. Could be redundant systems for the endurance purpose, or...??

As a side note, that thing looks like a NIGHTMARE to work on!

Here's the most complex, tight car I ever worked on, but it pales in comparison to that GT. Looks like the intercoolers have to come off with the bodywork?

[beeman]

Crash,
I think that Ganassi GT is so freaking sexy.
There are about 180 images of it I found backwards through hotrod.com. You can see most of them legitimately at hotrod.com, but you can't download them and they are displayed at a lower resolution.
Enter this link below, and change the BOLD number from 001- 180 or so, there are a few images missing that they took down (probably by order of Ganassi), but man are they cool. And good resolution.
http://st.hotrod.com/uploads/sites/21/2016/03/173-2016-Ford-GT-Ganassi-Sebring-Prep.jpg