zdet

I’m working on installing a third radiator on a 997.1 C2. I have reviewed the various DIYs and other threads on venting, and the consensus seems to be that cutting exhaust vents in the bottom of the bumper is needed (using the etched squares that are on the inside of aero bumpers as guides—noting that that the non-aero bumpers do not seem to have such etchings). Before I cut, I was wondering whether anyone knows why the X51 cars (which, I understand, came from the factory with the third radiator) do not have the cutouts (at least based on the pics I have found online)?

For what it’s worth, 997.2s with the center radiator do appear to have the cutouts. Maybe a design improvement?

Any thoughts? Thanks in advance.

EMC2

If you take a look at my thread below (although my car is a 997.2, I used the 997.1 Center Radiator Kit) you will see that the radiator mount (black piece directly behind the radiator is designed to vent out the bottom)

https://rennlist.com/forums/997-foru...don-t-fit.html

zdet

Thanks. I understand that. The question is whether cutouts are needed in the bottom of the bumper to allow air to escape out the bottom? Many of the threads (including yours linked above) conclude that cutouts are needed. My reservation is coming from (what seems to be) the fact that non-aero X51 cars with the third radiator don’t seem to have the cutouts from the factory.

zdet

For reference, here's a picture of the subject cutouts from Carrera Mike's awesome DIY:

andino

The air dam behind the radiator funnels the air downward. I suppose you don't HAVE to cut the holes but you're reducing the amount of air that can flow through the radiator by restricting the egress. There's a small gap between the under tray panels without cutting the holes if you're so inclined to not cut vents. But if you're going through the trouble of installing the third rad, why not just cut the hole so you get the most of the radiator?

Also fwiw, not all x51 cars came with the third rad. There's a couple thread of users adding the third rad to their x51 cars.

Eric Buckley

The 997.2 Installation instructions say to cut the holes.

For some reason I can't seem to attach the pdf, but here's a picture of the holes:

campbesl

I installed the 3rd radiator on my 997.1 2008 C4S without cutting the holes. I observed plenty of gap space for venting so decided the holes were unnecessary. Performance of the added radiator seems perfect though that's subjective rather than objective.

TopKatz

I have no holes cut for my third rad on my 997.1 C4s. I have yet to explode.

Dk27

I have the third radiator with the low temp thermostat without holes cut. My oil temps are around 20-25 degrees lower since the combination was installed.

yvesvidal

I have installed the third radiator and cut-out the four openings at the bottom. Despite this, the front frunk compartment gets very hot in the summer time, to the point that my GPS unit stops working, due to the heat.
Similarly, anything stored in the frunk (food or otherwise) will be fully cooked after a long trip in 100 degrees outside temperature.

Honestly, the cuts in the bottom are not enough for air to escape.

Yves

zdet

Thanks all. Really appreciate the input.

Thanks for the clarification. Can anyone with a .1 X51 with a factory-installed third radiator confirm whether their bumper had the cutouts from the factory? I found pictures of a few .1 X51 cars online (mostly from BaT listings), and all of them had the third radiator (of course, they could have been installed using the kit) and all of them had the non-aero front bumper without cutouts.

roadie13

To add some more possibilities to the mix: my 2005 C2S was going to have the holes cut but then the mechanics found a venting gap at the bottom bumper (see pic below). Apparently, this was the standard bumper shape for a tiptronic car (mine is 6MT), which had a third front radiator for transmission cooling as standard. It remained a mystery why my car had that bumper. Maybe the X51 model used the same modified bumper shape?

BTW I experienced less of an overall temperature drop after install, but the oil temp would come down more quickly from a peak after heavy driving, say on the track.



Upper lip is the air guide from the radiator kit, lower lip is the tiptronic bumper.

Center attachment of the tiptronic bumper, looking forward from underneath the car. Air flows out backwards through the gap.

Petza914

If I were doing it, I would go get some metal spacers (1/2" - 1" whatever will fit) from the store with some longer screws and create a gap at the back of the panel for the air to escape out the bottom.

zdet

@roadie13, you may be on to something. The PET does appear to show different part numbers for the 6MT vs. Tip bumper covers.

TexRedC4S

It wasn't long ago I looked into this and after reading many posts here and in other 997 forums, I decided to vent. Much like Carrera Mike, i cut holes in the bottom of my bumper. I used his photo and scaled it best I could. It was very easy. I added some screen to cover the holes by cutting the screen pieces larger than the opening and epoxying the screens to the bumper. A pic is attached. I would imagine that without the venting the frunk would get hot. With the venting, I didn't see any increase in temperature in the frunk area. I think it is needed.


The view is looking down, with the front of the bumper at the top of the pic. you can see the radiator openings at top with the same grill / mesh material attached there too.