I was at my race shop and had a 997GT2 oil scavenge pump / vacuum pump installed on the car. I am extremely happy with this conversion as there is a huge improvement in brake pedal feel compared to the stock 996TT/GT2/GT3 stock vacuum set up. I have been running the complete 997GT3 RS 380/350 brake system on my car for the last 3 years including the 997GT3 brake master cylinder. Even though my brake pedal has been very firm compared to the previous 350/350 set up, it still did not quite have the same feel as a 997GT3. One of my gripes has been the fact that sometimes when I would transition very quickly from full throttle to max braking, my brakes would not have quite the bite they normally have and braking would require a lot of pedal effort. Basically, what was happening was insufficient vacuum and would manifest itself on very hot days when the air is naturally thinner. I am also at a 5000'+ elevation where the air is even thinner with density altitudes in the summer approaching 10000'. I went over this with the owner of my race shop and it was decided to install the 997GT2 vacuum pump. On the 997GT2/GT3/TT, Porsche installed a separate vacuum pump which is piggybacked onto the drivers side exhaust cam oil pump. On the 996GT2/GT3/TT, brake vacuum is tapped of the throttle body. I am assuming that Porsche added the vacuum pump to improve brake feel and consistency and remedy the shortcoming of the 996 brake system.

The conversion is a direct swap. The exhaust cam oil scavenge pump is removed and replaced with the 997GT2 oil/vacuum pump. The stock 997GT2 vacuum line is routed from the pump and plugged into the stock 996 vacuum line which is just left of the F-hose. It is a direct plug in as the connectors are identical. All that is left is to remove the stock vacuum line that connects to the check valve at the throttle body. We installed a rubber vacuum cap on the stock nipple of the check valve at the throttle body. You also need to install a small rubber vacuum cap on the nipple that is on the 997 vacuum line (visible in the last picture) and that normally goes to the exhaust bypass flap on the 997 cars. You can get the vacuum caps from NAPA. Total time of the swap was about 3 hours start to finish with everything essentially plug and play.

The result of the conversion is profound and make the brakes feel identical to those of the 997GT cars. Pedal firmness is drastically improved along with improved modulation. This is a huge improvement especially for those that track their cars but it even makes a noticeable improvement in normal street driving. I can see why Porsche decided to go this route on the 997GT/TT cars. For those looking to maximize their brakes, this is a worth while upgrade.

996TT/GT2/GT3 EXHAUST CAM OIL PUMP

997GT2 PUMP EXHAUST CAM OIL/VACUUM PUMP

997GT2 VACUUM LINE

 

Glad you were able to take care of this. I bet you can't wait to put this to the track test this coming weekend! BTW, very nice write-up.

 

We learn something new every day!!!
Here's what I found in the parts cat…Very nice info, thanks for sharing….

 

It's gonna make a difference for sure. I can already tell difference just putting around in traffic. Chris knows his shiat for sure. I was cautiously optimistic about this making a difference but I'm floored by the change if pedal feel. See ya Saturday bright and early!

 

The 997GT2 has a different part number compared to the GT3 presumably due to the different RPM capability of the two engines. That's the reason we went with the GT2 version.

 

Thanks for this clarification. I'm surprised of the location which is just besides the exhaust. Must be made of very specific material….

 

Something I doubt I would ever need or do but find it very interesting= thanks for sharing.

 

Don't know. The pump has a metal case. There is a stock rubber water coolant pipe that is routed in the exact same location so temperature is evidently not an issue.

 

So are you saying by adding this pump it takes less pressure to push the brake pedal? I have always been amazed at how hard my brake pedal is to push for normal breaking.

 

The best way to explain it is that it makes the brake pedal harder and the brakes have a sharper biting point which means it takes less brake pressure to reach a desired braking input. Initially I figured the difference would mainly be felt under max braking at the track but it is very noticeable in normal street driving as well.

 

interesting, so perhaps a lower assist/vacuum(harder pedal), but more consistent vacuum(sharp bite point)?

 

Hard to say. I believe you get more vacuum and it's more consistent. I'm at a 5000'+ elevation with summer temps density altitudes climb to 10000'+ so the air is thinner and a lack of vacuum is even more apparent. Obviously Porsche felt this was a bit of a concern in certain situations thus the switch to the pump on the 997 cars. I think the advantage of the pump is that vacuum is available instantly. Prior to installing the pump I have driven my car back to back with a 7GT3 with identical 380/350 brakes (including same rotors and pads) and the brakes on the GT3 had a sharper and stronger bite point along with a slightly harder pedal. After swapping the pump, my brakes feel identical to the 7GT3.

 

nice write up !

 

To update this, I put over 80 hard track miles in 90F+ heat on the car today. The brakes performed flawlessly. Very solid pedal and totally repeatable over a 25min session. I'm very happy with this $1500 upgrade..

 

What I did in mine was to install a vacuum recervoir in line with the vacuum pick up at the t body, I have more then enough of a vacuum reserve, cheaper and simple.