Example Giac tune 60HP,IPD Plenum 30HP, Fabspeed bypass pipes 17HP. Does that mean that total HP gain is 107, or do the gains change when done all together ? Hope my question is worded properly !!!

 

I'm surprised none of the vendors have replied. My thoughts would be it would be cumlative and slightly higher as some of the mods play off one another (GIAC and bypass pipes). With that said, I'm not convinced the IPD gives a 30HP bump. Jason @HouseMotorsports has a client who is going to dyno it so we'll see.

 

My guess is not. I have modded the heck out of my 991TTS but not the Cayenne TTS yet. My wife doesn't want me to and it's hers so I have held off but I am going to do the plenum. The plenum is a bump in the mid range of RPM so you don't feel it up top as much I don't think. The GIAC will be spread across the range and help the car top out better. I have on the 991tts a FVD exhaust with 200 cell cats, FVD Brombacher headers, IPD plenum and FVD tuning module (piggyback).

The car turns 131mph at 10.5 type quarter mile times and I had a 16.8s 1/2 mile where my terminal speed was 151 and trap was 155 so I had actually slowed down before I got to 1/2 mile due to road conditions. I use Vbox for measuring the effect of the mods. Prior to the mods my best 1/4 was 10.9 @ 125 and my best 1/2 was 17.1 @151.

The car is a lot, lot faster with the mods now. I think I have about 650hp but cumulatively it would be more. However, I have a lot more pull up top and that is evidenced by the very strong 1/2 mile trap speed which would probably be 158 if I didn't slow down early, the peak speed on that run was 157 when I hit the brakes.

I am going to the Texas Mile in March so I will see what the car can do in a full mile run. I am looking for 190ish. I am planning to rent a car trailer and pull the 991tts behind the Cayenne TTS. Should be kind of a cool way to go.

 

When manufacturers make horsepower claims, and when they perform dyno tests - typically they do a baseline pull on a completely stock car first, then add their modification - then perform a second dyno run to see the gains vs. a stock vehicle.

I'd say the gains wouldn't work in a super structured scientific way where we would come up to exactly 107hp - because you introduce variables when you add additional modifications to the mix.

However as HOiYA has stated - there are mods that work extremely well in conjunction with one another - especially when it comes to increasing boost levels and improving airflow. The goal is to eliminate and relieve as many restrictions as possible. The more you open up the flow, the better performance you'll get.

I really think the emphasis needs to be put on overall improvement over the stock configuration on these Cayennes. I can't remember ANYONE being disappointed with their new found performance for the price they paid for some secondary catbypass pipes, intake plenum, and GIAC tune - at the very minimum. Not a single person I speak to says 'this wasn't worth it'.

At the end of the day, if you are looking for increased performance, without any negative effects in terms of driveability (this is such a KEY factor when modifying cars) the basic bolt on mods that are commonly discussed here make a lot of sense if you have some discretionary fun money to do so.

I know I've spoken to a good handful of Cayenne guys from the forum already, but if you ever have any questions or just want to talk shop - feel free to give me a ring at the shop, always happy to help!

- Jason
626 539 2911

 

Another item to keep in mind is that certain claims like the IPD plenum are rated at different points in the power curve. So while the plenum might make 30 wheel horsepower at 4,500 RPM, it might only be worth 12 wheel horsepower at redline. This is in contract to GIAC for instance, where they quote gains on the peak numbers (highest point of the stock power curve vs. highest point of the tuned power curve).