What and where to get them? sounds like it should be a mod once I find I need more... tomorrow! hahaha

 

Excellent question! I have heard of atting a GT3 throttle body.... are they much bigger than stock? I understand a bigger throttle body and plenum provides a noticeable power increase??

Jason

 

Caution!

Like throttle response?

It'll go by-by if your intake capacity is increased significantly.

That's the tradeoff - more top-end power, or maintain driveability.

 

thats kind of what i figured, im not sure why so many people are saying its a good power mod! Its like putting on carb thats too big, loose all throttle response

 

Do larger diameter throttle bodies effect intake capacity? My impression was that a larger throttle body would actually allow air into the intake manifold faster/less restrictive, and in essence have a similar effect as an aftermarket intake? If anything wouldn't a larger throttle body increase throttle response?

Could you explain the dynamics here.... would the decrease in response be negligible or very noticeable...

Jason

 

If the throttlebody was the smallest restriction in the intake system, you would be correct. However, it is not. Additionally, changing throttlebody size (or the size of ANY part of the intake system) effects the velocity of the intake air which in turn, will effect the performance of the engine. The effects can be either positive or negative depending on the setup.

 

I too was looking into this ......I cannot remember where I saw the throtle body though!
I am trying right now to re-trace my steps to find it!

Stacy

 

So, do you think an X-51 Air box intake would effect the flow of air significantly to perhaps lose HP due to the larger diameter flowing into a smaller stock TB of a non X-51 997/S?

 

Larger to smaller will increase air velocity and will change the power curve. You would not lose horsepower.

 

Remember what ever mods you all do you will need to re-map the fuel and ignition maps in the ECU for the mod and the car to work properly.

Do your mods as a system...adding this here and there is not the way to do things. Work with a knowledgable Porsche tuner so that you do the proper mods for a street car and that you get the proper fuel and air ratio and ignition timing.

 

This is a little deceiving, just a little bit, as most modern ECU's are learning computers and will adjust to varying air fuel ratio's on their own. Understand I am talking about the differences an intake or exhaust might make as the changes in pressure and air fuel ratios are very small, hence why they do not make much power on an NA car. Forced induction is different or going from NA to Forced induction....

If this was not the case then Porsche owners at high altitudes and lower pressures would have to run different ECU tunes compared to owners at lower elevations. Same is true for hot, cold, and humid climates. In the Carb days taking your car from one extreme to the other required re-jetting or optimizing the carb for the climate. If you have ever driven a carb equipped motorcycle from sea level to altitude, you get a very good representation of what I am talking about.

I do agree that the ECU can be optimized to work with your specific mods but it is in no way a requirment for someone changing their intake or exhaust components...and you are correct that it should be done by experienced shop. A set of headers or cats on a 997 might give you 10Hp and I would guess that an optimized tune might give you another couple ponies....

Jason

 

This is assuming that the larger diameter is tapering down to the smaller diameter, and not an abrupt change...right? Would the abrupt change cause more turbulence, thus negating any benefits from a higher flow velocity?

 

Turbulance can be good and like the size of the throttlebody, it's effect will be different for each intake design. Your stock intake system is designed to create turbulance of the air at different engine speeds and loads using a resonance valve.

 

I'd agree because it's actually a decent size and there's further restrictions in the system that neck it down far more anyways. It's not like the piddly 996TT one that uses the small boxster TB....

 

Sharkster, what is your opinion on proper ECU tuning when you start changing airflow through the engine?

Personally from experiance I have with other cars, performance boats and some motorcycles...when you change the airflow you need to program the fuel map and ignition map to compensate for these changes. These type of changes are far greater than someone operating the car at sea level or 4000ft in a mountain.

Please correct me if you feel I am wrong...thanks!