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1998 996 cable throttle with 80mm gt3 cup car throttle body

Slayford85

Member
Joined
10 Oct 2018
Messages
8
Hi all, I am new to the group and thought that I would share my latest project. I have managed to fit a gt3 cup car throttle body to my 1998 3.4l cable throttle c2. I am pleased with the result and feels more responsive and more torque than before. Pleased to expand more if you are interested. Steve :D
 

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Re: 1998 996 cable throttle with 80mm gt3 cup car throttle b

Slayford85 said:
Hi all, I am new to the group and thought that I would share my latest project. I have managed to fit a gt3 cup car throttle body to my 1998 3.4l cable throttle c2. I am pleased with the result and feels more responsive and more torque than before. Pleased to expand more if you are interested. Steve :D

:welcome:

Please do expand :thumb: :thumb:
 
Yes, interested to hear more - I though there were no throttle body upgrade options for the cable throttle cars.........
 
Ah a new mod , very interested in more details :popcorn: :popcorn: :popcorn: :popcorn: :popcorn: :popcorn: :popcorn: :stay:
 
It was/is possible to get your standard cable throttle body bored out and a new throttle plate fitted to add something like 2mm to the diameter. I recently looked into it and did the maths and found it only gives a cross-sectional increase of about 4%. Some more maths (don't ask me what I did because I can't remember) suggested the power increase wouldn't be more than about 6hp, i.e. you almost certainly wouldn't notice it, so I didn't take it further.

Fitting the cup car throttle body looks like a great mod instead with much more potential for increased flow, please tell us how you did it. It's certainly something I would like to do.
 
Has anyone actually done any back to back dyno testing on a larger throttle body on the 3.4L 996 engine?

I ask because it seems that people are assuming that the standard throttle body is a restriction on power, possibly because the GT3 has a larger one and produces more power. However, the engine in the GT3 is completely different to the one in 3.4L engine in the C2/4, so the logic doesn't necessarily follow and adding a larger throttle body may not have any significant impact, or at worst may actually cause a loss in power due to resulting in a non-optimal airflow.
 
I think it's fairly well recognised by tuners that the intake system is the most restrictive part of the M96 engine. Dynomike of this parish has stated as much in his posts and he does flow bench work. If you hit google I'm pretty sure you'll find posts in other forums by respected tuners stating as much, but as usual, back to back dyno tests from independent parties are going to be hard to find.
 
Porsche changed the intake manifold for the x51 upgrade. What size throttle body did they use on that?

MC
 
The 996 X51 uses the standard 74mm throttle body.
 
update

Sorry for the delay on the update. I stumbled across a gt3 cup car throttle body on Ebay and studying the photos decided that it was possible to successfully install the throttle body onto my 1998 cable throttle 3.4L car. My main drive to carry out the work was the fact that is nothing on the market to increase the throttle body on a non fly by wire m96 engine, and also many people saying that it could not be done. It was not quite a direct bolt on part and did face a few challenges along the way. I firstly had to rotate the throttle 180 degrees so that it followed the original lines of the old throttle body. I started of by fabricating the oil breather line that push fits into the original coupler and then made a brass nipple for the fuel breather as the gt3 throttle body was blanked off. The next stage was to remove the manual idle control valve and replace it with the electric one on the original throttle body. The following challenge was the cable throttle its self as the bracket that the cable sat in originally was 2 inch's closer than that of the new gt3 throttle body. This meant that I fabricated a bracket the move the cable 2 inch's closer the pivot point. The final hurdle was the throttle position sensor to which I had to extend the three pins using a fly lead I made to increase the length by 8 inch's or so as this was now located hard up against the bulk head and the plug was not long enough to reach it's new position. the car fired up first time and after a 100 miles or so the ECU had learnt the new air flow and adjusted the fuel to accommodate. Since then I have put a further 400 miles on the car and can say it feels more responsive and revs more freely and feel a vast improvement over stock.
 
The completed project
 

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The completed project
 

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