GP964

Has anyone installed a larger throttle body on a 911 C2? if so, is there a noticeable difference? more grunt & pull on acceleration? positive & negative outcome?
I bought an extra throttle body to have it bored larger, can anyone recommend a company that does this bore out conversion?

Thx
GP

Bill Gregory

There's a company that advertises in Excellence pretty regularly, and I've read of others using them for their throttle body (haven't used them myself). Contact: Ed Mazula, 800-792-9338 or email ed@bigborethrottlebodies.com....located in CA

Phil Raby

This has been mentioned here before, and the general consensus is that, changing the throttle body alone, makes little or no difference.

I for one would be interested to know if anyone has proof of this though...

Phil

RSAErick

I've investigated this topic in the past, and hear that you need to couple the big bore throttle body with an adjustable fuel pressure regulator to obtain the maximal effect.

If you are interested in having yours done, while not paying as much as Ed charges, you might want to contact Jim at Proflowdesign . He was significantly less $$$ for the same work.

Good luck, and let us know what you decide to do!
Erick

tonytaylor

As I understand it (which isn`t saying much) a `90 C2 comes with the aluminium plenum and dual choke throttle body which is thought to flow less than the later plastic plenum and single choke throttle body ( ala RS type throttle body). So, if you have a replacement throttle body and it`s a single choke I`m not sure it will fit if you have a aluminium plenum.
AFAIK increasing throttle body diameter without other (engine management) changes gives little gain.
My C2 has a rebored throttle body but as it was done in conjunction with numerous other mods so I can`t pass judgement on it`s effectiveness in isolation.

Erick,

Why you would need "an adjustable fuel regulator" ( ???? is that anyway!) to maximise benifit? ( answer is probably obvious and I`m a bit thick)

Adrian

Dear GP,
The cross sectional area of the throttle body valve is designed inconjunction with the airflow sensor. The engine management system will only react to measured airflow. If you change the throttle body valve alone the result will be "Null" simply because the ability to take in more air is not matched by the ability of the airflow sensor to measure this air. This does get quite complicated and I written a few detailed pieces on this subject on this forum but they may be missing since the change over.
Ciao,
Adrian
911C4

PS: I have done quite a lot of research on this subject and basically these kind of mods are a waste of money. The engine will suck in as much air as it can get. The value of the larger throttle body is that it reduces the restriction to the airflow.

GP964

Hi Adrian,

Will having a larger throttle body provide any gains?

Here's my set up

90 C2
Autothority MAFS
Custom Calibrated Chip
Dual outlet Tezet exhaust w/ cat bypass
LWF
2 Profire Ing Coils


Let me know

Thx
GP

Adrian

Dear GP:
From the research I have done the answer is no. The problem being the MAF requires a converter to provide usable information to the original DME. The original DME will only recognise a maximum input of 4.6V so this is the largest amount of measured airflow. If more air is allowed in the DME will not see it and will not adjust the fuel injection level to take advantage of the extra air. The main limiting factor with the fuel injection system is the number of times or the frequency that you can actually pulse (open and close) the fuel injector.
I doubt the money spent will provide any additional measurable advantages.
Ciao,
Adrian
911C4