Enlarged throttle bodies?

[Cooooooperslad]

This is a performance mod that dosn't seem to be mentioned on here much! are there any real gains to be had?

Anyone done a before and after rolling road / 1/4 mile?

Cheers

George

[Paul@1320]

On the mary head thread on NAM you will see that Hubie managed 241whp with a stock throttle body.

I believe that all Kuhmo Kids test cars are running stock throttle bodies and there making 230+whp

We've seen on ours 219.9whp / 250bhp with stock rev limiter. Its one of the thingsthat we've got down on the list for testing, but I'd rather spend my money somewhere else first.

[MINI-Morgan]

Cooper or Cooper S? I havent tried one yet mainly with my thinking that the supercharger isnt going to be effected too much by increasing the throttle body at my stage and would the increase be worth the cost?

[Berthil]

I just replaced my M7 62mm throttle body back to stock.

I didn't notice much when the M7 throttle body was put in place. Or it must be that the car was running worse when trying to keeping at constant speed between 2000 and 3000 rpm. And yes, I had my software adapted to the throttle body.

Then suddenly two weeks ago the M7 throttle body didn't calibrate itself anymore when starting the car what resulted in a EML mode right after starting.

Replacing the stock throttle body back solved this problem and I again cannot feel much difference.

I'm running 250 bhp with the stock throttle body, no problems.

[Aberdeen Al]

One of the Mini mags a few months back reckoned you'd get 5 bhp on a Cooper S - that was dyno'd I believe.

When I fitted mine - it seemed to reduce my yo-yo effect although it didn't eradicate it all together.

[Richard Crofts]

I got to say I'm not of the opinion that theres much to had from them until you have gone to high lift cams, altered head, high boost and many other things that make a need for better fueling. Most stock items will cope fine until you get beyond the fueling capability of the car, even then theres more to be had through bigger injectors, altered fuel pressures and a number of other things....only then would I bother with an enlarged throttle body. Thats my opinion though.

[MINIMANIAUK]

The air demand for the engine is dictated by the supercharger,it effectively "sucks" its requirement for air dependent on its rpm and volume- if this demand is met then there is zero pressure pre charger - IF there is a restriction to the air flow a vacuum develops,and the speed of airflow is affected ,this vacuum uses power from the charger and shows as heat .
The effect of a larger throttle on the S will be minimal as the charger air demand is not greater than the ability of the throttle size (stock) to provide it.
When reducing the pulley size the charger rpm increases and the airflow requirement also increases this can get close to the throttle size limit if rpm is increased high enough ,but at that point the charger is suffering anyway with other losses.
The stock charger is rated around 330CFM or just over 210bhp mark ,when pullied this increases ,but I suspect its only at a much higher CFM that the throttle is challenged.
The opcon outsucks the stock throttle ,and lost a fair bit of power by generating a large vacuum,this has been one reason for modifying the intake pipe and trying larger throttle .
A less restrictive air filter also helps the stock charger in this respect,but does allow more noise
Anything that makes the chargers life easier will help

[MINIMANIAUK]

The air demand for the engine is dictated by the supercharger,it effectively "sucks" its requirement for air dependent on its rpm and volume- if this demand is met then there is zero pressure pre charger - IF there is a restriction to the air flow a vacuum develops,and the speed of airflow is affected ,this vacuum uses power from the charger and shows as heat .
The effect of a larger throttle on the S will be minimal as the charger air demand is not greater than the ability of the throttle size (stock) to provide it.
When reducing the pulley size the charger rpm increases and the airflow requirement also increases this can get close to the throttle size limit if rpm is increased high enough ,but at that point the charger is suffering anyway with other losses.
The stock charger is rated around 330CFM or just over 210bhp mark ,when pullied this increases ,but I suspect its only at a much higher CFM that the throttle is challenged.
The opcon outsucks the stock throttle ,and lost a fair bit of power by generating a large vacuum,this has been one reason for modifying the intake pipe and trying larger throttle .
A less restrictive air filter also helps the stock charger in this respect,but does allow more noise
Anything that makes the chargers life easier will help