RE: Big bore throttle body on M20 - no gain?

["Fadeev, Alex" <Alex.Fadeev@xxxxxxx>]

"Apfelthaler, Horst" <Horst.Apfelthaler@domain.elided> wrote:
> 
> I've a question to the engine gurus:
> Some weeks ago I installed a big bore throttle body on my 2.7i
> engine (2.7eta bottom end, i head, i harness, i ecu, i cam)
> which resulted in 180+ hp at 6000rpm.

Don't forget to chip that thing!
2.5L engine with Jim C chip will dyno at 177hp with peak HP gain on 15hp @
5000rpm (http://www.turnermotorsport.com/catalog/catalog.htm). 

> I had it dynoed before and after the installation of the throttle
> body (+3.5mm in diameter) but could not see any gain in hp nor
> in torque. What's wrong here?

Nothing.
Big bore throttle body is a voluntary weight penalty.

> Is the AFM restricting the airflow too much?

Nope, it is just measuring the amount of air flowing through the intake. It
does not matter how big the throttle body is at anything other then WOT. If
I remember correctly, Jim C's re-programming actually leans out the mixture
at high RPMs. So even at WOT with the stock throttle there is plenty of air
flow. 
If you want to learn more, search the digest archives
(http://www.eskimo.com/~dalus/search.html) or get in touch with Jim C
(http://www.bonnevillemotorwerks.com/).

> Is it possible to install a bigger afm (from a big six)
> and have a modified chip? 

Sure, but why?
What you really want to do is return the waste-of-money big throttle body
and get your money back. However, I remember reading that the people who
sell those things never accept the returns. I wonder why ;-)

alex f

> Would it bring me some additional power when I install a big 
> six afm and dcalibrate it that it gives me exact he same
> electrical signals as the original afm? I can imagine to 
> calibrate them when i connect them in serial to a big fan /
> vacuum pump and and modify the output voltage / resistance.
> 
> Any Ideas?
> 
> Regards
> 
> Horst
> http://silverstone.fortunecity.com/chicane/541/

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