Re: 3.0 vs 2.5 V6 Throttle Bodies

[George Graves <gmgraves@domain.elided>]

First of all, AKAIK, the throttle body on the 3.0 liter Milano V-6 is 
the same size as that of the 2.5 liter. I don't know about the one on 
the 164.

My experience says that the mod involving the BMW AFM won't buy you a 
thing unless you can find some way to increase the diameter of the hose 
from the AFM to the plenum and increase the size of the throttle-body. 
You will also need to fit a fuel/air mixture monitor gauge to your 
car.You simply cannot fool around with your fuel system without some 
type of feedback. To get the whole story on this modification please go 
to:

http://www.gtv6.org/index.shtml

and select "Technical" and about 3/4 down the list, choose "Larger AFM 
Installation"

I know several who have tried this mod. None found it worth the effort 
in terms of added performance (that is to say, there is no discernible 
improvement although, to be fair, nobody I know has done before/after 
dynomometer tests either). The main problem, I should think, would be 
that there is no way to get around the fact that the intake plenum 
casting sitting atop the V-6 engine has a 2.5-inch inlet opening and 
the BMW AFM has a 3-inch outlet. You CAN soak your boot in hot water 
and get it to stretch over the new 3-inch BMW AFM outlet throat, but 
it's still going to 'neck-down' to 2.5-inches on the other end. Which 
means that you really aren't improving airflow as the volume of air is 
restricted to the size of the narrowest opening in the system which is 
the 2.5-inch throat on the plenum chamber inlet to the throttle body, 
all else being equal. But what you will have to do is reset your idle 
speed and your idle mixture using the aforementioned air/fuel mixture 
gauge.

Also, since the new AFM won't fit the Alfa's air-filter box, you are 
going to have to add a new air cleaner somehow. K&N, according to the 
referenced article, makes one of their high-performance cone-type 
filters which will fit the BMW AFM inlet. The only problem is that now 
you are sucking hot air from under the hood (bonnet) of the car and 
this article does not address that aspect of the modification at all. 
The inlet to the air cleaner needs to be COLD, outside air. The stock 
air cleaner provides for that because the opening on the air filter box 
peeks through the radiator wall opening behind the grill. Several 
people I know who have made changes to the AFM  or air cleaner using 
the K&N cone-type filter have fabricated solutions involving a length 
of clothes-dryer exhaust hose available from most appliance supply 
stores like Sears. Believe me, this is necessary even though the author 
of the article does not address it.

But like I mentioned, don't be surprised that after all is said and 
done you will have just returned your Alfa to the same state of 
performance that you had BEFORE you made the modification. But I will 
say that this is certainly a cheap and effective way of dealing with a 
broken Alfa AFM setup. Alfa ones are rare and expensive to buy new or 
used, and the BMW ones are easy to find and CHEAP in any wrecking yard 
catering to European cars.

Want to increase the airflow to your V-6? Replace the stock, 
restrictive paper air filter with the specified K&N unit from IAP. It 
will give you increased airflow without you having to modify anything 
and you might just garner a few free, extra horses in the deal!

On Tuesday, November 12, 2002, at 10:07  AM, alfa-digest wrote:

>
> Date: Mon, 11 Nov 2002 22:11:37 -0600
> From: "Michael & Carmen Keith" <mikeandcarmen@domain.elided>
> Subject: 3.0 vs 2.5 V6 Throttle Bodies
>
> I'll be picking up an '87 Milano Gold on Wednesday, & I'm already 
> making
> plans to tinker.  I'm stoked as this will be my first V6 Alfa.
>
> I plan to get a BMW AFM.  They are readily available at junk yards in 
> my
> area.  I'm also wondering if using a throttle body from a 3.0 would be
> helpful as well.  Is the throttle body of a 3.0 larger that that of 
> the 2.5?
>
> Thanks,
>
> Michael Keith
> Houston, TX
> '87 Milano Gold (on Wednesday)
>
>
George Graves
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided