RE: Anyone using a aftermarket fuel boost valve?

[Aleksander Mierzwa <alex@matrix.com.pl>]

Gerard wrote:

	>This makes sense. So, please correct me if I'm wrong (as I've
said above
	>I am a bit backward and stupid, but willing to learn), if
fuel:air ratio
	>is
	>above this then the motor runs rich, right? When does lean
running
	>occur?

Too much fuel = engine runs rich
Too little fuel = engine runs lean
Both affects negatively performace, emissions and engine durability.

	>I know doing things like fuel boosting can negatively affect
	>performance. It's
	>like slapping on larger wheels. I guy in this town also has a
Audi Turbo
	>in
	>the same candy apple red as mine, but he has put on 17 inch
Antera mags,
	>so it looks mean, but obviously he has now affective his
performance
	>'cos
	>the motor surely doesn't have the right torque and power curves
to drive
	>those things. Right? He'd probably be better off running on the
stock
	>15inch
	>wheels.

Changing to larger rims does not hurt performace as far as correct tyres
are installed. Installing larger rims requires changing to lower profile
tyres, so the diameter of the wheel does not change. Let's do a little
excercise:
The stock Audi runs on 15 inch rims with 205/60 tyres. 205 means that
the tyre is 205mm width, 60 means that the "profile" of the tyre
(sometimes referenced to as a "height" of the tire, this is exactly the
height of the tyre sidewall, eg. the tyre radius minus the rim radius).
205 * 0.6 = 123mm. Now convert the rim diameter to metric: 15 * 25.3 =
378mm. The overall diameter of the wheel equals to 378 + 123 * 2 =
624mm. OK. Now we are installing a 17in = 430mm rims. To retain the
diameter of the wheel we need to put 205/xR17 tyres. (Installing larger
rim usually makes you want to install wider tires, let's retain the 205
size for comparision now).
We have 430 + 2 * ( 205 * ( x/100 ) ) = 624, so x = ( 100 * ( 624 - 430
) ) / ( 2 * 205 ) = 47,3. Tires with "47" profile are not being
manufactured, so you'll have to put up with 205/50R17 or 205/45R17 tyre.
By applying these equations you can notice that 215/45R17 will give you
almost exactly the same wheel diameter as 205/60R15. Problem is, it will
rub on the fender :-(

	>this list. I was planning to throw away US$500 for a Superchip
mod, only
	>to discover that the same thing can be done by myself since I
have all
	>the
	>reprogramming and electronic equipment right here where I work.
As I've
	>discovered from this mailing list this tuning at WOT can be
accomplished
	>by remapping the fuel pump cutoff tables in the Hitachi MACxx
ECU found
	>on these vehicles. I've still got to get back to the person who
is
	>helping
	>me with that topic, I'm just working on finding out what is
useful and
	>helpful to fit to these vehicles (and, urh, boost valves are
not :-> )
	>Also, there are some mods that can be done to the vacuum piping
at the
	>wastegate (which seem a bit dangerous to me), and the boost
pressure can
	>be set in the ECU.

Remapping the ECU by yourself can be a tricky job, since lot of "trial
and error" work is involved into getting satisfactory results. However,
if you feel you stand up to the task, then good luck, hope you will give
the list a discount on your chip when you finish developing it ;-)

	>On the note of on increasing the _mass_ of _air_ entering the
engine and
	>cooling it, would there be any advantages in sealing all air
pipes with
	>some sort of heat retardant/sealant? K&N air filters also help,
but are
	>pricey in this country, but are reusable which is a good thing.
K&N also
	>manufacture air induction kits. They claim to have an induction
kit for
	>the K-Jetronic injection systems used on these Audis. Do you
have an
	>opinion on fitting these good breathers? How about ducting the
intake
	>pipe to somewhere on the front of the car, instead of it
sucking in
	>hot air from the engine bay? The problem with the induction
kits is
	>that they eliminate the box and expose this mass of area and
filter
	>through
	>which the car can breath, but obviously it is now sucking a
whole lot
	>more
	>air from the engine bay area. But I'd like to find out more
about these
	>filter kits.

	>Again on the topic of the heat seals, they're supposed to
reduce
	>temperature
	>so would wrapping the air pipes in the stuff cause let heat to
be
	>transfered
	>to the piping (and air within) from the heat in the engine bay?
No, I
	>didn't
	>see this in some ad, I just see some silver heat seals in my
engine bay
	>near
	>the turbo and it is already sliding off.

The insulation you see in your engine compartment is mainly to protect
various components from the heat generated by the turbocharger and
exhaust. Wrapping the intake ducts with heat insulating material can
help a little, the more sophisticated method is coating some elements
with special ceramic material. Feeding the engine with cold outside air
is a good idea, although if you happen to travel a lot on dusty roads I
would expect air filter to require much more frequent renewal.
There's lot of high-flow air filters on the market, I guess you should
limit your choice to the ones whose manufacturers can supply some hard
evidence (like dyno tests) that their product really increases HP.
Filters that replace your whole airbox will usually also alter the sound
of the engine.

Aleksander Mierzwa
Warsaw, Poland
mailto:alex@matrix.com.pl
87 Audi 5000CS turbo (mine)
88 Renault Medallion wagon (mom's)
91 mountain bike (just in case both cars broke at the same time :-)