[Diy_efi] RE: 18t injector upgrade to more horses

[Perry Harrington]

Scott,

Just changing the injectors on a 150 or 180HP 1.8t *WON'T* do squat.  You
must have the NEED for larger injectors.

In fact, all you do is piss off the computer and get bad gas mileage.

The stock injectors are adequate for quite a bit of hotrodding on the stock
motor.  The issue with the stock motor is this:  the Motronic ME systems
will cut *fuel* if they cannot control the boost of the turbo.  This is
a self preservation feature.  If you try to blindly increase boost (the
most common way of making more power with OE turbo motors), you'll just
piss off the computer and end up on the side of the road every time you
dip into the throttle too much.

Your choices for hotrodding the stock 1.8t are airflow improvements and boost
manipulators such as the BCS.

If you improve the airflow through the motor without futzing with boost, you'll
realize HP gains.  The first place to start is the intercooler.  Upgrade to
the 225HP TT intercoolers and you'll have less restriction and better cooling.

The exhaust system is another good place to get power, bigger is better.

But even with IC/exhaust/intake modifications, you *still* wouldn't need to
touch the injectors.  I'd say that you could pick up 20HP if you were really
picky and worked at it.

Drastic changes would be:  compression change, bigger turbo, major intake
work, TB upgrade, and porting.

You would DEFINITELY need new injectors then.  But what's $200 for injectors
when you just dropped 4-5K doing the rest of the motor?

My original reply was accurate and truthful.  On a stock 1.8t, changing the
injectors will get you nowhere.  On a "bolt-on" 1.8t, it would still get you
nowhere.  It isn't until you upgrade the turbo and airflow capabilities of
the motor that you'd need bigger injectors.

--Perry

On Wed, Feb 12, 2003 at 06:45:36PM -0500, Scott F. Williams wrote:
> Perry, what exactly do you mean by your statement:
> "Changing the injectors will get you nowhere without drastically changing
> all of the motor."
> 
> Revamping the 1.8T top to bottom is not necessary to realize gains with
> bigger fuel injectors. Rather, it (like any other motor) will need more fuel
> once the dutycycle of the stock injectors is pushed beyond a safe point like
> 85%. The 1.8T seems to have an astonishingly low brake specific fuel
> consumption, but that doesn't mean that it can outright defy the laws of
> chemistry and physics.
> 
> If your logic were solid, the factory wouldn't install bigger injectors in
> the 150, 180, and 225hp versions. The substantial difference between the
> factory 150/180hp and 225hp variants is the turbo -a KKK K03 versus the
> K04 -and engine management. Naturally, hotrodding the engine by oneself will
> involve similar mods to the factory route and will certainly necessitate
> injector upgrades after a point. This is all basic knowledge.
> 
> So, I must be missing some more erudite point of yours. Please elaborate on
> what you're *really* saying.
> --
> Scott F. Williams
> NJ Scirocco nut
> '99 Subaru Impreza 2.5 RS
> Mazda 323 GTX turbo "assaulted" vehicle
> Golf GTI 16v "rollycar"
> ClubVAC: "Roads found. Drivers wanted."

-- 
Perry Harrington			Data Acquisition & Instrumentation, Inc	
perry at dainst dot com					 http://www.dainst.com/

Those who would give up essential liberty to purchase a little temporary safety
deserve neither liberty or safety. Nor, are they likely to end up with either.
                             -- Benjamin Franklin

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