2003 VW Passat GLS (1.8T 5-sp manual)

[musasabi]

Hello everyone. =) This is my first post; I'm posting here because I've actually got a specific question in addition to my general introduction. Hope that's alright, mods.

In any case, I drive an '03 Passat 1.8T. It's a 20v engine running a K03 turbo at 15psi. It's running around twice the stock boost due to the ECM flash I've got. All told, my engine made ~150bhp stock, and is now making ~205bhp (or so APR claims).

My EPA estimates are 18/28, and I regularly exceed just by short shifting, staying off the throttle, engine braking, and avoiding full stops. And, despite what one might think, I very rarely get honked at by my fellow Chicagoans for getting off the line so slowly.

In any case, my specific question is this: A friend of mine has been utilizing this forum and getting great mileage in his Civic (of course). He stated the most efficient point of power deliever for "most" engines is 80% throttle at 2200rpm. But... What about a turbo charged engine? Particularly one running 15psi (with the fuel map to match, obviously)? Conventional wisdom tells me that if I hear the turbo spooling, I've given it too much gas to remain efficient. And, at 80% throttle, it'll spool every time by 2200rpm. Not to full boost, obviously, but the K03 is a little turbo, so it doesn't take much. So, is the efficiency point for a turbo gas engine different than an N/A engine?

Plus, if anyone has any advice from their experience with hypermiling a turbocharged car, please feel free to share. =)

Thanks in advance, everyone.

[Tango Charlie]

I have absolutely no experience with turbocharged cars, so unfortunately I cannot weigh in on that, but
Welcome to Ecomodder!

[mwebb]

the AEB engine was about 150hp but those were not used after about 1999 ,
your engine AWM is good for about 180 hp stock and about 1 bar of boost , stock 1 bar = about 14.7 psi

so
for better FE , why not re install the original software ? your tampered with software is probably not an improvement in anything anyway .

if you have not replaced the timing belt
do it yesterday , when the belt breaks the engine becomes a boat anchor .

never use any oil that is lesser than VW spec 502 , 504 is much better , do not attempt to save money on oil quality

you may be able to use 87 octane top tier fuel
IF you are not driving at WOT , ever . FE may go down due to knock correction ... or not depending on how aggressively you drive

grille block

[musasabi]

Ah, you bring up a good point. But there are some details that differ from your post. =)

First, my engine has an AWT head. The VAGCOM still reads it as AWM software, but either way, my engine is weird. Given that it could actually be either (AEB/AWM) since the AWT was never used in the US, but it's in the AEB family, I just assume the lower power rating to avoid bragging.

Either way, though, the AEB's only run .6 bar and the AWM's only run .8 bar, on stock longitudinal Passats. APR's ECU has me at 1 bar, though, yes.

Also, the timing belt has been changed at 70k and 140k, and I'm presently at 145. =) No worries there. Plus, if it is and AWM, they updated the timing belt so breakage was far less likely, as well as improved the water pump so it didn't destroy the impeller. Even still, I keep a regular eye on my timing belt.

Oil is always fully synthetic, but I hadn't done the research to see which manufacturers had VW approved oil. Thank you.

I like my car because it allows me decent fuel economy while also being fun. That said, I generally go WOT about once per tank, given the right circumstances. So, lower octane fuel would be dangerous. =)

I will do research on the oil, though, as I'm ~500 miles away from my next change.

But I'm still curious about the driving mechanics, haha. Does spooling the turbo ruin fuel economy for pulse and glide and short shifting? Etc?

[bandit86]

I just sold my 98 passat 1.8t 5 speed. It got an easy 35 on the highway not drivin it like a grandma. Mine would coast for ever, the boost gauge showed screwy numbers, I think I was on a constant low boost - maybe faulty waste gate. 275,000kms and ran great but my exhaust manifold always glowed in the dark even when I drove it super easy and not use the turbo for 2 miles coasting home. (country road)

Mine had the mystery battery drain caused by the comfort module under drivers foot well that drove me nuts and sold the car

[mwebb]

the AEB has bolt down coils while the AWM family has push fit coils
the letter designation for the engine will be stamped on the lug / hook moulded / cast into the cylinder head by the Tbelt cover on original engines
replacement engines may be blank

VCDS will look at the VIN and pick the engine most of the time or pick from the label file if it can not get the VIN on early pre can cars , can began in earnest in 2001 in the Passat.

my Audi A4q with AEB does about 34 mpg at about 65 mph with AC on
my Passat ATQ does about 32 mpg same conditions

but mostly i use
the geo metro

[Ecky]

I have no experience with boosted motors either, but a motor is typically most efficient at 80% load, rather than 80% throttle. You can tell you're at full load when you reach the point that pressing the pedal further doesn't accelerate you faster (or not much anyway - most motors start to enrich the mixture at some point and you get a bit more oomph).

To my knowledge, a turbo can actually increase FE because the motor is running at a higher compression, the only thing you might be fighting are fuel maps. You could read up on "pulse and glide" in Driver's Ed and try a tank using boost + that driving method, and see if it dramatically affects mileage.

[RobbMeeX]

Generally, chips also increase timing across the board which should make for better mpg as well. I'd suggest staying out of boost and not worrying about loss of mpg with the chip.
P.S. I've been to APR.

[Ladogaboy]

Originally Posted by mwebb

so
for better FE , why not re install the original software ? your tampered with software is probably not an improvement in anything anyway .

I disagree with this. Stock performance tunes tend to improve performance/power by leaning out the AFR and increasing the timing, both of which help with fuel economy.

I'm in a similar situation to musasabi, and from my experience thus far, boost is generally bad for fuel economy. Part of the reason is as boost increases, the AFR will get richer, and you are tracking further away from stoich.

The 80% load might still be accurate; however, if you can get a map of your boost profile, you'll be able to tell what your rpm range is. For me, as long as I stay under 2,500-3,000 rpm, I'll be generating little to no boost even at 80-100% load.

[mwebb]

sorry
you are incorrect on all counts

on these systems timing is pushed against the knock sensors , and the system can control timing advance and retard on each cylinder at all loads and rpms , when the "tuners" advance the timing they are just forcing the system to run in knock retard much of the time assuming they have not defeated that function in their ignorance .
which kills engines

then we have the leaning out the AFR myth
only happens at cruise with light load , has no effect on overall performance and it is a "good "feature that should never be tampered with

AFR can change under boost
or not and does not always change on VW and AUDI
and
expect calculated load to get close to 200% with 1 bar of boost
or 150% with .5 bar of boost , 7.35 psi , more or less .

a quick and easy way to test your system unless the "tuners / tamperers" have defeated that function too
in their ignorance

Originally Posted by Ladogaboy

I disagree with this. Stock performance tunes tend to improve performance/power by leaning out the AFR and increasing the timing, both of which help with fuel economy.

I'm in a similar situation to musasabi, and from my experience thus far, boost is generally bad for fuel economy. Part of the reason is as boost increases, the AFR will get richer, and you are tracking further away from stoich.

The 80% load might still be accurate; however, if you can get a map of your boost profile, you'll be able to tell what your rpm range is. For me, as long as I stay under 2,500-3,000 rpm, I'll be generating little to no boost even at 80-100% load.