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GreenGLI

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Discussion starter · #1 ·
Fuel usage?

I know this site is more focused towards getting more power and performance out of VWs, but I wanted to kind of ask around and see what kind of mpg people with the 16v are getting.
I got my GLI by trading a VERY nice 86 F250 diesel supercab for it. My main motivation was that as a daily driver the F250 was only getting 14-15 mpg running on diesel that was costing me $3.50-$375 a gallon. Basically driving it was costing me $0.25 per mile just for fuel.
I expected to get 24-26 mpg with the GLI (revised EPA estimates) and with unleaded running $3.10-$3.20 a gallon in my area I was expecting to lower my commute costs to about $0.12-$0.13 a mile. Basically cutting my fuel cost in half.
When I got the VW it was running crappy and on my first tank or two it only got about 15-20 mpg. Part of that was due to a heavy right foot as I was playing around with it and feeling it out performance-wise. Since then I've gotten it tuned up and corrected a few other issues and now it is running very well. In the process we figured out that the cat has probably been gutted since it is still running a little rich (high HC) at idle.
This last tank of fuel I have intentionally been playing light foot on the go pedal just to see what kind of economy I can get out of it. I'm at around 190 miles on the trip meter and sitting between 1/4 and 3/8 of a tank left. Based on the previous two fillups, I'm expecting that when I fill it up on the way home today it will take 9-10 gallons - which calculates out to be somewhere around 20-21 mpg.
My question is, IS THAT THE BEST I CAN EXPECT?!? When I say I have been light-footing it I mean a REALLY light foot. Like keeping the RPMs below 3500 ALL the time and 98% of the time below 3000, and 75% of the time below 2500 RPMs. I'm hardly ever even touching the real power band of the engine.
So am I gonna' have to dog this thing around and drive it like a granny all the time to get decent mileage, or does it sound like there is still something wrong (like a bad O2 sensor maybe) that is keeping me from getting better mileage? What kind of mpg are other people getting?



Modified by GreenGLI at 3:20 PM 12-14-2007
 
Discussion starter · #3 ·
Re: Fuel economy? (vwsquirrel)

Quote, originally posted by vwsquirrel »
I get 30 + on the hwy 25 or so in the city and thats normal driving. I believe you should be getting better mpg. This is a 1.8 16v scirocco.

I sure wouldn't think the difference between your 1.8 16v Scirocco and my 2.0 16v GLI would be that much - maybe 1-2 mpg at most due to the larger displacment and (maybe) heavier body....
Anybody with a 2.0 16v GLI care to chime in?


Modified by GreenGLI at 8:39 PM 12-14-2007
 
Discussion starter · #6 ·
Re: Fuel economy? (PASHAT)

Quote, originally posted by PASHAT »
I was getting 30mpg in my 2.0l Passat, driving normally. Of course, we have bigger gallons....

Well, by my calculations that is still right at 25 mpg US
Quote, originally posted by PASHAT »
Brakes dragging?

Doubtful. They aren't getting hot or smoking or anything.
Quote, originally posted by PASHAT »
Air filter clean?

Cleaning and re-oiling it tomorrow (K&N panel filter)
Quote, originally posted by PASHAT »
What spark plugs you using?

The Bosch non-platinums with the 4 electrodes (can't remember what they call them or the part number). They're the ones my buddy at All European Autowerk recommended...
I'm thinking O2 sensor maybe?


Modified by GreenGLI at 8:33 PM 12-14-2007
 
#7 ·
Re: Fuel economy? (GreenGLI)

Quote, originally posted by GreenGLI »

Doubtful. They aren't getting hot or smoking or anything.

Better to spin them when the wheels are up. Tiny drag makes a big difference.
I think that there were some Bosch plugs that people really didn't like, and I think it might be those four prong ones. Do a search on this thread on spark plug in the title/archived. Might find out something useful.
I am pretty sure that I was getting that mileage with a bad 02 sensor....I didn't change it until just before I sold it. Make sure that DPR signal is dead on....2.5 and fluctuating.
It is the 02 sensor that causes the fluctuation, so if your DPR signal is fluctuating, your 02 sensor isn't shot....might not be working perfectly though.
Make sure your timing is dead on, as well. And these VWs are high compression, so you really should use high octane....93 likely for you. (But, to be honest...I didn't)

Put a can of seafoam through the tank.


Modified by PASHAT at 9:09 PM 12-14-2007
 
#8 ·
Re: Fuel usage? (GreenGLI)

Quote, originally posted by GreenGLI »

Since then I've gotten it tuned up and corrected a few other issues

Understatement....somewhat humourous!
Oh...and fill it ALL the way up. Then drive it and fill it ALL the way up again....those fuel gauges are not all THAT accurate.
It will make you feel better to know that my Chevy Truck is getting 25 cents per KILOMETER!
 
Discussion starter · #9 ·
Re: Fuel economy? (PASHAT)

Quote, originally posted by PASHAT »
Better to spin them when the wheels are up. Tiny drag makes a big difference.

I'll try that - though I sure can't see any drag insignificant enough to not cause any heating/smell/smoking being significant enough to knock the gas mileage down 5 mpg or more
Quote, originally posted by PASHAT »
I think that there were some Bosch plugs that people really didn't like, and I think it might be those four prong ones. Do a search on this thread on spark plug in the title/archived. Might find out something useful.

Found 1 thread specifically about the 4-prong plugs. Everybody seemed to agree that the 4-prong were no better than the OEMs - but nobody seemed to think they were any worse either - at least not in a non-turbo motor. The majority concensus seems to be that plats in the water cooled VWs pretty much suck. That seems odd to me considering that Bosch was the first to make plats and they're such a major player in the German car market. WEIRD!
Quote, originally posted by PASHAT »
I am pretty sure that I was getting that mileage with a bad 02 sensor....I didn't change it until just before I sold it. Make sure that DPR signal is dead on....2.5 and fluctuating.
It is the 02 sensor that causes the fluctuation, so if your DPR signal is fluctuating, your 02 sensor isn't shot....might not be working perfectly though.

Still haven't measured that since we got the DPR working again - though it was adjusted to get the lowest possible HC reading at idle. Based on that I'd expect it to be pretty close. I'll go ahead and put a meter on it tomorrow though just to see.
Quote, originally posted by PASHAT »
Make sure your timing is dead on, as well. And these VWs are high compression, so you really should use high octane....93 likely for you. (But, to be honest...I didn't)

Yeah, I know its still timed a bit fast, but again, old school says setting the timing as fast as possible without causing knocking gives the most pep and best economy.
My rule of thumb on the higher octane is that if it ain't knockin' on regular don't waste the money on high-test. I know that's pretty old-school thinking what with modern engines having knock sensors and all, but it has worked for me all these years. Sounds like it wors pretty well for you too....
Quote, originally posted by PASHAT »
Put a can of seafoam through the tank.

To clean the injectors and fuel system? Aren't there better addatives specifically designed for that purpose?
Quote, originally posted by PASHAT »
Understatement....somewhat humourous!

Yeah, I'm a master of understatement - I figured you'd read this and find that amusing
Quote, originally posted by PASHAT »
Oh...and fill it ALL the way up. Then drive it and fill it ALL the way up again

Excuse me..., but...., well...., DUH!
Image
There isn't any other way I know of to accurately calculate your gas mileage. I'm even anal enough about it to fill it exactly the same WAY every time (let it run 'til it shuts off automatically, wait 5 seconds, squeeze the lever until it shuts off again, and repeat the process ONCE more, but ONLY once more).
I think I'm consistently getting it completely full every time.
Quote, originally posted by PASHAT »
....those fuel gauges are not all THAT accurate.

LOL! And you laugh at ME for making understatements! 100 miles on the first 1/4 tank, about 60 on the next 1/4, and about 30 on the next 1/4. That's lacking just a little bit in the accuracy department I'd say (more understatement humor)....
Quote, originally posted by PASHAT »
It will make you feel better to know that my Chevy Truck is getting 25 cents per KILOMETER!

Yeah, well, that's 'cause its a gasser - AND a bowtie. If it was a diesel it would only be costing you about about 60% of that - around 15 cents per km.
And to think you were actually ranking on my old Fords in that OTHER thread.....
Image



Modified by GreenGLI at 9:56 PM 12-14-2007
 
#10 ·
Re: Fuel economy? (GreenGLI)

Quote, originally posted by GreenGLI »

Yeah, I know its still timed a bit fast, but again, old school says setting the timing as fast as possible without causing knocking gives the most pep and best economy.

DON'T do this. This ain't your ford! Motronic will try to set it back to where it should be.
Seafoam is pretty well respected on this forum. Seems to work well.
Get everything set to stock settings, and try a tank of premium. I know that some people have gas that they like on your side of the border, but I don't know the brands down there. Up here, it would be Shell Gold....
 
#12 ·
Re: Fuel economy? (GreenGLI)

how much highway vs city driving(sitting driving) are you doing? The normal stop&go stuff will kill mpg, but the really bad stop....& go will really kill it. Just looking at you're location says you may be in the really slow stuff.
 
Discussion starter · #13 ·
Re: Fuel economy? (ps2375)

Quote, originally posted by ps2375 »
how much highway vs city driving(sitting driving) are you doing? The normal stop&go stuff will kill mpg, but the really bad stop....& go will really kill it. Just looking at you're location says you may be in the really slow stuff.

Most of my driving is back & forth from home to the office. Its about 20 miles each way and about 15 miles of it is highway. BUT the trip takes anywhere from 40-60 minutes due to traffic. Not much actual stop and go, but a lot of rolling slowdowns and an average speed between 20 & 30 mph.
So far I haven't had a chance to get 'er out on the highway and run for any real distance - not more than 10 or 15 miles at a time so far. Now I know that these aren't exactly idea gas mileage conditions, but they are pretty normal "city" driving....
 
#14 ·
Re: Fuel economy? (GreenGLI)

That does sound like some pretty slow commutting, but 21mpg does sound a little low too. Not having tuned your version of CIS, I can't give any real good advice, except maybe get a Bently manual and get the DPR and timing settings as close to stock and start from there. You already have a couple of people in this thread that I would say know a good amout about tuning your setup, so you can't go too far wrong following their advice. http://****************.com/smile/emthup.gif
 
Discussion starter · #16 ·
Well, the weather here has been absolutely CRAP this weekend, so all I was able to get done was swap out a balljoint that was popping. I remembered that the ECU I was using is the "performance chipped" ECU (according the the PO) and swapped in the stock one that I had. Think I'll run it using that one for a tank full or so and see if that changes anything. Hopefully the weather will be better next weekend.
BTW, PASHAT, I have verified that the stock 16v ECU can be "chipped". Techtonics Tuning and GIACK both make a chip with remapped timing and fuel curves for it. Don't know for sure if mine really has a chip in it or not, but now that I have it out I'll crack the case and find out....


Modified by GreenGLI at 3:10 PM 12-16-2007
 
#17 ·
Re: (GreenGLI)

Quote, originally posted by GreenGLI »

BTW, PASHAT, I have verified that the stock 16v ECU can be "chipped". Techtonics Tuning and GIACK both make a chip with remapped timing and fuel curves for it. Don't know for sure if mine really has a chip in it or not, but now that I have it out I'll crack the case and find out....

I thought those chips were external.....But heck, I don't know much about non stock systems. Crack open an ECU? You have more guts than I have!
Good plan....return everything to stock. Then test from that baseline. Get your DPR right, and your timing right. Make sure your air filter are clean and no vacuum leaks. Put a can of seafoam through it.
I am still not sure I like Bosch plugs.....
 
Discussion starter · #18 ·
Re: (PASHAT)

Quote, originally posted by PASHAT »

I thought those chips were external.....But heck, I don't know much about non stock systems. Crack open an ECU? You have more guts than I have!

Well, I'm a computer engineer (a.k.a. geek) so opening one up doesn't scare me. It is only 4 torx screws to remove the internals from the cover - not a big deal at all. Just want to m ake sure to wear a grounding strap so you don't accidentally "zap" something inside.
Quote, originally posted by PASHAT »
Good plan....return everything to stock. Then test from that baseline. Get your DPR right, and your timing right. Make sure your air filter are clean and no vacuum leaks. Put a can of seafoam through it.

I'm starting with going back to the stock ECU, and I'll go from there. I already know where to get some seafoam, too.
Quote, originally posted by PASHAT »
I am still not sure I like Bosch plugs.....

I haven't ever had problems with them in the past. I think it's pretty much like the oil brands question. Everybody has their favorite and their "never in my car" brand. I know my buddy does a lot of tune ups on VWs, Audis, BMWs, and MBs. Figure if he recommends 'em they must be OK - he knew that the plats weren't the best choice - which is more than I knew (and seems totally counter-intuitive to me).



Modified by GreenGLI at 6:48 PM 12-16-2007
 
#19 ·
Re: (GreenGLI)

i get 29-35 highway thats at speeds between 65-90+mph on and off the throttle,maybe closer to about 20-22 city not real heavy footed from light to light--but backroads can get a little crazy!!!mine is a 9a(2.0l)16v----no a/c no p/s.port and polish,cams,chip,header,no cat,o2j trans ,and lots of other non powertrain stuff,daily driven,driven hard--but very well maintained---i run 93octane-i get better mpg with that than 87,89,91---burns better,less carbon buildup,no spark knock,----usually on a 10-11gallon fill up i'll get between 325-390miles till the next depending on my driving habits etc.......
if you're all tuned up and the car is running properly,and the air pressure isnt set at 10psi in your tires---try runnin a tank or two of 89octane or 91--you might actually see an increase in mpg--is your timing set right,is it cis-e?--if so is the co% set too rich?what brand gas do you use and what brand tune up parts--all will play a big role in overall mpg>>>>>> http://****************.com/smile/emthup.gif
Image
 
Discussion starter · #20 ·
Re: (deeeGLI)

Quote, originally posted by deeeGLI »
if you're all tuned up and the car is running properly,and the air pressure isnt set at 10psi in your tires---try runnin a tank or two of 89octane or 91--you might actually see an increase in mpg--is your timing set right,is it cis-e?--if so is the co% set too rich?what brand gas do you use and what brand tune up parts--all will play a big role in overall mpg>>>>>> http://****************.com/smile/emthup.gif
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All tune up parts are brand new and all Bosch.
Yes it is CIS-E, though I have also seen it referred to as CIS-M (Motronic).
Timing is set at least a little fast I believe. I've seen reference to 6* BTDC as the correct setting, but no one has said at exactly what RPM it should be set 6* BTDC...
Not quite sure what you are referring to when you say "is the co% set too rich?". Exactly what adjustment are you talking about and how do I check it?
 
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