VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: 92Wolfsburg on October 26, 2007, 06:34:37 pm
-
Hi all, I just bought a 96 AAZ Jetta and plan to put some serious miles on it. It has 240,000kms on it, is in really nice shape and seems to be well maintained. On my drive from Toronto to Thunder bay, I averaged 5.6L/100km or 42mpg (US) - thirstier than the 92 Wolfie. Understandable seeing as its a bigger engine and has air conditioning and power steering. The car is probably heavier too.
90% of my driving will be on the hills and twisties of the north shore of lake superior.
Other than the usual wheel bearings and tire pressures and not driving like I stole it and stuff, what can be done to improve the fuel economy? Most of the threads I've read dealing with turbo/inj. pump mods are focused on increasing power not increasing fuel economy, although I'm sure some of the mods will accomplish both.
I do not have to worry about sniff tests where I live, but I dont want to do any mods that will effect reliability/durability of the engine.
Fuel: I currently run Huskey DieselMax with 1-2oz of Power Service fuel conditioner per tank. Anything else I can do with the fuel to improve economy?
Tires: Will be purchasing new winter tires soon and plan to go with the narrower 185/60/14 instead of 195/60/14. Narrower tires = less resistance = better fuel mileage right? For summer tires I plan to get hard compound touring tires.
Turbo: I can't even hear it spool up on this thing! On the MKII you can tell when the turbo is performing. Will increasing boost increase fuel economy or will it just suck more fuel in?
Intercooler: Has anybody noticed a difference in mileage after installing one?
RPMs: 105km/h in fifth is roughly 2700rpm. If i put taller tires on the front, say...185/70/14 the rpms should drop a bit. This may work in my favour on the straights but will it work against me when going uphill? Too much load on the engine?
Fuel Pump: I probably wont touch the pump for a while but I'm sure theres many things than can be done here.
Again, I'm not looking for any more power out of this thing, I'd just like for it to be as efficient as it can be.
Oh, and I run Castrol Syntec 5W40 for VW Diesels, with a fresh air filter every two oil changes and a fresh fuel filter yearly.
What have you done to improve your fuel economy?
Thanks for any input!
-
lots of air in the tires, make sure your car is as light as possible, no dead bodies in the trunk haha, clean injectors, lots of air flow in and big straight pipe out the back! the intercooler helps a little too. just keep your foot out of it. good luck!
-
big bumper mk2's for life!
-
Yeah I guess I could pull the cat out eh...
Will MKII downpipe/exhaust components work on a MKIII?
Oh, and can the injectors be shimmed for economy or is the best economy reached with clean stock ones?
-
In short the answer is no :wink:
-
I remember reading here that a lower breaking pressure- somewhere in the mid to upper 140's had a benificial effect on performance and economy. Timing would have to be adjusted . It's in here somewhere. Perhaps someone else can chime in who read it.
Jim
-
How 'bout the tires? Anyone notice a difference after going to taller tires?
-
Get some rebuilt injectors with a breaking pressure of 130bar and set timing to 1.05. That should increase mileage a bit without any loss of power. The lower breaking pressure makes for less pumping losses and there is no hard evidence that the lower breaking pressure means less vaporisation when injecting.
You could also add some undercarriage cladding to decrease drag. I read an article about a guy who added plastic sheets under the car where the engine is and got something like a 10% increase in mileage. I think it's worth trying.
Edit: Found some interesting articles.
Part 1
http://autospeed.com/cms/A_2455/article.html
Part 2
http://autospeed.com/cms/A_2456/article.html
-
the bigger the tires and wheels the better, i run some 14" teardrops and thin and tall tires like you said. It would probably be better to have bigger, lighter wheels and shorter sidewall tires to look cool and make the engine turn slower...
-
Well, bigger is not always better. Say you put a set of 22" rims on, your rotational inertia and mass would be so high that you couldn't accelerate. This is one big reason that some of the ricers that sound so fast and have huge rims can't actually pass anyone. I remember one test in a magazine (I believe Sport Compact Car) where they dropped quarter mile times substantially by removing their aftermarket "dubs" and installing the stock rims. Unsprung weight is a problem as well for handling. You need to look at the type of driving you do. If you do long steady state runs, you can get away with a larger set of tires/wheels. The flywheel effect won't really hurt you all that much. If you are constantly accelerating and decelerating, get the lightest tire/rim combination you can find. The closer to the hub the weight is, the more you can get away with. If you're going to extremes, weigh the tires you are considering before you mount them. The less weight you have to the outside of the tire diameter, the better your acceleration will be. (Your brakes will also spend less effort slowing the wheels and more slowing your car.) For optimum fuel mileage, you want your engine to be in it's most efficient range for as long as possible.
I tried a set of 195/70-13's on the front of my 1.6 NA Golf instead of the 175/70-13's, and there seemed to be a slight increase in fuel mileage, but nothing I could quantify with complete certainty. The difference (about 1-1.5 mpg IMP) was small enough that it could have been due to other factors.
-
i was assuming of course that no one puts dubs on their dub! i personally wouldnt go any bigger than 15's or 16's because of acceleration loss like you said.
-
Nice posts, I'll try the 130 injectors for sure.
This car (96 AAZ) actually has a big plastic shroud that covers the engine from underneath. It keeps everything nice and clean, but its a PITA when it comes time do do the oil filter!
In the summer I think I'll try a set of 195/70/14...so another 10% taller. I'm sure the narrower 185 tires would be better on fuel but if I'm increasing the diameter I should also increase the width to keep handling somewhat normal.
-
Actually, the skinnier tire will help you in the snow. But stay away from the steel wheel to reduce the unsprung weight. Find some aluminum or aluminum/magnesium "dingers" that still balance well and seal the tire normally at a garage sale or some such. Added up over 4 wheels and you can save pounds depending on what you get. That also translates into longer lasting brakes...
Andy
-
You can get 4x100 15" Steelies from Impex http://worldimpex.com/parts/genuine-part-wheel-disc_54110.html Corrado Steelies $70 each.
Details and pics Here, http://forums.tdiclub.com/showthread.php?t=151192[/url]
-
Just looked at my car, dont think the 195/70/14s will go. I'm planning on buying my snows from here http://www.discounttiredirect.com/direct/findTireDetail.do?c=2&sw=true&cs=185&pc=11206&rd=14&ar=70 but I wanna make sure they'll fit without rubbing first.
Anybody running 185/70/14's on a MKIII? Hows the clearence?
Anybody running any larger than normal tires? If so what size? I'll do the math to see what the diameter is.
I wish they made these tires in a 185/65/14!
Thanks for the input.
-
Actually, the skinnier tire will help you in the snow.
Interesting. That's the second time I've heard that, but it sounds counter-intuitive. Wider tires = more contact patch = more traction in snow, no? Please explain, I'm curious now. :)
Thanks,
-
i believe it has to do with 'cutting' through the snow. the wider tire surface will spread the weight of the car out on the surface giving you less psi which means less grip. skinnier tires will sink easier in snow.
but if you buy a really good snow tire, the actual size shouldn't really matter much. you will notice that snow tires have large spaces between the treads to allow snow to compact in those areas, which then allows the rubber to get something to grip on (if the snow isn't too deep of course)
the problem with winter tires is that they wear much quicker due to the fact that the treads are more spread out, and give poorer mileage as well. a trade off for safety of course.
anyone with a better explanation feel free to take a crack at it! :)
-
You're right about cutting through the snow. Think of it this way, if your tires are 10" wide, and you are going through 5" of snow, not all of that snow can be compacted into the spaces in the treads. If you walk beside a car that is driving (slowly) through deep snow, you will see that some snow gets pushed out to the side. If your tires were only 5" wide, a higher percentage of the snow under your tire could be pushed to the side, and your tires have a better chance of getting to pavement (gravel, whatever). One thing I have been told and believe from my own experience is that this matters more if you have slush at the base of the snow. If you have no slush between the road and the snow, the snow that compacts into the tire treads actually helps grip the snow under your tires and increases traction.
-
Thanks for the explanation guys. Now I feel better about going from 165 wide tires to 155 to improve fuel economy... I was worried they would be like ice skates in the winter. ;)
-
Thanks for the explanation guys. Now I feel better about going from 165 wide tires to 155 to improve fuel economy... I was worried they would be like ice skates in the winter. ;)
I've got 155/70/13 snow tires and they are good, it's a nice size.
-
Well I'm going from a 205/40r17 to a 185/65r15 for snow tires.
This is on my mk3 gasser, I have 205/60r14's on my mk2.
Still getting close to 35 on the gasser with the 17's.
Cool thing is all the wheels I have will fit either car.
dan
-
Dan: Any clearance issues with the larger tires on your MK III?
-
Where I grew up summer was three months of bad skiing. Of course, that was before the new technology rubber compounds came about...but those are only really good for ice contact. Back in '96 I bought a '92 Golf NA that came with Hallipalitta (sp?) snow tires. They were incredible, especially on ice...but VERY soft compound. Wore out right quick.
One thing to keep in mind though, if you go with a skinnier tire and there is enough snow on your roads to "rut" the road....your car will follow them like mad.
-
There are test made by ITAQ saying that the Jetta save 14% on Fuel using the DBF-4 from PROLAB-Technologies. It's the best on the market, also if you never want to have any problems with the whole fuel system. It cleans, lubricates the pump, eliminate water and it's not "oil base" so, environment friendly and it burns clean and biodegradable. At only 20$ for 1L that treats 2000L... .01$/L of fuel, it's definitly the cheapest also!
The website:
http://www.prolab-technologies.com/contenu/produitsAutoDetail_ang.cfm?noFicheProduit=135
Have a look at the tests:
http://www.prolab-technologies.com/multimedia_ang.htm
-
What a suprise, all 3 of your posts say the same thing. Shocking. Post to post salesman? :P