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Engine Specific Info and Questions => IDI Engine => Topic started by: cervelorod on November 06, 2011, 11:22:09 am
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I have a 1990 jetta IDI that seems to get much lower fuel mileage than I see others reporting. I consistently get 33-34mpg. I got that when it was NA, and now that I have added a turbo, I still get 33-34 mpg, although with a better grin factor. My engine has 195k on it, but it is solid. Very little blowby, starts well cold or hot, idles good, etc etc. I have some 17x6 wheels and tires on, but even on stock wheels and tires I get the same. I have it lowered about 1.5" and no brakes are sticking. I have max fuel turned up a bit with the turbo, but even straight hiway miles at 70-75 nets the same. Most of my driving is country 60-65.
Any ideas or is this were it stays??
Thanks,
Rod
1990 Jetta IDI Turbo
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I'm pretty sure for max fuel economy the driving speed is 90km/hr, or 55m/hr ish.. Maybe it's because of your speed.
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Does it get the same fuel economy with the fuel screw set at its normal position? I noticed a big drop in fuel economy with my fuel turned up a bit, even though my driving habbits were the same.
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I don't think I was getting any better when I first got it. I have no idea what the PO had done, but the collar was still on the fuel screw when I attacked it. I adjusted it while it was still NA, because I was not getting great fuel mileage anyways, and the power difference was very noticeable.
I think driving 55 on the Interstate here would get me a ticket... If max economy was at 55mph, I would hope that I could come close to that at 60-65, but I'm ~20% off.
I am timed at NA specs, 1.01, I've been to lazy to turn it back for the turbo.
Thanks!
Rod
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all things being equal, the 3 things i can figure will affect mileage is pump timing and internal pump pressure. But recently someone from this site who i know told me that he found some crud at the bottom of his fuel tank that must have been affecting his pump because once cleaned, his mileage went way up
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all things being equal, the 3 things i can figure will affect mileage is pump timing and internal pump pressure. But recently someone from this site who i know told me that he found some crud at the bottom of his fuel tank that must have been affecting his pump because once cleaned, his mileage went way up
Who'da thunk it. I changed my fuel filter, but never thought to clean the tank. I'm installing a veg oil conversion over the next few weeks, so I'll drop the OEM tank and see what I can find.
Thanks!
Rod
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x 2 on the internal pump pressure.
If your mileage is fair in town, but doesn't improve by more than a few mpg on a run, then lack of dynamic advance is a possibility.
General low compression will also contribute...
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My 1992 Ecodiesel (http://www.vwdiesel.net/forum/index.php?topic=8978.0) routinely gets 46-48 mpg combined city/hwy and has touched 50 mpg pure highway running 70 mph.
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I can achieve anywhere between 40-50mpg depending on how i am driving and the speed.
100km/h cruising for a tank (2450rpm for me) will net an easy high 40's.. but I rarely get to do that slow on the highway! LMAO 135-145km/h is more the mainstream.. 3300-3600rpm. and even then.. can stay above 40mpg.
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Is your odometer slipping?
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My best ever recorded mileage with Jezzie is only ~36 MPG - 6.5L/100km. She's a bit tired though, she burns about 1L of oil per 1200km or so.
Around town I often get more like 30 MPG - 8L/100km. :P
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In reality.. The ones claiming an easy 50mpg are probably not taking their readings right.. Fudging it a bit to look "superior".. And possibly just have a really tight motor in a very flat area, and it never has to work..
If you actually drive the bag off your car like I do.. Anything over 30mpg while having fun is a godsend to me :D
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I can pull 50, but it ain't easy, my motor is tired not tight, and it is flat here. My f250 mod set me back 2 mpg, and my odometer reads up to 3% high, which I proclaimed a while back.
Same as before, I essentially try not to hit the gas or the brake lol. And I can squeeze high 40's like this.
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Mileage claims based on one tank can vary substantially. (How do you know how full it was when you started the run and how do you know you filled to the exact same point?) I tracked my NA over the course of one year and 16,800 km. I averaged 42.17 mpg Imperial, and 36.71 mpg U.S. in that time (corrected for verified speedo error). Stock engine (as far as I know as it had over 250K on it when I bought the car) with 2.25" exhaust added to modified toilet bowl manifold. After I changed the exhaust I tended to beat on it. Note that I'm not sure what tranny I have but it's definitely geared substantially different than most diesel trannies.
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In my old 1.6na I regularly got around 5.5l/100kms with my best being 5.0/100 (uncorrected, maybe a 10% error IIRC). That engine was tired. It had less than 350psi in each cylinder and used about 1 liter/1000-1500kms. I wasn't easy on it, but I usually wasn't hard on it either. 91 Golf ftr
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I can pull 50, but it ain't easy, my motor is tired not tight, and it is flat here. My f250 mod set me back 2 mpg, and my odometer reads up to 3% high, which I proclaimed a while back.
Same as before, I essentially try not to hit the gas or the brake lol. And I can squeeze high 40's like this.
Well now that you have loaded the front end with lead it is going to be easy to exceed your average Fuelly. I had my car loaded down to within two hundred pounds of max gross last week on my run north. But it looks like I got great mileage. Over 300 miles on just over a half tank, maybe 2/3rds which is near the upper 40's. I will know the truth on Thursday when I do the refill at the same station thing. If the number is over 48 I am going to mark it up to one of three things, a. a new LeBra on the front, b. new wing window open on the drive up, c. a tightening of the OUT bolt to stop a weeping leak I didn't know was happening. By doing that I also picked up a pound or two at cruise on my IP pump.
You decide which is the correct answer to getting better mileage.
Even 45 MPG would be great considering I was nearly maxed out and doing 65-70 most of the way. It just ran nice and smooth.
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I can pull 50, but it ain't easy, my motor is tired not tight, and it is flat here. My f250 mod set me back 2 mpg, and my odometer reads up to 3% high, which I proclaimed a while back.
Same as before, I essentially try not to hit the gas or the brake lol. And I can squeeze high 40's like this.
What's a F250 mod?
I check per tank, but it has been 33-34 mpg since I purchased it 2 years ago. I drive it hard, use the throttle more like a switch than a variable resistor...
I have checked mine odometer via GPS with the same error your are seeing ~3% with my summer tires. It is worse with my winter tires.
Thanks,
Rod
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Someone else on here was having the same rotten mileage problem, can't remember if he solved it though.
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I can pull 50, but it ain't easy, my motor is tired not tight, and it is flat here. My f250 mod set me back 2 mpg, and my odometer reads up to 3% high, which I proclaimed a while back.
Same as before, I essentially try not to hit the gas or the brake lol. And I can squeeze high 40's like this.
What's a F250 mod?
I check per tank, but it has been 33-34 mpg since I purchased it 2 years ago. I drive it hard, use the throttle more like a switch than a variable resistor...
I have checked mine odometer via GPS with the same error your are seeing ~3% with my summer tires. It is worse with my winter tires.
Thanks,
Rod
My f250 mod was running the car with 2 truck batteries installed
My mpg is quickly sliding! 43.5 today! But I ran the piss out of it for about 80 miles so. I think I could have hit 45 hhad I not. 47 with 1 battery. But it's goin down!
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The F250 mod is not going to be in high demand here I can forsee that. Get ready for the cold weather and crappy mileage. I may have to drop the wax treatment sooner than later as the weatherman says colder and wetter for the PNW this year. I can't afford to be stranded in Portland with a plugged filter. So I am packing a spare.
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We've been below freezing at night for over a week now. Diesel prices jumped .10 - .20 two weeks ago, figured it was winter blend. Hooray higher prices and less btu's.... Cleaned my side of the garage so I could park inside too.
Rod
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yes i'm wondering if the weather/quality of fuel is having something to do with my mileage.
also, i stopped waxing (or any additives) about 3 tanks ago, so maybe that has played into it.
i had a dream i got rings for Christmas lol
in the spring i'm hopin to ring some pistons, and get my VNT on (with theman53's mount he fabbed me) and then we'll see what we can shake loose.
by the way, my car is freaking loud. OR Coaster (or anyone really) at 65+ is the engine just damn loud on yer car? i mean .. it's to the point wifey is now bringin the ear muffs she wears at the range for any highway travel she does with me. and i noticed i can still listen to rush limbaugh with the muffs on, so now i too am wearing them at all times.
what gives with that? why's the motor just make .. that much f'in noise??
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You have an exhaust leak. The motor itself does not make a lot of noise.. but the 23.5:1 combustion does ;)
Check it out, bet you'll find a hole somewhere in the tunnel.
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by the way, my car is freaking loud. OR Coaster (or anyone really) at 65+ is the engine just damn loud on yer car? i mean .. it's to the point wifey is now bringin the ear muffs she wears at the range for any highway travel she does with me. and i noticed i can still listen to rush limbaugh with the muffs on, so now i too am wearing them at all times.
what gives with that? why's the motor just make .. that much f'in noise??
Same here, I notice if I stop and my music is still playing I think "man that's loud", but it has to be to hear it over the engine, exhaust and studded tires...........and lots of rattles ;D.
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Not engine loud, nor road noise loud. Thanks to a healthy application of rubber in the doors, floors, and though out the back. Not a complaint there. I had a bit of an exhaust noise until I tore the pipes apart and reset them. I think the PO ran over something in the woods while fishing and just didn't care.
I do notice more road noise with the sunroof or the "wing", man I love them things, windows open but that is to be expected.
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Mileage claims based on one tank can vary substantially. (How do you know how full it was when you started the run and how do you know you filled to the exact same point?)
The proper way to do it is simple, if slow. You need to take the time and dribble fuel in at the end (after the pump shuts off) until you have nice green diesel right up to the top of the filler neck and then watch for a minute to make sure it does not go down. That way you KNOW the tank is full. Every time. I can get 3 more gallons in my 5000TD after the pump shuts off. I had a Ford Tempo diesel that would take another 6 gallons after the pump shut off. Rabbits will usually take another 1.5 gallons when the pump shuts off.
In case some of you haven't figured it out yet, foaming is the culprit. Different pumps and varying temps drastically effect how much fuel a tank will take before the pump shuts off. This is what causes most of the wild mileage claims. In a small tank just a gallon difference makes a huge difference in calculated mileage.
FWIW I have been tracking mileage in diesel Rabbits, Fords, Audis and Volvos that I have had my hands on since 1986 (yes, I am compulsive) and check mileage EVERY tank and on my Ranger TDs I plug the numbers into an Excell spread sheet, so I KNOW what kind of mileage my stuff gets. Any good diesel Rabbit should get 48 mpg combined if you drive it reasonably. I have owned over 2 dozen in the last couple of decades. If it won't, find out why. These cars get the big numbers by cruising in that "sweet spot" that uses almost no fuel. Pushing on the loud pedal mostly just makes more noise and eats fuel on a stocker. Me? I am cheap and don't mind driving like an old man (partly because I am), but mainly because it REALLY makes me smile to do the math on the back of the fuel receipt.
Caveat: All of my numbers come from pretty much stock rigs with cam and IP timing changes along with adjustments of the flow screw. If I do not have to part with the Audi I will start with the more esoteric upgrades like synthetic trans lubes, lowering and bigger exhaust. (Yes, straight up cam timing is not always the best)
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There is a spring loaded filler neck vent that you need to depress to let the air out and get more fuel in. Next time you fill up try this: when the filler neck is full, depress that vent and you'll hear a swoosh of air and the fuel level will drop, put more fuel in, then push the vent again and keep doing that until you get no more swoosh and the neck is full. It is also important to fill up at the same ambient and tank fuel temperature since fuel expands when heated. As you drive, the hot fuel returned to the tank heats the tank.
E.g. Immediately after you have driven straight for 500 miles, fuel temp in the tank is much higher than if you wait to let it cool off over night before you fill up. There will be a difference in how much fuel you can put in depending on tank temperature.
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Diesels do not have the flapper valve in the filler neck. That is an unleaded gas car feature to prevent using the old, larger, leaded gas nozzle into the filler neck. The flapper valve is supposed to make fueling with the wrong pump impossible. If I were you I would cut that entire restrictor out since it is not required on a diesel and really slows fill ups. Yours must be a conversion.
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Diesels do not have the flapper valve in the filler neck. That is an unleaded gas car feature to prevent using the old, larger, leaded gas nozzle into the filler neck. The flapper valve is supposed to make fueling with the wrong pump impossible. If I were you I would cut that entire restrictor out since it is not required on a diesel and really slows fill ups. Yours must be a conversion.
I think he's talkin' about that little "button" sticking into the neck a couple inches down.
My rabbit takes 2 gallons after the pump shuts off, sometimes it's 1.9 and sometimes 2.1 gallons more but it's very consistent. Yup, telling people about my "upper 40's" mileage is very fun........
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What vintage cars are we talking about? I have never seen any kind if spring loaded vent on any diesel VW that I have owned. Most of mine have been older stuff though.
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What vintage cars are we talking about? I have never seen any kind if spring loaded vent on any diesel VW that I have owned. Most of mine have been older stuff though.
MK2 gas and diesel afaik, I just checked my '92 golf diesel and it has it. It's just a little lever inside the neck towards the rear of the car that you push IN and it opens it.
I don't know about anything newer.
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I think you need to wax your car. Less wind resistance ::)
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I put a gauge on my IP this evening and I had 20 psi at about 1100 rpm. Guessing on the RPM part... I increased the pressure to 43 psi. I did only a short drive and didn't notice a difference in performance. I put my gps in the car and am going to check odometer and speedometer, also upgraded this week, then keep fuel economy and see if it makes a difference.
Rod