Modifications to improve MPG

[superfinch]

Can anyone recommend modifications to improve MPG? Chip sets, air filter, exhaust, etc.... VW approved, endorsed or otherwise. Just picked up a 2001 5 speed with 48K miles and are posting low 40s for MPG. Am hoping to get in the 50s for MPG.

Thank you!

[CoriBug]

Check out Fred's TDI Page. TDIClub.com. VW TDI Enthusiast Community. There's another thread here with virtually the same discussion.My MPG seems LOW...

[superfinch]

Thanks for the link to Fred's. We do have a new fuel filter in and hope that helps.

[DZLBUG]

Ventectomy, right foot mod, keeping tires fully inflated and just keeping maintenance up to date. TONS of info on TDIclub.

Leave the air filter alone. Exhaust mods will not help. Tuning (Rocketchip, Aligator) can help, but only if you're not overusing the increased power.

[kcfoxie]

Let me explain some things others have said.

Ventectomy: this does not improve fuel economy, it extends your range. There is a small release valve to the left inside of the filler neck. Fill the car till it clicks off. Keep filling till you see foamy fuel in the filler neck. Use the pump nozzle to hit that valve and listen for the air to vent and the fuel to drop. You'll do this a few times before the vent is fully vented, you get about 1.5 or so extra gallons in their, this is how most people get into the 700+ mile range "club."

Right foot mod: keep the RPMs under 2700 religiously and shift early.

Tire inflation: Big one, also a huge debate. I tend to run 38-40psi year round, 40-42psi on good tires with longer life tred and ratings for higher PSIs. Less rolling resistance = more MPGs.

Intake/Exhaust: I personally don't like the airbox setup on the NB. I intend to put a CAI ("Cold" air intake) into the vehicle for several purposes; primarily turbos work to take hot air, cool and compress it, and deliver it to the engine. The hotter the ambient air the more effective they work, part of the massive FE loss in winter is the cold air temps. PLENTY of TDIClub members sport "winter bras" that fully cover and prohibit the grille from getting contact with cold air to force the engine-heated bay-area air to be sucked up and used. I can personally attest that this increased my mpg by 3mpg over a 700 mile trip, taking the same route, using the bra on the trip in and not on the trip out. My times were nearly the same (give or take 15 mins) but the FE Difference: barely 43mpg return vs almost 47mpg coming in. The temps were in the 20s the entire time of this test.
so...based on this I personally like the CAI, as it removes the need to put a bra on the car later on. Tho, the Beetle seems to have less an issue with this due to it's design than the Golf and Jetta (my test was done in my Jetta).

Exhaust: less restriction, the better. But it won't improve things a lot, at best 1.5 to 2MPG. At best.

Tunes: Software tunes unlock power and can unloack FE, depending on how you drive. Notice the trend here? It's how you drive. If you feel the car has poor passing power, any tune (RocketChip and Alligator are the two older TDIClub tuners, there is also KERMA, Unitronic, REVO and BullyDog that make software or piggyback harnesses for TDIs. I'd only go with an ODBII-based reflash system and NOT a piggyback connector like BullyDog).

Ensuring your car is aligned also helps fuel economy.

In my Beetle I've been running no faster than 70, and I've only had it two weeks and one full fill, but I got 43MPG with it. Winter time fuel has more kerosene (to act as an antigel agent) and thus we have less fuel economy, plus the cold air temps, etc...

Pick and chose and experiment ... find what works for you. A lot of the TDIClub members speak of things as if they are set in stone or are the Bible, but really, the only advise I'd say is that solid is: DO NOT USE STRAIGHT VEGETABLE OIL IN YOUR VEHICLE, for many reasons but most notably is that no TDI is really setup to handle the viscosity of raw veggie oil, and you're going to end up spending more in oil changes and repairs than saving any real money using diesel fuel or supporting a local biodiesel producer. (However a secondary 'grease tank' plumbed into your vehicle for an additional 12 gallons of diesel fuel is something I'm looking at myself).

[FarrisK]

Originally Posted by kcfoxie

Intake/Exhaust: I personally don't like the airbox setup on the NB. I intend to put a CAI ("Cold" air intake) into the vehicle for several purposes; primarily turbos work to take hot air, cool and compress it, and deliver it to the engine. The hotter the ambient air the more effective they work, part of the massive FE loss in winter is the cold air temps.

You have that backwards. Turbos like to take COOL air, and by compressing it the air gets WARMER due to the laws of thermodynamics. This is why we have an interCOOLer, which cools the air back down before it hits the engine.

The reason MPG takes a hit in the winter is because the stations add anti-gelling additives to the fuel, which reduces it's energy density (depending on your location).

[MichelleRoze]

Originally Posted by DZLBUG

Ventectomy, right foot mod, keeping tires fully inflated and just keeping maintenance up to date. TONS of info on TDIclub.

Leave the air filter alone. Exhaust mods will not help. Tuning (Rocketchip, Aligator) can help, but only if you're not overusing the increased power.

HaHa! Right foot mod. Yup Love that one. That's probably my biggest issue. Though I've found so far with my Auto that if you set it to "economy mode" not "sport mode" and don't allow the tranny to automatically change, I've increased mpg quite a bit! from 34-36 to now 38-40 ... same traffic, same location, same driving. I was told "eco mode" makes the auto tranny shift sooner and stay in lower RPMs. Not 100% sure on that. Plus I've also modded my right foot a tad since I'm leary about the condition of my tranny at 140K...

[kcfoxie]

Originally Posted by FarrisK

You have that backwards. Turbos like to take COOL air, and by compressing it the air gets WARMER due to the laws of thermodynamics. This is why we have an interCOOLer, which cools the air back down before it hits the engine.

The reason MPG takes a hit in the winter is because the stations add anti-gelling additives to the fuel, which reduces it's energy density (depending on your location).

So how does one explain the heat trapping bras for the winter? Too cold or too hot = not very effective? Trying to strike a balance?

I've seen the on more than just TDIs, I've seen SEMIs with them so I believe that they do make an improvement in the vehicle operation.
Regardless I like the vehicle to sound throaty, the airbox is coming out.

[FarrisK]

Originally Posted by kcfoxie

So how does one explain the heat trapping bras for the winter? Too cold or too hot = not very effective? Trying to strike a balance?

I've seen the on more than just TDIs, I've seen SEMIs with them so I believe that they do make an improvement in the vehicle operation.
Regardless I like the vehicle to sound throaty, the airbox is coming out.

It has nothing to do with intake temperatures. It blocks the radiator, which lets the engine coolant warm up faster. Diesel engines take longer to warm up than gassers, and when engines are cold they go through a lot more strain, wear and tear, and probably get a bit worse mileage. Once the engine is warm however, the mileage difference pretty much disappears.

[kcfoxie]

the more you know!

[DZLBUG]

Regarding the ventectomy, it extends range AND makes your MPG calc's more accurate because you can always fill it to the same level so you always know how much you are using. Your MPG calc's could be off as much as 2-3 mpg depending on what level you are filling the tank to. By modifying the vent mechanism in the tank you can fill the tank to the brim. Note that this mod should only be performed on diesel vehicles due to the lower volatility of diesel fuel. A plump full vented tank of gasoline could equal BIG BOOM.

Be careful with the right foot mod. Babying a TDI 100% of the time is not good. Let it rev out to redline at least once or twice a day to keep things clean and moving properly in the turbocharger and related plumbing. Failure to do so can result in soot clogged VNT mechanism in the turbo which can cause overboost/underboost, limp mode and drivability problems.

Install a WAI (warm air intake) if you must, just stay away from the oiled filter elements. There are a number of excellent dry filters on the market.

An injector service (cleaning/calibration) as well as new nozzles may have positive effects in the mileage dept as well. Look up Franko6 on the forums for this service, as well as Drivbiwire. Both of them offer this service for a reasonable price.

[Fowvay]

I suggest selling your 18" wheels and getting some 15" wheels with 195/65 15 low rolling resistance tires. You will get a 5mpg+ bump in mileage from the reduced unsprung mass and rolling resistance.

[Lew]

Never over rev the engine until the cooland lamp is out. Not a good thing to do when the engine is not up to operating temps.

[sullyTDI]

Get a Rocket Chip Tune, Got mine about a month ago, and once i have went through a tank or two or playing around, I have now got 605+ miles on this tank and not in the red yet.

Granted I have the tune plus sprint injectors and ran down and passed a yellow mustang after they blasted by me at about 100mph the other day and still haven't used a hole tank of diesel....

[sullyTDI]

Originally Posted by Lew

Never over rev the engine until the cooland lamp is out. Not a good thing to do when the engine is not up to operating temps.

Second that!

[FarrisK]

Originally Posted by Lew

Never over rev the engine until the cooland lamp is out. Not a good thing to do when the engine is not up to operating temps.

Wait a few minutes after. It goes out too soon, according to most sources.

[Judee]

I've been mentally entertaining the idea of having someone create an aluminum plate to smooth out the bottom of the car... I haven't actually asked for a price yet... but I'd imagine if it can yield a 5-10% improvement in fuel economy, it would pay for itself pretty fast.

[SEABEECM1]

unless i mis read something is this a automatic or 5 speed ? If automatic 40-42 mpg is normal right?

[MichelleRoze]

Automatics, depends on the traffic. I get 40-42 on long highway trips only! City/stop and go Atlanta traffic, more like 37-38... But I'm also a bit of a lead foot too, so ya know. I kinda enjoy seeing soot come out the tail pipes and people's faces like something is wrong lol I'm easily amused.

[Bo185]

Best mod I have done is adding a taller 5th gear!