mpg improvements

Any suggestions on intake, exhaust, and tuning mods to improve mpg? I have a 2002 beetle with 135,000 miles, getting 45mpg. Thanks!

The thing which makes (by far) the biggest change to MPG is to change driving style. Most physical mods only make a very slight difference.
* LRR tyres
* Pump up tyres hard (beyond the recommended, but less than the sidewall max)

Regarding vehicle modifications. First look at the likely remaining lifespan of the vehicle, and work it out on a cost/benefit basis. Few mods will improve your MPG by more than 1%.

* The air intake on a TDi is pretty good - actually better than those oil-impregnated cone filters (which will kill your MAF due to oil contamination).
* Possibly a slight difference on exhaust but probably not enough to detect
* Fit a scangauge / ODBII reader if you don't have an MPG readout on the dash. This allows you to modify your driving behaviour. Worthwhile.
* A 5th gear mod is sometimes done (this raises the gearing). If you can do the work yourself it might just be worthwhile, but if you pay a garage to do it you will never get the money back.
* Aerodynamic - this is possibly the most useful area, will improve MPG slightly at high speed. Front splitter, spoiler, undertray. But again, you're unlikely to make the money back.
* Tuning... hmm, maybe, if you can remap it yourself. Try to get more low end torque so you can keep RPM lower. But you will never make the money back if you get it done professionally.

Work out the dollars and cents until it makes sense. (I know, it sounded good in my head)

Diesel is, for round numbers, $4/gallon.
You are paying 400 cents for 45 miles, or 8.88 cents per mile.

If you increase your FE to 50mpg that works out to 8 cents per mile.

Annually, if you drive say,... 20,000 miles that 0.88 cents per mile savings equals:

17,600 cents.

Less than two hundred bucks a year.

How much do you want to spend increasing your FE from 45 to 50 mpg, with no real guarantee of averaging 50mpg. (+10% is very optimistic)

slugbug said:

Any suggestions on intake, exhaust, and tuning mods to improve mpg? I have a 2002 beetle with 135,000 miles, getting 45mpg. Thanks!

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What are your driving conditions and which transmission?

MikeMars said:

The thing which makes (by far) the biggest change to MPG is to change driving style. Most physical mods only make a very slight difference….

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Mike did a very good job. Back in the 60's you could make good improvement in power, and mileage by improving the intake and exhaust, but the auto makers found out about it and figured out it was almost free to make those improvements so today your car already has those improvements.

While I agree that the most important thing you can do is driving style, but you may be able to gain a little with an adjustment to the tune.

who does the best adjustment tune for mpg?

Bob_Fout said:

What are your driving conditions and which transmission?

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5 speed and highway miles but i do idle in the mornig for 20 minutes to warm it up

Don't do it! It does no good to let these diesels sit and run. They won't warm up until you're actually moving on the road. In the middle of winter (at least NC's version of winter), it would take me between 5 and 10 minutes of driving to start blowing heat. The only time it ran was when I had to clean off the windows.

3516ACERT said:

Work out the dollars and cents until it makes sense. (I know, it sounded good in my head)

Diesel is, for round numbers, $4/gallon.
You are paying 400 cents for 45 miles, or 8.88 cents per mile.

If you increase your FE to 50mpg that works out to 8 cents per mile.

Annually, if you drive say,... 20,000 miles that 0.88 cents per mile savings equals:

17,600 cents.

Less than two hundred bucks a year.

How much do you want to spend increasing your FE from 45 to 50 mpg, with no real guarantee of averaging 50mpg. (+10% is very optimistic)

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Wow! Do the math! Hello! Thanks for your response. Keep the right foot light.

slugbug said:

5 speed and highway miles but i do idle in the mornig for 20 minutes to warm it up

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No idle is needed other than a minute or two at most.

How fast do you drive on the highway?

LRR tires, no more than 60 mph on the highway, drive so that you use the brakes as little as possible, don't idle it (you are getting 0 mpg when you idle and it does no good to warm these up that way). I stay light on the go pedal as much as possible but do lay it down once in a while to work the turbo.

... but i do idle in the mornig for 20 minutes to warm it up ...

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Like the others have said, skip this step. The best way to warm up the engine is to drive it (carefully, no big loads or revs while it is still cold). Are you having problems with ice? I use an icescraper on the outside (and sometimes inside!) of the windscreen, but haven't needed to do that for a couple of months now.

Idle uses 0.2gal/hour once the engine is hot, and a lot more when the engine is cold. TDis are too efficient to warm up effectively on idle alone.

You will also notice a difference once its warmer out. regardless if you try to warm it up or not. I notice over 100km difference per tank. that being said im from edmonton and our winters are the devil

Actually it is not the efficiency that keeps TDIs from warming up. It is the ultra lean burn at idle. The exaust gasses only come out at about 250F where as stoic idle in a gasser is about 1300F. This happens because the gasser restricts air flow to the point where only enough air to idle is allowed in where as the TDI flows the same amount of air whether at full throttle or idle and restricts the speed by limiting the fuel.

Assuming you're stock... and if you have access to vag-com, try timing adaptation of 5 degrees BTDC ... makes for more dieseling sounding engine but will improves combustion. Also do the cage mod.

Nich said:

Actually it is not the efficiency that keeps TDIs from warming up. It is the ultra lean burn at idle. The exaust gasses only come out at about 250F where as stoic idle in a gasser is about 1300F. This happens because the gasser restricts air flow to the point where only enough air to idle is allowed in where as the TDI flows the same amount of air whether at full throttle or idle and restricts the speed by limiting the fuel.

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Right idea but not entirely true, turbo pushes air in with throttle, so your flowing more air than idle, lol.

Bottom line is diesels use as much fuel as needed, and no more! Gassers run 8:1 at idle 14.7:1 at cruise. Diesels run about 40:1 at idle, and 18-20:1 at cruise.

A classic move!!!!

One that vw did years ago!!!

http://www.youtube.com/watch?v=9XUKOUbp_PA&feature=related

09R/T said:

Right idea but not entirely true, turbo pushes air in with throttle, so your flowing more air than idle, lol.

Bottom line is diesels use as much fuel as needed, and no more! Gassers run 8:1 at idle 14.7:1 at cruise. Diesels run about 40:1 at idle, and 18-20:1 at cruise.

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Yeah but they are talking about idling the engine in your driveway. Turbo is effectively invisible in this condition - no throttle, no VNT directing any exhaust flow onto the turbo, etc.

shizzler said:

Yeah but they are talking about idling the engine in your driveway. Turbo is effectively invisible in this condition - no throttle, no VNT directing any exhaust flow onto the turbo, etc.

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The turbo is always spinning if the engine is running.

Dang it you guys just want to make this complicated

Turbo is powered by excesive heat in exaust gas. At idle the engine would acutally get more air with out the turbo in the way restricting air flow. but this is not important what is important is the mixture ratios.

For the first minute the egr is partically open so the engine pistions are not breating entirely fresh air. this air is warmer becuase it has been previously burned. the mixture at this time is probably closer to 30:1 and temps around 450 . After the first minute the egr closes to prevent suit build up and the mixture goes to 60;1 or 80:1 and temps drop to 250 ish. Stock full throttle is closer to 18:1. if you have a chip tune they get this down to 15:1. Crusing only requires about 1/2 the aviable power thus crusing would uses more like 36:1 (18:1 *2) but the egr recycles air and reduces this to more like 30:1.

Oh and FYI no gas engine would use a 14.7:1 ratio that would produce 1700F egts and burn your valves in a mater of minutes. even on titanium motorcycle valves we dare not go leaner then 13.5:1 and idle is generally set to 13:1 or 12.5:1

Nich said:

Oh and FYI no gas engine would use a 14.7:1 ratio that would produce 1700F egts and burn your valves in a mater of minutes. even on titanium motorcycle valves we dare not go leaner then 13.5:1 and idle is generally set to 13:1 or 12.5:1

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No, sorry, plenty of gassers operate at stoich or leaner. Most cruise at that, and only run richer under acceleration. Civic VX, Insight and Toyota Prius all run leaner than 14.7:1, the Insight as lean as 25:1 cruising.

Yeah actually most new gas engines do run _exactly_ at stoich (side note, with 10% ethanol stoich is now ~14.3:1) until piston/cylinder/valve temperatures get dangerous. So really only at 80% throttle and above where they enrich. The limit continues to be pushed on new engines.... Some gasser turbos are running 1700F without issue - 500 hours at peak power on the dynamometer, for instance. Scary stuff, but somehow they stay together.

Wait, what was the original topic of the thread ?

Nich said:

Dang it you guys just want to make this complicated

Turbo is powered by excesive heat in exaust gas. At idle the engine would acutally get more air with out the turbo in the way restricting air flow. but this is not important what is important is the mixture ratios.

For the first minute the egr is partically open so the engine pistions are not breating entirely fresh air. this air is warmer becuase it has been previously burned. the mixture at this time is probably closer to 30:1 and temps around 450 . After the first minute the egr closes to prevent suit build up and the mixture goes to 60;1 or 80:1 and temps drop to 250 ish. Stock full throttle is closer to 18:1. if you have a chip tune they get this down to 15:1. Crusing only requires about 1/2 the aviable power thus crusing would uses more like 36:1 (18:1 *2) but the egr recycles air and reduces this to more like 30:1.

Oh and FYI no gas engine would use a 14.7:1 ratio that would produce 1700F egts and burn your valves in a mater of minutes. even on titanium motorcycle valves we dare not go leaner then 13.5:1 and idle is generally set to 13:1 or 12.5:1

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My Challenger from the factory runs 14.7:1 on the highway cruising....since then I have played with the tuning...now runs 15:1 on the highway with no issues....and runs a solid 11.8:1 at WOT....all measured with a Wide-Band.

slugbug said:

Any suggestions on intake, exhaust, and tuning mods to improve mpg? I have a 2002 beetle with 135,000 miles, getting 45mpg. Thanks!

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Invest in a scanguage and a taller 5th gear, LLR and lower your speed (left foot mod). This should get you at last 5-7mpg improvement.

my passat seems to run very well. it has a new injection pump only a few K ago, doesnt seem to have much blowby although its at about 180k, it does have an EGR CEL 00560 and its all stock 1Z. has 5w40 rotella t6, stock size tires at 45psi, no roof rack. i cant seem to break 43mpg. I am in neutral all the time, go the speed limit, try and keep the engine at the limit of load/acceleration on hills, etc. i do floor it occasionally perhaps once every 2 trips. my driving is pretty mixed with a lot of 45-60mph highway for 12 miles at a time then a good amount of city too. i'm generally getting 40 mpg. this seems kinda low given what some are claiming for these 1Z cars. any input?

Cage mod?

dezeljunky said:

Also do the cage mod.

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Is that the hollowed out Beetle on bicycle tires in the video above?

COcyclist said:

Is that the hollowed out Beetle on bicycle tires in the video above?

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I just did the cage mods and the car ran smoother right away! I am thinking about using the dielectric grease in every contact point in the car since it cannot hurt.n

NewTdi said:

Invest in a scanguage and a taller 5th gear, LLR and lower your speed (left foot mod). This should get you at last 5-7mpg improvement.

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Here in America, Is it not the "Right foot mod"?? LMAO!!

09R/T said:

Right idea but not entirely true, turbo pushes air in with throttle, so your flowing more air than idle, lol.

Bottom line is diesels use as much fuel as needed, and no more! Gassers run 8:1 at idle 14.7:1 at cruise. Diesels run about 40:1 at idle, and 18-20:1 at cruise.

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You are quote air/fuel mass ratios though arent you? you cant just use the ratios to say that diesels use less fuel...even if it is true. as the person you replied to said, petrols create a vaccuum using a throttle butterfly, so less air enters the engine. therefore for a given AFR less fuel than the same AFR at wider throttle settings.

Using AFR alone to conclude that diesels use less fuel is a false conclusion.

Stu

hip001 said:

Here in America, Is it not the "Right foot mod"?? LMAO!!

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OOops you're right!