Improving mpg in Vw TDI
 

I have an 06 jetta tdi. I have increased the tire pressure in my car. The car is out of warranty now and I'm trying to understand a few things.

I was trying to find out if I went to larger intercooler if that would help mpg and the pep the car has? The other thing is changing out the muffler to something that's more high flow. I read elsewhere that adding a fogger (water methanol solution has worked well with the older diesel vws. I read some place that he was able to get 3-4 mpg with the fogger on his 98.

I haven't heard that intake or exhaust modifications as you describe will improve mileage. I suggest taking care of the easy things first, like a good thermostat and a clean air filter. You could find out if you can get a chip tune oriented towards economy, but the TDI engine is hard to improve.

You could focus more on the car itself, and work on blocking the grille, using a coolant heater, possibly adding a lower air dam....that's where I am currently focused.

As a diesel owner. may I suggest a some suitable easies.

I am UK based and therefore suffer the sub zero damp morning starts that kill fuel economy.

Therefore I can reccomend a grille block, it does three things for diesels.. it helps improve aerodynamic drag, it helps reduce the airflow over the engine which means improved warmup time, and a curious bonus I've discovered is that if you seal it in, it helps reduce heat loss when the car is parked. Thus the engine is a couple of C warmer in the morning. I strongly suggest blocking the UPPER part of the grille, not the lower part. It helps push air over the top of the car and helps in the parked insulation there... I've tried blocking upper and lower.. I've only had gains with the upper blocked. Do make sure you're not blocking off cooling to other components such as the gearbox

Tyre pressures you've done.

Mud flap removal bought me a couple of percent.

Weight reduction of course.

Adjust the nut behind the wheel.. let's assume you've done that.

Clean out the pipes.. diesels have dramatically higher air throughput that petrols.. if you've clogged pipes then that will hurt.. check your Mass Air Flow sensor and your Exhaust Gas Recirculation... which often get horribly coked up.

The exhaust will have diesel particulate filter (DPF) and/or catalytic converter, you MIGHT be able to delete these depending on local annual legal testing and what sort of control signals if any they chuck back... you might be able to chip the engine not to worry about the DPF.

Also take further a look around this site.. there are some excellent posts by someone else with a jetta.

Derek

Having a larger IC would be good, but the gains from replacing an existing intercooler with a larger one are much smaller than from adding one to a non-IC engine. IF you are going to do it anyway, then instead of replacing, plumb it parallel to the first - this will give you the best cooling and the biggest drop in pumping resistance, but still not worth it, neither price-wise, nor space-wise, nor weight-wise.

Improving your exhaust may give you better FE (Our Peugeot Diesel - Part 1 - The Exhaust), but then again it may not (New Muffler = Lost MPG's). A free flowing intake is good, as long as it's cheap and easy (1.9L VW/Audi/Skoda/SEAT Diesel Mod alert! :))

And an upper grille block is a must if you are going to be driving a turbodiesel efficiently. In my case, the engine never really got up to temp, even with a lower grille block, until I covered the upper grille and put some thermal insulation on the engine.

The intercooler is a big restriction on the TDIs, some people have measured a boost drop across it as much as 3 psi. An after market intercooler could help reduce this a lot. I doubt there is room to plumb a new one in parallel. There was a nice place selling an upgrade that had a nice write up showing pressure and temperature drop before and after the upgrade.( Found it http://www.tyrolsport.com/product_in...ynotesting.pdf )

I would go to talk to the people on some TDI forum about reducing exhaust restriction and maybe see if they have figured out how to improve the intake too. (Don't use a K&N style filter)

I would forget about a radiator block as I wouldn't want to risk engine damage. (I've encountered times when I needed as much cooling as I could get)

Diesels like it warm.
Mine loves the 195deg thermostat I put in it.
A warm air intake is good too, I've heard of people putting shrouds around the exhaust even.
Mine just pulls warm underhood air.
Opening the exhaust is good if it doesn't lower your boost.
Bigger injectors will give better FE. Tdiclub.com lists the combinations that will work for your model on their FAQ page.

All that aside, as UFO said, the VW TDI is hard to improve upon.
The cars aerodynamics however are like a brick.
Anything is better than factory, airdam, grillblock (upper not lower), skirts and a kamm or boat tail.

Actually diesels like cold air better. It results in a cooler combustion which looses less heat to the cooling system and puts the energy saved into moving the piston. It also allows you to pack more air in the cylinder which further keeps the combustion cooler. More air also allows for a more complete combustion.

The only thing a warm air intake helps on a diesel is warm up time. Other than that it just makes more NOx and reduces power and fuel economy.

Opening up the exhaust never hurts boost as it reduces back pressure allowing a bigger pressure drop across the turbine of the turbo. Of course on the newer TDIs the boost is limited by the computer, but this is still a win because the back pressure on the engine is less.

Bigger injectors usually give more fuel and more power not better economy.

If diesels like it cold, why do some big diesels have intake warmers ? I'll agree it depends on the engine and outside temp. Typically intake manifold temps below 50deg F are less than optimal.


Try unhooking your exhaut after the down pipe and let me know how the free running exhaust works for you. Everything has limits. That said, it won't be an issue if he stays with practial pipe size. I have seen trucks that run like dogs with dual 8" straight stacks.

The larger injectors alow the same amount of fuel to be injected in a shorter time. This causes more to be burnt while the piston is closer to TDC. These engines are individual solenoid operated injectors, not distribution pumps like ours. Totally different animal. They vary pulse width like a fuel injected gasser not stroke length like a dist pump system.

Big rigs have them to aid in starting and engine warm up. In figure 14 of this report http://aerade.cranfield.ac.uk/ara/1937/naca-tn-619.pdf you can see that fuel economy and power increase as intake air temperature go down. All the way down to 26 Degrees F. At -3 Degrees F there is some power loss at lighter fuel settings. The engine in this test was only 14.5 to one compression ratio so with higher compression ratios the peak power for the intake air might be at a lower temperature.
[QUOTE]
Try unhooking your exhaut after the down pipe and let me know how the free running exhaust works for you. Everything has limits. That said, it won't be an issue if he stays with practial pipe size. I have seen trucks that run like dogs with dual 8" straight stacks.
[\QUOTE]
Actually I know people with engines just like mine who have run a straight pipe right out the side after the down pipe. It works great other than the fact its loud and against the law in most states.
I can't speak for the pickup trucks. They probably went with a turbo that is tuned for towing and max power that takes longer to spool.
Actually the whole idea behind the Diesel cycle is to keep the combustion stroke at a constant pressure. The closer you approximate this the more power you get per unit of fuel. Trying to get all the fuel to burn near TDC is like the Otto cycle which is less efficient.

[QUOTE=ConnClark;218634]Big rigs have them to aid in starting and engine warm up. In figure 14 of this report http://aerade.cranfield.ac.uk/ara/1937/naca-tn-619.pdf you can see that fuel economy and power increase as intake air temperature go down. All the way down to 26 Degrees F. At -3 Degrees F there is some power loss at lighter fuel settings. The engine in this test was only 14.5 to one compression ratio so with higher compression ratios the peak power for the intake air might be at a lower temperature.


It is still not an Otto cycle engine. The HP/FE gains are well documented. It is the same principles used in VWs 150hp race version and in Mercedees new Bluemotion (well they upped the injector PSI, but same result)

Chip tuning will improve pep, but be careful of the clutch especially if you have a lot of miles on the current one. A lot of remaps, especially generic ones, will just wind up boost pressure at peak torque. With long gearing the clutch is in the middle of an irresistable force (torque) and an immovable object (high gearing) so it starts to slip.

If you drive smoothly then you can get away with it for a long time (about 30k miles in my friend's case) before it starts to give up.

Depending on the engine type you can look to see if there is a more powerful variant and swap over some of the pieces from that. The 1.9s went up to 160hp (I think) and the 2.0s have gone up to 170hp in factory form - Audi TT TDI for example.

For example on the left below is the air intake from the PD130 engine, the one on the right is from the PD160 - its a straight swap.

http://www.jabbasport.com/store/medi...odxl/160_4.jpg

Although I am not convinced of the benefits yet, I'm waiting for the rest of the Autospeed article.

As ever though don't forget the rest of the car - brakes especially. Traction can become an issue with big torque increases. And smokey too.

http://www.youtube.com/watch?v=ycbiUPb8tVM

Hi, i don't know if your car is like european spec, but if is, you already have a very, very big and nice front mount intercooler, you don't need a bigger one, trust me ;)
I'm an european tdi tuner.

Are you a prof. tuner, in which case I have a few questions. :thumbup:

As I understand it not all TDis have FMIC - as in an IC mounted behind the grills. Some (like mine) have them in the front wing instead. OK its front but not in the full airflow if you know what I mean.

I am willing to be proven wrong on this. :turtle:

EDIT - Your ASZ engine code is the same as mine. :D

all mk5 generation has fmic, in mk4 version, only tdi 150 has fmic, if your car is an asz like mine your car is a mk4 version(here in europe only mk5 generation is called jetta, mk4 generation here is called Bora)
My asz is quite differnt from yours because it's the last version of asz, it's not available on golf or jetta chassis, i swaped it :)
so, if your car is a asz and it's mk4 chassis you really dont have fmic(i read your topic and the name jetta only reminds me mk5, that's my mistake).

As far as I know the 1.9 had a max factory power of 150 Hp. EDIT: I m VERY WRONG. it appears that PD 160 is 1.9

No Ideas on the rest of the thread.

I've seen that referred to as an SMIC... side mount intercooler. Apparently some Audis have dual SMICs... one on each side.

Still trying to find your question(s) in there, btw ;)

Hi,

I'm no the OP but the info is cool :thumbup:

My IC is in the bit between the front bumper and the front wheel arch.

Improving MPG on a Skoda Octavia 1.9 TDI
 

Dear Mario,

I have a Skoda Octavia 2009, with an 1.9 TDI engine. I have it almost standard but my upper grill cover. The cooling is ok, the fans have never run even at 30 degrees centigrades. The water cooling system remain always at 80 degrees ok (after warming up).

The car is responsive, the factory air intake is larger than the mod shown on this pages. So no need of modifying it. Undercover of the car is factory sealed as a standard also. I also removed the rear wheels mud flaps (I forgot that).

As you and other said, seems hard to improve MPG on this beauty. Mine has ASG transmission and even though, I am getting 5% over EPA, due to my driving habits I think, the little mods I did and the good condition of the car of course.

I am also waiting to see the next part of the Autospeed mod of the exhaust.
My mother´s language is Spanish, but what I understood from part 3, is that freeing exhaust flow didn´t improve power, what means that it probably didn´t improve MPG also. Do you agree on that?

How would you classify Skoda Octavia TDI 2009: MK4, MK5, or ...?
Do you know where is the Intercooler located in this car?

Thank you and good tuning!

Oldbeaver

Adjusting the nut behind the wheel TDI improving
 

Dear Derek,

Your advise makes a lot of sense to me.

I have a Skoda Octavia 1.9 TDI, and have done:

- Upper grill cover
- Rear wheels mud flappers removal

Please, can you explain what is "adjust the nut behind the wheel"?
Maybe a picture?

I am very interested about learning how to check/clean the MAF and check the exhaust gas recirculation. I ordered a VAG cable & software to plug into my notebook.. Do you thing these systems can be checked with the software before removing them?

Tks.

Oldbeaver

The nut behind the wheel is you, the driver. :D

Ha, ha, ha !!! :D

Thank you much!

I should have discovered that myself, was not so hard.
However, I took "nut" literally, figuring that there is some kind of thing to be tighten on these cars.

Good joke.

It didn't improve power because as he has discovered the computer keeps reducing fuel. Mileage might have gotten better though as he hasn't reported on mileage after each mod.

If it were a couple years older, you could turn it into this:
Smyth Performance | Facebook

Your skoda has front mount intercooler.
your car is a relatively recent, since the released of the golf mk5, all the tdi vw group cars have fmic, only the older ones have smic.
Everything you can do to decrease exhaust gaz temperature(EGT) will help you to get better mileage(remember egt is not the same as temperature of the exhaust piping), that's why vw is using fmic on tdi's, to get lower intake temperatures.



I´ve done some mods wich improve my mileage, one of the biggest improvement at the moment was the 15" wheels (my car has 17" from factory with sport tyres), with 15" the car is a lot free in the highway(notice that i lost handling and braking power but it's quite acceptable).
I also have a low restricted exhaust system, low restricted intake manifold with thermal coating on the intake manifold, i dont recommend you to delete egr if you want good fuel consumption, deleting egr will increase your fuel consumption, i only delete mine because i dont have another choice, but i recommend you to clean your egr and intake manifold at 100k-100k, because the dirt from the egr+oil vapours from the ccv will get your inatek manifold and egr clogged.

If you want to check some mods on my tdi engine take a look at my gallery at my forum profile, i will update my galleri soon, with pictures of my new 15" wheels and some very small aero work.



Saludos :thumbup:

I'd be shocked if airflow mods will increase mpg.
With my intake 75% plugged, there was no noticeable change in MPG after cleaning..

Same with mine... cleaning the intake made no difference in FE. What made a huge difference for me is getting updated nozzles / injectors. Could be because the old nozzles were not flowing as well, but putting new larger nozzles improved my freeway FE from ~28MPG to ~48MPG... huge difference!

I'm sure it wouldn't have made anywhere near as much difference if my current nozzles didn't have ~300K miles on them.:rolleyes:

The biggest improvement for FE for the car excluding the engine is tyres and aero.

The biggest improvement for FE or power for the engine is regular maintenance and a remap in that order.

The advantage of freer flowing air is that when you do request more power by dumping in more fuel you can get the air to burn it rather than just dumping it out the exhaust. So, you may not see a FE improvement, but you may see improved drivability.

TDI fuel yield improvement
 

Dear Mario,

Ok to all, however, I don´t see why yr 15" tires have better fuel yield than the 17" ones. I would have thought the opposite!

I also have a set of 4 17" sport tires, however, I have never used them. What you say is a surprise to me, as I was thinking sport larger tires may yield more.

By the way, I visited once Lisbon, took the tarin to Sintra and the coast train to the end (where there is a F1 circuit too). Very nice sight over there.

Ok to the EGR valve. Taking it out is no good, but there is a way to optimize it.

Cumprimentos,

Oldbeaver

There is no reason going from 17" to 15" wheels alone would improve your FE. The key is the weight of the wheels & what tires you put on them. If you get lighter wheels (so don't go with those cheap steel wheels, or even cheap alloys for that matter) you will see an improvement in ride, handling (including braking) AND fuel efficiency (particularly in stop & go situations, less so on the highway). Low rolling resistance tires will see a decrease in ride quality and handling (including braking) but an increase in fuel efficiency.

Mario probably replaced the all season performance tires with a more economy minded LRR tire to get that improvement.

Nope, this engine (the one in the Autospeed article) has all the air it needs already. Improving the flow in this case made no difference at all. Adding fuel (via the remap) added the power.

I have seen loads of postings on Skoda forums where people with my car (PD130) have fitted the PD160 intake and say things like "wow". But no A-B-A testing and no before / after dyno to back it up. The PD160 replica intake made as part of this article made no difference, in fact it went worse.

There is no agreed international calibration for the butt-o-meter :D

I think, it dependend on how clogged is your intake, egr and intercooler, it's very noticeable in performance when you clean all the intake in some cars(i'm talking only about diesel vw's).
About the 15", they are very light, the tires are thin, and i have a very long gearbox, with 17" i cant run at very low rpm's because the engine starts to choke(i dont know the corret word in english), with 15" i can run at 6gear, 1500rpm's and if i smash teh pedal the car goes to the front, no clutch vibration, no engine choking, feels very free and light, i can spin my wheels even in third gear if i full throttle :D
it's very noticeable the difference 17" vs 15"(i'm using audi a2 15" wheel).
I believe in car with short gearbox like tdi 110 you wont feel that kind of difference, to get the point, my 5th gear top down at about +/-210km/h(redline) and i still have another gear to run, i can run at 120km/h in 6th at +/-2000rpm's.
When you modify your intake you have to think like your car ecu, your car injects fuel vs maf readings, if you change your intake your maf readings will be different, sometimes you loose performance when you change your intake you have to know what your doing, and in a turbodiesel car, the turbo sucks the air, you dont need a "special racing intake" :)
I just mod my intake because i have to, i have no choice my car was a drag racing car, when i was using it to race i dont care about smoke, mileage etc, i just need a lot of air to burn a lot of fuel, as a street car, i care about the smoke, i care about the mileage, i'm very happy whit my street econo tune, very, very happy, but i know i can do even better, i have to try more ideas i have collected in this forum, and see if they work in my car, i'm not an engineering, i'm just a mechanic.

If you changed the rolling diameter of the tires your FE didn't go up as much as you think since the odometer thinks you are going further than you really are. Your speedometer is off too, luckily it reads faster than you are actually traveling, so you'll just get honked at and not get the police after you. :-D

http://img37.imageshack.us/img37/3674/testes.png
By mario_marques at 2011-02-01


This is my 5th gear with 15" wheels(not at redline but close), i also have digital meter in my car and i know how to calc gear rations vs wheel ratio ;)
I still have the sixth gear, i can set the speedometer in vag-com for 15", 16", 17" or 18" wheels.

Setting it for wheels is not the same as setting it for a different rolling circumference. But as long as you have tires that match one of those sizes you're good.

Did what Google earth said match your speedo? If not you have to include that percentage in all your calculations ... that seems like a lot of work every time you fill up. :)

I'm sorry, i have to try to explain better, when i adjust the speedo, i set to the wheel diameter too, standard wheel and factory specified tyre to match that wheel (entire wheel diameter), so with 15" i can only use 195/65R15 tyres, with 16" 205/55R16, with 17" 225/45R17, with 18" 225/40R18.
My speedo reads about 208km/h, gps tracking(the google maps thing you see in the picture is actually my data from gps tracker) reads 204, my car digital speedo reads 203 almost like the gps, it's hard to know the perfect speed reading from the speedo needle(my speedo scale goes from 0km/h to 260km/h.
Usually i dont drive that way in the streets, it's only for test purpose, i always drive safe under speed limit & econo.

Just making sure. ;) I've probably spent too much time on vwvortex where stuff like this is way over their heads. :D

Thanks Mario, I have been trying to find this out for myself due to problems with a U.S. EGR cooler recall. From what I can find it is better to leave the EGR intact for lowest fuel consumption.

Is better to keep it clean instead of removing it.
Fuel consumption increases a little when you delete your egr because when egr is open, turbo pressure drops down & maf readings, maf is the "thing" who gives your car the information to inject more or less fuel, more air, more fuel.
You can see this by yourself in vag-com, you can do the egr test and see how it changes the amount of air into the engine, in this test you can also see how is your vnt turbo system working, my car doesent have egr, in cars without egr, this test dont work.
The negative side of having a egr is that your intake will get clogged, when this happen you will loose performance and your fuel consumption will increase, so the ideia is keep it clean.

In most cases with a diesel engine elimination of EGR will increase mileage

http://www.iaeng.org/publication/WCE...p1548-1552.pdf

There are some exceptions to this but it takes just the right amount of EGR coordinated with the right injector timing to best approximate the ideal diesel cycle.