hard data on 17/22 ( or equivalent ) turbo upgrades and its MPG affect

Hey everyone.

I am seeking hard data on 17/22 ( or equivalent ) turbo upgrades and its MPG affect. I haven't been on here for very long and I have searched with agonizing results, about nil.

I have been told by respectable authorities that larger turbo's will not hamper MPG if you simply don't use the POWAH.

Looking for testimonies. Thanks!

I think deep down you know it won't.

I suspect the testimonials will start flowing in.

I'm quite curious about this myself. my gut says MPG's won't be better with bigger chargers. driving leisurely its still more mass to move...

you know what, I am going to go the other route. I would bet they DO get better mpgs. after all, the bigger turbo is MUCH more efficient than the(or atleast my) Stock turbo(KP39) and with an appropriate tune that uses said efficiency it would yield better mpgs. I know of one member who has the same car as me and has a better tune AND a 17/22 and is getting MUCH better mpgs than mine. last I spoke with him he was getting about 9mpgs higher on the interstate. and he has a bigger tune than me. I for one cant WAIT to get a bigger turbo, but not just for the increase in mpgs

Eric B

in the week that i had the turbo on before i got tuned, mileage stayed similar...

since tuning, i can't keep my foot out of it, so it's fallen significantly

if you put that turbo on, it might be possible to get the same MPGs... but good luck keeping your foot off that skinny pedal

I have 178whp and can get 48mpg. But I have a six speed. lol

My mileage with a 2005 Jetta automatic was 38-41 MPG. The best I got was 41.5 on a 350 mile trip, 95% on the freeway and flat. After installing the 17/22 and tweeking the Diesel Inside tune to match the turbo, around town is still 38-41. On the last trip I took, identical to the previous one, I got 47.5 MPG. Same amount of passing and the like.

I have noticed that I do not use as much high RPMs as before to get the same "go". Yes, more boost is working.

With the mods in my sig I get 1mpg less average than the day I bought the car. I in no way drive for mileage, in 50/50 highway/city traffic. But I did notice that the highway mileage increased and the city mileage dropped, but is even in the end with my commute.

On a recent long trip with cruise set on 85, and some air conditioner use the car averaged 46.

I have tracked every gallon of fuel that has been put into my car. The biggest mileage killer was the evry mod, because you're just dumping fuel in without adjusting anything else.

David

Driving with a light foot with a VNT-17 hot side and a good tune?

I would guess there is little to no boost being called for.

Which is least restrictive, a small VNT-15 hot side or a larger VNT-17 hot side? Yes, the VNT-17 or 17/22 would have more spinning mass, but this is not very much of an issue if little to no boost is being called for. I would guess it is wash, where a VNT-15 or VNT-17 would make little difference in MPG's when driven the same.

The MPG's are going to be affected most by the tune. This is where I love the RocketChip tunes, Jeff does a great job of balancing performance, total drivability and MPG's with his tunes... granted, I have never tried any other TDI tuning options, but then again, Jeff has never given me a reason to want to.

The key as I see it to great MPG's and improved performance without sacrificing drivability is a whole package approach where you carefully match all of your mods to each other and to the tune. Jeff is a degreed Mechanical Engineer, an excellent mechanic and a total gearhead besides being a world class tuner/hacker. If anyone could answer the original question definitively it would be him.

But I'm sure Jeff's answer would start with, "It depends..." and would include such questions as, "with what intake/exhaust mods? with what nozzles? with what IP?..." Because many variables affect the answer besides just the size of the turbo.

My fuel consumption was 5.9l/100km when I bought the car. With 260hp and few odd mods it averaged 5.9-6.1 depending on my driving style. The highest I calculated was around 7l/100km but that tank had 20 1/4 mile runs and some spirited driving and testing... If you keep yourself from flooring it all the time the modded car usually wins. Firstly the larger turbo will flow more air out of the exhaust which leads to better effiency. Secondly larger nozzles lead to shorter injection window for the same power. Thirdly most tunes are not ecologically designed since few of us go with the TUV or similar way to get the setup legal. So you get better MPG but you get more polution(mostly NOX) in the same time.

My fuel comsumption is awful, but could it be that in a NB, averaging over 80 mph you might not get as good as mileage as doing 60 with a vnt 15? Hell yes my milage went down, but so did the pedal. It is hard if not impossible to not use the power you will have once you tune your tdi to run correctly. At 60-65 I still get 48-52 mpg, but who whats to drive there?

I am not militant about keeping track of my mileage. but when I do. I do it right. car filled to brim, then filled again before I crunch numbers.

The best mileage I have ever gotten was 51 mpg. that was on a trip from Boston to Philly. at trip I have taken many times before. and squeezed 48.

51 was with all the mods in my sig, EXCEPT the 11mm pump.

RocketChip can tune your car so that you request LESS fuel while "rolling" down the road, when you have a 17/22 turbo. I believe that he leans you out a bit. That is possible because the larger turbo flows more air at the same RPM that a smaller unit.

I hope I explained myself well enough. short answer to OP: yes, you can. if you tune"Aas far as I know. which when it comes to tunes is not very far.

I know I take a bigger hit in mileage when I put on the summer wheels than when I changed the turbo. If you drive the speed limits and take off from stops normallly, I haven't seen an upgrade that is going to change your economy more than 5%.

With my ALH Skoda I did not see any changes to fuel consumption while upgrading (in steps) from stock to:
1. PP502
2. Race520
3. 11mm plunger
4. GT1749VB

Only thing that did actually increase MPG was when I replaced rear muffler with free flowing one.. that decreased fuel usage from 4.4L/100km to 4.2L/100km:
http://holysmoke.fi/pages/artikkelit/takavaimentimen-vaihto.php

Its completely shortsighted to say a turbo only will yield better mpg. Too many other factors are at play. Injectors, pump, intake, exhaust, and tune will all balance to have an effect. You cant just slap on a turbo and expect a jump in mpg.

I can get 38mpg in town short tripping it in the freezing cold (worst possible mileage conditions), or I can get 53mpg on the freeway doing 70mph. So, with all the possible variables, I'd say your mileage could be anywhere from 30mpg-75mpg ;-)

Wow.. can of worms!

So basically gains are from highway driving with "easier" breathing and loss is from around town because it is more difficult to keep it "off bizoost"

Strictly from a conservation of energy standpoint, would the energy re- captured by the larger turbo not translate into more forward motion, hence more mpg?

I understood that the turbo is could be looked at, amongst other things. as a means to capture more of the energy that would otherwise be wasted as exhaust and translate it into kinetic energy and forward motion. Based on that fact alone, and all other factors being equal, could one assume higher mpg with a bigger turbo because bigger turbo = more energy re-captured?

NOTE- This is a question and not a statement

oldpoopie said:

Its completely shortsighted to say a turbo only will yield better mpg. Too many other factors are at play. Injectors, pump, intake, exhaust, and tune will all balance to have an effect. You cant just slap on a turbo and expect a jump in mpg.

Click to expand...

at the same requested fuel level in a given rpm range, more boost should allow for better mileage since now you have more air to compress the fuel to "burn" it more thoroughly reducing wasted fuel

although you may notice an increase/decrease depending on your usual driven rpm range, since you may be making more/less boost in it

so in short, "it depends"

boosted alh said:

at the same requested fuel level in a given rpm range, more boost should allow for better mileage since now you have more air to compress the fuel to "burn" it more thoroughly reducing wasted fuel

although you may notice an increase/decrease depending on your usual driven rpm range, since you may be making more/less boost in it

so in short, "it depends"

Click to expand...

Here is my crude layman's understanding of the concept:

Remember that the more air volume that is being compressed or the higher the compression ratio, the greater the amount of power that is needed to push the piston upwards in the cylinder. This translates directly to increased pumping losses.

A given engine outputting say 200 horsepower on the flywheel might actually be making a total of 300 horsepower where 100 horsepower is being consumed by parasitic losses including friction and pumping losses.

Another given engine might output the same 200 horsepower but with only 70 horsepower in parasitic losses. This second example *should* yield higher economy because less fuel is needed to make 270 hp than to make 300 hp.

Volumetric Efficiency plays a huge part in all of this and admittedly the way VE is calculated is pure voodoo science to me where I do not understand the standards.

The best economy will always be found where just enough power is being made by an engine to propel the vehicle with the minimum pumping, frictional and other parasitic losses. This will vary by engine design, modifications affecting the engine's VE and the actual vehicle being propelled.

When I played with my ALH VNT setup the best economy came with least boost.
I ended to be usin ~0.1bar of boost during 80km/h road driving as that setup still had good throttle response (I was using stock ecu).
Forgot to mention earlier I changed also 3bar map because Race520 nozzles started giving too much boost at upper RPMs. 3bar map raised the boost some and reduced CEL light coming as turbo had a much harder to keep the request.

I tried to raise the boost at driving speeds with VNT adjustments, but that did only increase fuel usage.

I theory I would have assumed that increased burning efficiency and more air to be heated (and expanded) would have increased MPG, but I guess it wass due pumping losses that I saw reduction.
TDi engines seem to be sensitive to exchaust back pressure as I saw 4.5% increase in MPG when I changed the rear muffler..

I would have liked to decrease boost to minimum and EMP to minimum because of fully open VNT vanes at part throttle, but I got some problems with the chipper and that did not ever happend.. so i do not know how it would had worked out and it remains as a theory to me =)

the particular compressor on the 17/22 is about right smack on the peak efficiency island when you are cruising at 80 mph. That means less vane angle to drive it, at a slower speed, therefore less pumping losses, better fuel economy. I see this result time and time again.