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Engine Specific Info and Questions => IDI Engine => Topic started by: Northboundtrain on August 25, 2005, 08:14:56 am
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The next project I have in mind is building a 1.6L engine for the very best fuel economy I can possibly get. I'm wondering if it's worth the effort to find a turbo block (very hard to come by around here), or, for my purposes, whether an n/a set up would do nearly just as well (I already have a block).
I clearly see how a turbo allows more fuel to be burned for more power, but I've never quite understood whether a turbo makes the engine run more efficiently under a given load.
Any insights greatly appreciated.
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Well, I can tell you my experiences -
I had an 81 Rabbit pickup with an NA 1.6 diesel. The fuel screw was untampered with, and I got about 38 mpg. The compression of the engine was mostly in spec, but not the best.
My 88 Jetta TD gets 40 mpg and is by no means fast but it is MUCH faster than the truck was. I can go up grades on the freeway at or above the speed limit which the truck had a hard time doing. Compression is good on the jetta at 475 across. The only things I have done so far are maintenance and a set of GTD nozzles with a bit higher pop pressure.
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in theory a turbo should get better economy.
in practice that rarely happens, in my experience. i guess it depends on your driving habits.
if you're going for max fuel economy, then i imagine the overall budget of the project is also a concern (its money out of your pocket one way or another) so i would stick with the NA diesel. cheaper to build, less parts to break. will be slow, but you want economy so you won't be mashing the pedal anyway. my 2 cents.
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For best MPG lust use your na engine and pump. Add a turbo and don't turn up the fuel. Add a larger exhaust and use TD injectors. Install a cool air intake if you don't already have one. be sure your rings and valves are in great shape. Set the timing to turbo specs. Use stock size 13" tires.
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DRcool,
Since this will be a rebuild, what kind of pistons should I use? Turbo or N/A?
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N/A by far-gets way better economy if your careful. I was getting 1400kms per 50L (850 miles on 13 gallons) reliably and consistant on my 87 Jetta keeping it under 65 mph daily commute. Totally stock engine but modified exhaust (cherry bomb muffler-free flowing).
The turbo engine excells when you need the power-if your not under boost the fuel economy suffers cause the intake/exhaust are alot more restricted. Of course you do have the extra power when needed...
If your living in the mountains go with a turbo you need it and will get better economy when climbing.
I have owned close to 20 diesel VW's, the n/a diesels always far outshined the turbos when it came to fuel economy even on the same commute/speed. I live in a pretty flat area though, if your in the mountains I think a turbo would be needed or atleast the close ratio trans.
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reading through corky bells "maximum boost" book (amazing book btw, you should all get a copy) , you cant get somthing for nothing, no such thing as free energy and the turbo will decrease mpg under all conditions., even idling at a stop light.
normally it is not very much though, if you have a properly sized (large) turbo which has minimal backpressure off boost and reduced backpressure on boost you wont take a large mpg hit. if you run a dinky little k26 you would see alot of backpressure which is not good for efficency.
the only time you may see a mpg gain is under extreme load, such as hill climbing or pulling a huge load, because a turbo engine can have the power to get the job done and get out of that situation quicker than a n/a engine, which will be bogged down and under load for a greater length of time thus having a lower mpg over an extended legth of time.
imagine a vw pickup loaded up with stuff in the bed, going up a mountain side at 65mph. say it peaks the mountain in 15 minutes then we would have 15 minutes of boost action. imagine now that same truck with a n/a engine, running in a lower gear at 25 or 30mph with the petal floored, it now takes 30-40 minutes to go over the same distance.
30-40 minutes of full n/a throttle would probably cost more fuel than 15 minutes of boosted action. the boosted engine uses more fuel, but it gets the job done substancially quicker.
of course, with the hundreds of variables in engine design, hill grades etc, one cannot possibly give a definitive answer without knowing all the facts.
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It actually is possible to get "something for nothing" with a turbocharger, because a large part of the energy it uses otherwise literally goes out the tailpipe as waste heat. True, a turbo can cause backpressure, which the crankshaft must work against. But when the turbo is working right, it will put a substantial amount of this energy back into the crank via boost pressure on the intake stroke. In some cases, a well-matched turbocharger will even add more pressure to the intake stroke than it adds restriction on the exhaust stroke.
The main practical reason a turbodiesel will get better fuel economy than a naturally aspirated is that the engine can be loaded more and run at a lower RPM, where the engine will operate at an improved efficiency (lower brake specific fuel consumption.)
PS - this has been covered before:
http://www.vwdiesel.net/phpBB/viewtopic.php?t=649
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When I put in the GTD nozzles and messed with the LDA pin the car smoked a lot so I turned down the fuel screw a tiny bit as a quick fix. It made the car substantially slower and actually hurt my mileage. I had to rev the engine higher to make the same amount of power which increased the fuel consumption. IMO, an NA diesel would be fine if most of the time you drive in the city, but I wouldn't want to deal with the lack of power on the freeway again. If you want to go 60 mph on the freeway here you're going to get killed and I had to drive the truck with my foot to the floor on the freeway. It would slow down to 60 or below whenever I hit any sort of real grade. I just found it incredibly frustrating and I don't think I'd want to wish that on anyone.
As for the backpressure issue - 80% of the energy which spools the turbo is actually heat energy. There is not sufficient pressure to really create boost without lots of fuel. After seeing how slow my car can be to spool, I don't think the stock turbo is really all that restrictive. If it was, you could see boost by revving the engine in neutral..
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I agree that a 1.6lTD turbo has a pretty free-flowing turbine section. (And that's part of the reason why the thing won't spool very quickly!) It turns out that the cross-sectional area of the most restrictive area of a 1.6lTD K24 turbine housing is about equivalent to a 1.75" diameter exhaust pipe. According to some measurements I took, there was a ring with a width of 8mm at a diameter of 59mm:
(http://www.imagestation.com/picture/sraid181/pb485f867d1c80508f09da0ce8a554b9b/f2df408c.jpg)
This gives 2.3 square inches.
Granted, the gasses are vortexing through that area not going straight through, so the effective area is probably significantly less. No doubt there is some pre-turbine backpressure happening when boost pressure is being developed, but the whole idea is that this energy is captured by the turbine wheel (and re-delivered to the engine through the compressor.)
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According to holset's web site, turbocompounding allows even greater engine efficiency to be achieved by a turbodiesel (46% instead of 42%). That is basically a turbine wheel in the exhaust but it is connected to the crankshaft mechanically by gears. So it basically captures exhaust gas energy and uses it to mechanically drive the crankshaft.
(http://www.holset.co.uk/pics-related/2-products/2-5-turbo-technology/2_5_1-current/2_5_1_3-turbocompound%20system/2003%20Turbocompound.jpg)
link: http://www.holset.co.uk/files/2_5_1_3-turbocompound%20system.php
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i dont think you are measuring the turbine section quite right. just the outside diameter of a pipe means nothing without taking into account what is inside it. in this case, a turbine wheel.
its that ratio of parts which combined with other readings can indicate how much packpressure you might see for a given engine.
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Thanks for all the info so far.
fspGTD: I read the other thread, thanks for the heads up.
So tell me if I'm on track. A turbo essentially makes a smaller engine larger and more powerful by increasing the volume of air that flows through the engine and increasing the effective compression ratio.
I know that given the same load or horsepower requirement, a smaller engine running closer to it's maximum torque will be more fuel efficient than a larger engine. But if the horsepower requirement increases, and the smaller engine has to increase its rpm beyond it's maximum torque curve in order to meet the hp demand, then it becomes less fuel efficient relative to the larger engine. So as the hp requirement increases, at some point the larger engine then becomes more fuel efficient than the smaller one.
Therefore, is it safe to say that the answer to my original question of whether turbo or n/a is more fuel efficient is: "depends on your load or horsepower requirement"? And if this is true, then suppose my horsepower requirement is maintaining 65 mph on a flat highway. Is this a big enough load to make the "bigger" turbo engine more efficient than the "smaller" n/a engine?
Again, thanks for the help
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It never got specifically addressed on the other thread, but I am fairly confident that the reason simply turbocharging a mechanically injected diesel engine can yield an increase in fuel economy is that the turbo increases the mass of the working fluid. As Jake notes, the turbo recovers some of the otherwise lost heat (energy) in the form of air pumped back into the cylinder. Even if combustion is no more efficient (though it probably is) the heat of combustion heats up a greater mass of air to push on the piston during the power stroke. This results in the recovery of a greater proportion of the energy released during combustion in the form of torque.
Master ACiD, Corky Bell was talking about gas engines when he made that remark. Specifically, on page 13 in response to the question Will the turbocharger hurt my mileage?, he writes "Yes. The turbo, when installed as an aftermarket item on a spark-ignition engine, is not an economizer and cannot be construed as such." [Emphasis added.] Bell carefully distinguishes between spark-ignition and compression-ignition engines, as well as between OEM and aftermarket installations. FWIW, as long as I stay off the boost in my OEM turbocharged Eagle Talon, it delivers the same fuel economy as the naturally aspirated version of the same car/engine combo. On-boost is another matter, of course... ;)
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internal combustion engines are all based upon heat, the larger the difference in heat for intake and exhaust the more power that will be produced (thats why intercooling increases power, well that and a denser charche of air), so if you recapture heat, or the use of heat to pressureize the engine then the engine will be more efficient
its all about thermodynamics
later
Justin
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you still cant get somthing for nothing though. more boost means more pressure that a piston must compress on the compression stroke. this fights torque. also backpressure fights torque. the key to making more torque instead of fighting it is burning more fuel, and to do that you need more air, where the turbo comes into play, and is why it can make more torque than it takes.
howcome the only people to have done real scientific testing on fuel economny, the epa, rated the fuel economy for a turbo vw lower, by as much as 5mpg in some cases, than a non turbo vw? shouldnt it be the other way around if what these people say is true about turbos making diesels more efficent?
im not really argueing that a turbo isnt a good thing, because i firmly believe a diesel vehicle without a turbo is almost a crime, but im just saying you cant get somthing for nothing. weither its gas or diesel or steam, no turbo is 100% efficent, not even close. thats kinda what i meant by refering to corkys book. yeah i know he only talks about spark engines, but some of the points, espically his writings on efficency are valid to any kind of engine.
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I think this arguement could be summed up best like this:
- All else remaining equal, a turbo will not increase fuel economy in and of itself. But, in the the instance that the unit of work is beyond the normal capabilities and puts such strain on the engine to acheive that goal that it is pushed beyond it's area of peak volumetric efficiency, a turbo may increase mileage as it allows the engine to operate further within it's range of efficiency.
So what does that mean?
- If you live in an area that is relatively flat, and/or the vehicle is largely operated at low speed then mileage would be better without the turbo.
- If you live in an area with a lot of hills which frequently require more engine RPM's than can be efficiently attained (ie - Downshifting) then you are probably better off with the turbo.
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i can agree with that.
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You're right Master ACiD, there is no getting something for nothing. However, the case of turbocharging a diesel doesn't fall into that category. But rather than argue about it I decided to do some additional research to find out if I was on the right track, and so dug out my copy of Sir Harry Ricardo's The High-Speed Internal Combustion Engine, to see what he has to say about diesels. It turns out that he devotes 14 pages to just boosted diesels. The pages in question are filled with graphs and summaries of his research, but in the end he boils it down to 8 main points:
1. Detonation and pre-ignition are not present, permitting higher compression ratios than with spark-ignition engines. (We already knew that, of course.)
2. A greater charge density results in a shorter ignition delay and more complete combustion.
3. Cooling the intake charge yields greater charge density, permitting greater power up to the mechanical limits of the engine, but at the cost of greater ignition delay as compared to a hot intake charge.
4. The higher the boost pressure the less sentitive the engine to cetane number.
5. Intercooling a C.I. engine results in a relatively greater gain in thermal efficiency than it does for a S.I. engine.
6. C.I. engines increase their oxygen utilization rate up to 5% (from 82% to 86%) with added boost (comparing atmo to 3 bar of boost).
7. Adding boost alone results in a increase in brake effective mean pressure (BMEP). Just 10 lbs of boost (0.67 bar) resulted in an increase in BMEP of more than 19%.
8. Turbocharging will, at almost all load ranges, result in greater gains in mechanical and thermodynamic efficiency than are absorbed by the exhaust energy used to drive the turbo. [Emphasis added.]
Ricardo's final point can be considered as primarily the result of points 6 and 7. Namely, that combustion is more efficient in boosted diesel engines, and that increasing the mass of the air taken into the engine directly results in an increase in BMEP (what I wrote above as "the turbo increases the mass of the working fluid" resulting in "a greater proportion of the energy released during combustion in the form of torque." I just didn't use technical language.)
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Those are some really interesting bits of info, Stan!
you still cant get somthing for nothing though. more boost means more pressure that a piston must compress on the compression stroke. this fights torque. also backpressure fights torque.
That is true, but for every upwards stroke there is a downwards stroke. While the extra cylinder pressure and pre-turbine backpressure fight the piston as it moves up during the compression and exhaust strokes, (like you said - sapping power and torque from the crankshaft,) the extra cylinder pressure and intake boost pressure help the piston on its way down during intake and power strokes. So it seems then that that the net effect on the crankshaft through all four strokes would be zero, provided that the turbo could put out as much boost pressure as there is pre-turbine backpressure.
Which EPA diesel fuel economy ratings you are referring to?
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both of these subjects on compression ratios and intercoolers are not involved in the original topic, and the spesfic diesels we are talking about dont even come with intercoolers. heck their intakes are about 3 inches from the turbo!
now back to my question, why is the epa's established fuel economy ratings rate vw turbo diesels 5mpg lower than the same car and engine without a turbo?
check it out for youreself, at fueleconomy.gov. they list alot of cars including turbo and non turbo vw's, and the turbo engines are listed with lower mpg. the 85 jetta is the one i am spesfically talking about.
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now back to my question, why is the epa's established fuel economy ratings rate vw turbo diesels 5mpg lower than the same car and engine without a turbo?
I'd guess that could be because they rated those cars when they were new and the speed limit was 55mph. An N/A diesel can do 55, no problem. But 65+ might be an issue going up hills and such which makes you downshift and then your economy goes out the window.
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I wouldn't make too much out of what seems like one data point (1985 VW Jetta). The test results of these kinds of general fuel economy tests simply vary too much (potentially for a number of reasons) to take them literally. There is also other fuel economy data that contradicts the 1985 naturally aspirated 5mpg highway fuel economy lead.
If you go to the source of the data, the EPA, and take a look around there, at some other data points:
http://www.epa.gov/otaq/fereport.htm
...for example check out the 1983 model year data, comparing the VW diesels. You'll find the turbo-diesel is sometimes equal, sometimes a little better, sometimes a little worse than the naturally aspirated diesel, and the numbers vary much more depending on transmission equipment than presence of turbo:
estimated miles per gallon for 1983 models years
1983 Jetta Diesel, 5-speed manual: 42 mpg
1983 Jetta Turbo-Diesel, 5-speed manual: 43 mpg
1983 Jetta Diesel, 3-speed auto: 37 mpg
1983 Jetta Turbo-Diesel, 3-speed auto: 36 mpg
1983 Rabbit Diesel, 4-speed manual: 50 mpg
1983 Rabbit Diesel, 4-speed manual: 48 mpg
1983 Rabbit Diesel, 5-speed manual: 43 mpg
1983 Rabbit Turbo-Diesel, 5-speed manual: 43 mpg
1983 Rabbit Diesel, 3-speed auto: 35 mpg
1983 Rabbit Turbo-Diesel, 3-speed auto: 36 mpg
miles per gallon for 1984 model years (est, cmb, hwy)
-49 state-
1984 Jetta Diesel, 5-speed manual: 43/47/53
1984 Jetta Turbo-Diesel, 5-speed manual: 41/46/54
1984 Rabbit Diesel, 3-speed auto: 35/39/44
1984 Rabbit Diesel, 4-speed manual: 31/36/45
1984 Rabbit Diesel, 5-speed manual: 44/49/57
-california only-
1984 Jetta Diesel, 4-speed manual: 46/51/58
1984 Jetta Turbo-Diesel, 5-speed manual: 41/46/54
1984 Jetta Turbo-Diesel, 5-speed manual: 40/46/54
1984 Rabbit Diesel, 4-speed manual: 47/52/61
IMO... EPA says that they only test 10% of the actual figures... I'll bet they just rolled the 1984 Jetta data into 1985. You can see that the 1984 Jetta test is comparing a 4-speed manual naturally aspirated diesel to a 5-speed turbo-diesel. The 4-speed actually gives better numbers on EPA's test. One possible explanation. Another possible expanation, is that tests simple have too great of a margin of error to be accurate enough to tell which engine is more efficiency. They seem vary when we wouldn't expect them to, so either the tests have a wide margin for error, and/or the production tolerances vary from one car to the next enough that it causes these variations.
I believe that a more accurate test of engine efficiency would be the brake specific fuel consumption plots published by VW powertrain engineers in SAE papers (see other thread for this.) These tests rule out transmission and other equipment differences including the body style, etc, and focus simply on answering the question: how efficient is just the motor itself in producing power at various engine RPMs (plotted on the x axis) and loads (plotted on the y-axis)?
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Jake, what is your Dad's VW diesel pickup's fuel economy post-turbo compared to the same engine pre-turbo?
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Dad's 1.6lVNTD (Rabbit sedan, by the way) is now getting a touch over 50 miles per gallon. That is an average reading spanning several tanks by the way, so it should be a quite accurate. Unfortuntely, we don't know what it got before the turbo was added, because the odometer had a broken tooth, and so it skipped. But we are pretty confident that it didn't get anywhere near that mileage before the turbo was added. It was smoking quite a bit then, and now it is tuned to be just on the verge of smoke during all out wide open thottle. The 50 miles per gallon is also abnormally high for what is expected of a naturally aspirated diesel Rabbit, which I'd say is generally low 40's for the way it is used.
I can also add experience with my Rabbit with swapping the engine from a naturally aspirated 1.6 liter to a turbo-diesel 1.6. Back when it was naturally aspirated, it got on average low 40's miles per gallon (41-42 mpg.) After I swapped in the 1.6lTD (stock), I remember the mileage jumped up a modest but noticeable amount, around 2-3 miles per gallon, ending somewhere around 43-44 miles per gallon. (I also measured religiously at every tank and averaged across several sequential tanks, so was able to track any changes quite well.) But after adding the turbo, it seems the old transmission wasn't using the torque to it's fullest most efficient operating point at freeway speeds. This especially became apparent after opening up the exhaust, adding an intercooler, and increasing the boost pressure somewhat. So I swapped in a 5-speed that maintained the stock .71 fifth gear, but a lower-ratio final drive (IIRC it was a 3.34 final drive replacing the 3.89 of the stock "FF" tranny), causing a drop in freeway cruising RPMs from 3000 RPM to about 2500, or about 15% lower. The fuel economy shot up to 48 miles per gallon with the "longer legs" and the higher and more efficient torque area that was enabled by the turbo. The RPMs at cruising speed on the freeway were now at a seemingly ideal 2500rpm instead of the stock transmission's 3000rpm.
It turned out that proper gearing was key to maximizing the potential efficiency offered by the turbo-diesel. Looking at the brake specific fuel consumption plots, you can see how efficiency depends highly on load and RPM, and why reducing the RPMs and increasing the load is so helpful.
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i would love to look at those epa text files but i open them in note pad, its too difficult to sort through that stuff to bother. i cant seem to open a .rpt file.
i can tell you this, when my dad put a turbo on his rabbit truck, he straight up lost 6mpg, which pretty much coincides with what epa says.
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how does your dad drive now that he has a turbo? did he tune the engine properly?
I bet your dad has poor mileage from trying to keep the car in boost while giving it more fuel to spool the turbo. Get a nice tiny turbo like the VNT-15 :D
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i would love to look at those epa text files but i open them in note pad, its too difficult to sort through that stuff to bother. i cant seem to open a .rpt file.
i can tell you this, when my dad put a turbo on his rabbit truck, he straight up lost 6mpg, which pretty much coincides with what epa says.
Yes Jake how do you open a rpt file?The site offers pdf stuff only!
My Quantum hand book also gives improved mileage for TD over N/A. Best at about 56mph 10% or so.
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Yes Jake how do you open a rpt file?The site offers pdf stuff only!
Mark - I just opened the .rpt file that is inside the .zip up in notepad like a .txt file. Any text file reader should work. Just make sure you open up the .zip file first and copy the file inside to your local machine. You might find it helpful to rename it to add on a ".txt" to the end to get it to open properly.
MasterACID: Best I can figure, assuming you guys measured your fuel economy correctly and accurately, (and with no lead foot! :wink:), is that there is something wrong with the turbo equipment that you installed. If it was all working properly, you should not have noticed a fuel economy decrease, if anything there should be a small to medium increase, like what I found when I did a 1.6lTD swap. Hard to diagnose the problem without details about what was done during the turbo conversion though.
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what was done on the conversion, me dad replaced the original engine with a fully rebuilt turbo diesel. the turbo engine was bored 20 thou, gone over inside and out. the head was totally rebuilt and surfaced with all new parts as needed. the injection pump, injectors and turbo sent to a bosch diesel specialist for inspection and repair. turns out everything was ok except he needed 3 injectors rebuilt.
i honestly dont think you can get somthing for nothing. if that was true then every diesel in the world would have a turbo. but theres plenty of diesel forklifts, road graders, generators, waterpumps etc that dont have turbos, even large equipment like my ford 4.4 liter i4 diesel power head has no turbo.
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i honestly dont think you can get somthing for nothing. if that was true then every diesel in the world would have a turbo. but theres plenty of diesel forklifts, road graders, generators, waterpumps etc that dont have turbos, even large equipment like my ford 4.4 liter i4 diesel power head has no turbo.
That's an entirely different subject. That is marketing and price point at work. Adding on the turbo increases the cost of production and to the consumer. If it isn't absolutely necessary to meet the demands then you'd be lucky to actually even see it as an option.
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There were a lot of parts that were changed when you swapped the turbo-diesel engine, and many potential explanations for the 6mpg decrease in fuel economy. It could be as simple a fix as the timing wasn't set right, to as complicated of a fix as the engine wasn't machined right. But mere presense of a turbo being the culprit, I highly doubt. Have you given it enough miles to get the new rings seated in?
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i honestly dont think you can get somthing for nothing. if that was true then every diesel in the world would have a turbo. but theres plenty of diesel forklifts, road graders, generators, waterpumps etc that dont have turbos, even large equipment like my ford 4.4 liter i4 diesel power head has no turbo.
In my experience it's hard to come by any diesel engine made these days that's not turbo. Turbocharged engines are definitely more thermally efficient.
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Wow, thanks for all the info.
For best MPG lust use your na engine and pump. Add a turbo and don't turn up the fuel. Add a larger exhaust and use TD injectors. Install a cool air intake if you don't already have one. be sure your rings and valves are in great shape. Set the timing to turbo specs. Use stock size 13" tires.
So if I do this, should I use N/A or turbo pistons during the rebuild? Should I put on a hydraulic head or does it matter?
Thanks
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n/a pistons should work, as long as you don't up the fuel.
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NA pistons are cheaper and work fine for moderate fueling/heat levels. Where you need the TD pistons is at higer fueling on long pulls where the pistons have a chance to build up excessive heat. The TD oil jet carries this heat to the oil cooler and on to the radiator. The excess heat will cause excellerated ring, piston and cylinder wear.
Solid/Hyd head, no matter.
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You cant drop n/a pistons into a TD block because of the cooling jets. If you where to remove the jets... i dont know what would happen. Probably reduced oil pressure by quite a bit.
Turbo diesels are no doubt the most fuel efficient. Put it this way.... by the book... Golf mk4 stock 90bhp TDi = 55 mpg, 64 bhp SDi is about 48 mpg. Not only a big reduction in power, but also in fuel efficiency.
If you wanna go slow, a n/a diesel can be easy on fuel. My Jetta Eco does about 38 mpg... and thats driving it as hard as it possibly could be driven. You may as well call it a n/a diesel. The turbo is only there to increase air flow to reduce emmisions, not as a performance add on by any means.
(http://i18.photobucket.com/albums/b137/DieselMonkey/0643d364.jpg)
I heard somewhere that in parts of Austrailia its not legal to sell n/a diesels due to sparks that may leave the exhaust (fires in the bush). With the turbo, that spark stays in the turbine housing until it is no more.
If you want fuel efficiency, fit a small, wastegate turbo, de-fuelled pump, if the engine is in good condition in relation to oil pressure and ring sealing, run a light synthetic like Amsoil or Mobil 1 in both motor and tranny. Keep the car as light as possible at all times, 13" / 14" wheels (steels are generally lighter than alloys...not talking jap racing wheels here) and tyre pressure set correctly. If its got EGR, blank it off and reduce any load on the crank thats not necessary (air con, PAS etc..)
I ran 0W-40 in my 1.9D before fitting the turbo, for about 18 months. I ran that engine hard, and never any problems. Oil pressure now with 5w-40 Delvac is 110 psi at idle cold, so the 0w-40 didnt do any harm. Milage went from 480 miles to a tank, to about 550. It was a big difference, TDi's get even more impressive results.
Of course, direct injection is the only way to go for fuel efficiency, thats my next project.
regards, DM (below, picutre of my Jetta Eco.)
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You cant drop n/a pistons into a TD block because of the cooling jets. If you where to remove the jets... i dont know what would happen. Probably reduced oil pressure by quite a bit.
Turbo diesels are no doubt the most fuel efficient. Put it this way.... by the book... Golf mk4 stock 90bhp TDi = 55 mpg, 64 bhp SDi is about 48 mpg. Not only a big reduction in power, but also in fuel efficiency.
If you wanna go slow, a n/a diesel can be easy on fuel. My Jetta Eco does about 38 mpg... and thats driving it as hard as it possibly could be driven. You may as well call it a n/a diesel. The turbo is only there to increase air flow to reduce emmisions, not as a performance add on by any means.
(http://i18.photobucket.com/albums/b137/DieselMonkey/0643d364.jpg)
I heard somewhere that in parts of Austrailia its not legal to sell n/a diesels due to sparks that may leave the exhaust (fires in the bush). With the turbo, that spark stays in the turbine housing until it is no more.
If you want fuel efficiency, fit a small, wastegate turbo, de-fuelled pump, if the engine is in good condition in relation to oil pressure and ring sealing, run a light synthetic like Amsoil or Mobil 1 in both motor and tranny. Keep the car as light as possible at all times, 13" / 14" wheels (steels are generally lighter than alloys...not talking jap racing wheels here) and tyre pressure set correctly. If its got EGR, blank it off and reduce any load on the crank thats not necessary (air con, PAS etc..)
I ran 0W-40 in my 1.9D before fitting the turbo, for about 18 months. I ran that engine hard, and never any problems. Oil pressure now with 5w-40 Delvac is 110 psi at idle cold, so the 0w-40 didnt do any harm. Milage went from 480 miles to a tank, to about 550. It was a big difference, TDi's get even more impressive results.
Of course, direct injection is the only way to go for fuel efficiency, thats my next project.
regards, DM (below, picutre of my Jetta Eco.)
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In my experience it's hard to come by any diesel engine made these days that's not turbo. Turbocharged engines are definitely more thermally efficient.
I rented a small tracked Bobcat loader for work one day last year. It had a tiny 4 cyl diesel for power, with the smallest turbo I've ever seen. The whole unit was no bigger than a softball.
Would have fit nicely on my Norton :twisted: , but I think the rental guys would have noticed if it was missing :lol:
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Of course, direct injection is the only way to go for fuel efficiency, thats my next project.
What do you mean? Convert an IDI to DI? That would be a mod I'd like to see :shock: I'd also for sure want to try it myself -- anything to avoid all the electronics of the TDIs. While I admire the engineering that's gone into the newer engines, throwing parts and chips at them (even if I did have the money) to get better performance isn't my idea of fun wrenching.
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If you could get it working, it would sound like you threw a handful of bolts into the engine since there would be no progression with the fuel volume.
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No i mean a TDi motor running a Bosch mechanical direct injection pump. Over here its take your pick. I know of more than 5 different makes and models of vehicle with pumps suitable. Perkins where the first way back when they designed a 2ltr straight and turbo diesel for passenger cars. Performance was useless...i'll have the pump thank you... even has boost enrichment.
Simon cooper, who might frequent these boards has a 2litre (1.9 TDI bored) with mechanical pump. It looks like a 1.6 GTD pump but i doubt he could get the performance he is from a TDi using a small piston IDI pump. It does have methanol injection, Garrett roller bearing turbo and an aviation intercooler.
TDi engines with failed pumps can be bought for reasonable money. They last forever too, i've a 1996 1.9L with 165,000 miles and it has better compression and lower blow-by than both my IDI's. I have the ECU and g'box with that engine, but i want to try a mechanical DI. Probably get the same performance, just with more smoke.
Regards, DM