What's the ultimate IDI build for economy?

[Glegor]

Jer, you be on some crack...

[8v-of-fury]

Jer, you be on some crack...

bammmmmmmmm KEV lol

[theman53]

To be fair not every engine is 100% the same. The 15% is a general rule of thumb. Some could be 20% better than the next engine, as if I still had my flat red rabbit. The most I could ever get out if it was 44mpg and normal day was 40mpg, compare the average of the 2 and you are looking at over 20%. AND that would be a more honest evaluation as the flat red rabbit and the TDI had more similar mileage. My 86 jetta was completely redone engine and trans. Which eventhough its best was 48.53, once I intercooled it, the average tank was 45 to 46mpg...I never got a chance to do another freeway tank in the 7 months after the intercooler.

Then again, you may have a dud of a TDI and a gem of an IDI that are close to the same MPG and take it down to 5% once you figure the displacement and weight differences.

[Glegor]

yea.. tis true about mileage..

my engine gets 45+ in my mk2.. did even better in the mk1.

my GRANDPA barely gets 40mpg in his caddy, and he drives it like a GRANDPA.

[8v-of-fury]

To be fair not every engine is 100% the same. The 15% is a general rule of thumb. Some could be 20% better than the next engine, as if I still had my flat red rabbit. The most I could ever get out if it was 44mpg and normal day was 40mpg, compare the average of the 2 and you are looking at over 20%. AND that would be a more honest evaluation as the flat red rabbit and the TDI had more similar mileage. My 86 jetta was completely redone engine and trans. Which eventhough its best was 48.53, once I intercooled it, the average tank was 45 to 46mpg...I never got a chance to do another freeway tank in the 7 months after the intercooler.

Then again, you may have a dud of a TDI and a gem of an IDI that are close to the same MPG and take it down to 5% once you figure the displacement and weight differences.

Ahh, well that is a different ball all together. In proper tune, a DI will always be 15% more efficient than an IDI. It is the fact that the fuel is injected directly that makes it this way. However it is 15% more efficient in injection type, not overall and not all the time.

To make an IDI as efficient as a DI you need to do a lot of work, like VW did.. when they designed their DI engine

[Tinker Toy]

I agree that a DI might very well be 15% more efficient than an IDI due to reasons stated. VW did not stop with the conversion to DI and added a turbo to make more power to make acceleration acceptable to more people. The turbo pushes more air into the motor to permit more fuel to be burned to produce more power for better acceleration. The poor acceleration of an IDI would not do now for most people here in the US; never did.

Meanwhile under steady state driving, the turbo is making exhaust back pressure that the engine power must overcome by burning a bit more fuel. The DI part helps a little but not enough to make the fuel mileage as good as a simple IDI.

My view is that VW is also using the turbo to pump a little more air than needed for power to help with emissions. Otherwise this could be cut back for a little more fuel mileage due to less power loss from increased exhaust back pressure.

[theman53]

I think you are off a little. The MPG I was stating and should have added in my post more clearly is not a direct link to efficientcy. It is more of a side effect. The direct injected engine turbo or not is more efficient than the indirect injected turbo or not. Vw put turbos on the IDI but they had more back pressure than the VNT's they put on the TDI's. Overall the 15% comes from the way it processes the heat from the fuel. Pretty much 100% of the fuel charge is being used to push the piston back down. In the IDI it is flowing through the precup and not using all the energy to push the piston down. It loses heat and force to the precup, that is where most of the 15% comes from. That is why a car almost double the weight and .3L bigger on the engine normally gets better mileage than its smaller counterpart.

[Tinker Toy]

I agree that it is entirely possible that a DI would be 15% more efficient than an IDI for your reasons stated. Absent a turbo, that would mean that 15% more power would be produced from the same amount of fuel to also improve fuel economy but those gains are more than lost by the use of a turbo. Please keep in mind that an IDI does not have a turbo. With a turbo it would be an IDI TD, just so we are on the same page so to speak.

[8v-of-fury]

I don't know we are on the same page.. Lots of IDI have turbo's .. ?

This is a dead horse. Listen. Why would you want to run ANY diesel non-turbo, when so much is to be gained by having a turbo on there?

DI is superior to IDI. Volkswagen's TDI is superior to their older Diesel models. There is a reason they redesigned them . Better all around.

My 1.9 AHU M-TDI powered mk1 is way more fuel efficient then the exact same car with the 1.6 N/A I pulled out of it. Nothing changed but the motor.. Even using a bigger fuel pump, so technically I am even pumping in more fuel, but still more efficiently.

[theman53]

You are not clear to me. You are using terms in ways I haven't heard. This is to see if we are on the same page.

IDI= in direct injection.
DI = direct injection

The IDI was just called a TD when it has a turbo, for turbo diesel. IDI's most certainly had turbos.

Also, no efficientcy is lost with a turbo. Some backpressure is gained, but that is more than made up for in cool air pumped into the cylinder. This effectively makes a smaller engine bigger as you can put a bigger engines air volume into a small engine space. That otherwise a small engine couldn't pull in on its own ie. without the turbo an N/A can only pull in its own cylinder volume per rpm.
Also, turbos use the exhaust heat and flow to spool. You are not pulling on the rotating assembly like a supercharger. Turbos are using what the engine makes as waste to power itself. In essence it would be like eating your own crap and being able to lift more weights in the weight room, nothing else changed. I hope this is more clear but your idea of a turbo isn't correct sir. The turbo does not decrease efficientcy. With the LDA operating properly and you are not over fueled for any driving situation, with a turbo you will have more oxygen to burn the diesel more completely, thus more power, efficientcy, and usually mileage.
The problem is most with a turbo cannot hold their right foot where it used to be and use the extra power all the time. That said of the 6 N/A rabbits I had and the 1 TD mk2 jetta I have had only 1 rabbit got better mileage than the Jetta. I had a few tanks of 53mpg in that rabbit, fuel was LSD then so maybe that was the deal, on average though it was only 1-2mpg better.

If I am off please explain where you are coming from.

[Tinker Toy]

This thread is about fuel economy. Additional diesel fuel must be burned to run a turbo which is contrary to improved fuel economy. The use of the term "efficiency" is not appropriate as efficiency can include both fuel economy and engine power output.

[libbybapa]

Increases in efficiency DO translate into better fuel economy IF similar acceleration rates and cruising speeds are used. A turbo improves efficiency. The turbo recovers heat from the exhaust and turns that heat into work. Driven at the same acceleration rates and speeds, a turbo will improve fuel economy. Most people don't see an increase in fuel economy, tho because they drive faster, especially on hills. If you want 'ultimate' fuel economy from an IDI, then intercool it and turbo-charge it and DETUNE the pump so that it doesn't have any more power than a non-turbo. If you want 15% BETTER fuel economy, do the same things with a TDI.

[theman53]

This thread is about fuel economy. Additional diesel fuel must be burned to run a turbo which is contrary to improved fuel economy. The use of the term "efficiency" is not appropriate as efficiency can include both fuel economy and engine power output.

Wrong sir, just as we have stated no extra fuel needed to spin a turbo. If all you did was bolt a turbo onto your car and not touch the pump it will run better with the same fuel you have. Like I said it is wasted engine heat you engine already made to run, you are just reclaiming it. Again, drinking your own piss to rehydrate and run faster, or eating your own crap to lift more would be a suiteable analogy, but it won't happen that way on a person...taking waste and making it work a second time with no extra fuel.

[Tinker Toy]

Like I said it is wasted engine heat you engine already made to run, you are just reclaiming it.

NO! A turbo does not run due to high temperature. It runs from exhaust gas pumped out of the engine by the pistons; gas that happens to be hot.

[Glegor]

NO! A turbo does not run due to high temperature. It runs from exhaust gas pumped out of the engine by the pistons; gas that happens to be hot.

a turbo wont spool right unless the air is hot, and expanding..

the EXPANSION OF EXHAUST GASSES is what drives the turbo..

so, you were both right..

[libbybapa]

NO! A turbo does not run due to high temperature. It runs from exhaust gas pumped out of the engine by the pistons; gas that happens to be hot.

http://bit.ly/O8RQC4

Perhaps some of your confusion stems from thinking we are talking about gasoline engines which, unlike diesels, require a specific mixture. Even so, a proper turbo installation on a gasoline engine will also increase fuel economy provided similar acceleration rates and cruising speeds are used.

[theman53]

NO! A turbo does not run due to high temperature. It runs from exhaust gas pumped out of the engine by the pistons; gas that happens to be hot.

Look up...reply 45 of the thread...I stated that it was flow and heat, without both you will not spool the turbo. I didn't feel the need to type it again when I had said, "like I said already". I didn't figure you were actually reading it anyway.

I am not trying to fight with you I am trying to help you out in your quest to knowing it all.


Then you can teach me the rest that I don't have, as I look up to you.

[rabidroco]

Would it be possible to run a TDI head on a 1.6 block/pump etc? I like the idea of direct injection but do not want to mess with the electronic crap.

[theman53]

Would it be possible to run a TDI head on a 1.6 block/pump etc? I like the idea of direct injection but do not want to mess with the electronic crap.

Yes and no. It has been discussed many times. No one makes or will for any reasonable amount a piston for it. Also, you would need rods if the pistons didn't match up. Meaning you could buy a 1.9 and convert it to M-TDI for less money...ask 8v on that. But yes, you can bolt an AHU head to a 1.6. Also, a pump would need built.

[libbybapa]

As far as I could determine, the 1.2 TDI pistons actually fit the 1.6 rods/bore and have the proper pin height. Unfortunately they are PRICEY. With that consideration along with the fact that if you detuned a 1.9TDI to the power levels of a custom 1.6TDI, you'd achieve similar fuel economy, there really isn't any advantage to the reduced displacement especially when you can now get 1.9TDI engines for fairly cheap.

[8v-of-fury]

Ask 8v on that...

I broke even and damn near almost made profit on my M-TDI swap in to my mk1 .

With the time and money spent on a 1.6 DI engine out of an old 1.6 IDI block and 1.9 DI head.. You could easily pay someone to do a 2012 2.0L Common Rail full electronics and everything swap .. probably not, but it would come close after having an entire rotating assembly made from scratch!

You can easily and pretty readily convert the 1Z/AHU engines for a direct mechanical swap in to an mk1 or mk2. The ALH's are a little trickier as the block designs were different though.

NO! A turbo does not run due to high temperature. It runs from exhaust gas pumped out of the engine by the pistons; gas that happens to be hot.

What is the difference? If I coast down the hill with my engine at 2500rpm in gear, I can barely hear my turbo. Keep in mind there is still 4 cylinders worth of hot air spinning the turbo. If I push the fuel pedal I can easily hear my turbo jump up and scream to life. I have maybe increased my rpms by 100-200. There is only slightly more air flowing through the turbo, but it is WAY HOTTER because now I have added fuel to the cylinders.

[Glegor]

I broke even and damn near almost made profit on my M-TDI swap in to my mk1 .

With the time and money spent on a 1.6 DI engine out of an old 1.6 IDI block and 1.9 DI head.. You could easily pay someone to do a 2012 2.0L Common Rail full electronics and everything swap .. probably not, but it would come close after having an entire rotating assembly made from scratch!

You can easily and pretty readily convert the 1Z/AHU engines for a direct mechanical swap in to an mk1 or mk2. The ALH's are a little trickier as the block designs were different though.



What is the difference? If I coast down the hill with my engine at 2500rpm in gear, I can barely hear my turbo. Keep in mind there is still 4 cylinders worth of hot air spinning the turbo. If I push the fuel pedal I can easily hear my turbo jump up and scream to life. I have maybe increased my rpms by 100-200. There is only slightly more air flowing through the turbo, but it is WAY HOTTER because now I have added fuel to the cylinders.

the difference is HEAT..

your EGTs are like 250* while coasting, and like 800 once you get back on the pedal..

EXPANSION OF GASSES..

without expansion, the turbo would never lite..

[Tinker Toy]

a turbo wont spool right unless the air is hot, and expanding..

the EXPANSION OF EXHAUST GASSES is what drives the turbo..

Keep in mind that the exhaust pressure to run a turbo is at the same time exerting a reverse pressure on pistons attempting to pump exhaust gases out. Without the resistance due to the turbo, the reverse pressure on pistons would be less.

I read the Wiki article on turbos. It assumes that driving technique will be altered to use low revs to increase fuel economy. That may be possible but as a reality, it will likely not happen that way. Also, injecting more diesel fuel than a naturally aspirated engine can burn will be repaired with a turbo that will bring more needed oxygen but the fuel economy will not be more than with no turbo.

[8v-of-fury]

Keep in mind that the exhaust pressure to run a turbo is at the same time exerting a reverse pressure on pistons attempting to pump exhaust gases out. Without the resistance due to the turbo, the reverse pressure on pistons would be less.

Well yeah, but the gains more than offset the back pressure caused. Possibly the reason more than most diesels are boosted.. .

I read the Wiki article on turbos. It assumes that driving technique will be altered to use low revs to increase fuel economy. That may be possible but as a reality, it will likely not happen that way. Also, injecting more diesel fuel than a naturally aspirated engine can burn will be repaired with a turbo that will bring more needed oxygen but the fuel economy will not be more than with no turbo.

If you didn't change anything but add the turbo, fuel injected will remain the same but you will do so more efficiently and therefore in turn actually be using less fuel for amount of kilometers driven. You will only use lower revs if you have put on a turbo charger that will spool at low rpms, like a k03 or k14 off of an AAZ motor. They spool at 1800 and like 2200 respectively. The stock 1.6 turbo, the T3, spools more around 25-2600 and provides 10-11psi when fully spooling. At the same RPM as a non turbo motor, it is more efficient.

Engine efficiency directly translates to better mileage. Why do 1.6 Diesel engines easily get 50mpg when their EXACT 1.6 Gas counterparts struggle for 30mpg? The answer? Thermal efficiency and energy dense fuel.

[Tinker Toy]

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA542327

Quote: "The main findings of the study are as follows:

As the back pressure increases, the engine must work harder to pump the gases out of the cylinder against the higher pressure. The pressure ratios across the turbocharger compressor and turbine decrease, reducing the mass flow of air through these components and thus the air available to the engine. At the same time, the fuel flow must increase to provide the extra power necessary to overcome the increased pumping losses while maintaining a constant brake power output. As a result the brake specific fuel consumption increases above that for an engine operating in atmospheric conditions." Unquote.

[8v-of-fury]

Ok, explain to me why all of us in real world testing.. seem to get better mileage with our turbo equipped engines?

/nuff said

Theory is just that, Theoretical. Practical>Theoretical every time.

[libbybapa]

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA542327

Quote: "The main findings of the study are as follows:

As the back pressure increases, the engine must work harder to pump the gases out of the cylinder against the higher pressure. The pressure ratios across the turbocharger compressor and turbine decrease, reducing the mass flow of air through these components and thus the air available to the engine. At the same time, the fuel flow must increase to provide the extra power necessary to overcome the increased pumping losses while maintaining a constant brake power output. As a result the brake specific fuel consumption increases above that for an engine operating in atmospheric conditions." Unquote.

LOL! Dude, you are funny! Did you actually READ the article you linked? Obviously not, or else you are just trying to deceive people. It is about using diesel engines in submarines in the late 1930's. The back pressure being discussed in your quote has nothing to do with the turbocharger. The back pressure they were studying was caused by the engine pushing the exhaust through a snorkel which had a variable depth of water in it. I've rarely seen such a misused and deceptive quote outside of political or religious propaganda.

While that linked study is a strong argument for a free flowing exhaust system AFTER THE TURBO, it says nothing about the effect of the turbocharger itself on fuel economy or efficiency and the fact that you used it to say so in this discussion shows either a significant lack of understanding on your part or a desire to deceive others. Either way it's both funny and disturbing.

As far as your theory that a turbocharger simply causes back pressure and so requires added fuel to operate, that is also a highly deceptive and limited view. While the turbo does introduce increased back pressure, it also introduces increased intake pressure. While the exhaust back pressure is trying to push the piston back up, the increased intake pressure on the 'other' piston is pushing the piston down. While EMP is more than IMP, that is because the total gases in the engine expand during combustion which is what powers the whole system. The final effect of adding a turbocharger is that the exhaust AFTER the turbocharger has reduced waste heat because the turbine has recovered that waste heat and turned it into useful work increasing engine efficiency (and fuel economy provided similar acceleration rates and cruising speeds are used).

[theman53]

My IDI has a turbo, but after that no muffler...any restriction I added with a turbo would be negligable as I don't have the muffler. Try running your N/A without a muffler and see how many seconds it takes before you get pulled over. With your reasoning we probably have the same ammount of back pressure. Turbo is the most expensive muffler you will ever buy. It is nice and quiet too.

I think your submarine info should have remained classified, LOL.

[rabidroco]

[dodger21]

Turbos certainly do create back pressure that can negatively affect fuel economy. Try swap exhaust housing sizes and see what happens.

I got better mileage in my 300k mile MK2 1.6NA than my brothers 150k mile MK4 1.9 TDI.

In my diesel truck, the 18cm (A/R close to 1.1) exhaust housing is considered very big for the turbo. I get somewhere around 18-20 with the best ever being 23.2 on a 500 mile trip. Spool doesn't happen before 1900-2000rpms. My buddy who has the same center section but bigger 60mm compressor and a tighter 12cm exhaust housing as my turbo, with smaller tires, only got 14mpg on that same trip.

Both trucks were have nearly the same setups. 5spd, reg cab, long bed, 4x4s, manual. I had 33x12.5" tires, he had 31" equivalents. I had 4.10 and he had 3.55 gears. Fueled at the same station when we left. On paper, his truck should have gotten a lot better than mine.

Exhaust heat helps to spool the turbo at lower rpms. However, you can spool a turbo with RPM's alone. Heat just helps to drive it. If all you thought you needed was 1000rpms and a ton of heat, stick a blow torch in your exhaust manifold to help spool your turbo. Please report back with pictures.

OP, I planned on something like this before I parted my car. Major things to consider on a stock engine is weight and resistance. Thing that will help are aluminum wheels, skinny tires, lowering the car, custom front air dam, air flow THROUGH the engine bay (giant parachute. things like SCCA vents), lowering your weight, better 5th gear, light foot, a properly tuned engine, bigger exhaust with as little restrictions as possible, polished intake, ported exhaust, better air filter, add a 15psi electric lift pump, under drive pulleys.

Things to think about.

[theman53]

Look up...reply 45 of the thread...I stated that it was flow and heat, without both you will not spool the turbo.

Yes, turbos are a restriction, but your test has way too many variables and unknowns. Were both speedos spot on? Were both IP's putting out the exact cc of fuel? If it was hilly terrain you would fair better with 4.10's than his 3.55's. Also if he had a more aggressive tire for mud and snow and yours was less aggressive that would contribute to some MPG difference. Were they the same 5 speeds or different ratios. Was one a 1/2ton and the other a 3/4 or 1 ton? If you didn't stop as much and continued rolling the taller tire is supposed to help with fuel mileage on long trips. Did both setups have the same non dragging brakes? Did both have the same mileage on the trucks? Also, his probably had more HP if he used that more fuel or was operating with an engine in its peak torque range from the gear and tire setup you could have been under...etc there is way more than turbo difference.

The ony good test would be to put his turbo on your truck and yours on his and take the same trip again, same temps, same loads. Different engines do different things sometimes and doing the same mods to 5 different engines/trucks won't have 100% the same results. But to say his turbo was the only reason is a bit out there. Not saying it wasn't as it could be way too small for the engine or for the way he used the engine that day.

[dodger21]

Both trucks were completely stock 3/4 tons except the turbo. I should also mention he had a stock AFC pin but I had a really aggressive DennyT stage 2 pin where I got full fuel by 10 psi. I have no idea if his pump was tuned or just turned up. I tune mine at the race track.

Mine were mud terrains, his were AT's. You really are grasping at straws. I am saying, no matter what, unless PROPERLY setup (which the 1.6L NA pump really never was), then it will cause a restriction at highway/road speeds.

[8v-of-fury]

I am saying, no matter what, unless PROPERLY setup (which the 1.6L NA pump really never was), then it will cause a restriction at highway/road speeds.

On the contrary, the NA pump will flow the same amount of fuel as the TD pump. It also can achieve the same economy or power if all you changed was the pump from 1.6TD to 1.6 NA.

[theman53]

Big huge differences then...

I tuned car/truck with a diesel everywhere I have seen will usually get better mileage than a non tuned one driven accordingly. If you are making better power and your engine is breathing better you don't have to give it the fuel that he would.

I have a neighbor with a 12v cummins in a 1/2 ton truck *many non 1/2 ton parts* that dynoed rught under 400hp and he gets close to 22mpg around here when he drives normal. He gets about 10 when he is ripping on it. He has the same turbo on in either situation, drive style makes a huge difference.

Like I said the only way for your claims to be accurate would be to switch turbos and do the same run agian, without making any other changes.

[libbybapa]

The compression stroke similarly pushes against crankshaft rotation and similarly if you remove compression your engine efficiency will go in the toilet hurting both power and fuel economy. The analogy is very apt.