1.9L VW/Audi/Skoda/SEAT Diesel Mod alert! :)
 

Autospeed has a new series on modding the 1.9L TDI. The first part covers taking base measurements.

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They tend to be performance oriented, but if you do everything they do to a diesel except turn up the fuel you'll get better economy and power too :thumbup:

It actually turned out in the end to be a lot more complex than just power vs fuel economy but the end result is good in both.

Julian,

I'm sure it did turn out to be more. I was just noting that for people here in this forum, they might want to avoid the turning up the fuel step to maximize economy. (I know you can get the same economy if you keep your foot out of it but if the temptation isn't there ... )

Thanks for the great articles.

As the series will (eventually) reveal, fuel economy improved after the remap.

Looking forward to the next part on making your own intake. Did you look at the PD 160 intake as this can be a direct drop-in replacement and it has much less of a change in diameter from the intake panel to the pipe.

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

I'm also looking forward to seeing if this improves performance. Some people on Briskoda have claimed all sorts of benefits from the PD160 one including increased power, more responsiveness and greater sexual attractiveness - but with no hard data.

Nice article:thumbup: Waiting for more to see what I can try on my HDi.

Yes looked a this. Very expensive locally.

Without giving away too much, I can say that the new intake flows very well and the impact on car performance was interesting!

Looking forward to seeing that one then. The intake is spendy, over £90 here including VAT. It was under 50 until SEAT dealers realised they could make extra money.

New intake cost very little - maybe AUD$30

Julian,

Very strange results from your latest installment. It goes contrary to everything I have ever read and experienced with a diesel. Numerous papers and test stand experiments show that a diesel with a leaner mixture ( more air and using the same amount of fuel ) produces more power.

With the lower pressure drop on the intake there will be a higher pressure in the rest of the intake. This would reduce the amount of EGR that can be used. I'm betting that the emissions computer is restricting fuel to limit NOx.

Certainly not what I understand to be the case. Can you produce some references?

One very informative paper I keep referencing is

http://aerade.cranfield.ac.uk/ara/1937/naca-tn-619.pdf

in figure 8 they show power output with boost pressure for fixed fuel increments per cycle.

In figure 10 they show what a restriction of air intake does to performance.

in both cases the more in the cylinder results in more power out and higher efficiency for a given quantity of fuel.

@Julian

I've been waiting for this since part 1 :thumbup:

Briskoda had a 'definitive thread' on the PD160 a while ago. Lots of "yeah much faster" but no solid ABA testing and then repeating this with a remap I could see. So I saved the cash. I did plan on a remap without it but didn't go through with it although I do have an uprated clutch fitted.

As for yours, dissapointing results so far especially given the effort involved and the improved flow. I await the exhaust and remap installments though.

Are you planning to test the remap without the intake and exhaust, as in full on A-B-A to see the effect of flashing alone ?

no

I like old engineering but I think that referencing a 1937 paper as indicative of how a current diesel behaves is stretching things a bit. What engine speed was used? What compression ratio? How well was the fuel atomised?

I actually wasn't disappointed at all. I thought the pressure drop improvement was very impressive.

It seems to be a paper about testing compression engines at different altitudes. 2000 rpm was the speed quoted. It used roots type superchargers too.

Julian, at the end of the second part of the article, there is a graph of acceleration vs rpm for the standard and the new intake.


Do you have any idea why acceleration wasn't better through the whole rpm scale, but was actually worse below 1500 and above 4000rpm, even though the pressure drop was greatly reduced? Would this imply that just swapping the intake for something larger would harm performance and/or fuel economy when the driver's style keeps rpms between 1000 and 2000?

The pressure drop is good. I meant the accell tests.

Just a thought, is the standard intake plenty for a 1.9 litre engine only revving to 4500 rpm? If it was a petrol screamer then maybe that would release more power with this mod.

Also do you have any idea of increased boost pressure actually reaching the engine ? I'm wondering if the turbo / relief valve combination more or less sets the boost level at WOT no matter how much extra air the intake is allowing. If you restricted the intake then that would have a negative effect obviously.

One of my first ecodriving techniques with my current car, was to ever so gently reduce the throttle. It kept up the speed (sometimes it'd lose 1 or at worst 2 mph), but fuel consumption dropped significantly, and well beyond what you'd expect from a 1 or 2 mph drop in speed.

So it made the same power on less fuel, i.e. by leaning it.

It was rather tricky to reduce the throttle, as overdoing it meant the speed dropped like a stone, and any bump could change the position of my right foot, often ruining the whole thing.

As far as I can see, the cruise control seems to do something similar, but far more consistently, and with a lot less effort on my part ;)

I've tapped this elsewhere but maybe worth it here.

One of the techniques on older NA diesels (Pug 205 - where are you now ???) was to balance throttle against what the engine could make use of in terms of fuel. The theory was that if you overdid it, the effect was like smothering a fire with too much material. What you needed to do was balance it against usage to get the best. There was definitely a point where you got no more benefit from either higher revs or more throttle vs easing back and changing up.

As I understand it a turbo kind of reverses this - there is always too much air for the fuel being injected - unless you use the old fashioned (rotary pump) trick of turning up the fuel. That gave you more power but at the expense of smoke from the less than efficient burning fuel.

My idea for this is explained in the article.

I have made a slight change to the story, based on material on page 60 of the Bosch publication Diesel Engine Management (3rd edition), 2004, which covers power and fuel injection mass.

OK, I went back and studied the graph and text again, and I see that I was in error! Acceleration is actually better below 1500 rpm than with the stock intake. The y-axis of the graph is in g's, not in seconds, as I had thought.
My bad, terribly sorry about that.http://ecomodder.com/forum/member-pi...660-master.gif

Crossposting:
Diesel mods and testing

That homemade intake was my favorite part :) pvc, sacrificial coolies, and tape...

...and a cherry picker, and some vice grips and a wooden plug :)

http://autospeed.com/cms/A_112211/article.html

Part 3 is out on this series. Browser Warning

Its amazing how the ECU keeps making performance worse and worse by starving the engine of fuel. Even so I still think that mileage should be up though.

Part 4 is out with nice results. Fuel economy "appears" to have improved by 5% with a nice increase in power.

http://autospeed.com/cms/A_112228/article.html

Here is the link Browser Warning

I suspect that if you have a custom remap to a 1.9 TDI you would get these results even without the other changes.

I wish Julian had tested this theory too. It wouldn't be that hard for a handy guy like him to put it back to stock except for the tune.

Its a shame, still looking forward to the intercooller episode though. :D

I found a much more recent paper that discusses how boost effects BSFC and emissions than the old NACA papers.


http://www.erc.wisc.edu/people/facul...99-01-0840.pdf

Part 5 is out - intercooler and conclusion

Fitting a larger IC seems to have brought performance down again, but has improved fuel economy.

I've been thinking about the freer flowing intake today. I don't know about the TDI turbo, but my HDi's turbo has variable geometry, and this lead me to a thought experiment:
The ECU is constantly checking boost pressure and tweeking the turbine's geometry to keep boost where it is supposed to be. So if the pre-turbo intake is opened up (less restrictive = lower pressure drop = higher pressure delivered to turbo) the ECU adjusts geometry to 'scoop up' less. Post-turbo pressure is the same (ECU made sure of that), but the turbo is doing less work, i.e. less work is extracted from the exhaust.

So, opening up the pre-turbo intake has the same effect as reducing exhaust back pressure. And is probably cheaper.

On some cars that would be totally correct. Unfortunately for modders, some emissions control units utilize the turbine vane control to keep exhaust back pressure high to promote EGR flow. When the ECU tries to maintain X amount of boost with less pressure across the turbine, the EGR percentage drops and this change is picked up by the O2 sensor. Thus the ECU throws everything out of whack to try and keep emissions down and you can't always be sure what the results will be.

You may still get a little better mileage as Julian noted, but you could brainwash the ECU and make it better.

Some how we have to get Julian a 1985 Mercedes 300CD turbo. He would like that. The ECU controls an air recirculation valve and the EGR valve and that is it. Fuel is controlled by your foot and the amount of boost pressure you have.

TDIs have VNT turbos.

My thoughts have led me to conclude this won't work. The inlet side is cancelled out by the turbo - it boosts to the same pressure as long as enough air is coming in. If you improve it then it makes no difference.

The same for the exhaust - remember better exhaust flow only works for high-revving petrol cars. The exhaust diameter on my TDI is larger than any petrol car I have ever had.

Nope - this engine has all the air it needs. I still maintain if Julian removed everything else and kept the remap the power gains would still remain.

I'm willing to bet a bottle of wine on it.

[QUOTE=Arragonis;227360]TDIs have VNT turbos.

My thoughts have led me to conclude this won't work. The inlet side is cancelled out by the turbo - it boosts to the same pressure as long as enough air is coming in. If you improve it then it makes no difference.

Nope - this engine has all the air it needs. I still maintain if Julian removed everything else and kept the remap the power gains would still remain.

I'm willing to bet a bottle of wine on it.[/QUOTE

Arragonis, are you suggesting the improved mpg is just the result of the flash too? I have been studying up on diesels and everything suggests that turbo-diesels do best with free flowing intake and exhaust. This is at odds with Julian's findings though. I hacked off my muffler a few years ago and replaced it with a 2 1/2" straight pipe. I cannot say that it changed the power at all but it certainly didn't hurt my highway mpg.

In this case, yes.

The wine is in my garage (aka wine cellar :D) waiting to be shipped - its not an "expensive" bottle (Lindemans 2010 Chardonnay) but I am willing to put my money (and bragging rights) where my keyboard is. This is for road cars only. :D

http://images.connectselect.co.uk/im...AY_250x460.jpg

I am no engineer and am willing to be proved wrong. Only once though, not everyone gets wine - only Julian or the 1st proof maker :D

My belief is that this engine (TDI 105 I think) has all the air it needs. There is nothing to be gained by the intake or exhaust mods.

For example are there A-B-A MAP (Manifold Absolute Pressure) readings to record any additional air actually reaching the engine ? I would hypothesise that there would be none.

It didn't hurt but did it help ? I think you are in the same boat as this car - your car has all the air it can take. If you want more MPG it will come from technique. If you want power it will come from a remap.

A bit of background here. When I was young and daft (aka long ago for the former and last week for the latter :D ) I "tuned" an old school IDI turbo diesel in the form of a Peugeot 306 brand new company supplied car. The classic technique was to "adjust" (i.e. enrichen) the fuel pump until the the smoke appeared and then go "half a turn" back, but only if it was the Bosch pump. If it was Lucas you were out of luck.

It worked, my 306 XRDT was much faster but didn't use noticeably more fuel. I have no idea about how long it lasted because I left that job when it had 70K on the clock and it was still fine then and the dealer had serviced it at least 5-6 times without noticing.

I love diesels because they are simple creatures.

More fuel = more power.
Less fuel = better MPG
Too much fuel = smoke » add air

My last (no trailer) tank was 19 MPG. No cat, 15 yr old (hollow) muffler.
I upped the pump till it smoked, then added boost (air) to clear it.
167K miles and still pulls that beast up hills with the rare downshift.

Julien's problem is he added air but no more fuel. The TDI simply adjusted the metered volume to match the airflow and load. Now, had he installed bigger injectors the outcome would be vastly different.
Diesels don't work off of a 14:1 ratio, nor do their computers attempt to maintain any set mixture. More pedal = more juice.

Go to Fred's TDI Page. TDIClub.com. VW TDI Enthusiast Community and look through the more power section of the FAQs. See much mention of bigger air passages??? Raising the boost is only to control smoke, to burn the extra fuel that you have added.

The inverse reason is why EOC is of little benefit. The engine nearly cuts fuel when coasting. DFCO? WWII diesels had it. Years back a trucker told me it took less diesel to low idle for half an hour than it did to start back up.

Sorry, where were we...... oh yeah.

Bottom line, diesels are very different from gassers. Or before someone nitpicks, injection ignition engines bear little resemblance to spark ignition engines. :rolleyes: