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

[COcyclist]

Originally Posted by Arragonis

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.

[Arragonis]

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

[ConnClark]

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

[Piwoslaw]

Part 5 is out - intercooler and conclusion

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

So if there was no power increase, was the fitting of the larger intercooler a waste of time? For two reasons, I don’t think so.

Firstly, the fuel economy is clearly improved. This change is not visible in all driving: it seems more pronounced at higher speeds where loads are greater. In Part 4 of this series I said that typical fuel economy had improved to about 5.3 litres/100km. That is still the case in most circumstances, but in freeway use at a sustained 110 km/h, 5.1 litres/100km is now common.

[Piwoslaw]

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.

[ConnClark]

Originally Posted by Piwoslaw

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.

[Arragonis]

Originally Posted by Piwoslaw

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.

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.

[COcyclist]

[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.

[Arragonis]

Originally Posted by COcyclist

Arragonis, are you suggesting the improved mpg is just the result of the flash too?

In this case, yes.

The wine is in my garage (aka wine cellar ) 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.



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

Originally Posted by COcyclist

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.

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.

Originally Posted by COcyclist

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.

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 ) 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.

[JasonG]

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.