34MPG in a 2002 Grand Cherokee diesel

[Logic]

Originally Posted by AdrianD

The front lip is a bit of a liability, it gets damaged very easily but it also needs to be ok in the looks department and rubber won't cut it

Ye; conveyer belting will deform and spring back, no problem, but getting it to look good isn't easy. Doable, but not easy.
This is the kind of thing where you might keep an eye out on other cars for a lip you like that might be made to work.

Originally Posted by AdrianD

As for bell mouths, surprisingly, the pipe going from filter housing to turbo inlet has a really nice bell mouth. There might be some improvement in the factory "snorkel", which has a flap over it to prevent water ingress at speed but it's right at a corner of the grille.

Glad to hear there's a bell mouth in the filter box exit!
Bit late now after all the stripping, but pics reqd of that snorkel and where is sits before we can have an opinion on it.

Originally Posted by AdrianD

Surprisingly, Jeep took good care of air getting in the turbo but not so much the air getting out:
- factory turbo has a large "chamber" after the turbine outlet, which narrows down a lot at the actual turbo outlet.

That chamber is likely a way to kill the swirl flow from the turbo outlet, so you may want to keep that bit.

Originally Posted by AdrianD

- exhaust necks down from 2.5" to 2.something in several places
- muffler is very restrictive, with little benefit in noise, I'm running a straight-through muffler now and, to the ears, the exhaust is just as loud as factory.

The "necks down" in a couple of places is ok as long as it necks up again soon after and the necking is gradual.

Which, of the 4 mufflers are we talking about?
There's that shared one, then another 2 per pipe, or is this some other muffler and not the one in the pic?
Did you notice an improvement from the 'Free-Flow' muffler?

Originally Posted by AdrianD

Planned mods:
- possibly larger tires which are down 3 points in the EU tire label economy compared to current ones. Still narrow, just more sidewall. I will do some testing, maybe I can gain some economy at the cruising speed (105-110km/h)
- air/water intercooler - it will happen, just not sure if I can manage before the trip
- cleaning the intake manifold (it has a lot of deposits from EGR) OR installing a manifold which promotes equal airflow to all cylinders

Sounds interesting. Enjoy!

[AdrianD]

Originally Posted by Logic

Glad to hear there's a bell mouth in the filter box exit!
Bit late now after all the stripping, but pics reqd of that snorkel and where is sits before we can have an opinion on it.

It's visible from the grille, I will take a photo of it.

Originally Posted by Logic

That chamber is likely a way to kill the swirl flow from the turbo outlet, so you may want to keep that bit.

It's on the exhaust side, barely visible here:


The engine pulls harder in the higher rev range after the turbo upgrade without any fueling changes in the ECU.

Originally Posted by Logic

The "necks down" in a couple of places is ok as long as it necks up again soon after and the necking is gradual.

Which, of the 4 mufflers are we talking about?
There's that shared one, then another 2 per pipe, or is this some other muffler and not the one in the pic?
Did you notice an improvement from the 'Free-Flow' muffler?

There's only one muffler on the diesel. After the exhaust mods, the engine pulled from lower revs without downshifting.

[cRiPpLe_rOoStEr]

Originally Posted by AdrianD

cleaning the intake manifold (it has a lot of deposits from EGR) OR installing a manifold which promotes equal airflow to all cylinders

If you replace the intake manifold, maybe that would be an excuse to also add a water injection setup, as it would be useful to decrease carbon buildups from the EGR. Not only due to its benefits to the combustion process, but also due to it preventing oily vapours from the crankcase breather to stick to the manifold.

[AdrianD]

I was planning on water/meth injection, maybe if the air-water intercooler doesn't manage to keep temps low
EGR is disabled, so if I clean the manifold, it will stay clean.

[Logic]

Originally Posted by AdrianD

I was planning on water/meth injection, maybe if the air-water intercooler doesn't manage to keep temps low
EGR is disabled, so if I clean the manifold, it will stay clean.

For spark ignition:
Water injection (after intercooler) decreases performance economy
UNLESS
you run higher compression/boost, as the increase in compression increases efficiency way more than the water decreases it.

ie: You add the heat that evaporation removes back with more compression.

https://www.youtube.com/watch?v=jextyKc2UN4

[cRiPpLe_rOoStEr]

Originally Posted by AdrianD

I was planning on water/meth injection, maybe if the air-water intercooler doesn't manage to keep temps low

The intercooler, as long as it's sized accordingly, will keep temps low enough. And it's always safer to have the intercooler sized properly, instead of having to rely on water+meth injection on normal driving conditions.

EGR is disabled, so if I clean the manifold, it will stay clean.

Sure. But anyway, as water+meth tends to avoid those oily vapours from the crankcase ventilation to stick to the manifold, it would be useful to prevent dirt from accumulating. Just like some newer gasoline-powered cars feature a double injection (port and direct) instead of only direct injection, as it prevents carbon buildups around the valve seats.

[Logic]

Originally Posted by cRiPpLe_rOoStEr

The intercooler, as long as it's sized accordingly, will keep temps low enough. And it's always safer to have the intercooler sized properly, instead of having to rely on water+meth injection on normal driving conditions.

Yep, but an intercooler can only take temperatures down to ambient. (ideally)
Water injection goes WAY cooler than that, thx to both evaporative and plain conductive cooling with its high specific heat capacity, allowing the use of high compression and high compression = efficiency.

While the methanol is a fuel is only really needed to stop the water from freezing and popping the pipes etc.

https://www.youtube.com/watch?v=jextyKc2UN4&t=582s

[cRiPpLe_rOoStEr]

Originally Posted by Logic

While the methanol is a fuel is only really needed to stop the water from freezing and popping the pipes etc.

Sure, and most likely ethanol can be used for the same purpose. On a sidenote, besides ethanol being available at most fuel stations in my country, it can also be homebrewed

But if a homebrewer would eventually try to make ethanol at home, and willing to have a sip too, care must be taken during fermentation, to avoid turning it into methanol instead of ethanol.

[Logic]

Originally Posted by cRiPpLe_rOoStEr

Sure, and most likely ethanol can be used for the same purpose. On a sidenote, besides ethanol being available at most fuel stations in my country, it can also be homebrewed

But if a homebrewer would eventually try to make ethanol at home, and willing to have a sip too, care must be taken during fermentation, to avoid turning it into methanol instead of ethanol.

Making ethanol with rotten fruit and veg is something everyone should do and would do if they knew how easy it is. ("But that takes 10 mins of research! NOT happening!!")
Why just toss it out..!?
I think most modern cars' ECU's simply compensate for whatever mix is in the tank since the advent of E85.

And if your fuel doesn't work (too much water) it doesn't matter because you're too pissed to care!

[AdrianD]

Latest updates:
- reduced commanded torque converter clutch slip in the cruising RPMs from 50rpm to 25rpm
- cleaned the intake manifold and removed the swirl flaps (2 ports / cylinder, one promotes swirl and the other is straighter and can be closed by the ECU).

Before removing the swirl flaps I did an offroad trip with larger tires, 31" vs 29", got a MAF error and the limp mode keeps the swirl flaps open. The car pulled at low revs the same as it did with smaller tires and functional flaps. And I only noticed the open flaps after I checked what happens with the MAF limp mode.

After swirl flap removal and some timing increase at cruise, the turbo vanes are less closed (60% duty cycle before the mods vs 50-52% after) at the same RPM and injection quantity which makes me think VE should have gone up.

I also did a long trip on the highway but unfortunately had serious head-wind both ways. Going away, the wind socks were horizontal and pointing mostly towards the car, I could even see small trees bending from the wind.

First tank was 670km on the highway with 20+km/h winds and 105km/h on the GPS and 40km of flogging in Budapest traffic, fuel consumption was 8.52L/100km or 27.6 MPG.

Not very far from last year's trip (7.96L/100km or 29.54MPG), when I did not have head wind and did not drive in Budapest traffic.