Reports: 2014 Fiesta 1.0T EPA rated 45 mpg hwy, 32 mpg city - starts @ $17240 (sedan)

[Miller88]

The problem is, people will start having fun with the boost and get poor mileage.

My parents have a 2014 2.0 Ecoboost Escape AWD. My father and I have no problem getting 30-32MPG out of it (way over the EPA rating). But we drive it light and stay out of the boost.

My 2.0NA Focus can get low 40s and it is rated for 34. Wonder what the real world economy would be on this when there is someone driving for efficiency behind the wheel?

I do like the idea of turbocharging smaller engines and putting in tall overdrives. Best of both worlds! My concern is that they may not be reliable in the long run.

Turbos are getting better, especially now that they are no longer oil cooled.

[MetroMPG]

Originally Posted by Miller88

Turbos are getting better, especially now that they are no longer oil cooled.

Will we be able to engine-off coast a Fiesta with no adverse effects on turbo longevity?

[Daox]

I dont think I would without an electric water pump to keep cooling the turbo while the engine is off. It wouldnt be too hard to rig up.

[pgfpro]

I think it depends on the amount of fuel that is used during the pulse. Most likely it won't be that much and only slightly more then a N/A engine would be.

I just did some stoichiometry testing on my turbo car and the center cartridge doesn't increase at all in temperature after a pulse at 14.7 A/F and pulling over and checking with a infra-red gun. The added frequency of EOC is what would determine the amount of engine oil break down and a good synthetic oil would be a must to offset it.

To be fair EOC also has to have some negative effect at the exhaust valve guide since the exhaust valve itself will run around 650*C at the center of the valves head.

Today's turbo cars are all water cooled and what Daox proposed is a very good idea and I agree a extra low voltage water pump could be installed very easily.

[wdb]

There have been a lot of improvements to engine-off cooling of turbochargers as well. My STi for example has a small coolant reservoir located above the turbocharger. When the engine is off, heat continues to be exchanged from the turbo to the reservoir via conduction. Turbo timers, even in high performance cars, are pretty much a thing of the past.

When I was in Europe a few years ago we rented a little Fiat diesel thingie. It looked like a tiny minivan. It had a 1.1L turbocharged engine. The turbo was the size of a large coin! It was so small and spun up so fast that its full capacity was available just above idle; if I recall correctly full boost was at 1500 RPMs. I would expect this Ford turbo will be similar. In other words it won't be something you will be able to "stay out of" during acceleration because it will spin up so quickly and easily.

[redpoint5]

I don't understand how turbos are hurt by shutting off the engine. Sure, the oil or water that cools it stops flowing, but so does the heat generation. Does a turbo continue to increase in temperature after the engine is shut down, and if so, how?

[pgfpro]

Originally Posted by redpoint5

I don't understand how turbos are hurt by shutting off the engine. Sure, the oil or water that cools it stops flowing, but so does the heat generation. Does a turbo continue to increase in temperature after the engine is shut down, and if so, how?

The turbo's hottest part, the turbine starts to cool when the engine is shut down. But the problem lies in the turbine transferring heat to the center cartridge. When the engine is shut off, the center cartridge will no longer have nice cool oil and coolant to cool it.

When the engine is running the center cartridge will run around 220*F due to oil and coolant flow. The turbine housing always is transferring heat to the center cartridge. But with the engine off and no circulation of coolant and oil to pull away heat from the center cartridge you could see the oil film degrade at the turbo's shaft and bearing's, if the turbine reaches extreme temperatures from very high engine load, or not enough ignition advance.


This is one of my turbo's that had some heat issues. Plus you can also see some coking at the turbine's seal.

[Miller88]

Originally Posted by MetroMPG

Will we be able to engine-off coast a Fiesta with no adverse effects on turbo longevity?

Originally Posted by Daox

I dont think I would without an electric water pump to keep cooling the turbo while the engine is off. It wouldnt be too hard to rig up.

I have not looked at the 1.0 EB, but the other EcoBoost engines (and most engines with coolant cooled turbos) have the cooling system designed to utilize convection currents to keep the coolant flowing when the engine is off. You no longer have to idle when you get somewhere to allow the turbo to cool down.

[War_Wagon]

Originally Posted by redpoint5

I don't understand how turbos are hurt by shutting off the engine. Sure, the oil or water that cools it stops flowing, but so does the heat generation. Does a turbo continue to increase in temperature after the engine is shut down, and if so, how?

I was always told that it's because the turbo is still spinning when you shut the car off if it had recently been under boost, and once the engine stops then the shaft is still spinning with no oil circulation. I don't know how accurate that is, but it made sense when I heard it. The turbo timer would let the oil keep flowing at idle until the turbo had time to stop spinning.

[user removed]

If you P&G (engine off) you are going from a significant impeller speed to basically nothing fairly quickly. While you jsut shut the engine off the turbine impeller could still be spinning at 20-30,000 RPM. Although you have shut off the heat source (combustion) you have not shut off the heat transfer.

Now you have a very hot turbo, with the shaft spinning rapidly and it is very hot, but you have eliminated the oil flow and coolant flow (if water cooled). Even with a high quality synthetic oil, you have a recipe for failure, a situation way outside design parameters.

regards
Mech