Hypermiling a VW TSI (turbo direct injected) engine

Discussion in 'Fuel Economy' started by swineone, Sep 17, 2019.

  1. swineone

    swineone Well-Known Member

    Hello everyone,

    Old timer here (even placed 1st on one of the B-league of the hypermiling competitions about 10 years ago, when I had a Honda Fit), but I haven’t visited the site in a while. However, I’ve been applying what I learned here ever since.

    I just sold my old car and bought a new one, which is a Volkswagen up! with a 1.0 TSI flex-fuel (ethanol and gasoline) engine (3 cylinders, turbo and direct injection). By the way, I bought this car because it is advertised as the most fuel-efficient non-hybrid car in Brazil. This prompted me to come back here to see if I can learn something about hypermiling this engine, since it is so different from those I had previously.

    Obviously many techniques still apply, especially those that have to do with paying attention to traffic ahead of you, to avoid losing momentum, drive at lower speeds, driving with load and so on. However, turbos are new territory for me and I’m looking for some tips on how to extract the best efficiency from them. Here is a torque/power curve for the engine in my new car:


    Unfortunately I was unable to find an exact BSFC chart for my engine, but I did find one for a 1.4 VW TSI engine, which is reproduced below:


    If I hadn’t seen this image, my guess for the most fuel efficient part of the chart would be at low RPMs, as usual (2000-3000 as the chart shows), but especially, that it would be closer to 50% of max torque, with an equivalent manifold pressure to the usual 70-80% of max torque we find on NA engines. In other words, I thought from the moment the turbo spun up, I would be getting a worse BSFC than if I just stayed a bit below atmospheric pressure. However, this chart appears to show the usual sweet spot at 70%-80% of max torque, where certainly the turbo is already acting.

    Thus, my main question is: can I keep using the older rule of aiming for 70-80% of engine torque at low RPMs for maximum efficiency? The chart certainly appears to say so.

    The next question regards P&G. I’ve been driving my car using P&G with ICE off for over a decade. However, I’ve heard that, to prolong lifespan on turbocharged engines, one should idle the engine for a while before turning it off to let the turbine cool off. Doing P&G with ICE off would directly contradict this, and I don’t want to do anything that puts the health of my engine at risk. Currently my thinking is to continue doing P&G, but with ICE on. So can anyone comment on this?

    At last, I’d appreciate any other tips that are specific to this type of engine. Info about maintenance would be welcome as well — I’m somewhat worried about the tales of carbon buildup on the back of the admission valves because of direct injection. Because of my very severe driving pattern (my commute to work is about 1 km on the way in, and another 2 km on the way back or so), I’m thinking of doing oil changes every 6 months rather than the manufacturer’s recommendation of every 12 months. Note that while this suggests I shouldn’t even be getting a car, unfortunately this is not practical in a country with crime problems like Brazil, considering I lug my $4k laptop to work every day. I’ve looked at EVs, but with the cheapest ones costing 3 times as much as the up! I just bought, it made no sense to me, especially considering how little I drive.
    UberJager and BillLin like this.
  2. Carcus

    Carcus Well-Known Member

    Hello and welcome back.

    Another maintenance consideration would be oil dilution with fuel. These types of engines (direct injection/ turbo) are somewhat prone to that, especially with your driving pattern,... I might think leaning on the turbo could exacerbate. (checking that the oil level is not rising/ changing more frequently --- probably a good idea)

    FWIW, for city driving, .. I keep my civic 1.5T in eco usually, which limits the amount of boost. I couldn't do engine off coasts (even if I wanted to) because of the car's electronics (multiple errors if I did).

    /I'm curious to know what you're able to get out of the little 1.0T (I'm averaging 45 mpg on my 1.5T 6MT (87 E0 usually).
    BillLin likes this.
  3. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    I've been wondering about the potential io the VW 1.4 TSI , an engine we can get here in the Jetta and Golf.
    Maybe as good as the Honda ? The EPA numbers aren't extremely impressive , but we know that those numbers
    are for reference only. Actual mileage will give the EPA number a sound spanking.
    BillLin likes this.
  4. swineone

    swineone Well-Known Member

    As an initial report, I’m rather happy with the fuel consumption of this car.

    Yesterday, I drove it from a cold start (although the ambient temperature was fairly warm), no AC, driving using P&G with ICE-on, on a fairly short trip of about 6 km inside town on a hilly terrain, stopping at a few lights and getting some light traffic. I’m babying the engine for now since I’m still breaking it in (I just took the car out of the dealer on Thursday), so I’m trying to avoid the usual 70-80% target engine load and going for about 50-60% instead. From my parking spot to the destination parking spot, I got 12.2 km/l on ethanol (E100), which I expect would translate to about 18-19 km/l on gasoline.

    On a second trip yesterday of similar length, I also achieved 12 km/l. In this case, the engine was already warm (not up to operating temperature though), but the outside temperature was about 5 degrees Celsius colder as well.

    These are very promising figures, and I’m excited to see what I can get out of this engine once it’s broken in and I get acquainted with the car.
    BillLin likes this.

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