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Old 08-26-2017, 08:55 AM   #1 (permalink)
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How would you accelerate my car? (small turbodiesel)

I have a Renault Clio dci with a 1.5L turbodiesel engine. Advertised power is 90HP and 220Nm of torque (162 ft/lb). I have made the assumption that I should accelerate with as little throttle as possible and upshift as early as possible. I usually upshift at about 1800rpm which means I am at around 1200-1300 rpm in the next gear (second gear and up, fourth and fifth have a smaller difference). It is a double overdrive 5 speed manual transmission (4th is at 0.9, 5th is at .67 and the final drive ratio must be 3.55).

Below is a link to a dyno run made by some chip tuner, the blue dotted line is the stock torque curve and the red dotted line the stock power curve. Ignore the solid lines as they are the tuned ones.


Would you accelerate with light or high load? Would you try to keep the engine at 0 boost? At what rpm would you upshift?

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Old 08-26-2017, 10:08 AM   #2 (permalink)
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You really need to run some tests on your car to find out. You need a gas mileage computer, most of us use a Scangauge or Ultragauge. Start at a defined point, set the computer to zero, accelerate to a speed, then read the gas mileage as you pass a second defined point. Do this for different acceleration rates and shift points. Accelerate to the same speed in all tests.

The second point, where you read the gas mileage, should be just after you get up to your speed at the slowest acceleration. My truck does best when I just step on the gas and shift at 2500 RPM. That also has me moving with traffic.
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Old 08-26-2017, 12:04 PM   #3 (permalink)
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Unlike a gasoline engine, you're not going to suffer much pumping loss by not accelerating hard. Theoretically, you will get an even better BSFC when you get in to boost, because the engine can create more power per stroke (even less losses). So you won't waste fuel accelerating quickly, either...unless you are jack-rabbiting between lights and having to slam on your brakes and wasting your momentum each time. The only thing that will waste power is (sustained) revving up higher than you need to be.

I'd accelerate however I felt like at the time, and remember to shift somewhere around 2500-3000 rpm...or 2000-2500 if I'm in no hurry.

I've driven my TDI like I stole it, and I've driven it like a granny...it still gave me 40mpg (US) each way.
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Old 08-26-2017, 10:08 PM   #4 (permalink)
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What year is your Clio?

Newer cars run very lean off boost but can run very rich on boost (power OR economy). A lot of diesel driving tips relate to old tech.

I have 2016 dCi-140 (1.6), here are my tips.

Use eco mode if you have it. Eco mod reduces acceleration enrichment (ie give soft throttle response). If you don't have Eco mode, remember your right foot controls your AFR (to an extent), so be gentle.

Cruising at a steady speed is far better than P&G

I accelerate at up to 80% load, in my van there's a throttle stop that in Eco mode gives me an easy way to drive that way without looking at the SGII. Accelerating slower, keeping boost low definitely helps my city economy.

After accelerating to cruise speed, lift off completely for a couple of seconds, then gently add throttle to maintain speed. The ECU goes into DFCO and when you add throttle, you're running lean cruise mixtures immediately.

I'm now regularly seeing 5.5/100km (40+MPG). I'd love to see what this engine would do in a car half my van's size and weight.

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Old 08-27-2017, 06:57 AM   #5 (permalink)
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From what they say here driving small turbodiesel around 1500-1700 RPM leads to clogged turbo, clogged EGR and who knows what. When I was at the inspection responsible technician was revving up my engine to clear the soot emissions and advised me not to drive like I did. So now I drive a bit below 2000 rpm, accelerate quick enough to get in speed soon and than try to stay in lean burn. Using this I am able to be in par with NEDC figures, or even beat it.
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Old 08-27-2017, 04:54 PM   #6 (permalink)
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I'd rather keep the load the most constant possible, and I see no reason to keep off-boost. No wonder the main improvements in turbocharging have been done to make them spool faster at lower revving.
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Old 08-29-2017, 08:02 AM   #7 (permalink)
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Originally Posted by oldtamiyaphile View Post
What year is your Clio?
I do use eco mode 99% of the time. It is a 2015 model but it has the K9k 1.5 diesel whereas yours has the 1.6 R9M. We also have a 2015 Qashqai that has the 1.6 diesel. Throttle response is way tamer in eco mode and full throttle before the stop is probably about 70-80% load. I did not know about the DFCO trick so thank you for that! I don't P&G the diesels as there is no point in doing so. I am usually at 3.7L/100km although I have gotten it down to 3.2 in a 1500km round trip at 90km/h (with AC on!). Feels great getting 1500km out of a single tank! I have the torque app and a bluetooth OBD reader so I am going to experiment with that.

Originally Posted by seifrob View Post
I only drive it at low revs inside the city or while accelerating. 90% of the time I drive on the highway where the engine is turning over 2000rpm at speeds over 90km/h. They also say that sudden high amounts of load produce soot that clogs stuff up so I try to avoid that. In my opinion, city driving is the worst for soot production, so I tend not to use the car when possible.
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Old 08-29-2017, 08:16 PM   #8 (permalink)
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You realy need the BSFC line to get an accurate guss from the Dino. I say guss becuse the dino run is at max fule making the info only accurate at full throttle. In over the road trucks more time at a medium acceleration takes more fule than a short time at medium-high(not max) rate acceleration to reach hi gear (low fule consumption /rpm) . Shifting too soon is bad to as this bogs the motor and takes more fule/time than if the same rate of acceleration in the correct gear slection. Early shifting will make your emissions equipment work harder as well. There are 2 ways to make boost. 1 shear rpm/cfm. 2 fule. At high rpm (read 60mph top gear) the air flow is sufficient to make boost. At low rpm cfm is to low to make boost so boost is made from over fueling.
Try shifting plus or minus 50-250 of were HPand TQ curves cross about 2200rpm for you and 2115rpm tor the modded rig. This x marks the spot to start and adjust to preference. In the '60s this x was the spot that yealded the best engen life and usually best economy.
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Old 08-29-2017, 09:05 PM   #9 (permalink)
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Originally Posted by sotiris.bos View Post
I have a Renault Clio dci with a 1.5L turbodiesel engine. Advertised power is 90HP and 220Nm of torque (162 ft/lb). I have made the assumption that I should accelerate with as little throttle as possible and upshift as early as possible.
I have a Clio engine in my Scenic.

This is how I accelerate mine:

I still get around 12l/100kmh in such situations.

So for economy, perhaps the opposite of that. :-)
2003 Renault Scenic - 30% more power with no loss in fuel economy.
1991 Toyota GT4 - more economical before ST215W engine-swap.
previous: Water-Injected Mitsubishi ~33% improved.
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Old 08-30-2017, 10:13 AM   #10 (permalink)
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Find a Brake Specific Fuel Consumption map for your engine. It will show you how much fuel you're burning for the engine's load and rev range.

Somewhere on that map you'll see where the isobars probably make a zone of lowest consumption per unit of power at a certain loading and speed. Aim to do all your accelerating in that zone of load and speed.

Barring being able to find the BSFC map, aim to do all your accelerating in and around the engine's torque peak, which for you is at 1900 rpm. It'll be in the ballpark, even knowing that the torque peak assumes WOT for the test. Gear in, let out the clutch, foot flat to just past the torque peak rev point, shift. Repeat as necessary until you are at your desired speed.


Lead or follow. Either is fine.
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