Thread: Trivia and other useless but interesting items

Originally Posted by Eevo

i recently did a 1500km trip in my 2013 e3 hsv maloo. i wanted to post some things i found that i found interesting (but useless)

the facts:
6.2l v8
aftermarket cam
tuned, peak power 350kw at the rear wheels
4.11 diff gears (stock is 3.7)
car weights about 1800kg


before, twin 2.5inch exhaust, x-force headers, pacemaker exhaust
now, twin 3.0inch exhaust, kpm headers, kpm exhaust

before, adelaide to alice springs, cruising at speeds of 110kmh to 150kmh, fuel economy about 12-14l/100km
after, adelaide to newcastle
110kmh, fuel economy about 10l/100km
150kmh, fuel economy about 13l/100km
300kmh, fuel economy about 30l/100km, hard to tell, only did this in small bursts. was an instant economy rather than an average.


my 2008 RRS 3.6 v8 diesel weights about 2700kg, fuel economy is fuel economy about 12l/100km
RRS weights 50% more than the maloo
RRS has half as much power than the maloo, similar torque values.



some things that i can surmise/deduct:
better flowing headers/exhaust results in better fuel economy, a better sounding exhaust and a more responsive engine. no change to peak power tho.

being diesel alone does not reduce fuel enonomy. weight and possibly aerodynamics are big factors too.

around town the RRS is better on fuel than the maloo. maloo is about 17l/100km, RRS is 12l/100km.

sydney traffic at midday sucks and i wasnt anywhere near the cbd. Goldburn to Lake Munmorah. the Pacific highway cruise is magestic!






questions: how big a factor does aerodynamcs play into fuel economy?
i asked google to take me on non toll roads. it took me on the M5. how much do i owe? did i get lost?

On Fire Eevo 300kph News is that there is also another burning rubber involving Landrovers!




Enormous fire at Jaguar Land Rover's Castle Bromwich car plant as firefighters rush to scene

Originally Posted by Eevo

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questions: how big a factor does aerodynamcs play into fuel economy?

...............

I can remember in the 70's after the oil crisis there was a fair bit of info on this.

From memory air resistance got somewhat exponential over 100 km/h and around the top of the windscreens of the day was a bad area.

Carmakers concentrated efforts in that area to get it as smooth and aerodynamic as possible, so things may well be different these days.

In my 74 POS I'll get about 10% more milage at 100 km/h with a 20 knot tail wind compared with 100 km/h in no wind.

DL

I remember years ago,VW boasting their Kombi van,late 70's model, had less air resistance than an E type jag.

Speed makes a huge difference to fuel burn.

The LC200 we have,has a graph of fuel burn in real time which is extremely accurate.This can be watched as it is being driven.
A drop of 10Km/hr in the 90 to 130Km/hr range will usually drop fuel burn around .9 to 1.5L/100Ks.Not towing.

Air resistance is exponential, or more precisely, proportional to the square of the speed relative to the surrounding air, right from a speed of zero.

But other resistance (or equivalent losses) to moving also exists from zero. But this other resistance is not proportional to the square of the speed, but can be constant, such as some frictional resistance, and the resistance equivalent of energy that needs to be expended regardless of motion, such as the airconditioning and heating, some of it is proportional to speed, such as rolling resistance of tyres.

For typical modern car designs, air resistance is insignificant compared to other resistance up to speeds above about 50kph. Above this speed (which will vary somewhat according to design), it rapidly becomes the dominant resistance because of the square of the speed relationship.

Another factor which can obscure this relationship can be the engine efficiency of the vehicle, which can vary widely according to engine speed. This is particularly important if the vehicle has few gears and a rather peaked engine efficiency curve, or, even with a wide range of engine efficiency, if the vehicle is driven at speeds above which engine efficiency drops off even in the highest gear available. In some cases there are other factors as well, such as speed dependent gearbox losses and critical airspeeds at which aerodynamics change, or windows up or down which change aerodynamics. etc.

And, of course, roof racks, trailers, towing mirrors etc can completely change the aerodynamics.

Originally Posted by JDNSW

Air resistance is exponential, or more precisely, proportional to the square of the speed relative to the surrounding air, right from a speed of zero.

Thanks John, since the beginning of this conversation, I've been trying to recall an article I read forty odd years ago about speed and trailer heights above cab height and their effect on fuel consumption.
Basically, if I remember correctly, 1 foot above the cab at a constant speed required X amount of extra fuel, 2 feet above required X² extra fuel.

Interesting really. Old boss chipped me because he once got a better fuel reading from the R-730 than I did. Except, as I pointed out he was towing a set that was flat floored and 4.3. I almost always towed a double drop, 72 pallet mezz set that was 4.6. So, not only bigger frontal area but heavier as well.

This was interesting
Dumping syndrome - Symptoms & causes - Mayo Clinic
My keen interest in running could add that eating before running fast has a consequence as well 😁😁😁as well

Originally Posted by NavyDiver

This was interesting
Dumping syndrome - Symptoms & causes - Mayo Clinic
My keen interest in running could add that eating before running fast has a consequence as well 😁😁😁as well

Makes sense to me, jogging ends with the runs.