[SeanB]

And to add, "Tool, Special" often was a standard tool, just modified. A standard box spanner, with a ground down face, so as to fit a reduced thickness locknut as an example. Another, a standard flat blade screwdriver with a thinned down blade, to fit in a hole to turn a screw head recessed deeply in a machine.

[Geezer]

Did they actualy have it in stock? Here it is almost always - Ex Factory ( 6 weeks).

I never really got that far because that was about as much as I paid for the car! (It was 35 years ago).

[Nizzle (OP)]

How's the post-mod mileage testing going BTW?

First empty gas tank increased my range with 85Km until the "Go fill up light" came on, but I had considerably more traffic jam on my commute due to road works.
The tank I'm doing now might be more comparable due to more comparable traffic situation, and I have high hopes of getting more than 110Km extra range, which would be 10% of the total pre-chipping range.

[peppercorn]

I have high hopes of getting more than 110Km extra range, which would be 10% of the total pre-chipping range

Thanks for the feedback.
I hope you're enjoying those extra torques that were promised!

Have you got as far as doing a rough calculation on what the payback period is for the cost of the 'chipping'? Not that it's all about the dosh necessarily, but it's nice to know.

[Geezer]

I await the results with bated baited baytied
 
The results should be interesting.

[syhprum]

Modifying the engine mapping sounds to me like a very dangerous procedure (financially) professional programmers are known to leave the occasional bug in programs let alone amateurs who do not have all the debugging facilities that the original engine mappers had.

[Nizzle (OP)]

I have high hopes of getting more than 110Km extra range, which would be 10% of the total pre-chipping range

Thanks for the feedback.


I hope you're enjoying those extra torques that were promised!

Have you got as far as doing a rough calculation on what the payback period is for the cost of the 'chipping'? Not that it's all about the dosh necessarily, but it's nice to know.

Yes, the extra torques does provide extra driving pleasure
If, for the sake of easy calculations I assume a gain of 10% (which it's likely to become I've noticed), then let's see what the payback period is at current fuel prices:

Before chipping, I spent 85€ to fill up and drove ~1100Km pump to pump (~985 until "low fuel" light turns on, but then I still have 10L)
After chipping with an assumed 10% increase I will spend 85€ to drive ~1210Km pump to pump.
I annually drive ~44.000Km, so I save (44000/1100)-(44000/1210)= 40 - 36.36 (let's stay conservative and take 36.5) = 3.5 trips to the fuel station per year, or 297.5€
Chipping set me back 500€, so payback period is about 1.7 years under fixed fuel prices.

Modifying the engine mapping sounds to me like a very dangerous procedure (financially) professional programmers are known to leave the occasional bug in programs let alone amateurs who do not have all the debugging facilities that the original engine mappers had.

I've been given 3 years warranty on the engine, and 1 year on the gearbox. I'm thinking that if nothing goes wrong in that period, it won't go wrong after that period either? And I can always have it "rechipped" after 3 years just to get an extended warranty and still make profit

[Nizzle (OP)]

Hi guys,

I did another test with some very good results. I expected some fuel economy improvement, but not this much..
In Belgium, motorway speed limit is 120Km/h. Now I did a full tank with maximum speed 110Km/h on the meter (which is about 102Km/h in reality). This increased my range from pump to pump from ~1100Km to ~1450Km (!!)
I also noticed that it impacted my work-home commute time with less than 5 minutes, and I must admit, I'm driving with a lot less stress caused by "slow cars, get out of my way!" situations

I think I'll stick to my new max. speed from now on...

[Geezer]

Are you saying you reduced your cruising speed? If so, that will have a large impact on fuel consumption because most of the power produced by the engine goes into overcoming drag, and drag is proportional to the air velocity cubed. Reducing your cruising speed by 20 km/h will save a lot of fuel.

On freeways, I tend to drive a few MPH less than the limit. It makes little difference to the journey time, and it's a lot less aggravating (for me anyway). I think I might invest in a trilby.

[peppercorn]

Yes. Not wanting to lessen your good efforts, but it may be at least in part a little of improvement by placebo - ie. taking more care with your driving because you want good results...  trying to replicate how you drove before is the best test you can hope for but even then it's probably still going to be skewed subconsciously.

[Nizzle (OP)]

peppercorn, before as well as after chipping I was obsessed with getting maximum range out of one tank of gas, so my driving style was similar, with the exception that I'm accelerating a bit faster and smoother to cruising speed after the chipping, because the chipping made that possible
My previous post was not a comparison pre- and post-chip. It was a comparison in cruising speed 120Km/h vs. 110Km/h on motorway, both post-chipping. The range increase of this test is however much bigger than the range increase of chipping..
Oh well, up to now, I'm convinced that chipping my car was a good idea. There may be some placebo effect, although there's hard data as well, and I believe that in ~ two years (conservative estimate), I will have return on investment followed by actual profit afterwards...

[peppercorn]

Apologies for my misunderstanding
Although I guess it'd be good if you could separate the two changes (chipping and speed reduction) for a side-by-side comparison.
Still even if it takes the remaining lifetime of the car to get RoI then in my book it was probably worth the 'experiment'!

[syhprum]

I always understood that at modest speeds drag increased as the square of the speed it is of course the power required that increases as the cube of the speed.

[Geezer]

I always understood that at modest speeds drag increased as the square of the speed it is of course the power required that increases as the cube of the speed.

Quite right! I thought that was what I said, but I didn't.

[techmind]

Thanks for your nice graph, Lmnre, but won't the fuel efficiency depend (non-linearly) on the demanded torque - at any given rpm speed?

Surely the efficiency should be a 2D (3D?) plot of efficency versus engine speed (rpm) and torque (or power)?

I would really like to see a 3D plot for my (petrol) car engine...
I'm not doing badly though, to get about 40mpg out of the car even for my daily commute, about 5-6miles each way, on 30-50mph roads, over half of which is 'urban' driving. And that's with fairly "enthusiastic" acceleration when it's safe and inoffensive to do so. :-)

[William McCormick]

Hi,

Next week, i'll be "eco-chipping" my car. I'll have experts rewrite my motor management software to make it more fuel efficient, with a 5-10% increase in range with a full gastank by optimizing valve timings in the 1500 - 2500 rpm range. They will also make my acceleration pedal feel more like the "old mechanical systems" instead of the current "drive by wire", and they will also increase my torque from 350 to 400 Nm, but my BHP/kW will remain the same (since increasing BHP without informing the taxation authorities is illegal here).

So my question is: "What performance differences can I expect with this Torque increase while my maximum Power stays the same?"

For good performance torque, is usually king. If you have a lot of horse power, but you have to make it 3,000 or 4,000 rpm, that is time. When you want to get on the parkway, you do not want to wait for the engine to hit 4,000 rpm, and then go.

With torque, you just go. Many of the state trooper, state police cars used to be equipped with what some dealers would call a parkway rear. Parkway rears are not popular with most amateur street racers. Because they heard that, at the race track, they use much higher gear ratios. Higher number of drive shaft revolutions to tire rotations. But what they don't realize is that at the drag strip or even the small oval tracks, the race engines are fully or nearly fully revved, to the maximum sustainable RPM's the engine can handle. They channel the full horse power, through the clutch. The average street car would last about a month doing that.

The average driver and car, even the guy who likes to move, will benefit from the parkway rear, and high torque. Because the automatic transmission is usually designed to make the most of the parkway rear. You get really good acceleration, because, you have the torque, and since the drive shaft is not turning very fast, you can stay in first gear to 50 or even sixty miles an hour. Giving you a wild acceleration curve.

To give you an example the older 1986 five speed mustangs were very fast, off the line, they were the car to beat. But a larger heavier thunderbird of the same year with a parkway rear, could stay with the Mustang off the line. It would hang three car lengths back, until the cars hit about 70 miles an hour, and then the Thunderbird would, literally wall all over the Mustang. The Thunderbird used to get about 17 miles to the gallon all around. And as much as 27 highway doing 70 miles an hour. Top end was off the odometer.

Some of the higher end vets would also walk all over both of those cars. But the average stock vets would get beaten by the Thunderbird.


                      Sincerely,

                            William McCormick 

[peppercorn]

Thanks for your nice graph, Lmnre, but won't the fuel efficiency depend (non-linearly) on the demanded torque - at any given rpm speed?

Surely the efficiency should be a 2D (3D?) plot of efficency versus engine speed (rpm) and torque (or power)?

This may not be precisely the comparative plot you're looking for but most manufacturers will (eventually) publish one of these: a Brake Specific Fuel Consumption (BSFC) chart.

They can be particularly useful for understanding where the sweet-spot is for a vehicle w.r.t. throttle setting, engine load and revs; which is sometimes counter-intuitive.