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Hi all,

Please see the Introductions forum for my previous posts. They are relevant to this one..

As far as my work is concerned. I'm mostly looking into existing simulators at the moment. What I consider the most important things to teach at this point, are these.

First of all, I want people to get some understanding of engine load. That will enable them to make far better decisions about gear shifting: when low load, go to low RPMs. When load is high, keep slightly higher rpms (up to 3000 or so).

This is important to me as I see many diesel car drivers around town being too lazy to shift back into 1st gear after almost a full stop, then hitting the accelarator really hard in order to have some torque. I cycle behind them in thick black smoke... Various sources on the net confirmed that this is a symptom of an overloaded engine. In addition, it wears out the engine much faster.

Now, I think if people would understand this concept, they would be far more inclined to pay attention to their shifting behaviour. I prefer no to treat them as stupid and just tell them to shift up sooner.

Secondly, I want them to practice on the simulator a very anticipating driving style (DWB) in various circumstances.

Well, I'm sure there are more important things, but please let me know what you guys think about this.

Thanks,

Wim

Hi WimW:

___I have maybe 45 minutes in total behind the windscreen of a CI-ICE based VW and running at 3,000 RPM is bad enough in std. SI-ICE, let alone a CI-ICE. Never ever go there is about the best advice I can give and stay out of first gear if at all possible is the second. The Ranger P/U never sees first gear other then from a dead stop and only for a second or two before I am in second. She also never sees over 2,300 RPM yet she has allowed me upwards of 65 mpg over a 20 mile flat segment under P&G. 70 + out of the Accord … And now 180 + out of the Insight. All the while never ever approaching anything near 3,000 RPM let alone 2,500. See my previous post wrt to steady state speeds.

___You have to throw those maps away as they don’t work for those of us that do actually push tanks in the real world.

___Good Luck

___Wayne

It's not so much a matter of throwing the maps away as using them for what they are worth, and no more. I had a look at one that was posted on another forum and was applicable to some kind of gas engine. Basically, it showed that the highest Brake Specific Fuel Consumption occurs at 60-90% load from 1500-2200RPM. In other words, that's where you burn the least fuel per unit of power generated. So if you are going to get maximum fuel economy you want to stay in that region, right? Not exactly.

Fuel economy in miles per gallon doesn't translate directly from BSFC. Even though those maps tell what to do with throttle and gears (gas engine here) when you want to make power, it doesn't always make sense to generate all of that power in the first place. What I have found is that, given a choice, it's best to shift at roughly 2,000RPM and keep a light touch on the throttle. Getting into the high-torque area would get me to speed faster, but doesn't correlate with my best trips. The less I demand of the engine, the less fuel it burns.

Thing is, diesels work on a different control mechanism. Rather than controlling air and metering fuel to match at a roughly stoichiometric mixture, a diesel just lets the air flow unrestricted and richens the mixture depending on how hight the power demand is. All of that black, nasty smoke from older diesels comes from huge amounts of fuel being dumped into the cylinder during each cycle. So the question: what to do about it? If you absolutely need to make the power, I think that the solution is to down-shift and bring the RPMs up rather than keep them low and inject by the litre. But the other solution that most drivers whine about is leeping the RPMs low and maintaining a light touch on accelerator. It stands to reason that reduced frictional losses of low RPM driving would give the best possible results.

In short, the suggestion to down-shift rather than stomp on it is not wrong. But it's only half of the full solution.

After reading Tim's post, I see that we will have to treat gas and diesel engines as entirely different. Does the following make sense to you folks?

Assume a normal person will want to keep up with other traffic, and hence get a certain amount of power... In the case of a gas engine: stay in low rpms and hit the accelerator enough to keep up, even if that's quite a bit of throttle. In case they can't keep up: go to higher rpms. In the case of a diesel engine: go for low accelerator, while trying to keep rpms low if possible. That way you avoid lots of diesel being injected and coming out unused the other end.

I'm also posting a more general question about this stuff in another thread.

Thanks,

Wim

Sounds sensible to me.