need Kern's brain power on this....

[glen e]

As many of you know, I am the factory sales rep for BMW in south Florida…been doing this about 20 yrs and love my job. Who wouldn’t? One of the perks is I drive everything new so I can train the sales staff at the dealerships here. Every now and then I get to drive something special yesterday I got an M6 for a few weeks –> 500+ hp V-10 engine and as the Germans want it – no cup holders whatsoever! See here:


Please no anti-BMW comments – I don’t care what you buy….that’s not the point…. read on….

The interesting thing is this the first car I have seen with the ability to dial up or down the horsepower, not the “economy” or “sport” buttons on some cars that change the shift points, this is changing engine mapping and gets specific about it...you can choose 400 hp, 500 hp or 500 hp “plus” – Naturally the MPG changes too and the diff in the "400" and "500 plus" settings are HUGE – 10 mpg vs 17……see here on the dash how to dial it up or down:


So that begs the question, why can we do this in OB motors?…. Many of the motors made today are nothing but software changes, if you have a 200 verado and can find a wrecked 275 and can salvage the computer..it will plug in and voila!, you have a 275..Naturally your warranty is gone and you can’t order a new 275 computer from merc without trading in your old one…EPA and all that stuff.

So we know that due to the EPA we can't dial up, but how about this? – how about the ability to DIAL DOWN your hp when you don’t need it? Say you are heading out for a long trip to the canyons or Key West and you are on plane, all weight distributed and you’re running 275-300 somethings….and on your instruments you had a button labeled “economy” that would load the 225/250 engine map? A good example is the new Yam F350…why can’t you dial that motor back to the F300 if you’re up and running on flat sea and save a few gph?

Let the discussion begin…

[CAP1]

Glen,
That's wicked sweet. I've always believed every car enthusiest should drive/own a V-10 or V-12 before all the gas is gone.

From a technology standpoint, I think what you are talking about is certainly possible. I think the Verado HP changes within the same block/size illustrate how engine manufacturers do have the ability to change power with only software/programming changes. I can see the liability issue of adults having larger HP engines and having the sense to moderate use of high power levels, then Johnny the teenager getting aboard with his buddies for a ride and ratcheting up the power. I guess it is the dial-a-level power ability that, while sounds great for those with sense, may be concern for liability lawyers of the corporations.

Certainly F1/CART/Indy type engines have this type functionality for years, but with turbo or forced induction designs. It is all in programming fuel, air, pressure, and combustion levels in a controlled environment.

Let's see what outboard manufacturer brings it to market 1st. I would think the Verado design would give Merc the edge since they already have a proven forced induction design.

Just my .02

[CaptGorges]

Not sure that this answers any of your questions, but it has seemed to me through owning several cars that I have put "power-chips" or whatever, I have never been able to gain more than 10-15 hp, but I guess Ive never tried to retard the timing to reduce HP. And most cars are already tuned for optimum performance, you cant get a whole lot more out of them. Maybe in the example you used on Verados, assuming it is the same block and supercharger and all, you may be correct. Ive always wondered though about chipping a marine diesel motor. My dad has a '05 GMC Duramax and he has a programable chip that you can tune to +50, +100, or +150 with the push of a button. And she will SCREAM. Other guys I know with diesel trucks have chips that allow you to do more to the system (fuel/o2 ratio and whatnot), dad's just does HP. Im going to put a KAD43 Volvo in a boat soon, an early 2000's model (235HP/500Ft-lbs, cruises the boat at 28mph @ 3200RPM @ 3.5GPH, WOT is 35@3900@>5GPH) with a computer, and Ive wondered if on longer trips (stream and such) if I could crank it up another 100HP for the run out, burn a little more fuel, and run a little closer to 35-40MPH at cruise, and then tune it back down to still troll at 1GPH.

[SKEETERMAN]

Awesome car!!

[Kern O]

Nice ride, Glen.......

About the variable power: I've going to offer what I know (or think I know) about engines and the EPA. So, I'll do my best to make it understandable. That's not a word often used with the EPA. We need to start with a basic explanation of how a current generation engine is managed. Then, we'll look at what BMW may have done.

The use of a computers to determine fuel, timing, boost and cam position has really improved the efficiency and output of engines. But even with better cylinder heads, improvements in intake and exhaust flow, we still come up against some basic rules in spark ignition engines. The biggest one is the air fuel ratio. Get it too lean and it pings, get it too rich and unburned fuel goes out the exhaust. Since we want the best blend of power and economy, we also need to know where the mixture should be to make the best power and economy. Strangely, power goes up a bit as the mixture goes toward lean and begins to drop slowly as it goes rich.

So, once we get the mixture somewhere near right, we look at timing. Fire the spark too early and the cylinder pressure rises so fast that the engine is being pushed backwards as the piston rises on the compression stroke. Fire it late and you get nice flames out of the exhaust. A lean mixture burns quicker than a rich one. Likewise, as engine speed increases, the spark has to come earlier. Light loads, such as cruise speed, let you lean the mixture and advance the timing. But the moment the load goes up, you better add fuel and take away timing or ping sets in instantly.

The camshaft lets the engine breathe by opening the valves to let fresh air in and the exhaust out. But air moves slowly. If the engine was turning one rpm, we'd open the intake valve with the piston at the very top of the stroke and close it at the very bottom. Then the piston would come back up with the valves closed and compress the mixture. Once it was right back at the top, we'd fire the plug and the resulting explosion would push the piston down. Once it got to the bottom, we'd open the exhaust valve so the spent mixture could be pushed out the exhaust.

That's fine at 1 rpm. But as the engine goes faster, all of those things change because the air and fuel move slowly and the explosion takes time to come up to pressure. At higher engine speeds, the spark can occur at 35 degrees of crank rotation before the piston gets to the top. Any force generated by that explosion is actually pushing the engine the wrong way. but that loss is more than offset by making the most powerful part of the explosion occur when the crank is at an ideal angle to transfer as much force as possible to the prop (or wheels). The same is true with cam timing and fuel mixture.

So, you wind up with a map that is programmed into the computer that shows where the fuel and timing should be for a given rpm point and throttle position. Next, you need a bunch of sensors to tell the computer what is really going on. At every instant, it needs to know things like air temperature, throttle position, coolant temperature, the volume of air actually flowing into the engine so it can make its best estimation based on the pre-programmed map. But it can also cheat. Cleverly enough, it also gets input from two sensors that tell it what is really happening instead of just what is supposed to happen
Those are the O-2 sensor and the knock sensor. The O-2 sensor reads the burnt exhaust gases and tells the computer is the mixture was right or not. The knock sensor listens for ping and tells the computer how far it can advance the timing before ping starts. Put the whole mess together and you get an engine that idles well, cruises economically and will smoke the tires when you nail the throttle.

So, how did BMW come up with the variable power? By using different maps. One may have economy as the goal and the other may have power as the goal. In reality, those are very similar maps, as long as you don't mind the engine bogging as you climb into the throttle. The computer has to be able to watch the throttle position and figure out what you have in mind. If it senses a fast opening, it had better start adding fuel and taking away timing before waiting for the O-2 sensor and knock sensor to say "OK". If it does not add fuel it will ping and stumble. That gets into the issue of driveability, something that has improved a lot - along with starting. Gone are the days of pumping the pedal to start the engine and the engine hesitating as you go to wide open throttle. It is entirely possible to write one map that comes very close to maximum power and economy and many cars have them.

So, why are there different power levels available on command? I'm going to guess here, OK? I'll bet the most economical map is the default map. Why? So the vehicle had no trouble passing the EPA driving cycle for its fuel economy rating. I'll also bet it would face a huge gas guzzler tax if it was certified with the performance map. The EPA driving cycle has led manufacturers to do some "interesting" things. That driving cycle is a very specific program that is run on a dyno, not on the road. It is supposed to simulate both in-town and highway driving. It is also the same program for everyone for every car and etvery manufacturer. So, the manufacturers have analyzed it and have done about everything they can to make their cars get the best results on that specific test. I have a 2006 GTO with a six speed. The transmission is equipped with a device that makes you shift from 1st to 4th if you are driving at light throttle. Why? For better mileage, because it keeps the engine speed down and reduces friction. It is also very, very annoying. Why is it there? Because installing it improved the results of the EPA driving cycle. The automatics have a $1500 gas tax that the stick cars do not, partly as a result of that little solenoid.

Now, onto outboards. If the 200 Verado and the 275 Verado are the same engine with only a different computer (which I don't find surprising), how are they doing it? The Verado is unique in that it is supercharged. Adding boost adds horsepower. So, while we used to see the same basic engines having variations of 25 or so horsepower for different carb jetting or timing, we now see changes of 100 hp on a computer program. The Verado does it by adding boost and fuel. Blowers are wonderful in that regard. They let a little engine act like a big one. You just force more air down their throat..........But even though the blower will make more power, the frictional losses of the engine are a function of its displacement. Even if we use cylinder de-activation, the friction continues. But that friction is only a mionor factor here.

But boats have a very basic problem. What we think of a cruising in a boat, is still going up a very steep hill as far as the engine is concerned. It takes a lot of fuel to push the boat up that never ending hill. Boats also have a lot of drag and are very poorly designed for fuel economy in order to balance other factors such as ride. My 22 Talon would happily run in the high 130's on 600 horsepower. But the 600 horsepower that Glen recently bolted to his transom will only push his boat to half that. Why? The Talon was a tunnel hull and got up on a cushion of air, reducing the drag of the water to almost nothing. That nice big fuel and power eating wake it made at 20 mph was almost gone by 80 mph. At 125, it left nearly flat water behind it.

But put it in anything over a 2 foot chop and you were in for a brutal ride. The tunnel would slam and the sponsons loved to pierce the oncoming crest because the boat did not have enough lift to get the bow up in time to avoid giving you a bath of lake water.

Not so in a deep "V". They are happy to cruise through snotty water and the deeper the "V", the better the ride - at the cost of more fuel used.

The bottom line: I think any major change in fuel economy in boats will come as a result of hull design, not engine improvements.

[Playin' Hooky]

Cool ride Glen. Did not know you were a factory rep. Sounds like a great job. Wish I had went to school and became a factory parts rep for Ford. I am a wholesale parts manager at a Ford dealer.

The creation of horsepower via a laptop PC or simple download to a vehicles computer is amazing to me also. I dumped a program into my trucks PCM an instantly it became a monster.

In the near future you will see Ford releasing vehicles that also have variable programs that will be selectable in order to achieve better fuel millage and performance.

Do you work with sales or parts and service? I have two reps that visit me from Ford.

[darbikrash]

Thanks to Kern for that very informative description of ignition and valve timing. Nicely done and easy to follow.

The Z06 Corvette has had a "valet key" feature for almost 4 years now, wherein you can place a card into a dash slot and immediatley detune the engine by about 100 hp instantly.

This is great on cars, but I'm not sure about boats, for exactly the reasons that Kern has suggested. In the marine diesel world, data is plentiful and easy to come by. Not so with outboards. Just try and find any specs on BSFC (Brake Specific Fuel Consuption) for any outboard. Not gonna find it.

It is with BSFC data that we can see the effect of engine tune on efficiency.

If you're curious, take a gander over at the Caterpillar Marine diesel site, for example, and look at any engine that they produce. What you'll find is a full range of engine HP ratings for every displacement. For example, a 12 liter engine is available in A, B, C, D, and finally the highest, E ratings. The E rating in all cases is well over the 1hp per cubic inch displacement rule for high performance. Note the BSFC is listed for each HP rating.

Now this is going to sound funny, but the higher the rating, the more economical the engine is, as evidenced by the lower BSFC data. The engines within this rating are all pretty much the same, except for fuel maps and of course, boost. We'll get to that in a minute.

This is because the higher the volumetric efficiency in the cylinder, the more power it makes for given displacement. More power equals more fuel you say? Yes it does, but for two engines operating at the same power output, the one with the higher volumteric efficiecny (and lower BSFC) will get the better fuel economy.

So a 3208 CAT rated at 435 max HP (E rating) will get better fuel economy at cruising power (say 275 hp) that the exact same 3208 rated at 320 HP max (C rating).

I use the diesel example becasuse no such data is available to consumers of outboards, or you could make the same case with Verado's for example, if they'd be kind enough to make this data available.

So I agree with Kern and would conclude that although you may be able to detune an outboard, you would not want to because you would almost certainly get WORSE fuel economy. Similarly, if you were interested in reducing the load on the engine hoping that it would last longer, detuning is probably not the best way to go.

Again taking a page from the marine diesel guys who do this type of thing all the time, it's much better to underprop the boat if the goal is engine longevity, because it is the prop that puts the load on the engine, and nothing else.

But after all of this, if you simply must detune your engine, it's pretty easy to do with forced induction engines such as the Verado. Some type of wastegate can be installed, which diverts excess boost to atmosphere (obviously before fuel is added). It's even easier on turbocharged engines, the Cummins in my Dodge truck went from 12 psi factory boost to 35 psi boost with a $6 spring added to the wastegate....

By using the wastegate approach, much of the O2 sensor algorithims remain intact, as there is just less air (and conseqeuntly less fuel) going through the engine.

But don't expect to get good mileage.