http://world.honda.com/HDTV/news/2003-4031127a/

since i'm not too keen on much of these terms, i was completely lost... if someone could put it in lame man's terms that be awesome.

 

CRIMENY!!!!! 65:1!!!!!! forget about putting FI on that car.... first time you turn it on... KABOOOMMM!!

i bet that car gets like 40mpg...

 

Yeah I was gonna say, a bit lean.

I'm not a pro so forgive if I make some mistakes. A/F is the ratio of air to fuel in the engine. I'm thinking under forced inductioin conditions the ideal ratio is 12:1. That being 12 times as much air as fuel. If you run too lean you'll get detonation/knocking=BAD things for the engine. Basically under the situation where it's 65:1 they're hardly using any fuel at all.

I think it's pretty interesting how they vary the time in the stroke where the fuel is injected i.e. it's usually during the intake stroke but by doing it on the compression stroke it ensures (when combined with direct injection and that special piston) cleaner burning and more efficient burning of fuel. That's all I'm gonna say before I screw up some more. I hope I'm not too far off.

James

 

Yeah.. typical "safe" a/f ratio for a forced induction engine is 11.5-12.0:1... about 12.8:1 for an NA engine. Im sure they're using forged pistons to get away with such a lean mixture... but even then... lean means you run pretty hot... that would raise NOX... im interested to learn more about this engine!!!

 

Direct Injection technology is not used over here in the united states because of our poor fuel quality (i think direct injection uses 98 and101) so we will never see this technology (as in A/F ratios 65:1). Direct injection is common is europe and japan and was developed in the early 80s by mitsubishi, recently due to costomer demands for more fuel efficent cars Volkswagen and Honda have renewed intrest in this technology. As for 40 mpgs - i think it gets like 60 ... what will be interesting is when honda figures out how to integrate this new level of direct injection with hybrid technology ... i would estimate 100 mpg could be possible.
LexusFiend

P.S. I read about 6 months ago that the United States might get a "detuned" version of direct injection better suited to our fuel. Havent heard anthing else about it tho ...

 

With a 65-1 mixture, they don't really explain in the video just how detonation and pinging is controlled...... a MAJOR concern with ultra-lean mixtures like that and with high combustion temperatures and advanced spark timing. Under those conditions, a conventional computer-controlled knock sensor would have to retard the timing so far the engine would seriously overheat and barely run at all. I think part of the answer is the 98 octane gas that LexusFiend refers to......an obvious reason why we don't get that technology here(yet). But....keep one thing in mind. While we may not have the fuel quality they do in Europe and Japan, we're not paying $4-6 a gallon for it, either. (again........ yet)

 

Don't worry, Jim...you pretty much got it right.

Air-fuel ratio can change drastically with altitude, though, ...which is why most naturally aspirated (non-forced induction) engines produce maximum power at sea level and, under normal atmospheric conditions, lose power with altitude......a concern with piston-powered airplanes. Engineers use 59 degrees Farenheit and 29.92" air pressure as the standard for an engine's rated power. As you get higher, the amount of fuel going into the engine has to drop to keep the same AF ratio in the thinner air. Turbos and superchargers delay this (but do not entirely prevent it) . The highest altitude that a forced induction auto or airplane engine can maintain sea-level power is called the critical altitude. Above that,....... forced induction or not.....you will lose power because the air is too thin to be compressed to sea-level density.

 

maybe it's just me and I'm missing the boat here somewhere but everyone here is talking about A/F ratio and stating that (roughly) 12.0 to 1 is average for N/A engine. I'm thinking everyone is confusion this with compression ratio. the way I understood it (and if i'm wrong-my bad), compression ratio is how much the air and fuel is compressed when detonation occurs. A/F ratio would only be the ratio between the two as they are combined within the combustion chamber. So by stating 65-1 A/F ratio, it only means that the engine is very efficient in that the engine (which is a glorified air pump) can move 65 parts air with only 1 part fuel. This would have no bearing on compression and in turn not affect detonation in any way. Now, since they engine can work so efficiently on one part fuel, I am thinking that with forced induction the risk of detonation from running lean could be increased due to the small amount of fuel in the combustion chamber on each rpm cycle.

 

The compression ratio is different from the A/F ratio. A higher compression ratio means more power can be squeezed out of the engine, but at the same time increases the odds of detonation so that's why high boost applications will get lower compression pistons or head gaskets.

Now for A/F ratio, if you look at a dyno chart, along the bottom is usually a graph detailing the A/F ratio throughout the rev range. Usually towards the higher end (especially on high boost engines) conditions will lean out as boost rises. This is where tuning with an SAFC or something like that can control A/F levels so that an engine won't run too lean, then knock, then explode.

James

 

it said 35.2 MPG on the video, i think

and makes about 154hps /87 ft-lb of tq?

 

That's the point I was trying to make. Earlier posts appear to be confusing these two.

 

Though it isn't clear on which car the 35.2MPG figure was obtained, 35.2MPG just doesn't sound very impressive as today's Civic sedans are doing 32 city/38 hwy. The current engine produces 115hp/110 ft-lb of tq, so the new engine can be at best described as simply a higher-powered but less torquey replacement.

Interesting development nonetheless. Somebody has to try something new once in a while.

 

In regards to the A/F ratio being 12:1( or whatever you think is best, and it varies with application and fuel type) being best, that is at WOT. Not cruise, which is that they are talking about. I'm sure if you measured the A/F at WOT it will be much much richer. If you look at a "normal" vehcile today most will go into what is called "lean cruise" and this happens when the throttle hasn't been adjusted for a set amount of time. Something very lean like 18-19:1. You can do this without getting high combustion temps because there is no load. A good example is driving on the interestate with the cruise on. Once you adjust the throttle it will go back to a normal A/F loop and read the o2 senors again, and so on.

 

Maybe we don't get high quality fuel but hey look on the birght side ...
We do get White Fudge covered Oreos!

 

Isn't the new GS engine direct injection...?

James