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Lean Mixture


James Matteu

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I have been asking the local shops about turbo charging the Accord and piggy backing the ECU for fuel management. I get about that far until I tell them I have a V6 and that I want to use the smallest turbos possible in order to tune it for roughly stock HP but an increase of 10-15 mpg. Their eyes glaze over and I get shoulder shrugs and idunnos.

 

When Honda introduced their first Turbo, it was their 1983 750cc motorcycle that was heralded as the power of the 900cc with the fuel efficiency of the 500cc. So, my idea is at least in the spirit of Honda turbo. The bike did the job with a .75in turbo. If I could improve mpgs, the upgrade would pay for itself over time.

 

So, here's the question: how low can I go? I know 14.7:1 is standard, will it stall on 20:1? 30:1? 60:1? Does anyone have any sources for this kind of information?

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Thank you, no wonder I cannot find any data on high lean air-fuel mixtures. I guess the test motor does not last long enough to generate data.

 

You know it really bugs me, how was Honda able to use forced induction to make a more powerful engine while increasing fuel efficiency.

Edited by James Matteu
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I'm pretty sure that when gasoline cars use turbos for efficiency, they are using them to overcome pumping losses generated by sucking a vacuum in the cylinder on every intake stroke at part throttle.

 

Diesels don't get all their efficiency from the fact that they can run SUPER lean (plays a big role), but it also comes from the fact there is nothing holding the piston back on each stroke downward.

 

EDIT: A turbo diesel efficiency gain is somewhere in the ~4-5% range over that of a non turbo diesel.... When your burning over a gallon in just ten miles, that 4% can really help out.

Edited by Pyrorocketeer
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I'm pretty sure that when gasoline cars use turbos for efficiency, they are using them to overcome pumping losses generated by sucking a vacuum in the cylinder on every intake stroke at part throttle.

 

That is actually another idea I had. Bone stock motor with a dry sump system installed.

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well... I wasn't exactly referring to oil, but parasitic loss due to oil windage would increase power and efficiency some.... might not be the most economical, but it would help. then again, polishing every surface inside of your block would too.

Dry sump would also help alleviate a lot of excess crankcase pressure, which would help too.

 

I was referring to the vacuum your engine pulls when it tries to pull a whole cylinders worth of air through a small crack in a throttle body at part throttle.

 

 

Want to do some good reading about ICE efficiency, read up on Smokey Yunick's hot vapor cycle engine.... Who knows if it could actually run, (It is said that it did, but the numbers don't quite work out) but its really neat some of the stuff that he thought of.

 

In fact, read up on any of the different kinds of ICE, there are some out there that will blow your mind....

Edited by Pyrorocketeer
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I was referring to the vacuum your engine pulls when it tries to pull a whole cylinders worth of air through a small crack in a throttle body at part throttle.

 

Now I see what you were saying, I agree.

 

up on Smokey Yunick's hot vapor cycle engine...read up on any of the different kinds of ICE, there are some out there that will blow your mind...

 

I have checked out a few ICE designs, some exotic, some look like paper dreams. I have to admit, I had never heard of Smokey Yunick, until now.

 

My ideas are all in the spirit of retrofit to existing motors to increase efficiency, starting with mine:

 

dry sump

small turbo

fuel management

shutting off a pair of cylinders (V6 to V4)

miniscule nitrous feed

properly inflated tires

not driving like an idiot

and the classic: keeping up with regular maintenance

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I think what you'll come to find is that if you come to all the cost of all that up, it will take years to start seeing any costs benefits if there are any.

 

dry sump $500-700

turbo >$400

 

shutting off cylinders, Doesn't your v6 shut off one back of cylinders during cruise? Else, you will have to do a lot of work to shut off cylnders.... problems with oxygen sensor false readings, CEL's from injectors not working correctly, uneven head temps if you shut off single cylinders, and could cause warpage. Plus you still haven't overcame the pumping losses of that piston unless you can shut off the valves.

 

nitrous as an extra source of oxygen.... eh.... at almost $40 to fill a bottle, probably not worth it. Take into account probably 300+ for the nitrous setup.

 

inflated tires, and not driving like an idiot will yield some amazing results. Check out gassavers.org they have some pretty neat ideas for fuel efficiency over there, a lot has to do with simple aero mods, and driving techniques.

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it will take years to start seeing any costs benefits if there are any.

 

True, and I am not one to save gas for the sake of saving gas at any expense.

 

dry sump $500-700

 

I didn't know that.

 

Doesn't your v6 shut off one back of cylinders during cruise?

 

No shut-off, I have a C27, old skool.

 

...unless you can shut off the valves.

 

I overlooked the "dead cylinder effect", but your right. When my CRX was dying, I drove it on 3 cylinders for a few months. I always wondered if I could get it to do this but smoothly (since a CRX on 3 is anything but smooth).

 

I am going to check out gassavers.org, thanks again.

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Yeah the biggest expense with the dry sump is the pump itself. then you need to modify your oil pan, a place to put the tank, lines to run to it....... it adds up.

 

you can get it to fire on 2 "smoothly" above a certain rpm.... 3 just shakes the piss out of everything. lol.

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  • 1 month later...
So, here's the question: how low can I go? I know 14.7:1 is standard, will it stall on 20:1? 30:1? 60:1? Does anyone have any sources for this kind of information?

From: http://paultan.org/

 

"An engine that has surfaced and pretty much faded in a short time is Honda’s i-VTEC I Engine, a variant of the K-series DOHC engine family featuring gasoline direct injection. It made it’s debut in the previous generation 2004 Honda Stream 7-seater MPV in Japan, but the current Stream does not use this engine anymore, instead using a 2.0 liter version of the R-series i-VTEC SOHC engine.

 

The engine featured the ability to use ultra-lean air-fuel mixtures of about 65:1, much leaner compared to the the usual direct injection engine 40:1 ratio, and of course so much more leaner than the stoichiometric air-fuel mixture of 14.7:1 - this saves fuel. Fuel consumption dropped to 15km per liter. Power ratings remain the same at about 155 horsepower. This engine in the Stream is mated to a CVT gearbox with a manual 7 virtual gear shifting feature.

 

Honda also had a demonstration engine back in end 1999 where a 1.4 liter DOHC Honda engine was equipped with a VTEC-DI system. This was Honda’s first demonstration of direct injection to the public. The engine was installed in a Honda Logo (the predecessor to the Honda Fit/Jazz) and made power and torque outputs of 107 hp at 6200 rpm and 133 Nm at 5000 rpm.

 

Check out a video of the i-VTEC I engine after the jump."

 

i-vtec-i-engine.jpg

 

No chance of retrofitting direct injection to my C27. So I guess that pretty much kills my thread question.

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if you want your engine to last , you tune it to run about 12:1 on a turbo car at WOT , bit less perhaps. when your ecu is in closed loop , it always commands 14.7:1(which can be changed on vehicles able to be tuned). when its in open loop , it reads off the map solely. an NA car should be tuned to 13.2:1 at WOT. same for crusing as turbo car , crusing AF is always stoic. it ensures healthy long lasting engine to live by these numbers. and less chance of detonating. assuming your AF is on and tuned , timing is where the power comes from. running as advanced as possible without causing knock. you cant run as much timing on a turbo car. running better fuel , allows more timing. if your engine has detonation or pinging , theres 2 solutions , better fuel , less timing. as far as how lean can you go without stalling? i really dont see the validity of the question , as you simply cant run an engine like that. these rules are universal unless you run alcohol(very knock resistant , can run alot of timing without knock) , or some other kind of fuel or setup than conventional.

Edited by cranny
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i really dont see the validity of the question , as you simply cant run an engine like that.

It appears this is the rule for a motor such as mine, the C27A4. I see that now.

 

I was interested in using fuel management on my C27A4 to accomplish what Honda has done with their direct injection (VTEC-Di) design; which is a 40+:1 AF ratio to improve fuel economy.

 

Again, I see what your saying and realize this cannot be done to my Honda V6.

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  • 2 weeks later...
  • 1 month later...
Thank you, no wonder I cannot find any data on high lean air-fuel mixtures. I guess the test motor does not last long enough to generate data.

 

You know it really bugs me, how was Honda able to use forced induction to make a more powerful engine while increasing fuel efficiency.

 

You might be able to find some information along that line by Googling "Miller Cycle Engine". The Mazda Millenia had this as an option. You may not achieve what you're trying to do from this information but it will give you some guidance.

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