Another thing, check this out. If you could actually achieve a mixture approx 14.7:1 in the top of the chamber, with the rest being just air, then what would happen to the nox emissions? I think they would be low, because the stoichiometric **** would would burn quickly like normal, and the rest of the air wouldn't get hot enough to create the oxides. Or would the presence of the extra oxygen work against that and sabotage my theory?
I do know that the egt would be really low.

 

Acutally NOX is at its highest at just slightly lean of stoich....like 15.5:1 or so. NOX likes heat...when I get home I will get my graph of how CO, NOX and O2 relate accoring to AFR

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rorik &raquo;</TD></TR><TR><TD CLASS="quote">Go leaner, then make less power, then give more throttle, which then burns more fuel? So then the net result is burning slightly less fuel due to a reduction in pumping losses? Intuitively, that makes sense..sort of.. but I still think there's more to it than that.</TD></TR></TABLE>

The point here is to make it so lean that you actually need more throttle to maintain the rpm at a particular A/F. Which is more efficent. If you let RPM go up, then you're actually using more fuel.

 

well yeah, if you increase your rpm, then you're going to burn more fuel..since when has driving faster resulted in a mpg improvement!

However, I think more of the reason why running somewhat lean or burning with a stratified charge results in a lower bsfc is because it results in a higher dynamic compression..more efficient

 

edit...wrong topic oops

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rorik &raquo;</TD></TR><TR><TD CLASS="quote">well yeah, if you increase your rpm, then you're going to burn more fuel..</TD></TR></TABLE>

that isnt true.

some engines may be much more efficient at higher rpms.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase &raquo;</TD></TR><TR><TD CLASS="quote">that isnt true.

some engines may be much more efficient at higher rpms. </TD></TR></TABLE>

I thought it was a given that at higher RPMs an engine might take as much fuel as it takes it to idle.

 

how?

 

Because at higher RPM's the engine is more efficient. Fuel is atomized better, more RPM's gives less time for pre ignition and detonation, and im sure there is more reasons but that is all I could think of off the top of my head

 

Somehow I dont see how swapping out an ls final drive for a type r is going to give you better mpg.

 

It wouldnt...It would give you worse mileage because at 75mph in 5th gear would be put at a higher RPM than the ITR would give you. Less load...but Im pretty sure it would use more fuel

What I was saying is that at idle, huge fuel injectors seem to puddle and requre a lot of fuel to obtain the target ARF. At higher RPM's and boost levels, the fuel is atomized really well and could use just as much fuel at 5000rpms as at idle

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase &raquo;</TD></TR><TR><TD CLASS="quote">

that isnt true.

some engines may be much more efficient at higher rpms. </TD></TR></TABLE>

I don't know what you mean by efficient. Care to elaborate? I'm having trouble picturing how increasing your cruise rpm could result in increased mpg..if that's at all what you meant.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rorik &raquo;</TD></TR><TR><TD CLASS="quote">

I don't know what you mean by efficient. Care to elaborate? I'm having trouble picturing how increasing your cruise rpm could result in increased mpg..if that's at all what you meant.</TD></TR></TABLE>

I believe he is talking about Ev (volumetric efficiency), I assume you know what this is but just to define in simplistic terms (cause that is the only way I understand it), it is the actual amount of air that the engine pumps vs. the amount of air that it would idealy pump. An engine is just a complicated air pump right? I have read the same thing, that some engines are much more efficient at higher rpms (pump better).

 

I think you may have to do a lot of testing under controlled conditions to see where you will make the most gains in your fuel economy. The VE (Ev) of the engine may increase at higher rpm, but the injection event is happening more often than if you had lower RPM. If you are tuning to a specific A/F, then you would also have to increase the fuel output at the higher RPM point to make up for the higher VE.
There is a point, as mentioned earlier, where a loss of power results and an increase in RPM/throttle must be made to compensate for it. You will not find a magic A/F that will give you Geo Metro fuel economy and 300 HP... You can play with it so that you can retain a lot of your factory fuel efficiency for cruise, but you typically will not see any gains. If you do see gains, it will more than likely be because you are not in closed loop mode and no O2 cross counts are being made. You could retain a higher A/F the entire time, though your catalytic converter (if people even use them...) won't work very well and you will probably have higher NOx output.
I've been able to tune my car to over 34 mpg highway/mixed (mostly highway) with the turbo and engine swap. Before the changes I averaged 35mpg highway on the D16. I've run as high as 16:1 A/F during cruise with a slight increase in EGT (100 deg) and have not encountered knocking etc. I have closed loop disabled and am running entirely off my map. The 34 mpg average was done on 15:1-15.5 A/F cruise with little to no change in EGT under low load. When the engine approaches 0 vac/boost (-4in/hg), my maps compensate heavily for the load and I have everything tuned to around 12.1-12.5 A/F for those conditions.

 

just read this and it really makes me think more for when im going to street tune my car pretty soon when i get my exhaust on

 

I have a question regarding tuning ignition.
I have read that you should add timing just after Max Torque.
Is there a specific amount or a guide?
Like what we have for Air/Fuel Ratios?

 

2

 

Would running a conservative timing hurt the torque?
My torque drops after 6 grand.

 

I believe timing is directly related with tq. So in essence it would help get your tq up. Also since HP is product of TQ.

 

Back from the dead!
Alot of good info in this thread. Would be nice to read some more good info added to this already great info. Anyone care to elaborate?