[enkeivette]

Originally Posted by st-evo-9*corn fed-8urvet*

oh ya crystal ass clear!!!

so ya after my tune my highest vacuum is 10-9 in numerical value which yields me about 65mph at on cold nights or cold weather in general

but this is only because of my tuning. a stock evo would probably hit 50-60mph

and if u look at just about every stock tune out there

there fuel areas read at 14.7 in the idle and cruising cells in relation to engine load and rpm.

this is because 14.7 is the air/fuel ratio that is perfect for best emissions....all cars i have seen that have installed a wideband o2 air/fuel ratio monitoring system will read at 14.7 no matter where u are in the cruising area of ur stock tuned factory map

so in essence u arent really gonna yield to much better gas milage by letting off the throttle because the car is always gonna compensate the afr and make it 14.7:1 which most cars to get the best fuel efficiency there afr needs to be at 15.8:1 to 16.1:1 on petrol based fuels.

That's interesting, pretty damn lean, does it run any hotter like that?

And the AF ratio in a normal engine can also be 14.7:1 at WOT, with more fuel/ air consumption. Trying to see here where there is the least fuel consumption, because 14.7 is just a ratio.

[st-evo-9*corn fed-8urvet*]

Originally Posted by enkeivette

That's interesting, pretty damn lean, does it run any hotter like that?

And the AF ratio in a normal engine can also be 14.7:1 at WOT, with more fuel/ air consumption. Trying to see here where there is the least fuel consumption, because 14.7 is just a ratio.

normally what ull find is on well built and cooled motors have these general afr's

rememer this is for petrolium based fuels IE. 91, 100, C16 octane's etc....

16.1:1 = best fuel consumption for running the engine at its leanest

14.7:1 = best fuel emissions reason y all cars read this almost everywhere

12.5:1 = most power potential.

as for my afr of 18.1-17.8 its because im running ethonal E85 and it cools the combustion temps which in turn cools the egt's my egts are around 800F while cruising when they used to be at 1400F on my gas tune at 14.7afr. also e85 is highly oxygenated so its gonna raise that air part of ur afr.

so what might be a 14.7 afr on gasoline, would in turn be a 16.4:1 on e85

really if u guys couldnt tell im enjoying everyday im running this hippy corn shit

also when u get into the most efficient power, and best fuel consumption afr for e85 things kinda get mixed up.

im not even sure of what the best afr for e85 is because of its high oxygenation which in the tests ive done in my car have seemed to end up being the 18.1:1 range and the engine actually starts starving for fuel but doesnt over heat. u just get split random nano seconds of random cylinder misfire.

and in theory the best power ratio for e85 is around 9.4:1 i believe but if u run it that rich it bogs ur engine down alot!!!

but in reality ive found that 12.5:1-12.8:1 seem to do just dandy for the best power ive made out of e85.

im sure with a direct injection motor such as the one found in the solstice u could get more power out of a richer fuel ratio for gasoline and e85.

[94cobra69ss396]

I ran the Cobra today and recorded the vacuum at 55, 60, 65 and 70. At 60, 65 and 70 I had 12 in. HG and at 55 I had 10 in. HG. This got me thinking, as long as you have enough power to cruise at the given mph without loading the engine you should have higher vacuum the higher the rpms are. To test this I dropped the car at 65 from 6th gear to 4th gear and the vacuum increased to 15 in. HG while still cruising at 65. Not sure what this means because I'm not an engineer.

[SeanPlunk]

Interesting stuff - I'm actually glad you started this thread Enkei

[BRUTAL64]

Originally Posted by 94cobra69ss396

I ran the Cobra today and recorded the vacuum at 55, 60, 65 and 70. At 60, 65 and 70 I had 12 in. HG and at 55 I had 10 in. HG. This got me thinking, as long as you have enough power to cruise at the given mph without loading the engine you should have higher vacuum the higher the rpms are. To test this I dropped the car at 65 from 6th gear to 4th gear and the vacuum increased to 15 in. HG while still cruising at 65. Not sure what this means because I'm not an engineer.

The main thing to look for is highest Vac in inches and the lowest possible RPM. As your speed increases the greater the resitance from air itself.

[94cobra69ss396]

Originally Posted by glenn64vette

The main thing to look for is highest Vac in inches and the lowest possible RPM. As your speed increases the greater the resitance from air itself.

So theoretically since I had 12 inches HG at 60, 65 and 70 I should get the best gas millage at 60?

[enkeivette]

Originally Posted by glenn64vette

The main thing to look for is highest Vac in inches and the lowest possible RPM. As your speed increases the greater the resitance from air itself.

Originally Posted by 94cobra69ss396

So theoretically since I had 12 inches HG at 60, 65 and 70 I should get the best gas millage at 60?

And ya, theoretically.

[94cobra69ss396]

Well, I have to drive out to Phoenix in September for business so I'll do some testing and let you guys know what I find.

[enkeivette]

Originally Posted by 94cobra69ss396

Well, I have to drive out to Phoenix in September for business so I'll do some testing and let you guys know what I find.

Sweet.

If you have the patience, do 55 one way and 60 going the other. This would be the tell all about the vacuum theory.

[94cobra69ss396]

I'd did some testing today because I had to drive out to L.A. to visit a customer. I filled up at a gas station right before I got on the freeway and set the cruise control for 60. After visiting my customer I stopped and filled up the tank before getting on the freeway to head home. I had gone 67 miles and pulled 27.202 mpg. On the way home I set the cruise control at 55 and filled up when I got off the freeway. At 55 I only pulled 22.218 mpg. This was in my Cobra which has 3.55 gears, 245/45/17 and a T56 with a .72 overdrive.