Thread: Theory: Increased Engine load leads to better fuel economy

Did a few more highway trips and it does indeed seem like the only reason increased load actually improved MPG is because in increased load cells more optimal timing. Running less timing in lower load cells seemed to have improved my MPG driving on straight roads too.

Must be nice having 34mpg. My s13 with sr20 n ever break 20mpg. Highway or city

Just 34? Try 36.4 on my highway trip this weekend .

I got 37.8mpg with 22inch tires

Vadim you should email me your tcd so I can try that timing map out.. my mpgs suck.. even worse with SD..

Now is this just once, or are you consistently getting 37mpg? I've had one time fillups get 44mpg, due to pump inaccuracies. This is why I keep track of my mileage in a spreadsheet and try to fillup at around the same mileage city and highway, at the same pump.



This is with MAF, I had to hook it back up once the cold air set in, because my MPG's tanked with SD. On that SD tune while it was 70-80*F ambient I got 38.03 mpg, but as soon as 50*F ambient temp hit, best I got was 31mpg. As soon as I hooked the MAF up, got 35-36mpg. I'll send it to you still, it's rough base tune for cruising,it's 24* for from -25 inHg to -10, which is not a good timing map by tuning standards. But what's funny is, when I tried to smooth it out, aka make it more timing at -25 then step it down, I got worse MPG.

conservative mixed driving is closer to low 30's avg, but 100% highway mileage; 6th gear cruising around 70mph is ~38mpg

The statement that engines are more efficient at WOT is absolutely true, this is mostly due to higher volumetric efficiency because of less turbulence from the throttle blade frothing up the air.

A reason you may see better efficiency in a turbo car at slightly higher load, is that you are burning just enough fuel to spin the turbine just enough to feed the engine air without building boost, effectively eliminating the work required to pull the air in.

Engines are more efficient at WOT, doesn't mean they are more FUEL EFFICIENT though. Turbo does help reduce pumping losses really well. I personally gained 2mpg city just from dropping the turbo into my old VE, tune stayed the same (was already a turbo tune).

[QUOTE=Vadim;939767
Engines are more efficient at WOT, doesn't mean they are more FUEL EFFICIENT though. Turbo does help reduce pumping losses really well. I personally gained 2mpg city just from dropping the turbo into my old VE, tune stayed the same (was already a turbo tune).[/QUOTE]


It's the same thing. An efficient engine is fuel efficient. That's the defintion of a efficent engine.

I haven't read the whole thread but all you need to look at is:



BSFC (Brake Specific Fuel Consumption) = fuel consume/ power

Brake specific fuel consumption - Wikipedia, the free encyclopedia