Will fuel consumption be worse or better with a built motor provided that the power output is kept the same. So if you went for a 8.5 CR build (stock cams)and tuned to the same target AF's and power does this mean consumption will remain the same etc.

 

to get the same power curve on a lower compression car, you need to run more fuel and timing.

if it was stock compression, no reason fuel consumption would drop.

 

Stay off the Boost and you will not notice the difference

 

When I took my car to Orlando it took a tank and a half to get there. It only took a little over a tank to get home and that was with a little fun on the way home too.

 

At the moment i'm getting 380kms/70L which is about 236miles/18.5 gallon. With the way fuel prices are in australia it is costing me about AU$122 to fill up which is quite expensive.

This is on my HKS ST with PE510's and stock CR

Need to work out if I keep the car or buy something that is a bit more economical.

 

12.75mpg... how do you drive? If this is normal driving and not aggressive / constant boosting, then you need to look at your tune. Sounds like the car is too rich under normal conditions.

 

werd
when i had my tn kit i woudl get better gas milage actually...since most of the driving was under vaccum and i would be running leaner than stock

 

My only input on this would be...
You will need a good tune on the stock setup, then a good tune on the built setup to compare.
What I am saying is you cannot compare the stock computer setup to a tuned built setup. The factory settings are going to be extremely conservative.....very rich with very little timing (they have to be safe afterall). Purely optimizing the stock tune will net you more power and better mileage right off the bat (you'll be sending less fuel to the cyclinders and burning it more completely/efficiently)

T

 

Approx 10mpg when driving hard

24mpg cruising on the highway

 

Forgot to mention that I'm running the Haltech as the ECU. I have attached a shot of my target AF's. From what i can see during driving the AF's do match the table etc. I personally thought my car was running rich so I compared my haltech WB to another manufactures one during driving and they are pretty close even though the haltech is pre cat and the other one was at the exhaust tip.

My driving style is not IMO considered hard or aggressive. Give it a squirt now and then and used as a daily driver to work.

Boost = 7psi

 

380 is pretty poor. with my APS TT and unichip i get around 450-500 around town. 500-600 if i mix it with hiway driving.

Ive tried all sorts of things to increase my fuel consumption. These days i skip gears alot, 1/3/5 around town. or 1/2/4/6. I found that by doing this, i can easily pickup k's. Add some grandma style driving into the mix, keeping the revs low and now throttle blipping, i can increase fuel consumption to 50-80kms more a tank. but anything more then grandma driving i find that i can be at fullboost and still get similiar mpg.

These are definatly hungry motors.

 

Power takes fuel

 

What is the stock compression? ~10.5?

Has anyone done a built motor with close to stock compression? If not, is it because it easier to avoid knock/detonation, etc? People have hit 500whp on the stock block. I am asking because the power drop when not in boost with a lower compression motor is noticeable compared to a stock block.

 

Well i wonder who was steeling all my power when it was stock.

VE = fuel usage per kw. Nissans arnt exactly VE monsters.

 

If i was getting 450-500 i would be happy. Is yours a stock block and what boost etc?

 

I think it's all in the tune.. I'm getting pretty similar km/L as you... Also, I know that my tuner is known to be very conservative tuner, so I kind of expected in the back of my mind...

 

stock block, stock aps kit with 2.5" exhaust, jwt flywheel and plenumn spacer. stock boost. and a very conservitive tune, into the 10s in boost, it was tuned for power output, and stopped around 380hp to keep the stress on the engine at a minimum.


Edit: i just filled up my car after
280km hiway
280km city (not much boost, skipping gears)
and i pull 65L into the tank to fill her up. So yeh, its probably one of my best MPG's.

This car takes alot of care to get it acheiving good MPG. I found that u either get good fuel eco, or **** fuel eco. A bit of boost every change, and u might as well take her to redline.. Mine was tuned by Spiro.

i just read ur 380km/70l.. I would expect that kind of figure if i had been tracking or beating the hell out of the car the entire tank... Its pretty poor i must say.

 

By built, I am assuming you mean 'built and boosted'.

A naturally aspirated motor in a factory tune is intentionally very conservative and therefore slightly rich and 'sloppy'. A motor that is correctly engineered, boosted, 'blue-printed' and tuned will be far more efficient and get better 'gas mileage' under cruise conditions than the factory build.

Under boost conditions the motor will do what it is designed to do, which is convert air and fuel (and lots of it) into motive force. The 'gas mileage' will drop dramatically.

My car, when naturally-apirated, used to get about 22-23 mpg travelling 30 miles to work on the interstate. Now it gets about 26 mpg under the same conditions with the improvements mentioned in my sig. A day at the track it drops to about 13-15 mpg.

Ultimately, it is a matter of mechanical/chemical efficiency. Good engineering costs money but it does get results.

 

Maybe my closed loop is where my issue lies. I have logged my WOT previously and it is was a solid 11.5 AF from memory.

Didn't mention this before but my WB which i use for closed loop is pre cat but this is located near the shift leaver. This may not be the best or ideal position as it is too far downstream. Haltech modded my map background calculation so that the WB would react quicker to compensate for the distance but maybe this is not perfect. Might get a O2 simulator for the factort O2's which sit about 6-8" from the turbo and move the WB up to one of these bungs.

 

What kind of a/fs are you seeing at idle?