Modified Car? How Bad Is Your Fuel Economy?

[ausdrift]

So having got a respectable amount of engine work done I've now noticed that my previously poor fuel economy has managed to get even worse. And I naively thought it would get better with a tune...

So, I thought I'd put it out there to find out if others enjoy just as poor economy as a result of daily driving your modified Skyline.

Car - ECR33 Skyline

Power - 235rwkw, 430 N/m

Kms to a tank - 300 max

Go!

[zebra]

That's terrible

I was getting 400+ks to a tank of E85 in peakhour to and from work

[Hadouken]

Honestly it's pointless saying xx k's to a tank.

What is your l/100km?

[Ben C34]

How big is your tank?

[scotty nm35]

How hard do you drive it? I go through 20L in a 5 minute session at Sandown.

I can get down to 10L to 100k's in the evo on e85, the stagea is generally twice that on the open road.

Injectors play a large part, do you know how much of the fuel is being sprayed onto the walls of the ports rather than towards valves? How small are the droplets? Most people would have no idea I guess.

[ausdrift]

If you were to state your vehicle, then using "per tank" is fine as its consistent.

But ok, lets simplify this then by doing L/100

Which in my case is a shocking 18L/100kms and that's largely putting to and from work.

I think I have to have a word with my tuner as although I have Nismo 740cc injectors, Z32 AFM etc, economy should be much better than that...

[jiffo]

Mostly it's going to come down to the right foot. Heavy foot, crap economy.

Your power certainly isn't out of the box, loads of much higher hp cars doing respectable L/100 numbers.

If the car doesn't have cams or adjustable cam wheels it should be pulling a nice manifold vacuum. You'll see a big drop in economy once you alter cam timing/valve overlap.

What's the static compression numbers, won't get good off-boost economy from a low compression engine.

And finally the tune, very few tuners will spend time on the light load points and that's where most of us drive for economy.

[mr skidz]

And finally the tune, very few tuners will spend time on the light load points and that's where most of us drive for economy.

Hit the nail on the head right there [emoji115]

[admS15]

I have similar setup to you ausdrift. Making 248rwkw with nismo 740's. Get around 12-13l/100 in grandpa mode and 14-15l/100 driving with a fair amount of right foot. I did ask my tuner to focus on economy. My cruise afr's sit between 14 and 15 to 1. Your car is definitely using too much unless you are constantly on boost.

Edit: That is all around town, start stop driving. Freeway would obviously be much better.

[89CAL]

I think i was getting around 15-16l/100km with Nismo 740's and Hypergear SS2. Just put EV14 1000cc's in so thinking economy is going to improve a bit now

The figure i gave for economy was mixed driving. I never manage to do a proper economy run on a tank lol

[jiffo]

I'd forget any city figures, it's just not worth the effort.

But a highway test (without crazy RPM overtaking) I'd expect no worse than 10L per 100.

My stock RB26 does 10 highway driving.

I added the trailer and it went 20 to 25. (I couldn't do the 350K trip with my 72L tank)

Car was always on boost, so poor economy.

[KiwiRS4T]

The Stagea uses 12 - 15L/100km round town with a reasonable amount of boost. Would have to really thrash it to get 18L/100

(km per tank is far too vague as I assume you don't drain the tank each time and the amount left will vary).

[ausdrift]

The tuner I used is very reputable, and I did emphasis the fact that its a daily and I wanted a smooth reliable driving experience, so I assumed he would have made it good down low too.

On the daily work grind there is little opportunity to get on boost, so I'm almost always driving relatively conservatively. Hence my confusion...

[t_revz]

Rb25. cams, modified head, port/polish, hypergear SS2, nismo 740's.

9.7l/100 on 3/4 highway run and 1/4 hills section on the way to work. Get 600km out of a tank and still just off empty. Would guesstimate about 8.5 on highway only

[ausdrift]

Jeeeeeeeeeeezzzz, that's good

[t_revz]

Jeeeeeeeeeeezzzz, that's good

How many litres do you squeeze in after your "300 max"?

[niZmO_Man]

How many litres do you squeeze in after your "300 max"?

About fifty bucks? LOL

[zoomzoom]

You need some some data on whats going on. Do you have a wideband? What ECU are you running and can you show a timing map?

Just sounds like a combination of being rich and not enough timing where you drive 90% of the time.

Even as an amateur tuner I get better fuel economy than stock. I made sure the open loop map was as close as possible to the target AFRs

[jiffo]

Rb25. cams, modified head, port/polish, hypergear SS2, nismo 740's.

9.7l/100 on 3/4 highway run and 1/4 hills section on the way to work. Get 600km out of a tank and still just off empty. Would guesstimate about 8.5 on highway only

That's a great result.

No2 son's 33 would do similarly, I used to worry once 600k's rolled over but it never ran out.

[V28VX37]

Honestly it's pointless saying xx k's to a tank.

What is your l/100km?

^^^This. I don't know how why it's so hard but kms/tank is so not a useful measure, even if you know the (dry) tank size, as it's never 100% empty or full.

For a useful measure of economy you need to look at l/100km (or MPG), over time.

If you were to state your vehicle, then using "per tank" is fine as its consistent.

But ok, lets simplify this then by doing L/100

Which in my case is a shocking 18L/100kms and that's largely putting to and from work.

I think I have to have a word with my tuner as although I have Nismo 740cc injectors, Z32 AFM etc, economy should be much better than that...

What turbo and how much power? 18l/100kms is not necessarily that bad, depending on context.

Here's some of my figures for comparison (275rwkw @ PULP, Hypergear SS2, 850cc injectors, Walbro 255):

• Freeway 10-12l/100km
• City 12-15l depending on traffic
• Track 20+

Stop-start traffic absolutely kills any economy.

Still, my previous 5.7L cam+heads 290rwkw+ LS1 was north of 20L BP98 in city traffic, so in comparison the Skyline is an econobox