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Leighos 12-14-2010 04:41 PM

Hi From New Zealand
 
Hey Ecomodders,

I'm new here but have been interested in getting good fuel economy for many years. I often drive with economy in mind and have also done a few improvements to my vehicles to help improve the fuel burn figure.

My 1994 Subaru Legacy RS (Japanese import) gets on average 20 MPG combined cycle (here in NZ we are metric, but I don't mind converting for you guys :D) and thats with the occasionally boost up to full power, it is my weekend a fun car after all!
I've owned it for 7 years now, and in its originally spec it was a 2.0l twin turbo, terribly inefficient and fuel guzzling!
I have converted it to a single turbo turbo setup, which un-complicates a very complicated and inefficient induction system.
Added a free flow cat-less exhaust (we dont have emission testing here, yet).
I've also increased the ignition voltage to 16v, which actually does create more complete fuel burn and has slightly increased mileage, so far I haven't burnt out any coils so thats a bonus!
I plan to fit mpguino soon (its OBD1) to keep a better eye on fuel consumption. 20 mpg is not impressive I know, but for a 4wd car thats capable of 300hp thats quite respectable it think, and there are still improvements to be made that wont compromise performance or reliability too much.

My daily driver is a 1992 Isuzu MU, I think in the US they are called a GMC Amigo? Anyway its a small SUV with a 2.8l turbo diesel engine. It returns a reasonable 30mpg on a combined cycle. I'm happy with that for now, diesel has gone up to $1.30 a litre so I'll be looking at doing a few mods soon to stretch the economy even more. One idea I have is to fit a fuel pre-heater before the injector pump (yes mechanical diesel injection) that is heated the fuel slightly by the engine coolant flow.

I look forward to sharing ideas with you all in the near future.
Bye for now,
Leigh.

tumnasgt 12-14-2010 06:06 PM

Welcome to Ecomodder, it's cool to see another NZer on here.

What part of NZ are you from? I'm from Wellington, one of the biggest tricks here is learning to use the hills to your benefit: not going too hard on the gas on the way up and using engine braking (DFCO) on the way down.

Leighos 12-14-2010 06:59 PM

I'm in Hamilton, the Waikato is reasonably flat so I mostly employ 'light footedness' and driving without brakes (in the diesel).
I've ofter wondered, would fuel consumption be comparable driving economically in hilly areas to driving economically in flatter areas?

tumnasgt 12-14-2010 08:00 PM

Quote:

Originally Posted by Leighos (Post 209528)
I'm in Hamilton, the Waikato is reasonably flat so I mostly employ 'light footedness' and driving without brakes (in the diesel).
I've ofter wondered, would fuel consumption be comparable driving economically in hilly areas to driving economically in flatter areas?

Depends a lot on the hills. If the hills are so steep that you have to brake on the way down, it's often less efficient. But if the hills are enough to maintain speed in neutral or with light engine braking (just enough to get deceleration fuel cut off), you can often get better fuel economy than on the flat.

Driver skill comes into play a lot more on hills, and manual transmissions really shine in comparison to autos (especially on the way up).

Are your cars manual? If they are, what at what kinda revs do you shift up?

NeilBlanchard 12-14-2010 09:26 PM

Welcome to EM, Leigh!

I've been to New Zealand -- does that count? We visited for about 2 months, back in 1982. It's a wonderful place.

Leighos 12-14-2010 09:47 PM

Quote:

Originally Posted by tumnasgt (Post 209538)
Are your cars manual? If they are, what at what kinda revs do you shift up?

Yes both my vehicles are manual, I've actually never owned an auto!

With the Subaru, when I'm driving economically, I drive totally off boost and change up around 3000. If figure keeping the manifold pressure low but still using adequate RPM to best use the engines torque, is a good way to keep the fuel burn low.
Although my concern with turbocharged petrol engines when driving off boost, is effectively they are acting as a normally aspirated engine, but having a very inefficient compression ratio (My Subaru is 8.0:1) and a restriction in the intake (the turbo and intercooler). I guess its all about compromise though with auto engines.

With the Isuzu, apart from idling, the engine is mostly always running in boost pressure, this is where turbo diesels are very efficient. I maintain around 5psi of boost and get to 2500 RPM before I change up, this seems to be a good balance of useful torque and economy. Incidentally, I also cruise at 2500 RPM in 5th gear, it give approx 85km/hr road speed which better suits the vehicle's aerodynamics also.

What sort of tyres do you run?
The Isuzu used to have 15" 'all terrain' tyres, not that great for rolling efficiency. I managed to get a set of 18" alloys with proper road tyres, I reckon that made quite a difference to economy (and road handling).

Leighos 12-14-2010 09:51 PM

Quote:

Originally Posted by NeilBlanchard (Post 209552)
Welcome to EM, Leigh!

I've been to New Zealand -- does that count? We visited for about 2 months, back in 1982. It's a wonderful place.

Of course it counts ;)

Come back for a visit again sometime, its still a wonderful place.

tumnasgt 12-14-2010 10:30 PM

Quote:

Originally Posted by Leighos (Post 209556)
Yes both my vehicles are manual, I've actually never owned an auto!

With the Subaru, when I'm driving economically, I drive totally off boost and change up around 3000. If figure keeping the manifold pressure low but still using adequate RPM to best use the engines torque, is a good way to keep the fuel burn low.
Although my concern with turbocharged petrol engines when driving off boost, is effectively they are acting as a normally aspirated engine, but having a very inefficient compression ratio (My Subaru is 8.0:1) and a restriction in the intake (the turbo and intercooler). I guess its all about compromise though with auto engines.

With the Isuzu, apart from idling, the engine is mostly always running in boost pressure, this is where turbo diesels are very efficient. I maintain around 5psi of boost and get to 2500 RPM before I change up, this seems to be a good balance of useful torque and economy. Incidentally, I also cruise at 2500 RPM in 5th gear, it give approx 85km/hr road speed which better suits the vehicle's aerodynamics also.

What sort of tyres do you run?
The Isuzu used to have 15" 'all terrain' tyres, not that great for rolling efficiency. I managed to get a set of 18" alloys with proper road tyres, I reckon that made quite a difference to economy (and road handling).

If your Subaru's gearing allows it, I'd recommend changing up around 2300rpm, as engines are typically more efficient at lower RPMs.

On the highway I try to stay at around 90km/h, which is around 2500RPM in the Camry and around 1900RPM in the Sonata (if only manuals had gearing like that). 90 is good because it's the legal limit for trucks, so people get less pissed off than if I was driving 85. Sometimes I'm impatient and drive at 100 though :)

Leighos 12-15-2010 02:27 PM

Quote:

Originally Posted by tumnasgt (Post 209562)
If your Subaru's gearing allows it, I'd recommend changing up around 2300rpm, as engines are typically more efficient at lower RPMs.

I have tried shifting at lower RPMs, the problem with this car is due to its relatively low compression ratio and transmission drag (full time 4wd), if the RPM drops below 2000 after a shift, the engines needs to pull a lot less vacuum to recover, resulting in more fuel usage.
Without the use of an accurate fuel consumption gauge of some description, this is only an educated guess, but my current driving style does yield a lot more mileage than other techniques I have tried.
I'd like to build a mpguino or something similar in the near future.
Do you use anything other than odometer to monitor fuel consumption?

tumnasgt 12-15-2010 03:16 PM

Quote:

Originally Posted by Leighos (Post 209671)
I'd like to build a mpguino or something similar in the near future.
Do you use anything other than odometer to monitor fuel consumption?

I'd like to get a proper meter, but the Camry isn't OBD-II, so it'd have to be an mpguino, but we might be selling it soon so my mother doesn't want me modifying it. For the Sonata, a Scangauge is a bit pricey, and we are considering downsizing it to a civic hybrid or similar, so an mpguino isn't an option for now in case we do sell it.

The Sonata has a trip meter for fuel economy, but it's not very accurate (look in the fuel log, I have the meter vs actual in the fill up notes). It's nice though because it finally got my mother to start driving more efficiently, even with the slushbox and bigger car, she is using less fuel in the new one than she used to in the Camry.

Leighos 12-15-2010 07:04 PM

I've been considering down sizing too, my wife and I don't have children - so a smaller, more economical car would suit us better.
...But I love my old Subaru, and for sentimental reasons it would be damn hard to let her go!
The Isuzu is really useful too, towing trailers and carrying loads etc, plus its cheap to run being a diesel so it gets driven to work everyday.
I'm not convinced hybrids are the way to go, their mileage isn't all that impressive compared to some new generation diesels, and I dread to think how much a new battery would be when it comes time to replace.

One choice that gets quite overlooked in this country are CNG powered vehicles, CNG used to be really popular in the 80's but only buses now seem to use it? I wonder if it will ever make a comeback?

tumnasgt 12-15-2010 07:26 PM

We would be getting a used car, and diesels are really expensive. There are a few current-generation Civic Hybrids for around 15k, which is just in our price range, provided we get enough for the Sonata.

The main reason for downsizing is that we have ended up with two mid size cars, when it's not very often that we need to travel with lots of people or stuff. My mother also finds that the B pillar is too wide in the Sonata (I understand it's because of the side airbags), and she sits with the seat in a position where it adds to the pillar blind spot even more.

Hybrids are really effective if you are in the city a lot, as it is near impossible to avoid speeding up and slowing down, which hybrids are excellent at making the most of. But for out in the country, diesels are better when cruising on the highway as they can run very lean.

Leighos 12-15-2010 09:21 PM

Quote:

Originally Posted by tumnasgt (Post 209740)
Hybrids are really effective if you are in the city a lot.

That is a good point, being from a small city and commuting daily out to our local airport, I never really thought about it like that.
I've ventured up Auckland a few times and been stuck in peak traffic :mad:, operating in electric only would be great for that stop/start crawling!

tumnasgt 12-15-2010 09:37 PM

Quote:

Originally Posted by Leighos (Post 209757)
That is a good point, being from a small city and commuting daily out to our local airport, I never really thought about it like that.
I've ventured up Auckland a few times and been stuck in peak traffic :mad:, operating in electric only would be great for that stop/start crawling!

Sadly the Civic Hybrid doesn't have electric only like the Prius, but it still allows you to use some of the energy that otherwise would have been lost to braking. And it switches off the engine at traffic lights, which will reduce the wear on my ignition switch (and my fear of the battery dying in the middle of the road).

A brand new Prius with the <45km/h electric only mode would be fun, because that way I could drive to the local shops and back without having the problem of a cold ICE. But they are way out of the ~15k price bracket.

Maybe when I win the lotto...

Leighos 12-16-2010 08:18 PM

Quote:

Originally Posted by tumnasgt (Post 209759)
Maybe when I win the lotto...

Me too, winning the lotto is the only way I will ever be able to afford a Tesla!

BLSTIC 01-25-2011 08:33 AM

My legacy GT (1st gen wagon) did better than yours... Around 15l/100km around town, 10 on the highway.

Single best 'mod' I did for efficiency was a combination of boost guage and air-fuel ratio meter. Drive at the highest load you can without going into open loop. Normally equates to 0-1 psi below 3000rpm. Scored 40km per tank around town out of that one... Also my boost controller was an adjustable pressure relief valve, i found that open/closed loop depended on throttle and rpm only, not boost pressure. So using my boost controller set to high (not normally considered efficient) it could run up to 4psi (as opposed to 1-2) in closed loop going up hills, more than likely helped being able to run higher boost (and get more power) without using the stupid-rich fue mixtures subaru's are famous for...

Another thing you could try is the parrallel fuel rail mod and get the computer tuned to suit. One of the reasons mose people run them rich is because of the fuel rail setup (two separate rails, with one feed, one relief, and a joiner) creates a pressure differential between the first and last injector in the rail. A sad fact of life with most computers is that you have to tune to suit the worst conditions. So if one cylinder is running lean you have to run the rest rich to make that one ok... And the ignition timing for that cylinder is ideally also different from the rest too (but you can't set it right coz the others will ping). End result is overall richer mixtures and retarded timing without the safety that normally comes with it. Although that is mostly theoretical, subaru's have an alarming tendency to destroy #4 bearings and pistons more than anything other. Manifold design is fine... guess which injector is the last in the line for fuel pressure?

It might sound complicated, but the mod and tuning can be quite simple. Get an aftermarket fuel pressure regulator and a third fuel rail (sides are interchangable, you want to have two rails without the factory regulator). Split the fuel feed line and feed it into both rails, with the regulator after you join the rails together again. This gives you even fuel pressure and a way to adjust your open loop mixures. A potentiometer in the air temp sensor circuit can adjust ignition timing (to a degree, pardon the pun).

Another worthwhile mod may be to fan force your interheater (ok cooler, but you park up after going for a drive, put your hand in the scoop, and tell me that your intercooler is cooling down. Also try tell me that the computer will do something OTHER than add fuel and retard timing to get rid of the pinging when you tromp it. And you can't lie about it...). Again mainly for high loads, but if you enjoy them as much as I did, going faster and using less fuel is a double win.

I measured my intercooler temp after going for a thrash on a cold (6*c) day. Coolant temp in my water-air intercooler was 30*c. Then I fixed the pump and it dropped to 9*c. More power without a fuel consumption hit. Worth a try...

Leighos 01-26-2011 05:09 PM

Thanks for the reply mate.

Thats some good advice for sure.

I have a boost gauge and usually drive just in vacuum and shift below 3000rpm, so you are saying allowing a bit of boost to develop would be more economical? I always thought anything below WOT was in closed loop anyway? Wouldn't an increase in manifold pressure equate to an increase in fuel delivery? Sorry I'm not an expert on this, I don't mean to sound ignorant :)

I have also toyed with the idea of fitting an AF ratio gauge, would it be worth while only using the narrow band factory o2 sensor though? I have a simple LED display gauge, but I figured it wouldn't be telling me anything useful, I'm already well aware that she runs excessively rich haha!
I'd like to run a little leaner when driving economically or cruising (safely leaner, if there is such a thing for a EJ20) but I'm running a factory v3 STi ECU set up (440cc injectors, 90mm AFM and a TD05H 'big' 16g) and that doesn't have a intake air temp input (i don't think?) so I was thinking of modifying the AFM signal, but yea need to do a bit more research before messing around with that.

I've also performed the split rail fuel rail mod when I did my single turbo conversion, but using two right hand rails with the factory FPRs. I still have a pair of left rails so I you think using an adjustable FPR is a worthwhile mod for economy, I just might give that a go.

I totally agree with you about the inter-heater. In fact I have heard many times that Subaru designed the bonnet scoop both to allow cool air in for the intercooler, but also allow hot air out when the car is stationary (like in bumper to bumper traffic in Tokyo!). So it makes sense that the air to air intercooler is going to heat up around town and decrease your overall efficiency. I'd really like to convert mine to water to air someday, I wonder though how the benefits offset against the difference in weight plus load on electrical system to run the pump?

So I take it you don't have Subaru anymore?

BLSTIC 01-26-2011 11:38 PM

No my subaru had an uninsured meeting with an angry mob and bottles. Between that and my multiple spare cars I decided to sell it off.

I would say that the adjustable FPR would only help fuel economy in open loop. If you already have the split rail mod I wouldn't be re-doing it for what amounts to a bit of fun...

As for the air fuel ratio meter, mine was a $25 jaycar 'voltage monitor' on the factory narrow band sensor. It doesn't tell you exact air fuel ratio, but it can tell you when you are in injector over-run (i.e. zero fuel being injected), closed loop, open loop, and the nature of misfires that develop. It responds fast enough to catch individual misfires that you can barely feel as well. Misfires show as a lean condition, by watching the guage you can determine if the misfire was caused by fuel (guage goes lean slowly before misfire) or spark (guage goes full rich to full or off scale lean immediately after misfire).

In normal around town driving getting boost was nigh on impossible in closed loop with my VF10. On the highway was easier though (engine speed changes slowly and boost comes on at lower rpm).

More to follow when I get home from work

pounsfos 01-27-2011 03:35 AM

its good to know im not the only nz'er on here (hi from christchurch)

if your going to get a smaller car then get yourself an old school suzuki alto (65mpg easy peasy) or if you want something abit bigger, holden barina's are good cars and plenty cheap or if you like old "cool" cars then get a corrolla or starlet. the 4afe toyota corrolla's are good on gas to you can get a respectable 40mpg out of them, my friend gets 55mpg out of his but he has had an ecu tune, custom this and that.

if you want to keep the suby then put a smaller turbo on it, less spool time means acceleration off them mark and better fuel economy (as long as you keep the boost below about 5psi) get a ecu tune as well. and if you want make a hot air intake, seriously theres alot you can do

oh and dont forget to read the modifications page and hypermiling tips.

one last thing. dont forget to keep track of your "milage) ask the gas guy for the reciept with the litres on it :)

if you were in chch i'd give you discount on fuel but your not haha (i work at bp)

BLSTIC 01-27-2011 06:37 AM

Oh I'm in dunedin too... And despite being interested in economy I currently drive the most needlessly excessive car I could come across. All I can say is... At least it's not the 5.6L version...

Such a pity that it uses CIS-E... I really don't know how to tune it properly, nor tune it to accept any modifications I may perform...


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