Stonage07

Sup Folks! I have been having this problem ever since I got the car honestly, but it never stood out to be that much because I hadnt driven anything with a working damn fuel guage before <lol>.. Now with work related driving, it has became damn obvious that it uses a bit too much damn fuel for a 1.5 liter Economic block, it average's out to be around 28 MPG, when sometime more city driving will force it down to 25-26'ish.. And I tell you, that is with careful and {too} slow driving! I did do some testing over the last few months, tanking the same fuel everytime, full tank, with driving in ECONO mode vs just driving without even paying attention, with the occasional pulls.. Both came at out 520 KMs funnily...

The engine, which is a D15Z6, I think the american equivalent would be the D15Z1? Anyhow, it has 110k Miles on the block. It is a healthy engine, well taken care off as far as I know, it'll only smoke some condense during cold start, when warm there is zero smoke.. I feel like these engines should atleast be capable of reaching atleast 35 to 40mpg, A gsr is more fuel efficient then my little 1.5 LoL

I cannot comprehend why a rather fresh block would drop so much MPG? I've read about ppl going damn near 45 mpg with the d15z1 block

TIA!



Ahh edit:... Its a EK chassis and tthe tire size is 205/40 R17's, i know it affects the reading but positively or negatively..

DumpdEJ6

Wheels will make a difference, heavier 17" wheels like you have will cut your MPG down some, but not as drastically as what you are saying. Also tire compound will play a role, stickier tires have more rolling resistance. How long has it been since you did a tune up? (air filter, plugs, distributor cap and rotor) Could be slightly sticking brakes, could be alignment issues, could be incorrect ignition timing, there are a ton of factors in play and if they are all just a little bit off, it adds up.

Stonage07

Yea man, that is the bummer.. So many damn factors come into play, but it could be the O2 sensor, as I read on this subject, but then again I aint sure...I feel like all these things could only benefit in a little increase.. But to clear it out, Brakes are fine, alignment isn't 100% but it has no unusual tire wear {Will be addressed after I have a new coilover set put on}

Could it be related to the Economic Mode for these engines, that there is something not correct relating that? It feels not to benefit me in any way when keeping my eye on it, nor does it seem to be as responsive as i'd thought {The light that comes on in the dashboard}

Stonage07

I've been looking up what possible causes could be for such a big MPG drop... This engine is advertised at 49MPG when it first came out. I have the original piece of paper telling me everything about the engine. So thats even worse then I thought lmao

Checked out the Pollen Filter, not too dirty by any means.

I was thinking to clean out EGR on the intake still, and the MAF sensor.. But what else!!! Was hoping to atleast have a semi-economic car till I swap it out for a bigger engine :/

What could be the main causes for such MPG drops on a healthy engine?

Stonage07

I would like to mention that the exhaust does have slight popping noises when it is idling, slight mis or backfiring.... Also rarely will it when starting it seem to die out the first couple seconds until I give it gas, where it will run at normal idle rpm

Stonage07

Anyone? I'd love some tips on where to start without prioritizing dishing out 100s of $$!! This is only a temporary block aswell, as im saving towards a b18

DumpdEJ6

Have you done a compression test to be sure that it is a healthy engine? You never mentioned whether you had done a tune up recently, if the spark plugs and distributor cap and rotor are old and worn, that can make a big difference.

TomCat39

Also, have you verified what manual transmission is mated to the car? If it's a performance SI big bearing transmission, you won't get anywhere near the fuel efficiency.

Also, dirty injectors will cause a bad spray pattern and impact fuel economy as well as bad burn of the fuel and even restrict fuel.

A weak fuel pump could be providing less then optimal pressure.

Do you have the 5 wire O2 primary sensor? If you only have the 4 wires then you have the equivalent of the California D15Z1 engine which gets half the fuel economy as it doesn't have the same lean burn capability due to no wideband o2 sensor.

These are the first things that come to mind that may be an issue on a vtec-e motor.

Stonage07

It is definetly the LS gearbox, it managed to pull to 190 in 4th with some room left.. Believe it was the s20 gearbox. But I did just check the o2 sensor and it is definetly a 1 wire sensor lmao like wat da ***... The upstream o2 sensor we're talking now right?

I dont even know how to begin working on this issue not having any knowledge regarding wiring and all that jazz... Shouldnt this motor have came with a 4-5 wire o2 sensor atleast? Since its vtec-e lol




@DumpdEJ6, I havent had the compression tested, it feels healthy, it sounds healthy. It just slurps a lot of gasoline thru a XXL straw... But i bought the car like this, so a tune-up will be due in some time

TheShodan

iTrader: (14)

You need to just attack these things with fresh items, as mentioned. There's not going to be ONE thing that cleans it all up.
-Compression/leakdown
-Fresh plugs / wires / distributor cap/ ignition rotor
-o2 Sensor may or may not need changing if not throwing an official code
-Catalyzer? Makes a difference
-Fuel injector cleaning / replace fuel filter if possible.


Nothing to it.... But to do it....

Stonage07

Yea true mate, btw salute to you. Bought a turbocharger from you a couple years back via Greg @ Autoworks :}

But, yeah meh.. There is no CEL atleast and for the o2 sensor could it really be worth it seeing its just one wire instead of the 4 or 5 they should come with to have this great MPG? I dont understand how these engines come from factory claiming they can reach 21kms to a liter, apparently with a one wire o2 sensor while my does not even half that..

@Theshodan, are these engines able to get like 40+ mpg with the 1 wire o2 sensor they came with from the factory if the owner's manual does state it should be getting 45+?
Or is there more to it and that only certain d15z6's or whatever came with the 5 wired o2 sensor?

TheShodan

iTrader: (14)

The 02 Sensor that they get from the factory is certainly capable of over 40mpg, but you're really not taking into account a lot of factors that contribute whether or not you actually get 45+mpg. It doesn't matter whether it's a 1 wire sensor or 5 wired sensor. They all work within the OEM specifications and give the same voltage signal, so, it doesn't matter as long as it's working well, and giving the right voltages.

1) MPG estimates. Please remember that the way they gauge these range/mileage estimates is based upon certain calculations that today are not regarded as "precise" as they once were. This wasn't something that Honda did on purpose like the VW scandal or used as a method to directly help with increased sales, but they did use that range as a possible optimal goal that the engine could be able to achieve. The difference now, is that based upon newer calculation, you might get close to their proclaimed MPG estimates, but they make that calculation based upon the fact that the engine was new over 21 years ago. To expect that kind of precision in MPG estimates, is setting yourself up for a standard the car just won't not live up to.

2) Age of the car. Remember, this engine is at least 16 to 21 years of age, in stock form. As much as Honda had over engineered their products in the Golden Era of its popularity, you can't expect one 02 Sensor and a couple of parts to make it back to being brand new again. Only with a complete rebuild of the engine with all specifications (Including new oil sealing and compression rings, new bearings, pumps, etc) could you expect the 40mpg to 45mpg that you're trying to achieve. What we're trying to help you solve is to make sure that the car can get much better gas mileage relative to the current models out there, coming close to what the factory had. That's going to be more than just worrying about which 02 Denso sensor that Honda used then.

3) Sum of its Parts - There's not going to be one particular part that will be responsible for you for getting the optimal fuel mileage that you're looking for. We're all trying to help you get the concept of using the right components to get the car to perform in a much better situation than it currently does. That doesn't mean that you're automatically going to get the car to have high-MPG just from replacing a few parts, but getting the right parts will help you get closer to your goal. Look at Point #2 regarding the age of the car, and think realistically as to what this car may gain. Parts like new distributor rotor, leads (spark plug wires), plugs, radiator and hose flushes, air filter, cleaned IACV motor, and other steps (assuming engine compression is within specifications) will all help in getting your MPG higher, and the car run smoothly. This also means running the right OEM wheel sizes and getting all of the proper plastic underbelly shields to help with better aerodynamics for MPG

I'm not even going to get into aftermarket parts, like supreme Aero packages on the car, or moon-style wheel covers, to squeeze every drop of fuel out of the car. It's just not realistic.

4) The Human condition -. These MPG estimates only come even close to reality when the human driving the car constantly and consistently drives conservatively , and understands when to shift the gears to get optimal fuel economy (the automatics really suck at this), and when the car should basically be coasting down a hill in neutral. Again, these figures you're going for are with optimal conditions at all times. Meaning, there's no practical way for you to get these 45mpg+ averages unless you have the engine rebuilt and drive with every bit of respect for getting high fuel mileage. That's hard to do, if not impossible.

So, I think that at least changing the O2 sensor will help the car overall to run much better than without it, (and it won't matter which "wire version" you get,) but just like every other part that we're stating you need to change, it will get you further to your goal. But please, don't blame the car, nor yourself if you don't reach the 41+mpg. If you want to do that, get a VW TDI running on diesel, and you'll get closer to that goal more consistently.

I hope this helps you at least get the car running in better order.

DumpdEJ6

The fact is that the OP still hasn't (or at least hasn't told us) that he checked the compression, nor inspected/replaced plugs and distributor cap/rotor: all things that are likely to have just as much, if not MORE influence on gas mileage than the O2 sensor. THESE ARE THINGS THAT NEED TO BE DONE. OP: Stop focusing on the O2 sensor and get the easy/cheap stuff done first. A compression test is easy to do and since you have to remove the spark plugs in order to do it, just replace them with some NGK v-powers while you're at it. Tell us the compression numbers, get a new cap and rotor, fill up, drive...then fill up again and get back to us.

Talking about it isn't doing anything to help your car.

Stonage07

Shodan thanks for being so clear n formal mate, I understand your points! I'm not aiming to get top fuel economy just would be nice to have a little higher MPG with this car for the time being and the power output since its nothing crazy, guess the O2 sensor will be due next then. Maybe thermostate if i can diagnose it faulty since it does take a long time to warm up. But those are long shots, we'll see!!! I'll definetly get to work with it after the usual bills and report back with hopefully some guud worthwhile news =P

Stonage07

DumpdEJ6, the thing is. It's not so simple to get the compression tested. I dont have a connect or know a reputable garage that doesnt charge crazy amounts to get the compression sorted out, it sounds more for the long term longevity of the engine aswell, but i've been busy working mate, but all money has re-located into monthly bills haha so in a weeks time I can get to some working which will be a tune-up, inspect the plugs to see how it runs

I was thinking though, these NGK V power plugs are they worthwhile in comparison to the normal NGK spark plugs? on a stock engine d15z with just CAI MPG wise, power i could care less since it isnt all that impressive. I'll get to some real acceleration after i've saved up some money to get a b18c / b18b swap hihi

DumpdEJ6

G-power, V-power, doesn't really matter, just get NGK plugs. You can buy the tool for compression testing, it's probably less than $30. Compression testing a car is as easy as changing spark plugs, and it's essential for determining the actual health of the motor.