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Discussion Starter #1
Hey i'm new to the forums-
Been looking around for a great car that has good MPG from factory and some mods to make it more efficent, currently i have a saab 93 and its a bit thirsty. but on the highway not that much, 7-8L/100km ( highway) speed 100-120km/h

been looking for a honda especially the old ones because i see that they have real good fuel economy for their age, so im kinda hooked for one.
i know that there are alot of threads about this but doesn't feel like i get a straight answer, im kinda new to hondas.

is there a way on a budget we say for an example 1000 USD to make the D-series more fuel efficent? with out touching the motor that much?
and which D series should i aim for? people say HX for fuel efficeny or CRX but those cars is kinda hard to find here in sweden haven't seen one for sale for a while. so im more intrested for a civic ( IDK if HX CRX is trim levels or not from factory )

the information i've gatherd so far from other threads about this topic is

  • high compression
  • new block / transmission
  • lean burning tune
  • strip the car for lower weight
-vtec stage 3

Hope you guys understand my frustration :)
 

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Brokedick Millionaire
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Transzex will probably comment in this since he’s had experience with hyper miling in a crx
Or maybe not.

Built motor/high compression is not needed. Stock D15B7 is just fine. Add easy bolt on's, no need to remove the head, easy 50+ mpg. Also easy to get 33 whp with just those easy bolt-ons.

D15Beast7, the legend, was copied a few times and the output number were the same 115-118 whp.
 

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Discussion Starter #4
that's very nice to hear that i dont need to touch the motor that much.
but i haven't seen any motor with the D15B7 selling yet on the websites im looking at ( blocket as call in sweden ) aka craiglist ish.

i found a 1.5vtec with D15Z8 one and i guess that has the vtec-e. very intrested of this one because of the vtec-e.
the cars that is listed is a bunch of 1.4L ones. and what kind of bolt on's is there? like hot air intake? cat removal from the manifold incase it has one?
 

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93 Civic Cx hatch
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Getting good mpg is more about the user and how they drive than the actual car when looking at a stock civic. It is really simple to do but not everyone cares enough to develop the skill of it. Don't have a lead foot and shift earlier than you normally would is probably the easiest way to explain it. There is more to it than that though. You can always install one of those mpg vacuum gauges, they help you understand where you are not driving as efficiently as you could be.

I've had countless crxs and civics over the years and always managed to get great mpg in them. No need to do any bolt ons or special things unless you want to. When I buy a new one I just do a tune up on it. Generally that will involve replacing the spark plugs, inspecting and possibly replacing the distributor cap or rotor wheel thing(forget name), changing old filters, etc. Mostly I just check it over and see what it needs and replace that, simple.

I currently have a 93 civic cx with the d15b8 that is the 70hp 8 valve motor. Not the fastest and honestly a little too slow for me.. Although I've been driving it for years and love this car. I drove this thing around Colorado at a mile high elevation in the past which made it even worse lol. I had no problems getting 50 mpg in this car but it comes with some compromises. I had to deal with it struggling going up hills. In the mountains in the rare times I had to go up to an even higher elevation the car was a joke and honestly probably dangerous... Needed to drop down to second gear and it barely pulled up some bigger hills and that was at like 30 mph with other cars whizzing past me. My motor was "strong" and had good compression and all that but 70 hp and 8 valves only goes so far. Just to give you a real world example of issues I've had. Great mpg, but it has its compromises. Car is super reliable though and I've put a ton of miles on it. I would take it anywhere but I've also taken care of it.

Honestly unless you require 50+ mpg for some reason you don't need to look for the super efficient models. You can get good mpg in other civic models as well.
 

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Discussion Starter #6
Yeah i understand the driving part i can do that and i have the skill for it. But it depends on the car also like my saab(2.0t) its thirsty in city its like 13L/100km how efficent i even drive it wont drop. Sometimes i turn the engine off when i wait for red light etc but it doesnt help that much.
I always try to use the cruise control so i dont hassle with the gas all the time.

Thats why i want a 90-110hp civic instead of 70-84hp. Its like u said it feels like it doesnt pull on mountains or inclined roads. I had a similar experience with a skoda 1.6L 102HP
Was going to drive home from work 4 people in the car tried to overtake the trucks ( they drive like 50mph in highway ) but it felt like the motor was very weak i even downshifted to 4th and tried to overtake the trucks and it was in an inclined Road. Was stuck at 65mph it wont even go past it. But hey you have to sacarfise power for mpg i guess..
 

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Where I live currently it is full of huge hills so it is frustrating. My issue with pulling on hills and in the mountains is caused by 2 things. The biggest is that the engine is 8 valves I think and just cannot handle the task, the next is that my transmission is the extra long geared transmission. So the transmission makes it even worse for the motor. I am about to partially fix this issue in the coming months by installing a different head and ecu into my car. This should take me from 70hp up to potentially a little over 120 iirc if I do one of the vtec heads. Quite a huge difference. Even with that change I expect to still be able to maintain close to 40 mpg but I won't know until then.

If I were you I would stick to the dx/ex models. Those are going to have better gearing on the transmission for going quicker as well as higher hp motors. The dx model is somewhere between the ex/si and the cx as far as gearing if my memory serves and is your best bet. They will still be capable of great mpg too. Depending on the year I would expect to get anywhere from 30-40 mpg which is 9.41 - 7.06 L/100km. The older hondas around 89-95 can get some of the best mpg imo because they are usually the lightest but anything 91ish and older probably doesn't have airbags.. So keep that one in mind if it matters to you. Unless where you live is different, in the US they did not come with them until later like 92/93.
 

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Discussion Starter #8
its kinda hard to find older civics here in sweden i belive, or i'm just looking at wrong places, as i said its kinda hard to find the motor i want.

the D15Z8 is still for sale on a civic hatchback from 97. and the D15B7 cant find it anywhere even on the junkyard i cant so its pretty useless to look for one and do a swap. rather spend the money from bought motor and swap to a newer car and maybe have better mpg opportunities. but as i said. what kind of bolt ons is there? to improve the mpg
 

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Generally bolt ons improve your power which will often have the opposite effect and reduce your mpg but it is a complicated thing. The only real "bolt ons" that will have a direct effect on improving mpg will be on the body of your car. You can add things like a cover that goes over your windshield wipers(looks super ugly) that helps the air not be disturbed by them. You can remove the mirrors from your car and get the little inside ones, but check your local laws on that one. You could mod your rims so they cause less drag, usually a flat cover over them. Putting a cover completely over your rear wheels(like the old Prius' used to have) is also really good for mpg. Covering the underside of the car also to reduce drag is a huge help. You can do many of these mods on the cheap with the corrugated plastic sheets but it doesn't look great.

If you want to look into more things you can do to improve your mpg I would check out sites like ecomodder, where the hypermilers hang out. All of the above is really only to get the very last little bit of mpg out of your car. You should be able to hit 40+ just stock, getting much over 50 or even something like 60+ mpg takes a lot of work in most cars. Way beyond the bolt ons, you have to change the entire way you drive. No more cruise control and things that waste gas like that. It can be a big lifestyle change if you hypermile depending on how hard you go at it. Lots of coasting involved.

I still think the best mod is the driver and changing the way they drive. Conserve your momentum, that is the name of the game with mpg. When you approach a hill and give the car more gas, keep the gas steady where you have it. The car will bog a little bit going up the hill and you will for sure slow down. When you reach the top of the hill you gain everything you lost going up it by costing down the hill. Always coast in gear as that should use no fuel. If you coast out of gear then you are still idling. Things like that are essential to getting good mpg imo.
 

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Brokedick Millionaire
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rotary, you've missed the point somewhat. Proper parts that improve power while using the same amount of fuel increase efficiency and therefore MPG. Before Ecomodder was around, I was hypermiling on here and other forums, a bunch of it is the drivers style, but there is also an issue with OBD-1 Honda ECU's that if you keep a steady throttle, the ECU will keep leaning out and correcting back to stoich as needed, no knock sensors involved.

When you approach a hill, you do NOT give the car more gas, you maintain the steady throttle. You will slow going up the hill but holding that pedal position you will gain speed back on the downside.

Having an old "loose" motor that doesn't engine brake well while coasting might help MPG, but tweaking the TPS setting so you can crack open the throttle while coasting, but not engine braking, with the fuel injectors shut off, is key.

My test bed was I-75 between Detroit and Cincy, every 2-3 weeks I was making the trip from D to C on Sunday night with light car traffic, normal truck traffic. Timing the hills and truck passes using the aero effects is key. You need to sling shot past the truck and not stall as you get at their LF wheel. Do that on the downhill side without adding throttle (you'll be speeding!) and give some of it on the uphill side.

Because of this I rarely drafted trucks which can be dangerous. Time your slingshot pass without moving your left foot, it takes discipline.

D15B7, 85 whp stock with 100k miles or so, 102 chp factory rated when new.

Same motor. 100k more mile, simple IHE, Biggest D16A6 Crane Cam there was, ported Z6 intake and TB, minor ECU tuning, Stillen header and 2.25" crush bent exhaust though STOCK OEM cat. converter.

121 whp or 145 chp. 37-38 mpg stock improved to 53 mpg on pure gas, or 48 mpg on E10...with aero mods as well. That damn rear bumper parachute!
 

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I agree you can get more efficient with more power to a point. With my car and having the 70hp at the crank motor in it I struggled in many places where I could have been more efficient if I had more power. Where I would have to downshift to even make it up some hills. I too have driven quite a lot in this car on a fairly regular basis but it has been a little over a year now since I've seen my car. Getting it back soon though.

I didn't draft trucks either because my car didn't like going much over 65 or so and I found some of my best mpg at around 60/65 anyway so it worked. There doesn't seem to be a lot of go left in the 8 valve motor at that speed but my car doesn't even have a tach stock so I can never be positive of my exact rpm. I still don't like dropping gears and basically redlining it to pass someone at that speed. The highway I used to drive was pretty flat so not really any downhill passing opportunities there but I can see that working in other places. These are reasons why I really want to get up to even around 90hp with the 16v head or whatever it gets you. I think it would help the car a lot.

When you approach a hill, you do NOT give the car more gas, you maintain the steady throttle. You will slow going up the hill but holding that pedal position you will gain speed back on the downside.
That part was a mistype by me, what you said is what I meant as you can see by the rest of the sentence where I also said to keep it steady and then the rest of what you said.
 

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Read up on hypermiling techniques, using cruise wastes fuel. Another avenue would be a large turbo that would enable the motor to run in a near zero pressure state without adding much fuel.

Some people have hit 60+ mpg while making nearly 200hp on boost. Key to that is sizing the turbo so you really gotta TRY to spool it.

I dont see why that wouldnt work well w your locally common smaller engine either. Itd run w more tq on basically the same fuel and have good power when you werent demanding efficiency.

Itd easily challenge the stated budget but if you saved 400$ buying a more common variant youd be close to there if china no brand turbos are ok in your mind.

I really only spent money on injectors and am under 800$ on my kit but i already had a wb02 sensor installed and a socketed/chipped ecu.

All that said my wifes bone stock 92 4 door gets 40-42 mpg loaded through a mountain pass. Only mods are a b000 ex transmission and a cold air intake. Its a great setup.
 

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Discussion Starter #13
How come cruise waste more fuel? I've read somewhere and heard from people that it saves more fuel in road trips because the computer adjust the air fuel ratio in longer steady trips or am i just wrong?
 

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In our cars anyways, cruise control's only goal is to maintain set road speed, whatever that might entail.

Typically there isnt much processing being done to also consider AFRs or load when using cruise. The government said Engine ECU operates the engine and is in control of fuel economy and emissions. There was never a requirement that said other devices that could take over the controls that a driver already uses must be part of overall fuel economy and emissions regulations. So cruise on our cars isn't part of fuel management or emissions regulations, meaning there was no incentive to have to provide additional cruise operation MPG.

Cruise control ECUs job is simply to hold set cruise speed. It is the Engine ECUs job to manipulate AFRs and other parameters based on current driver demands and inputs. This is why the cruise control system in our cars physically operates the accelerator pedal, to emulate a dumb ass driver.

That being said, it also doesn't have the foresight to anticipate hills or other changes that might affect upcoming loads, therefore it can't come up with a plan of attack to keep fuel usage at a minimum.

The cruise program only senses "hey, speed is dropping/increasing, accelerate/decelerate slowly until speed begins to increase/decrease then maintain throttle position when set cruise speed is met".

Almost all cars older than 2004 operated cruise like this, not really giving too much consideration to MPG since the responsibility of handling MPG falls on the Engine ECU, and has always traditionally been based on driver inputs, nothing else. Cruise control ECUs in our cars physically operates the throttle pedal, to emulate a driver, nothing else. If the car was an automatic, it 'might' unlock the torque converter a bit earlier if cruise was set where it began to notice speed decreasing faster than usual in anticipation for a hill to bump the torque input a bit to the transmission and get revs up a tiny bit more into the powerband, but that's about it honestly. The transmission control program in our cars ECU is still dependent on engine sensors and throttle position to know how to shift gears based on driver load demands, hence why the cruise actuator operates the throttle pedal.

Cruise control in our cars with an automatic is nothing more than a stand in idiot driver who doesn't anticipate accelerating their car before a hill. If it's a manual, it's even worse. It primary job is to maintain road speed if it can, nothing else.

Newer cars post 2004 began to implement more dynamic situational awareness. This required a larger suite of feedback systems and sensors necessary to support such a cruise control program, but were still not yet implemented across a wide range of cars.

Come to today, cruise control in a modern feature loaded car is incredible. They have forward looking cameras and forward looking radar. Typically these are used for ABS and collision avoidance systems, but cruise can also use them if programmed to follow cars in front (adaptive cruise control), or better anticipate an upcoming hill.

The latest and greatest cruise control implementation currently being headed up by Daimler corporation have manually created mappings of our highways to map where hills start and end in our highway systems. Since these plot maps are constantly being updated by them for new roads, kind of like Google does for Google Earth, the OEM will push over the air updates to continually update the cruise map pack in each car that has this feature. The cruise control system will use the car navigation system GPS data to determine where it is, then correlate to the map packs to KNOW where hills are, providing the ability to know when to begin to accelerate and decelerate, coupled with the forward looking radar and cameras to know if it is appropriate to do so (like in case there is a car in front or something).

Automation is coming, I think cars are up to SAE level 3, boundary level 4 in automation at this time (because of some of Tesla's stuff). Tractor trailers are up to SAE level 2 currently. Google 'SAE automation timeline' for more info about this!
 

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I would say that even modern cruise doesn't have the situational awareness to be more fuel efficient than a human. Adaptive cruise doesn't reliably look past the car in front for example, and can't anticipate driver behavior like a human.

And i can't remember ever hearing that setting the cruise shifts the car into a different fueling condition.
 

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I would say that even modern cruise doesn't have the situational awareness to be more fuel efficient than a human. Adaptive cruise doesn't reliably look past the car in front for example, and can't anticipate driver behavior like a human.

And i can't remember ever hearing that setting the cruise shifts the car into a different fueling condition.
Your right, it's definitely not as good as it could be, due to current radar and camera limitations. This is why Daimler is manually creating maps of our highways to plot the terrain, and they are also leveraging data from the Army Corps of Engineers to make these kinds of mappings a reality. There are very big fuel economy gains to be had in the HD industry by a technology such as this, so there is a big push to widen the implementation. It currently exists on the latest Freightliner New Cascadia over the road trucks.

But Mahle is saying they will have 500 meter range LIDAR units ready around 2025 for under $1000 a piece. If this is the case, I suspect around that time software engineers will have the inputs and resolution they need to make cruise control load anticipation a reality.

It is an interesting time to be alive! Something new all the time.
 
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