D16y5 Turbo or D15Z1?
 

Searched everywhere and I have certainly learned a lot. Sadly...no conclusions though...

I'm looking to get a Honda Civic VX with a D15V1. However, I have heard that this car is painfully slow. For my job I am driving back and forth across town getting off and on the interstate, interchanges, aggressive merging, etc. Given that I'm driving all day for work I want great MPG. However, my fear is that a stock D15V1 will struggle with aggressive interstate driving (perhaps even causing a reduction in mpg).

Modifications won't add much HP unless we are talking about a turbo. Weak rods and small valves in d15z1 make me doubt the increase of power in a turbo.

I hate to get something other than a D15V1 motor, but if I have to... Considering a JDM D15B 3-stage 92-95, but I think I'll have better luck curing cancer than finding one. A much more realistic find would be a D16y5.

Best estimation mpg I have with a D16y5 in a Honda Civic VX/CX is 36 combined (calculated by using data from Fueleconomy.gov and weight difference calculator). Obviously 36 mpg combined is good, but its almost 10 mpg less than the D15V1 motor. Even with my aggressive driving I think the D15V1 would get better than 36 mpg combined...

Lastly, people claimed that putting a turbo on a D16y5 at a low psi (0-5) would help MPG. I've seen claims ranging from 25 mpg (worse than stock) all the way to 64 mpg... Obviously proper tuning and driving characteristics playing a big role.

SO........ what should I do? Again this is a daily driver for MPG. Unfortunately, I'm not delivering newspapers in a suburb; I'm on and off freeway/highway/interstate/interchanges (very hectic).

I think a lot of people here will tell you not to mess up a perfectly good vx by adding a turbo. Maybe it would be wise to pick a different civic to start with. I believe from what I have read cx's have the same or about the same gear ratio as a vx. Then you could add a turbo engine to that car.

As for my personal opinion you dont need a lot of power to deal with agressive/ congested traffic. I use to drive my 1988 nissan sentra hatchback with only 70 hp on the freeway at 75mph without any issues.

I beleive you need to work on "adjusting the nut behind the wheel" first. This tatic is the single most important change for improved FE.

Welcome to the site. What are you driving now?

The VX might be slow compared to some cars, but its really not painfully slow. 0-60 times are around 9 seconds according to google. Thats pretty run of the mill for any smaller car without a sporty engine. If you know how to use it, it should never be a problem IMO. Best bet would probably be to find one and test drive it if you're really THAT concerned.

Sounds like a tough driving environment. And jumping off/on the freeway is not the ideal scenario for the VX, with its tall gearing and lean burn qualities. It's ideal as a cruiser. I have heard too that a properly tuned turbo that delivers its boost at a low rpm range (1700-2200 rpms) can benefit FE. Ford's ecoboost engines do exactly that.

But the single best thing you'll do for your FE is adapt your driving style with instrument guided precision. Get an OBD2 car (not the VX) and buy an Ultra Gauge to monitor engine sensors and drive in the optimal throttle/load positions.

Good luck!

Eh, I don't think I've ever seen any solid evidence of a turbo improving mileage unless the engine is downsized, and that is exactly what Ford is doing with their ecoboost engines. Slap a turbo on any ol engine and you're going to use more fuel.

True. Good point.

To make another point against turbo charging for fuel economey there is evidence that it doesn't work well. If you look at fuelly, the real world gas milage for ecoboost motors in general aren't that much better. These same "more efficent motors" get about the same FE as their larger NA versions because people can't stay out of the boost and therefore don't see the benefits of the smaller displacement.

I still think the vx has plenty of power for a car of its size. No need to mess with the car, its all about learning to drive to make use of the power it has. We all know that the driver makes the biggest difference in FE no matter the car. The same could be said for the ability to deal with traffic.

What are you currently driving? You could probably save yourself a lot of time and money if you just change your driving habits and very little modification if you are only trying to achieve 36mpg combined. Trying to add a turbo will only decrease FE, add HP and cost you a lot of money. You will never earn your money back from the upfront investment.

I currently drive a 2000 Mazda Protege. Its pretty slow on the interstate and with all the crazy merging. Of course this doesn't mean much because its not in the best shape.

Well basically I used this: wallaceracing.com/et-hp-mph.php. It seemed accurate enough for me. According to the specs on the 92 HP d15v1 I'm going to be getting around slower than my Mazda protege. In fact, I'd have to find a way to cut weight and boost HP to about 105 before it would be better than my mazda. I've considered doing this....

California98Civic hit the nail on the head IMO. Its a tough driving environment and I don't believe the d15v1 was designed for my "on-off-crazy-interstate-maze". I really do wish I could use the proper driving techniques to boost mpg. Unfortunately, the environment won't allow for it, nor will my crazy schedule (often in a rush).

Certainly sounds like a turbo on a d15z1 is out. Maybe I should try and track down a stage 3? Can I put a 96-00 stage 3 in a VX or CX? I seriously doubt I'll find a 92-95 stage 3. No love for the y5? Anyone with experiences driving this?

People here have seen as high as 58mpg (link) from a Mazda Protege. Achieving the numbers you are talking about should be fairly easy in your current vehicle. Not to be rude, but I don't believe the car is the issue here. You might want to read up on some hypermiling tips (link) which will definitely help you to improve, maybe even do some minor modifications which will make it that much easier to achieve higher numbers.

What is your mpg goal?
How fast do you drive?
What psi are you running in your tires?

You should check the 65+ Efficiency Mods section (link) to see some of the little things you can do to improve your mileage.

What kind of mileage are you wanting/expecting? Mid 30's may be all you'll get if you have to be aggressive. Maybe a larger 1.7 or 1.8 with a taller set of gears is what you're looking at. Power goes up as far as you can afford...

I don't have to be constantly aggressive. And after seeing people with turbos and low psi getting 64mpg, I definitely think my goals are possible:

City: 40 MPG*
Highway: 50 MPG*

*With occasional bad driving due to the nature of my travels...

Would you mind sharing where you have gathered this information?

There are plenty of people who have already ruined perfectly good civic VX's with engine swaps, so if you really want to go that route you might find exactly what you are looking for.
The difference between a VX and a CX once you pull the engine out for an engine swap is the VX has more wiring for the lean burn and the v-tec, if you are going to go with a 3 stage v-tec you are going to have to hack up the wiring anyway and you are not going to use the lean burn part of the wiring and you are going to pull the engine that the car was designed to use and that people get 50-60mpg with stock.

There are plenty of civics with engine swaps but finding one that is stock is rare.

It almost sounds like you need a motorcycle.

Russell would be my source: d-series.org/forums/forced-induction/117099-i-did-some-fe-testing-64-8mpg dot html.

However, other people have done it, but not up to 64mpg. I see a lot of mid 40's though.

Not looking to destroy a beautiful VX. I have respect for this car: honda-tech.com/showthread.php?t=1535304&highlight=turbo

From what I have been reading the 64 mpg turbo y5 is tempting, but most are unsuccessful and end up with a butchered VX getting 35 mpg combined. However, lots of engine swaps with the y5 are successful, yielding more power, but less mpg. Alternatively, I could just stick with a stock z1 and do very minor mods to increase power (very minor). One mod that comes to mind would be a 2.25 inch piping catback exhaust. I would get better mpg and more power since the motor would be able to exhale at full capacity (emissions standards are non-existent in my city).

So.... either boost the power of a z1 or boost the mpg of a y5. Which would be easier?

From the thread at the forum, the guy is running a crazy set-up that enables him to do some very ultra-lean burn, using special plugs, cams and a fully programmable EFI.

You're not going to get that within a budget, not the kind of budget you'd throw at a daily beater... and in that state of tune, I doubt it'd pass NOx regulations.

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Work on your current car. If you have the 2.0 with the manual, you can swap out fifth for an old 626 gear for some extra reach, and get taller tires. You can even chip it for more power and extra lean burn, if the idea of a special map to enable ultra-lean cruising is enticing, this is possible. The 2.0 is very resistant to detonation.

I agree with the "russell setup", almost anything is possible if you throw money at it (55 mpg fiero comes to mind). I'm definitely leaning towards a z1 and just trying to boost the power with a few very basic (and cheap) mods. I'll also try and cut weight where I can.

The y5 is not out of my mind yet though..it is very enticing given the 115 hp and the fact that the valves are much larger. I think there would be some serious mpg gain from a new intake and full exhaust (probably more power too).

I did some FE testing 64.8mpg - D-series.org

Seems to be a lot more leget than some of the others I have seen out there, mainly because this guy gives actual detals of his setup.

Cutting weight will improve your mpg slightly but you would have to cut a lot of weight in order to see any noticeable changes in the environment you drive in. Weight reduction is far more effective in city driving, while aerodynamics play the largest role on the highway.

rrsussel aka dturbosol here on ecomodder, has did a lot more than work on his engine. He incorporated changing his driving habits, aerodynamic and other modifications.

"Try to run high IAT temps. I use a grill block"
"Run your tire pressure at 55psi to 60psi"
"Run with your windows up"
"If you do have AC turn it off"
lowered 2"

Here is his post on ecomodder of his build (link). This one is only 6 pages :)

I read in one of these posts that his goal was to keep it under $6,000 invested. With that much invested to make 64.8mpg, it will only take ummmm 117,108 miles (8 years to the average driver) to make his money back. Only after that will he begin saving money on gas. He has done an amazing job on that car and is getting great gas mileage, but in the end the upfront investment just isn't worth it

I used to have a 95 Civic CX with a D16A6 swap. It made 100 whp with an intake and exhaust and was plenty fast. I got 40 mpg all day long driving like an idiot.

I have seen that link before. But thanks for the reminder! That car's owner established an ecomodder fuel log at one point: 1993 honda del sol s Gas Mileage (dturbosol) - EcoModder.com. And in a couple log entries he reported about 70mpg across full tanks with average speeds of 55mph and 58 mph (during summer). But he did really extensive and complex engine mods, it seems, including designing his own lean burn "prechamber".

Check out his first fuel use gauging method: I did some FE testing 64.8mpg - Page 5 - D-series.org

Here is the fuel map he discusses, in post 50. The highlighted blue is the lean burn zone:

http://i147.photobucket.com/albums/r...nebreetune.jpg
I did some FE testing 64.8mpg - Page 3 - D-series.org

And here's a pic of some aeromods he reports in post #63, reporting over 70mpg:

http://i147.photobucket.com/albums/r...ideaeromod.jpg

In post #71 he promotes ecomodder, as he suggests he wants to build a kamm back. In a later post he seeks a CX transmission from a guy.

Here he is designing and prototyping a huge boattail:
http://i147.photobucket.com/albums/r...mockuprear.jpg

Quite an amazing thread. Skills and motivation like few have. Amazing.

The Z1 engine and o2 sensor do not handle over sized exhaust or exhaust leaks without burning out the $300 o2 sensor within a few months, if you get a new o2 sensor you need to fix the exhaust to stock or you've just wasted money.

Shouldn't be a problem as long as I don't go too far beyond 2 inches. People have gone all the way up to 2.5. I'm just going to 2.25 inches.

Is your Mazda a manual or automatic? If it's automatic, ditch it.

If it's manual, you could...

-work on your driving habits
-start aggressively aero-modding it for the freeway
-get some used lightweight wheels and remove the rear seats
-build a kammback or boat tail
-buy the VX and trade me for my DX D16 which has plenty of power and 40+mpg highway

But I do recommend that you get some coroplast and do a grille block, wheel covers, rear skirts and a passenger mirror delete immediately (air dam if you feel like throwing $20 at it). Combine that with improving your driving technique and you might be surprised at what you get.

The first tank out of my '92 Ford Probe (with the Mazda 2.2L rated at EPA 21/28mpg) was 38mpg. Nothing special other than some aero work and hypermiling. The car later got a 40-inch boat tail and achieved 41mpg over 400 miles just driving a steady 60 mph.

Your car's EPA figures are comparable to my old Probe, so you can definitely average 40mpg if you try.

1.75" exhaust was enough to burn out 2 of the 5 wire o2 sensors on my old civic vx and both my brother and I had the 5 wire o2 sensors burn out on our current vx's from exhaust leaks, it's a common pattern with people who have 5 wire o2 sensor problems to have them burn out after an exhaust leak or switching to a non stock exhaust.

but if you like buying exhaust systems that haven't been proven to increase mileage but that do have a pattern of killing expensive sensors, then go for it.

The stock engine on the VX has some weird sensitivities and it works great in stock form.

Not to discount all the other advice but with the modest goals and performance desired, skip the highway cruiser models (cx-vx) and go straight to the common-man DX. I had a DX take me from NH to FL and back with NO hypermiling or mods @ 35mpg. A stock DX should be close to your goals and a few mods will get you closer for far less money than a VX + turbo.

Swap in the VX 5th gear and adjust the driver, should exceed the goals stated.

The fifth and sixth gen d-series DX, VX, CX, and possibly other trim level trannys all had the 0.702 fifth gear. It was the final drive that made the big difference in fwy cruising rpms. Swap the CX/VX final drive into a DX and you get very similar gearing (not the same, but similarly tall).

But I think hamsterpower has a good point too.

Happy father's day to all who might be celebrating right now...

Thanks Guys for the kind words.

That car was a major learning experience for me. It was kinda of a love/hate adventure. It was fun in that it was a success but it came with a ton of broken parts and labor hours and lots of $$$. In the end I sold it for a nice new house. So I can't complain to much.

My advice would be on a budget, is to get a nice fuel efficient platform to start with. Then work on the aero. Its by far the most bang for your $$$ that you can do. Plus of course the driving techniques is number one.

dude get this. i ran my d16y5 civic hx with a little turbo back in high school with an open down pipe. like 4 inches of exhaust just dumping in my engine bay. at first i ran 310cc RC injectors but it wasnt running to nice. and i didnt tune it. i was just running an FMU to manage the fuel. so i went 240cc integra gsr injectors. it ran better and got a little better gas milage. if i remember correctly i was getting like 320-340 to the tank. i got like 400-440 before (before i was a real hypermiler) so i was averaging about maybe 28-34 mpg in my un tuned turbo set up driving the piss out of it. it was quick to. kept up with some v8's. impressed the chicks. but i eventually took it back apart. 40k miles later running stock (with my engine killing dad driving it) the bottom end of my engine kind of totally died. probably because it leaked a quart of oil every 100 miles and it was running lean as hell. but if it wasnt done by an idiot high schooler it probably could have turned out pretty sweet. just needs to be tuned properly.

oh and another thing. my primary o2 sensor. even though it was treated like crap for like 160k miles and is currently 270k old is just now showing signs of failure.