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.