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-   -   Realize the full Performance/Economy Potential of a Honda Civic VX (https://www.fuelly.com/forums/f9/realize-the-full-performance-economy-potential-of-a-honda-civic-vx-8019.html)

suspendedhatch 04-12-2008 01:52 PM

Realize the full Performance/Economy Potential of a Honda Civic VX
Topic Index
Page 1
Introduction, Goals
Distributor-less Ignition, Waste Spark
Engine Swap
Balanced / Blueprinted Injectors
Initial Dyno Tune
Recommended Reading (Tuning)
LSD Transmission
Weight Reductions / Additions
Gassavers Myths
Planned Mods
Other Mods
Advantages of Direct Fire Ignition
CDI Module

Page 2
D16Y5 and D16Y8 DFCO specs (grasshopper)
Dyno Graph
Distributor-less Conversion
Salt Lake to Albuquerque trip photos

Page 3
Things I'm Doing that Don't Help FE
O2 Target Table
O2 Target Table with Driving Conditions superimposed on it

Page 4
AEM EMS VTEC and VTEC-E Controls
Interpolation and Resolution
Smog Test
Integra DA Wish List
Injector Phase Tuning Benefits
Ignition Timing
Tuning Part Throttle Ignition Timing
Ignition vs Idle Target
P2J ECU VTEC and VTEC-E Pinouts / Wire Colors (grasshopper)

Page 5
Honda Civic Alignment / Tire Wear
Low Temp Thermostat
Updated Pics
Wish List
Injector Phase Tuning
Spoiler Fix
D15Z7 Helms Manual (spanish)
Ignition Timing
D15Z7 OEM specs!!!
D15Z7 5 Speed Gear Ratios
D15Z7 Cam Lobe Height
Valve Relief

Page 6
Valve Adjustment
Winter Tire Choice
Tire Size for HX Rims on a 5th gen Civic
HX Rims, Integra Brakes


Having owned several Hondas and never been fully satisfied, I decided to rethink exactly what my ideal car would be. What I came up with is that I want a car that has great handling, great braking, great power, and great economy. Essentially I want better performance than a Civic Si and better FE than a Civic VX (these being the only vehicles I could afford that have double wishbone suspension front and rear and an exceptionally low coefficient of drag matched to an economical motor). It seems like a pipe dream. But it just so happens that Honda had the same idea.


From 1996-1999 Honda produced a motor that combined VTEC-E and VTEC into one. They didn't bring this motor to the United States. In Japan the block was stamped D15B. Across the rest of the eastern hemisphere, the block was stamped D15Z7.


So last August I sold my Civic DX automatic that had a SOHC VTEC swap and bought a lowly Civic VX. I decided that I needed a chassis change because I wanted a manual transmission and I wanted many things that are only found on the VX, ie the rear diffuser, front lip spoiler (also found on Si), aluminum lower alternator mount, aluminum front lower driver's side engine mount, less sound deadening weight, "VTEC-E" valve cover, and lightweight alloy rims.


First thing I did was lock the car in the garage until I could install some serious car alarm security. It is a Honda afterall. "Honda" is synonymous with "stolen".

Then I did some maintenance on the motor and drove it that way for several months to give me a good baseline. My FE goal would be based on my own personal driving habits and my goal is to exceed this baseline w/out any sneaky tricks like driving like a near-sighted grandmother. My baseline avg was 38 mpg mixed, 44 highway.

The Rules
Which brings me to "the rules". To the general public, the car must outwardly appear to be stock; in other words, it's going to be a sleeper. I don't want to draw any attention from thieves, street racers, cops, or ricers.

Secondly, the car must outperform both the VX and the Si.

Third is not so much a rule as a constraint. My salary requires a very limited budget with long periods of time between expenditures.


So luckily, I already had the AEM EMS. "WHAT?! You have an EMS? Don't those go for thousands of dollars and require hundreds of dollars to have professionally installed and tuned?" Yes and yes. But I got one for $1100 in 2001 (at-cost to help with development), and I have a friend that is a professional tuner. It's a good thing too, because there is no other viable option available for me to realize my goal. Hondata simply isn't capable.


AEM Gauge-Type Wideband O2
The next piece of equipment that I would need so that I could run lean mixtures is the AEM Gauge Type UEGO Controller. $260 ouch. But it's cheaper than competing products and far superior.


suspendedhatch 04-12-2008 04:13 PM

Distributor-less Ignition

The AEM EMS allowed me to convert to distributor-less ignition. This allows much more precise control of the ignition timing. Four small coils are more efficient than one large coil because they have more time to charge before they fire (aka dwell). The AEM Twin Fire CDI Ignition module doubles the voltage and amperage of the ignition system. I bought some used Honda CBR coil-on-plugs (this was before AEM came out with the pencil coils) and a used MSD DIS-4. The DIS-4 was bad so I worked out a rent-to-own deal with my homeboy Scottie for his AEM Twin Fire since he blew up his race car anyway. Here is my write-up of the install: Coil -On-Plug Conversion

Note that you can see the distributor in the picture. At the moment I can't afford a AEM EPM ("engine position module"). On a Honda, the cam and crank sensors are typically found inside the distributor. This is the reason why Honda distributors are so unreliable. The distributor also plugs a hole in the valve cover. The EPM replaces the distributor completely. It plugs the hole and provides a replacement hall-effect sensor to replace the weak factory cam sensor. The stronger AEM sensor is accurate into very high RPMs while the factory sensor tends to "wander" even within the factory redline and is vulnerable to ignition "noise".

Waste Spark
I wired the coils and configured the EMS for waste spark. Waste spark means that in addition to firing the coil at the correct time, you also fire it on the exhaust stroke. In theory this might reduce emissions, but I remain skeptical until I can see the results with a gas analyzer. It just so happens that I've been given the unfortunate opportunity to do a before/after emissions test (that's right I failed emissions and got a free re-test, might as well convert to DIS first). **Waste spark does not appear to help emissions. My HC's are higher than I would like.


Engine Swap @ Motiva
I drove the car from San Diego to Albuquerque to enlist the help of my best friend Scottie at Motiva Performance Engineering. The guy is a genius and one of the few people who understands and respects my goals for the engine. He swapped the engine and tuned the EMS while I mostly took pictures.

Balanced and Blueprinted Injectors
I swapped over my 240CC OBD1 VTEC injectors which had been balanced and blueprinted by RC Engineering. This not only improves fuel flow but also the spray pattern. The result is injectors that are better than brand new factory injectors and that are more consistent from one cylinder to the next, resulting in a more accurate O2 reading so the ECU has more accurate control of the overall AFR.

And with that, the 220k mile factory D15Z1 and tranny went to the big recycler in the sky.


Peak HP / Torque
The end result of tuning was 119hp and 99ft/lbs at the wheels! So at this point I have already exceeded the Si's power. The picture above shows over 30 dyno pulls (I think it only shows 9 at a time). The crazy spikes were caused by Scottie doing a long dyno pull with shifting. The time in the bottom right corner indicates that we finished tuning at 4:30AM.

He got the car to start up and idle reasonably well. We did some street tuning, and then I headed back to Salt Lake where I was left with finishing the street tuning myself. At this point I will recommend some reading material.

Recommended Reading (Tuning)
How to Tune and Modify Engine Management Systems: Jeff Hartman
Building and Tuning High Performance Fuel Injection: Ben Strader
Engine Management Advanced Tuning: Greg Banish
AEM EFI Basics: (download from their forum)

I will talk a great deal about tuning a standalone for economy at a later date.

HX Wheels
As for the physical wrenching on the car, the puny 13 inch VX alloys wouldn't fit the Integra front brakes, so I sold them and found a set of 14 inch lightweight HX rims. They could easily be mistaken for VX rims when seen on a 5th gen Civic. The Integra front calipers require a little bit of grinding or a spacer in order to fit the rim.


You wont find HX wheels on ebay. If you find them on craigslist, they're painted and/or curbed. They're a ricer's favorite. Car-parts.com will search the nation's salvage yards. I found a set of three at a local junkyard and picked up the forth later.


OBD1 LSD Transmission
The transmission I chose is from the earlier generation JDM D15B. This tranny has factory LSD and the SOHC VTEC gear ratios. Clearly this is not the most economical trans available, but remember that my goal is to exceed the stock VX economy; not get the most economy I possibly can. So this trans suits my overall goal of the ultimate daily driver.

Lightweight Flywheel
I replaced the flywheel with an 11lb Exedy flywheel and OEM replacement clutch. If you go too light with the flywheel it will waste gas because you will have to rev high to leave from a stop. The Exedy is only a couple lbs lighter than the stock VX flywheel, which in turn is lighter than the other SOHC flywheels.

Weight Reduction
I have been reducing weight where it is not perceptible to the driver or occupants.

Retained the VX's lightweight Alternator Mount
Retained the VX's lightweight Engine Mount
Removed Intake Manifold Bracket
Removed Rear Speakers
Removed front and rear Bumper Supports
Removed SRS System
Removed Driver's Knee Bolster
Removed Spare, Jack, and Tools
Removed Ignition Coil, Rotor, Ignitor, Plug Wires
Replaced Steering Wheel with a smaller non-SRS wheel
Replaced cast iron exhaust manifold w/ SS Header
Replaced intake pipe with aftermarket CAI
Replaced battery with Odyssey PC680MJT
Replaced suspension with Tokico RAK Coilovers
Swapped DC Integra front seats
Installed lightweight Rims (15in Rota Slipstreams for summer, 14in HX's for winter)
Installed lightweight Flywheel

Weight Additions
I've easily added as much weight as I've removed, and will probably add some more weight down the line. I like to think of it as getting rid of dead weight. The weight you add is functional and increases the useability of the vehicle. It's the same concept as adding a roll cage to a race car that has been stripped of it's interior. These are the items I feel are significant (included some negligible stuff).

90-91 Civic Si 15/16 brake Master Cylinder
DC Integra front/rear brake swap
Neuspeed front upper Strut Tower Brace
DC Integra front lower Crossmember Brace
DC Integra GSR front Swaybar
Progress 24mm adjustable Rear Swaybar
Larger diameter and wider Tires
AEM Twin Fire ignition module
CBR Ignition Coils
D15Z7 vs D15Z1 (slightly heavier?)

And before anyone makes a dumb internet comment, I'd like to say that I'm 7% body fat. I always have been.


suspendedhatch 04-12-2008 04:22 PM

I'd like to take a short break from that and quickly dispel some FE Myths I've come across on this forum and others.

Coasting to a stop in neutral USES MORE GAS than coming to a stop in gear. Fuel injected vehicles have a strategy called DFCO, or Deceleration Fuel Cut Off, which means that when you foot is off the throttle and the RPMs are above 1000, the injectors are TURNED OFF. This is possible because it's inertia keeping the engine rotating. The wheels push against the transmission which pushes against the crank. When you put the car in neutral, you disconnect the crank from the trans. The RPMs drop to idle rapidly, and the ECU turns on the fuel injectors to idle the engine.

Shutting down your engine at a red light wastes gas because it takes an enormous amount of gas to start a car. When I was delivering pizza I would average 5mpg less than normal, and the only difference was all the short trips requiring me to start the vehicle.

Running lean at all times does not increase fuel economy. Running too lean can hurt mileage under certain operating conditions, such as acceleration. Running lean benefits FE under cruise conditions, but not if you run so lean that the loss in power requires and increase in throttle.

I saw someone's post where they mentioned running an AFR of 10:1 on a stock motor "for best power". Best power on most modern engines is right around 13.2, and manufacturers will run in the neighborhood of 12.5 for engine safety. 10:1 is insanely rich. It will cause bore wash which means you clean the oil off the cylinder walls increasing engine wear and in turn blowby and weak compression. I consider that a waste of gas even though you are at full throttle and not concerned about mileage.

suspendedhatch 04-12-2008 04:33 PM

Planned Modifications
Tuned Intake Pipe
Electric Water Pump
Cruise Control
Antenna Delete
Get a 1/4 Mile Time
Install "VTEC-E" Valve Cover
Endyn Roller Wave high compression N/A Pistons
Tune the individual cylinder trims
Tune the injector phasing
Tune the Part Throttle Ignition Timing and VTEC-E Crossover on a load-bearing dyno

Soon I plan on redoing my crappy custom exhaust. I'm going to order some 2.25in mandrel bends, two 18in long Magnaflow Resonators, and most likely I'll retain my 2.25 Magnaflow Muffler.

suspendedhatch 04-12-2008 05:11 PM

I'm sorry about the seeming lack of continuity and contradiction in time flow from one paragraph to the next. The truth is (not only am I a scatterbrain at the moment), some things were tried, didn't work, were put back to stock, and then later executed successfully. Other details of the timeline were contracted just for the sake of brevity.

GasSavers_Erik 04-12-2008 05:41 PM

More mpg than a VX and more power than an si would be a great combo, especially for the ppl that think that gas saving cars can't merge safely into fast traffic.

I'm looking forward to seeing your gas log when you get your vehicle in the garage.

suspendedhatch 04-12-2008 06:24 PM

When I'm tuning the car I get as low as 31 mpg. When I drove to Salt Lake from San Diego I averaged 44 mpg. When I was exploring the city and looking for houses to rent, I averaged 36 mpg. I've spent a lot of time on the ignition, idle, and start up since then. But it's going to be a while until I can go without tuning between fill ups to see what mileage I'm at currently.

Tuning wastes gas cuz you spend an hour or two idling in the driveway, or starting and stopping the engine 20 times, or purposely driving inconsistently to reach each load/rpm cell. Not to mention driving with your foot on the brake and driving up hill in too high of gear to reach those pesky very high load / very low RPM cells.

I wish I had my own load bearing dyno.

civic94 04-12-2008 08:14 PM

well i have a ex/si tranny on mines, and i averaged 45 mpg when i had a 50/50 city and highway commute. its all in how you drive it

my best was 55 mpg averaging 50 miles per hour on a trip

well its a great thing that your trying to get more power and efficiency out of a civic, but it would be nice if the transmission can be like a si tranny from gears 1-5, and 5th gear is just like a vx one

DRW 04-12-2008 08:26 PM


Originally Posted by suspendedhatch (Post 95833)
Fuel injected vehicles have a strategy called DFCO, or deceleration fuel cut off, which means that when you foot is off the throttle and the RPMs are above 1000, the injectors are TURNED OFF.

Since you have EMS, can you change the DFCO rpm? I've lowered mine to about 938 when the engine is fully warm, it's higher when the engine is cold. It's a nice mod since there is very little engine braking at low rpm! I can coast in gear for a good distance without slowing much.


Originally Posted by suspendedhatch
I saw someone's post where they mentioned running an AFR of 10:1 on a stock motor "for best power". Best power on most modern engines is right around 13.2, and manufacturers will run in the neighborhood of 12.5 for engine safety. 10:1 is insanely rich. It will cause bore wash which means you clean the oil off the cylinder walls increasing engine wear and in turn blowby and weak compression. I consider that a waste of gas even though you are at full throttle and not concerned about mileage.

That's an interesting interpretation. I suspect you're responding to something I wrote in 'Remapping the ECU for lean burn'? I've edited two of my posts to make them a little clearer. This one: https://www.gassavers.org/showpost.ph...5&postcount=21
and this one: https://www.gassavers.org/showpost.ph...98&postcount=5
Thanks for the feedback.

VXRider 04-12-2008 09:28 PM

This is a great thread, I'm interested to see how your car turns out. I'll definitely be following.
Keep it up!

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