I recently got my hands on a fixer-upper 1989 Honda Hatch back.
Everybody's made them fast, I want to make them amazingly fuel efficient. I'm thinking either the HF engine and tranny, or the Vtec-E... I at this point don't know much on either. I'm under the impression that the HF is a d15? with a really cool tranny, restricted intake, and I'm assuming restricted exhaust.
What is the Vtec-E?
Oh, and how "impossible" is this?

 

sounds crazy

 

vtec-e is a d15 also that would be your best choice for mpg cause i got a friend with one in his daily 92 coupe gets 45 and that motor has 200+ plus

 

It's not a standard d15 though, right? It has the Vtech head, programming?

 

efficiency is key...i think it can be done. hypermiling techniques and maybe an HHO setup and you'll get there. just remember oxygen and map sensor adjustments if you play with the hydrogen.
if that guy in ohio can build a 400hp mustang that gets almost 100mpg, you can certainly make one of our little cars pull it off

 

HHO? what's that? (ps... look up the guy who goes by the moniker "Motorhead Messiah")


Modified by RasHondasDriver at 9:42 PM 10/11/2008

 

If it could be done on the d series engine, honda wouldn't have invented a new engine to do it with the insight, and even 80 was somewhat tough unless you were already hypermiling

I'm pessimistic, but maybe 80 just isn't very realistic unless you have a lot of time and money

I'll cast my doubts aside though and say unto you 'good luck'

 

without removing virtually 3/4 of the cars original body weight (rendering it illegal to be driven on city streets i'm sure) i don't see 80mpg as a feasible possibility.

 

Maximun efficiency can't be acheived with the hatch unfortunatly. The kamm back of the crx as well as it being lighter stock for stock give it a good advantage in drag coefficient and, therefore mpg.

That said, it's nonsense to go buying a new car just to increase the mileage a bit more... But if you happen to come across one it would get you a few more mpg.

Ever wonder why the insight and prius look suspiciously like the crx?

Look into A LOT of weight reduction.

 

*VTEC, Vtech is a phone.

UKDM D13 block with D15Z1 VTEC-E head+tuning and HF transmission would be a killer MPG setup

I managed to get 57mpg highway in a D15B VTEC 88 Civic Hatchback, so with more "mpg" mods I could see how 80mpg, highway, is possible but still difficult to achieve.

 

Honda was experimenting with Lean Burn engines to get more MPG but that system has issues of it's own. So Honda gave up on developing it further. The theory behind it is solid, but unfortunately emissions regulations, and the demands on it in an automotive application makes it impractical. It's not meant for acceleration, and works better in a steady state.

You would have to look to other avenues for gains. Such as aero, rolling resistance, lightening the car. Using a more modern engine with a newer computer behind it. The quest to minimize emissions has benefited fuel economy; because less gas coming out means less emissions. All of those can be pushed to some point. There's even coatings that you could apply to the internal components of the engine, transmission and driveline to reduce friction.

Janos

 

^K2e2vin, totally had to be a miscalculation saying you got 57 mpg with a D15B VTEC....unless you were pushing the car along or something.

Anyhow, I'm on a similar journey, I'm putting a D15Z1 VTEC-E engine into my 1991 Civic HB STD in a couple weeks, I just ordered it. I am a delivery driver and get about 25-27 mpg driving in these severe conditions I do (all stop & go, and pretty fast). I used to get 33 mpg when I had regular highway traveling. My car is rated at 28 city/33 hwy, the 92 VX is rated at 39 cty/ 49 hwy. I should save at least $500 a year in gas at the current price. Also I'll be going from 70 hp 4 speed, to 92 hp 5 speed (if I can find a 5 spd cable trans!) and yes the HF transmission is the best for FE.

People have done this conversion and it's somewhat documented. It seems to be a very easy swap, hopefully I'll do a write-up on it if I can get a memory card for my camera.

GL

 

and that 400hp/500ft/lb tq 100mpg mustang is bs too. not that you should need anything more than your own brain to figure this out..

http://ecomodder.com/blog/2008...anure/

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by therotaryrocket &raquo;</TD></TR><TR><TD CLASS="quote">^K2e2vin, totally had to be a miscalculation saying you got 57 mpg with a D15B VTEC....unless you were pushing the car along or something.

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Nope, calculated it like 6 times because I was surprised(using distance travelled divided by fuel consumed; same way that SCC did).

With that said, I was using a DOHC ZC transmission with 4.25:1 FD, cruising from 3700-4000RPM at ~70MPH on I40. The brakes are larger than stock(heavier 10.3" EX rotors) but otherwise the car was gutted and 11lb Miata wheels.

As stated before; it's about efficiency. These (16v)motors need to rev some to where they reach higher efficiency at part throttle. Lowest rpm is not always the best because you'll need to give it more throttle to sustain speed(so in some applications, no, the HF/CX/VX transmission aren't always the ideal choice for best fuel economy).

Now, lets look at the 8v engines(including VTEC-E engine). These motors will benefit from keeping the revs lower with the tall transmissions since the aspiration setup is more efficient at those RPMs. That's the whole point of the 8v setup...better VE at lower RPMs.

It should also be noted that two (Aquafina and Bone) and probably more respectable members noticed better MPG when letting their motors rev a bit higher. I believe Aquafina is getting better MPG than his stock transmission with his ridiculously short transmission.

 

I'd believe 80mph more.

 

Idk but if you're crazy I am too... Building a D15Z1 88 CRX HF hoping for similar numbers. If hypermilers can get 75mpg out of a 92-95 VX Hatch I'm hoping for 80+

 

So it looks like your saying the D15Z1 VTEC-E is an 8 valve engine, that's totally wrong, it's actually 16 valves, and all 16 open and close the whole time, only when vtec is engaged they all open a little further.

Also a transmission with longer gearing is more efficient because the gears are more efficient. Every turn of the crank results in a further distance turned at the wheel. Weight is less of a factor on the HWY than in the city.
Your right the VTEC-E is designed to be more efficient at lower revs, and the performance engines more efficient at higher revs.

I read an article once that explained the internal combustion engine efficiency curve. The harder you work the engine the more efficient it becomes, but the more fuel you use. So really if you get a small engine and tall gearing the engine will be working hard, but it's smaller so it'll use less gas.

Also if you haven't heard of pumping losses than you couldn't take advantage of another possible FE technique (which has mixed results in the real world, but technically should be more efficient). If you know about pumping losses in the intake system than you'll know it's part of the reason diesel engines are more efficient and also more efficient with taller gearing and a smaller engine.

Some manufacturers are now taking advantage of a fly by wire throttle body because it allows the ECU to control the angle of the throttle valve, thereby variating the degree of vacuum and directly changing the pumping efficiency. Also the VTEC-E uses a 5 wire wideband O2 sensor and runs in a lean burn mode of up to 20:1 A/F ratio iirc, compared to the leanest mixture your D15B VTEC runs....someone chime in, i imagine it goes no leaner than 14.7:1 A/F unless your decelerating. So how do you compete with that?

I must ask you K2e2vin, how do you measure the amount of fuel consumed? did you pump the first time at 85* F and then refill at 55* F? are you just judging by your odo and your fuel gauge? It is pretty difficult to get an accurate result anyways, but sorry to say i'm still in disbelief that your setup netted a real 57 mpg....then again I'd be a hard person to convince of this as I'm getting a D15Z1 for the reason of FE and I'm trading power because of it, so I wouldn't want to do that if I could get 130 hp and 57 mpg. I just find it very far fetched.


Modified by therotaryrocket at 12:48 AM 10/12/2008

 

I referred the D15Z1 as a 8v engine because that's where the FE comes from; the gears are set up to keep it in 8v mode as much as possible.

How I measured it was filled up fuel all the way and used google map to calculate the total distance(like 109mi trip one way). What I did was traveled that route, back and fourth, and measured the amount of fuel it took to fill it back to the top(at the pump). Temperature was not that big of an issue, because on both days that I filled up was like 85-90F, although that is a big variable to consider, along with the accuracy of the gas pump. I did this on two weekends, and got ~57mpg on the first weekend and ~55mpg on the 2nd weekend. I'm planning to take the car to Charlotte in a couple of weeks and I'll measure what it's doing then(although the transmission is different; stock CRX Si transmission going in while the DOHC ZC is getting a 4.437FD and, when I get some money/part released, 3.083 first and MFactory LSD).

Also, weight makes a difference on hills. You live in NC, you know what I'm talking about

Longer gears do not mean it's more efficient. For the same displacement, you would use more fuel for a higher load(less vacuum/wider throttle angle). When you have the revs real low and way out of it's "part-throttle efficiency" band, you're bogging the motor, so to say, and have to give it more throttle to sustain speed. There's a really nice FE thread on D-series where a member actually datalogged and got worse MPG when he switched from a Si transmission to a DX transmission. He observed that the engine was spending more time in the upper map region(higher load); working harder to run at lower rpm. Diesels also work in mostly lower RPM bands, so you can't really compare them to the 16v motors revving at higher rpm.

My ECU was a socketed P28 with a slightly modified P08 basemap and LC-1 WBO2.
Also, yes, the leanest target A/F ratio is 14.7, but you'll see richer mixtures if you need to give it gas. At around 20% throttle the target a/f ratio is around 12.5:1. Now when I was cruising, I was able to sustain ~70mph by just laying my foot on the pedal(pretty much weight of my foot) and giving slight pressure on occaisions, this was at ~4000rpm mind you. I didn't datalog while driving but if I had to guess, it was probably at around 5% throttle most of the time. If I were to use a longer transmission and say I had to keep it at 20% throttle to maintain speed, the injector duty increases roughly 17%, or theoretically dropping it from 57mpg to 48mpg. So, comparing my motor to the D15Z1, the Z1 has the potential to get even better MPG than my setup, but the way I'm driving with my setup works well vs people who've thrown in a VTEC-E engine expecting incredible MPG without changing their driving style(which I would have to do too if I switched to a Z1).

And to address drive-by-wire; it reduces or eliminates some "user variables" in order to get better performance. Simple as that. Say a car is rated 40mpg hwy, there will be people who will get higher and lower than that number. "Assist" them and it will help them close to or better than that number.


Modified by K2e2vin at 5:00 AM 10/12/2008

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by K2e2vin &raquo;</TD></TR><TR><TD CLASS="quote">I referred the D15Z1 as a 8v engine because that's where the FE comes from; the gears are set up to keep it in 8v mode as much as possible.
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It's not "8 valve mode" its technically 13v mode (3.25 valves per cylinder) it opens one of the intake valves just a little to promote swirl but still uses all 4 valves.

 

Honda first called that CVCC in the 78 civic I think...... Chevy calls it "Vortec"

 

you would need to use diesel to get closer to that i feel. probably 50-60mpg would be the limit.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bob_760 &raquo;</TD></TR><TR><TD CLASS="quote">

It's not "8 valve mode" its technically 13v mode (3.25 valves per cylinder) it opens one of the intake valves just a little to promote swirl but still uses all 4 valves.</TD></TR></TABLE>

You're right, I stand corrected. I just have 8v stuck in my head. Although, I believe one valve cracked open was mainly to prevent fuel pooling. So, it could be considered 12v mode.

Fueleconomy.gov lists estimated MPG. There's plenty of guys getting 60-70mpg in a VX on gassavers.org.


Modified by K2e2vin at 1:44 PM 10/12/2008

 

I dunno, i have to agree that it was for the swirl effect.

They even implemented that swirl effect to some degree in the design of the newer d16y8. the offset divider in the intake ports caused swirl and increased low cam performance/ecomomy.

 

I never said that it didn't prevent or help attribute the mixture from swirling, but rather to keep fuel from puddling. The swirl effect could be created with just one valve opening; but fuel will start building up behind the closed valve.

 

i still say it's possible. we just haven't perfected ways to get the most energy out of gasoline. most of it is waste energy expelled from the tail pipe. IF, big IF, you can make your motor more efficient (by adding hydrogen or whatever) and you can improve your driving techniques, you will see 80mpg or more. i know that the insight was rated for 53mpg, but there were guys getting 90+ out of them with simple mods.