Best engine for a hypermiler Z

[naviathan]

This thread has been a bumpy road let's get it back on topic. What engine would be a good choice to make a Z get outstanding mileage without being too slow to drive safely.

 

I am going out on a limb to say an early 1990's 1.5 Honda motor with a TON of mods to be able to mount it longitudinally in the Z.

 

It worked in my Civic so it should work in a Z.

I would go with the KA24 on MS2.

[ZR8ED]

Another way, somewhat mentioned is improving the efficency of your engine. VE (volumetric efficency) A more modern driveline likely has a better ve than our stock motors, but since many of us are rebuilding them, we can do a lot to improve our ve. My last L6 motor was built with this premise, to make a decent amount of hp without going crazy $ on exotic parts. We lightened what we could. ie crank, flywheel, pullies, and helped improve the flow of fluids ie oil/water passages by matching waterpump ports, removing rough casting marks where possible (not polishing). Crank and rods were highly polished, cyl head was generously ported (overkill for street engine) polished etc etc. plus a hole bunch of other rebuilding techniques that I know little to nothing about.

 

What I ended up with was one heck of a fast 8000RPM redline motor that could run on high octance pump gas. Got into the low 20 mpg's with 4.11 gears and triple weber carbs and fat tires weighing in at 2680lbs (lowest it ever weighed on a scale)

 

So what I am getting at is we have some good options to improve the ve of our stock engines, can improve our aero, and still have a good time on a track!

 

I can certianly attest to the improvements from a programable FI system. My megasquirt runs awsome, and my cruising a/f ratio is low 15's on the highway. Nice and safe, and I am now happily cruising in the very high 20's, yet I can drop the hammer, and fry my 315's! More tuning may get me into the 30's, but my z is not a daily driver, and I won't care much until it costs me more than $100.00 to fill it. It is reasonable enough for me right now.

[Gollum]

Regardless, this thread was created to discuss possible engine choices for a hypermiler Z, not to debate the safety of various hypermiling driving techniques. Please don't hijack the thread.

 

Word! There's lots of engine options, so lets get to them!

 

Modifying an S30 for hypermiling is just another direction for these awesome cars to go in. It doesn't mean the Z-car will be the best hypermiling car there is, it means you can hypermile, and still drive a Z-car!

 

Hey look everyone, he does have some Z bones in him after all.

(just having fun, hopefully you know you'll be family here soon enough)

 

Ok I like the SR20DE suggestion. I'll list some other swaps that should be in the right vein

 

Mazda BP Engine

Toyota 1RZ

Toyota VZ

Nissan VG

Toyota GR

Nissan VQ

 

 

Overall I think motor choice is going to come down to two main factors:

 

1) What transmission options are there

 

2) How much power does it produce

 

The power and price are loosly tied together, and how much power you want is all up to you. As long as it's a newer motor it shuoldn't be too hard to get decent power out of it while retaining some efficieny.

 

There was some talk earlier in this thread about piston disabling during cruise. I'd highly recommend against it. GM was NOT the first company to experiment with this idea and most companies that tried it failed, the engines weren't reliable and had issues because of it. From what I've been told (by someone who's worked for nearly every auto manufacture and would still be working on cars if it weren't for injuries, who's a close friend of mine) that the issue is that when you start disabling cylinders to start to have oil sealing problems around the piston rings. The rings get cold and start to leak. His thought on the new LS2 and other engines doing the cylinder disabling again was that they must be using an ALTERNATING disabling method, so each cylinder fires every other time, but all cylinders are actually still firing. This in effect is LIKE having half your cylinders gone, but that's not what's really happening.

 

If someone actually knows how the system works, please share. But unless I could find out for sure how they're doing it and replicate it in the same way, then I wouldn't bother. Too much risk.

[Daeron]

I typed alot of this up, and I realized I had used lots of capital letters and exclamation points. I'm not being argumentative in the slightest.. but I had coincidentally thought at great length about this matter last night while I was working, and so I had alot to say; John's point was just a great stepping off point for me to bring it up. The caps and !!!!s are only intended to elucidate my position a wee bit more, and attempt to type with a bit of a voice, if you catch my drift.. so I came up here and typed out a clarification at the outset, that this is NOT ranting in the slightest. I FULLY appreciate the complete definition of the term "driving for performance" and respect my masters in that regard.

 

 

You've never driven on a race track at 10/10ths for 45 minutes. Get your competition license and do a Spec Racer Ford rental at the next local SCCA event or rent a shifter kart and run a 30 minute heat race.

 

Nor was I able to achieve anywhere NEAR the best fuel economy!! I HAVE driven 10/10ths for minute long autocross courses, so I DO have a taste of what the difference is between street and track.. not to mention that I honestly concentrate on driving as much or more than anyone in a family of racers (they've told me that when riding with me behind the wheel) so, just to make it clear, I am not completely BSing on dropping the term "performance driving" around. (just a smidge of the BS)

 

 

 

The point I had intended to make (I actually realized this might get missed last night while I was at work) was that the aggressive, get-there mentality involved in PUSHING the car is FUN, and a natural instinct for any predator-type critter (ie, humans.) It is instant gratification from utmost concentration. Certainly, racecar driving requires a massive amount of control and discipline!! Its not SHEER instant gratification, because if you drive like that, you get more acquainted with walls then you do with turns. It IS a matter of instant gratification nevertheless.

 

Driving for economy's sake, on the other hand, is slow, pedestrian, takes longer to achieve a goal that you know could potentially be achieved quicker.. I am leaving lack of "fun" out of its list of detriments but we all know its there.. In the long run, driving for economy is about Delayed gratification: paying less at the pump/saving the whales/having a blue sky instead of a brown one (how can anybody cope with living in LA? sorry) All of the benefits of economical driving take time and investment to show up.

 

 

 

Generally speaking, it is much more difficult, and requires more self-discipline, and self control, to delay gratification.

 

THAT is the sense in which I meant economy driving takes more effort than driving for performance. Because, the fact of the matter is, PERFECT FLAT throttle control, keeping it RIGHT on the edge of stoich (slightly lean) and responding to every dip and bump and curve in the road, is hard as hell even in South Florida! My ground is FLAT! NO horizon, so one might think that super-economy was possible, because all I need to deal with is turns, and a few short bridges and canals. (the canal banks are, as a rule, about 10-15 feet higher than ambient elevation.. most of which is somewhere from 10-40 feet above mean sea level. Twenty miles from the shore.) In reality, all that my "super-economy" driving should take is me functioning as a constant human cruise control, but thats INCREDIBLY hard to do, both functionally and mentally.

 

Now, at the same time, I know that even driving at the ragged edge of performance is also a balancing act with economy driving, too.. so is Pizza delivering, at $4/gallon in the town where I work. Seriously, this neighborhood has the most self-centered and ignorant, unskilled drivers in a tri-county area where that problem is rampant... so I am always pushing towards the front of various packs of slow-dogs, dealing with jerks who want to fly past me, etc..... all the while, trying to save gas, yet still get my pizza there in time to make decent cash. (side note: this job sucks. Bad. summertime is going to be a season of change for me.) I am about the exact opposite of a race driver when at work: trying to save gas, yet still get there before EVERYONE else at ALL costs. My point is, I DO understand that racers are often racing to get there before everyone else at all costs, yet still trying to save gas.

 

 

 

 

Whew!!! I didn't mean to turn into a preacher like that, so I am sorry. Now, back to reading the rest of the thread!

[Daeron]

okay, now, more pertinent to the discussion at hand, I would say that the most likely option is going to be 240SX engine and trans. I would call an older 200SX engine and trans the BEST option; possibly an early 80s pickup truck and 2wd trans. (unless you WANT 4wd?? )

 

 

Why?

 

NAPS-Z engine, if you find a way to fuel inject it, WILL be your ultimate mileage nissan four banger.

 

Has nobody else here ever had a friend who saw their Z-car and told them about the PHENOMENAL mileage that they got out of this little old datsun 200sx that had a four cylinder, but eight spark plugs????

 

If all else fails, take a carbureted manifold for the engine, chop the intake flange off, machine it for injector bungs, and find another car's intake manifold to weld to it for a throttle body. Or use the downdraft carb manifold with a TBI injector throttle body from something.

 

 

Now, the KA... youve got DOHC, 4 valves per cylinder. thats mighty nice. They ARE all over the place with fivespeed transmissions bolted onto them. There IS a useable stock fuel injection system on it already, and even if you don't use that, or don't use it forever, having all those bits already made for that car could be seen as helping the project immensely, as far as "simplicity factor." I do not know what parts are available to increasing the VE, but with 4 valves it should be easier. I personally might even look into redesigning the internals somewhat (are there any other cranks for that motor? hmm...) but building the engine from a bare block up for this purpose would naturally be IDEAL. I REALLY like what ZR8ED brought up regarding the specifics that went into his engine build.

 

 

The VG30 SOHC is also widely available, and everything that could be said about the KA (except 4v heads) can be said about it.. but I wonder if the extra displacement is needed. De-stroker VG anyone?? To me, if it comes down to these two, the VG/KA question should be settled by close examination of available internals and manifolds to build your "ideal" VE longblock.

 

 

Personally, I suspect that VERY mildly turbocharging and fuel injecting an old L-series 1800 or 2 liter might even be better.. For that matter, leaving it NA and setting up a mikuni manifold with the Accurate Injection ITB kit might not be that bad either... After all, how many people get up to 30 mpg with our six cylinders??? Again, I think of the old 210s at 35 mpg in the 70s on craptachi carburetors. (Hitachi SU's are the exception to the craptachi carburetor rule)

 

 

To me, pulling an engine out of another make (unless the trans comes with it) is too much of a stretch... I suppose I have a certain Nissan brand loyalty that is far from universal here, but I just can't consider engines from other vehicles. There is something of a knowledge void there as well. Anyhow, your choices are varied, and it really depends on what you can, and are willing to do that is not "stock" to an engine for this project....

 

Can you FI a carb'ed motor?

Can you mix and match the trans?

Can you rebuild the whole motor?

 

Nissan gave us everything from 3.3 to 4.11 gearing for the rear pumpkin, so thats a given. You COULD use a truck transmission and find a rear diff to make it work. You need to examine the transmissions available for each engine, and decide how much you want that to impact the engine choice.. and then decide how crazy you are willing to go with the engine itself to make it work how you want it.

 

Just dont overlook the old L and Z series nissans... they made 35-40 mpg on carburetors, what can they do with real engine control?

[Nick56289]

The Datsun B210 got about 50mpg so it would probably be a good candidate for a hypermiler. However im not sure if then A12 engine would be a good candidate for a Z swap because they made less than 100 hp ( I think around 80). Something to ponder though.

[Clifton]

okay, now, more pertinent to the discussion at hand, I would say that the most likely option is going to be 240SX engine and trans. I would call an older 200SX engine and trans the BEST option; possibly an early 80s pickup truck and 2wd trans. (unless you WANT 4wd?? )

 

 

Why?

 

NAPS-Z engine, if you find a way to fuel inject it, WILL be your ultimate mileage nissan four banger.

 

 

 

Naps Z's did come with efi on atleast 3 models. If it were a decent engine they would not have scrapped it for the better KA.

[seanof30306]

My thoughts on laying out the parameters for a hypermiler engine:

 

1) If you look on fueleconomy.org, and compare different models, you see that 4 valve per cylinder, DOHC, VTEC, etc models tend to get worse MPG than their lower-tech counterparts. I don't know that there's anything inherently less efficient in those technologies, I'd tend to think they'd be more efficient, and therefore, should get better mileage. The thing is, those technologies were designed for performance, and would likely be employed in engines with higher compression, more aggressively cammed, etc., as well as put in cars with stiffer gearing, more performance accessories, etc.

 

2) Fuel injection is way preferrable to carbs when it comes to MPG. All fuel injection is not created equal, though.

 

Throttle body injection (TBI) is sort of the red-headed stepchild of fuel injection. All it really is is a carb with more precise fuel metering. The fact that it mixes the air and fuel in the intake means it has all the inherent weakness of wet-flow systems. Believe me, if my Firebird hadn't come with TBI, I never would've messed with it.

 

Direct port injection is much more efficient. The fuel injector is placed right at the intake port on the cylinder, so there is no pooling.

 

Even better yet is sequential fire direct port injection, where the fuel injector meters the fuel with incredible precision, introducing it only at a very specific point during the intake stroke.

 

But wait, there's more. MAF (Mass Air Flow) injection determines how much fuel to add to reach a pre-determined air/fuel ratio by actually sampling the air.

 

MAP (Manifold Absolute Pressure) works sort of like a blind man who has memorized the route to work. The amount of fuel is determined by engine vacuum. The problem with that is, if you make any changes in airflow (free-er flowing exhaust, intake ari, etc., the MAP system can't make adjustment, all it can do is follow it's fuel tables, as dictated by engine vacuum. Furthermore, if you change camshafts, you can throw the system totally out of whack. More duration means less vacuum, which MAP fuel injection interprets as the throttle being opened further. You can be sitting at a stoplight and it thinks you're running down the road at 40 mph. MAP is also very vulnerable to vacuum leaks, etc. MAF is a much better way to go.

 

So, for our theoretical Hyper-Z, I'm thinking the ideal induction system would be a Mass Air Flow, Direct Port, Sequential fuel injection system. Preferably, it would be an OBDII system, as the pcms are faster (and therefore more agile), and they are much easier to hack and tune, and you can often use wideband O2 sensors, which makes your tuning much more precise.

 

As far as the engine itself, that's a little more complicated. If we were looking 100% for economy, we would go with the smallest displacement, simplest, lowest hp engine possible. An 80hp Z-car, though, is kinda sacrilidge.

 

I'm not sure where the right compromise is. I'd think that's going to be pretty individual of a choice.

[Daeron]

Naps Z's did come with efi on atleast 3 models. If it were a decent engine they would not have scrapped it for the better KA.

 

Were any of them tuned port injection? which cars?

 

Sean:

 

I was not aware of what you said about 4 valve engines. Was the data such that multi-valve engines, or multi-CAM engines were incriminating, or can you not reliably tell the difference? Eh, moot point.

 

The reason I brought up the 210 was not to suggest dropping an engine straight out of one of them into a Z, rather to suggest looking long and hard at how that engine was built (rod, stroke, bore lengths, compression ratios, even combustion chamber and piston shape if you can get it) and possibly build an L6, or an L4 to match that as close as possible, yet still retain enough POTENTIAL power for use when needed; as mentioned regarding motorcycles, power IS a safety feature once in a while.

 

Don't overlook the possibility of building an engine that makes more power than you ever plan on using: thats the potential beauty of turbocharging. Build a WEAK engine, and when you push the throttle down so far, suddenly it wakes up.. there HAS to be a way to delay turbo kick-in relative to throttle location.. wouldn't that simply be a crazy-strong wastegate spring?

 

Now is as good a time as any to throw in this mantra: highest MPG for any given engine is achieved when cruising at or around the torque peak. Horsepower being a function of torque, an engine that gets quickly (~2200-2500 RPM) to 100-120 ft-lbs and stays right about there will be PLENTY fast by the time its wrapped up to 6K, if you feel like it.

 

If memory serves, the HF CRX engine made a max of like, 85 horsepower... and about 105 ft-lbs of torque. The torque peaked at 2200 RPM.

 

If you seem to want to nix the 4 valve idea, then I am very prone to say find a NAPS-Z engine or an L20B and play with it. The L-series should be easy to find a weber manifold and get some ITB setups for, if nothing else.. if I am not mistaken most of the time when someone weberized a NAPS-Z engine they used a downdraft; that is the only reason I suggested TBI.

 

I wouldn't knock it (TBI) about so badly for economy purposes though... Perched on top of a hot engine or exhaust, once the fuel is sprayed by the injector at twentysomething PSI into air moving at ridiculous speeds, pooling isn't SO horrible. Don't forget that ALOT of I-4s are crossflow heads, so the intake charge is kept alot cooler.

 

My old TBI subaru is capable of some respectable mileage numbers (1.8 boxer, OHC, tiny ports and manifold, 91 hp/108 ft-lb., up to almost 40 mpg reliably reported and beyond that reported with room for doubt) and I bet the firechicken's problem was the fact that it was a lunky, smog-era V8 more than the fact that it was just an "electronic carburetor" feeding it. My point is, the 5.0 TBI they put on the SBC (at least as it was found in my buddy's camaro) in the 80s is not a slow system, or a fast system... I've always considered it to be somewhat, half-fast.

 

Now, one last point.. what I mentioned about best MPG at torque peak should also influence your selection of transmissions/gearing. This, in my mind, is the best argument for sticking with an L-series or other nissan box.. much knowledge is had about them, much variety is available.* (If you do an L20B, then you can build the engine, stick it into your car as is with the tranny and rear end you have, dyno tune it, and FIND exactly where you want to put the gears, and THEN shop around for your gearbox of choice.

 

*AND, speaking of variety.. you could even theoretically DOWNsize the rear diff on this car to an R160, if you wanted to keep your eyes peeled for an older gen subaru with an LSD. The added traction from an LSD, plus the lighter and smaller rear axle... I am picturing a "no hole shots!" sticker on the horn button.

 

 

 

I have A LOT to say about this, because I have thought about it all a great deal and my family has discussed it as well. Honestly, the best hypermiler might just be turbo-diesel! If not an LD28, then what about a volkswagen? Anyway, my point was not to remind myself of ANOTHER point to bring up, it was to apologize for my continual, long, rambling posts... but there is SO MUCH to discuss and I do so love typing my words for you all to read.

 

 

 

Edit-- Irony is typing all that, reviewing it, adding a point or two, apologizing for its length, and then hitting a button that says "Quick Reply."

[kiwi303]

So, for our theoretical Hyper-Z, I'm thinking the ideal induction system would be a Mass Air Flow, Direct Port, Sequential fuel injection system. Preferably, it would be an OBDII system, as the pcms are faster (and therefore more agile), and they are much easier to hack and tune, and you can often use wideband O2 sensors, which makes your tuning much more precise.

.

 

I've been googling.

 

Ok, an SR20DE has Squential injection, fit an extrudabody ITB system for individual metered injection, if you pick a post-'96 engine it should have OBDII since thats when the govt mandated all cars to have OBDII systems, the SR20DE uses MAF air flow sensors not MAP.

 

sounds like it meets all your needs, plus it has the same block and thus mounting points as the SR20DET which has conversion mounts available for the Z cars already, no need to do a home bodge job.

[seanof30306]

highest MPG for any given engine is achieved when cruising at or around the torque peak.

 

That's not exactly correct. Highest efficiency is achieved at or near the torque peak. Modern cars cruise in overdrive well below the torque peak. My 383 Firebird, for example, has a torque peak at 3400 rpm, but, in 6th gear, I cruise at 1600 rpm at 60 mph, and get 31 mpg doing it. I guarantee you covering the same distance in 4th gear at 3400 rpm will not yeild anywhere near that economy.

 

Maximum efficiency can actually be calculated using the bore/stroke ratio. I have the formula somewhere, but can't find it right now.

 

Torque, however, is important in a hypermiler, and has a seat at the table. The more torque an engine has, the less throttle it takes to motivate it. The less throttle it takes, the better the mpg.

 

So, I'm thinking the ideal engine for our Hyper-Z would have a broad, flat torque curve, low in the rpm band.

[seanof30306]

I was not aware of what you said about 4 valve engines. Was the data such that multi-valve engines, or multi-CAM engines were incriminating, or can you not reliably tell the difference? Eh, moot point.

 

I don't really follow this.

 

Here's what I was saying. If you go to fueleconomy.gov, you can look up the EPA fuel economy of various cars. Having done this quite a bit, I have noticed that the higher tech models tend to get worse mileage.

 

For example, a 1998 Honda Civic 1.6 SOHC manual shows 27/34 mpg. The 1.6 SOHC VTEC manual Civic shows 25/32.

 

I don't recall seeing any of the higher-tech models getting better mileage than comparable low-er tech models.

 

The reason I brought up the 210 was not to suggest dropping an engine straight out of one of them into a Z, rather to suggest looking long and hard at how that engine was built (rod, stroke, bore lengths, compression ratios, even combustion chamber and piston shape if you can get it) and possibly build an L6, or an L4 to match that as close as possible, yet still retain enough POTENTIAL power for use when needed; as mentioned regarding motorcycles, power IS a safety feature once in a while.

 

Don't overlook the possibility of building an engine that makes more power than you ever plan on using: thats the potential beauty of turbocharging. Build a WEAK engine, and when you push the throttle down so far, suddenly it wakes up.. there HAS to be a way to delay turbo kick-in relative to throttle location.. wouldn't that simply be a crazy-strong wastegate spring?

 

The problem with that is the turbocharger adds significant restriction to the exhaust system. The same engine with a turbo would get worse mpg, even if you kept your foot out of it.

 

If you seem to want to nix the 4 valve idea, then I am very prone to say find a NAPS-Z engine or an L20B and play with it. The L-series should be easy to find a weber manifold and get some ITB setups for, if nothing else.. if I am not mistaken most of the time when someone weberized a NAPS-Z engine they used a downdraft; that is the only reason I suggested TBI.

 

I wouldn't knock it (TBI) about so badly for economy purposes though... Perched on top of a hot engine or exhaust, once the fuel is sprayed by the injector at twentysomething PSI into air moving at ridiculous speeds, pooling isn't SO horrible. Don't forget that ALOT of I-4s are crossflow heads, so the intake charge is kept alot cooler.

 

My old TBI subaru is capable of some respectable mileage numbers (1.8 boxer, OHC, tiny ports and manifold, 91 hp/108 ft-lb., up to almost 40 mpg reliably reported and beyond that reported with room for doubt) and I bet the firechicken's problem was the fact that it was a lunky, smog-era V8 more than the fact that it was just an "electronic carburetor" feeding it. My point is, the 5.0 TBI they put on the SBC (at least as it was found in my buddy's camaro) in the 80s is not a slow system, or a fast system... I've always considered it to be somewhat, half-fast.

 

Each intake valve is only open during one revolution out of 4; 25% of the time. During the other 3 revolutions, the intake valve is closed.

 

With TBI, fuel is constantly being mixed with air in the intake plenum and travelling down the intake runners. During the 3 out of 4 revolutions that the intake valve is closed, that fuel re-liquifies and pools around the valve, only to fall into the combustion chamber on the intake stroke in liquid form. It is partially re-atomized during the compression stroke (the higher the compression, the better the re-atomization), but it is not an efficient burn of the fuel.

 

Even in some direct-port injection systems, there are problems. Batch fire injection fires the injectors twice per four revolutions. Pooling still occurs, but less so,

 

SFI (Sequential Fire Injection) is the most efficient, by far, as it only introduces fuel into the individual cylinders at the precise moment when the intake valve opens, delivering a perfectly atomized spray directly into the intake port. That is the reason why SFI is able to deliver such impressive MPG at such low emissions, when compared not only to carbs, but to TBI and batch fire direct port injection.

 

TBI was a great improvement over a carb, and I have spent considerable time working with it, but, in 2008, it just doesn't make sense to look at transplanting technology that has been outdated for over 20 years into a project vehicle whose goal is efficiency when there are so many better choices readily available. It would be one thing if you had a donor car sitting in the back yard, but to go out and get a TBI FI setup for this project is like going out and buying an ATARI to play video games on.

 

Also, as far as GM TBI processor speed? The '7747 ecm found in third gen Camaros and Firebirds has a baud rate of 8200. I would point out that that is slower than canine offal, but I don't want to run afoul of the mods.

[OlderThanMe]

Nobody has mentioned the CA18DET...

Pick one up for a grand on Ebay with a 5 speed, install your aftermarket EFI of choice, and an instant 35-40+mpg with 175hp.

 

Then you can do some aero stuff like lowering, narrow(stock...lol) tires, block off the front end, etc...

 

Check out:

www.ecomodder.com

[RedEvilrps13]

^^FINALLY.

 

you know i was thinking of that on the way home from work yesterday.

 

i love CA's but most people consider them old and crap compared to the SR20...even though the CA is a mini RB and has a WAY better head design than the SR.

 

but i digress.

[Daeron]

to be honest, I was apparently grossly under-estimating your ambition and your confidence in your ingenuity.. Thats a very short way of trying to say a whole lot

 

I'll forget about the turbo point; why I hadn't had that beaten into my head at all yet is beyond me, it was mentioned above already. your points about any TBI system are taken and acknowledged.

 

The entire 16 valve versus DOHC question was basically wondering whether the additional CAM used most commonly to operate the extra pair of valves, or if it went hand in hand with the additional valves themselves. Basically, I was pointing out a nuance in the 4 valve/cylinder field, and asking if you had a clue whether it mattered which side an engine was on.

 

Don't underestimate the possibility of finding a GOOD TBI unit to install a pair of in place of SU carburetors on a stock manifold for an older engine, though! I agree completely with you regarding the rather feculent nature of the chevy TBI system, but I think VERY broadly outside the box on a number of things... I've given a world of thought to slapping a pair of the TBIs from my subaru onto one of my uncles roadsters and trying to make it work. With two runners per body, it would only take two injector drivers to run a hack-job at semi-sequential injection. There are only two possibilities regarding firing order: the first is, either of a pair will take turns, and if "carb" A is for cyl 1-2 and B is for 3-4, then you will always get a 2-4-1-3 order (ABAB; ) OR, they are synched, and you will always get a 2-4-3-1 (ABBA, essentially AABB) order. BUT.. like I said, you appear to consider tuned-port of reasonable importance.... so I will stop the now.

[seanof30306]

to be honest, I was apparently grossly under-estimating your ambition and your confidence in your ingenuity.. Thats a very short way of trying to say a whole lot

 

I'll forget about the turbo point; why I hadn't had that beaten into my head at all yet is beyond me, it was mentioned above already. your points about any TBI system are taken and acknowledged.

 

The entire 16 valve versus DOHC question was basically wondering whether the additional CAM used most commonly to operate the extra pair of valves, or if it went hand in hand with the additional valves themselves. Basically, I was pointing out a nuance in the 4 valve/cylinder field, and asking if you had a clue whether it mattered which side an engine was on.

 

Don't underestimate the possibility of finding a GOOD TBI unit to install a pair of in place of SU carburetors on a stock manifold for an older engine, though! I agree completely with you regarding the rather feculent nature of the chevy TBI system, but I think VERY broadly outside the box on a number of things... I've given a world of thought to slapping a pair of the TBIs from my subaru onto one of my uncles roadsters and trying to make it work. With two runners per body, it would only take two injector drivers to run a hack-job at semi-sequential injection. There are only two possibilities regarding firing order: the first is, either of a pair will take turns, and if "carb" A is for cyl 1-2 and B is for 3-4, then you will always get a 2-4-1-3 order (ABAB; ) OR, they are synched, and you will always get a 2-4-3-1 (ABBA, essentially AABB) order. BUT.. like I said, you appear to consider tuned-port of reasonable importance.... so I will stop the now.

 

Once again, I'm not following you. "Tuned port" refers to the length of the intake runners. Longer runners = more torque, shorter runners = more hp. GM, for example, made Tuned Port Injection in both MAF and MAP incarnations. TPI was batch fired, but that was caused by the limitations of the ECM, not anything inherent in the tuned port design.

 

Nothing I've discussed above has anything to do with tuned port.

 

And with TBI, you are still mixing fuel and air in the plenum, an inherently inefficient design.

 

Now, all of my experience is with American V8s, so maybe there's something I'm missing here, but I still can't see the sense of going to the work and expense of adapting a TBI injection system when there are so many other more efficient designs available.

[SHO-Z]

It takes X hp to move the Z down the road at 60 mph. The same can be said to accelerate to get there. Lowering the weight and improving the aerodynamics on the Z is another mileage improver. Go trough the car and remove or lighten everything that you can. A full belly pan will improve the Aero on the car along with cleaning up the front end.

 

As for the engine/ Air Pump, anything that will improve the air going in and out will improve the mileage. I had a 240 about 30 years ago and was getting 30+ mpg all of the time on the highway. All I did was drop the needles in the SUs.

 

My all time best mileage car was a BMW 700 Sport Coupe that I had back in the 60s. Did a mileage rally in it and got 62 mpg, second place to a Morris Minor, am I really that OLD?

 

Yea gas was 29 cents a gallon an I wages were in the $1.50 /hr range an we were concern about mileage!

[Gollum]

For example, a 1998 Honda Civic 1.6 SOHC manual shows 27/34 mpg. The 1.6 SOHC VTEC manual Civic shows 25/32.

 

[caps used for accenting key words, i'm not angry ]

 

Ok... which engines are we talking about here?

 

Honda has made a lot of variants of lots of motors. I've worked on my fair share of hondas and in my experience NEVER ONCE have I seen two engines of THE SAME PEAK POWER have the non-vtec one get better MPG. The reason why most Vtec equiped madels take a SLIGHT drop in MPG is because they recieve a HUGE performance increase, with increased low end torque AND increased high end HP.

 

It's like expecting a V8 mustang to get the same or better MPG than a V6 mustang. Why would it? You don't buy a Vtec model honda for the MPG, you buy it for the power, thus the extra HP brings the MPG down a taste.

 

All things being equal, in my experience the Vtec WILL get better MPG.

 

Example:

 

Stock B16A is capable of 170hp EASY on a stock motor. If you were to build up a D16 to those power levels in the same care I'll guarentee it'll be getting significantly worse MPG.

 

So really what you need to ask yourself, is how much power do you want? If you want 200hp I wouldn't suggest a SOHC 8 valve 4 cylinder. I'd suggest something that gets near or over that stock, and then modify and tune it for milage. Maximize the low end torque giving up some high RPM HP. If you only want 60hp then I wouldn't suggest a 1.8+ liter 16 valve DOHC 4 cylinder, simply because all of them will be way to agressive for that power level.

 

 

I'd forgotten to mention the CA18 motor. They're pretty good from what I've seen. Still think the SR20DE might be the easiest way to go for you still though. It'll make enough power to put a grin on your face and still should be able of pulling down some pretty crazy milage.

[cygnusx1]

Quoting myself lol

The 1984 200SX 4 cylinders were really good on gas too. I drove one 7500 miles in 15 days on a little road trip and got around 37mpg.

 

This is the car we drove around the USofA back in college.

 

 

Great engine, great mileage, great electronics, dual plugs.

[zmaster]

I just watched fox news lastnight, and they showed hypermiling, and it got me interested in it. I have heard moth balls , and or pure acetone can increase your gass mileage greatly.