The typical A-series engine buildup threads always seem to be concerning producing more power. This thread is completely different.

I am interested in maximizing the fuel mileage capabilities of an A-series engine. Yes, even moreso than these cars could muster from the factory. I am competing in events called "Economy Runs" here in the US. My car is a '77 B210. It is the same car as seen in this thread: here. It's twin carbed 1608cc A-series will need to come out temporarily for these "Economy" events as it only gets 25 miles per gallon.

The B210 is a natural choice for these events because economy is exactly what the car was built for in the first place. But my 1608 has twin Dellorto 40mm carbs, small Crane cam, and has a fairly high compression ratio at 10.25 to 1. So now I'm thinking about going back to the stock fuel sipping configuration - or maybe even a bit further.

The plan was to remove the side drafts and reinstall the original intake and original Hitachi carburetor. Then a friend pointed out to me that the high compression I am currently running in the 1608 is a great for gas mileage. I had forgotten about that fact. That got me thinking and reading. I read an article all about compression ratios and how it effects power and economy. One quote says: "Increases in compression ratio do not only impact power generation; they also create gains in fuel efficiency. The higher the static compression ratio, the more fuel efficient it will be. This is the reason for diesel's superior economy over spark ignition engines."

It goes on to say that: "If an engine having an original static compression ratio of 8.0 to 1 was increased to 11.0 to 1, power would rise by only 5.2 percent, but fuel economy would improve nearly 20 percent!"

Now I'm thinking about building another A-series engine specifically for fuel mileage. Instead of detuning the 1608, it seems like a better idea to start from scratch with a low mile standard bore A14 block I've got here.

I read up about the different cylinder heads on this site in the Tech section. Unlike all of the "power" buildups for the A-series and the using better Oval port heads for maximum flow, it seems like the best bet for fuel efficiency will be the smaller round port heads. I checked my stock of heads and found a really nice condition "990" casting round port head. It is from a 1980 US spec A14. Here's what the cylinder heads article says about the 990 casting: These came on the "GFU" and "MPG" cars (USA-market B210 and B310 fuel economy champion models). Perfect!

So basically, I'd like to build a standard A14 engine but with high compression [10.5 or 11 to 1]. Yes, this will require expensive premium fuel [with some leaded racing gas mixed in as well to run, but I am trying to get 50 mpg with a B210. Has this ever been done?

Has anyone here ever experimented with trying to exceed the great fuel economy of the A-series engine?

Cheers,

Mike

i just went lpg (like you guys and propane) and got instant fuel economy gains... and savings.

Bit different to your style of racing.

Round port was used by factory to choke thenegine down, reducing power but increasing economy.

Could be done with stock hitachi, jetting could also be improved.

Yes yes YESSSSSSS
I have been thinking about a real fuel miser engine for a couple of years, & what it would take to really drive your dollar further.

In my case I started with the car & for me it would have to be a B20 [Datsun 1000 Ute] as these are the lightest of them all. The B210 is a barge by comparison.

I had also thought 'A10 engine', but my 1200 GX engine in my old B10 sedan got much better mileage than it did with the stock A10 engine, so 1200 engine it had to be, but not a later A12 as the 1200 engine is a direct bolt-in. I once got almost 55mpg [Imperial gallon] from my [heavy] 1968 Datsun 1000 four door sedan with a 1200GX engine, so the potential is really there.

My version of this 'virtual' 1200 engine used A10 flat top pistons with the cylinder head from the KB10's version of the A10 engine. The flat top pistons naturally provide more compression but the KB10's round port head is worth another half a point of compression in stock trim as well.

I also wanted to wrap the inlet manifold in copper tubing that ran hot water through it for good manifold heating & I thought that an 1-1/4" SU would be good as it is a high vacuum design carb that is almost infinately tuneable.
Warmed air would also be drawn from over the exhaust manifold. Turning liquid fuel to a gas is of paramount importance & not a single micro droplet can be allowed to escape.

An A15 flywheel is nice & heavy so should produce advantages here, but it adds some weight overall. Never mind, some sacrifices must be made.

I also thought of the 56A five speed [F5W56A] as the extra gear between 1st & 5th will also be good for economy, ... & it's a straight out bolt-in.

Switching a 3.54 to 1 ratio H150 differential into the original B20's housing is no problem either as it too is a bolt-in & final gearing can be controlled with tyre size on skinny steel wheels which are readily sourced in 13" & 14" sizes. The only downside is that the H150 is an iron diff & the original B10 & B20's H145 diffs were alloy case units. Bummer.

Further, but minor weight reduction can be achieved with the removal of the spare tyre & it's mounting gear & even the passenger seat as well as the substitution of a motorcycle battery in place of the original.
The smaller & lighter 1200 radiator should also be quite adequate in this application.
The heater was an option in the earliest of the B20 Utes so leaving it out will save some weight & still be road legal in Australia.

Such a car would not be a road burner, but man, it could make a tankfull of fuel go a very looooooong way.

My thoughts:

A12A (same motor mounts) 10:1 compression, Throttle body fuel injection, 5 speed OD, 155/80 tires, lower the car, make a lexan aero grill air dam set up, ditch all the weight you can, synthetic oils etc etc.

I would think 65-70 MPG is attainable.

Tom

im also thinking fuel injection would be very high on the to do list for an engine concerned mostly with fuel efficiency

its also better for high comp as the tuning is more precise

I think u r starting off on the wrong foot using an a14, its a fair bit thirstier than an a10, but if u are using a 1200 body the a10 might not be viable powerwise?. Tho i think a stripped out B210 would come close in weight to a B10.
id look at a free flowing exhaust, and least restrictive air intake with cold air induction. the high comp is good,
programmable efi will allow better dyno tuning and lean running on closed loop, an improvement of say 12:1 up to 14:1 air/fuel ratio in highway cruising, thats if u want to spend that amount of time and $. Its possible a tiny main jet coud achieve the same if u can experiment with an a/f meter.
friction modify the motor with slick50 or nulon, likewise the gearbox and diff.
run 50psi in pizza cutter tyres,
also if u r really keen, make up an aerodynamicr front nose out of say perspex, fibreglass of even carbonfiber, and reduce drag underneath with a flat peice under engine bay going as far back and as tidy in meeting up to all edges as possible.
look forward to the results of this project.

Quote:A stocker can do that:


Why not try something difficult like 70 mpg? Your 20% increase from high compression alone should get you to 60 mpg...

aerodynamics, low roll resistance, and low weight is the key.
Go forth and spread yee word upon disbileavers

Goodluck

Quote:
I'll disagree with a couple of points here.

A freeflowing exhaust will not do any harm, but at the engine speeds that an economy oriented engine will be operating at when in max economy mode, even a stock exhaust will not be a hinderance. None the less, if a new exhaust is needed, then a small improvement in size will be OK

The 'least restrictive intake' will also contribute nothing since the actual volume of air passing into the engine will be quite small when in max economy mode. Good for max power, but not for economy.
Small ports & manifold runners mean that the gas velocity is acceptably high at max economy engine speeds which contributes to stable mixtures.

Cold air induction is BAD since it will not help with the conversion of liquid fuel to a gas & it's only the gas that actually burns. If the manifold is cold, then some of the fuel condenses on the walls & is drawn into the cylinders as a liquid.
This results in a lean mixture which robs power meaning that even more throttle is needed to provide the required power.
Worse yet is the fact that at the higher throttle opening, the vacuum signal is reduced & the higher the vacuum, the better the conversion of liquid to gas.
With warm air & heated manifold, ALL of the fuel should be converted to gas & if the vacuum signal is high the leanest setting can be made at the carb. This means that every atom of fuel is producing power instead of washing the oil from the cylinder walls.
For pure raw economy, warm is good, but for racecar power, cold is good.

High compression is good, but only within reason. After all, it's gotta run on pump fuel.

If EFI is used, then yes, the fuel mix can be programmed pretty lean, but on an A series engine, for a specific event, it can be a big spend & a well tuned carb, when driven properly, can give a very good account of itself in this department.

The only other thing I can think of is a hotter thermostat. For economy, a hot engine is a thrifty engine & lets remember, pure unadulterated economy is the goal here, not power or performance.

And remember a A10 may not be best because it will be working harder to gain and maintain speed. You would get more fuel economy with a slightly larger engine as its not working so hard.

Is LPG more efficent though? Yes its cheaper but you use more of it! This test isnt $/fuel its distance/fuel!