My office mate pisses me off daily... "35MPG" he mumbles as we walks past my cube...

He owns a new 2014 Mazda 3, a 3000lb car with a 2.5L 4 using direct injection. Our commutes are both in town.

My 2007 Honda fit, a 2400lbs, 1.5L Port Fuel Injection... I can't get better than 30MPG!

He tells me he's running around with a 13:1 compression ratio on REGULAR gas... (Fit is 10.4:1)...

Okay, I'm sold on Direct Injection's advantages...

We've seen adaptations of various VW Fuel Injection Systems on the Type IV... anybody got the bug to try and build a Directly Injected, Mass Airflow and Oxy Sensor managed motor?

Gas mileage? Who cares? Mazda 3? Who cares? Besides that, he probably lies.

Get a FA20 out of a BRZ (FRS).
It is 4cyl, Boxer, 2.0L, direct&port injected with 12.5/1 CR and variable valve timing
I get 30 MPG in the BRZ.

Then you can ridicule him for having ONLY Direct injection.
Tell him "Good Luck with those carbon deposits!! HA HA"

The Direct only engines have a problem with carbon buildup on the intake valves.
The combo port/direct cleans off the carbon.

Oh, and my Passat TDI gets 54 MPG.

Carbon Buildup on the Intake Valve is definitely NOT intuitive. I'd expect if any to be on the injector itself, but I understand that when you run 20Kpsi..nothing is gonna stick to that blast.

Why the Intake Valve? Just because it is constantly cooled?

Interestingly, the first motors retrofited with direct injection performed much worse than their port injected counterparts. Cylinder head and piston top really designs need to be optimized for DI since there is no port pre-mixing. I met some guys from a German university who converted a Honda CBR600RR motor to DI and found performance to be much worse, even after quite a bit of optimization. The other issue is that there aren't too many engine controllers out there suitable for controlling the DI pump (Syvecs, MoTeC M1 series come to mind), so you are a little limited on controls.

Variable valve timing is really where performance lives. With many modern VVT and VVL systems you can continuously "optimize" air movement through the engine and reduce pumping losses, charge contamination, and throttling losses. It's almost to the point that a TB is not necessary (see BMW VANOS where there is no conventional throttle body; it's only used for major flow throttling and all fine tuning is in the valve lift/timing).

The really cool part about DI for me is that since there is no port fuel wetting you can extensively control torque with fuel flow. Port injected engines either just use spark timing to control torque (only useful to about a 20% reduction), or have some torque reduction/increase delay because of fuel supply delay when using fuel cuts for torque reduction. DI injections don't have this problem so almost all torque reduction (literally 60-80% is possible) can be done with fuel. This means that traction control on racecars retains fuel efficiency. AER wrote a great article about it in terms of their LMP2 engines.

Port and direct injection like the BRZ is definitely the way to go!

i read white paper a while ago on D/I. there is a whole lotta black magic that goes into those motors.

VVT, throttle by wire, ign timing insane fuel pressures.

the throttle on those runs like a diesel wide open at light/cruse load.

every thing is controlled by how much fuel, when it's injected and when the ignition fires and the cam phase/ timing.

some serious wizards design those engines.

the "carbon build up' is the oil on the valve stem that doesn't get washed off or burned off in the case of the exhaust valves.

it's more of a gummed up build up.

my nephew had the do the "cleaning" on his turbo cobalt ss, get this they air blast walnut shells into the intake port to clean it. and then shop vac it out.

Certainly the first aircooled type.
I would think the greatest difficulty would be being able to run the high compression and lean mixtures possible as with the watercooled.
A variation on the theme is an LPG (Propane)conversion that used a chamber injector.
From what I've read of the adiabatic cooling characteristics of the gas the method may have some distinct advantages over gasoline.
An informative treatise on the method was written by Smokey Yunick,and entertaining.
http://www.smokeyyunick.com/--------------- -------------- Buy this 1100 page book.
http://www.legendarycollectorcars.com/feat...xclusive-video/
http://www.hotrod.com/how-to/engine/hrdp-1...t-vapor-engine/
https://www.google.ca/#q=smokey+yunnick+fuel+injection

Jim,

Could you please design me an aircooled motor, adapted with today's technology.

You wont feel so good about the port/DI combo once you get the oil analyzed and realize how much gas is in the oil
Who cares if he drives a Mazda 3.

Heh--I know people who can get 50 MPG out of a Fit... MPG ain't everything, and you have a huge influence over what you get by how you drive.

--DD

True that man let me guess

Faster u go the worse the mileage

The more the wind resistance

Click to view attachment
The guts of it.Hasn't been installed into a 914 to date.AFAIK.
http://www.ft86club.com/forums/showthread.php?t=17247
https://www.google.ca/#q=FA20
http://jalopnik.com/5918932/the-wait-for-t...s-crash-is-over.

Could be a challenge to give the T4 a new lease on longevity and efficiency.

All engines have at least some "scavenging" where the intake valve begins to open when there is still positive pressure in the cylinder.
So some combustion by-products see the back of the intake valve.
In a port injection engine the fuel will keep this cleaned off.

The BRZ does kind of sound like a diesel and also has a very loud high pressure fuel pump driven off the cam.

Someone would have to do a boat load of R and D to fit DI to a type 4 engine. you'd need to mount a whole whack of sensors , new pistons so the ultra lean burn would work correctly, not a mater of just machining a random size pocket into the piston either, I imagine you'd need to break out the old slide rule for that one. I'd have to say, you'd be a bit nuts to try, But nutty people keep things interesting. Neat technology, very diesel-esque. I took a training course a few months back on tier 4 final diesel engines, its funny how these engines are, in some ways, becoming more like petrol engines and at the same time the DI petrol engines are using diesel technology.

so his car runs approx 50 miles further on a tank of fuel. less than 2 gallons of fuel saved. big deal. do you own your 07'? casually ask what his 2014 mazda payments are.

My 2010 Fit consistently gets 35-36 mpg.....driven daily in urban stop & go traffic. And I do not drive conservatively....

I would think the major disadvantage is the cooling of the fuel in the intake. Without it, I would think that you would have to add additional cooling capacity.

Click to view attachment
What a great idea Mike,a liquid cooled head for the T4,DOHC 4V,DI.
Crank trigged,variable timing and anything else I can think of.


https://www.youtube.com/watch?v=zcPGfjUO3Yg

https://www.youtube.com/watch?v=E3v2lBpeZPc
https://www.youtube.com/watch?v=78QrZyQInnk
http://www.hotvws.com/news2.php?contentID=70
https://www.linkedin.com/pub/brian-hyerstay/10/b62/93
http://www.kval.com/news/local/Rare-1946-V...-222742581.html

You're killing me.......

I drive JUST in town but on Country Highways.. 8 miles to work, usually average about 45-50 MPH (School Zones and Speed Limits).

I bought a Fit 'Sport' which has 55 series tires, but hardly Steamrollers. ( I own the car BTW, bought it new in 2007 to replace me worn out '96 Mustang GT).

Wife insisted on an automatic (5 speed) for the 3 times a year that she drives it... ( )

I accelerate smoothly (proof that I can drive smoothly.. I got 190K miles out of my Mustang GT original clutch....)

I can't crack 30 MPG in town... shit!!!

Okay, I do weight 240lbs (am working on that).. but comeon....

I'm a Mechanical Engineer.. it's really a question of Efficiency.. this is my biggest pet peeve and bugs the crap out of me to leave any power or mileage "on the table"....

It would be better that I knew LESS about how crappy the Bosch D-Jet system is on 914s.. every time I drive that car, I'm thinking how any $800 Honda could kick my ass in mileage, power, and handling, simply because I've got 1930's technology behind me...

But then i get out of the Porsche and look at it.. and no Honda can ever ever look that good.....

what, spraying fuel on the back of a closed valve with enough extra to hopefully work does not satisfy your mechanical engineering guidlines?

I bought my wife a Base 2015 Honda Fit to replace a 1999 Audi A4
that was killing me on repairs and 80.00 a week in gas. Wife commutes
almost 100 miles a day
The Fit is a CVT, because of a shoulder injury a few years ago.
If she is going to aggravate the shoulder, it will be
when driving her 911 in the summer.
The first week we owned the Fit, we drove it from the N.H. border
to just east of Philly. It averaged 41mpg. I checked just to be sure.
We went back to Philly last weekend. Car has almost 4000 miles on it
and with far less use of Cruise Control, more traffic and 4 snow tires on it, it still
averaged 37 mpg.
Car was 16,500 new. Gas savings alone are worth it, never mind the peace of mind
a new car gives. Also it will allow the 911 to be insured with Haggerty since
your daily driver has to be less than 10 years old.

As I posted in other threads..
We love diesels.. But at the premium prices diesels command plus the
higher fuel costs.. Can't beat the Fit.

The thermodynamic efficiency of aircooled engines.The book.
A lot of work has been done since the Bosch of '68.
It has been seen a 2 plug cylinder provides a more complete mixture burn.
Nickies and lower reciprocating mass,hmm this is getting expensive.

Maybe you should look around on www.cleanmpg.com . They have people getting crazy-good efficiency numbers out of all sorts of things, including Fits.

High tire pressures, and keeping the engine working at low RPM seem to be pretty key for MPGs.

--DD

Believe it. VW direct engines suffer from it across the board. The procedure is to remove the intake manifold and walnut blast the intakes. There's even a special dedicated blaster for it. Takes 5-7 hours on a 2.0 turbo engine, and it may be necessary as often as every 50-60K miles. Trade magazines have run articles on the need and the procedure, and how to get in on the cash cow. BTW, those pesky bits of carbon occasionally break off and bend the intake valves.

Edit: My '02 TDi has gotten as good as 52MPG, and my wife and I aren't exactly fast lane mobile chicanes. We average, in mixed driving, around 47. TDis have an intake carbon problem, but it's from the egr, not a design fault.

The Cap'n

Lol. I drove my 2010 Fit ~77K miles over 4 years. When I traded it in, my MPG was 33MPG. This included winter gas, climbing HUGE hills every day, and miles of stop and go traffic every morning.

If I was driving on flat land, or did not have a lot of traffic to deal with, that car easily got 40+mpg.

My Aunt has a 06 Fit and has averages 40mpg in Washington State.

I also weigh 240ish. Or were you just referring to the weight of your lead foot? Cause I don't think its the car....

I weigh about 165 so you've got some weight on me but I doubt it would cause a huge difference. I vote for the automatic causing most of the decreased mpg. I think it's easier to drive efficiently with a manual than with an automatic.

The DI MINIs suffer from the same problems; the same walnut blasting is required. Oil vapor comes in through the PCV system (and possibly elsewhere), and the oil that winds up on the valves never gets washed off with a nice spray of gasoline.

One of many reasons I am glad I got the non-S Cooper; it has port injection.

--DD

Dave, it has direct injection. its just not high pressure common rail direct injection.

I used to drive 20 miles (out of town) when I first moved here to Petaluma. I'd avg 34MPH. When I landed a job in town, I got several moving violations in a fairly short time (county was Fund Raising). The penalties turned me into an "old man" driver.. I never exceed the speed limits (45-50 on highway, 35-40 on boulevards).

For this reason, I believe I don't have a lead foot.

Probably just asking for trouble, but if i ran a higher viscosity Trans Fluid, could I get it to "lockup" earlier in the rev range?

I know they're not the same thing, but the consequences are the same, for the same reasons.

--DD

Essentially, none of the prince motors are real great.
Its almost like you guys should hire me for your mini division.

Does your car have the flappy paddle shifters? if so its really easy to treat it like a clutchless manual. Use engine braking as often as you can. Leave decent following distance between you and the car in front of you so you dont have to start and stop a frequently. Unless you are climbing mountains on a regular basis (which is a possibility) there is no reason you should not be getting 33+ mpg in your car. If you are a flat lander, you should be getting 40s.

Zach