The tricks up my sleeve... Methods I may implement for better FE.

[SVOboy]

I am just saying that I think the diesels honda and toyota bring to the us in the next few years will beat VW in the emissions department, Im not saying that some of their cars aren't comparable.

EDIT: For example, the diesel released in the US will be a 50 state diesel, which no one else has right now: http://www.iht.com/articles/2006/05/...rg/sxhonda.php

[Hockey4mnhs]

GO HONDA GO i cant wait to get one

[Wyldesoul]

There's also the matter that I highly doubt that in EPA tests, they make sure not to use the turbo.

When you engage the turbo, you jam more air into the engine, and therefore more gas to keep the stoichiometric A/F ratio.

Of course if you get into the turbo, you'll use more fuel.
I've found that at least with the Ford 2.3, the Turbo gets around the same FE as the N/A, highway at least. City, the turbos usually get less than the N/A, but that's because you do a lot more accelerating, and therefore use the turbo a fair bit more.
Well, that is with the average cars, and average drivers.

Quite obviously in tests they'll use the turbo, but if you don't use the turbo, the cars usually end up having the same FE.

I'm not trying to decry you guys, but I'm just going on the experience that I've had with owning both N/A and turbo ford 2.3 cars (Mustang 2.3, and Thunderbird 2.3 turbo), and what I've gleaned from frequenting the forums for both cars.

Turbo charging seems the best way to add lots of HP without sacrificing FE. Get rid of all back pressure in the exhaust system, use the turbo for the back pressure, and know that you have power if you ever truly need it.
Just keep the delicate foot that has been trained to maximize FE, and you wont ever build up enough exhaust velocity to engage the turbo. There will be a restriction to the intake, but at partial throttle, that won't make much of a difference.

My opinion based on experience and my knowledge. There is a rather good chance that I'm wrong, and that when you start getting into the really high FE realm, that a turbo, even when not engaged will sap the FE, but at the realm I'm at the N/A and turbo have very little difference in FE, and that seems to be the average across the board for most owners in the forums I usually frequent.

[rh77]

...made me think of this thread from about a year ago.

The mods on this guy's GSR included a Zero-PSI turbo that improved economy as explained. So it is possible to boost for FE...

RH77

[landspeed]

Originally Posted by omgwtfbyobbq

That's the great part about the EPA highway test. It's consistent! So, given the same car, one with a NA engine, and another with a turbocharged version of the same engine and a taller transmission, on the same test. It's evident imo, that the turbocharged engine is less efficient than the NA engine if it gets worse mileage, because it's over the same test, in the same car, with the same engine, and a slightly more efficient transmission ratio. The only variable I can think of would be the ECU, but I'm pretty sure that's the same for both, since all cars have to keep the AFR at 14.7:1 during normal driving unless they're lean burn, diesel, or hybrid iirc. .....

I would say two other reasons are, that turbo engines (at least mine) might enrich the fuel mixture at a lesser throttle than a NA engine, presumably because if you go on full boost, the engine heats up inside, and then cruise at part throttle, it might detonate due to the extra heat that you wouldn't get in a NA engine.

Also, turbo versions of engines generally have a lower compression ratio, again making the engine less efficient. Diesels have an extremely high compression ratio.

My car has a lot of torque at about 2000RPM, but, below 1400rpm, there is very little torque at all. The newer 2.0 16v high compression engine (mine is 1.8 8v low comp) is so different; if you just touch the accelerator slightly at 1000rpm, you can feel the power of the engine, and the car will begin to speed up if on a straight or slight downhill. Even the 1.0 Nissan Micra/March 16v engine is like this - a lot of torque low down. With my car, I need to keep the revs at 1500rpm minimum, in order to accelerate at all.

[Snax]

landspeed has it correct. It's about safety margins. While a higher compression motor can afford the random detonation here and there, a turbocharged motor is far less tolerant to it as cylinder pressure is increased. One good detonation event can literally blast the piston ring lands apart or worse. That simply doesn't happen with your average NA motor. So in the case of the turbo, they map extra fuel in to mitigate that possibility as well as reduce timing advance.

[omgwtfbyobbq]

Originally Posted by trebuchet03

Careful... that is quite easily a fallacy (slippery slope?)...

Thermal efficiency and fuel economy are very different things If you want to compare the efficiency of heat engines, compare the energy cost per kW

If the same test compares the same cars, over the same cycle, with the same engine, and (taller) gearing that's favorable in the turbocharged car for fuel efficiency, with the turbo car getting worse mileage than it's NA counterpart with shorter gearing. It's evident that the turbocharged engine is less efficient (over that cycle ) than the NA engine imo. I dunno what else to control for...

Originally Posted by landspeed

I would say two other reasons are, that turbo engines (at least mine) might enrich the fuel mixture at a lesser throttle than a NA engine, presumably because if you go on full boost, the engine heats up inside, and then cruise at part throttle, it might detonate due to the extra heat that you wouldn't get in a NA engine.

Also, turbo versions of engines generally have a lower compression ratio, again making the engine less efficient. Diesels have an extremely high compression ratio.

Yes. I don't think that's a problem at part load, since at most part load the turbo'ed engine probably still makes less power than the peak for the NA version. More throttle enrichment on WOT and peak might be present, but even then, the turbo Eclipses were intercooled to avoid that very problem. I think all things being equal, at part load, Mitsubishi still had to have the car at stoich.

Originally Posted by Snax

landspeed has it correct. It's about safety margins. While a higher compression motor can afford the random detonation here and there, a turbocharged motor is far less tolerant to it as cylinder pressure is increased. One good detonation event can literally blast the piston ring lands apart or worse. That simply doesn't happen with your average NA motor. So in the case of the turbo, they map extra fuel in to mitigate that possibility as well as reduce timing advance.

I would guess that tolerance to detonation has more to do with the power/L and engine speed where detonation occurs, than any inherent difference between a turbocharged and NA engine. In any turbocharged engine, they need to have more fuel, because they have more air, compared to aNA at the same speed. But, the engine is likely still at stoich for most driving conditions, due to emissions regulations. Any risk of detonation will likely be mitigated a bit by way of well designed intercooler. The turbocharged Eclipse motor put out ~100hp/L, which is what some NA motors can do, so it shouldn't be a matter of adding additional fuel and running the AFR richer than other manufacturers in a well designed system imo. I think you touched the point, different CRs, which imo is why the turbocharged motor was less efficient over the EPA highway cycle. There is probably some portion of the load map where the turbocharged engine is slightly more efficient due to higher peak cylinder pressure and turbocharger efficiency, but because of the supposed power requirements of today's vehicles, most drivers, and the EPA highway test, seldom see that portion. So, for most low load operation, the turbocharged engine will be less efficient than the NA engine imo, and this seems to be backed up by the EPA highway results with the same car/engine.

P.s. You sure that bike is 700 MPG Equivalent Energy?

Originally Posted by SVOboy

I am just saying that I think the diesels honda and toyota bring to the us in the next few years will beat VW in the emissions department, Im not saying that some of their cars aren't comparable.

EDIT: For example, the diesel released in the US will be a 50 state diesel, which no one else has right now: http://www.iht.com/articles/2006/05/...rg/sxhonda.php

Orly? Yarly! Honda, Toyota, or VW may have the cleanest 50 state diesel, but Honda's offering in Europe hasn't been very different, so I doubt it will be much different if/when released over here.

[Gary Palmer]

Welcome to GasSavers!

I am normally driving an 89 Honda Wagon, although I am temporarily driving an 87 hatchback. In any case, for economy and functionality, I have been very pleased. I'd leave the A/C in and use it in Florida. If you don't turn the A/C on, it pulls virtually nothing for power, but it's still available when it gets hot and muggy.

I've considered the type of modifications you are considering. However, I still have a D15/Z1 and an HF transmission modification, which I know should be able to get me up to the high 40's or low 50's, while running something which is currently available.

I had heard of a person who put about a 5 psi boost on a Geo, and they were able to get quite a bit better mileage, without unduly stressing the engine.

I will be interested in following what you do and what your results are, keep us posted, please.

[trebuchet03]

Originally Posted by omgwtfbyobbq

If the same test compares the same cars, over the same cycle, with the same engine, and (taller) gearing that's favorable in the turbocharged car for fuel efficiency, with the turbo car getting worse mileage than it's NA counterpart with shorter gearing. It's evident that the turbocharged engine is less efficient (over that cycle ) than the NA engine imo. I dunno what else to control for...

That's what I'm getting at... the engine cycles are not the same -- "sameness" means the system model is the same -- turbo charging can be modeled as a reheat stage (something the NA system won't have). I'm not saying that particular setup is or isn't more efficient (because the design determines that and there are plenty of ways to design a turbocharger system) - I am saying that it is a fallacy to make that comparison as a statement of general (or possibly specific to this case) fact.


Hands down, I won't argue that the test shows different fuel economy results reliably. Simply, thermal efficiency is 1 - (heat out)/(heat in). Which is why comparing thermal efficiency of two engines VIA mileage can't happen for engines that have different power ratings (unless adjusted by the ratio of power generated - which is not linear).

[DrivenByNothing]

The ECU will receive a modified voltage from the O2 sensor in order to lean out during closed loop operation. Detonation is obviously a realistic problem. To combat this, I will be implementing water injection. Water injection is very effective at preventing detonation and has several other benefits.

Water Injection Benefits:
Raises octane of the mixtue
Increases compression (water is incompressible)
Cools incoming air
Steam cleans cylinders

I'm sure I'm missing some. Water injection is much easier to implement on a turbocharged engine.

Another reason for the turbo, is to allow for higher compression to be created in the motor in order to test E85.

So the reasons for boosting are a) Ease of implementation of water injection b) Ease of creating a higher air to fuel ratio, c) Gain of some extra power for a small displacement engine, and d) Increasing of compression for alternative fuel applications.

If it doesn't work out, most of my investment will still have progressed me forward.