[Infidel]

I was reading the turbo thread and it got me thinking about the possibility of using a turbo for pure FE rather than for power. Currently, I think the insight turbo that's out there is running something like 7psi of boost through an intercooler and fuel managment by upping the fuel pressure. What if you did this:

Ditch all the fuel managment and intercooling. Replace the turbo with an IHI-RHF3, have a waste gate set at something really low, like 2psi, and try driving around?

The RHF3 is a ball-bearing turbo designed for super small motors (about half a liter). By putting such a super small turbo on the insight, you're running the turbo way out of its efficiency band. What this will do is jack up charge temps, but that's what the insight seems to like for FE and lean-burn. 2psi is very mild, and the technology exists to clamp the MAP voltage so that the ECU never sees boost. A super small turbo will kind of behave like a "free" hair dryer blowing into your intake. Since you're not artifically adding fuel, you have the effect of leaning out your mixture a little less than 10% or so.

At the very least, it would make the "hot air mod" obsolete, and could potentially give you summer FE in the winter.

Ideas?

 

[Dougie]

Seems to me that the point of forced induction is to increase the amount of air that gets in. That means you need to put more gas in to keep the mixture constant.

But much of the energy loss in an engine is due to friction, and adding forced induction doesn't change that much.

The way to improve economy using a turbo is to make the engine much smaller first. If you run 15 PSI of boost you roughly double the effective displacement, so if a 1000 cc engine without boost is appropriate for the Insight, perhaps a 500 cc engine with a blower would be good.

That's what many of the small European diesels do, for example. Like the SMART car...

 

[Infidel]

Hmm... sort of. The traditional purpose of Forced Induction is to extract more power out of a motor of given displacement. The only way to get more power is to burn more fuel. For Performance applications, you install the turbo, tune, burn more gas and go.

For FE applciations, (like small turbo-diesels), what's happening is really alot like what Honda did with the insight. I.e, you can run a smaller engine than someone can reasonably live with for steady-state cruising, but have power-on-demand from the turbo. FE turbo setups just replace our IMA system with boost and a temporary increase in fuel consumption.

Since reducing the insight's displacement is not reasonable, my idea was to use a super-small turbo "on the sly" to very slightly increase the air density in the motor *without adding more fuel*. Yes, this is "dangerous", however, if the charge is kept *very* small, I think the effect you will be like a mini-lean-burn under acceleration. The fact that such a small turbo heats the air will also trick our ECUs into entering/holding lean-burn easier.

Also, under light load (typical current lean-burn), I wouldn't expect the turbo to be adding very much positive pressure, if at all. Running premium fuel should also give you just enough anti-detonation protection to get away with a *slight* leaning of the A/F mixture under load.

 

[Insightful Trekker]

Personally I don't think what you want to try will work. The specifics for any _potential_ MPG improvement form adding a turbo will be highly dependent on driving conditions and style.

Dougie's got the basic concept correct :!:

But it seems to me that Willie or JackMPG may be able to provide some real world data. Their turbos are about as minimal as can be installed. But from wht I've read of their general driving pattern their not in the hyper-miler catagory (no offense), but the do achieve improved MPG under more aggressive driving conditions.

The converse is not necessairly true.

Willie, Jack :?: Got some hyper MPG data turbo vs non turbo :?:

 

[Dougie]

Most of the time you drive the Insight at small throttle openings. (If you care about mileage, at least!) So there's plenty of extra air available if you need it--just crack the throttle open a bit more.

But that won't lean out the mixture, because the feedback loop controlled by the O2 sensors will increase the fuel supply to keep the mixture where the system thinks it "should" be. This will happen if you add forced induction, too, and is why it's so easy to add superchargers and turbos to modern cars: The fuel system automatically compensates for the extra air (to a point).

If the goal is to lean out the mixture, it would be easier to fool the O2 sensing system somehow. You would probably melt a piston, though.

On the other hand, this basic idea--lean burning--is one of the important features of the car already. If you want to pursue an investigation of this path, figuring out a way to stay in lean burn mode under a wider range of operating conditions would be very useful...

 

[Willie Williford]

FE

John:
During my installation and testing of the turbo I posted a "Comparasion Run" with two other Insighters. (See page 1 of the original thread, Turbocharged Insight, May-2003).

Also, during the development of the " fourth injector", I found that the Insight would take 1.5-2 pounds of "boost" before the engine would starve for gas. Felt Just like hitting the rpm limiter.

Didn't try it much at high rpm. Ran the vehicle like that for over a week while the injector system was designed..........For what you may "gain" in FE, very low percentage, I don't think it would be worth the effort. Jackmpg has some stats I believe on wideing the lean burn window because of the turbo installation.

Hope this helps.

I can be a hypermiler. Best run: Campo Ca. to Yuma Az..94.6mpg for 123 miles.......... Got a 35mm photo to prove it.
An absolute comparasion can only be done on a "dyno".

Willie

 

[Insightful Trekker]

Re: FE

Thanks for the quick reply Willie.

Well,

Campo to Yuma @94.6 for the entire trip would put you _solidly_ in the hyper miler category. Reads like your current set-up gives the extra power without any sacrifice in economy (when driven in the hyper miler style). It doesn't read like you gained any "pure" MPG's.

But the dyno test would be the only _true_ comparison. Too many other factors on the road to isolate MPG's. IMO I agree that a turbo won't be a big MPG gain for an Insight, but I do wish it were so easy.

 

[Infidel]

What are the operational conditions that cause lean-burn to be held longer? From what I've read here, it appears that engine load and intake temperature are the two major factors, correct?

If this is true, than a sufficiently small turbo *should* be able to provide some increased airflow even at small throttle openings. Also, any increased airflow will also generate some heat. Both of these factors should trick the ECU into holding lean-burn longer, I think.

Do all existing insight turbos run with an intercooler? Does anyone have any piping that goes straight from the turbo to the intake manifold, and are there any wastegates out there that allow you to clamp boost at 2lbs?

A simple system that allowed me to do a mild hill climb in lean-burn 3-5mph faster than what I can currently do will be well worth the expense *for me*.

 

[Jackmpg]

Turbo Without Boost

John, Infidel too,
Glad Willie chimed in, he's really the expert here, Iv'e learned allot from him. Could it be done, of course. No fuel management, no intercooler. I'm not using an intercooler now, free warm air mod.

Turbo's are designed for boost so it may be difficult to adjust one down to zero boost with the waste gate. An external greddy waste gate or relief valve may get you close. The stock Insight MAP sensor will read 11 psi of boost, so no issues there.

Insight is allot faster, even without positive boost as the turbo reduces ICE load. Trick is to use a turbo that starts to spool early, if you want to hypermile. So it reduces load early, while your in the LB/P rpm range. Willie and I both have that, I believe, turbo is spinning quite fast even before you get to "boost", reducing load. We can stay in LB/P as long as conditions permit.

With a stock Insight Iv'e done the 110-120mpg @ 43mph thing. With the turbo am able to do same at 48mph. Also LB/P, can take that up to 71, 72mph at a stretch. More enjoyable for me, is getting mpg above 60 at a little over 80mph. Below 80mph mpg drops, it's in the gearing. Willie stated a long time ago, our cars are over geared a little. Turbo helps make up for this, even without positive boost you still have forced induction over coming partial vacuum.

Now, to turbo or not. Cost is not expensive by comparison to doing larger engines. Don't need the intercooler. But for $200 more you can get a Fuel Management Unit and have the best of both worlds. I find that I'm winning more average drivers over by showing them a hybrid can beat the pants off what most of them are driving and still get extreme mpg. Most of them are not impressed by a car that backs up traffic, no matter what mpg's your getting driving slow. I followed Willie's good example to turbo an Insight to make the little car breath taking to drive and promote our little cars. Well, what do you think all? Jack

 

[Insightful Trekker]

Re: Turbo Without Boost

Jack,

Thanks for the quick reply. You seem to confirm Willie's post that you get more power without a significant MPG "hit". And that hyper MPG is still available when you drive as such.

Infidel,

There are physical limitations in regard to lean-burn and engine load. Its a delicate balance and one that cannot easily be broadened. From Willie's and Jacks turbo experience it looks like manifold pressure is not significant, but more than zero, in widening the lean-burn window.


See these lean-burn discussions for further information:


Is the holy grail of 'lean burn' an illusion?
http://www.insightcentral.net/forum/viewtopic.php?t=186

Lean Burn clarify
http://www.insightcentral.net/forum/vie ... php?t=2945

Unlimited Lean Burn?
http://www.insightcentral.net/forum/vie ... php?t=3115

HTH!