fuel economy for rotary
 

Hi, does any one know any tricks or ways to make rotary eat less gas, so far I tried the swirling system (tornado) inside my air intake line, it didn't work, as a mater affect I think it made it worst.
:scratch:
So if any one knows anything about fuel economy mods, please punch a line!

crummy fuel economy
 

Hey I know exactly what you are talking about. I have tried everything.
The other night I was watching a show about corvettes and was kinda shocked to find out that one of the original engine ideas for the vette was a turbo rotary engine but scraped the idea because they were fuel gusslers. When I heard that I laughed and said your not kidding. I didn't mind it so much when I got mine in 86 but today it's not so much fun. Gas prices are 4 times what I started out with. Even thought maybe rebuilding the carb would help NOPE. :wallbash:
I guess we just have to face it, if we are going to own one of the coolest cars in the world, :icon_tup: we are going to have to live with crummy fuel economy.

Good luck

MDK

the "tornado intake system" is nothing but a scam. the best way to keep your fuel economy up would be to make sure you are properly tuned, run some seafoam through the tank to clean the fuel system, make sure your tires are properly inflated, etc. what kind of car do you have? those are just a start. if you do a search, you'll be able to find much info on the subject.

Yeah those tornado's are a plain rip off sorry to say. Generally given the nature of a Rotary engine they consume a lot of gas mainly because the combustion chamber is so large. More so than that of a regular piston engine. Like old_skool said, you can have it run about as economically possible for a rotary but it will never compare to a 4 banger.

Its a price im willing to pay to drive such a sick car!

60K tuneup, correct tire pressure, shift before 3800.

And shave some lead off your foot.

cut and paste from another post
 

Lots of things that you can do, but question is, are they worth the effort. If you're getting really bad fuel economy right now (defined as <12 city, <15 highway), then you might try looking into one or more of the following;

Brakes - are your brakes in good shape? Do they drag at all, or do you notice that one brake seems to get hotter than the rest when you stop driving? Brake dragging can dramatically reduce total mpg. Change your brakes and lube the pivot pins to keep things in good working order.

Intake/Exhaust - a restrictive intake/exhaust system, clogged by long passages and/or debris on your air filter can cause poor mpg - get a new air filter element, fix that leaky fuel injector, or retune your carb for a leaner mixture.

Wheel bearings - do you hear squeeks and/or groans from the wheels under light braking or turning? Could be that you need new wheel bearings and grease seals. If yours are worn out, not only will they cause toe problems, but will wear your tires more quickly and increase front-end drag. Get an alignment, replace wearing parts, and set it for minimum toe-in for better mileage.

OMP pump running well? Premixing? Having plenty of oil for internal seal lubrication will decrease internal engine resistance which is a big determinant of mpg. Change your oil and go to a lighter weight (10/40 instead of 20/50) to decrease internal friction.

Tire pressure - 28 may have a nice, comfy ride, but 32-34 (based on tire size and manuf. recommendations) will definitely net you as much as 1-2 more mpg. Less rolling resistance means better efficiency, AND performance.

fuel filter - having a dirty fuel filter will cause the ECU to think that you are running lean, and will open the injectors longer

By far, the biggest contributing factor to poor mpg is your own driving style. Stay out of the secondaries, drive highways when you can, and keep it below 65 on the highway. Use your cruise-control more, and don't drive like a 'rabbit' - drive like the 'tortoise'. Slow and steady wins the race (and pays less at the pump). HTH,

its funny bc for years i figured the lil 1.3litre would get decent gas milage but the more i read the more i see not.

its not like we purchased a bike. motors smaller than a four cylinder but make the power of a v8 and up, yeah fuel's gonna bite. all i know is shift at 3k, ease on the gas, and listen to the other members.

In the FC FAQ, there are links to a few detailed mileage topics.

Anything sold to improve fuel economy is generally a scam. If a 3 cent piece of sheet metal shoved into the intake could improve fuel economy, don't you think the manufacturer would have already installed it? This goes for ridiculous things like the Fitch Fuel Catalyst, HHO systems, fuel pills and additives, as well as any other miracle device.

^ this man's a genius

i used to own a honda prelude 2.2 h22a costs just as much to drive it as a rx7 maybe a little more but not a hole lot correct tire pressure helps.. and how you drive your car if u drive the hell out of it your gunna burn the gas real fast just drive it nice

try taking some unnecessary weight out too, i think every 100 lbs is about 1 or 2 mpg, better than nothing. also dont drive like a racer when you dont need to.

Thanks guys for all your advise! I appreciate that even though it doesn't cheers me up, doe to the fact that I just have to compromise.

But there was one thing I was gonna ask, > what if somehow I could increase the temperature in a gasoline supply line ( heat it up or what ever ). The idea here is that if the gasoline will be hot or warm it'll evaporate better when it is sprayed in the combustion chamber than cold gasoline, so I am thinking if it will evaporate better then it may burn better and may give better low rpm torque, witch may increase the fuel economy.

What do you guys think of that idea? Does it makes sense or it's just stupid?

no. just no.

Gas Saving On Your Rx
 

MY DAD sugests to run the car lean but performance is going to be a little shatty but more economic, or retard the timing a little on crank angle... :icon_tup:

There is nothing that you can do with your RX-7 that will pay for itself in gas savings. That especially includes the free stuff.

Agreed agreed. The best way to save gas money is to move to south carolina. 1.29 a gal is pretty good hunh?

Please Oh Please don't run lean, unless you wanna lessen the amount of money paid for gas by not have a car to put it in >_<

That depends on your set up.

My Se with mild mods such as RB exhaust, 2nd gen leading coil, electric fan, 2nd gen trans with very tall 5th has yielded a best of 33.5 MPG.

Peejay's 12a carbureted model has yielded more than that.

The 2nd gen leading coil mod on my SE produced a 1.5 MPG increase and was verified 3 times by switching back and forth from the stock to the 2nd gen coil pack. When I went to the electric fan I gained 1 MPG.

A lot has to do with driving style also.
Increasing your tires pressures 5-7 PSI will make a difference without compromising tire wear.

As with the 4x4 world that I am a big member of, the best things you can do to help mileage have already been listed.

Tire pressure
Tune up (pugs, wires, oil - check your viscosity and run a lower level to reduce internal engine friction)
driving style
Keep your speed low (less than 65 mph)

The only point I will argue is cruise control. I have done several tests with a wide variety of vehicles and the best method I have is to keep a constant foot pressure on your pedal. That may mean going slower up hill and faster down hill, but in the end your economy can and will go up.
Case i n point: 1996 Ford Bronco with 351 (5.8 liter) engine.

Driving too and from Albany Oregon along Highway 97, 58 and I-5 (I do this trip a lot) I have seen increases as much as 3 mpg when not using cruise control. I think that this is a battle that will never see the end, but that is my stand on it.

Thanks,

Wally

one thing i do with my car can add up to 15 mpg if used whenever possible. if u have a manual (which i assume) whenever you casually get up to a good speed and u know ur gonna stop soon just press on the clutch and coast, if ur on a flat surface, you can usually make about 1/8th of a mile from 40 mph just coasting, since the engine goes to idle rpms with the clutch in, this saves a LOT of gas. my car gets around 30 mpg, but with this method, around 42 mpg. i would suggest the same with automatics but just let go of the gas. you can also do this if u know there's slower moving traffic up ahead just coast all the way up to them and apply the brake until u match their speed and coast and gas from there.:icon_tup:

Modern EFI systems completely shut off the injectors when RPMs are above around 1500 with high engine vacuum.

wouldnt it turn off then? haha i dont see how thats possible...

It's simple.

During acceleration, the engine drives the transmission, which drives the rear wheels.

During decel, and if the TPS is closed, and above say 1500 RPM, the turning rear wheels drive the transmission, which connected to the engine turns the engine.

I don't think it turns the injectors off completely when the engine is on, but when the car is in gear rolling and your foot is off the gas pedal it work at its minimal, because the vacuum in the intake manifold is like between -27 to -30 psi on my car anyways.

But if the injectors would be completely turned off it would damage the engine, I think it would cause detonation.

Minimal as in the injector duty cycle is zero, zip, nada. The injectors are not on.

You mean inHg, not psi.

minus ( - ) psi means vacuum psi

On my boost vacuum gauge it shows 27 to 30 psi of vacuum.

:icon_no2:

And I could give you a risen why I say that injectors do not turn off when you let your foot of the gas pedal while rolling in gear, what does fire in the combustion chamber then, air ?? So when you put your gas down the car just like what, reignites??

And there are many other thinks that just don't support what you say.

Injectors got to spray gas on every revolution when the engine is on, other wise it would be just like as if you run out of gas.

The injectors definitely shut off when the engine is without load. The momentum of the car keeps it going.

Vacuum is measured in inHg on your gauge, not (-) psi. One psi is about 2 inHg. The complete absence of atmospheric pressure (the limit of vacuum) is -15.4psi or about -30inHg. You will never see a number lower than 30inHg on earth, unless your gauge is broken.

^^ Thank you dgeesaman.

-CON-, I'm not making this stuff up. I have never heard from a reliable source telling me that the injectors do not shut off. I hear this from people who have actually measured injector duty cycle while under these circumstances. Heck, I've been in the car and seen data from that drive that the injector duty cycle is indeed zero during this time period. I don't claim to be a rotary god, or even a cars in general god, but I do know a little about this subject and have seen first hand that this does happen. I just don't want you to spread misinformation, especially being in the New Member section.

Have you ever ran out of gas while driving? Have you noticed that the engine only stumbles when you try giving it gas and when you let off, it is smooth until you get below 1500 again? I have run out of gas while driving my 92 Accord. I can tell you from experience that while I was in 5th gear and had my foot on the gas, accelerating slightly. Was doing about 70 at about 2500 rpm. The engine started to stumble. As soon as I let off the gas, the engine sounded normal, and the stumbling ceased. This is because the momentum of the car connected directly to the transmission was driving the engine. I kept downshifting while slowing my car towards the shoulder. Once the car had sufficiently slowed down in 2nd, the engine started bucking again.

About the psi vs inHg argument.
http://en.wikipedia.org/wiki/Orders_...tude_(pressure)

Notice that standard atmospheric pressure is 14.696 psi on an absolute scale. This should tell you right off the bat that the smallest possible pressure lower than atmospheric is nearly 0, which is roughly 14.696 psi lower than atmospheric. So arguments that claim that their machine can achieve 30 psi lower than atmospheric are downright absurd.

No. Atomization is not the issue. The fact that a rotary has a very long and inefficient combustion chamber is. And the fact that the stock ECU runs the car very rich.

Retarding timing would decrease mileage. Certainly, leaning the car out during cruise would increase mileage to a point but you reach a point of diminishing returns. At some point you will lean it out so much you need to go harder on the pedal, thus burning more fuel anyway even if the engine is leaner (follow that? :) ). For a rotary I've found the best mileage is at around 15.5 with about 32 degrees of timing.

Of course you can't apply these changes if you don't have a tunable ECU.

I call absolute horse shit on you managing 42 MPG with any rotary. It's not going to happen.

Now, if you have a long coast, your advice is valid. It is best to hold in the clutch (DO NOT PUT IT IN NEUTRAL) and just coast up to that red light. By keeping the engine at idle you will indeed save fuel. However if you are slowing down at a normal rate to stay with traffic, it is best to engine brake down to a stop as when engine braking, all fuel is cut from the engine.

All modern EFI systems (and most ancient ones) cut fuel during overrun. That means the stock L-Jetronic ECU in your RX-7 will be running zero injector duty cycle as you decel. It's called "overrun". As you decel in high vacuum with the TPS reading zero, the ECU knows you are coming to a stop and will hold the injectors closed until about 1500 RPM (or is it 1000?) at which point it will fire them again to avoid stalling the car.

However I need to point out that this is all covered in the 2nd gen FAQ.

my car with some mods and a power fc gives me about 400miles to the tank highway so i guess its not that bad 250 city it runs like a diesel truck when i floor it. my s10 pickup gave worse milage and didn't run fast.

So there you go, I learn something, I can't disagree against two. About the psi thing you guys are totally right, I checked my gauge no where there says that it is in psi.

But I still can't believe that the injectors do actually completely turn off at that point, what about the carburetors you cant turn that off, because it has an idle screw.

Also why I don't think that the injectors stop spraying fuel in those conditions is because fuel injection cars have the idle screw also, therefor the oxygen does get in to the intake system even if the throttle is closed.

According to what you are saying> Are you saying that the engine revolves on dry??

Regardless of whether you believe it or not, it is fact and not opinion. Pick up any ECU you can connect a computer to (whether it be a standalone, or an ODBII factory ECU) and watch injector duty cycle on a long decel. It drops to zero.

Carburetors are not fuel injection. They work in a totally different way. As long as the engine draws air then fuel is being delivered. Very little fuel on overrun, but fuel nonetheless. That's why carbureted vehicles tend to stink, can't handle cats very well and buck a bit on decel.

Again, what you believe is irrelevant. :)

YES! On decel, NO FUEL IS ENTERING THE ENGINE.

I hate to be wrong! But you're right about this, because I remember getting my self the electronic devise, for S4 that eliminates fuel cut off, I just never thought it actually cut the fuel off completely, and yesterday I did some tests on my actual car, so !?!

Well there is another thing I learn on this web!

I think you're referring to the FCD or Fuel Cut Defensor. It's to eliminate overboost fuel cut so you can run more then 8.6 PSI on the stock ECU. Without an FCD, all fuel to the rear rotor is cut at 8.6 PSI to prevent overboost.

There you go!! Yeah, it clips to the boost censor plug!!

But on the other hand I don't want to agree with you on this subject, I want to put this on hold until I will find some valuable facts that I could back my self up with, because it's just doesn't make sense to me, I really don't think that the injectors stop spraying fuel when on deceleration. It got to bring it at least to the idle duty cycle, because it does back fires and smoke does comes out when you decal.

I know that I don't know much about engine management system, but I'd like to learn more about it.

I wish I could show you a screen shot of my friend's computer connected to his standalone that shows the injector duty cycle being zero during long decels.

I know that it does turns injectors off in piston cars for a second or two when you frisky let go of the gas, because it has a charge already and doesn't need no more gas, that is what I been told before. But completely turned off I never heard it. So I'll do some research on this.

Yes to all of the above, plus get rid of all the extra weight in the car.

Weight kills your mileage arround town - but not that much on the highway.

I wish I kept datalogs from my tuning sessions, but I generally delete them afterwards so they don't clog up my computer. When you spend every weekend tuning EFI systems like I do, it doesn't really help to have a thousand datalogs and maps around.

Keep in mind that most people who tell you about fuel injection don't actually understand it themselves.

I don't know what more I can do to convince you. Just a Google search for "fuel cut decel", "over run fuel cut", or a read through the EFI basics over at the Megasquirt website will confirm this.

Or, just observe the O2 sensor while you do a long decel while off the pedal.

Or connect a meter with duty cycle readings to one of your primary injectors.

Or, misadjust the TPS so that the car thinks you are still on the pedal during decel and compare it to a properly adjusted TPS.

Or connect a simple LED in parallel with one of your primaries and mount it on the dash.

Jesus, why is everybody tryin to convince this guy?? its his problem he doesnt believe everyone and like Aaron said its all in the FAQ so pretty much all you guys are wasting your time. let him believe what he wants, im not trying to be an ass but theres like 15 posts trying to get this guy to believe what is fact

Hahahahahahaha!!!:)

Who gives a f...k??

I believe you guys and respect your opinions and you research, just wanna do a research for my self as well!! It's interesting shit, and think of other people who will read this learn as well!!

This massage is specifically for those people who said that injectors turn off when the car coasts in gear!

So here, I am not going to say that I read or heard someone saying, but I my self tested just today on the 1987 Mazda RX-7, with stand along Rtek7 management system from the test I will say that the injectors DO NOT turn off when the car coasts in gear or at any time when the engine is on!

Now you can say that I tested it wrong or you can say that my friends car is broken or you can say that the people who build Rtek7 did it wrong, or you can say whatever you want now!!

Also I'm not gonna say that you guys are wrong, maybe there are cars that have their injectors turn off when coasting in gear, because a lot of you do say that and I my self was almost convinced by that. I don't know, but one thing I do know that this particular car/management system does not turn off the injectors when costing in gear, and I will not stop there I want to do more tests on the other rx7's, on the stock systems as well, I would test my voltage signal/pulls today on my cars primary injectors if it wouldn't be minus 30 Celsius outside, one thing I learn on here that I got to watch what I say around here because it may come back and bite me on my ass, for the next time when I say something I'll try not to look like a fool in front of those who does his research on encyclopedia.com.

How I tested it?> I read the voltage supply/pulls to the primary injectors of the palm pilot that was communicated with ECU, we were driving for half hour, wasted 1/4 of a tank of gas and not even for a one split second it would say that the primary injectors are at zero volts/pulls or OFF as it was saying on the secondary injectors, the voltage/pulls would decrease variably as you would coast the car in gear and bring the rpm down. But never zero it would always show a number. But fuel ratio gauge would actually read lean. So here do your own judgment.

Did any of you guys actually tested it your self.
Please let me hear your experience!!

well according to the add below my post at this time "econo aid!" get more power use less fuel. lol

Something is wrong with you car or the RTek. Maybe one of the people involved with that project will chime in.

I must point out that an RTek is not a standalone. It's a programmable stock ECU.

I can't believe I'm even still involving myself with this, but clearly there is something wrong with your testing methodology. I've realized now that whether you believe the injectors cut or not is irrelevant.

You drove for half an hour and used 1/4 tank of fuel? There is clearly something wrong with that car. My bridgeport gets better fuel economy. I suspect that the RTek is not giving actual duty cycle numbers, but only those it pulls from the map at that load point. If you were to put a duty cycle meter on the actual injectors, and the car is working properly, then you will see the duty cycle fall to zero.

Note that you will not get decel fuel cut if your TPS is not adjusted properly or unplugged.

I would happily fully demonstrate decel fuel cut in my car and post the video here, but there's 12 inches of snow on the ground and it's in storage.

This will be my last post on the subject. I need to pick my battles, and clearly I've picked the wrong one. :)

just a thought... im not sure but can you buy an MSD box for an rx7... i have one on my monster miata ...gives you 7 x the spark for a better combustion... i just don't know if you can get them for a rotary engine...worth looking into tho

-6al box. its been debated and beaten to death on how it compairs.


but in short, yes you can.