tips on how to raise mpg?
04-06-05, 06:05 AM
#1
I "lost" my emissions....
Thread Starter
tips on how to raise mpg?
if anyone has any good tips please post, im getting like 15 mpg and i know i should be getting like 24. thx
04-06-05, 06:59 AM
#3
always modding
Join Date: Mar 2005
Location: on a tiny island in the middle of a sea
Posts: 1,667
Likes: 0
Received 3 Likes
on
3 Posts
put everything back to stock
i.e remove ur performance mods..
check ur timming and tuning, check ur 2 sensor, fuel injectors, fuel filter etc..
oh and if ur a turbo rotory.. don't let the boost gauge ever leave "VAC" :P
i.e remove ur performance mods..
check ur timming and tuning, check ur 2 sensor, fuel injectors, fuel filter etc..
oh and if ur a turbo rotory.. don't let the boost gauge ever leave "VAC" :P
04-06-05, 07:45 AM
#7
Jesus is the Messiah
Everyone who gave advice so far sucks except for the guy who said "O2 Sensor" :-p
I say
0) Keep it under 3800RPM, and dont accelerate so hard! 24 is highway MPG for a stock RX-7, not city.
1) Plugs
2) Wires (Check the resistence before replacing)
2) O2 Sensor (Just replace it, they're $7 from Olympic)
4) Check the sensors per FSM: TPS, MAP, MAF.
12) Hows your alignment?
-6) Clean your injectors!
e) Get a free(er) flowing exhaust, port your intake for velocity instead of CFM. Don't wire open your 6pi.
Pi) Get an aftermarket EMS and tune it to run lean except under boost.
My 'vert gets 28MPG
I say
0) Keep it under 3800RPM, and dont accelerate so hard! 24 is highway MPG for a stock RX-7, not city.
1) Plugs
2) Wires (Check the resistence before replacing)
2) O2 Sensor (Just replace it, they're $7 from Olympic)
4) Check the sensors per FSM: TPS, MAP, MAF.
12) Hows your alignment?
-6) Clean your injectors!
e) Get a free(er) flowing exhaust, port your intake for velocity instead of CFM. Don't wire open your 6pi.
Pi) Get an aftermarket EMS and tune it to run lean except under boost.
My 'vert gets 28MPG
Last edited by Tofuball; 04-06-05 at 07:47 AM.
Trending Topics
04-06-05, 08:14 AM
#8
It's only Rock and Roll
iTrader: (1)
Join Date: Sep 2004
Location: In a house...
Posts: 2,509
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Tofuball
Everyone who gave advice so far sucks except for the guy who said "O2 Sensor" :-p
I say
0) Keep it under 3800RPM, and dont accelerate so hard! 24 is highway MPG for a stock RX-7, not city.
1) Plugs
2) Wires (Check the resistence before replacing)
2) O2 Sensor (Just replace it, they're $7 from Olympic)
4) Check the sensors per FSM: TPS, MAP, MAF.
12) Hows your alignment?
-6) Clean your injectors!
e) Get a free(er) flowing exhaust, port your intake for velocity instead of CFM. Don't wire open your 6pi.
Pi) Get an aftermarket EMS and tune it to run lean except under boost.
My 'vert gets 28MPG
I say
0) Keep it under 3800RPM, and dont accelerate so hard! 24 is highway MPG for a stock RX-7, not city.
1) Plugs
2) Wires (Check the resistence before replacing)
2) O2 Sensor (Just replace it, they're $7 from Olympic)
4) Check the sensors per FSM: TPS, MAP, MAF.
12) Hows your alignment?
-6) Clean your injectors!
e) Get a free(er) flowing exhaust, port your intake for velocity instead of CFM. Don't wire open your 6pi.
Pi) Get an aftermarket EMS and tune it to run lean except under boost.
My 'vert gets 28MPG
04-06-05, 08:21 AM
#9
Jesus is the Messiah
Number -6 has been a major problem in a lot of RX-7s that I have worked on. As you've said, it caused problems starting, especially within a few hours of when it has been run before. So, besides leaking fuel when the car isnt even running, it leaks while you're driving as well. Really really leaky injectors can very much impact your fuel economy. I was getting something like 11MPG on my Acura Legend when it had leaky injectors. Bad stuff!
04-06-05, 09:01 AM
#13
It's only Rock and Roll
iTrader: (1)
Join Date: Sep 2004
Location: In a house...
Posts: 2,509
Likes: 0
Received 0 Likes
on
0 Posts
He just got it, stock 86 NA champagne (sp?) w/no sunroof. It was flooding real bad the other night when he was trying to start it after sitting for a couple of hours. Pulled the fuses and tried that a few times then decided to push start him, smoked a bit afterwards. I know he's put new plugs in it so maybe a 60k tuneup and 2, 2, 4, -6....?
04-06-05, 09:51 AM
#15
vac leak
Join Date: Aug 2003
Location: Rutgers
Posts: 1,247
Likes: 0
Received 0 Likes
on
0 Posts
if he was having flooding issues after letting it idle for a couple of hours then wouldnt that suggest a hot start problem?...the injectors could be leaking.......and that could also be part of the season why its getting such shitty milage
04-06-05, 01:29 PM
#18
Eats, Sleeps, Dreams Rotary
iTrader: (1)
Join Date: Jun 2001
Location: London, Ontario, Canada
Posts: 3,106
Likes: 0
Received 0 Likes
on
0 Posts
This question has been asked a lot of times, but I'll add a few things that make the biggest difference, if your car is operating correctly. In no particular order:
1. Cone air filter. You can achieve measurably better millage. They're pretty affordable already, but will pay for themselves fairly quickly.
2. Inflate the tires as was mentioned above. Don't do the maximum for the tires, but you can certainly be running mid-high 30s psi.
3. Get a cheap A/F gauge. This helps you ensure that you are driving the car properly and in closed loop.
4. Drive for millage. Particularly on the highway you can fairly painlessly get better millage. Lowering the revs to stay in closed loop (eg. driving slower) and lowering them closer to 3k will improve your millage a LOT. Track your millage and pay attention to what stratagies work.
5. Draft trucks on the highway. You can gain 5-10%.
1. Cone air filter. You can achieve measurably better millage. They're pretty affordable already, but will pay for themselves fairly quickly.
2. Inflate the tires as was mentioned above. Don't do the maximum for the tires, but you can certainly be running mid-high 30s psi.
3. Get a cheap A/F gauge. This helps you ensure that you are driving the car properly and in closed loop.
4. Drive for millage. Particularly on the highway you can fairly painlessly get better millage. Lowering the revs to stay in closed loop (eg. driving slower) and lowering them closer to 3k will improve your millage a LOT. Track your millage and pay attention to what stratagies work.
5. Draft trucks on the highway. You can gain 5-10%.
04-06-05, 01:46 PM
#20
RPM's cost money, my old vw had a shift light and the damn thing was always lit! I tried following it's suggestion for a whole tank and my city mileage went up about 20%. It took too much self control to keep the revs below 3k so I gave up. EVERY bit of maintenance suggested above will help too as does free flowing exhaust.
04-06-05, 02:34 PM
#22
If you're paying attention, an RX-7 can outstop a semi without even trying.
Things I've learned about the nits & grits of fuel economy on my '7 (88 SE, NA, more or less stock):
The O2 sensor will go bad and not throw a code. If it's cycling slowly, the ECU will still follow it's suggestions, but will get worse economy due to the slow readings. If it's REALLY bad, it will throw a code, but as long as it cycles at all, the ECU will listen to it.
Closed loop mode on the highway is very easy to break out of. I spent a several hundred mile trip with a LED attached to the "O2 sensor test connector" up with the engine diagnostic connector, and learned some interesting things:
Closed loop mode only exists up to 3500 RPM. Anything above that, and it will be in open loop mode. This works out to 85mph or so on mine. Cruise above this, fuel economy WILL suck.
Closed loop mode is *very* easy to break out of with excess pedal pressure. When going up a hill, press the gas pedal like there's an egg between your foot & the pedal - it might stay in closed loop mode. If you jab at it like is fun to do with a '7, it will drop out of closed loop mode and suck significantly more fuel.
At least on mine, the O2 sensor seems to take a while to warm up.
As for other fuel economy things, it's been pretty well covered. Interestingly enough, performance mods often improve fuel economy, IF YOU STAY OUT OF THE THROTTLE. Freer flowing intake & exhaust means less pumping loss. General maintenance is also good - plugs, wires, injector cleaning (as in, take them out and have them cleaned), tire pressure.
Your transmission fluid, engine oil, and differential fluid will make a slight difference. Slippery synthetics will let things spin with less resistance than ancient dino oil. Less power loss in the drivetrain, better fuel economy (and more usable power).
Finally, if you don't have any catalytic converters to babysit, you can lean things out on the highway significantly with a SAFC or standalone. If you're using a SAFC, closed loop mode will still take over and adjust things to where it feels proper (14.7:1 or so). However, leaning it out in the cruise band will still help somewhat, due to the fact that it is easy to drop out of closed loop mode, and leaning it out will reduce fuel consumption up hills & such.
The real trick to leaning it out on the highway is to actually not let it use closed loop mode at all - disconnect the O2 sensor (and replace it with your favorite wideband sensor). The ECU can't go into a feedback loop, so it's just using maps. The SAFC modifies these maps nicely. There's also no real risk of detonation when under light load on the highway, so you can lean the engine out until it starts to surge, then richen it up slightly. I believe a lot of people cruise in the 16:1 or 16.5:1 range with standalones and have no problems. You'll fry a cat in short order with the higher EGTs from this though.
And, last, an ignition system upgrade may help some. That MSD6A will be firing multiple hotter sparks up until 3500 RPM or so, giving better combustion.
There's no "instant fix" for fuel economy, but you can do a bunch. I'm actually starting the process of making my '7 a fuel sipper (hah!) due to the long commutes I make (and the fact that my '7 is the only car I have with AC). I'll post updates as I figure stuff out.
Oh, and even with all this stuff, don't expect much above 10-12mpg when driving it hard. Power takes gas. Though, if you have a NA, leaning things out throughout the RPM range may help decrease fuel consumption & increase power - the stock ECU runs stupidly rich under load.
-=Russ=-
Things I've learned about the nits & grits of fuel economy on my '7 (88 SE, NA, more or less stock):
The O2 sensor will go bad and not throw a code. If it's cycling slowly, the ECU will still follow it's suggestions, but will get worse economy due to the slow readings. If it's REALLY bad, it will throw a code, but as long as it cycles at all, the ECU will listen to it.
Closed loop mode on the highway is very easy to break out of. I spent a several hundred mile trip with a LED attached to the "O2 sensor test connector" up with the engine diagnostic connector, and learned some interesting things:
Closed loop mode only exists up to 3500 RPM. Anything above that, and it will be in open loop mode. This works out to 85mph or so on mine. Cruise above this, fuel economy WILL suck.
Closed loop mode is *very* easy to break out of with excess pedal pressure. When going up a hill, press the gas pedal like there's an egg between your foot & the pedal - it might stay in closed loop mode. If you jab at it like is fun to do with a '7, it will drop out of closed loop mode and suck significantly more fuel.
At least on mine, the O2 sensor seems to take a while to warm up.
As for other fuel economy things, it's been pretty well covered. Interestingly enough, performance mods often improve fuel economy, IF YOU STAY OUT OF THE THROTTLE. Freer flowing intake & exhaust means less pumping loss. General maintenance is also good - plugs, wires, injector cleaning (as in, take them out and have them cleaned), tire pressure.
Your transmission fluid, engine oil, and differential fluid will make a slight difference. Slippery synthetics will let things spin with less resistance than ancient dino oil. Less power loss in the drivetrain, better fuel economy (and more usable power).
Finally, if you don't have any catalytic converters to babysit, you can lean things out on the highway significantly with a SAFC or standalone. If you're using a SAFC, closed loop mode will still take over and adjust things to where it feels proper (14.7:1 or so). However, leaning it out in the cruise band will still help somewhat, due to the fact that it is easy to drop out of closed loop mode, and leaning it out will reduce fuel consumption up hills & such.
The real trick to leaning it out on the highway is to actually not let it use closed loop mode at all - disconnect the O2 sensor (and replace it with your favorite wideband sensor). The ECU can't go into a feedback loop, so it's just using maps. The SAFC modifies these maps nicely. There's also no real risk of detonation when under light load on the highway, so you can lean the engine out until it starts to surge, then richen it up slightly. I believe a lot of people cruise in the 16:1 or 16.5:1 range with standalones and have no problems. You'll fry a cat in short order with the higher EGTs from this though.
And, last, an ignition system upgrade may help some. That MSD6A will be firing multiple hotter sparks up until 3500 RPM or so, giving better combustion.
There's no "instant fix" for fuel economy, but you can do a bunch. I'm actually starting the process of making my '7 a fuel sipper (hah!) due to the long commutes I make (and the fact that my '7 is the only car I have with AC). I'll post updates as I figure stuff out.
Oh, and even with all this stuff, don't expect much above 10-12mpg when driving it hard. Power takes gas. Though, if you have a NA, leaning things out throughout the RPM range may help decrease fuel consumption & increase power - the stock ECU runs stupidly rich under load.
-=Russ=-
04-06-05, 04:12 PM
#24
Lives on the Forum
Umm, don't drive the car in the city...
I (along with a couple of other people here) have noticed that if you try to keep the revs down (especially during cruise), you will actually get worse mileage. In other words, cruising at 80 mph in 5th actually nets better gas mileage than cruising at 70 in 5th. Strange but true. I do believe it's because of the "flywheel" properties of a spinning rotary engine.
Since I've driven the same 50 mile stretch of highway day after day to go to work over the years, I've noticed some other interesting tidbits about fuel economy also: if it's raining, gas mileage goes down (even though you slow down a bit). And, the colder the outside air temp, the worse the mileage...
I (along with a couple of other people here) have noticed that if you try to keep the revs down (especially during cruise), you will actually get worse mileage. In other words, cruising at 80 mph in 5th actually nets better gas mileage than cruising at 70 in 5th. Strange but true. I do believe it's because of the "flywheel" properties of a spinning rotary engine.
Since I've driven the same 50 mile stretch of highway day after day to go to work over the years, I've noticed some other interesting tidbits about fuel economy also: if it's raining, gas mileage goes down (even though you slow down a bit). And, the colder the outside air temp, the worse the mileage...
Last edited by WAYNE88N/A; 04-06-05 at 04:21 PM.
04-06-05, 04:19 PM
#25
Lives on the Forum
Forgot to mention:
Cone filter did nothing for my mileage.
Neither did the wide-open exhaust...
Only in WOT conditions do they help...
Only thing I've found that actually increases my mileage (which has averaged 26-27 mpg or so ever since I bought the car stock back in '99) is to use a premix ratio in the 80:1 range. Only thing wrong with those ratios, though, is the excessive blowby into the oil system. Oh well, as Rush likes to say, "you don't get something for nothing".
Cone filter did nothing for my mileage.
Neither did the wide-open exhaust...
Only in WOT conditions do they help...
Only thing I've found that actually increases my mileage (which has averaged 26-27 mpg or so ever since I bought the car stock back in '99) is to use a premix ratio in the 80:1 range. Only thing wrong with those ratios, though, is the excessive blowby into the oil system. Oh well, as Rush likes to say, "you don't get something for nothing".