Help point me in the right direction for my poor MPG
Don't believe a word he says, and for the love of god don't let him touch your car.
07-10-12, 10:04 AM
#56
Even with a piston driven car, higher octane gas will burn faster
I know this because I've put 93 octane in my nissan 200sx seR to see if it made it faster, couldnt feel a difference according to butt dyno, but according to my gas mileage, im pretty sure it was burning through it much faster.
07-10-12, 10:10 AM
#57
Just to be clear, so no one is confused by your use of "burns faster";
Higher octane is more difficult to ignite, and if anything burns slower. You experienced decreased mpg because you weren't burning all the fuel that was injected and were most likely making less power because of it.
Higher octane is more difficult to ignite, and if anything burns slower. You experienced decreased mpg because you weren't burning all the fuel that was injected and were most likely making less power because of it.
07-10-12, 10:16 AM
#58
Just to be clear, so no one is confused by your use of "burns faster";
Higher octane is more difficult to ignite, and if anything burns slower. You experienced decreased mpg because you weren't burning all the fuel that was injected and were most likely making less power because of it.
Higher octane is more difficult to ignite, and if anything burns slower. You experienced decreased mpg because you weren't burning all the fuel that was injected and were most likely making less power because of it.
I guess it does burn slower, that's why turbo engines like it running high boost (prevents detonation)....but would a high compression n/a engine need it too (i didnt think detonation was an issue on n/a)Still unsure after you saying that why certain setups get more hp running higher octane fuel? Im a bit confused
My 200sx Ser is already running pig rich because it's probably in limp mode since the check engine light is on, I still manage to get 28+ mpg in the city and like 38+ on the highway, this is when i'm shifting 4k or less normally (redline starts at 7k)
When i do floor it though my gas mileage is garbage, and the power really isnt that great even though i've got a full exhaust as well as an intake (i'm guessing because of my check engine light being on)
Reason for it being on , at least one reason I know of is because my rear o2 sensor isnt hooked up, the previous owner chopped the harness and I've yet to find where the wires are >.<
I've looked under the car and found nothing, really need to trace it and just bypass it somehow, then hopefully the check engine light will shut off, if not its something to do with my emissions system, who knows...as long as im getting 30-40 mpg i dont really care .
07-10-12, 02:55 PM
#59
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costly, but the only thing I could do to finally fix my 88gxl's poor mileage. New water and air temp sensors. I also did a homemade version of the HKS circle earth using cheap ebay knock off and HKS instructions.
07-10-12, 05:40 PM
#60
I'm seeing 450kms on a tank and that's 90% high way driving at 60-70mph. That's about 15mpg highway. Albeit this is my first manual (I've done 500ish kms in total) so it's obviously affecting my gas mileage. I'm hoping my car will get 20's when I get used to it. -.- Gas where I live is 1.26 a liter, or 4.76 a gallon for you Americans and where I'm moving for college it's 1.40 a liter or 5.30 a gallon. Gas is expensive in Northern Ontario and that's for 87 octane! My car is a '91 N/A with 96,000kms/60,000 miles has a cat-back exhaust and an HKS cone filter.
07-10-12, 06:59 PM
#61
I'm seeing 450kms on a tank and that's 90% high way driving at 60-70mph. That's about 15mpg highway. Albeit this is my first manual (I've done 500ish kms in total) so it's obviously affecting my gas mileage. I'm hoping my car will get 20's when I get used to it. -.- Gas where I live is 1.26 a liter, or 4.76 a gallon for you Americans and where I'm moving for college it's 1.40 a liter or 5.30 a gallon. Gas is expensive in Northern Ontario and that's for 87 octane! My car is a '91 N/A with 96,000kms/60,000 miles has a cat-back exhaust and an HKS cone filter.
07-14-12, 04:49 PM
#63
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I'm seeing 450kms on a tank and that's 90% high way driving at 60-70mph. That's about 15mpg highway. Albeit this is my first manual (I've done 500ish kms in total) so it's obviously affecting my gas mileage. I'm hoping my car will get 20's when I get used to it. -.- Gas where I live is 1.26 a liter, or 4.76 a gallon for you Americans and where I'm moving for college it's 1.40 a liter or 5.30 a gallon. Gas is expensive in Northern Ontario and that's for 87 octane! My car is a '91 N/A with 96,000kms/60,000 miles has a cat-back exhaust and an HKS cone filter.
07-15-12, 02:42 PM
#64
OK, this car's gotten BAD. It WON'T start with out a fuel pump cut switch, ever, unless it's sat over night. But keep reading, I think I've solved the problem!
For the hell of it, I disconnected the water thermosensor, and drove around. FSM says the ECU defaults to 176F (operating) w/ no input from this sensor. I no longer needed the cut switch!
Took the car on a 150 mile trip w/ my gf (actually, it's her car) to a state park. before leaving, we filled up & calculated the milage.. it was 12.3... fuuuuuckk that's awful. OK, let's see how it does now! So we take off, pure highway driving, to the park. Total distance covered was 149.1 miles. We averaged about 85 (kept the revs right around 3500, but under to keep secondaries off) the whole time. Drive was with windows down the entire time, & a good bit of WOT driving.
When we returned, we filled up again... It only took ~6 some to fill up. Divided it out, 22.93 MPG! Keep in mind the ONLY thing different is that I disconnected the thermosensor. I even back probed the ECU TWICE to see if I was getting proper voltage, and was!
I guess now I'm going to probe the sensor itself & check it's resistance per FSM, and just go from there. But I'd have to say this is fixed, & that I feel quite dumb overlooking it after all this time
For the hell of it, I disconnected the water thermosensor, and drove around. FSM says the ECU defaults to 176F (operating) w/ no input from this sensor. I no longer needed the cut switch!
Took the car on a 150 mile trip w/ my gf (actually, it's her car) to a state park. before leaving, we filled up & calculated the milage.. it was 12.3... fuuuuuckk that's awful. OK, let's see how it does now! So we take off, pure highway driving, to the park. Total distance covered was 149.1 miles. We averaged about 85 (kept the revs right around 3500, but under to keep secondaries off) the whole time. Drive was with windows down the entire time, & a good bit of WOT driving.
When we returned, we filled up again... It only took ~6 some to fill up. Divided it out, 22.93 MPG! Keep in mind the ONLY thing different is that I disconnected the thermosensor. I even back probed the ECU TWICE to see if I was getting proper voltage, and was!
I guess now I'm going to probe the sensor itself & check it's resistance per FSM, and just go from there. But I'd have to say this is fixed, & that I feel quite dumb overlooking it after all this time
07-30-12, 10:39 PM
#66
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Sort of reviving an old thread, but i was really proud to see the car made it to 306 miles on this tank. I dont think I've ever gotten that high on any tank in any car I've driven.
http://www.flickr.com/photos/globekidd/7681621522/http://www.flickr.com/photos/globekidd/7681621522/ by http://www.flickr.com/people/globekidd/, on Flickr
http://www.flickr.com/photos/globekidd/7681621522/http://www.flickr.com/photos/globekidd/7681621522/ by http://www.flickr.com/people/globekidd/, on Flickr
07-31-12, 12:24 AM
#67
Driving RX7's since 1979
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Sort of reviving an old thread, but i was really proud to see the car made it to 306 miles on this tank. I dont think I've ever gotten that high on any tank in any car I've driven.
300 mile tank by Daulton G. Photography, on Flickr
300 mile tank by Daulton G. Photography, on Flickr
What size are your rear tires?
Are you running a stock transmission and differential?
Ever checked the speed your speedo indicates compared to the speed a GPS "location" indicates?
07-31-12, 09:20 AM
#68
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205/60-15
Stock and stock
Yes, took a couple hour trip up north months back in this car and the milage matched up between the trip odometer and the gps.
Ps. I'm now at 320 miles but its reading E and no fuel light. I'm capping it there though and filling up.
Stock and stock
Yes, took a couple hour trip up north months back in this car and the milage matched up between the trip odometer and the gps.
Ps. I'm now at 320 miles but its reading E and no fuel light. I'm capping it there though and filling up.
Last edited by REAmemiya_fan; 07-31-12 at 09:22 AM.
02-17-14, 08:36 PM
#69
BUMP!!! Wanted to update this, as I can almost say w/ zero uncertanty that I've solved the problem.
As stated, I:
-Confirmed fuel pressure was within spec
-changed the following w/ other "in spec" parts: MAF, CAS, plugs, coils, fuel pump, ECU, PS computer (hey, I was grabbing at straws!! & trying to fix intermitent PS issues)
-checked rigourously for vac leaks (none)
-confirmed closed loop operation of O2 sensor
-reinstalled all emissions equip, minus cats.
-checked compression w/ a mazda tester, over 115 psi on all faces
STILL could not bump over 12-13 city w/ my wife driving it, & around 15.5-16 highway. Thats filling the tank, driving to fill up, & doing miles driven/gallons.
Fast forward nearly 2 yhears til now. She daily drives the car, & we both just kinda left it as is, since it does run well. We just dealt with the fact that it
-got crappy milage
-shuddered slightly on acceleration
-started up VERY fast, on cold. Like, a 1/2 second of engine cranking
-was very bogged down & labored launching from a stand still
Well, in building a megasquirt controlled T2 vert, I learned THIS: https://www.rx7club.com/2nd-generati...ferent-973214/
Apparently timing marks vary one pulley to another. ****!! I'm about to put 15# boost thru this engine (S4 JDM motor I found at a junkyard, & I left the orig pulley at the yard as I damaged it during removal of the front pulley bolt to tear down engine for inspection). I swapped pulleys saturday w/ another car here that had an RB one on it, & decided to re-time the car that HAD the RB pulley, and now had, what should've been, a matching S5 pulley to it's S5 engine. Well it ran like ***. I got home, & retimed it back to where I had it, with the CAS lock stud about 1/3 the way up the adjustment slot. Issues gone.
It THEN DAWNED ON ME>>> Oh man, what is Rebecca's RX7 (subject of this entire thread) timed to?? Perhaps it's pulley is the wrong one too??? It has similar issues to what I just induced on my car by re-timing to the pulley that didn't match the engine from the factory...
I check, sure as ****, it's bottomed out on the far left side of the slot. Broke the nut loose, moved it so it was 1/3 the way over, tightened, went for a drive.
-Started up NORMAL compared to all the other 7's I have (23 ATM, much experience w/ these cars, etc)
-Did not shutter AT ALL during slow accel
-NO MORE backfiring
-smooth, much less labored, low end accel.
There only thing that's yet to be tested is hard data on the MPG's. I'll chime back in after a few weeks have gone by to say what it was.
So ANYWAY, I'm feeling very confident with calling this issue fixed & done.
TL;DR:
-IF YOU'VE CHECKED THE TIMING W/ A LIGHT, AND IT'S GOOD, DOUBLE CHECK THAT THE CAS LOCK STUD IS 1/3 IN THE SLOT OF THE CAS. THIS COULD VERY WELL BE YOUR ISSUE. IT'S RIGHT INFRONT OF YOUR EYES, BUT IF YOU DON'T KNOW, SOOOO EASY TO OVERLOOK.
As stated, I:
-Confirmed fuel pressure was within spec
-changed the following w/ other "in spec" parts: MAF, CAS, plugs, coils, fuel pump, ECU, PS computer (hey, I was grabbing at straws!! & trying to fix intermitent PS issues)
-checked rigourously for vac leaks (none)
-confirmed closed loop operation of O2 sensor
-reinstalled all emissions equip, minus cats.
-checked compression w/ a mazda tester, over 115 psi on all faces
STILL could not bump over 12-13 city w/ my wife driving it, & around 15.5-16 highway. Thats filling the tank, driving to fill up, & doing miles driven/gallons.
Fast forward nearly 2 yhears til now. She daily drives the car, & we both just kinda left it as is, since it does run well. We just dealt with the fact that it
-got crappy milage
-shuddered slightly on acceleration
-started up VERY fast, on cold. Like, a 1/2 second of engine cranking
-was very bogged down & labored launching from a stand still
Well, in building a megasquirt controlled T2 vert, I learned THIS: https://www.rx7club.com/2nd-generati...ferent-973214/
Apparently timing marks vary one pulley to another. ****!! I'm about to put 15# boost thru this engine (S4 JDM motor I found at a junkyard, & I left the orig pulley at the yard as I damaged it during removal of the front pulley bolt to tear down engine for inspection). I swapped pulleys saturday w/ another car here that had an RB one on it, & decided to re-time the car that HAD the RB pulley, and now had, what should've been, a matching S5 pulley to it's S5 engine. Well it ran like ***. I got home, & retimed it back to where I had it, with the CAS lock stud about 1/3 the way up the adjustment slot. Issues gone.
It THEN DAWNED ON ME>>> Oh man, what is Rebecca's RX7 (subject of this entire thread) timed to?? Perhaps it's pulley is the wrong one too??? It has similar issues to what I just induced on my car by re-timing to the pulley that didn't match the engine from the factory...
I check, sure as ****, it's bottomed out on the far left side of the slot. Broke the nut loose, moved it so it was 1/3 the way over, tightened, went for a drive.
-Started up NORMAL compared to all the other 7's I have (23 ATM, much experience w/ these cars, etc)
-Did not shutter AT ALL during slow accel
-NO MORE backfiring
-smooth, much less labored, low end accel.
There only thing that's yet to be tested is hard data on the MPG's. I'll chime back in after a few weeks have gone by to say what it was.
So ANYWAY, I'm feeling very confident with calling this issue fixed & done.
TL;DR:
-IF YOU'VE CHECKED THE TIMING W/ A LIGHT, AND IT'S GOOD, DOUBLE CHECK THAT THE CAS LOCK STUD IS 1/3 IN THE SLOT OF THE CAS. THIS COULD VERY WELL BE YOUR ISSUE. IT'S RIGHT INFRONT OF YOUR EYES, BUT IF YOU DON'T KNOW, SOOOO EASY TO OVERLOOK.
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