chrisnewton

Yes, first post, I know...but I've been reading here for a while, and strongly considering buying an RX-8 in the near future. Anyways, today, while researching the 8, I found this article:

http://www.rxtuner.com/farticles/Can...dExplained.pdf

Anyways, in that article, I noted a few interesting things which I havent seen generally discussed in its own thread (yes, I'm sure there have been posts related to this buried deep in other posts about HP or MPG)

- One rx-8 was making more HP stock then another
- Variances in MAF voltage noted
- .15 volt difference on the 4 volt MAF sensor is the difference in 20HP or 1 (their claim)
- 1/3 of RX-8s were significantly varied from the other 2/3rds of the RX-8s


So, I'm wondering if the stat of 1/3 of RX-8s they saw which had weird MAF voltages, lines up with the number of RX-8s that see horrible mileage of 12 mpg?

Also, wondering if this could be one of the symptoms of poor dyno readings?


Has anyone gone and recorded maf voltages and done any correlation that might explain cars that have very poor mileage?

Chris

zoom44

yes. i collected maf voltages fom 20 or so people and the maf variance is significantly less than that. 1 out of the 20 was considerably different. but the small differences between the otherswere all seen at like 7k rpm. hardly where you would be for mpg.

so i would say no to both of your questions.

12 mpg people are a combination of problems some are driver some are car. until each person claiming this low mpg allows testing by the dealership or a 3rd party then no one can be certain. but my advice is get it done even if you have to pay.

dyno results are dyno results. if you dont like the results try a diffeent one. your results might improve. some charts can reveal an issue with ports or rpm pickup. but a clean chart with 170 hp to 200 hp is normal depending on type of dyno.

Glyphon

example on how much driver effects fuel economy. i bought my car used. my first tank on it, i got 23.5 mpg. since then my average fuel economy is 18.520 mpg. the previous owner is a member of this site also. she mentioned to me once that she never got the car above 16mpg. i don't think i've had a tank below 16mpg. we live in roughly the same area, so we have the same climate, same terrain, same traffic. major significant difference...the driver.

RotaryNoob

So you drive like a grandpa and she drove like a madwoman... Makes sense.

alcimedes

Can I get her number? :D

Glyphon

don't drive like a grandpa. try again. :p
driving like that is bad for the engine...doesn't get rid of any carbon deposits. my car gets redlined at least once a day, and many times more.

Astral

Amen! Words to live by!

icyur2

I drive it mostly in city, changing shift @3750-3500RPM and get 20MPG. This is from using 91 octane..since I only have 900 Miles on mine, I'm not redlining until I'm at least 1500 Miles on it..break-in period.

Off the subject, but do anyone know how many gallons is left when you get that lovely fuel light engaged? The stupid manual don't tell you, besides recommending that you don't let it fall below 1/4 tank..how useful is that???

zoom44

read this thread titled 'when does your gas light turn on' https://www.rx8club.com/series-i-tech-garage-22/when-does-your-gas-light-come-69007/

r0tor

iTrader: (1)

Simple cruising, the PCM uses feedback from the O2 sensor to ajust the a/f ratio to stoich - so if your MAF was reading high, the PCM would look at its table and add a certain amount of fuel (which would be too much), but would then look at the O2 sensor and see its too rich so it would cut back on the fuel till it reaches stoich and store that cutback needed into the long term fuel trim so next time it shouldn't have to readjust.