Wing

3750RPM :D After that all 3 injectors are on!

eccles

I just filled up again, having used 3/4 of a tank with the DSC and TC turned completely off the whole time. The gas mileage was indistinguishable from that which I've been seeing all along: 15.5mpg.

RX-8 2004

I have 1200 miles on my car and on the avg. with getting on the throttle occassionally. I am getting 22.471 mpg with the DSC & TSC ON. Mostly city driving with a few Hwy. I have not tried it yet with it all off.

neit_jnf

Actually, the injectors work at the same intervals as the ports. 2 injectors (1 for each rotor) up to 3750 which is when the secondary ports open and the secondary injectors come into play. So that's 4 injectors until 6250 when the auxilliary ports and extra injectors are activated.

idle - 3750rpm 2 inj
3750 - 6250rpm 4 inj
6250 - fuel cutoff 6 inj

Remember that the standard power engine only has 4 ports and 4 injectors.

LTAGFERN

Sport Package M/T, Sunlight Silver, 1950 miles

Very interesting posts within this 'thread'. I also have begun driving with the DSC/TCS "off", disabling the 'system' during the short idle before driving. Disabling isn't a 'habit' yet, but I almost always remember to turn it 'off' before driving away.

All things considered, there are many variables which will affect my mileage. However, I refilled my tank (6.25 gallons) this morning to check MPG after driving 138 miles with DSC/TCS 'off', and . . I DID get the 'highest' MPG I've ever gotten. A bit less than 22 MPG . . . which is not great, but higher than the roughly average 19.5 MPG I HAVE been getting.

I seem to be getting slightly better MPG using Shell, and I'm now using Shell 89 octane 'mid-grade'. This MAY help MPG a bit, but also may be that sales hype is affecting my mind. And because we are nearing the Fall season, I've been using less A/C (more open window). This probably helps MPG. And because the engine torque is relatively flat, I've been shifting more within the 2K - 3K RPM range instead of the 4K + range. (Doesn't seem to be necessary to accelerate in order to get into the 'torque range' like in a piston engine.) And, the outside air temperatures are cooler, which ALWAYS benefitted my relatively underpowered Dodge Stratus.

However, I have become more familiar and comfortable with my '8', and am driving with more assertiveness than I had been during the first 1K + miles. There DOES seem to be more available power and my car seems to have more . . . zip. Whether this is because of DSC/TCS being 'off', or having to do with 'break-in' of engine and associated parts, or having something to do with programmed 'mapping' changes, I don't know.

The bottom line. For whatever reasons, I've experienced better gas mileage and what feels like slightly more power during my obviously very short trial period of driving with DSC/TCS 'off'. The window sticker from my car states "highway MPG . . 24". I'll continue driving with DSC/TCS 'off' . . hoping . . I may achieve that 24 MPG some day in my '8'.

U. N. O.

i just don't see the co-relation btw. milage/ dcs, tcs systems. Granted that dcs uses the brakes (and throtle/timing?) it would not affect the avg. mialege so much, from 17 to 21+ ... as far as power goes, it is all psycological, other wise mazda would have said something about it instead of offering 'free' stuff and buy backs, as dishonest as those b****ds are, they would find anything as an excuse, and if they didn't use it is because it is not a real power problem solver.
The real thing to think about is that again you mentioned that you have 5000 miles already in the car.. does anyone else that have over 5k of miles notice a mileage change or even power change in their car?..

sorry but for someone considering a buyback, this seems a bit too easy to just "fix the problem" of both power and mpg.

canzoomer

Yup, too good to be true. Oh well.

I just finished a tankful with the DSC fully off each time I started it.

No appreciable difference. I got 16.2 liters per 100 kilometers.
Mainly city driving, easy shifting. I generally shift 1,2 the 4 or 5th gear.
I pop in the cltuch, go into neutral and idle when decellerating to lights and stuff.

Glad I sent my letter in.

R32

Just from personal experience using Shell gas, I do have a '98 Corolla, and tested during the summer their actual claims for more mpg.

Now, I drive real assertive. I jackrabbit greenlights, hit 75-80 on the freeways, etc. I don't drive a manual because I did get a 6 CD changer and driving stick doesn't make sense in So Cal traffic.

Now, my car holds 13.2gallons. Even when I ran with Arco, Chevron, Mobil, etc., with 50/50 driving on city and highway, I've been able to get mileage between 280-330 consistently. I always push til the gas indicator lights up.

I switched to Shell with similar driving style and similar driving routes with the 50/50 driving city/highway. Now, my mileage is consistently between 320-375.

I duplicated the test over a month just for reassurance to see if Shell gas was worth the extra $0.03 more per gallon. The results are still virtually the same, and even when I do hit the 280-300 mark with Shell, the tank still indicates just under 1/4 tank of gas, compared to the Gas light flashing with other types of gas and similar mileage.

I don't work for Shell, but I do recommend exploring this option. Even the extra 20 miles per full tank is worth it.

8_wannabe

R32 (and others on this thread): I appreciate what you're saying and I'm playing around with Shell a bit to see if their claims are true. However, to add real validity to the numbers we need to be consistent in how we're measuring mileage. I'm not the first to post this, but we need occasional reminders. Running till the light comes on and seeing how many miles you went allows too much uncertainty in the precise mpg analysis.

For those who aren't doing so, here's what you do. Top off the tank (make sure it's really topped off.) Set your trip odometer to zero. Drive around, the lower you run the tank the better. Top off the tank again (make sure it's really topped off.) Note how many gallons it took on the second fillup. Divide miles on your odometer by gallons on the second fillup, that is your mpg. Report it to the forum. You should be accurate to a decimal place or so. Reset odometer to zero and repeat the process.

If we really want valid analysis of what's going on, everyone needs to remove subjectivity (like, it's half full so I got like 15 mpg.) Let's be consistent in how we're doing this. There are too many variables to start adding more of our own. :-)

R32

I appreciate the tip, but now with college starting again (already 3rd week) it's going to be a lot of 90/10 city/highway.

I'll see what I can do.

Needless to say, I was already convinced when the I hit the 260mi mark with a quarter tank. 260mi on other gas was clearly near E.

8_wannabe

I'd kill for 260 at 1/4 full. The best I've done is 240 down to the warning light, which came out to 18.1 mpg when I refilled.

f1michel

Just refilled after using 87 octane shell gaz and giving it a fair ride, using all 6 speeds all the time and shifting at 6k or just about.

14.06 L perr 100 k or 16.79 mpg. By far my worst tank and i'm at 6100 Km. Of course it was at the dealer today and they put 45KM on it testing whatever i told them wasn't right. ( cruise,AC, alignment, front brakes) all minor stuff. i'm sure the mechanic didn't shift it at 3K !

BTW, there nothing wrong with EVERYTHING i reported !!! I didn't laugh at him but told him he's probably get a service note pretty soon about all my minor complaints... i was their 1st ever RX8 to service since i was their 1st buyer and have over 6K in 5 weeks.

TJRX8

First tank (87) down with TSC/DSC off.

214Mile/12.3Gals=17.39 ! Best yet by over 1 MPG. I even forgot to turn it off a couple times and I drove the **** out of it every now and then. No grandma driving at all.

I wonder if the ECU map is messing with the DSC too, causing low mpg.

RodsterinFL

First tank (not even a complete one) with all turned off.

I had 47 miles on the tank before folllowing your advice. I just got gas last night and got 18.11 mpg in my regular town run where I was getting 16.5 mpg on the last 3 tanks prior. THis definitely makes a difference.

This is also in line with my last two cars' mileage. It is harder for us to compare mileage all driving different places and distances and of course with different conditions - some highway, some street runs, etc. My previous cars BMW 328is got 19-20 mpg and the MIllennia S 17-18 mpg on the run I refer to in the RX 8 above. THis is not that different.

SOmeting else to consider - using regular gas made mine run better (smoother) the first tank of regular I DROPPED to 14 mpg. but it quickly improved. I know I cannot MAKE any of you switch to regular gas but I cannot emphasize enough the difference it made on my engine. THe thing acted like it was choking before on 91. Like it was bogged down all the time. Then with regular it was as if it became free rolling (emergency brake off!!!) I keep reading where people used regular and their engines would barely run or started knocking hard, etc. I have a difficult time with that with all having the same engine and all.

ALso. according to the tech info on our engine, we only use 1 injector up to 3500 RPM and 2 beyond up to about 6000 - harder driving obviously uses more. SO I am training myself in town to shift throught the first three gears VERY quickly to force that 1 injector only scenario. THis of course being when I want to be conservative

8_wannabe

Same experience here, Rod, both with the 87 octane and the injector scenario. I figure the least efficient speed to drive is that which the second or third injector has just kicked in; like another mph slower it would cut off. Put another way, the most efficient driving is as fast as you can go before the next injector kicks in. Don't know if this is true or not, maybe someone can weigh in. Unfortunately, at highway cruising in 6th this means 70 mph. I just find it hard to cruise that speed in the '8; the damn thing just wants to go 80. :D I'm using cruise control a lot now to increase efficiency further.

twinturboteddy

I sent you a P/M

myrx8

I have a base model with no options - I mean nothing. I was considering returning mine for one with more options, but after hearing and reading about this whole TCS and DSC problem with speed and MPG - I think I am going to keep my base model with nothing on it.

I have heard of TCS and DSC slowing cars down.

I'm hoping that with some mods, no options, lighter tires, none of that other equipment to weigh me down, I may just get the speed up there!!

8_wannabe

Just finished a full tank with DSC/TC full off. I've got 2600 miles on my GT now, using 87 octane. Since 2000 miles my mpg has been slowly increasing from 15 up to 18.1. Now with TCS/TC off I got 17.8. Prob 60/40 city/hiway. I shift around 3000 rpm; hiway cruise at 80; never redline; almost never above 6000 rpm.

I'm not sure we have enough data yet to say that the DSC/TC is making a difference or not, just a few anecdotal stories and theories. I'm gonna try it every other tank or so; my current tank I'm not doing it. Let's keep at it and see if we can really establish whether this makes a difference or not.

B-Nez

Yeah, I've had it off for at least 2 tanks now. I thought my mileage seemed better during that 1st tank, but realized that I had also changed the oil. Upon my next fillup, I did the calculations, and mpg was still between 17-18. So, not really an improvement. I've still been leaving it off, though (except when the kids are with me), just because it is so much fun.

8_wannabe

Good point, I forgot to mention. Leaving DSC/TC off brought back that satisfying squeal of tires that had been absent. When I picked up my son at school his friends out front were admiring the car (15-yr-olds). when I pulled a quick U-turn and the tires squealed a bit they were in nirvana with this car. It was way cool.

myrx8

My world with my RX8 is squeling tires and slipping around sharp turns. It kinda brings the sportiness back into the car.

Also, I always drive conservitive in my car with my family.

B-Nez

I LOVE making U-turns, now. Much easier with DSC/TCS off. Also, now when powering around a tight corner, I get that little bit of wheelspin that I can control, rather than DSC cutting my throttle to almost 0 and making that thumping sound. :D

mikeb

It is pretty fun with it off thru the turns

boowana

Yesterday, i filled the car with premium (93 octane) and was careful to fill it exactly. I then started the car, disabled the DSC nad the TCS, set the air on two and with windows up and sun roof closed headed for the highway. It was a 4.5 mile run to get to the highway and I drove the car very easily. Upon reaching the highway, I headed north and slowly brought the car up to 70 mph. I then set the cruise on and left it. Later on the run, the speed limit increased and I reset the cruise up to 75. The total run one way was 71.8 miles. I stopped at a new casino on the Oklahoma border and went in to get a bottle of water. While there, i decided to try my luck. I less than two minutes I was up $43.00 and grabbed the money and ran. On the return trip, I did the exact same thing with the cruise. i wne trihgt back to the gas station to the exact same pump to fill up as before. It took 6.082 gallons and I travled 143.3 miles. That meant i got slightly more than 21 mpg. The weather was at 77 degrees and there was no wind to speak of.
I don't know how I could have done it better and was trying to see the BEST mieage I could achieve when driving in a fashion that represnted my typical driving style.
My question is, how can someone else living in the same area, toting two passengers, driving more in the city get 28 mpg? I would sure like to know. If it is true, there has to be significant differences between one car and another.

Wing

Is 75mph and 70mph over 3750 RPM? Because that's when the 3 injectors start fireing.

I usually cruise at 110km/h which is below the 3750rpm.


I'm happy it is sooo fun today I was going 90mph around a tight corner (it felt like I was only going 60!)...