jimmy_jammy

Hi all, I am new to the RX8 having only owned mine now for just under a week .
I live in the UK and own a Winning Blue, 231 6Spd RX8. I went into alot of research before buying one, and I like the car more and more every day! I knew consumption was going to be bad.... But 3 quarters of a tank I managed to get 106 miles. Is this normal?
Im now doing a experiment with the new full tank, not going over 2.5k revs. So far i've squeezed 23 miles out 1/8th of the tank.

What is the most ecanomical way to drive a rotary engine? the lowest Rpm possible??

Many thanks

Go48

Well, holding it to 2.5K rpms is certainly not good for this car and will not improve your fuel mileage substantially if at all. The best way to improve fuel mileage is to not let the car idle for long periods, avoid stop-and-go traffic, go easy with acceleration, and keep the engine in the power band which is 3K rpms up. On the open road in 6th gear, try to keep the revs below 3,750--the point at which the ECU commands certain functions to happen that can result in more fuel being consumed.

BTW, you cannot accurately measure the fuel mileage using the fuel gauge. You can get a general idea of mileage, but such gauges are not particularly accurate. Fill the tank, note the odometer reading and do that for several tankfuls. Then divide the total miles (km) traveled by the gallons used for those miles and that will give you a reasonably accurate reading of fuel mileage. You should expect to average ~20 mpg for mostly open road driving. Stop-and-go driving mileages frequently have been reported in the low teens--some lower than that.

rx8wannahave

OK, I need to clear this up once and for all because I've heard this before. Driving your 8 at 2.5K does not harm your engine...if it did, then at idle we would all be hurting our engines.

The RENESIS has a built in seal that actually removes carbon so the REV it to 9K daily or else it will build up carbon is hogwash.

With that said, that does not mean that revving to 9K does not loosen things up and make the rotary “feel” nicer but certainly driving at 2.5K does not harm the engine when the owners manual actually states that by 45mph you should be cruising in 6th gear which means the car would actually be under 2.5K...more like 2.25K.

So, what I suggest to you is to shift before 3.8K and make sure you are cruising around in 6th gear when you are going 45mph or more.

I don't do this all the time since I like to push my 8 some but I do it enough that my 8 has never gotten less than 249 miles per tank (or 18.6mpg). My lifetime average is 19.2mpg and when I really drove like a grandma to see how high I could get I reached 20.5mpg in all city driving with normal traffic (not too much not too little).

With all that said, I'm not a rotary expert by any means but from what I have heard here driving the rotary at 2K is not going to harm your car nor is hitting 9K.

When my 8 is cold I always shift at 3.5-3.8K (as well when I'm just cruising around), but when I'm more aggressive I shift in the 5+K range (when I REALLY want to play I nail her 9K hot spot often).

Note: If I'm wrong, please teach me...cause again I'm not a rotary expert...only a newb.

Go48

If you're "not a rotary expert" why are you making such definitive statements? Certainly idling momentarily at 2.5K won't harm the engine. But lugging the engine for long periods while driving in the higher gears is not good for the engine. The engine should be in the power band in order to not stress the engine and the power band starts well above 2.5K.

grapes

jimmy jammy- I would strongly suggest that you use Go48's advice for optimal gas mileage. Don't lug the engine at 2k RPM's shift at around 3,500 and remember that the gas tank is shaped quite narrow at the top. That might explain your poor mileage in the first quarter tank. Good luck. Keep us informed.

rx8wannahave

Did I not leave the door open to being wrong? "not an expert"..."teach me if I'm wrong"...why did you ignore that?

Again, unless some of the rotary brains come in here and tell me otherwise I still think it's OK to drive around town going 50MPH and in 6th gear. IF...that is harming my engine, then this is the last rotary engine I buy.

I didn't know that power band = no stress, last I heard race cars put alot of stress on engines and it's not because they are cruising around but because they are running it constantly in it's power band.

Again, I could be wrong but if my engine dies I'll blame Mazda since they state in their owners manual that I should be driving it in 6th gear past 45mph for optimal fuel economy.

No offense, maybe you know more about the rotary engine than I do...but I still would like to hear more on this.

Did you know about the seal that scrubs carbon off the Renesis? Maybe I misunderstood that...but I don't have the link with me to show you what I mean.

AGAIN...I'm completely open to being wrong, until I hear it from more people I think I'm right on this.

zoom44

it is ok to drive around town in 45 in 6th gear. but you should still rev it (in gear while moving not free revving) at least once a day once warm. it really is better for teh overall health of your engine. there is no "scraper seal"

jimmy pleae read the sticky thread https://www.rx8club.com/new-member-forum-197/cumulative-gas-mileage-gas-mpg-thread-61139/ and post there if you have more questions

rx8wannahave

OK...agreed with me, agreed with "you should still rev it for the better health of your engine" which I didn't disagree with, but no "scraper seal" agreement?

Zoom44 here is where I got it (thank you google):

Linky

This is what they said:

Newly Designed Seals: Renesis employs a new cut-off seal located between the rotor’s dual oil seals and side seal. This sealing arrangement eliminates blow-by between intake and exhaust ports and prevents carry-over of exhaust gas to the next intake cycle. Side seals are a new keystone-type with wedge-shaped section. Exhaust gas build-up against the side seal can easily cause carbonisation, but with the wedge-shaped or cuneiform side seal, the seal shape is optimised to remove carbon.

...and here is the picture:

zoom44

the side seal is optimised for cleaning carbon build up from itself. it doesnt say it removes all carbon build up or even if it stops all carbon build up against itself. just that it removes as much as possible.

i was actually going to get the same pic

rx8wannahave

So where in the engine does reving high help clean?

This is my first rotary and I'm always willing to learn something new.

zoom44

the extra heat helps burn it off where ever it is.

rx8wannahave

I see, how effective are fuel, carb, injector, etc cleaners on a rotary engine? I think we can agree that techron from Chevron has been shown to really keep the combustion camber clean on piston engines...does anyone know if they are as effective on the rotary?

Sorry for sidetracking this thread....

jimmy_jammy

Ahh... I feel so much better after spending a couple of hours sitting down, using the search button and absorbing all this new information like a sponge on how to treat a rotary engine!! lol

So bottom line is that what i've learnt...

Optimum fuel efficent driving is around 2.5-3.5k Rpm

Rotary engines are nothing like a normal engine (i knew that anyway :p)
and that its actually GOOD to Rev the engine hard, and to drive with high RPM as to compared with a normal piston engine it is bad... I still cant get over that!
I've been treating my new car with such respect and being careful lol...worrying about wearing the engine out, and ive been driving it totaly wrong so far.
And of course letting the car warm up 'n all.... (we all know that one.)

I just need to say what a great help all you guys are, I cant wait for the next time i drive my RX8, that i know now to keep reminding myself its GOOD to redline it, and keep it up in the high Rpm's... thats what driving is all about!

Having owned 4 previous cars, and enojying while you can redlining a few gears, but deep down you know your torturing the engine....Now I am Freeeeeeeeeeee lol

rx8wannahave

I was in your shoe's once...and on some levels still am, you really learn alot here and learn to fall in love with the RX8 and rotary engine quickly.

yiksing

Idling in low rpm is not the same as under-revving (lugging the engine) in gear (you are loadng the engine in the latter). I don't know much about a rotary engine but in a piston engine, lugging may cause piston slap (just something I read, not sure if its true or not)

Foamy

Hi rx8wannahave and others - you get 19 mpg !!!!!! I would die for this, my average is 14mpg with many weeks at 6 - 10 mpg (US Gals).
Measure by filling up and noting miles at every fill up since new.
I got my new AT in Oct 2004, love it to bits, but the fuel economy often tests my love for it, mainly because I have to stop for gas every 150 mils or so.
Do the experts out there think I might have an engine problem, I got most Flash updates (I think), I live in the cold NE USA so have to remote start my RX8 for 5 minutes twice a day.
For those that tell me to do a search, I have and not got much relevant information - re-borne threads are not all bad IMHO

Go48

Well when you idle the car for 10 minutes a day, you WILL get poor mileage. Not necessarily that bad, but if your engine is running at idle, whether in your driveway of at traffic lights, you're not racking up any miles while you're burning fuel. If most of your driving is stop and go, that will kill the fuel mileage in this car.

Let the car warm up for a minute or less and then drive off keeping the rev at or below ~3K. That should improve your mileage a little.

Foamy

Hi Go48 - I agree, while idling fuel is consumed and no miles clocked up, I do occaisionally let her idles for 5-10 mins, but mostly do as you suggest, get on the road and go easy until warm.
However, before I got the rotary my driving pattern with a piston engine was the same. I am quite sure that the piston engine did not suffer such a reduction in MPG because of the idle periods.
Does anyone know if the Rotary is more prone to gas guzzling at idle than a regular piston engine ?? Can't solve the problem I know, just curious.

yiksing

It definitely guzzle more gas when idling than moving around. I'm getting quite good mileage now about 450 km full tank and I never idle, only the first 30 seconds warm up then take it easy under 4000 rpm. Shortest trip I take is around 12km with mixed driving habits but then again I lived in tropical weather.

Jaguar_MBA

When I drive to save fuel, I keep the RPMS below 3,750. The secondary intake ports open at 3,750 RPM (6 speed) and I construe that once those secondary ports open, the engine will start injecting more fuel. When I cruise on the highway I will set the cruise control at a speed that will keep the RPMS at ~ 3,600 RPMS.

max5roadster

I just got done doing my first trial mileage test with my mid-pipe installed:
22.5mpg!
(10-15 city, 85-90 hwy.)
Keeping revs low without lugging and only redlining about 5 times to pass. Warm-up times varied, but I made sure to accelerate at a rate that would **** off grandma. My best in the summer was 23.6 all interstate. I can't wait till it warms up and we switch back to a summer grade fuel mix! 25 mpgs Here I come!

max5roadster

Oh I forgot to mention I also have a gutted airbox (1st MAF screen removed) with a K&N cone filter mounted inside. I use Royal Purple 5-30 and Premix with Lucas Oil UCL (Upper Cylinder Lube).

rx8wannahave

6-10mpg Wahhhhhhh

I don’t see how you could get that even by trashing it like your life depended on it. Either you have a problem 8 or something in your driving habits aint helping your situation out.


Well when you idle the car for 10 minutes a day, you WILL get poor mileage.

A HA!

What he said, and it sounds like you do it for up to 20 minutes sometimes. That my friend, is what is really hurting you.

I’m in FL so our temp’s don’t get too low but regardless you shouldn’t have to heat her up for 5-10 minutes every day.

What I normally do in the morning is let it idle for about 30sec and then go. You warm up the engine faster by driving it but like already stated do not push the 8 when cold (or any car really). When the 8 is cold keep the rev’s under 4K max and if possible under 3.5K.

Oh and yes, my lifetime average has been just over 19 mpg in city driving (max 20.5 minimum 18.6mpg). I don’t hit a lot of traffic but my drive is not traffic free either. I don’t drive like a grandma but I’m not hitting 9K after each red light. I have a base 6spd fyi.

BALANCE is the key to have fun and maintain decent fuel economy. Also, like stated keep it at about 3.6K on the highway and that should help things out also.

I hope the best…try what we say and report back.