What have you done to your RX-8 today????

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Re: What have you done to your RX-8 today????

Post by nightfire10 »

Perhaps one of these Image

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Re: What have you done to your RX-8 today????

Post by 13Black »

Eeeee kawai desu desu.

Must find a way to drift that.
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Re: What have you done to your RX-8 today????

Post by akhan48 »

johnbb99 wrote:
Sun Dec 16, 2018 8:54 pm
It may be better to discuss this idea elsewhere, so mods would you move it or tell me where it should be, please?
I would be very interested if there was a way to increase the economy of the RX8 even if that meant reducing the power output.
I realise I will be in a minority, maybe of 1, but it bothers me (from an ecological point of view) that the fuel consumption is as high as it is.
I'm talking about an actual improvement not lowering the cost by using LPG for example.
For me, the particular attraction of the RX8 is it's balance and handling and steering so I would be prepared to accept a moderate reduction of power output.
Is there any way to achieve this?
Your best bet would be to use it as a weekend car or sell it and buy an electric car as a daily if you’re so concerned about the environmental impact.

I’ve found that the way I drive it makes little difference to MPG. Climate makes more of a difference. I get about 30 miles a tank more in the summer. You can also get a few more miles using Tesco 99 or V Power. My remap has made my MPG worse so I wouldn’t count on that either.
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Re: What have you done to your RX-8 today????

Post by kopite72 »

It doesnt matter a damn what you do, fact is the moment you turn the key there's over 300 CO2's eminating from the arse end of the car and that's that.
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Re: What have you done to your RX-8 today????

Post by New Duke »

Put the track wheels into the garage loft. After having dropped one on my ear then fell off the ladder. My ear still hurts.

Good times :lol:
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Re: What have you done to your RX-8 today????

Post by jondkent »

Managed to achieve worse mpg ever in the last week. 130 miles over the last week or so and tank only 1/4 full now. Lots of short trips though which would explain.

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Re: What have you done to your RX-8 today????

Post by MARKTHOMASBRAND »

kopite72 wrote:
Sun Dec 16, 2018 9:21 pm
Yep,buy a prius....you're in the wrong car and on the wrong forum,is this a troll? Seriously?
No Ian...John is not a troll :!:

Met him on the Wales Road Trip & he's a lovely guy :thumleft:
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Re: What have you done to your RX-8 today????

Post by kopite72 »

My bad then,I read it and just thought....seriously? If you're reading this John then I apologise but I guess the simple answer is no.As you know these cars are not exactly environmentally friendly and there's pretty much nothing we can do about it.....
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johnbb99 (Mon Dec 17, 2018 11:09 pm)
R3 GONE, FUN WHILE I HAD HER BUT NOW LOVING MY 25TH ANNIVERSARY MX5

Mods so far..
BBR 200 PACKAGE
COBRA " RACE " BACK BOX
MEISTER COILOVERS
KONIG HYPERGRAMS ( POLISHED LIP)
RACING BEAT ARB's ( FRONT AND REAR )
IL MOTORSPORTS STRUT BRACE AND ADJUSTABLE
DROPLINKS

Mods planned..
BBR STAGE 2 SUPERCHARGED
WILWOOD 6 POT BBK
FULL UNDRBODY SEAL
ATOTO HEAD UNIT
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Re: What have you done to your RX-8 today????

Post by warpc0il »

jondkent wrote:
Mon Dec 17, 2018 8:17 am
Managed to achieve worse mpg ever in the last week. 130 miles over the last week or so and tank only 1/4 full now. Lots of short trips though which would explain.

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Driving the 8 like you would to get the best mileage from a conventional car, and the mileage will get noticeable worse.

The efficiency of a rotary engine improves as the revs rise, before dropping off again near the maximum.

Driving in at least one gear, sometimes two gears, lower than you'd expect, will keep the engine in this more efficient band and improve both the mpg and spg (smiles per gallon)

The mouse mat mod significantly helps with mpg on short journeys in the cold, as the PCM gets to switch to warm running quicker and the oil isn't so thick for so long. See viewtopic.php?f=30&t=53888

Also check tyre pressures, as these can drop in the cold weather and increase the rolling resistance.

If you can drive a section of road being very light on the brakes and come to a halt uphill hardly using the brakes at all, then get out and put your hand against the centre of each wheel. The rear wheels should be chilled and the fronts only slightly warmer. If any are really warm/hot then you have a brake rubbing, which will eat into your fuel consumption and is "a bad thing" anyway.
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Re: What have you done to your RX-8 today????

Post by PeteH »

I think getting more mpg is an interesting task. There are mods you can do that would significantly help (although all come with compromises, of course):

1) A clever remap would work. You would need to run it at 15 or 16 AFR up to about 25% throttle and 5000rpm. Just make sure you go rich at higher loads.
2) Fit an FD Auto diff. This has a ratio about 15% longer than the 8 diff. Top gear acceleration would be non-existent, but motorway cruising would be more economical.
3) Do what you can for aero. Remove the wing mirrors. Fit a flat floor. Put a smooth cover over one of the oil coolers.
4) Do all the lightening stuff the race cars do, such as strip the interior, remove the sound deadening, remove the air con, etc.
5) Reduce alternator load by removing the air pump, electric power steering etc.
6) Fit skinny tyres, and inflate them as high as possible.

All of these together, coupled with an economical driving style, should significantly improve the mpg. Whether you would still consider that it "feels like an 8" is another matter....
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Re: What have you done to your RX-8 today????

Post by Scartlead »

The only decent thing to do with an 8 is drive it like you stole it :) any notion of concern with emissions is totally redundant. Personally I have to pay seriously crap and unfair road tax for the privilege. Red line all the way!
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Re: What have you done to your RX-8 today????

Post by johnbb99 »

Thanks for the recent helpful comments on my [admittedly] unusual query.
PeteH's points are exactly what I was looking for.
1 looks very interesting, I wonder what would be different, (and what are AFRs?).
2 also a possibility
3 I couldn't do without wing/door mirrors, but a flat floor could be good. Group buy anyone? :)
4 Logical, but a step too far for me. (Although I could do without all the gubbins on the electric seat.)
5 Maybe... (I should know what that air pump does...) More steering feel? - OK! (But I'd probably have to spend time in the gym before I could park it!)
6 Skinny tyres? Nah! (Because:- A) looks matter & B) adverse effect on The Handling, doubtless.)

We all look for different things in our RX8s. Some want a track car, others a daily drive. (etc, etc). I revel in it's handling (which is why, like others, I've just shelled out on new PZ suspension.)
John -- ex-owner of a Winning Blue 231
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Re: What have you done to your RX-8 today????

Post by johnbb99 »

Scartlead wrote:
Mon Dec 17, 2018 1:26 pm
Personally I have to pay seriously crap and unfair road tax for the privilege.
Me too. It's a bummer.
John -- ex-owner of a Winning Blue 231
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Re: What have you done to your RX-8 today????

Post by warpc0il »

The Secondary Air System (aka air pump) is part of the emissions system and helps the cat get to working temperature quickly during a cold start. It's redundant all the rest of the time. However, it weighs much less than the contents of my wife's handbag and is only removed from race cars as part of an extreme diet or to free space under the bonnet for something more important - like a turbo.
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Re: What have you done to your RX-8 today????

Post by PeteH »

Chasing mpg is like chasing lap time. There's no single big thing. It's a hundred tiny things that all add up.

AFR is air fuel ratio. If you don't have a cat then you can afford to go quite lean at light loads.

Skinny tyres can look OK. With the right wheel offset they can look very much like stock wheels and tyres. And they don't have to ruin the handling too much. But if you don't want to do that then buy eco tyres, and run them 5psi high than recommended. It will also affect your handling a bit, but will make a big difference to your cruising mpg. And you can drop the pressures when you want to hoon it.
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Re: What have you done to your RX-8 today????

Post by Goobie »

Rotated it 90 degrees...
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Re: What have you done to your RX-8 today????

Post by bigpete8 »

That's one heck of a garage 😀
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Re: What have you done to your RX-8 today????

Post by AutoGibbon »

Is that the garage/unit I think it is?

Also:
PeteH wrote:
Tue Dec 18, 2018 7:18 am
AFR is air fuel ratio. If you don't have a cat then you can afford to go quite lean at light loads.
Why or how does that work?
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Re: What have you done to your RX-8 today????

Post by PeteH »

AutoGibbon wrote:
Tue Dec 18, 2018 9:47 am
PeteH wrote:
Tue Dec 18, 2018 7:18 am
AFR is air fuel ratio. If you don't have a cat then you can afford to go quite lean at light loads.
Why or how does that work?
I'm not sure what the question is. Are you asking how to change the AFR? Or why a lean AFR reduces fuel consumption? Or why you can't do it with a cat? Or something else?
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Re: What have you done to your RX-8 today????

Post by Dr. FrankenRex »

AutoGibbon wrote:
Tue Dec 18, 2018 9:47 am
Why or how does that work?
The catalytic converter likes the car to run a little rich, so that it can keep the core temp of the cat down. If it gets too high the components melt and it causes collapse and failure.

In a car running a decat, that is less of a concern, as such you can run the engine leaner (less fuel) which creates more complete combustion, both aiding power and fuel consumption - just not at the same loads.

The only thing that need be considered with an RX8 is that the fuel at the top end of the rev range is actually used as an additional coolant for the internals of the engine, so you can't lean it out too much up there without causing additional damage to the internals through extra heat buildup :thumleft:
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Re: What have you done to your RX-8 today????

Post by AutoGibbon »

PeteH wrote:
Tue Dec 18, 2018 10:32 am
I'm not sure what the question is. Are you asking how to change the AFR? Or why a lean AFR reduces fuel consumption? Or why you can't do it with a cat? Or something else?
Sorry, was asking how running without a cat allows you to run lean. DrDan has answered in full, cheers.
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Re: What have you done to your RX-8 today????

Post by warpc0il »

The easiest way to visualise a lean (economical) vs a rich (powerful) AFR is...
- in a lean mixture, every molecule of fuel needs to be surrounded by molecules of air, so that all the fuel gets burnt.
- in a rich mixture, every molecule of air needs to be surrounded by molecules of fuel, so that all the air gets burnt.

Real life is never as simple as that and charge-cooling, flame-front management and a whole bunch of other stuff get in the way.
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Re: What have you done to your RX-8 today????

Post by johnbb99 »

Might there be any gains to be had by flowing and polishing to improve the breathing of the engine, or did Mazda get that pretty well right in production?
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Re: What have you done to your RX-8 today????

Post by PeteH »

As a general rule, flowing and polishing gains you a bit more peak flow (power) at high revs, but makes little difference at lower revs. At lower revs the engine isn't usually restricted by flow losses, so it can easily pull in all the air it needs.

If it's engine mods we are looking at then the options are very limited, and not very effective:
1) The tune (AFRs, as previously mentioned).
2) Reducing the losses. That means thinner oil, lower oil pressure, slower water pump, no air con, minimum alternator load. Obviously some of these are a very bad idea on a rotary...
3) Seriously reducing the losses. Ceramic coating the plates, and running ceramic seals. Serious money for small gains.
4) Higher compression. Nearly impossible for us. Damn those piston engine things.... :evil:
5) Maximise the calorific value of the fuel. This means running no premix (DUCK!!! :shock: ). Oddly, it also means running 95 octane fuel, unless you can remap for higher octane.
6) If you do all the intake mods (RB snorkel, high flow filter, polished everything) this will help a tiny bit. Don't make the ports bigger, or bridge them though, since they decrease low rev efficiency. Exhaust mods (as free flow as possible, and decat) will also help a tiny bit.

That's about all I can think of for the engine. Mazda did a good job, and trying to improve upon it will cost you serious money for rather small gains, and probably a significantly reduced engine life.
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Re: What have you done to your RX-8 today????

Post by johnbb99 »

Thanks for another very clear and full answer, Pete.
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