RE: Mazda RX-8: PH Heroes

[Fastdruid]

untakenname said:

Lots of enthusiasts fit a 'SOHN' system which feeds the engine pure 2 stroke from a separate tank, this has the added benefit of then being able to run proper synthetic in the sump giving the bearing far better protection, most also premix putting 2 stroke into the petrol tank to further help lubrication.

Trouble about pre-mixing is unless you change the map you end up running weak. Of course the RX-8 runs rich anyway to preserve the cat so it may not be that big of a deal in reality (apart from the poor cat).

If I actually had enough time to drive one for fun I'd have another...I'm still contemplating putting one in a locost while you can pick them up for pennies. Fit new coils, a SOHN kit (I knew they did one but it's been a while, I could not remember the name), lose the cat and re-tune. More reliable, more power, better fuel economy, what's not to like?

[Christmassss]

Black S2K said:

The earlier 'rebuild it yourself' post is also interesting - I presume it's all seal wear and the chamber liners don't need any attention?

I've long maintained that anyone used to two-stroke 'bikes wouldn't find the engine at all daunting - there are similarities.

Generally its just the seals. From memory i think the Apex seals are the common failing factor on the Renesis engine.

The housings/rotors will probably need replacing if the apex seal has come away from the rotor and been thrown around the engine. You can get the housings refurbished for minimal £.

Essentially: Poor Spark due to the shocking factory Coils, Causes unburnt fuel to wash away the oil, no lubrication fks the seals.

A well looked after rotary will go on for just as long as a normal engine. The engine in my FC is on 148k, highly modified. No issues. My home built engine in the FD is still going.

As i alluded to, if (when!) i get an RX8, i would go the whole hog, carbon ceramic seals, porting, get the rotors properly balanced etc. Be interesting to know how far you could push it whilst staying NA and only 2 rotors.

[otolith]

Fastdruid said:

It was something that I was always concerned about...but didn't have a single problem with ours. Stalled it a few times but it re-started fine. Ours was an MY06 though which had a bunch of fixes from the earlier cars (better starter, different flash on the ecu).

Mine did it once, had to get the AA to restart it (as I recall, basically supply it with power to stop it flattening the battery, pull the fuel pump fuse, and keep cranking it, pausing periodically to let the starter cool). Can't remember what I'd done with it the night before.

[cib24]

Christmassss said:

Generally its just the seals. From memory i think the Apex seals are the common failing factor on the Renesis engine.

The housings/rotors will probably need replacing if the apex seal has come away from the rotor and been thrown around the engine. You can get the housings refurbished for minimal £.

Essentially: Poor Spark due to the shocking factory Coils, Causes unburnt fuel to wash away the oil, no lubrication fks the seals.

A well looked after rotary will go on for just as long as a normal engine. The engine in my FC is on 148k, highly modified. No issues. My home built engine in the FD is still going.

As i alluded to, if (when!) i get an RX8, i would go the whole hog, carbon ceramic seals, porting, get the rotors properly balanced etc. Be interesting to know how far you could push it whilst staying NA and only 2 rotors.

Not very far. You are restricted by the exhaust port design on the Renesis. Sure, it cleans up emissions but the two 90 degree bends for the side exhaust port make the car more susceptible to flooding and limits the power you can make. Mazda maxed out the Renesis from the factory with the largest intake ports it ever put on a rotary. Porting those further nets you about 10-15hp.

Older rotaries with peripheral exhaust ports could be ported on the intake and exhaust side to produce in excess of 300bhp N/A, and drag cars on meth with lots of timing and ignition advance that didn't need to last long could see 400+bhp from the little 13b.

[Phil Dicky]

Gridfire said:

Coincidentally my 2007 RX8 is sat waiting for collection by a salvage company right now, as I've just replaced it with a TT. It works but has a few dents, a cracked windscreen, needs new tyres, and frankly I don't want to spend the money to make it saleable to only expect £1500 at best.

It gone yet

[Black S2K]

Fastdruid said:

Black S2K said:

That's very interesting information - Mazda claimed at the time they'd fixed the tip wear and then it looked like they hadn't.

The R3 they added an additional lubrication hole, as you say it's obvious that they hadn't fixed the wear.

Personally I would have thought they would have been best running a separate oil injection system rather than try and use engine oil. Akin to two-strokes and indeed using two-stroke oil. They would then be able to use "perfect" oil that was designed to be burnt rather than the compromise engine oil. It would also mean a nice neat tank which would be easy to top up and could have a gauge/low warning on it.

On the subject of oil though...for something that was designed to use oil it had the most god awful dipstick and filler. You needed to remove the engine cover and reach right the way over the engine.

I remember reading that, now you mention it!

Got very close to buying one back then, but then the 86 was rumoured...I'm pleased that its solecisms may be fixed, as I have a soft spot for things Mazda.

[delta0]

Fastdruid said:

Trouble about pre-mixing is unless you change the map you end up running weak. Of course the RX-8 runs rich anyway to preserve the cat so it may not be that big of a deal in reality (apart from the poor cat).

If I actually had enough time to drive one for fun I'd have another...I'm still contemplating putting one in a locost while you can pick them up for pennies. Fit new coils, a SOHN kit (I knew they did one but it's been a while, I could not remember the name), lose the cat and re-tune. More reliable, more power, better fuel economy, what's not to like?

This is completely incorrect. You do not run “weak” by premixing, whatever that means. Maybe you meant lean, again you do not have any problems premixing and will not run lean.

Fastdruid said:

The R3 they added an additional lubrication hole, as you say it's obvious that they hadn't fixed the wear.

Personally I would have thought they would have been best running a separate oil injection system rather than try and use engine oil. Akin to two-strokes and indeed using two-stroke oil. They would then be able to use "perfect" oil that was designed to be burnt rather than the compromise engine oil. It would also mean a nice neat tank which would be easy to top up and could have a gauge/low warning on it.

On the subject of oil though...for something that was designed to use oil it had the most god awful dipstick and filler. You needed to remove the engine cover and reach right the way over the engine.

As it is a mid engine then yes you have a bit further to reach. The R3 does not require the cover to be removed to access the dipstick.

Edited by delta0 on Thursday 13th September 23:37

Edited by delta0 on Thursday 13th September 23:39

[Fastdruid]

delta0 said:

This is completely incorrect. You do not run “weak” by premixing, whatever that means. Maybe lean, again you do not have any problems premixing.

Lean is the same as weak.

https://encyclopedia2.thefreedictionary.com/weak+m...

Whatever you want to call it, unless you change the map you will be injecting less actual fuel per event as a percentage will be oil instead.

The RX-8 runs rich at a number of places to keep the cat cool, so it is *highly* likely that a weak mix will not cause it to run significantly lean. Certainly it wouldn't under closed loop conditions but it's possible it runs a touch lean under open loop.

[Fastdruid]

delta0 said:

As it is a mid engine then yes you have a bit further to reach. The R3 does not require the cover to be removed to access the dipstick.

Correct me if I'm wrong....but while it has a flap for the dipstick you still have to remove it to top up. Which is pretty much going to be every time you're checking it. So you still need to remove it every time!

[PorkRind]

I dont think anyones mentioned turbo charging it, like the old rx7, is that an avenue any of you have tried or is it just not worth the money?

[delta0]

Fastdruid said:

delta0 said:

This is completely incorrect. You do not run “weak” by premixing, whatever that means. Maybe lean, again you do not have any problems premixing.

Lean is the same as weak.

https://encyclopedia2.thefreedictionary.com/weak+m...

Whatever you want to call it, unless you change the map you will be injecting less actual fuel per event as a percentage will be oil instead.

The RX-8 runs rich at a number of places to keep the cat cool, so it is *highly* likely that a weak mix will not cause it to run significantly lean. Certainly it wouldn't under closed loop conditions but it's possible it runs a touch lean under open loop.

Firstly the 2 stroke oil will combust and secondly its mix ratio is around 400:1. The amount that is added is negligible from a combustion point of view. It is so small you wouldn’t even be able to measure any changes.

Fastdruid said:

delta0 said:

As it is a mid engine then yes you have a bit further to reach. The R3 does not require the cover to be removed to access the dipstick.

Correct me if I'm wrong....but while it has a flap for the dipstick you still have to remove it to top up. Which is pretty much going to be every time you're checking it. So you still need to remove it every time!

You literally lift it up and place it on the front of the engine bay. It’s not that uncommon in modern cars to have to remove a cover and at least with the RX8 you actually have room to put it somewhere.

PorkRind said:

I dont think anyones mentioned turbo charging it, like the old rx7, is that an avenue any of you have tried or is it just not worth the money?

It is done but it is expensive. The RX8 does already produce more power than the RX7 FC and earlier, and similar power to the UK spec FD. The main one that produced notably more was the JDM spec version.

Edited by delta0 on Friday 14th September 05:15

Edited by delta0 on Friday 14th September 05:19

[cib24]

Not entirely true. The RX-8 makes about 190-210hp in reality and far less torque. The FD in all forms is a much quicker car.

As for turbocharging, the Renesis isn't ideal due to the restrictive side exit exhaust port design. It severely limits flow above factory power levels and causes huge amounts of heat to be generated which kills reliability unlike when dealing with the older peripheral exhaust port 13b motors.

[Christmassss]

cib24 said:

Not very far. You are restricted by the exhaust port design on the Renesis. Sure, it cleans up emissions but the two 90 degree bends for the side exhaust port make the car more susceptible to flooding and limits the power you can make. Mazda maxed out the Renesis from the factory with the largest intake ports it ever put on a rotary. Porting those further nets you about 10-15hp.

Older rotaries with peripheral exhaust ports could be ported on the intake and exhaust side to produce in excess of 300bhp N/A, and drag cars on meth with lots of timing and ignition advance that didn't need to last long could see 400+bhp from the little 13b.

Not strictly true, Re-ameniya have achieved around 280 primarily just porting the side ports and the much overlooked seal clearances. Many people over look this. The stock engine has a massive tolerance from factory and this massively affects power.

Panspeed built a 300bhp 2 rotor renesis, but using the 13b rx7 housings. Although they have moved onto a 3 rotor system.

Knighsports also did one, but info is thin on the ground.

Its all down to cost - I think if you were to pay someone to do Renesis work it probably wouldn't be worth it in relation to £ to Power return. But as I (and my tame Rotary tuner) would be doing the work, it makes it worth while!

I notice you also have an RX7, 395hp from stock twins is impressive. Whats your spec?

Edited by Christmassss on Friday 14th September 12:21

[Black S2K]

Christmassss said:

Not strictly true, Re-ameniya have achieved around 280 primarily just porting the side ports and the much overlooked seal clearances. Many people over look this. The stock engine has a massive tolerance from factory and this massively affects power.

Panspeed built a 300bhp 2 rotor renesis, but using the 13b rx7 housings. Although they have moved onto a 3 rotor system.

Knighsports also did one, but info is thin on the ground.

Its all down to cost - I think if you were to pay someone to do Renesis work it probably wouldn't be worth it in relation to £ to Power return. But as I (and my tame Rotary tuner) would be doing the work, it makes it worth while!

I notice you also have an RX7, 395hp from stock twins is impressive. Whats your spec?

Edited by Christmassss on Friday 14th September 12:21

Could well explain why no-one found a production one that made 237 BHP.

I'm fascinated by this sort of detail crap...

[southendpier]

I've been running a 40th Anniversary coming up 4 years.

It does drink fuel, it doesn't drink oil - really. I do around 4.5 k miles per year.

I did flood it once doing a car shuffle on the drive This was annoying but totally my fault! Sorting that out is very simple providing you have enough battery juice to crank the starter with the fuel pump shut off.

For those that haven't driven one they really are unique. You can happily just leave it in 2nd around town - 30 mph is 4,000 rpm. It just sounds odd at first as you are not used to the engine whizzing away with so much room to rev even more. It'll rev to 9.5k in 1st and that is around 42 mph. If you keep the revs in the right range it is a very lively sports car,

it is a small car but 4 seats is very useful and the boot is deep and interior many storage hatches etc

in summary; the RX8 is a much better car than I thought it would be.

[RJG46]

Our local Garage in Hextable, Home Hill, always has a good number for sale. Selling and working on RX-8s seems to be pretty much all they do. Not used them as I don't have one.

[Christmassss]

Black S2K said:

Could well explain why no-one found a production one that made 237 BHP.

I'm fascinated by this sort of detail crap...

I do love a rotary engine.

Stock engines and probably many rebuilt engines will end up with a side seal clearance of 0.3/0.4mm which is huge! Re-Ameniya recommend 0.08-0.1mm. The bigger the gap the lower the power - as an attributing factor. Which as you rightly point out, is why even standard ones struggle to make the quoted power, as they wear they lose more and more power.

[delta0]

cib24 said:

Not entirely true. The RX-8 makes about 190-210hp in reality and far less torque. The FD in all forms is a much quicker car.

As for turbocharging, the Renesis isn't ideal due to the restrictive side exit exhaust port design. It severely limits flow above factory power levels and causes huge amounts of heat to be generated which kills reliability unlike when dealing with the older peripheral exhaust port 13b motors.

I didn’t say it was quicker than an FD, although around a track it is stock vs stock. Torque at the wheels is the most important and there isn’t much difference. The turbo does of course get you a nice wide high torque band and easier tuning potential. With it also being lighter you get a low 5s to 60 time stock. The 8 is a low 6s time and the R3 with a little less mass and even shorter gears gets you just into the 5s.

Edited by delta0 on Friday 14th September 13:07

[Christmassss]

delta0 said:

I didn’t say it was quicker than an FD, although around a track it is stock vs stock. Torque at the wheels is the most important and there isn’t much difference. The turbo does of course get you a nice wide high torque band and easier tuning potential. With it also being lighter you get a low 5s to 60 time stock. The 8 is a low 6s time and the R3 with a little less mass and even shorter gears gets you just into the 5s.

Edited by delta0 on Friday 14th September 13:07

Interestingly, Panspeed sacked off their Time attack FD RX7 in favour of the RX8, 20b NA...The noise...

[cib24]

Christmassss said:

Not strictly true, Re-ameniya have achieved around 280 primarily just porting the side ports and the much overlooked seal clearances. Many people over look this. The stock engine has a massive tolerance from factory and this massively affects power.

Panspeed built a 300bhp 2 rotor renesis, but using the 13b rx7 housings. Although they have moved onto a 3 rotor system.

Knighsports also did one, but info is thin on the ground.

Its all down to cost - I think if you were to pay someone to do Renesis work it probably wouldn't be worth it in relation to £ to Power return. But as I (and my tame Rotary tuner) would be doing the work, it makes it worth while!

I notice you also have an RX7, 395hp from stock twins is impressive. Whats your spec?

Edited by Christmassss on Friday 14th September 12:21

Interesting. Show the proof of the RE-A one as I am curious. In any case no one in the UK has made more than 230-240 without extreme and undrivable port work.

Panspeed's 300bhp car is not really much of a renesis anymore because the housings they use have peripheral exhaust ports which I explained in my previous post flow soon much better and have so much more potential. That car's engine is much more in line with every other rotary prior to the Renesis.

My FD dyno'd at 398bhp (340 to the wheels) and 360lb ft of torque (300-ish to the wheels) from a relatively generous Dyno. So let's call is 375-400hp depending on where you take it to be dyno'd.

Mods are pretty basic as I focused on key weak points and wanted to retain a stock OEM look.

Twins with increased boost pressure to 1.05 bar up from 0.75.
Stock air box and paper air filter but a Greddy stock location intercooler (not very big).
Water injection at a small 250cc/min dosage to keep intake temps cool when the small intercooler heatsoaks.
3" downpipe, 3" midpipe with high flow cat, 3" back box.
HKS Twin Power ignition amp
Hotwired stock fuel pump to make sure it sees maximum voltage at WOT.
Apexi Power FC custom ECU tune.

That's it.

Edited by cib24 on Friday 14th September 14:14