I have emailed MoTeC Australia regarding their M800 and M880 engine management systems. This is their very interesting reply. Could some of you more technically-minded people decipher and summarise this for me so it's easier to understand.

Thanks

Michael

Message from MoTeC
Michael,
Both Motec Japan and Motec USA have installed an M800 on an RX-8, the factory ECU is removed. The engine is no trouble after a few issues are addressed:

1) Trigger wheel must be changed from 36-2-2-2 to 36-2

2) The DC Generator must be replaced with a conventional 3rd generation RX-7 (FD3S) alternator unit. It drops in, using all the stock RX-8 mounting points, belt, and terminals.

3) The secondary injectors need to be wired in pairs

The ecu will require the SERVO code for the OMP function to work, and an M800 will be necessary in order to get the OMP to work as we need the extra injector drivers.

The car however, is a whole lot more complicated. Removing the factory ECU will terminate the dash cluster (speedo, odo, temps, fuel level, warning lights, status lights, etc.), electronic stability control, power steering, cruise control, A/C control, engine cooling fan control, emissions control, secondary air injection, and so on. ABS still functions.

The information I've had from the US indicates that gains are very hard to come by on stock parts. Also, the intake system seems to be very sensitive to how it is manipulated. It presents less than 100 kPa under the throttle at WOT - around 95 kPa. The (70mm) DBW throttle may be the choke point, not sure. There appears to be a trade-off in the design of the intake system that was very carefully examined and massaged to give the best end result. It goes to show that some manufacturers are putting a lot of effort into development - certainly in this case, where the engineers were given a target hp figure... Aftermarket tuning with the Motec ECU will come into its own with a modified race engine.

Cost would be retail for the M800, a wiring harness, new trigger wheel, fitting and tuning by a Motec dealer.

Regards,
Andrew Naumann
MoTeC P/L

 

1) No idea
2) You need to remove the '8s alternator [0] and fit an FD RX-7 one
3) Not sure. I could speculate but would most likely be wrong.

SERVO code) Something to do with the OMP - Oil Metering Pump. I don't think I need to tell you how important this is.

Next para) You can install the MoTeC ECU but you lose all the standard RX-8 items listed. At the least this would mean having to install a custom dashboard, 'normal' radiator fan and you would still have no A/C, ESC, power steering [1], cruise control, emmisions control [2] etc.

In short - you can do it but it would be a Bad Thing(TM) on a daily street driven car. It would seem that the implicit message from Mazda is "don't muck with it unless you're really serious" [3]. Or possibly Mazda is going to release their own hot up kit in the near or not-so-near future.

OR you could wait for someone to develop a piggy back ECU that leaves all the niceties and just lets you play with fuel and ignition.

It is still very early days for the '8. Modifications will start to happen and eventually there will be an accepted "way" to make mods to the engine, suspension, etc on an '8 just as there is on an RX-2, 3, 4, 5 and 7 (gen 1, 2 and 3).

totally off topic
FWIW, the Mazda/Eunos Cosmo (that had the 3 rotor 20B engine) has an ECU that is tied to the Auto transmission so that even keeping the stock engine management but swapping to a manual requires (a) a replacement non-factory ECU (as the Cosmo was auto only) or (b) somehow tricking the ECU into believing that the auto is still there. (b) is very, very difficult.

[0] The email from MoTeC says DC generator - interesting.
[1] which could be interesting on 235 section tyres
[2] Say good bye to your roadworthyness (in addtion to having a "for race use only" ECU)
[3] Many manufacturers are taking this view with their ECUs. To take one example I have read that the GenIII V8 ECU in Holdens is able to sense when the air intake or exhaust is changed. It adjusts timing, fuel metering etc to take power back to factory levels.

 

Correct. The RX-8 has a generator, not an alternator.
This is pretty easy to understand when you look at the factory wiring diagrams, which I now have.

Its like we have returned to the 1960's VW production in a way.:p

 

Great info L&L. I love my dash cluster and would hate to loose it. Damn that stock ECU!

 

New fuel and ignition maps are the only practical way to go at the moment. I went looking down a similar path with the Wolf 3D EMS. Too much of the car goes the way of the dodo

I'll be very interested to know what a full mazdaspeed engine upgrade would involve and obviously how much it would cost.

 

kev

The only system that i would consider is one that piggy backs the existing ecu , and i think ihave found a great local system i cant disclose it as yet as it is currently being manufactured and wont hit the maeket till january 2004 .

However i have contacted other managenent system manufacturers and i am tryng to learn as much as possible before i consider doing any changes to my baby .
as YOU HAVE READ MOTEC PRAISED THE RX8 AND SAID THAT THERE ARE NO EASY WAYS TO VASTLY IMPROVE IT , the mazda engeners have done their work well but id love to get another 50kw on my rx8 if possible then i would be in rx8 nirvana.

michael

Thanks to the replies guys.

 

Guys, just released last week. The Mazdaspeed RX-8 (Japan only) has a "modified" ECU as per the technical details. This means it will have a part number & with that part number. It can be ordered & purchased.

Expect it to be expensive though ($5K??) as any Mazda part will be.

Aftermarket shops such as RE-Amemiya are working hard on thier own modified ECU. Its still a bit away but will happen. Those should be around the $3000 area (exchange) when they become available if I know my RE-Amemiya pricing....

Saru.. In REgards to the Eunos Cosmo. Been there, done that. Not that hard once you understand..........:D

 

Yes, Mazda seem to have done their homework on this one.

When I read about Helmholtz resonant tuning and the amount of work that went into the design of the intake system, it goes to show just how much effort and thought has been spent extracting as much NA power out of this engine as possible.

While aftermarket intakes/exhausts etc. may yield small gains, I fear that the only way we will ever see anything even close to an extra 50kW is through forced induction. Bring on the turbo and SC kits!

 

Translation: There's a substantial restriction in the inlet path for reasons other than power. 95kPa is nearly 1psi below atmospheric which is a huge restriction for an NA car.

As an aside "stand-alone" ECU's can be piggy-backed. I know it sounds strange, but the majority of aftermarket ECU's can share the crank signal, the rest just need to be buffered. I ran my last FD on an aftermarket ECU for fuel/ignition/turbo control and the stock ECU for idle,AC and OMP control. This is what I would do (assuming I didnt want to wait for a PFC).

-pete

 

I'm not so sure that there is a restriction in the inlet path. Remember that the whole intake system uses Helmholtz resonant tuning (gotta love that word).

Anyways, the whole principal behind this type of tuning is that when the plenum chamber (in this case, the air filter chamber) resonates, it creates low pressure, which promotes maximum airflow into the chamber. Air will always move from a high pressure to a low pressure. The larger the pressure differential, the faster it moves.

So if the presure in the inlet path is 1psi below atmospheric, then it probably proves that the Helmholtz tuning is working exactly the way it was designed to - by creating lower pressure in the inlet system than outside.

 

Head hurting now, but…

… bad software approach, but I can understand why Mazda have done it!

Makes me wonder what will happen if I am driving along at 120kph and transient sunspot activity zaps the ECU

 

The I guess you'd get to find out what sort of Transformer an RX8 is

 

Is that like the Heimlich Maneuver? :p

 

GUYS

Its starting to commpute , if you catch my drift .

cheers

michael

At least this time i believe i have managed to add some wortwhile serious information into the forum even though i didnt understand a large portion of it.

KEV TIMBO , stop laughing i can hear you from here .

 

L&L, to be as serious as I can be, it tells me very clearly there is no "early adopter" advantage on tuning the 8, just a lot of risk.

(sheepishly) .. besides, there's no way I want more power, given I was pinged yesterday for speeding (and it was a big one, too -- bugger!)

(thinks: must check out lease deals on Fiat Panda -- hmm, perhaps it even comes in a diesel) :D

 

I believe LINK make a piggy back capable system - think tyey're Kiwi ... must be in their nature

Anyway, a little more power and zing, plus an exhaust that tells you what the engine's doing at higher revs - but remains mild at low revs is all I'm after.

The "timbo express" example is typical of what'll happen to me with too much power.

L&L, we're laughing with you buddy

 

Saru, what you have heard a load of BS. (I had a GenIII before the '8. Stock 180 odd rwkW, Exhaust/Intake/Edit = 235 rwkW). All the ECU does is adjust the LTFT and STFT (Long Term and Short Term Fuel Trims) to get the O2 (aka mixture) correct. When you modify the intake or the exhaust, after a couple of WOT blasts these have been "Trimmed" to optimium, and you ECU has learnt the new exhaust etc. One aspect of tuning is to adjust that target AFR's to get them closer to ideal than what a stock tune is.

My preferred method of tuning is to alter the enrichment/timing maps in the ECU, not trying to trick it with some piggyback item. One of the original ways of tuning early EFI cars was to pop a resistor across the MAF output to "trick" the ECU that there was more/less air going into the engine, so it compensated the fuel accordingly. With some careful experimintation, you could get a mixture that would give better power. Tuning has come a long way since then. The RX'8 sure is differently mechanically than a reciprocating engine, but it still has the same requirements - air, fuel at the right time and volume, and spark at the correct time. That is what the ECU does in a nutshell.

L&L - The MoTec is a very good unit, and capable of being tuned by many experienced race engine tuners (PowerTorque, for example). But I wouldn't reckon you need one unless it is for a race car, where you can afford to loose all the other niceties, such as the dash etc.

The MAP (Manifold Absolute Pressure) of 95 kPa is a little low. This needs to be as close to atomoshperic as possible, which is normally a tad over 100kPa (unless a cyclone is around ). This indicates there may be some restriction in the intake, but that does not necessarlity mean throttle body or MAF. Personally, I wouldn't want to change it too much, as it sounds like a good job has been done on the variable tract design. First of I would put in a KingDragon air cleaner (only cause I chose KD over a K&N on my SS).

Unless we hook up a dyno, such as the DynoLog to the ODBII port on the '8, or we use something like EFILive, we won't know what the MAP really is. 97/98 is a better figure.

I always wonder how "optimal" these Renisis engines have been designed anyway. And don't forget - once you start increasing output, you compromise longevity.

Anyway - some practical information from my experience

Cheers,
Hymee.

(Insert :teach: smilie here )

 

Timbo

Hey i would have though a man with as many talents as yours could have sweet talked his way out of a speeding fine what happened to all your good one liners ?

HYMEE, thanks for your wise words of wisdom you are a grill legend in your own lunchtime,( ment in a nice way)

Timbo kev would have seen red and talked his way out of the parking ticket .

I was also stopped , for speeding but not booked (its not what you know its who you know.)

Michael

 

When the MAN with real dark wraparound sunglasses gets out of the (unmarked) SS, pulls on his (Gestapo style) leather peaked cap, and marches forward, pad in hand, it's no time for one liners

PS: am thinking my previous calculations of 8's speedo accuracy (~5% optimistic) were themselves pessimistic, that's the best I can say from the whole experience :o

 

I'm still confused about the generator vs the alternator - does this have any other impacts....

I'd suggest the loss of cluster is about the display not the functionality .. well at least I hope not ...

R

 

Hey Timbo ...

So what was the displayed speed vs the radar??

 

Is that like saying "As an engine tuner I make a good grill?" (meant in a curious sort of way - hehehe)

So - How do ya know??

Cheers,
Hymee.

 

As long as L&L doesn't start telling you how much he likes your bar ... then I think you'll be safe. :D

 

I'd reckon the speedo reads almost 10% over pinged speed -- but don't ever rely on that!

(practices innocent look in mirror):p

 

Hymee, if your tuning is anything like your grill, we will not fail to be impressed. Take another bow