If you have Dyno'd an RX-8...
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From: Boulder County, Colorado
Originally posted by RX-8 friend
Canzoomer found that here in winter he had to start at 3-4k RPM. Anything higher would cause the limp mode as it had too much wheel spin. This was with the stage 1 mod., however. Without you might do better at a higher RPM.
I think you'll find it trip at 3-4 sec. of spin, but check to see. Be interesting if it's different from car to car. We found there are levels of "ECU worry". Some show no lights yet reduce power. Some show lights that go off if you just drive around the block. Some show lights that require battery disconnect for hours to remove.
Canzoomer found that here in winter he had to start at 3-4k RPM. Anything higher would cause the limp mode as it had too much wheel spin. This was with the stage 1 mod., however. Without you might do better at a higher RPM.
I think you'll find it trip at 3-4 sec. of spin, but check to see. Be interesting if it's different from car to car. We found there are levels of "ECU worry". Some show no lights yet reduce power. Some show lights that go off if you just drive around the block. Some show lights that require battery disconnect for hours to remove.
Originally posted by RX-8 friend
Quick fix! Want to dyno your car? Before pulling on the dyno, remove the bolt holding the ABS sensor in each rear hub. Back the car on the dyno. Crawl under there and carefully pull the sensor out of the hub and secure it to a non-moving part with tape. Do your dyno runs, then crawl back under there and re-insert the sensors, pull off the dyno, and reinstall the bolts.
Better fix for racers later.
Quick fix! Want to dyno your car? Before pulling on the dyno, remove the bolt holding the ABS sensor in each rear hub. Back the car on the dyno. Crawl under there and carefully pull the sensor out of the hub and secure it to a non-moving part with tape. Do your dyno runs, then crawl back under there and re-insert the sensors, pull off the dyno, and reinstall the bolts.
Better fix for racers later.
Originally posted by Omicron
Good info, and interesting, since with my car as soon as the rears slip the car the "wiggly lines symbol" lights up. But the insidious thing is that I'm not sure any warning lights indicate when the car has gone into limp mode.
Good info, and interesting, since with my car as soon as the rears slip the car the "wiggly lines symbol" lights up. But the insidious thing is that I'm not sure any warning lights indicate when the car has gone into limp mode.
Originally posted by Omicron
Yeah, mine even lights up briefly when I do a hard shift from 1st to 2nd and break the tires loose.
Yeah, mine even lights up briefly when I do a hard shift from 1st to 2nd and break the tires loose.
The situation I describe on the dyno happens when we already are "DSC OFF". It is impossibly to do anything on the dyno with it on.
These cars don't make enough power to warrant strapping them down. When we get to something like 240 or 250kW and above at the wheels is when they start to drive themselves up out of the rollers. I guess it really is a torque thing - as they tend to need to strap auto's down more than manuals.
It is great hearing different experiences for different folks! This forum is really great for that.
Cheers,
Hymee.
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From: Boulder County, Colorado
Originally posted by Hymee
Have you got DSC turned OFF when this happens? I have only ever seen that when DSC is ON.
Have you got DSC turned OFF when this happens? I have only ever seen that when DSC is ON.
These cars don't make enough power to warrant strapping them down.
It is great hearing different experiences for different folks! This forum is really great for that.
Originally posted by Omicron
I disagree - I wouldn't risk my car on the dyno not strapped down... too much of a chance for something to go wrong and the car go crashing through the wall, perish the thought!
I disagree - I wouldn't risk my car on the dyno not strapped down... too much of a chance for something to go wrong and the car go crashing through the wall, perish the thought!
Cheers,
Hymee.
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From: South Florida
I have experienced wheelspin at 4000 RPM and thereafter noticed a reduction in power with the DCS turned off, It seems like the car is getting choked and the RPMs take longer to rev? somethings going on here! Why can't Mazda just install a high heat cat or let us do it, then they could put everything back to normal! it just dosen't make any sense why Mazda would build this type of car and just sit there and allow this to happen!
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By using the old horsepower calculator:
http://www.douglevinmotorsports.com/HP_calc.htm
And entering the following:
15.18 et
93 mph
3050 pounds
This equals 192 wheel horsepower according to the trap speed
And also 173 wheel horsepower according to the ET. That seems about the average the RX-8 is making on the dynojet, between 170 and 190 wheel horsepower.
Thor.
http://www.douglevinmotorsports.com/HP_calc.htm
And entering the following:
15.18 et
93 mph
3050 pounds
This equals 192 wheel horsepower according to the trap speed
And also 173 wheel horsepower according to the ET. That seems about the average the RX-8 is making on the dynojet, between 170 and 190 wheel horsepower.
Thor.
Then there is that other old rule of thumb about wheel HP being about the same as engine kW.
177 rwHP ~ 177 fwkW
Would be interesting to compare to a G-Tech or a MrDyno measurement.
Cheers,
Hymee.
177 rwHP ~ 177 fwkW
Would be interesting to compare to a G-Tech or a MrDyno measurement.
Cheers,
Hymee.
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From: Edmonton
ABS Sensor ID
If you look at the hub with the wheel off you will see a wire going down to it from the inside fender. On the rear there are three bolts holding this assy., two for the cable and one for the sensor (right in the wheel hub). If you remove that bolt you can wiggle out the sensor. It's magnetic (variable reluctance device). Clean it off with a rag before reinserting it. They love to collect rusty iron filings.
If you look at the hub with the wheel off you will see a wire going down to it from the inside fender. On the rear there are three bolts holding this assy., two for the cable and one for the sensor (right in the wheel hub). If you remove that bolt you can wiggle out the sensor. It's magnetic (variable reluctance device). Clean it off with a rag before reinserting it. They love to collect rusty iron filings.
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From: QUEENSLAND
I AGREE WITH RX8FRIEND
THE ONLY WAY TO SOLVE THIS PROBLEM IS TO FIND A WAY TO BYPASS OR FOOL THE COMPUTER MANAGMENT SYSTEM TO THINKING THAT WHENEVER WE PUT AN ADD ON THAT IT IS OK TO HAVE IT. ALL THIS WITHOUT EFFECTING THE DSC AND ABS CAUSE IF WE DON'T THAN THE CAR IS GOING TO KEEP GOING INTO LIMP MODE.
I WOULD SAY THE FOCUS ON IMPROVING THE 8 IS TO FIRST WORK OUT A MANAGEMENT SYSTEM THEN DO THE REST AS IT'S LIKE BYING ALL THE ACCESORIES FOR YOUR COMPUTER WITHOUT THE COMPUTER
THE ONLY WAY TO SOLVE THIS PROBLEM IS TO FIND A WAY TO BYPASS OR FOOL THE COMPUTER MANAGMENT SYSTEM TO THINKING THAT WHENEVER WE PUT AN ADD ON THAT IT IS OK TO HAVE IT. ALL THIS WITHOUT EFFECTING THE DSC AND ABS CAUSE IF WE DON'T THAN THE CAR IS GOING TO KEEP GOING INTO LIMP MODE.
I WOULD SAY THE FOCUS ON IMPROVING THE 8 IS TO FIRST WORK OUT A MANAGEMENT SYSTEM THEN DO THE REST AS IT'S LIKE BYING ALL THE ACCESORIES FOR YOUR COMPUTER WITHOUT THE COMPUTER
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From: South Florida
Hey Guy's, I didn't want to sound like I was complainig too much about the limp mode thing, because even with it happening, I still love my car! Good luck to those of you who will be doing the work to get around this tear in the achilles and thank you, because we will need it. Hey, Mazda, CAN YO HEAR US!
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From: Hungary
An idea about fooling a correct signal, why not connect the two rear sensor wires and connect them to only ONE of the sensors?
Of coarse the sensors must have a common ground though. If it's a symmetically driven sensor system then it's just not the way to go.
This may sound problematic at the sensors (long wire etc.) but should be a piece of cake at the ECU box.
Any thoughts?
Of coarse the sensors must have a common ground though. If it's a symmetically driven sensor system then it's just not the way to go.
This may sound problematic at the sensors (long wire etc.) but should be a piece of cake at the ECU box.
Any thoughts?
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From: Boulder County, Colorado
Canzoomer and company are working on this, and reportedly have a fix theoretically worked out. But getting their Stage I mod out the door to all us anxious customers is priority #1 right now, so I suspect this won't get worked out until after the first of the year.
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From: Boulder County, Colorado
Judge, from what I have heard, the limp mode triggers even when you disable the DSC and TCS by holding the button down long enough to get the car-with-squiggly-lines dash light. Apparently the ECU "decides" that you must not have really meant to disable it if it gets lots of delta between the front and rear wheel turn rate.
There is no doubt that you have gotten AWESOME 60 foot and 1/4 mile times, but if the limp mode is indeed triggering, your times might be able to be even better if the car was prevented from going into limp mode. Canzoomer and company have repeatedly seen this mode happen on the dyno, and he thinks that it triggers when you get more than about 3 seconds of wheelspin, DSC/TCS disabled or not. So this begs the questions: When you launch, how long do your back wheels spin?
There is no doubt that you have gotten AWESOME 60 foot and 1/4 mile times, but if the limp mode is indeed triggering, your times might be able to be even better if the car was prevented from going into limp mode. Canzoomer and company have repeatedly seen this mode happen on the dyno, and he thinks that it triggers when you get more than about 3 seconds of wheelspin, DSC/TCS disabled or not. So this begs the questions: When you launch, how long do your back wheels spin?
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From: Lebanon, NH
Omicron,
I think Judge Ito would know if the TCS interferred with his run. I have triggered it once with DSC/TCS disabled (5 sec press & hold).
I was fooling around and did a long burn out (~5 seconds) and when the ECU stepped in it felt like I hit a brick wall. The wheels instantly stopped spinning and the revs dropped to a more reasonable level.
It also put it into limp mode, which I was able to reset by shutting the car off then restarting it.
I think Judge Ito would know if the TCS interferred with his run. I have triggered it once with DSC/TCS disabled (5 sec press & hold).
I was fooling around and did a long burn out (~5 seconds) and when the ECU stepped in it felt like I hit a brick wall. The wheels instantly stopped spinning and the revs dropped to a more reasonable level.
It also put it into limp mode, which I was able to reset by shutting the car off then restarting it.
Last edited by Speed Racer; Dec 24, 2003 at 02:29 PM.
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From: South Florida
yeah, it sounds like Judge Ito has the proper tire Psi for max grip, maybe that's why he is not triggering limp mode, yet breaking transmissions! Hey Judge, not that I want to break my tranny, but what tire PSI do you use for those launches?
I his 60' time is 1.9, then he hasn't hit it yet (aka the 3 second theory). I've only ever seen it happen on the dyno. (ABS warning and TC warning lights, "DSC OFF" goes out). Lets call the "car-with-squiggly-lines" the Traction Control (TC) warning light from now on 
Cheers,
Hymee.
Cheers,
Hymee.
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From: Katherine, NT
Can you be in limp/safe mode without any indications in the dash? My understanding is that limp mode is indicated by either the ABS light or the CEL. I've never seen either of these on the road - and only the ABS light on the dyno. Does this mean I've never been in safe mode on the road?
Wildcard,
Canzoomer reckons that opn the engine dyno for long enough you eventually get a CEL. Perhaps his runs have been longer than ours - but you have seen how it works. Mark set an appropriate ramp rate for the gear we were in. The full test was probably about 10 to 20 seconds would you reckon? You have one on tape don't you?
Cheers,
Hymee.
Canzoomer reckons that opn the engine dyno for long enough you eventually get a CEL. Perhaps his runs have been longer than ours - but you have seen how it works. Mark set an appropriate ramp rate for the gear we were in. The full test was probably about 10 to 20 seconds would you reckon? You have one on tape don't you?
Cheers,
Hymee.
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From: Katherine, NT
Our dyno runs were done in 4th from a start speed of 75km/h with a ramp up to 195km/h. The ramps took 12 seconds. I checked on my camera.
On some of the runs, the ABS light was aleady on before the ramp. On the last run, it was off and Mark watched to see exactly when the ABS light came on. It came on at about 7000rpm, which was precisely the point on the curve where the mixture got richer and power reduced.
On some of the runs, the ABS light was aleady on before the ramp. On the last run, it was off and Mark watched to see exactly when the ABS light came on. It came on at about 7000rpm, which was precisely the point on the curve where the mixture got richer and power reduced.
