Diy- How To Dyno The Rx8
11-29-2007, 07:33 PM
#1
The Professor
Thread Starter
Diy- How To Dyno The Rx8
Okay, as some of you may know, the RX8 is a very picky car, its onboard electronics and advanced Dynamic Stability Control(DSC) and Traction Control System (TCS) are top of the line.
Being so, the RX8 was made to safely take you on your daily routine trips as well as keep you safe while taking that turn too fast on the track.
These systems work in conjunction with the ABS system to selectively brake each wheel that detects slip as well as pull engine throttle if it detects too much of a wheel slippage problem.
The main reason people dyno with such low numbers (besides bad spark plugs, bad coils) is because the car detects that two wheels are spinning at a perceived 100mph while the other two are stationary. The computer then activates some level of the ABS/DSC system to either brake the back wheels, or refrain from giving full power to the back wheels. Both of which spell low numbers on the dyno.
So here is the DIY to pull the ABS/DSC fuse, completely disabling the system for the purposes of dyno testing the car.
This is the ONLY way to get high and consistent numbers from the RX8.
Step one, find the engine compartment fusebox:
Step two, remove the fusebox cover and acquaint yourself with the fuse diagram:
Step three, with the engine off, remove the 60Amp ABS/DSC fuse, start the car and preform the run.
THE best way to get high numbers out of the rx8 is to run 3 pulls back to back to back with no cool-down period. The 3rd pull in this series is the highest number that your rx8 is capable of achieving. If you would like to try again, wait until the engine is completely cool before re-running the series of 3.
Good Luck! Put up some high Numbers!!!!!!!!
Being so, the RX8 was made to safely take you on your daily routine trips as well as keep you safe while taking that turn too fast on the track.
These systems work in conjunction with the ABS system to selectively brake each wheel that detects slip as well as pull engine throttle if it detects too much of a wheel slippage problem.
The main reason people dyno with such low numbers (besides bad spark plugs, bad coils) is because the car detects that two wheels are spinning at a perceived 100mph while the other two are stationary. The computer then activates some level of the ABS/DSC system to either brake the back wheels, or refrain from giving full power to the back wheels. Both of which spell low numbers on the dyno.
So here is the DIY to pull the ABS/DSC fuse, completely disabling the system for the purposes of dyno testing the car.
This is the ONLY way to get high and consistent numbers from the RX8.
Step one, find the engine compartment fusebox:
Step two, remove the fusebox cover and acquaint yourself with the fuse diagram:
Step three, with the engine off, remove the 60Amp ABS/DSC fuse, start the car and preform the run.
THE best way to get high numbers out of the rx8 is to run 3 pulls back to back to back with no cool-down period. The 3rd pull in this series is the highest number that your rx8 is capable of achieving. If you would like to try again, wait until the engine is completely cool before re-running the series of 3.
Good Luck! Put up some high Numbers!!!!!!!!
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Rx8tj (04-24-2020)
11-29-2007, 07:39 PM
#3
The Professor
Thread Starter
11-29-2007, 07:43 PM
#4
The Professor
Thread Starter
I've done like 6 dyno sessions, with the fuse pulled, without the fuse pulled, button pressed once, button pressed and held 10+ seconds.
And in end, this is the only way to get consistent numbers where you can be sure some electronic system isn't interfering with the power delivery.
And in end, this is the only way to get consistent numbers where you can be sure some electronic system isn't interfering with the power delivery.
11-29-2007, 08:32 PM
#9
The Professor
Thread Starter
I usually dyno in 4th, gear isn't really important on a dyno when going for horsepower because regardless of gear the load placed on the engine by the dyno is the same in "horsepower" mode (hp vs engine rpm)
Just as if you were going up a hill on a bike, whether you spin the pedals 30 times in a low gear getting up the hill or push really hard making the pedals go around once you are using the same total calories. Which is what the dyno in "horsepower" mode is looking for, the amount of raw power output.
If you do the math in the end it comes out to be the same. Dynos have different modes though, and some of them do measure acceleration which would show a difference in gear (hp relative to ground speed).
Just as if you were going up a hill on a bike, whether you spin the pedals 30 times in a low gear getting up the hill or push really hard making the pedals go around once you are using the same total calories. Which is what the dyno in "horsepower" mode is looking for, the amount of raw power output.
If you do the math in the end it comes out to be the same. Dynos have different modes though, and some of them do measure acceleration which would show a difference in gear (hp relative to ground speed).
11-29-2007, 08:40 PM
#11
The DSC/TCS "fail" (hold the button for 10 seconds) completely disables the system.
Pulling the fuses is not needed.
I've scoped the power through the system with it disabled (not to mention logging the TPS and ignition timing - the only control the PCM has over power - on my dyno runs, showing no interference) and some wild driving and it is fully off. With the button press, the system is truly off.
Inconsistencies in the dyno pulls are not a result of leaving the fuses in place.
If the PCM was truly concerned with the function of the DSC/TCS, it would fail-safe in either failure mode and it does not.
Pulling the fuses is not needed.
I've scoped the power through the system with it disabled (not to mention logging the TPS and ignition timing - the only control the PCM has over power - on my dyno runs, showing no interference) and some wild driving and it is fully off. With the button press, the system is truly off.
Inconsistencies in the dyno pulls are not a result of leaving the fuses in place.
If the PCM was truly concerned with the function of the DSC/TCS, it would fail-safe in either failure mode and it does not.
11-30-2007, 12:34 AM
#12
I have to agree with staticlag that if you dont pull the fuse it will not dyno cosistently. With the pushing for 10sec I was able to get maybe one run if it was done quickly. The moment the car saw that I was going at that speed standing still it would not let me dyno a full run after that. I would have to drive the car off the dyno and then bring it back so it would operate properly. It might not be the TCS/DSC, it might be the ABS triggering something too. I am not sure I just know that there is a difference between the pushing the button and removing the fuse, at least with the INt-X installed. With the stock ecu still in control it doenst matter what we tried, we couldnt get a consistent reading past the first run. If we had to stop the first run for some reason, which is the case most times, that would be it for the day. Any ideas.
Chris
Chris
11-30-2007, 12:33 PM
#16
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..racing beat suggests doing this for competition events and dynos
12-02-2007, 04:30 PM
#20
The Professor
Thread Starter
Well, there really is no way to tell for sure that just pushing the button for 10 seconds will disable the system completely on everyone's car.
It may for yours, it may not for someone else. I do trust MM and I do trust the oscilloscope though
The only thing that absolutely makes sense is to unplug the thing. You're not going to wire a new ceilining light with just the power switch in the "off" position, you're not going to replace your radiator fans with just the ignition off, you're not going to replace a circular saw blade with it still plugged in.
So why should you dyno with the ABS/DSC still plugged in? It literally takes two minutes do to this.
It may for yours, it may not for someone else. I do trust MM and I do trust the oscilloscope though
The only thing that absolutely makes sense is to unplug the thing. You're not going to wire a new ceilining light with just the power switch in the "off" position, you're not going to replace your radiator fans with just the ignition off, you're not going to replace a circular saw blade with it still plugged in.
So why should you dyno with the ABS/DSC still plugged in? It literally takes two minutes do to this.
12-02-2007, 05:12 PM
#23
oh bugger - I should be dead
Even though I don't think it is 100% necessary - I do agree that it makes sense . I know when I did mine that I forgot to push the DSC button for the second session after lunch . Your method could have prevented a c**k up .....
12-02-2007, 06:16 PM
#24
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this is what they say exactly...
In developing this flash, we disconnected the Front Oxygen Sensor so that we had a stable, unchanging platform. Otherwise, the system would continually develop new trims that we would have to chase. Of course, it is not appropriate for you to do this (except in racing) because the system NEEDS the oxygen feedback information to correct the engine’s operation at light to moderate throttle settings. The fact is, in our experience, the PCM will usually build a 2% to 3.5% top level trim, which means the engine is running that much richer than best power mixture. In general, this is a small amount, and will only cause a fraction of 1% loss of power. On the other hand, if you don't want to run with this factor (i.e. racing applications), you have two choices:
1. Disconnect the Front Oxygen Sensor (at the top of the bell housing), pull and reinstall the "ROOM" fuse (in the left kick panel) to eliminate the 3 trim levels, and the PCM will NEVER build a fuel trim (it will turn on the "Check Engine" light, but that's all).
2. As an alternative, you can simply warm the engine prior to a competition run, shut off the engine, pull and reinstall the "ROOM" fuse, and begin your competition shortly after starting the engine. In this way, the engine never sees the "cruise" operation it needs to build the trim level.
In developing this flash, we disconnected the Front Oxygen Sensor so that we had a stable, unchanging platform. Otherwise, the system would continually develop new trims that we would have to chase. Of course, it is not appropriate for you to do this (except in racing) because the system NEEDS the oxygen feedback information to correct the engine’s operation at light to moderate throttle settings. The fact is, in our experience, the PCM will usually build a 2% to 3.5% top level trim, which means the engine is running that much richer than best power mixture. In general, this is a small amount, and will only cause a fraction of 1% loss of power. On the other hand, if you don't want to run with this factor (i.e. racing applications), you have two choices:
1. Disconnect the Front Oxygen Sensor (at the top of the bell housing), pull and reinstall the "ROOM" fuse (in the left kick panel) to eliminate the 3 trim levels, and the PCM will NEVER build a fuel trim (it will turn on the "Check Engine" light, but that's all).
2. As an alternative, you can simply warm the engine prior to a competition run, shut off the engine, pull and reinstall the "ROOM" fuse, and begin your competition shortly after starting the engine. In this way, the engine never sees the "cruise" operation it needs to build the trim level.
12-02-2007, 06:20 PM
#25
So, why would you do any of that for a dyno run.
Oh yeah, I remember.
To cheat.
Why would you dyno a car in an undrivable state?
More importantly, it is only applicable on a vehicle that still has its OEM PCM in the loop in its original tune.
If you have the Int-X or if you have the ability to re-flash the PCM and change the A/F targets, then it is an irrelevant (and stupid) trick.
Oh yeah, I remember.
To cheat.
Why would you dyno a car in an undrivable state?
More importantly, it is only applicable on a vehicle that still has its OEM PCM in the loop in its original tune.
If you have the Int-X or if you have the ability to re-flash the PCM and change the A/F targets, then it is an irrelevant (and stupid) trick.
Last edited by MazdaManiac; 12-02-2007 at 06:30 PM.