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:

http://img.photobucket.com/albums/v5...clag/step1.jpg

Step two, remove the fusebox cover and acquaint yourself with the fuse diagram:

http://img.photobucket.com/albums/v5...clag/step2.jpg

Step three, with the engine off, remove the 60Amp ABS/DSC fuse, start the car and preform the run.

http://img.photobucket.com/albums/v5...clag/step3.jpg

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!!!!!!!! :)

or just push the DSC button for 10 secs to disable it .......

Doesn't work, ABS is still active and will still activate.

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.

interesting...this wouldnt be needed if the 8 is equiped with abs but no dsc correct?

yes it does work - did when I dynoed anyway .
but your idea is probably better in that you don't need to keep remembering to disable it .

This is needed for every RX8.

What gear do you use?
I think you should be using 5th because it's 1:1 ratio in the 8, but holy shit, you're going to be doing 147mph

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).

lol, that would explain why my rear was acting wierd on the dyno.....

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.

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

for what I got from the dyno run, its probably the ABS more than the DSC/TSC........but hey, I am probably wrong

yank the ROOM fuse too...

The room fuse? That is awkward, does this supply power to these systems too?

Chris

i should have clarified thats for people not running an external engine management system... it will set the fuel trims to 0 and disable the WBO2 sensor so it can not build any fuel trims

..racing beat suggests doing this for competition events and dynos

ahhh interesting, but if I do that my car would likely go kaboom

never pulled it on mine :dunno:

Yeah, there is no need. I don't know where this myth got started - probably a residual from the early HP-denial days.

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.

Where did you measure the voltage from MM? The Abs/DSC relay?

its on racing beats web page... since you called pettit a bunch of amatures, racing beat is probably just a bunch of n3wbs then :squint:

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 .....

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.

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.

Wow. Nicely put. Run what you brung. I like that.

I had my 8 during the dyno / horsepower conspiracy or "HP denial" days as MM puts it. It was painful. I like this "just dyno it and what it says is what it is" philosophy.

I think that the dyno is so entrenched in the minds of the typical clueless performance consumer that they will buy anything that is papered with results that can be sold as significant.

It is a measuring tool. If you use it to measure shit, the only thing you will know for sure is how much shit you have.

Yes, they say you can pull the room fuse, but you put it back in before you dyno.. Also, they say 1% loss of power, so your looking at 1-2 whp difference.. Hardly anything to worry about or needed duing a dyno run. Especially if you dont pull it on a base run & any other time, then the number increase will still be the same. So what is the point?

The PCM will not set significant fuel trim instantly. It takes time and it isn't necessarily adverse to power.

a) I said it was useless to do if your running an external engine management system
b) if you don't do it, you sure as hell better not try comparing your own dyno runs on different days to see the effects of mods since your no longer comparing apples to apples... in NA mods a few hp here and there is actually significant when looking at mods that only gain a few hp. God all help us if we want any kind of consistency in our dynos.

...didn't someone on this forum have a sig that was something like
3hp from a REVi intake $300
7hp from resetting the ecu priceless

that philosophy leads to such things as intercoolers being iced down with CO2 fire extinguishers, dynos done on freezing days and not corrected for temperature, dry ice on intakes, exhausts uncorked, oil and water pressures adjusted to meet someone's agenda, tire pressures adjusted to meet wanted outcomes, dyno information being wrongly inputted, fans being used or not used...

...if your not going to do a legit dyno that is repeatable, then your wasting your money

^ that's a great point. How many people cheat? Most! The one's that don't, make excuses when their numbers are lower than they wanted. People run high octane race fuels or alcohol at dynos when they don't on the street and then use the excuse "it was for safety". That's crap.

I don't see how pulling a fuse is a bad thing or cheating. An n/a engine can only make so much power. If it's consistent, that's all that counts. That's the important thing. It isn't the total number.

Dynoing a car IS done when the car is in an undrivable state. The front wheels don't move, there is no wind resistance, and it's strapped down. It doesn't get any more undrivable or unrealistic than that. I just don't see why there's such an argument and why anyone is so hellbent that their method must be the only correct one. Just pull the fuse and dyno it. It's easy to do. If you don't want to do this, push and hold the button in. Big deal. Pick one. It's your car.

I really want to see 2 different dyno sessions with each method now. I want to see one dynoed with the button pressed and held. Dyno 3 times back to back to back. Then go back in a week and repeat. Compare numbers. Do the same thing with the pull the fuse method. Use the same car. Compare results between both for consistency. The total power number isn't important. Consistency is. That's what I want to see. If one method consistently produces a higher power number on an n/a car it would actually be the more accurate one to use anyways.

Someone try this and post the results.

That's all fine and good, but my original point was that there is some misunderstanding of how the DSC/TCS actually works and what happens when you push that button.
The whole "cheating" thing was an aside.

Really, all one needs to do it datalog the timing, injection and throttle position to see if the PCM is interfering.
I datalog these things at all times (driving, dynoing, parking, whatever) and I can tell you conclusively what the PCM does and does not like.

EMU logs it ALL - just doesn't modify it in closed loop.

Refresh my memory.

My bad Ray - but FYI to anyone curious about Jeff's statement.

The EMU logs gather all the sensor info from all engine speed and loads - so you can get really interesting findings once you have a ton of the information organized.

Lol. Yep. True.:doh:
I logged that area, but I never really paid much attention to it since the likelihood of popping the motor there is pretty slim. Usually I'm still in "stomp on it mode" at that point and between the PCM's adjustments and the acceleration map, there is a lot of transition going by in that second that the RPMs are below 3500.

BTW - you can force the PCM into open-loop whenever you want with the EMU as it stands right now.
I'm not sure of the benefit particularly, but wherever you have an "ON" cell in the NCVS map, the PCM will be in open-loop, regardless of load.

I have a bunch of fun datalogs that might be useful. I've been driving the car in a fashion that might be considered "uncharacteristic" of me lately. Lots of crazy transition in and out of full and partial boost at all kinds of weird load points (like part throttle to 7200 RPM and then stomping on it or "pumping" the throttle all the way through the RPM band up to the rev limit - stuff that makes the driver look like a retard, which, according to his SO, he is).
I also have several where I bog the car down to 2k in 6th and tromp on it all the way until I feared for my life and the validity of my driving permit.

Email em - and I'll plug them in.

BTW - I looked back in the software - I think I found it..... :lol:

I need to do a cross compare view of the old and new tunes - adding to the list of enhancements.

I totally agree, which is why I think that we need a standard way of dynoing the rx8, ideally all the dyno charts we have on this site would be on the same day on the same dyno. But with different dynos, different ambient temps, and different ECUs comparison remains difficult.

I have seen some dynos where even without the button + 8 seconds press power remains unaffected. This leads me to believe that there is still variability in the sensitivity of the wheel speed sensors and ECU control in different cars. Just like some folks running a catless midpipe show no CEL even though so many others do.

Until I see a oscilloscope reading of the ABS/DSC relay to be sure that it is drawing no power during a dyno (meaning its inactive) I am going to assume that its still doing something at some level even if you give it the system fault (button +8 seconds). Lets start getting some consistency in our dynos by doing a simple unplug.

You don't need to monitor the DSC/TCS. Why don't you guys get this?

If you log the throttle position, you will see that the PCM does NOT interfere. This is the only engine input the PCM has in relation to the DCS/TCS.
The ignition timing and injector pules width are also similarly unaffected.

If you suspect that the PCM is messing with your dyno sessions, why don't you just log it? sCANalyzer, CANScan or whatever. It doesn't matter.
Anything that can show the throttle position will show you what is going on.

I log through my e-Manage, so I get the raw data and that TPS doesn't move an iota on the dyno.

As subtle as the PCM might seem in certain situations, it is not so in regards to the DSC/TCS.

Its that simple.

On that note, does the PCM limit throttle opening when the engine is cold and is that refelcted in PCM data logs?

Yes and yes.

and when its hot/ overtemp. and yes

ask anyone who's spiked the top of the temp guage while on the dyno.:banghead:

Doing back to back runs on a RX8 without cooling down is a recipe for destruction. Put a big fan in front of the car and let it run for as few minutes between runs.
Trust me.

Vince

I wanted to note that in my case while I was monitoring the TPS doing the dyno the throttle did get closed by the ECU when the car passed 6000rpms, this happened more severely/earlier the higher the gear, in third I could get a good run up to around 6500 before it closed the throttle. And this is with an Int-X and button pushed for 10sec.

When I had the EMU installed it would retard timing and enrich the mixture until the car lost power if the fuse was removed because it couldn't control the TPS anymore so it had to find another way to keep the driver from "killing" himself. If I left the fuse in and pushed the button for 10sec it would just close the throttle.

I have yet to try the car with the Int-X and the fuse removed, I have faith that this will eliminate the issues or I will have to find another way around the system(i.e.temporary mechanical throttle body).

Any other thoughts, anyone?

Chris

Yeah, its a giant heater when it is moving.
Its a furnace standing still.

What year is your car?

I have dynoed OEM and with both versions of the e-Manage and have seen no such interference.
Is your MAF in the normal location with the Int-X?
I know from looking at your EMU tuning (the "1000ccMOD_OctaneBoost.EM2" file) that the PCM was going to freak on the dyno because of what you were doing with the AFM map.

especially after a long slow parade drive and you drive straight over and onto the mobile dyno and they forget the fan:banghead:

All of you, shut up !!!!!

Im gonna go dyno my car after this week, suppose to do it last week but shit ass Clutch Bracket broke in the *Right* time, took them 3 days to fix it, got my car back on friday, too late.

and this coming week I have finals and shit work bugging me like crazy.

Gonna do it the xmas week I guess. I will try the *DSC button* method first. 1 hour unlimited pulls for 120 bux (aye...), weather is gonna be cold.

After that I will do another pull after the new year using the *Pull fuse* method. Alright ?

that will be pointless doing it on different days

Won't be "pointless", but it won't quiet the dyno Nazis.