I found this in another thread on inaccurate dyno readings:

"In addition, we have determined that, in order to prevent damage to the catalytic converter and the entire driveline, when the PCM determines unusual operating parameters such as excessive slip in the drivetrain from the front to the rear wheels, it causes a rich high-RPM mixture and retardation of the timing. All these items combine to cause apparent considerable horsepower loss.
The RX-8 uses a very advanced engine management system. Besides precisely controlling the operating parameters of the engine, self-preservation (of both the engine and the catalytic converter) is also considered.
The engine management system continuously monitors all engine functions and adjusts accordingly. For example:
Under heavy load acceleration, the timing is retarded and the fuel mixture richened to reduce the likelihood of pre-ignition or spark knock. If spark knock is encountered, a knock sensor senses the condition and further retards the timing. Gradually timing is advanced and fuel mixture leaned after the load is reduced.
A second reason for fuel enrichment is that when timing is retarded, exhaust temperatures increase; a richer mixture lowers the exhaust temperatures and reduces the chances of damaging the catalytic converter.
The ABS hydraulic unit/control module (HU/CM), or the DSC HU/CM for cars with DSC, determines vehicle speed by comparing the speed of all four wheels. If two are turning and two are stationary, it will still compute a speed but senses that the car is experiencing excessive wheel spin. To protect against engine or catalyst damage:
The engine management system compares the throttle opening, gear selection (determined by engine speed and road speed) charging efficiency and engine coolant temperature to determine the driving condition.
Since the car is under heavy load, in a tall gear (testing is usually performed in third or fourth gear), with a wide throttle position angle (wide open), spark timing is reduced and the fuel mixture is richened to reduce the occurrence of spark knock and to reduce catalytic converter temperatures."

I shortend it, So does this mean that if we install a High Flow CAT or mid-pipe and the CEL comes on because the ECU doesn't read the CAT sensor right it will switch fuel maps and actually cause us to loose power because it thinks the CAT is being damaged?

 

I would have put this in the Aftermarket Performance and MazdaSpeed. I think more people might see/answer.

 

A High-Flow cat isn't much more than a gimmick, IMO. They operate exactly like OEM Cats. I doubt the car would be able to know which type of cat is installed.

 

That article only shows that the ECU monitors engine and transmission sensors in determining fuel enrichment for cat protection. If that is the case, there is nothing to determine what is actually going on at the cat - let alone if there is one at all.

 

But people have reported after installing a HF CAT they have to reinstall the a sensor or the CEL light comes on and w/ some HF CATs they can't reinstall the sensor. Any mod can move it to the aftermarket section, it proball ywill do better there.

 

Of course, if the oxygen sensor is not installed, the car will through a CEL... that's common sense... wouldn't it make snse to re-install the oxygen sensor back into place, so that the ECU "thinks" that the cat is intact?

 

This is how the PCM is Monitoring the CAT.

Switch Ratio Method (1996 - 2004)

In order to assess catalyst oxygen storage, the monitor counts front and rear HO2S switches during part-throttle, closed-loop fuel conditions after the engine is warmed-up and inferred catalyst temperature is within limits. Front switches are accumulated in up to nine different air mass regions or cells although 3 air mass regions is typical. Rear switches are counted in a single cell for all air mass regions. When the required number of front switches has accumulated in each cell (air mass region), the total number of rear switches is divided by the total number of front switches to compute a switch ratio. A switch ratio near 0.0 indicates high oxygen storage capacity, hence high HC efficiency. A switch ratio near 1.0 indicates low oxygen storage capacity, hence low HC efficiency. If the actual switch ratio exceeds the threshold switch ratio, the catalyst is considered failed.

Index Ratio Method (some 2001 and beyond)

In order to assess catalyst oxygen storage, the catalyst monitor counts front HO2S switches during part-throttle, closed-loop fuel conditions after the engine is warmed-up and inferred catalyst temperature is within limits. Front switches are accumulated in up to three different air mass regions or cells. While catalyst monitoring entry conditions are being met, the front and rear HO2S signal lengths are continually being calculated. When the required number of front switches has accumulated in each cell (air mass region), the total signal length of the rear HO2S is divided by the total signal length of front HO2S to compute a catalyst index ratio. An index ratio near 0.0 indicates high oxygen storage capacity, hence high HC efficiency. An index ratio near 1.0 indicates low oxygen storage capacity, hence low HC efficiency. If the actual index ratio exceeds the threshold index ratio, the catalyst is considered failed.

General Catalyst Monitor Operation

If the catalyst monitor does not complete during a particular driving cycle, the already-accumulated switch/signal-length data is retained in Keep Alive Memory and is used during the next driving cycle to allow the catalyst monitor a better opportunity to complete, even under short or transient driving conditions.
Rear HO2S sensors can be located in various ways to monitor different kinds of exhaust systems. In-line engines and many V-engines are monitored by individual bank. A rear HO2S sensor is used along with the front, fuel-control HO2S sensor for each bank. Two sensors are used on an in-line engine; four sensors are used on a V-engine. Some V-engines have exhaust banks that combine into a single underbody catalyst. These systems are referred to as Y-pipe systems. They use only one rear HO2S sensor along with the two front, fuel-control HO2S sensors. Y-pipe system use three sensors in all. For Y-pipe systems, the two front HO2S sensor signals are combined by the software to infer what the HO2S signal would have been in front of the monitored catalyst. The inferred front HO2S signal and the actual single, rear HO2S signal is then used to calculate the switch ratio.
Most vehicles that are part of the “LEV” catalyst monitor phase-in will monitor less than 100% of the catalyst volume – often the first catalyst brick of the catalyst system. Partial volume monitoring is done on LEV and ULEV vehicles in order to meet the 1.75 * emission-standard. The rationale for this practice is that the catalysts nearest the engine deteriorate first, allowing the catalyst monitor to be more sensitive and illuminate the MIL properly at lower emission standards.
Many applications that utilize partial-volume monitoring place the rear HO2S sensor after the first light-off catalyst can or, after the second catalyst can in a three-can per bank system. (A few applications placed the HO2S in the middle of the catalyst can, between the first and second bricks.)
Index ratios for ethanol (Flex fuel) vehicles vary based on the changing concentration of alcohol in the fuel. The malfunction threshold typically increases as the percent alcohol increases. For example, a malfunction threshold of
0.5 may be used at E10 (10% ethanol) and 0.9 may be used at E85 (85% ethanol). The malfunction thresholds are therefore adjusted based on the % alcohol in the fuel. (Note: Normal gasoline is allowed to contain up to 10% ethanol (E10)).
All vehicles employ an Exponentially Weighted Moving Average (EWMA) algorithm to improve the robustness of the FTP catalyst monitor. During normal customer driving, a malfunction will illuminate the MIL, on average, in 3 to 6 driving cycles. If KAM is reset (battery disconnected), a malfunction will illuminate the MIL in 2 driving cycles. See the section on EWMA for additional information.

 

According to dynoes that is an incorrect statement. With the CZ unit & SR Motorsports unit gains of about 5-6 hp have been seen. Unless the dyno is incorrect, there are real hp gains from a hi-flow cat unit. The hi-flow cat like an aftermarket exhaust simply reduces restriction, and lessens back pressure. Simple concept. Of the people that have gotten hi-flow cat units, I have only heard of a few that have had CEL problems. The ones with the issue are the ones who got the midpipe (essentially a straight tube replacing the cat & resonator). In this case the O2 sensor detects that there is no cat on board and CEL comes on accodingly. Some people have gotten the Casper O2 sensor "fooler" unit.

 

I've dyno'd with 'hi-flow' cats...frankly, look at them. They look identical to OEM cats. The mesh inside has the same-sized openings, etc... I'd love to see a same-day dyno of a mostly stock car using OEM, then Hi-Flow.

 

The mesh screen inside has nothing to do with the restriction of the unit. It's the cell #'s in the cat that counts. I've seen hi flow cats on my 911 that looked identical from the outside (same size, same look, same mesh screen on entry & exit), that until you've cut them open you won't notice a difference. One was a 400 cell cat (OEM), the other was a 200 cell cat, and another was a 100 cell cat. All looked the same until you popped them open. Hate to call BS, but show us/post your dyno. What hi-flao unit are you running ? Appearances are meaningless. The K&N filter look huge, but consistently delivers the smallest gain in hp compared to the RE or HKS intake system. There have been dynos posted by other people on this board that have gained hp from the CZ/random technology unit, not the manufacturer claims (these tend to be optimistic) but actual drivers. I'm bringing my car in on Monday to put in the SR Motorsports Flywheel, SR Motorsports Hi-flow Cat, SR Motorsports Pullies & RE Air Intake (hawk brake pads & wheel spacers). I will do a before and after dyno, but not one after each mod (unless someone wants to pay for my $100+/hour dyno time). So we'll find out something. I'm optimistic at 8-10 hp

 

I would hope you would get a little more than that...

 

Has anyone answered the question of possible loss due to the CEL from the ECU

 

This will be interesting to see, what exhaust (cat back) do you have?

 

Racing Beat Exhaust

Horse,

I'm expecting little, so if it comes out with more than 10 hp I will be pleasantly surprised vs. expecting too much & being disappointed.