It is pretty interesting - looking back and searching forum I see that almost every one of folks who underwent this 200 cell cats upgrade process either with AWE or Fabspeed or else then initially complained about some oddities in car behavior. Ian posted that his car goes 'out of tune' with time and becomes flat, Cattman car did not go properly at all until ECU was reset, etc, etc.

I wonder now with quite provocative question - was all that aftermarket exhaust stuff even worth doing?
My car right now also is doing something odd and inconsistent - looks like timing fluctuates from time to time so sometimes it pulls like crazy and then for no visible reason in same exact situation it acts flat. I will try to reset ECU again to see what is it - but it is definitely pretty annoying and did not happen at all with stock exhaust. It is truly odd to be driving on 3rd gear, floor gas and see your car hardly feeling it.

So, whoever here completed those cats upgrades - did you have any burn-in period with any inconsistent behavioral problems on your cars after exhaust upgrade or was it straight up perfect and nice and even no ECU reset was needed?

I am just trying to collect some statistics here on who got what. Nothing can be easier than to roll back to original stock but it is not the issue here. I am just concerned with what my ECU is doing as it does not seem right to me at all so I want to understand if it an individual glitch or a part of some common pattern.

 

No issues. Upon install, never did an ECU reset. Everything works as advertised.

Maybe it's the design of the xPipe in general versus regular aftermarket 200 cel cats? Just posing a question as well as I do not have an answer and am not qualified to answer any questions regarding the xPipe design versus regular aftermarket cat design.

 

You have PM

 

Ian,
please post your convo. I would like to follow this thread as I will be putting on awe cats to go with my cans. Interested in the outcome

 

There is no conspiracy here - Ian and several others suggest I should clean up MAF sensor and then check its performance.

 

Great Advice, did that work?

 

Well, I just drove to get a can of CRC MAF cleaner from autozone, did 30 miles this morning total, so, well... Either another ECU reset worked properly or my car just got scared to death by perspective of another attempt to brutally abuse her but it now runs more then perfectly. Goes like a rocket.

I start to suspect other thing, which also may be related partially to MAF, perhaps - every time I notice severe degradation in performance outside temperature was close to 90. This morning it was about 70. There is definitely a correlation there because every single time it was pretty hot when I drove her and sensed torque degradation, so it may not even be exhaust. Plus engine was definitely on different tone - more bass roaring than usual.

Dan from vividracing suggested adding octane booster next time in hot weather after I sense another episode of 'flattness' and, well, if octane booster will eliminate timing issue - it means it is just hot air what causes this. It is not clear what to do about it though... I am just not sure why would 20 degrees diff cause such an effect but it was the only fluctuating element now I am able to see. Nothing else was changed.

By the way, does anybody have a link to proper MAF cleaning procedure? I know where is it, I know I need special wrench to get assembly out. What next - should I spray it while it is in assembly or should it be taken out? I hope not as taking out MAFs is usually quite a delicate business...

 

Here's a summary of some info and the discussions I've had with both Utkinpol and Cattman regarding a problem I experienced with my car. I hope neither Utkinpol or Cattman mind me posting this here - I thought it was relevant to the thread and others on here.

In short, my car had been running really oddly. It would lose performance over time and felt like it was pulling timing as it both went and sounded 'flat'.

I eventually got the problem sorted but it was certainly a complicated fix!.

I firstly took my car to a local tuner with a dyno to try to figure out what was going on. They discovered that the car was pulling timing (about 5 degrees - this doesn't sound much but the car is only meant to run about 24-25 degrees of timing at full throttle/peak rpm). They also found that the lambda sensors were correcting the MAF far too much - the long-term fuel trims were at about 7% from memory - and unusually, the MAF was telling the ECU that MORE air was going into the engine than was actually the case. Odd as MAF's usually fail lean. This problem was also causing the car to run too rich at full throttle.

I was really surprised to find out from the tuner that the lambda sensors can be correcting a mis-reading MAF by up to about 20% before throwing a code! He told me that an engine in this condition would be running dreadfully but the ECU would still show a healthy car. In fact, the tuner said that if the MAF is functioning but not accurate, it can even prevent the car from adapting properly and it was likely this that was causing it to pull timing.

A new MAF and a reflash of my ECU with the latest stock map for my car (the latter simply a precaution) sorted the problems and it now runs very well. The long-term fuel corrections are under 2% - well within acceptable tolerances - rather than the 7% with the faulty MAF and the car now runs 24-25 degrees of timing as it should.

So it seems that the MAF sensors are given a little too much latitude to be out-of-calibration before they throw a code - something I think could be a possible reason why some cars just don't run quite right.

The simple way to check this is to hook your car up to an ODB-II tester and look at the long-term fuel trims. (You don't need PIWIS or Durametric for this as fuel-trims are part of the mandated emissions information that has to be readble by all ODB-II equipment). If they're more than a percentage point or 2, this could indicate a faulty MAF or maybe an air leak.

The good news is - to go back on topic - that none of the issues with my car had anything to do with high-flow cats. The AWE system on my car just works as advertised - it was other sensors causing the problem.

Finally, there's a common myth that putting free-flowing exhausts on a car somewhow reduces back-pressure at low rpms and reduces torque. This is not the case at all. There is little or no back-pressure from a stock exhaust at low rpm anyway. Think about this. Your engine can probably produce no more than, say, 90BHP at WOT at 2000rpm. If the exhaust was already restricting the outflow of gasses at 2000rpm/90BHP, it would strangle the engine completely at 6500rpm and 355BHP. In fact the engine would never get to 6500rpm or produce 355BHP! So fitting free-flow cats on their own will leave low rpms where they are and increase power higher up the range when the stock exhaust does become more restrictive.

Changing headers however, can change torque characteristices markedly. Different pipe lengths and diameters change how the exhaust scavenges gas from the cylinders. Another topic for another day!

 

The key element there above I think is 'new MAF'. From what I know - usually after cleaning one would have 50%/50% chances for sensor to die. So it may be easier to get a new one instead.

I wonder - suncoast sells then by $350 something. Does Bosch make OEM MAFs we could use? No way this thing should cost almost $400, it is a very simple sensor.

 

Here is how to clean -


http://www.renntech.org/forums/index...opic=414&st=20

http://forums.rennlist.com/rennforum...t=maf+cleaning

also

https://www.6speedonline.com/forums/...f-cleaner.html

 

I did the headers, 200 cell cats, mufflers and O2 sensors on my '99 C2 Cab at the same time. The battery was disconnected during the install. I reconnected the battery and drove the car for a few miles. There may have been a little bit of "hesitating" or a flat spot in the torque curve initially, but after a few miles, it went away. I never had a CEL or any other problem related to the installation of the aftermarket parts. YMMV.

 

From what I know usually engine outs back pressure is calculated and maintained by selecting exact diameter of header`s intake pipes and that piece alone actually controls back pressure. I am not even sure how much influence cats produce there, if any. I just remember that every custom headers guys in racing garage were modding were calculated out - too wide pipes were bad, too narrow pipes were bad too. And no one ever cared about cats.

 

No issues with my AWE/HJC 200 cel Cats

Jason

 

Could you repost the links? Looks like they got truncated by the board software.

Thanks!

 

open up last MAF CLEANER link - look into post #9. surprisingly it has same links google gave me.