Go Go Ghetto MSP custom exhaust
- Thread starter Rainman
- Start date
OK, OK, OK....I think I get it now!
I'm going to the exhaust guy later this week to have the O2 sensor moved behind the cat. I humbly submit to the collective wisdom of my fellow MSPers.
I spoke with a service guy at Mazda who also does his own tuning on the side today. He agreed with the forum consensus. He said that if I didn't have a CEL yet I probably would soon. However, the other point he made was what bothered me the most.
As I understand him this was the point that he made. Since the 2nd O2 sensor is for high efficiency burn of remaining fuel/pollutants (i.e. to check what the cat is doing) if the cat is behind the O2 sensor, the sensor reads that the A/F mixture is too rich since the gases reaching the sensor have been untreated. The ECU then leans out my A/F mixture. Not so bad if I was stock without the flash. However, with the flash and other performance mods (including exhaust) the engine will require more fuel for the increased air coming into, and leaving the engine. The ECU leaning from the misplaced sensor magnifies this issue to the point of being too lean. This causes my engine to run hotter.
My EGT is located in my DP. Cruising around town my temps are 800-900 or so. When I take it easy on the highway at 120 kmh they are about 1150-1200. When I mash it on the highway (160 kmh/100mph) the EGT soars to 1400+ even when I am not in boost. With the estimated 200 degree drop in temp from the cylinders to the DP this is really an EGT of 1600-1700+. This is BAD for our engines....as I understand it...LOL (not really laughing though). So extended highway driving or extended hard runs are NOT a good idea until I get the situation fixed. I feel like I have been crippled.
There is a silver lining though. Since I will move the O2 bung behind the cat, I can have the one in front of the cat plugged with a screw-in plug rather than welded shut. Subsequent dyno tuning can be done via that first O2 bung.
I knew that there was a lot to learn, but **** sometimes this s*** is worse than the anatomy and stuff that I have to know for work.
Rainman
I'm going to the exhaust guy later this week to have the O2 sensor moved behind the cat. I humbly submit to the collective wisdom of my fellow MSPers.
I spoke with a service guy at Mazda who also does his own tuning on the side today. He agreed with the forum consensus. He said that if I didn't have a CEL yet I probably would soon. However, the other point he made was what bothered me the most.
As I understand him this was the point that he made. Since the 2nd O2 sensor is for high efficiency burn of remaining fuel/pollutants (i.e. to check what the cat is doing) if the cat is behind the O2 sensor, the sensor reads that the A/F mixture is too rich since the gases reaching the sensor have been untreated. The ECU then leans out my A/F mixture. Not so bad if I was stock without the flash. However, with the flash and other performance mods (including exhaust) the engine will require more fuel for the increased air coming into, and leaving the engine. The ECU leaning from the misplaced sensor magnifies this issue to the point of being too lean. This causes my engine to run hotter.
My EGT is located in my DP. Cruising around town my temps are 800-900 or so. When I take it easy on the highway at 120 kmh they are about 1150-1200. When I mash it on the highway (160 kmh/100mph) the EGT soars to 1400+ even when I am not in boost. With the estimated 200 degree drop in temp from the cylinders to the DP this is really an EGT of 1600-1700+. This is BAD for our engines....as I understand it...LOL (not really laughing though). So extended highway driving or extended hard runs are NOT a good idea until I get the situation fixed. I feel like I have been crippled.
There is a silver lining though. Since I will move the O2 bung behind the cat, I can have the one in front of the cat plugged with a screw-in plug rather than welded shut. Subsequent dyno tuning can be done via that first O2 bung.
I knew that there was a lot to learn, but **** sometimes this s*** is worse than the anatomy and stuff that I have to know for work.
Rainman
Last edited:
Update
Went to a local tuner guru today to ask questions prior to the exhaust revision (booked for Thurs pm). Popped the hood when we were talking together and noticed that some of the wire protector on the front of the engine (passengers side) was completely melted potentially confirming the theory that the engine was running lean and therefore too hot. Until Thurs pm I am babying the car and keeping RPM below 3500 at all times. Damn, that is slow.
This got me to thinking on the way home from work. Several companies sell downpipes that have NO cats on them. These are for "racing" only, but plenty of people are using them on the streets. You have to buy a small electronic component with these (and other) cat-less exhausts to get rid of the CEL. But if there is no cat, then these other engines would technically be in the same situation as my own (since the cat is behind the sensor), at least from the veiwpoint of the ECU. If that was the case, the all of these engines would be running lean and therefore running hot.
I had an EGT so I was able to pick up on this trend. Together with the information from the service guys we could figure out that engine temps were in a really bad range. However, not everyone who has these types of exhausts has an EGT or an A/F meter. Running your MSP hard without this kind of monitoring would allow you to run your MSP under extremely harsh conditions, some of which might prove too much for the MSP to handle. There seem to have been a rash of MSPs unexplainedly blowing up of late. Could this be a contributor to this trend. Another local MSP just blew his engine last week and he had only just installed his EBC. He had a 2.5" Greddy exhaust, CAI, hardpipes, boost guage and A/F guage. With the A/F guage he should have been able to figure out what was going on, but stranger things have happened.
Rainman
Went to a local tuner guru today to ask questions prior to the exhaust revision (booked for Thurs pm). Popped the hood when we were talking together and noticed that some of the wire protector on the front of the engine (passengers side) was completely melted potentially confirming the theory that the engine was running lean and therefore too hot. Until Thurs pm I am babying the car and keeping RPM below 3500 at all times. Damn, that is slow.
This got me to thinking on the way home from work. Several companies sell downpipes that have NO cats on them. These are for "racing" only, but plenty of people are using them on the streets. You have to buy a small electronic component with these (and other) cat-less exhausts to get rid of the CEL. But if there is no cat, then these other engines would technically be in the same situation as my own (since the cat is behind the sensor), at least from the veiwpoint of the ECU. If that was the case, the all of these engines would be running lean and therefore running hot.
I had an EGT so I was able to pick up on this trend. Together with the information from the service guys we could figure out that engine temps were in a really bad range. However, not everyone who has these types of exhausts has an EGT or an A/F meter. Running your MSP hard without this kind of monitoring would allow you to run your MSP under extremely harsh conditions, some of which might prove too much for the MSP to handle. There seem to have been a rash of MSPs unexplainedly blowing up of late. Could this be a contributor to this trend. Another local MSP just blew his engine last week and he had only just installed his EBC. He had a 2.5" Greddy exhaust, CAI, hardpipes, boost guage and A/F guage. With the A/F guage he should have been able to figure out what was going on, but stranger things have happened.
Rainman
C-Bass said:
Rainman said:
Actually, the catless exhausts that have a MIL installed should be safe. The engine reads the first sensor, and adjusts accordingly, and then reads the second sensor to see if the cat is doing it's job. If you've got a MIL installed, the PCM will always think the exhaust is acceptable at the 2nd O2 sensor, and therefore will not adjust it leaner to compensate.
Also, the Greddy exhaust is Cat-back, so unless the other guy had a catless mid-pipe fabricated when he installed his Greddy, he should still have had his original cat and O2 sensor setup.
Exhaust fixed
OK. Went to the exhaust guy a day early cause I got the afternoon free at work. He changed the exhaust. He essentially re-did the whole thing because we found that the two different sized cats are because of the cross-member running underneath the car. The second larger cat (the one installed on my car) is longer and overlaps the cross member. If your engine torques too much, there is a chance that this will touch the member and rattle. Anyway, he changed the angle of the flange somewhat so that there was enough clearance between the cat and the member. Then he rerouted the cat about 4" further back behind the cat. Then he put on the flexpipe (although he noted that it would be less beneficial farther back like that). Next he refabricated the are remaining pipe with an extended over-axle bend (recall, previously it would touch here if if the car was full). Lastly, he reattached the muffler and added a 2nd empty O2 bung (for dyno tuning) just before the flex pipe. He couldn't use the original misplaced O2 bung because he had to cut if off so that the cat could be fitted as far forward as possible so that I didn't have to get a new O2 sensor wire.
Three hours later, the MSP is back in action. Louder than ever because he didn't have a plug for the empty O2 bung. I gotta pick one up tonight. Had to pussyfoot it past the speedtrap cops so that it wouldn't sound as loud as it is. Don't really notice any big changes as far as performance yet, but haven't really had a chance to hammer it. I do think that the EGT values are generally lower. I'll provide more info as things progress.
Rainman
OK. Went to the exhaust guy a day early cause I got the afternoon free at work. He changed the exhaust. He essentially re-did the whole thing because we found that the two different sized cats are because of the cross-member running underneath the car. The second larger cat (the one installed on my car) is longer and overlaps the cross member. If your engine torques too much, there is a chance that this will touch the member and rattle. Anyway, he changed the angle of the flange somewhat so that there was enough clearance between the cat and the member. Then he rerouted the cat about 4" further back behind the cat. Then he put on the flexpipe (although he noted that it would be less beneficial farther back like that). Next he refabricated the are remaining pipe with an extended over-axle bend (recall, previously it would touch here if if the car was full). Lastly, he reattached the muffler and added a 2nd empty O2 bung (for dyno tuning) just before the flex pipe. He couldn't use the original misplaced O2 bung because he had to cut if off so that the cat could be fitted as far forward as possible so that I didn't have to get a new O2 sensor wire.
Three hours later, the MSP is back in action. Louder than ever because he didn't have a plug for the empty O2 bung. I gotta pick one up tonight. Had to pussyfoot it past the speedtrap cops so that it wouldn't sound as loud as it is. Don't really notice any big changes as far as performance yet, but haven't really had a chance to hammer it. I do think that the EGT values are generally lower. I'll provide more info as things progress.
Rainman
C-Bass said:
Your experience with a custom fit sounds like an ordeal to me!! If I compare it with mine (Camo Tuning in Montral, specialized in rally cars for quite a long time), your guy doesn't seems that "professional" to me. I must say that I got there with pictures of the Ion setup that was in Turbo magazine and others of the Apex downpipe. Anyways, I think they should have known better to start with. JMO
The meaning of the Y in DIY!
True enough, but it was partially my fault. When I had the car done, I left it up to the tuners at my garage because they already had the car. They were preparing it for the Import Nite show and as part of that preparation they took it to the exhaust guy. I didn't give them any pictures of what I expected as I figured that they knew more about it than I did. They are a new shop, but decent guys that work hard. They know alot about Hondas (who doesn't...LOL), but less about other makes. I shouldn't have trusted them with deciding what to do, not that they aren't trustworthy, but as I have learned before (when a business owner), if you want something done right then do it yourself.
I really should have given them pictures of the other stuff to work from so that they had a better idea. Although, after watching the exhaust guy redo the system I can understand why he did things the way he did. First, he did leave the second O2 sensor where it was. Second he did place the second cat where it was originally. However, the first cat on our system is a shortened version of the second. This design is because of the cross-member I mentioned before. On the original system the flex bolts allow for enough motion after the connnection to the DP so that the torque from the engine is not transferred to the exhaust pipe. With these flex bolts, no flex pipe is needed. Then you have short cat, O2 sensor, pipe (6" over the cross member), and long cat.
When I took it in yesterday, he didn't have a 3" hi-flow cat in the short length. He only had the long one. This may have been his fault or my tuners fault for not purchasing a short cat (if they even make it??). Really, I should have bought the cat myself when I purchased the muffler, but again I trusted their judgment. Anyways, it took quite a bit of finangling to fit that long cat before the cross member. I am sure that when he looked at the system orignially, he figured that it would be a b**** trying to get something to fit before the cross member so he took the easy route. Replace the flex bolts with the flex pipe, get rid of the first cat, and then put a 3" high flow cat where the second cat was. Without me or the tuners present to watch over his back there wasn't anyone to say "wait a minute." Lesson learned.
In the end, the long cat didn't quite fit all the way before the cross member. The back 1/5 of it is over the cross member, but he did angle it a bit so that even with some torque it wouldn't hit the cross member. Then he put the flex pipe after the cat. Not as good as having it further forward, but it worked. So now my exhaust goes: DP-flange-long cat-O2 sensor-short length 3" pipe-3rd O2 sensor bung (for dyno tuning)-flex pipe-rest of the exhaust. I hammered it on the way home and on my way to a local show last night. I also gave it a good run this afternoon after work. So far, no creaks, no vibrations, and no clunks!
The 3rd O2 bung is unplugged as I haven't picked up a plug for it yet. This may affect the EGT values a bit, but I had it up to 150 kmh last night and 140 kmh today. Last night my EGT values maxed at 1350 at about 4K RPM and 150 kmh. It was fairly humid, but ambient temp about 25 C last night. Today, it was about 31 C ambient, so I had the fan blasting, but no AC. At 140 kmh, 3700 RPM, EGT steady at 1200. Add about 200 F to those and I'm still sitting under the 1600+ (1400 + 200 correction) I was seeing before. I think things are better. Not sure about the loss or gain of any power. However, with the O2 sensor back where it was supposed to be I have a bit of the hesitation back despite the fact that my MSP is flashed.
Rainman
True enough, but it was partially my fault. When I had the car done, I left it up to the tuners at my garage because they already had the car. They were preparing it for the Import Nite show and as part of that preparation they took it to the exhaust guy. I didn't give them any pictures of what I expected as I figured that they knew more about it than I did. They are a new shop, but decent guys that work hard. They know alot about Hondas (who doesn't...LOL), but less about other makes. I shouldn't have trusted them with deciding what to do, not that they aren't trustworthy, but as I have learned before (when a business owner), if you want something done right then do it yourself.
I really should have given them pictures of the other stuff to work from so that they had a better idea. Although, after watching the exhaust guy redo the system I can understand why he did things the way he did. First, he did leave the second O2 sensor where it was. Second he did place the second cat where it was originally. However, the first cat on our system is a shortened version of the second. This design is because of the cross-member I mentioned before. On the original system the flex bolts allow for enough motion after the connnection to the DP so that the torque from the engine is not transferred to the exhaust pipe. With these flex bolts, no flex pipe is needed. Then you have short cat, O2 sensor, pipe (6" over the cross member), and long cat.
When I took it in yesterday, he didn't have a 3" hi-flow cat in the short length. He only had the long one. This may have been his fault or my tuners fault for not purchasing a short cat (if they even make it??). Really, I should have bought the cat myself when I purchased the muffler, but again I trusted their judgment. Anyways, it took quite a bit of finangling to fit that long cat before the cross member. I am sure that when he looked at the system orignially, he figured that it would be a b**** trying to get something to fit before the cross member so he took the easy route. Replace the flex bolts with the flex pipe, get rid of the first cat, and then put a 3" high flow cat where the second cat was. Without me or the tuners present to watch over his back there wasn't anyone to say "wait a minute." Lesson learned.
In the end, the long cat didn't quite fit all the way before the cross member. The back 1/5 of it is over the cross member, but he did angle it a bit so that even with some torque it wouldn't hit the cross member. Then he put the flex pipe after the cat. Not as good as having it further forward, but it worked. So now my exhaust goes: DP-flange-long cat-O2 sensor-short length 3" pipe-3rd O2 sensor bung (for dyno tuning)-flex pipe-rest of the exhaust. I hammered it on the way home and on my way to a local show last night. I also gave it a good run this afternoon after work. So far, no creaks, no vibrations, and no clunks!
The 3rd O2 bung is unplugged as I haven't picked up a plug for it yet. This may affect the EGT values a bit, but I had it up to 150 kmh last night and 140 kmh today. Last night my EGT values maxed at 1350 at about 4K RPM and 150 kmh. It was fairly humid, but ambient temp about 25 C last night. Today, it was about 31 C ambient, so I had the fan blasting, but no AC. At 140 kmh, 3700 RPM, EGT steady at 1200. Add about 200 F to those and I'm still sitting under the 1600+ (1400 + 200 correction) I was seeing before. I think things are better. Not sure about the loss or gain of any power. However, with the O2 sensor back where it was supposed to be I have a bit of the hesitation back despite the fact that my MSP is flashed.
Rainman
thunder said:
Wow! Now we know all the story! I wish I had an EGT like you to check how things are working.... I also get a bit of hesitation sometimes but only when it very warm (which makes sense). I forgot to mention that I had bought my cat before I went to the shop (magnaflow 2.5") and I knew exactly haow I wanted done, also I stayed there so when they had questions I was there to explain. Mazda is not as well known as VW or Hondas so it's better to do our homework before 
I'm glad it worked out for you. Fo me, I felt a noticeable difference right away (probably an extra 10WHP).
I'm glad it worked out for you. Fo me, I felt a noticeable difference right away (probably an extra 10WHP).
I can see where you're coming from, but people who work on exhausts for a living should know things like this. It's not like this setup is specific to the MSP. It's fairly typical of an OBDII car. I don't see you being at all at fault. Anybody would like to think they could trust an exhaust shop to build an exhaust system that works the way it's supposed to. I'm glad everything worked out for you! Have fun with your exhaust, I can't wait for mine
Butt dyno
I didn't notice much of a difference once the exhaust was fixed. But I did notice a BIG difference between stock and custom. Can't say for sure cause it hasn't been on the dyno, but I figured about 10whp as well.
Rainman
I didn't notice much of a difference once the exhaust was fixed. But I did notice a BIG difference between stock and custom. Can't say for sure cause it hasn't been on the dyno, but I figured about 10whp as well.
Rainman
thunder said:Wow! Now we know all the story! I wish I had an EGT like you to check how things are working.... I also get a bit of hesitation sometimes but only when it very warm (which makes sense). I forgot to mention that I had bought my cat before I went to the shop (magnaflow 2.5") and I knew exactly haow I wanted done, also I stayed there so when they had questions I was there to explain. Mazda is not as well known as VW or Hondas so it's better to do our homework before
I'm glad it worked out for you. Fo me, I felt a noticeable difference right away (probably an extra 10WHP).
Diy
I kinda felt the same way, but I didn't want to lay blame where I could've changed the outcome. I got the impression that he didn't do much work on imports, however as an exhaust guy you would expect him to know his s***...especially where you can cut corners and where you can't. As it is, he charge me another $80CAN cash for the switch. I felt like driving off without paying him, but I didn't want to make this more of a problem than it was.
It is a lesson for next time. Even though I am only learning all this stuff now, I think more and more that I have do stuff myself to get it right. Alot of the stuff is not complicated. It just requires a significant time investment and the right tools. It may not look as pretty as something prefab, but at least I will understand how it works and WHY it works. That way, if it f--ks up, I can only blame myself.
Rainman
I kinda felt the same way, but I didn't want to lay blame where I could've changed the outcome. I got the impression that he didn't do much work on imports, however as an exhaust guy you would expect him to know his s***...especially where you can cut corners and where you can't. As it is, he charge me another $80CAN cash for the switch. I felt like driving off without paying him, but I didn't want to make this more of a problem than it was.
It is a lesson for next time. Even though I am only learning all this stuff now, I think more and more that I have do stuff myself to get it right. Alot of the stuff is not complicated. It just requires a significant time investment and the right tools. It may not look as pretty as something prefab, but at least I will understand how it works and WHY it works. That way, if it f--ks up, I can only blame myself.
Rainman
C-Bass said:I can see where you're coming from, but people who work on exhausts for a living should know things like this. It's not like this setup is specific to the MSP. It's fairly typical of an OBDII car. I don't see you being at all at fault. Anybody would like to think they could trust an exhaust shop to build an exhaust system that works the way it's supposed to. I'm glad everything worked out for you! Have fun with your exhaust, I can't wait for mine
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