Originally Posted by gracer7-rx7
(Post 12471432)
Is it 'normal' for the inside of the ACV to be 'dirty'?
Thanks. |
I suspect there is some kind of spec for leakage between the port air system (and maybe split air too) and the actual ACV and they eventually get gummed up no matter what. There's always going to be some rough combustion at times (especially at idle on these engines) due to overlap between intake and exhaust.
Remember that back when all this stuff was designed (basically 70s and 80s), emission warranties were not very long. Nowadays emission components have to last 120k-150k miles to comply with modern regulations. So significant carbon buildup isn't surprising. It's the same thing you see on EGR valves etc (and the FD did have EGR in '93). |
Hello, @arghx
I'm bringing this thread back and also re-read this thread. (Good thread, by the way) I was going to private message you, but other people in the future can benefit from this too. (If they buy expensive emission parts and want to keep them for a while.) ;) I'll get straight to the point, I bought an expensive catalytic converter from FEED and want to keep it healthy. My previous bonez cat blew out; it was old, the car is running rich, and the air pump is not connected, but I will get it tuned and run the air pump with the new cat. Here is the list of mods and new parts that are on my car (or going on my car shortly) before I ask my questions and bounce ideas around: Greddy V-mount New OEM fuel injectors Water Injection, AEM 99-spec twins with all-new hoses and all-new solenoids in the rat's nest New Air pump out of the box Fujita Engineering twin catalytic converter EGR delete, along with deleted solenoid in the rat's nest Power FC, (removed wires "AWS Solenoid," "EGR Switch," and "EGR Solenoid," but going to put back the "Split air bypass".) I read the Power FC can run the air pump if I have the wire "Split air bypass" connected in the harness to the ECU and not cut like everyone else says to do. (Correct me if I'm wrong that the Power FC can't run the air pump) Also, I read that water injection can help with carbon buildup, which is the only reason I have it. My theory so far is to have the air pump installed with the Power FC and ensure the ACV is working while the system is getting water injection to fight carbon buildup. Basically, I have 2 goals, keep my catalytic converter healthy as long as possible and minimize exhaust smell as much as possible. (I'm not trying to pass emissions btw since there is none in my state) If there is anything that you recommend, I would be happy to listen. |
Originally Posted by CREEPENJEEPEN
(Post 12539594)
Power FC, (removed wires "AWS Solenoid," "EGR Switch," and "EGR Solenoid," but going to put back the "Split air bypass"
https://cimg9.ibsrv.net/gimg/www.rx7...874594b7b2.jpg the Red arrow is the split air bypass, its an add on for the US. the actual work is done by the big diaphragms which both markets have and the PFC runs. we cut the 4 wires because they have different functions between US and Japan the Green arrow is the Relief, it chooses if the air pump air is relieved to the air cleaner, or keeps going in the valve. the other diaphragm is the Switching Valve, it Switches the air pump air from "Port Air" to "Split Air" as far as keeping the cat happy, the stock cat wants to be kept under about 650c, over that it starts melting. i would assume FEED is using a metal converter, and those typically have a higher temp limit, i think the SARD ones are 1100c, which is higher that you can hit with a rotary, which is nice. the JDM setup has a temp sensor in the cat, so there is a provision for EGT there for best performance, i'd think if you tuned the thing so it hit the AFR targets in the base map you'd be really in the ball park, best performance in a converter is when its in closed loop dithering around 14.7:1 afr, which is what the stock, and PFC maps do until the EGT gets high enough that they start adding fuel to keep temps down. if you did have a test, you'd tune it so it hit the values on the base map, under the same conditions as the test, and make adjustments from there. for example the California test is 15mph in 2nd gear and then 25mph in 3rd gear, so i'd log data for that, and if it tested high for something, its easy to tweak the AFR/timing. i don't think water injection will make any difference here at all |
Thank you for that informative response; I'm still learning something new every day and recently jumped into learning about emissions because of this expensive cat, lol. Yeah, I'll have my tuner adjust for the optimum AFR for health of the engine and the components attached to it. Not chasing the edge of tuning to make crazy HP. My theory is that water injection is mainly for carbon build up; it's always steam cleaning the engine.
You're right, I should have thought that those pins go nowhere, I remember now, (de pinned them 3 years ago). Here are my 3 questions after reading your response: 1. First, will having an air pump with a PFC do anything on a USDM rx7 since one diaphragm is completely disabled with the PFC? 2. Is "Port Air" to "Split Air' important for cat health and smell? 3. Do I need to modify anything so the air pump can work correctly with the PFC? (Example would be removing vacuum lines or unplugging anything on the ACV) |
Originally Posted by CREEPENJEEPEN
(Post 12539768)
1. First, will having an air pump with a PFC do anything on a USDM rx7 since one diaphragm is completely disabled with the PFC?
2. Is "Port Air" to "Split Air' important for cat health and smell? basically what happens is that the engine is tuned to run as lean as it can without misfires, but due to the way its constructed this is like 12:1 or so, but the converter needs to see 14:7:1, so they add the air pump air. 3. Do I need to modify anything so the air pump can work correctly with the PFC? (Example would be removing vacuum lines or unplugging anything on the ACV) |
So getting the air pump working is all about getting the AFR inside the cat lean enough so it's actually oxidizing. Otherwise it's can clog up with unburnt fuel, and (speculating here without elaborate equipment) occasional deceleration fuel cuts basically throw a bunch of hot air from the engine into a bunch of unburnt fuel in the cat and cause a lot of reactions inside heating it up.
You need to keep your EGT's down under boost as well. WIthout having a fast action EGT probe in the inlet of the cat it's hard to know what's going on. Usually 900-950C inside the catalyst is about the most they can take without accelerated wear, so it's best to keep the temperature coming out of the manifold below that if you can. Generally speaking though, I'd keep AFR's between about 10.5:1 and 11.0:1 , with occasionally going slightly leaner. I know that's on the rich side, and possibly costing power, but there's a reason why stock tunes run so rich. I'm not going to tell you to advance timing to keep EGT down because a Bonez cat is a lot cheaper than rebuilding a motor, so a good safety margin on spark timing is preferred for reliability. |
Originally Posted by arghx
(Post 12539962)
So getting the air pump working is all about getting the AFR inside the cat lean enough so it's actually oxidizing. Otherwise it's can clog up with unburnt fuel, and (speculating here without elaborate equipment) occasional deceleration fuel cuts basically throw a bunch of hot air from the engine into a bunch of unburnt fuel in the cat and cause a lot of reactions inside heating it up.
You need to keep your EGT's down under boost as well. WIthout having a fast action EGT probe in the inlet of the cat it's hard to know what's going on. Usually 900-950C inside the catalyst is about the most they can take without accelerated wear, so it's best to keep the temperature coming out of the manifold below that if you can. Generally speaking though, I'd keep AFR's between about 10.5:1 and 11.0:1 , with occasionally going slightly leaner. I know that's on the rich side, and possibly costing power, but there's a reason why stock tunes run so rich. I'm not going to tell you to advance timing to keep EGT down because a Bonez cat is a lot cheaper than rebuilding a motor, so a good safety margin on spark timing is preferred for reliability. |
Normally under WOT or heavy acceleration your hottest temperatures are going to be pre turbo. When you start talking about an air pump being involved, and deceleration fuel cuts (backfires etc), then you'd literally need to drill into the cat. Measuring pre turbo is a useful indicator, although it won't tell you if there are some reactions going on inside the cat causing it to get significantly hotter. You probably won't get a fast enough reading just eyeballing a gauge. We have to look at it from the perspective of a hobbyist driving an old car around a few thousand miles a year. From that point of view it starts becoming cheaper to just replace cats than to do the work to keep them going a long time.
Here's a diagram from a paper studying emissions that shows how various EGT sensors are placed in a downpipe (in this case no turbo, just a nonturbo 4 cylinder exhaust manifold). UEGO indicates a wideband and HEGO are narrowbands. These various sensors were used in this study to measure the impact of the reactions throughout the exhaust system, and each "TC" (K-type thermocouple, found on most EGT gauges) measures temperatures through the exhaust stream. There was an air pump as well, just not pictured. In your case you basically have temperatures on the upstream portion of the exhaust system (left side of the picture) but not inside the actual cat. https://cimg3.ibsrv.net/gimg/www.rx7...b52a018a00.png |
Originally Posted by arghx
(Post 12540715)
We have to look at it from the perspective of a hobbyist driving an old car around a few thousand miles a year. From that point of view it starts becoming cheaper to just replace cats than to do the work to keep them going a long time.
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Originally Posted by CREEPENJEEPEN
(Post 12541090)
Unfortunately the catalytic converter that I bought from FEED was almost 2,900USD. (Twin Cat, same air flor as a midpipe) Trying everything I can to keep it healthy, and this thread is helping out a lot. I came across an excellent program for the Power FC, called "FC tweak" and I believe it has everything I need to help keep the correct ratio of air to fuel for the cat. Installing a bunch of sensors in the cat seems more of a learning curve. I'd rather have the AI built into FC tweak take over than have someone like me, that's not an engineer or tuner, take over. You seem like you went to school for this subject or taught it; you're very knowledgeable.
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The FC Tweak software automates stuff that a lot of tuners are doing in their head or in Excel. (Full disclosure: I was given a free copy of it, but have not done an extensive evaluation).
That being said... there are inputs and there are outputs. The output is the catalyst bed temperature, which is directly related to the life of the cat. The input is air, fuel, and spark. We can make certain assumptions about what spark timing and AFR for example will do inside the cat, but without direct measurement it's all estimation. That being said, direct measurement is not an easy thing for a home hobbyist, so you do the best you can with rules of thumb and good tuning. So having good tuning helps, but you can't reduce cat temps under load without giving something up. You can't add fuel to lower cat temps without reducing power/fuel economy relative to not caring about exhaust temps. You can't advance spark to reduce cat temps without increasing the risk of knocking, etc. Also,the airpump affects cat temps, but its control is mostly hard coded into the PFC and the stock ECU. |
the early JDM FD's had a temp sensor in the cat, N3A7-18-760B. PFC is setup to use it, but the US cars have something different
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Originally Posted by arghx
(Post 12541120)
The FC Tweak software automates stuff that a lot of tuners are doing in their head or in Excel. (Full disclosure: I was given a free copy of it, but have not done an extensive evaluation).
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Edit: I received a reply back from Xavier and adding the airpump isn't possible since it's hard coded into the powerfc. Dang.
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Originally Posted by CREEPENJEEPEN
(Post 12541329)
Edit: I received a reply back from Xavier and adding the airpump isn't possible since it's hard coded into the powerfc. Dang.
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Originally Posted by j9fd3s
(Post 12541340)
but it works fine as is, so you don't need to do anything
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it doesn’t just come on for initial cold startup only like on an RX8?
I always thought it was only used to get the cat up to temp for that reason, weird. . |
Nope, FD air pump runs at low RPM/idle. It disengages during acceleration and high RPM.
Dale |
Originally Posted by TeamRX8
(Post 12542348)
it doesn’t just come on for initial cold startup only like on an RX8?
I always thought it was only used to get the cat up to temp for that reason, weird. . the MSP just runs like a normal engine.... |
thanks for edumacating me, makes sense
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Originally Posted by TeamRX8
(Post 12542414)
thanks for edumacating me, makes sense
. Mazda figured out that they needed the side ports really early, like before the FD was on sale, so the test bed was an NA miata with an early 13B-MSP, which is a neat idea for a fun car |
Can I use the newer ACV from the later 4, 5, and 6 series FD's in my 94 USDM FD?
From what I've read: https://www.rx7club.com/attachments/...v_actuator.jpg https://cimg0.ibsrv.net/gimg/www.rx7...8d482a5cbb.jpg The JDM ACV has a spot for the split air bypass solenoid valve, but it's not being used. https://cimg1.ibsrv.net/gimg/www.rx7...654eab6a36.jpg Once more, we're skipping a solenoid valve. Right here is where the 'Relief 2' solenoid valve would fit.The newer ACV versions ditch two valves: the split air bypass and the Relief 2. The only valve they keep from the old to the new ACV is the port air bypass. So, why can't I fit the newer ACV into my '94 USDM FD? It seems like the relief actuator, which is vacuum-controlled, should already be relieving the air pump, why do we need a separate "Relief 2 solenoid valve"? Also, we might not even need the split air bypass valve if it's supposed to work off the switching actuator, which is also vacuum-controlled. The later ACV models are still available new, so it would be convenient if I could use them. |
there is also a rebuild kit, Mazda USA doesn't know about it, so you need to source from Japan but it exists
Part number is FDXU-13-991 https://cimg5.ibsrv.net/gimg/www.rx7...b0aefccc35.jpg |
That’s cool, it’s better then getting a new ACV for 350-400 dollars.
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