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Two years and many dollars later, I think I am in need of a bit of help. I'm still trying to pass IM240 in Colorado (Denver area) without success. I've replaced quite a few parts putting the car back to stock + previous owner's bolt-ons, but I'm starting run out of ideas to get it to pass. New parts
Engine: OEM short block w/ ~400 miles on original OEM 94 ECU, no smoke of any color
Emissions: full new solenoid rack, OEM engine harness, full silicone vacuum line replacement, EGR/ACV/split air/AWS all installed
Ignition: plugs day before test day, OEM plug wires, OEM coil harness
Fuel: pump replaced, tank replaced, filter replaced, 2 new OEM primary, 2 cleaned and bench tested OEM original secondary, FPD replaced, no premix ever
Sensors: FC thermoswitch, thermostat, O2 sensor (Bosch), fuel thermo, oil pressure, coolant level
Also a whole bunch of other stuff unrelated to emissions PO's bolt-ons that aren't helping N3G1 99 spec turbos, Greddy Airinix intake, Bonez 3" turbo back w/ cat (marked '03?!) and split air hooked up Test day mods I think are helping
Oil change and new plugs day before, rear tires at 37psi, 30min highway driving/boosting prior to test w/ 15min wait, precontrol/wastegate pills removed
During my original test in 2021, I ran the IM240 with no split air and potentially no air pump due to the crumbling connector. All of the new parts I listed were installed but it failed CO and HC badly. The equipment inspection failure was for not having a precat after they looked at the sticker under the hood. Colorado doesn't do visuals any more, though exhaust systems are now supposed to be CARB compliant specifically.
After putting the project away for a bit, I sourced a new air pump plug and verified the air pump clutch actuation. I then removed the split air block off plate and installed a new split air tube to the cat. After burning out two years of crud in the engine and cat, I do have to say the car smells much better at idle when warmed. I was pretty frustrated to find that the result was nearly identical to the run with no split air. To make matters worse, Colorado also applied tighter HC restrictions in 2022, making the FD that much further away from passing.
I'm a bit unsure what to do next.
TPS?
I did notice the small spikes on the mild acceleration between 180 and 200 seconds and checked the TPS. The TPS is slightly out of spec in only the closed value of the narrow range sensor (1.4v vs. 1.25v spec), but I'm not sure if that is enough to get the car failing this badly.
ACV?
Prior to today's test, I did half check the ACV by disconnecting the split air tube before the one way valve and checking for air. I could feel pressurized air coming out of the tube at high idle and the air did cut off when revving the engine. That seems backwards from how Arghx's port air diagram was drawn (below), so perhaps I have something cross connected in the rat's nest. I dread pulling the ACV but will do it if port air seems to be the culprit.
Catalytic?
The Bonez cat that is on the car is the previous owners and I have no idea how long it's been on the car. In reading through the other detailed IM240 thread, my understanding is that the NOx would also be failing if the cat were in need of replacement.
Ignition?
Overall the engine seems to be pretty happy once warm. I hear very minimal exhaust "pauses" at idle. The car happily winds to redline under partial and full throttle. I do hear some "stumbling?" maybe on decel but no backfires. The car also does buck rolling on to decel, but I'm not sure if that is drive train slop related or engine related. The car also does hesitate minimally on very light throttle application, but I think that might be TPS related.
AWS interference?
One problem that for sure remains has to do with the behavior during AWS. On cold start, the car goes to high idle, then stumbles pretty hard for a few seconds until I pull it out of AWS with a throttle tap. The exhaust tip does cough up what smells like liquid gas and the plugs were wet when I pulled them. This only happens on cold start, but the car does idle smoothly at ~1k despite the throttle stop being backed out. After quite a bit of driving (45min+), the idle will settle to 800 and be smooth.
Assuming you've seen this: Passing Emmissions. I stumbled on it the other day while investigating the fuel catch can and immediately gave thanks for living in a state with a 25 year exemption.
So, you are trying to pass emissions testing with the Bonez cat? Is that correct?
If so, I'd switch to a good stock cat for the test. Most of us in CA do this.
I agree with the above, I used to live in Colorado and I barely passed with the Bonez and had to switch to stock to pass after 2 years. Not sure if the levels are more strict or not now, this was back in the early 2000s.
Assuming you've seen this: Passing Emmissions. I stumbled on it the other day while investigating the fuel catch can and immediately gave thanks for living in a state with a 25 year exemption.
I had seen that thread, but I didn't remember to block the catch can to UIM line before I headed to the testing station. I'll definitely do that on the next go around.
Originally Posted by gracer7-rx7
So, you are trying to pass emissions testing with the Bonez cat? Is that correct?
If so, I'd switch to a good stock cat for the test. Most of us in CA do this.
Yes, trying to pass with the Bonez. I would give this a try if I had access to a stock cat, but unfortunately the PO didn't include the stock one (if he had it) when I bought the car. There were posts in the other thread here https://www.rx7club.com/3rd-generati...d-out-1119012/ where other users had mentioned passing IM240 with the Bonez. I was hoping that since so many other parts had been updated to like-new, that the test would be passable with the Bonez.
I think my main concern at this point is figuring out where the richness is coming from: ACV failure, ignition failure, or injector failure. The values from the test aren't even close to passing. Based on the troubleshooting table that has been passed around in a few threads, I originally thought that the air injection was the cause. This was why I did the updates to reconnect the split air and verify that it was reaching the cat. I'm still stumped as to why this didn't change anything on the second test. The ACV has off-vehicle testing in the FSM, but I wasn't able to find a procedure to do on vehicle testing to see whether the port air was working or not.
Based on the included graphs it looks like your air pump isn't doing anything or the air isn't getting to the cat. There is no change after connecting the split air pipe.
I recall seeing something years ago about the side port on some aftermarket cats was fake with no actual opening into the converter chamber. I'm not sure if the Bonez cat was the subject aftermarket cat or not. Regardless it could be easy for you to remove the split air pipe at the cat and see if the tube does indeed penetrate the converter chamber and pass air. With the car running while it is disconnected you should feel exhaust gas pressure coming out of he tube.
I'm with the other guys on the stock cat though, it's going to be greater than any other option.
There are a few FD guys in Colorado, somebody may be willing to let you borrow one to pass
Not sure of the best way to bolt to the 3" Bonez DP/catback to the stock cat, but if anyone reading this is an FD person in CO willing to let me borrow an exhaust please PM me.
Originally Posted by Molotovman
Based on the included graphs it looks like your air pump isn't doing anything or the air isn't getting to the cat. There is no change after connecting the split air pipe.
I recall seeing something years ago about the side port on some aftermarket cats was fake with no actual opening into the converter chamber. I'm not sure if the Bonez cat was the subject aftermarket cat or not. Regardless it could be easy for you to remove the split air pipe at the cat and see if the tube does indeed penetrate the converter chamber and pass air. With the car running while it is disconnected you should feel exhaust gas pressure coming out of he tube.
I just went out to the garage to test this since you're right, no air is indeed a decent theory on why the graphs are the same.
With the car off, I tested:
1) to make sure that the 1 way valve was letting air through into the cat's direction by disconnecting it at the "1" mark and blowing through it. I was able to blow through using less force than I'd use to blow up a balloon. I also wiggled the other clamps towards the engine block to make sure none were obviously loose.
Then disconnected the end of the tube from the cat's metal pipe and started the car to test:
2) to make sure I could feel exhaust pulses from the cat as you suggested. I could both hear and feel the exhaust pulses coming from the metal tube.
3) to make sure I could feel air moving through the tube, through the one way valve, and towards where the cat would have been. With the car idling at ~1500 from the cold start, I could feel air pressure exiting the hose at about the force of a garden hose on low with your thumb half over it.
Not sure of the best way to bolt to the 3" Bonez DP/catback to the stock cat, but if anyone reading this is an FD person in CO willing to let me borrow an exhaust please PM me.
Bonez should bolt up to all the factory stuff. Unless you have had some custom pipes welded everything should bolt up. Wouldn't hurt to have both the precat and main cat, the main cat only should be enough to pass as long as its in good condition but pre cat is often necessary if everything isn't in the best of shape
Unknown if the stock air plumbing to the Bonez cat actually does anything - or whether it provides the same benefit as it does with the stock cat... With the stock cat, the composition and quantity of rare metals/materials is different and more effective than the Bonez. https://www.rx7club.com/3rd-generati.../#post12219234
Your conclusion is that the car is running rich but you don't have a wideband O2 sensor on there to measure, do you? Your conclusion is logical considering the reference material. But what about if it is "running rich" because the cat is not filtering the exhaust sufficiently?
Your conclusion is logical considering the reference material. But what about if it is "running rich" because the cat is not filtering the exhaust sufficiently?
My comment about running rich was definitely pointed at the reference material coupled with the fact that I can still catch whiffs of unburnt fuel from the exhaust, especially at startup. I agree that the forum knowledge points to using the OEM cat to pass, but there are also users reporting passing emissions with the Bonez (perhaps with a matrix in better condition than mine). I was hoping to rule out other potential culprits before spending a good chunk picking up another cat.
Originally Posted by gracer7-rx7
Your conclusion is that the car is running rich but you don't have a wideband O2 sensor on there to measure, do you?
I do have an Innovate LC-1 for my 20b that has been sitting in a box for 10 years unused which I could hook up. I'd planned to install it when I got around to restoring the interior. Assuming that I did find it running rich on the gauge, I'm still not sure what further parts in the fuel or ignition systems could be the culprit. Short of the coils, most components in those systems are new. I think the only involved sensors I didn't replace are the IAT and MAP.
Is E85 available in your area? It burns cleaner than gasoline, and ethanol's stoichiometric ratio is an easy way to make the fuel mixture leaner on our primitive stock ECU. I've seen people suggest about 1 gallon of E85 per 2-3 gallons of gasoline for piston cars. I also like the idea of adjusting the throttle position sensor, if you're able to get to the adjustment screws.
Not sure of the best way to bolt to the 3" Bonez DP/catback to the stock cat, but if anyone reading this is an FD person in CO willing to let me borrow an exhaust please PM me.
I just went out to the garage to test this since you're right, no air is indeed a decent theory on why the graphs are the same.
With the car off, I tested:
1) to make sure that the 1 way valve was letting air through into the cat's direction by disconnecting it at the "1" mark and blowing through it. I was able to blow through using less force than I'd use to blow up a balloon. I also wiggled the other clamps towards the engine block to make sure none were obviously loose.
Then disconnected the end of the tube from the cat's metal pipe and started the car to test:
2) to make sure I could feel exhaust pulses from the cat as you suggested. I could both hear and feel the exhaust pulses coming from the metal tube.
3) to make sure I could feel air moving through the tube, through the one way valve, and towards where the cat would have been. With the car idling at ~1500 from the cold start, I could feel air pressure exiting the hose at about the force of a garden hose on low with your thumb half over it.
Are you able to get help to see if the air pressure from the pump increases with RPM? Does the FSM spec air pump flow relative to RPM?
You seem close enough to the limits that replacing the cat should do the trick. If you don't want to keep troubleshooting I'd get an OEM cat, swap it in, and run the test.
Are you able to get help to see if the air pressure from the pump increases with RPM? Does the FSM spec air pump flow relative to RPM?
You seem close enough to the limits that replacing the cat should do the trick. If you don't want to keep troubleshooting I'd get an OEM cat, swap it in, and run the test.
The FSM only has a spec for cutting air at 3250rpm (which it does) and a pressure check at the air pump outlet at idle (not sure exactly how much the SST plugs the elbow). I've sent some PMs and put up an ad for an OEM cat, but I'm interested in troubleshooting in the mean time. I'm still baffled as to why the split air made exactly 0 impact. Those two final output calculations could have been from back to back runs they're so close.
Originally Posted by scotty305
Is E85 available in your area? It burns cleaner than gasoline, and ethanol's stoichiometric ratio is an easy way to make the fuel mixture leaner on our primitive stock ECU. I've seen people suggest about 1 gallon of E85 per 2-3 gallons of gasoline for piston cars. I also like the idea of adjusting the throttle position sensor, if you're able to get to the adjustment screws.
I can get E85 but I don't really like the idea of imprecisely altering the AFR, especially when the techs seem to be getting their foot into it on the 150-170 second portion already. I did try to adjust the TPS but I haven't been able to get the bottom screw out despite 2 days of sitting in PBlaster and mild hammer taps. The metal on the screw head has already started to yield a bit, so I think I'm going to end up having to pull the UIM anyways to get it off.
You really are going to need a stock cat to pass. The Bonez cat is a nice part but it has nowhere near the density of material a stock cat does. It's typically borderline if it will pass.
Your air pump seems to be working just fine so you are good there.
Beg and borrow a stock main cat from someone and try that out. The pre-cat doesn't help with warm emissions testing, you should be able to pass with flying colors with a downpipe, stock main cat, and a healthy running car.
The FSM only has a spec for cutting air at 3250rpm (which it does) and a pressure check at the air pump outlet at idle (not sure exactly how much the SST plugs the elbow). I've sent some PMs and put up an ad for an OEM cat, but I'm interested in troubleshooting in the mean time. I'm still baffled as to why the split air made exactly 0 impact. Those two final output calculations could have been from back to back runs they're so close..
the CA test is way different, but in CA we don't get to the split air part, its all port air. and if the car doesn't want to go into port air, we make it go to port air. Port Air works so well you can almost make it pass without a cat at all, which is what the Bonez is
Without a wideband you don't know your AFR in the first place. Modern pump fuel, old fuel injectors that haven't been cleaned, aging vacuum lines, aging sensors, non-OEM O2 sensor, aging engine, and aging wiring harness have already imprecisely altered your car's AFR compared to how it would have run when brand new.
If the test operators are getting into boost during the test, the ECU will intentionally run the engine rich which is known to result in high HC and CO numbers. You can avoid that by loosening some of the clamps near the intercooler or y-pipe to create big boost leaks. That's not great for the turbochargers so avoid full throttle at high RPM with big boost leaks.
Or use E85 and install your old wideband if you want to keep an eye on it. The wideband sensor measures O2 content and doesn't know or care what fuel you're using; lambda 1.0 on e85 will still register lambda 1.0 just as if you were using gasoline, and then most wideband gauges convert from lambda to display AFR gasoline. So if you want to see 14.7 at part throttle on gasoline, you still want to the gauge to show 14.7 at part throttle on E85 (or some mix of 30% E85 and 70% pump gasoline). Because E85 has better octane than pump fuel, it's less likely to detonate even if you somehow manage lean the open-loop fuel mixture to numbers that would be dangerous for pump gasoline.
Without a wideband you don't know your AFR in the first place. Modern pump fuel, old fuel injectors that haven't been cleaned, aging vacuum lines, aging sensors, non-OEM O2 sensor, aging engine, and aging wiring harness have already imprecisely altered your car's AFR compared to how it would have run when brand new.
That's the thing, all of these ARE new on my build. It's new OEM stuff ordered from Ray/IRP/Atkins for everything in your list except the pump and O2.
The stock ECU will still run plenty rich at 7psi, but wiring the wastegate open would build boost less quickly on a sequential twins car. It might be easier to change the OEM blowoff valve's vacuum source to use atmosphere rather than manifold pressure. I haven't done that myself but I think that should make it act like a huge boost leak above 0 psi.
If you want no boost just loosen a few IC hose clamps. You don't have to go too crazy, just do that and you will have zero boost.
Actually worked on a friend's car once that was close to stock, forgot to tighten one hose clamp and the car literally had zero boost, no real weird noises, just drove like an NA car.
I finally got the bottom screw for the TPS loose, so I was able to replace both with some stainless hex bolts and get the TPS adjusted into the FSM range. I think the narrow range is sitting at about .8v closed, 4.99v open when the car is warm. This seems to have solved or at least greatly helped the stumbling after the AWS rev. The TPS adjustment also improved the hot idle exhaust smell, and I don't really get whiffs of raw fuel at idle anymore. I think I'm going to take it in as is on Monday just to have a graph to compare to the pre-TPS one.
I still don't have a line on a stock cat to either borrow or buy. Is there a published resource comparing the OEM cat's matrix composition to current manufacturers by chance? When I called the Colorado DMV about getting a repair waiver, the tech directed me to converters on carbcats.com which would qualify towards the cost cap in getting the repair waiver. I assumed cats that are CARB approved should have enough matrix material and rare metals to catalyze as well as the OEM if it's been through CARB testing/approval process versus high flow cats that aren't CARB approved. Not sure if that is actually the case though.
I still don't have a line on a stock cat to either borrow or buy. Is there a published resource comparing the OEM cat's matrix composition to current manufacturers by chance? When I called the Colorado DMV about getting a repair waiver, the tech directed me to converters on carbcats.com which would qualify towards the cost cap in getting the repair waiver. I assumed cats that are CARB approved should have enough matrix material and rare metals to catalyze as well as the OEM if it's been through CARB testing/approval process versus high flow cats that aren't CARB approved. Not sure if that is actually the case though.
CARB certification means that the cat went through the te$ting proce$$, and they paid the fee$
it doesn't mean much more than that
CARB certification means that the cat went through the te$ting proce$$, and they paid the fee$
it doesn't mean much more than that
Agreed, what we have found over the years is that very few aftermarket cats can hold up to Rotary exhaust temperatures and tend to fail fairly quickly. This is one reason why a quality cat for a rotary tends to be very expensive.
09-27-23, 05:52 PM
