Honda / Acura K20a K24a Engine Forum banner
1 - 20 of 43 Posts

·
Registered
Joined
·
19 Posts
Discussion Starter · #1 ·
Need to smog my RSX Frank motor k20 head/ k24 block in Cali. I have an ECU that i normally run with KPRO, but apparently they are flagging if its not your stock ecu. Can i safely put my stock ecu back in and drive it until all of the monitors reset, and get it smogged, or am i gonna torch my engine?

thanks and sorry if its a repost.
 

·
Registered
96 civic HX K24a
Joined
·
2,569 Posts
Need to smog my RSX Frank motor k20 head/ k24 block in Cali. I have an ECU that i normally run with KPRO, but apparently they are flagging if its not your stock ecu. Can i safely put my stock ecu back in and drive it until all of the monitors reset, and get it smogged, or am i gonna torch my engine?

thanks and sorry if its a repost.
You will have cel for anything not hooked up that the oem ecu will call for but you can putt around on the stock computer I wouldn’t go doing any pulls /no vtec your engine needs quite a bit more fuel than the k20 map gives.
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #3 ·
You will have cel for anything not hooked up that the oem ecu will call for but you can putt around on the stock computer I wouldn’t go doing any pulls /no vtec your engine needs quite a bit more fuel than the k20 map gives.
Thanks. Everything is hooked up. Oddly enough I went Frank, but everything is pretty stock except for a cai. I did move the wire on the harness to give me the reverse lockout as it's a base ecu. But otherwise pretty stock. Guess I'll poke around town and get the monitors into a good state and have em smog it.. thanks for the help.
 

·
Arouse the DAMPFHAMMER!
Joined
·
9,465 Posts
...my stock ecu back in and drive it until all of the monitors reset, and get it smogged, or am i gonna torch my engine?
What phrase @Brotatochip used recently? Ah yeah, I second that what @KBuilt said. If you plug the stock ECU without any modification you definitely will run your engine lean, pretty lean, such lean that the smog test may smog your engine if ECU is in open loop. Just do the calculation, assuming same VE, the 2354 ccm block will like to suck around 18 % more fuel to run the same lambda. Normally ECU is in closed loop, that means the lambda controller has to send a plus 18 % more fuel add signal to the ECU. Normally at +-10 % the ECU has to send a signal to the OBD output about this. Maybe not a MIL, but the smog tester will see that the correction (STFT value, see below) is very high.
  1. You won't pass the test, especially if the smog guy does a tip in test. The lambda controller will need more then a half wave to find back to setpoint.
  2. You have to tune it with an Technology which does not bother the OBD output (like Doctronic)
  3. You will likely get MIL codes as STFT (short time fuel trim) will likely exceed it's limit or at least exceed the limit to through a code on the MIL lane.
You need to inform yourself about smog test requirements and what you need for it to be done before. Here some hints: BAR'd K20A | Honda / Acura K20a K24a Engine Forum.
 

·
Registered
Lotus Elise K20A2
Joined
·
1,407 Posts
the trims won’t matter as long as they do not exceed the limits to activate MIL. +-30% are not uncommon as tolerance band. Something as simple as a clogged paper air filter is sufficient to warrant such as trim.
If you pass emissions with the stock ECU and no MIL/DTC codes are flagged, you’re fine.
At worst, install bigger injectors or up the fuel pressure a tad.
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #7 ·
the trims won’t matter as long as they do not exceed the limits to activate MIL. +-30% are not uncommon as tolerance band. Something as simple as a clogged paper air filter is sufficient to warrant such as trim.
If you pass emissions with the stock ECU and no MIL/DTC codes are flagged, you’re fine.
At worst, install bigger injectors or up the fuel pressure a tad.
Good info. Cali doesnt use a sniffer anymore as far as i know. They hook up to the obd port and run the car for like 5 minutes. I am assuming to ensure it doesnt trip a cel. I am assuming that they are of the belief now that if all of the computers are working and all the emissions equipment is on the car it should be within limits smogwise. I installed the stock ECU earlier, and drove it around the block. Has a terrible idle, but otherwise seems to run fine. I'm planning to drive to/from work tommorow 35 miles each way and hopefully it will reset all the monitors. If i pass smog then i'll pop the kpro ecu back in for 2 years.

Thanks.
 

·
Registered
Lotus Elise K20A2
Joined
·
1,407 Posts
in Germany they reintroduced the sniffer tests even for the most modern vehicles. That can lead to funny situations with some plug-in hybrids and hybrids. The outlander for example cannot run its engine while stationary unless the battery level is below 80%. My Prius needs to be switched into a service mode though a complex sequence of pressing buttons, lights on and off, brake switch etc.
Why all of this? They found that some drive with non-function cats and have installed MIL eliminators or modified software.
But I believe the main trigger was the VW Diesel scandal with VW suffering the least in Germany and the can owners the most.
 

·
Arouse the DAMPFHAMMER!
Joined
·
9,465 Posts
I assume you're talking about this quote when someone asked what ECU to use on a K24a2? :LOL:
Oh, sorry, it was @Bjorn who seconded what you've posted. I just remembered your conversation, mixed up and the phrase "I second that...".

Cali doesnt use a sniffer anymore as far as i know. They hook up to the obd port and run the car for like 5 minutes.
Good luck for it. I am looking forward to your report about it, which may help others to pass this test.
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #10 ·
Well sofar no good. My catalyst monitor is till inc. every so often I get a cel with p420. I'm thinking I will have to find a guy to hook up my smog, as it seems this lean condition isn't allowing my cars cat monitor to go complete.
 

·
Arouse the DAMPFHAMMER!
Joined
·
9,465 Posts
as it seems this lean condition isn't allowing my cars cat monitor to go complete.
As I said it before, without tuning the engine lambda you won't challenge it easily. Do you have any to organize someone with techniques of doing it?
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #12 ·
As I said it before, without tuning the engine lambda you won't challenge it easily. Do you have any to organize someone with techniques of doing it?
I have a tuner, who i will have to talk to. Unfortunately, I dont believe there is a way to make a KPRO imitate the stock ecu hash. I suspect there are alternate way's to make my car pass. I will have to talk to some people. Only thing is, that usually this kind of pass is 3x the price of a normal smog.
 

·
Arouse the DAMPFHAMMER!
Joined
·
9,465 Posts
I have a tuner, who i will have to talk to. Unfortunately, I dont believe there is a way to make a KPRO imitate the stock ecu hash. I suspect there are alternate way's to make my car pass. I will have to talk to some people. Only thing is, that usually this kind of pass is 3x the price of a normal smog.
I've tuned many builds for TÜV compliance which worked out well. There are no MIL's poping up. Alsi sniffer test get passed as well, which is much more challenging as just passing the OBD reading. So don't worry, speak with your tuner if he has experience on that...and if he is confident about the test requirements.
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #14 ·
I've tuned many builds for TÜV compliance which worked out well. There are no MIL's poping up. Alsi sniffer test get passed as well, which is much more challenging as just passing the OBD reading. So don't worry, speak with your tuner if he has experience on that...and if he is confident about the test requirements.
I dont think you understand exactly. The problem in California is, that KPRO is illegal. Before 2022, they did not try to detect it. So all previous years, my car passed smog on a tune. This year. The smog equipment is detecting KPRO installed by using a known Hash of the factory ECU and comparing it. So, i was attempting to put my factory ECU into the car, just to pass the smog. Once i passed the smog i would put the Kpro ECU back in. Since that is not working, I am going to have to find a person who will find alternate means of getting this smog done. I might even end up rebuilding my k20 block and putting it back in to avoid this hassle anymore.
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #15 ·
the trims won’t matter as long as they do not exceed the limits to activate MIL. +-30% are not uncommon as tolerance band. Something as simple as a clogged paper air filter is sufficient to warrant such as trim.
If you pass emissions with the stock ECU and no MIL/DTC codes are flagged, you’re fine.
At worst, install bigger injectors or up the fuel pressure a tad.
Do you think bigger injectors on my stock prb ecu will fill the p420 CEL i am getting?
 

·
Arouse the DAMPFHAMMER!
Joined
·
9,465 Posts
...problem in California is, that KPRO is illegal. Before 2022, they did not try to detect it. So all previous years, my car passed smog on a tune. This year. The smog equipment is detecting KPRO installed by using a known Hash of the factory ECU and comparing it.
Ok, that is new to me. Here the Doctronic would might help as the guys at Doctronic change only the setup of the one of the chip on the Honda ECU. They don't add any additional mother board like KTuner or Hondata does it. You might speak with them, they have also customers in oversea and speak English too.

Bigger injectors, like @Lotus recommended, or a higher fuel pressure would also solve your issue partely. You need roughly 18 % more fuel, the calculation of the injector size or increased fuel pressure is easy. It can't solve all imperfections, as the VE map of the 2-Liter compared to the 2.4-Liter engine is quite different over load and engine speed, but it would be a much better match. I would check up the Doctronic route for the long term and for the short term solution I would install an adjustable fuel pressure regulator and hide it, clean up the stock as for dummy use, as some smog test guys are not bad at their job ;).
 

·
Registered
Lotus Elise K20A2
Joined
·
1,407 Posts
you could pop back your KPro back in and load a stock k20a2 map in there. Or just open it in the software. Check for the injector map value in the idle area, check for the injector size in the map. Next do the same for a k24 map. This gives you an idea on injector sizes and the amount of fuel required.
If you run it on the k20a2 stock map on the KPro, you should even actually see how much leaner or richer it runs. The short term fuel trim will tell.

I think you might get close with a plain injector swap to a larger or smaller size depending on too rich or too lean.
Thing is that at idle and fast idle, a k20 or a k24 will need about the same amount of fuel per revolution as both loads and rpm are very similar. As the K24 runs bigger injectors, a k24 map will likely use a shorter injection duration compared to a k20 map. If you run a k24 with k24 sized injectors on a k20 map, it will likely run way too rich.

What injectors are you running? Stock RSX-X or bigger injectors, e.g. K24?

I just had a look in the Hondata software. The RSX-S stock map, the K24 Accord stock map and the k24 TSX stock map use about the same fuel values at idle, ok within a few %. The RSX-S and the TSX maps are set up with 310cc injectors while the k24 Accord stock map is set up with 270cc injectors.

At say 600mbar and 1000-1250 rpm the RSX-S map and the TSX map are near identical, but the Accord map lists a value 17% higher. This corresponds to about the difference in injector size.
As long as these engines are heavily throttled at part loads, especially lower part loads, they seem to use about the same amount of fuel at the same MAP and rpm.
I am guessing you are using the wrong sized injectors. You best bet will be using the injectors that are matched/belong to the stock ECU.
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #18 ·
you could pop back your KPro back in and load a stock k20a2 map in there. Or just open it in the software. Check for the injector map value in the idle area, check for the injector size in the map. Next do the same for a k24 map. This gives you an idea on injector sizes and the amount of fuel required.
If you run it on the k20a2 stock map on the KPro, you should even actually see how much leaner or richer it runs. The short term fuel trim will tell.

I think you might get close with a plain injector swap to a larger or smaller size depending on too rich or too lean.
Thing is that at idle and fast idle, a k20 or a k24 will need about the same amount of fuel per revolution as both loads and rpm are very similar. As the K24 runs bigger injectors, a k24 map will likely use a shorter injection duration compared to a k20 map. If you run a k24 with k24 sized injectors on a k20 map, it will likely run way too rich.

What injectors are you running? Stock RSX-X or bigger injectors, e.g. K24?

I just had a look in the Hondata software. The RSX-S stock map, the K24 Accord stock map and the k24 TSX stock map use about the same fuel values at idle, ok within a few %. The RSX-S and the TSX maps are set up with 310cc injectors while the k24 Accord stock map is set up with 270cc injectors.

At say 600mbar and 1000-1250 rpm the RSX-S map and the TSX map are near identical, but the Accord map lists a value 17% higher. This corresponds to about the difference in injector size.
As long as these engines are heavily throttled at part loads, especially lower part loads, they seem to use about the same amount of fuel at the same MAP and rpm.
I am guessing you are using the wrong sized injectors. You best bet will be using the injectors that are matched/belong to the stock ECU.
This is all great info. I am actually using the stock rsx injectors. When i did my swap i took all parts from my old engine, except for the head gasket.
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #19 ·
Ok, that is new to me. Here the Doctronic would might help as the guys at Doctronic change only the setup of the one of the chip on the Honda ECU. They don't add any additional mother board like KTuner or Hondata does it. You might speak with them, they have also customers in oversea and speak English too.

Bigger injectors, like @Lotus recommended, or a higher fuel pressure would also solve your issue partely. You need roughly 18 % more fuel, the calculation of the injector size or increased fuel pressure is easy. It can't solve all imperfections, as the VE map of the 2-Liter compared to the 2.4-Liter engine is quite different over load and engine speed, but it would be a much better match. I would check up the Doctronic route for the long term and for the short term solution I would install an adjustable fuel pressure regulator and hide it, clean up the stock as for dummy use, as some smog test guys are not bad at their job ;).
How does a fuel pressure regulator work? does it require a bigger fuel pump?
 

·
Registered
Lotus Elise K20A2
Joined
·
1,407 Posts
Same as on a propane tank for the BBQ.
Fuel enters one side and exits on an other side.
There is a spring loaded membrane inside holding a needle over an orfice that adjusts the flow rate in such a way the input pressure stays the same.
AFAIK the FPR on a civic is commonly integrated into the fuel pump assembly.
In most Honda cars, you won't require a bigger pump for modest pressure increases.
Mind you that at higher pressures, the pump flow might be reduced.
I'd only increase fuel pressure for your emissions purposes and turn it back to stock ASAP.



Arm Tool Font Machine Fictional character


Product Rectangle Font Gas Cylinder



some cars like the RSX-S use a dead end system. The fuel rail can either be connected to an extra outlet of the FPR or just tee'd of the supply line.
Most higher power or tuned cars change to a return system as it provides fuel more evenly over the injectors at high flow rates and tend less to require pulse dampers.
Rectangle Line Font Parallel Slope
 

Attachments

1 - 20 of 43 Posts
Top