Will the FD generation pass smog by substituting a straight downpipe in lieu of stock upper catalytic converter? It has been mentioned that excessive heat is generated because of the 2 catalytic converter system.

 

https://www.rx7club.com/showthread.p...ight=emissions

 

The first cat is for cold start clean air test . Most places do not test for that .Go to the after market pipe and you will be good to go .

 

As the last 2 posters said, you should be OK with emissions. And taking off the precat does reduce underhood heat quite a bit.

 

In general, it fails visual inspection if they know what they are looking for... It will pass the sniffer tests. I haven't really heard of too many people in CA getting flagged visually for one, but it can fail your visual inspection.

 

If that is the case, then the HKS DP is less obvious, since it is not shiny stainless steel.

Dave

 

My car passed California smog with a downpipe installed. The car has never failed smog in the past, so it's not required to take it to a Test Only station. As mentioned by others, the tech could have failed me for visual inspection, but I'm not sure he noticed or cared.

-s-

 

i have a random technology high-flow pre-cat downpipe for sale...PM me for info

 

You'll be fine as far as passing goes. I passed Ca emissions with FLYING colors (yeah, even I couldn't believe it) with a downpipe. If you're really scared about visual, you could try spraying your downpipe with some black hi-temp paint, it should help it "stick-out" less.

 

if you end up switching your pre-cat for a downpipe, i would get a shop to do it. ask them wat they charge for a downpipe install, that way they have to stick to the price. its very frustrating and time consuming in my opinion.

 

I've got a straight downpipe and a stock cat and just failed emissions here in toronto, canada.

Any thoughts? I don't think our test would be any more strict than in California.

 

There have been a lot of threads on passing emissions if you search. The usual problems, though relate to:

1. non-functional air pump or ACV
2. dead cat
3. ignition problems

How close were you? What other modifications do you have?

 

Here is a list of mods:

Apexi Power FC ECU with Commander
Intake Hard Pipes w/K&Ns
Megan Racing Downpipe
Petitt Racing Aluminum AST
Megan Racing Midpipe
Racing Beat dual-tip catback
GReddy Elbow
GReddy Intercooler Piping
GReddy Profec-b Spec 2 boost controller
Supra TT Fuel Pump

The results with this set up were

Curb Idle
HC ppm: Limit 200, Reading 332 FAIL
CO%: Limit 1.00, Reading 1.92 FAIL

ASM 2525
HC ppm: Limit 64, Reading 402 FAIL
CO %: Limit 0.35, Reading 2.94 FAIL
NO ppm: Limit 485, Reading 301 PASS

Then, I installed a stock cat and these were the results

Curb Idle
HC ppm: Limit 200, Reading 179 PASS
CO%: Limit 1.00, Reading 0.26 PASS

ASM 2525
HC ppm: Limit 64, Reading 309 FAIL
CO %: Limit 0.35, Reading 2.43 FAIL
NO ppm: Limit 485, Reading 112 PASS

I was thinking I would try to get a precat installed, but from reading other posts here, it sounds like that might not be the right approach.

Dave

 

You're very lucky then. My FD has never failed a smog test but I have to go to a test only station each time. Same thing with all my previous RX-7s as well as my friend's. My FD passes the emissions test with flying colors with an HKS downpipe as well.

 

I'm guessing (and that's all it is, is a guess) that since your idle readings looked good with the cat, but the with-cat 2525 readings didn't improve much from the no-cat ones, that
a) the air pump and ACV are working (air pump air is more necessary at idle)
b) the cat may be at least partially defunct and unable to handle the higher flow requirements of the 2525 test
c) your partial-throttle mixture is pretty rich.

And, I agree that a precat should not be necessary if everything else is mostly working as intended.

Dave

 

Thanks very much, Dave

If the cat is no good, I know what to do about that, but how would I alter the partial-throttle mixture?

Thanks,

Dave

 

Now you're getting beyond my knowledge base, but remapping the Apexi Power FC ECU would be my 1st thought.

Dave

 

JDM cars came without a precat

 

RTRYRCKT I had almost the identical setup. I drove to the test place and swapped out my computer in the parking lot, passed with flying colours. Put back the pfc computer and drove home! I did have a new high flow cat and o2 sensor. Just to mention I failed 2 times previously. Once that day.

 

Well folks, I had my car tested again - this time with the stock ECU.

PASSED ("like a football")!!!

Thanks Northern7 for the tip! We Canadians need to stick together! :-)