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Just acquired an 89 CRX with a DOHC ZC and a Jackson Racing Supercharger. Took it for emissions inspection yesterday and failed due to high NOx levels (limit is about 1650 ppm and the car registered about 1800 ppm, so it's close).

My plan is to Seafoam the motor in order to clear whatever carbon deposits I can, then swap out the O2 sensor (just to be sure...especially after the Seafoam treatment), back off the ignition timing a little bit (to the low end of the specified range...about 16 BTDC).

Question - when feeding in the Seafoam through a vacuum line, should I only feed it in after the supercharger, or is it advisable/beneficial to feed it in pre-supercharger? I don't see any reason why it would hurt anything inside the unit, but I just want to verify that there aren't any sensors or seals I need to be worried about if I use a port pre-TB.

I think I may have just answered my own question...if I feed the Seafoam in pre-TB then I probably need to be worried about sensors, IACV and FITV...

I think I'm gonna find a port post-supercharger unless someone tells me it would be better to go the other way.

Anyway - if you have a strong feeling one way or the other, please let me know.
:cuddle:
 

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Post supercharger = boost, not vaccum.

That said, I'd be hesitant to go that way. If you really think that Seafoam is the answer, pop the intake off and scrub it down while you let seafoam sit on top of the pistons / in the intake ports for a few days.

I know that high cylinder pressures contribute to NOx, so it may just be a matter of the boost is making it jump.
 

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Discussion Starter #4
Post supercharger = boost, not vaccum....
Only with the throttle open - at idle (and part throttle) it's still vacuum (verified with the boostz gauge).

Pulling the intake/blower is a reasonable suggestion though...as always, thanks.
 

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Run it through the brake booster line on the manifold at idle then reconnect when you want to rev. Manifold sees vacuum until nearly WOT. Not really a point in going pre blower. How is the pcv system plumbed? Do you have a hose from the black box to the fitting on the s tube?
 

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Run it through the brake booster line on the manifold at idle then reconnect when you want to rev. Manifold sees vacuum until nearly WOT. Not really a point in going pre blower.
Awesome. Thanks.

How is the pcv system plumbed? Do you have a hose from the black box to the fitting on the s tube?
Yep, black box with hose running through a PCV valve to the s-tube.
 

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Seafoam isn't the answer. Making sure your timing is spot on and all other ignition related components are good/new is much more important than seafoaming the engine.

Understand what High NOx means, then work backwards from there.
 

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Discussion Starter #9
Seafoam isn't the answer. Making sure your timing is spot on and all other ignition related components are good/new is much more important than seafoaming the engine.

Understand what High NOx means, then work backwards from there.
I was under the impression (based on the research I have done) that high NOx was an indication of higher than expected cylinder temps and one of the contributing factors could be excessive carbon deposits, thus my plan to seafoam the engine and try to clean this out.

I also read that a bad 02 sensor can result in higher than normal NOx levels, thus the planned O2 sensor replacement.

I also read that retarding ignition timing can help lower NOx levels, thus the planned retarding of timing.

If my understanding is wrong on any of these points, please explain.
 

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Run it through the brake booster line on the manifold at idle then reconnect when you want to rev. Manifold sees vacuum until nearly WOT. Not really a point in going pre blower. How is the pcv system plumbed? Do you have a hose from the black box to the fitting on the s tube?
Note - this is how I hydrolocked that Z6 in my basement...
 

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I was under the impression (based on the research I have done) that high NOx was an indication of higher than expected cylinder temps and one of the contributing factors could be excessive carbon deposits, thus my plan to seafoam the engine and try to clean this out.

I also read that a bad 02 sensor can result in higher than normal NOx levels, thus the planned O2 sensor replacement.

I also read that retarding ignition timing can help lower NOx levels, thus the planned retarding of timing.

If my understanding is wrong on any of these points, please explain.
Your understanding is correct.

High cylinder temperatures can also raise NOx emissions, even if pressure isn't super high. This is typically caused by running lean. A really dirty or dead oxygen sensor might read artificially rich and trick the engine into running lean, so it doesn't hurt to replace it... except maybe for your wallet.

The first thing I'd check is your ignition timing. I'd probably run 14 deg BTDC for the emissions check. Depending on your vacuum at idle, even that might be too much.
 

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I prefer to seafoam by using a SMALL vacuum line and pouring SMALL ammounts of seafoam into a cup instead of using the whole bottle which is enough liquid to hydrolock most engines.

Triple D filled in what I was getting at.
 

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Discussion Starter #17
Used the vacuum line from the fuel pressure regulator with a cone shaped fitting from a mity-vac kit on the end of the hose and Seafoamed the motor yesterday (was careful not to introduce too much at once based on the hydrolock warning above) - another typical success story. Pushed the timing back as far as it could physically go (it was almost there already), swapped out the 02 sensor (so I have something to write down on the form I give to the testing station as my "parts replaced to remedy condition" on the back of the retest form), and - just to be completely anal - put zip ties on all the vacuum line connections on the intake manifold and throttle body to ensure there are no vacuum leaks. We'll see what the emissions testing station says later this week...
 

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While in theory, any carbon in the chamber will increase NOs, it would take a substantial amount of carbon build up to cause a noticeable increase in NOx.

The easiest cheapest way to remove carbon from the chamber is to introduce a squirt of water when the engine is under load. This is easily done with a windscreen washer bottle with a nozzle into the air duct before the supercharger. Operate the washer pump with a push button switch and only operate is during a good hard long pull.
 

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Discussion Starter #20
What engine management are you using?
The stage 1 kit for the DOHC ZC utilizes an auxiliary FPR and JR recommends using a higher flowing fuel pump (Walboro or whatever), but no reprogramming that I have seen. They offer ecu upgrades (to Hondata S300) as part of the "stage 2" kit (that includes the pulley upgrade), but at this point I am still just stage 1.

So at this point I don't have the ability to tweak the fuel maps or timing, but I was hoping I could get the car registered without having to go that far just yet. It is in the cards in the near future though.

I am even contemplating an E85 tune...
 
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