Want an intake manifold but need EGR for CA smog

Sand

Sand

Greenie N00B Member
Greenie Member
I live in the wonderful golden state of California, where I can't legally pass smog with a single emissions readiness monitor that doesn't pass. But I also have a speed 3 that I am stocking up on parts for a "big" turbo swap on (cst4). I would like to keep all the emissions equipment so that I only have bribe my smog guy to pass me visually.

I really want to do an aftermarket (Corksport or ST) manifold after hearing how poorly balanced the stock manifold flows, but that requires me to remove the EGR, failing the EGR readiness check. Has anyone found a way to trick the ecu into thinking the EGR is working while it's actually removed?

Could we simply block off the metal hose that goes from the EGR by the exhaust to the Intake?

I found this awesome thread (not being sarcastic this time) https://mazdaspeeds.org/index.php?threads/drive-cycles-for-emissions.6026/ in which someone outlined a method of fooling the ecu with a length of vacuum line but people argued the realism of this method.

Any experience, theories, and discussions welcome. Thanks!

Another idea... Has anyone tried plumbing the Egr into their intercooler piping?

I know everyone's first thought is to remove Egr (for good reason)...
 
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Ideally you want the EGR to always be in a full vacuum environment. That's why the EGR tube is always behind the throttle plate.

You could try and make your own port on one of those manifolds. Basically make a custom EGR to manifold pipe and then a fitting on the manifold to adapt it.

Another option is to port a stock intake and fully remove the divide between the runners in the manifold itself. On the head ports you'd knife edge the divider between the ports to help smooth the transition into the cylinder head.

You keep the stock look, it's still CARB "legal" though I use that term loosely.
 
Lol yeah thats what I am going for... Carb """legal"""

Lots of good ideas. How would you go about making a port on a plastic ST manifold? That point about vacuum makes sense, so does Egr just stay shut if you're making some boost?

And I have heard a little about porting the stock manifold and the concept makes sense, but this post https://mazdaspeeds.org/index.php?threads/your-intake-manifold-and-you.1271/ seems to indicate there was an even greater flow imbalance after porting the manifold.

I just don't want one cylinder running leaner than the rest and causing issues, especially if I end up going 6th Port...
 
The EGR is shut when the solenoid is off. You want it in a full time vacuum so it pulls the exhaust gasses into the engine. If it was before the throttle plate then extremely hot air would be stagnant and not move as quickly. This would cause excessive heat soaking of the intake system.

Carbon build up from the EGR is mostly due to unburnt fuel, oil droplets, and the fact nothing is wetting the valves/port to keep the carbon from sticking to it.

@Raider is right about going fully stock for smog testing. That's the easiest way to ensure you pass.
 
I know that Cobb has said that they will no longer support bypassing emissions or something to that effect. I do not fully know what that means. People can still use old versions of their software yes? In any case, I have no EGR and no VCTS and no CEL codes with a Cobb AccessPort tune.
 
They never actually hid the cel what they did was switch it so the code was always in a not ready state similar to if you had just replaced the battery and the sensors haven't had enough miles to recalibrate. Now they do not put them in it ready so you get the cel. I believe that the change is in new versions of atr so don't update though it may somehow be forced. If you are self tuning with an older version of atr you should still be able to turn them off otherwise you are stuck.

Not having a visible cel didn't mean that you could pass emissions in states that use obd2 scanners as there is a limit on the number of not ready you can have. Maryland is one California is zero I don't know about other states
 
Thanks for the information. I googled for Texas. Vehicles prior to 2001 can have 2. After 2001 can only have 1
 
Yeah stocking out would be one way to ensure passing but that means I'd have to change my turbo, downpipe, intercooler, and if I get a new intercooler that too.

Working on cars is fun but redoing work sucks.

Does anyone know what the ecu does to pass the readiness monitor on the Egr?
 
Sand said:
Yeah stocking out would be one way to ensure passing but that means I'd have to change my turbo, downpipe, intercooler, and if I get a new intercooler that too.

Working on cars is fun but redoing work sucks.

Does anyone know what the ecu does to pass the readiness monitor on the Egr?
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When the engine gets up to operating temperature and PCM commands the EGR valve to open, exhaust will start to flow into the intake manifold. When this happens the PCM uses the MAP sensor to see if they're is now a pressure dIfferential in the manifold from the EGR valve opening. This tells the PCM that exhaust is flowing. So there's two checks, check one that valve circuit is working, and check two MAP sensor pressure data. You can obviously pass check one by just plugging in the EGR, but fooling the MAP sensor is damn near impossible since you need accurate MAP data for proper tuning performance.
 
Great explanation. Also explains why two check engine light codes come up when disabling the EGR system.

I wonder if there is a way to filter the EGR or something, like how we add catch cans to our PCV lines to catch the garbage before it makes it to the intake system.
 
Sand said:
Great explanation. Also explains why two check engine light codes come up when disabling the EGR system.

I wonder if there is a way to filter the EGR or something, like how we add catch cans to our PCV lines to catch the garbage before it makes it to the intake system.
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Are you still trying to figure out a way plumb an EGR with a ST manifold?

I've talked to my tuner about this and seen other information on just splicing into the PCV port on the Manifold. Obviously you'll need to build a custom EGR tube for this and use something like a brass T fitting.
 
The way manufacturers eliminated the EGR system is with VVT on both camshafts. By controlling overlap they can control exhaust gas temperature.

If you add EGR into a plastic manifold you risk melting it. If the ST manifold doesn't have a provision for it then it is either done through a port within the head or controlled by valve overlap.
 
337, this was one of the reasons I decided to go with an aluminum intake manifold. I considered the ST but as you mentioned the temps from the EGR gasses would be a problem.

I considered something that would drop the EGR gas temps enough to make them tolerable for the ST manifold but decided it was too complex and too much work. That and other reasons just make that manifold too much of a headache to try and use in my situation
 
I still haven't run into anyone who has tried it on this platform, but I plan to try and pipe the EGR into my catch can pathway between PCV and CS intake manifold (hose selection will be important if leaving EGR active long term) MAP should still see the pressure differential and I would hopefully get some carbon catching. TBH hose melting at the T isn't even much worry to me because the EGR will be left unplugged and inactive unless I'm going through smog, so the hose only needs to survive that day and I can throw a new one on next time I smog it.

So plan would be to leave most of the metal pipe intact but cut off the end and pipe to catch can loop
 
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