626 Manifold Install Questions

[KrayzieFox]

But the EGR doesn't vent, it pulls air in. So I guess I don't see the difference between the EGR pulling in air from the exhaust manifold vs atmosphere.. neither gets registered by the MAF. Plus, the exhaust isn't a closed system like the intake, so that kind of makes the EGR system a temporary vacuum leak by definition.

Anyway, there are just semantics at this point.. what matters is that I can from personal experience guarantee you that you won't get a CEL from hooking up your EGR to pull from atmosphere while capping the exhaust port.

Good luck to you, and if you need pictures of this install let me know and I can snap some of my bay when I get home.

 

[hornsfan10609]

All air that runs through the engine is metered by the MAF, it becomes exhaust after it enters the combustion chamber. The EGR does not pull fresh air from the outside it simply recirculates exhaust from the manifold, exhaust that was air that was measured by the MAF.

 

[KrayzieFox]

All air that runs through the engine is metered by the MAF, it becomes exhaust after it enters the combustion chamber. The EGR does not pull fresh air from the outside it simply recirculates exhaust from the manifold, exhaust that was air that was measured by the MAF.

Ok I see what you're saying, but I don't think that it matters for the air that comes back in to have been metered by the MAF at some point. I say this because the total amount of air reintroduced back into the intake manifold is the same regardless of source, and that's the value that actually matters here. The net gain in air through the EGR. Whether it comes from the exhaust or the atmosphere won't affect how much is reintroduced, hence why you don't get a drop in vacuum or a CEL with this setup.

I guess the real difference between the two is overall O2 content, as fresh from the atmosphere will have higher O2 content than exhaust. So in theory pulling in fresh air would cause you to run a bit lean since the ECU is expecting "dirtier" air from the exhaust that doesn't require as much fuel to combust, but in practice I think this amount is so negligible that it doesn't make a bit of difference :/