Why water jacket filled on EGR spacer?

[tim281]

I think the FRPP Cobra intake manifold is the only aftermarket manifold that eliminates the EGR spacer water jacket? Do all the other intakes just keep the EGR spacer and elimnate the water line connection? I would think there is no reason, except for cold start emissions, to have the water jacket heating up your intake charge.
Is there pretty easy to block off with some plugs at the intake manifold...any driveability issues?

I saw a pretty good deal on a performer intake, but then you have to pay additionally for the larger EGR spacer...so I guess the cobra intakes really are a lot cheaper when you keep that in mind.

 

[bubba-dough]

Do a search for egr and you will find all your answers. Also when you buy a larger throttle body, get the egr spacer at the same time as a package. Its a lot cheaper that way.

 

[95Vert383AOD]

Doesn't hurt not having it. I block them off or use a delete plate on my 302 and 383 motors. I don't see why you would need it.

 

[tim281]

Ok. I did a search and read a few posts to see what the just of the arguement is here. I think the EGR coolant is for cold start up issues and not to cool the spacer.
1.) On my old 87 Buick Grand National, it had the coolant lines going to the TB also and the EGR was located on the intake manifold...no where even close to the TB.
2.) From the Thermo standpoint, think of an open system mass flow anaylsis.Think about the volume of air going into your intake compared to the exhaust recirculation airflow volume. The intake air flow is probably 100X the amount of EGR gases...the bulk of the airflow is at atmosphere temperature and a tiny fraction is hot airflow from the EGR......the bulk airflow temperature will easly cool down any heat added by the EGR. I bet you could do a thermo model for this and show the air temp increase from the EGR is only about 2 degrees, where as the air temp increase from the coolant is definitely higher. Have you ever been working with metal and it gets really hot...then you grab your compressed air hose and shoot it for a second or two....presto it is cool. This is what is happening to your EGR input, think of your air intake as your compressed air cooling down the system.
3.) The cobra manifold doesn't even do it....why...because it is not needed and probably heats up airflow rather than cooling it.
4.) If you look up the thermal capacity of a fuild and then compare that to the termal capacity of air....again you will see that fuild dominate by an order of magnitude.....this means your TB will be heated up to the coolant temperature.

BTW...I am a mechanical engineer and this is my best gut feel without doing any research.