Introducing heat to the intake manifold

[siteunseen]

I have spoken with 3 mechanics whom I have complete faith in their knowledge of Imports. All of them told me that cutting the EGR valve mount off the rear of my N47 intake would be fine. Turning my N47 into something closer to the coveted N42 intake but still keeping the newer technology on the N47. I have a ceramic coated header from MSA for my '77 car with a N47 head that has no fitting for any kind of heat tube. Today I carried the intake to a Foreign car machine shop to have it vatted hopefully to de-carbon it. He said that my intake had to have a way of heat circulating or it would frost up and not run well. That's totally backwards from everything I've read on all the Z forums (this is my favorite and most helpfull, thanks to you all) I wasn't going to stand in his shop and argue with him the fact that people run the non EGR N42 on '77 & '78's and seem to be satisfied with their performance. So I left feeling like I had ruined my intake. I'm a Z diver (this is my 3rd Z & also had a '83 ZX) not a Z mechanic but I really enjoy working on this car, it scrathes my brain. I would love to someday help other people with their problems but that's about 10 years away! Does heat have to be circulated through my intake through the EGR passage like he says?

[Zed Head]

Sounds like your Foreign car machine shop guy knows too much about the wrong things.

[LeonV]

Does an engine need EGR? Did all engines before '74 "frost up" because EGR was not mandated? No, on both counts. Your mechanic doesn't know what he's talking about, which is typical...

Now, does the car run cleaner with EGR? Yes.

Does it hurt performance? No. There is no good reason to remove the system.

Edited September 22, 2011 by LeonV

[ZCurves]

No, you are absolutely fine. All the EGR does is allow small amounts of exhaust gas to be remixed and re-burned, thus improving the quality of the emissions. Just ask him to boil it out and weld it up - ignore the rest of his comments.

[LeonV]

EGR will also increase fuel efficiency.

[siteunseen]

Well now I can say I have complete faith. Thanks, I can relax now!

[siteunseen]

I see alot of benefit from the EGR but I've taken a sawz-all and now it's in the trash can. I have a $300 header with no EGR hole.

Edited September 22, 2011 by siteunseen

[FastWoman]

If the intake manifold were on an aircraft engine at 10,000 ft + on a cold winter day, then maybe. However, I think your carbs would ice up first. Your intake is sitting right above a hot exhaust manifold, stuffed into a barely-large-enough engine compartment. I've never heard anyone complain that their intake manifold is too cold. Quite the opposite!

[siteunseen]

If I have a frost problem I could always remove the heat shield. That guys so wrong. I will go elsewhere for my boil out vat bath. Thanks for all the replies they eased my mind up enough to remove the exhaust manifold. Baby steps before falling hard.

[ozconnection]

EGR will also increase fuel efficiency.

How can that be?

[LeonV]

How can that be?

There are three reasons, the first two of which are twice as important as the third. Firstly, holding load constant, pumping losses are reduced as EGR is introduced. Higher exhaust pressure increases intake pressure, therefore you achieve a better cylinder fill. Second, there is less heat transfer to engine walls (lower adiabatic flame temperature) which reduces heat losses. The third has to do with the chemical reaction during combustion being more efficient (decreasing degree of dissociation).

Referenced from Heywood's Internal Combustion Engine Fundamentals.