what's the difference???n42/n47 intake.

[Megatherion]

I've been searching, but I didn't find an answer, I bought my '78 280z with the stock n42 block and n47 head, but the intake manifold is a n42, now my question is, is that ok? or do I need to change the n42 for a n47 intake manifold?

 

thanks!

[Lukaniuk]

Yup you need a different manifold. So you might as well take that n42 off and give it to me.

 

jk

 

I'm not sure on exactly what the difference is, but you're ok with the n42 manifold.

[Daeron]

the manifolds have many subtle differences, but they are all largely interchangeable. The most significant difference in any of them is whether or not the manifold was designed with an EGR system; being in california (and as late a model as you have) I highly suspect yours is an EGR style intake.. but judging from your sig, that makes about as much difference to you (for the time being at least) as having the right cigarette lighter for the car...

[Challenger]

Well both the n42 and n47 didnt have webbing. Some n42s didnt have egr some did. But I think the n47 was only egr'd. Not sure which years the n42 was egr and not egr. I know that some 75's had it if not all...

[Megatherion]

thanks for the quick answer guys, also the guy who sold me the car gave me the n47 manifold, I really don't know why he changed the manifolds, and yes both manifolds have the EGR valve.

[BRAAP]

Well both the n42 and n47 didnt have webbing. Some n42s didnt have egr some did. But I think the n47 was only egr'd. Not sure which years the n42 was egr and not egr. I know that some 75's had it if not all...

 

This should help clarify which Z's did and did not have EGR.

ALL '75-'78 280-Z's destined for CA had EGR.

ALL '77-'78 280-Z's destined for all states in the US had EGR.

Only '75-'76 Federal cars, (non CA), were the NON EGR N-42 intakes.

 

The only difference functionally, one would be concerned with regarding swapping intakes, is if they need EGR for emission reasons. Out side of that, functionally ALL the OE EFI intakes, '75-'83 are interchangeable.

[Zmanco]

I'll ask this question here as I think it adds to the thread (if not, sorry for the thread jack): it seems like most people find the non-webbed manifolds more desirable than the webbed. But it's my understanding that Nissan added the webbing in later years to help reduce the heat rising from the exhaust manifold and heating the fuel rail. If that's true, then wouldn't the webbed be more desirable?

 

Or is it just that the non-webbed looks better?

[BRAAP]

This debate still drones on, and has not been definitively tested and measured as to which style, (webbed vs non webbed), offers what benefits over the other under what conditions and for what applications.

I am pretty sure the webbing was not intended to protect the fuel rail from heat so much as to help contain/manage exhaust heat in general and may have been done in an effort to help in the manufacturing/casting of the manifold itself, or the webbing was an effort to reduce the likelihood of engine fire from leaking fuel injectors, i.e. wont dribble directly down onto the hot exhaust manifold, instead puddle up on top of the intake? (The last one may be a bit of a stretch… )

 

The webbing does help keep exhaust heat from radiating up above the intake, but the aluminum is also a heat sink, and that webbing will absorb that exhaust heat that now corralled under the intake, i.e. hotter intake manifold overall.

 

Personally I prefer the non webbed for aesthetic reasons and that it wont trap as much heat under itself, therefore absorbing that heat into the manifold, and ultimately raising IAT. Others will say other wise for their reasons and that is fine.

 

Until we see some hard data from back to back testing with temp sensors around the engine bay recording temps of the intake manifold, fuel, IAT's etc, under varying conditions, environments, engine loads, road speeds etc, we are mostly theorizing. Some have some IAT data, but nothing that is a direct back to back comparison.

[FlatBlack]

Im using the non webbed only because I think it looks better. And it already had the EGR off

 

[woldson]

This debate still drones on, and has not been definitively tested and measured as to which style, (webbed vs non webbed), offers what benefits over the other under what conditions and for what applications.

I am pretty sure the webbing was not intended to protect the fuel rail from heat so much as to help contain/manage exhaust heat in general and may have been done in an effort to help in the manufacturing/casting of the manifold itself, or the webbing was an effort to reduce the likelihood of engine fire from leaking fuel injectors, i.e. wont dribble directly down onto the hot exhaust manifold, instead puddle up on top of the intake? (The last one may be a bit of a stretch… )

 

The webbing does help keep exhaust heat from radiating up above the intake, but the aluminum is also a heat sink, and that webbing will absorb that exhaust heat that now corralled under the intake, i.e. hotter intake manifold overall.

 

Personally I prefer the non webbed for aesthetic reasons and that it wont trap as much heat under itself, therefore absorbing that heat into the manifold, and ultimately raising IAT. Others will say other wise for their reasons and that is fine.

 

Until we see some hard data from back to back testing with temp sensors around the engine bay recording temps of the intake manifold, fuel, IAT's etc, under varying conditions, environments, engine loads, road speeds etc, we are mostly theorizing. Some have some IAT data, but nothing that is a direct back to back comparison.

 

Just out of curiosity, did the the heat shield and injection fan show up at the same time as the webbing?

In my deep discussions of heat sinks for CPUs, my understanding concluded with the idea that aluminum can absorb heat OK, but sheds heat like a mother.

Hence the copper bottom heat sinks. Also you remove something from baking that is covered in aluminum foil that is at 350deg, the foil will cool in literally 1 to 2 seconds.

Yet you can cover something hot with aluminum foil and it will keep it hot for a much longer time.

[BRAAP]

Just out of curiosity, did the the heat shield and injection fan show up at the same time as the webbing?

In my deep discussions of heat sinks for CPUs, my understanding concluded with the idea that aluminum can absorb heat OK, but sheds heat like a mother.

Hence the copper bottom heat sinks. Also you remove something from baking that is covered in aluminum foil that is at 350deg, the foil will cool in literally 1 to 2 seconds.

Yet you can cover something hot with aluminum foil and it will keep it hot for a much longer time.

 

The steel heat shield was used since day one.

Injector fan introduced on the ZX in '79.

 

Yes, your assessment of heat transfer in aluminum is accurate, but the foil is not really a fair comparison regarding our intake manifolds.

 

I’ll keep try and keep this simple.

Thickness of the aluminum AND its surface area are the factors we are interested in, (Delta T, or temp differential, is also part of this but for our examples, it is constant). The Quantity of aluminum determines how "much" heat it can hold. Its surface area tells us how "fast" it can absorb and release that heat at a given temp differential, (Delta T). How much and how fast. The more aluminum you have, the more heat it can absorb and hold. The more surface area that volume of aluminum has, the “faster” it can absorb and release that heat. Foil is at one end of this spectrum being very little in quantity, but with a lot of surface area. It gets hot and cold FAST! Now picture a solid block of aluminum, same volume of material but block form, not a sheet. A lot of quantity with not as much surface area as the foil, (surface area to volume ratio). This block will take much longer to fully absorb that heat and much longer to release that same heat, in the same environments. Our intake manifolds have a much greater volume to surface area ratio compared to foil.

 

The area under our intakes is quite hot on a running engine. Hotter than we want our intake manifolds to be. The non webbed manifolds will absorb so much heat, the rest passes through, between the runners. Webbed manifolds absorb approx as much heat into/though the runners as the non webbed, but the webs are not allowing the heat to just pass through without absorbing it first, then the webbing rejects some of that heat off the top, (Delta T, or difference in temperature between the two surfaces), the rest of that web absorbed heat goes into the runners and plenum with the cooler air inside. Add to this, the manifold cannot “transfer” this quantity of heat "through” the webbing as fast as that heat could just rise up through the between the open runners of the non webbed, we are now trapping some of that heat under the manifold, allowing the manifold more time to absorb that heat trapped under it, and is probably hotter.

 

This is where it gets sticky. The air our engines ingest passes "through" this now hot intake manifold. This air that is feeding the engine we have gone to great lengths to make sure is cold and dense with our super-whiz-bang cold air intakes, now is absorbing the heat out of the manifold that it absorbed from the exhaust! The air that actually enters the cylinder is not as cold as we prefer or thought it was... Think drag racers icing their intake manifolds!

 

This is the only real disadvantage to non cross flow head designs having the intake and exhaust entry/exit on the same side of the head. The intake is generally over/above the hot exhaust.

 

Now if we can keep the heat for getting into the manifold all together, … That is whole other topic, ceramic coatings, heat barrier manifold gasket, heat shields wrapped with header wrap and those shields totally separating the engine bay into upper lower/cold and hot decks, with ducting, fans, etc… Again, a topic for another discussion, not this thread.

[woldson]

Good stuff, thanks as always:)!