Custom making exhaust manifold and pipes

[NZAE92]

OK
so next year in technology we are allowed to make anything we want has anyone made custom exhaust manifolds for the 4AF if anyone has could they post picks of them so i have a vague idea of what fits and what looks good??
cheers

[jmaz87]

have u looked on ebay? fyi 4afe manifold would fit and prb easier

[SCT]

I guess it naturally custom, thanks to rust, I removed the resonator and the mufflers' gone. So, all there is on my car is possibly a cracked header, flex pipe, cat, more pipe, ends right after the rear wheel, not under the bumper.

Sounds very nice.

When I get my SV, I may keep the stock headers or get the ones off ebay, unless I actually go turbo which is likely. For the rest, no resonator, no muffler, 2.5" all the way, heat coated sterling silver.

[NZAE92]

i need it to be hard. if i can get all the stuff for free then i may aswell goo the hole 9 yards and get everything custom made which i can do at school which would be great

[freakinbox]

look at some of the 4age headers. The 4af/4afe headers are really basic and the options out there suck. But if you took some of the designs of the better 4age headers and made it to fit the 4af/4afe you'd be better off.



Doubt something like this will fit in the area for the ae92 but you could measure it out and maybe do something that none of us have

it's an ae86's header



This is a 4afe header for the ae111 apparently which would also be a neat idea





From what I recall you want to keep all the runners on the header the same length and maybe make it a 4 to 2 to 1.

[NZAE92]

cool.
i have a bigport 4age bluetop header that i can go off aswell but i might still need to take the exhaust manifold off.
but it doesn't help that everythings welded together maybe only the down pipe and that are welded idk haven't had a good look. umm oh i will take those pics and have them for next year its good thinking ahead for this sorta stuff .
how many inches should i make it? what is the stock diameter? and will i want it straight through?? it will still need bends in it aswell oh and crap insurance might need to be called i hope not lol
thanks for those picks freakinabox oh and i've always wondered what people mean by 4 to 2 to 1 i know its a ratio of some sort like 4 ports to 2 pipes to one outlet.
and thanks everyone else for there input too

[Donald]

4-1 is 4 head pipes comming together into 1 collector, and then you have 1 pipe from there.
4-2-1 is the 4 pipes itno 2 pairs, then those 2 pipes into 1 further down.

4-1 is best for top end horse power, and you lose low end torque. You don't want that. That is best for high RPM all out racing.
4-2-1 is better for low to mid range torque, and that would be the prefered setup for street use.

The pairing of the pipes is important too. I can't remember what it should be off the top of my head, but it needs to match the firing impulses of the spark plugs. You don't want 2 consecutive firing impulses paired together.
I think 1+4 and 2+3 should be paired. Somebody correct me please if I am wrong.

The length of the pipe between the head and the "Y" is important, I think, also the distance to the next from the first "Y"s to the next.

Find yourself a book on building exhaust manifolds before you start.

[canadianae92]

4-1 doesn't mean top end horse power/ low end loss... its all about extractor length and sizing to achieve desired power range among other methods

4-1 flows better than 4-2-1 in most cases, saying 4-2-1 is better for street use is a marketing ploy because 4-2-1 headers are just easier to manufacture and design while maintaining a nice flow but there are the cheaply made 4-1 out there that are even cheaper to make yet but will normally hurt performance because of shitting piping and collector design as well as improper runner pairing

4-1 needs a more advanced design to reap the real performance out of it for the target power range... 4-2-1 can maintain heat at lower revs because of the early exhaust gas joining which helps with scavenging and the rate of flow

large sized and long 4-1 extractors would be for high revs with an early exhaust exit because they can maintain heat at the target range and therefore flow and scavenging(you can take a look at formula atlantic headers if you want to know what I mean) they would cool exhaust gases fast at low revs and hurt performance in that range

blahblahblah

have fun modifying that factory manifold, aren't they cast iron? lols

ill post an example of a terrible 4-1 header tomorrow or something

[Donald]

Originally Posted by canadianae92

4-1 doesn't mean top end horse power/ low end loss... its all about extractor length and sizing to achieve desired power range among other methods

4-1 flows better than 4-2-1 in most cases, saying 4-2-1 is better for street use is a marketing ploy because 4-2-1 headers are just easier to manufacture and design while maintaining a nice flow but there are the cheaply made 4-1 out there that are even cheaper to make yet but will normally hurt performance because of shitting piping and collector design as well as improper runner pairing

4-1 needs a more advanced design to reap the real performance out of it for the target power range... 4-2-1 can maintain heat at lower revs because of the early exhaust gas joining which helps with scavenging and the rate of flow

large sized and long 4-1 extractors would be for high revs with an early exhaust exit because they can maintain heat at the target range and therefore flow and scavenging(you can take a look at formula atlantic headers if you want to know what I mean) they would cool exhaust gases fast at low revs and hurt performance in that range

blahblahblah

have fun modifying that factory manifold, aren't they cast iron? lols

ill post an example of a terrible 4-1 header tomorrow or something

I don't know enough to agree or disagree with you, but your arguments seem sound. I do know enough to believe it is more of a science than I wan't to mess with, and chance making things worse instead of better.
I'd rather go rebuild an automatic transmision.

[freakinbox]

ugh the idea of messing with an automatic transmissions scares the crap out of me. Just seeing them dismantle and reassemble one on tv makes me go cross eyed. Then they start modifying the valve body I just want to blow my brains out lol. I'd rather make a header...

Just to clear this up as well, with a stock motor the header is almost pointless. Bang for your buck there are better things to buy. I keep pointing out the exhaust mainfolds on the newer cars aren't like the ones they used 30 years ago on domestics that were a tube with an outlet somewhere along it making it horrible and unefficient. Ours run down from each cylinder until they hit the outlet so there are runners... Also with the stock motors it seems like you have a choice between headers or a slightly larger exhaust, combining them is a bad idea and makes the car feel sluggish.

But in this case he gets to build it for free so why not? What is the worst he will do? make a pos and just put the original manifold back on

[NZAE92]

hahahahahh that prolly might be the case but if im determined not to make a POS then it will hopefully turn out right.
im thinking of doing the whole exhuast system in tec aswell cause it's a years worth of building and manufacturing oh and the paper work that comes with the project what diameter should i make the exhaust piping like 2 1/4 inches is that alright for a street car cause i read on a site that, that would be ideal for a street car as some race cars go right the way up to 2 1/2 to 3 inches

[freakinbox]

that's to big with a header. The car will feel weaker. With these cars stock I'd say no more than 2"

[canadianae92]

2 1/4 is fine for street my hks catback is 60mm and that must be pretty close to 2 1/4 if you want to do the math and about 60mm is the recommended size for street n/a I guess

too much piping is a restriction anyways but if its small its even more so a restriction you just don't want it TOO big because the exhaust gasses will have more room to expand and cool hotter gases move faster too small and you are choking it

on a stock motor a header is pointless if its done wrong and either way you won't see the full benefit because your motor is stock but it would be hard to not improve over the stock 4af exhaust manifold

for headers/exhaust there is always exceptions if its done right like 4-2-1/4-1 can both be comparable and a header can improve the flow of a stock motor over stock headers if its done right but it can also hurt performance if its done wrong...

[freakinbox]

that is where I have noticed one of the best gains, I know most people will say it's fake or stupid. But taking off the stock muffler and putting on a straight through. I have the same deal, other people also like how the car sounds. Something with the 4af where a muffler not being there or almost not being there makes the car sound good. Seems like the general idea on here is that 4age's are not like that.

I also noticed even before the muffler I put on, or before the stock one rotted away. The motor on that car are higher rpm is loud as all hell on it's own.

[NZAE92]

so 2" straight through would be fine??
or should i keep the muffler i don't want it too loud cause the police will pull us over for being to loud but it can be silenced aye??