20V vs 4AGZE + Turbo

[Ben Wilson]

aluminium is a much better conductor of heat and will help with cooling the intake charge as compared to steel.

After the intercooler, hopefully the inlet charge will be cooler than the engine bay air so the last thing you want is heat transfer. Rust shouldn't be a problem, a coat of paint on the outside and blowby oil will take care of the inside. Aluminium is lighter and looks good though.

[CHB]

what i know from experience from local racers is that 20V Valve retainers is the weakest link. it oftenly cracks and cause the valves kiss the pistons.. there aren't many manufacturer make a refined version of 20V valve retainer.. may be you should machine it out from some harder materials...
so hope this will help..

[hybridaddy]

After the intercooler, hopefully the inlet charge will be cooler than the engine bay air so the last thing you want is heat transfer. Rust shouldn't be a problem, a coat of paint on the outside and blowby oil will take care of the inside. Aluminium is lighter and looks good though.

lol dude,using steel for an inlet manifold is dodgy,end of story.
being a welder and fabricator myself i know this,the back of a steel weld on thin material will be flakey due to oxidisation of the material cause by lack of shielding gas.
this flakey stuff will continue to break off over time and it is highly undesirable for your engine to consume it.

as for the heatsoak issue you are obviously overlooking the heat transfered to the manifold by the head.
go touch your plenum after a long drive and tell me how bad you burn your hand

[Ben Wilson]

A 20v comes stock with an insulating spacer between the manifold and head.

If you're really paranoid about the flakes, you can always backpurge the job. I just sloshed some POR-15 inside mine. Mine doesn't get that hot even with a top mount 'cooler in the back of a mr2.

[finney]

another thing to take into consideration is the positioning of the alternator on the 20v vs the GZE as the 20v has it mounted on the intake side whereas on the gze i believe it is on the exhaust side. i was toying with the idea of putting a twin screw on mine but after doing some quick figures i worked out that it would be far too expensive for the power gains.

[hybridaddy]

A 20v comes stock with an insulating spacer between the manifold and head.

If you're really paranoid about the flakes, you can always backpurge the job. I just sloshed some POR-15 inside mine. Mine doesn't get that hot even with a top mount 'cooler in the back of a mr2.

those are some excellent solutions for masking the problems created by poor material choice

[Ben Wilson]

Mainly done due to the lack of a spare $4k for a decent TIG...

So, from a cost benefit point of view if you have to buy the equipment yourself which is a better material to build a manifold from?

[oldcorollas]

those are some excellent solutions for masking the problems created by poor material choice

it's not that bad a material choice.

why did manufacturers make intake manifolds from alloy vs cast iron? (they are the only real choices they would use for casting)
1. aluminium is easier to cast complex thinwalled shapes.
2. aluminium will resist oxidation better than the cast iron.
3. surface finish on Al is better inside the ports, as you can have nicer cores as alloy has much lower melting point.
4. heat transfer from the head to the carby prevented carby icing... (remember it snows in japan)
5. cost.. although aluminium is more expensive, it requires lower temperature of melting and heat treating, and energy does cost (700degish vs 1500deg??...)
6. weight. cast iron has density around 8. alloy is around 3. alloy has thinner walls. alloy will be much lighter, esp when hanging a carby eetc off (since it is unsupported)
exhaust has to be cast iron due to poor high temp strength of alloy, but exhaust weight is supported further down..

if you are casting one yourself, you would use alloy also.

if you are making from tubing.. it really doesn't matter that much.
for example... the air to surface contact of an intercooler vs a straight pipe.. which do you think has a higher rate of heat transfer? you can do the heat transfer calculations yourself.. air going thru at a max of sayyy 300ft/sec.. plenum is 1foot? max 2ft long for the last cyl.. thats not a lot of residence time...

apart from the oxidation due to poor welding techniques and finishing after, why not steel?

[hybridaddy]

i understand what you are saying,but if we are talking about mig or stick welded inlet plenums here its way off the clock on the ol' "bodge-o-meter" in my books lol!.

there are some jobs that if you dont have the facility to do it properly you are best leaving to someone who does.

everyone has a different limit as to what they can produce themselves.
everyone has a different idea of what is acceptable and what isnt.
what you should and what you shouldnt make yourself falls somewhere somewhere between those lines

[hybridaddy]

its a silly arguement lol that really doesnt even need to be had!

[Ben Wilson]

i understand what you are saying,but if we are talking about mig or stick welded inlet plenums here its way off the clock on the ol' "bodge-o-meter" in my books lol!.

That's why I used an oxy

[oldcorollas]

true, but do you think anyone doign a half dececnt job would stick weld an inlet?
Mig yes (with back purge maybe), but stick no.

considering the crap that an engine will ingest over it's lifetime, a few flakes of oxide will not be that bad the thickness is only a few microns or tens of microns anyway, and being brittle iron oxide, will quickly break up.

it's not an argument. i was just giving the reasons why alloy is actually used...
it's a cost and complexity of casting issue.

i cannot think of any reason why steel or stainless steel could not be used as an intake manifold (assuming you clean the inside of manifold after.. but you should do that anyway

edit, as for the nice pic of the quads on page 1... aren't those black stubs steel instead of alloy? you want to use 2 or 3mm alloy for a flange plate?

[Ben Wilson]

edit, as for the nice pic of the quads on page 1... aren't those black stubs steel instead of alloy? you want to use 2 or 3mm alloy for a flange plate?

They look ilke MIGed steel to me...

[hybridaddy]

haha you guys.

there is an old saying that goes like this.
"you can lead a horse to water but you cant make it drink"
i feel it fits this thread perfectly.

now why dont you go and find me all the inlet manifolds that companies are selling made from mild steel.
and ill find all the onles made from alloy.

seriously i know you probably both have ones made from steel and thats why you will defend it to the death,but you wont find professionals doing that,and professionals are the ones we should be looking to for ideas on how we design our own product.

no offence to either of you i just firmly disagree with what you are saying

[gearb0x]

Professionals have money to burn or the right tools as well

While it might be high on the "dodgey meter" it is a perfectly acceptable way to build manifolds, alloy shits on it from a great height no doubt, but what they are arguing it is an option, which you flat out rulled out in your first post with no backing it up (hence my asking )

End of discussion here there is no doubt that alloy is better in every way except cost, but to alot of us, cost matters.

Which Pure-SX pointed out it had to be cost effective