Know how I know ricers don't know a single fucking thing about performance? Heads...

A lot of cars have great heads stock
Old ass smog era V8s dont but most modern DOHC engines have amazing heads from the factory

Boost can overcome shit head flow but boost with good head design is much better
If anyone talks about making their car fast without talking about suspension they are a moron

retard, read the post it says i have a ported and polished head

I mean you won't get serious gains, but for a light car even a small bump in power is noticeable. Just as long as you aren't sperging out on $4k fabspeed exhaust systems
Chinks make Fabspeed header clones with good enough welds, just gotta do a little modification to make them seal right. And ceramic coat them. $200 vs $1000

Oh and in regards to a 911 engine swap, an LS swap is more cost effective for a couple grand more

The heads still need to be milled they flow fine but the compression is usually shit.

Fuck no.

Hell, I know for a fact that you can literally take the entire 987 Cayman exhaust system and run it. You might have to lengthen o2 sensor wires though. Those take offs from 987 owners upgrading are usually pretty cheap

Lighter and flows better than stock, though obviously still catalytic inhibited.

But on a real note, I was talking to Raby at Flat 6 one time, with a 3.2 you could see 230-240 at the wheels with that mild shit and a proper, not mail order, tune.

>Old ass smog era V8s dont
The heads in these engines weren't the bottlenecks, it was the horrendous compression (sometimes worse than the ancient flatheads), crude electronics, and the sweeping use of EGR that made some of these engines dogs.

/thread

Yes, heads are part of the performance formula. And money being no object, basically every build should have head work included, shaping/blending/porting/bowl work/etc.

Money being an object, fancy head work isn't usually the best value. And without sending a head to a specialist for said engine, it can be a real gamble. Make magic numbers on a flow bench, loose peak velocity, mid-range is ass.

This and it's worth saying that aftermarket heads (if there is an aftermarket for your car) are usually good $/hp ratio.

wow you gave back your leased piece of shit and bought someone else's problem car. seems like you know alot about cars.

just head delete. all that metal gets in the way of flow

Small ricer motors won't gain much from a good head because they're so small. Going straight to power adders is the best bang/buck. And most modern heads are pretty good anyway. If anything get a bigger cam.

>heads
Since ricers usually run DOHC pentroof heads with variable valve lift and time there is not much to gain on these parts.
Individual throttle bodies, short intake runners, higher compression, longer valve times with higher overlap and a higher redline each make much more of a difference on these engines than new heads.

If you get fast enough, even a ram air intake might actualy work better than new heads, but that is just for german highway pulls in excess of 250km/h...

>static flow chart
These don´t actualy say much about the head.
Static flow doesn´t realy matter, dynamic flow is much more important.
For example: some companies managed to get their volumetric efficiency over 100% due to the better dynamic flow performance of their heads and intakes instead of just looking at static flow.

That is why engines like the famous F20C generate more than 100 Nm/L while beeing shit in static flow test.

>He doesn't realize modern twin cam 4 valve per cylinder motors already flow far more air than they need to from the factory

Ricers don't work on their head because their "riced out" twincam heads already flow more than enough air for a substantial horsepower increase.

I am literally creaming my jeans right now

>tfw cam only swap nets 30+whp
Yes heads swap will definitely increase power as well but not being a displacelet helps.
What size is your civic motor OP?

yeah on a large displacement pushrod engine definitely, especially since a smog example can be picked up for peanuts, the heads were restrictive, often had something called peanut ports, the exhaust flowed horribly, the compression levels matched those of flathead engines, head work definitely does a lot for those old smog motors

you shouldn't have to put heads on anything made after 1997 because that's when gm finally got on the ls boat which flows almost as nice as dohc which pretty much everyone had by then

but....hardly anybody works civic heads because they are good enough from the factory that any gains to be had are expensive to get

???

Head work is expensive, time consuming, and risky if you do it yourself.

It's the last place you should work on. you don't even need to touch the head until it becomes a bottleneck for forced air and more aggressive cams.

Those are unrelated to the engine though. Great mods by themselves, but OP's point, although poorly worded, is mostly that heads get ignored when building an engine.

>Power adders
I assume you're talking about boost here. When boosting a car, it's always much safer to upgrade the head as well. Think of the head as the restriction in that case, and the more boost you add, all you're doing is adding pressure through that restriction: you're making more PSI. Compressing your intake air more always means that you're losing power: it'll make for higher IAT's, and it'll make your setup more prone to detonation. By doing a good head job, you can make similar amounts of power at a lower PSI level - much safer, and if you turn up the PSI, your bottom end or fuel system can then quickly become the limiting factor for most engines.

Also, exhaust head work can improve throttle response and boost threshold on turbo setups.

There's an awful lot to gain on most DOHC head with a good (CNC) porting though. They're roughly cast in most cases, and good portwork can make all the difference in power and throttle response, especially on turbo motors.
ITB's, trumpets, a cam swap and a higher redline (ECU tuning) all make more power, sure, but when you're building an engine (and increasing the compression) you really want to make sure the head doesn't become the bottleneck. Unless you've got an amazing factory head design that comes CNC-ported, you're usually leaving quite a few ponies on the table if you don't port your head.

A decent 4-AGE head makes ~230cfm @.500 after porting. That scales to roughly 290 cfm if it had a 4'' bore, pretty substandard when you compare it to a decent 4'' LS head that does well over 310cfm at the same lift.
Before porting, you're looking at roughly [email protected] - roughly 240cfm when you scale it to 4''. Not exactly great.

>987 airbox
>straight and insulated intake piping
>bored throttle body
>Y splitter in plenum
Why not just buy a set of ITB's then?

>i have a ported and polished head
Which is pretty useless to say unless you've had it tested on a flow bench. For all we know it was done by a V-ate goober who just hogged out the ports and got zero gains.

Dynamic flow is mostly a combination of high compression bottom end, good static flow, and cam size and timing. It's also pretty hard to measure, and static flow is easy to measure.

The F20 is pretty good at static flow tests though, easily making 300cfm. It's got really poor air velocity below 4-5K RPM though, since it has pretty big ports for it's displacement. That makes for some bad throttle response, but hey, it flows like a champ at higher RPM.

Don't forget cams.

>modern DOHC engines have amazing heads from the factory
I'd say good, not amazing. There's still room for improvement on any cast head that isn't CNC-ported from the factory.

Too bad the LS never came as a flat 8.

You don't have to work on them though. YOu can buy aftermarket heads, or get 90% of the improvement with a good CNC port job.

there's room for improvement on any setup but for big power heads are one of the last things you need to upgrade on a modern engine, head work being a staple is due to smog causing every american engine made from 73-97 to have awful flow

>A decent 4-AGE head blah blah blah blah blah blah

The reason I chose that picture is because the 4age big port has ports which are too large and according to the 4age man (billzilla) under 200hp you'll actually make more power by filling the ports in a bit (making them smaller).
It's a bit like the classic 4v clevo head where if you're not dry sumped and revving to 7500rpm you're better off with smaller ports.

Now that's not to say the ports are perfect - they'll still want a bit of a clean up and maybe even a reshape but you'll get fuckall power for a huge cost compared to other modifications.

Also were you seriously just comparing the flow of a 4AGE head to an LS1 head? When a 4AGE has almost half the displacement per cylinder?

b16 heads are already good enough

>When a 4AGE has almost half the displacement per cylinder?
The nice thing about static flow testing is that you can just ignore what's under the head. All that really matters is how much air you're pushing through that head either per valve size, or per bore size. Flow per bore size is pretty much the industry standard for head flow efficiency where I work. Note that all of these should be at the same valve lift in order to scale properly. 0.500'' is a good starting point.

4-AGE has a 81mm bore, 4'' (~102mm) is roughly the standard for US small blocks (e.g. LS2). The LS is actually 3.9'' off the top of my head, so slightly smaller.
A stock 4-AGE flows about 190cfm/ Divide by 81, times 102, and you end up with about 240cfm if you'd scale the entire head to fit on a 4'' bore 4-AGE.
A ported 4-AGE flows about 230 cfm. Divide by 81, times 102, and you end up with about 290cfm if you'd scale the entire head to fit on a 4'' bore 4-AGE.
A factory LS1 head (keep in mind, those are 20 years old by now) flows something like 230cfm stock. Pretty much in the ballpark of a stock 4-AGE.
A good LS1 ported head flows about 310-320cfm @.500''. A bit better than the 4-AGE, but then again there's a big market for them. You could cheat a bit and go upwards of 340-350cfm, but you'd need more valve lift (.650-.700'') for that.

tl;dr you can compare the efficiency different sized heads when you scale them accordingly

You know stroke matters too right?

Not really, since all testing is usually done at a standard pressure differential (28'' of H2O).

The only place where stroke matters is on dynamic flow, but it's completely isolated from static flow as tested on a bench.

stroke also affects torque, an engine with a long stroke will have more torque than one with a shorter stroke

I think we're talking about flow here, mate.

>muh standardized testing

Let me put it simply for you
>longer stroke
>more distance for the piston to travel
>at the same RPM the piston must travel faster to cover the longer distance
>head needs to flow more to allow the extra air sucked in by the piston traveling faster in order to cover the longer distance of the bigger stroke

So no, you can't compare the flow of a ~400cc per cylinder head to a ~700cc per cylinder head. Maybe your standardized testing works amongst American V8s because they all have roughly similar bores and strokes and engine characteristics in general but it doesn't work when comparing to a 4 valve per cylinder twin cam.

I know how an internal combustion engine works. Exactly because strokes and bores are different, you want to standardise your testing so you can compare heads of different sizes. You scale the stroke by always using the same pressure differential, and you scale the bore after you've got your results, and you keep the valve lift the same if you want to compare results between different heads. If you want to improve your own heads, you simply keep modifying at the same bore & pressure differential, and you look for bigger cfm numbers at identical lift levels.

In static flow testing, all you're doing is flowing air through the head. There's no stroke, and no bore to matter, although the latter does determine the size of your head which means you need to scale it.

>Maybe your standardized testing works amongst American V8s
Nope. Since you can really eliminate all the other variables, you can even use it for testing 50cc scooter heads (35-40mm bore) and mountain motors (127+ mm bore).
>because they all have roughly similar bores and strokes
Not really, since those bores can be anywhere between 3.5 and 4.5 inches.

Also, valve actuation doesn't matter in flow testing. Unless the camshaft is directly in the port (if it does, you've got a problem right there), it doesn't matter. You're just setting the valve at X lift, and testing flow. One advantage that multivalve engines do have, is more valve skirt. That means you can get pretty good cfm with a relatively small port size, which means high air velocity throughtout the entire lift range - important if you want good throttle response.
The nice thing about the added valveskirt in multivalve engines is that it doesn't come at the expense of as much reciprocating inertia as you get with a 2-valve setup, which ultimately means less valvetrain inertia and a potential higher redline (if your bottom end or head cfm aren't the limiting factor). However, it does mean that multivalve engines usually are subpar in efficiency per valve circumpherence, which is the second industry standard for head efficiency I know of. That makes it a pretty bad standard at comparing multivalve heads vs. 2-valve heads though, since it downplays the efficiency of a multivalve head. Therefore, you should use cfm per bore size instead.

You still don't get it.

A BIGGER STROKE NEEDS TO FLOW MORE CFM.

Nope. As long as piston speed stays the same, then you're pulling the same amount of air through the head. You're generating the same pressure differential - which is standardised in flow bench testing.

A bigger stroke can use as much cfm as a shorter stroke at the same piston speed. This just means it's at a lower RPM.

>This just means it's at a lower RPM
Finally we're on the same page.

So:
>most performance 4 valve heads already flow more than enough for say ~7500rpm (Hondas do more)
>Increasing the flow will only benefit at high RPM and will actually decrease torque at lower RPM
>4 cylinders suffer from harmonic issues
>Building a bottom end to take more than 7500rpm reliably would usually be very expensive and you would experience diminishing returns on your gains
>Since the head already flows more than enough for reasonable RPMs (we've established that now)
>Much better to slap a turbo on and keep the revs under 7500

Understand now?

I'm the other guy, not him, but a lot of this stuff can be had and set up easier and cheaper than ITBs, for starts. Just take it all of a 987 and 911

>having shitty heads from the factory

just pushrod things

>>most performance 4 valve heads already flow enough
More flow is never a bad thing though. After boltons and tuning, the head usually becomes a bottleneck, so you'll want to upgrade that.
>>Increasing the flow will actually decrease torque at lower RPM
Only if you add huge amounts off port volume, which lowers air velocity. Proper heads increase power throughout the RPM band.
cylinders suffer from harmonic issues
So? You can build around that.
>>Building a bottom end to take more than 7500rpm reliably would usually be very expensive and you would experience diminishing returns on your gains
It's not 1990 anymore, 8K RPM on a built motor isn't impressive. If you desperately want lower RPM, just slap a stroker kit in, which is getting ridiculously cheap nowadays. You'll need a better head to take full advantage of that, though.
>>Since the head already flows more than enough for reasonable RPMs (we've established that now)
That's, like, you opinion, man.
>>Much better to slap a turbo on and keep the revs under 7500
Slapping a turbo on a bad head is the fastest way to excessive boost levels and IAT's. A good turbo setup is most efficient when combined with a good head. You're squeezing more air through a better air pump, which makes it even better.

Jesus you just won't give up will you.

THE ONLY WAY YOU WILL MAKE A SUBSTANTIAL POWER INCREASE OUT OF A MODERN PERFORMANCE TWIN CAM 4 VALVE PER CYLINDER ENGINE IS BIG RPM.
Which = $$$$$$$, bad driveability, bad torque and fuck all power increase.
Ricers add turbos because it's the cheapest, most reliable, smartest way to make substantial increases in power.

And the reason for all of this? The heads/manifolds already flow pretty good - they are not the restriction. Just because heads gets you more power on your V8 doesn't mean it's the same for every other engine.

Another way is to add displacement, which is getting pretty cheap nowadays.
If all you're doing is adding RPM, sure, stuff gets horrible for street use quickly. It shouldn't be your only goal though.
Turbos are seperate from this issue though. Like I said, a good turbo on a bad engine is a bad idea. You'll get a lot more response out of something that's properly built, especially with the added exhaust flow of a good head.

Up to your standards, maybe they flow good. For somebody working with significantly better engines, they don't, and you can clearly see meat left on the table for any factory head that doesn't come with CNC porting. I don't even work on V8's, most of my design work is inline fours (both motorcycle and your regular 2L 16v DOHC units).

>Dynamic flow is mostly a combination of high compression bottom end, good static flow, and cam size and timing
It is more than that, there are resonance effects coming in and changing everything depending on rpm, wich allows some engines more than 100% volumetric efficiencys at certain rpms.
>It's also pretty hard to measure
Indeed.
>F20C performs bad under 6000rpm
That is kind of the point of a high rpm engine, it is desinged to run around 8000 rpm.

There are heads with better static flow than the F20C, but way worse dynamic flow.

>There are heads with better static flow than the F20C
It's hard to think of any 3.4'' bore head that'll flow 330cfm@12mm though. That's roughly equivalent to a [email protected]'' for a 4'' bore (LS2), which is might impressive.

Resonance (usually Helmholtz) is determined by intake tract length (actually volume), which means it's easy to optimise for several specific points by just changing intake manifold geometry. Good resonance tuning is indeed key to high volumetric efficiency.

>Resonance (usually Helmholtz) is determined by intake tract length
Not only that, there are also other dynamic effects.
This stuff is so complex, that even modern CFD programms struggle to be precise.

What about cars where the head is not a restriction in the first place?

Yeah sure man, two valve heads with swirl ports flow just fine.

Dropkick.

>swirl ports
Wasn´t that a diesel thing?

Power to ALL the wheels is better than only using two. Not a bad Civic. Still wouldn't touch a stock evo on track or offroad. Maybe in a straight line if you're one of those faggots.

>I heard over time the Bosch ECU would self tune
It may have long term fuel trims which are meant to correct changes in fuel injector flow rates over time due to expected wear.
It won't correct the 'VE or target air fuel ratio, nor the ignition advance.
Closed loop fuel correction is likely to only be at steady state driving too.
Just hope it doesn't have a maf, because you're really fucked if it does.

That's copypasta you idiot

If it has a regulated catalythic converter, it tunes the A/F ratio almost perfectly stochiometric based on oxygen sensor data.

>being this new

It's also very much a smog era thing too.

And people think the heads of the smog era motors flow just fine....

>More flow is never a bad thing though. After boltons and tuning, the head usually becomes a bottleneck, so you'll want to upgrade that.
This is the part that's wrong. Any JDM performance engine flows too much for NA operation. If its a stock turbocharged engine then it's a different story.