best turbo head what do you think

[Stealer Of Souls]

9.2:1 engine 14psi big port head was 176kw @wheels
same engine 8.0:1 small port head 183kw @wheels

Now that's compelling evidence...

Bigger ports actually slow down the charge, the benefit of speed is that air has got inertia and with higher velocity more air will enter, thus taking advantage of longer duration (remeber the valve is still open when piston starts compressing the air, to allow more air to enter due it's inertia). Even with turbo the flow of air is not continous, so wave physics plays more than people give credit to.

Okay this is probably gonna turn into a whoflungdung affair but...
I was under the impression that forced induction negated the majority of the issues associated flow velocity. Therefore the aim was to achieve best flow rate.

[Mr Revhead]

i know what your getting at....

the thing is for most applications the bigport head is actually too big.

hence why i suggested 45psi and metahanol

[sergei]

Even with forced induction, the air still comes in pulses, with every pusle there are high pressure/low pressure fronts, with the pulse propagating it's own inertia is very important, thus the port velocities still apply.

[pc]

9.2:1 engine 14psi big port head was 176kw @wheels
same engine 8.0:1 small port head 183kw @wheels

nuff said

umm.. why the CR difference?? has the small port head got a really large combustion chamber?
With those differences in power I would think a 3.8% difference on different days could be error... atmospheric conditions etc.

[Drifter4ag]

different headgaskets

[trdfxgt]

hmmmmm should i just toss a coin ha ha ha i think ill go with the small port as there are other benifits such as the oil return and manifold does not require removal tvis i think in happy with that thanks for all the info guys

ps crnkin should i go for the small port ?????? ha ha

[Stealer Of Souls]

hmmmmm should i just toss a coin ha ha ha i think ill go with the small port as there are other benifits such as the oil return and manifold does not require removal tvis i think in happy with that thanks for all the info guys

Yeah. The smallport is definitely not worse than the bigport, if anything it's an improvement, so why not take the external drain! Oh yeah. TVIS is just a plate that sits between the manifold and the head. So easy to remove...

[crnkin]

9.2:1 engine 14psi big port head was 176kw @wheels
same engine 8.0:1 small port head 183kw @wheels

nuff said

umm.. why the CR difference?? has the small port head got a really large combustion chamber?
With those differences in power I would think a 3.8% difference on different days could be error... atmospheric conditions etc.

or the head could flow 20% better velocities.....


SMAAAAAALLLLPORT

Honestly, less taking, more doing.

Use the smallport and go away










hehe u dont have to go away

[ROBODISCO_20v]

Why don't you try a 20v head with the quads & a custom phlenum.
Would be even better than a small port 16v

[trdfxgt]

$$$$$$$$$ thats y and i allready have both a small port an big port head

[crnkin]

I wasnt even going to comment on that but why go for a silvertop when we are discussing a bigport 16v head to flow too much.

At least his car has modified gear ratios for circuit racing

[strx7]

Have a friend building a 4AGTE at the moment and we have the option of using either a bluetop bigport head or the factory 4AGZE (AW11) head. Its running a T28 and has 60 shot of NOS and LARGE injectors, where is the 'cut off point' between the heads as far as target HP is concerned?

Cheers

[Mr Revhead]

they are the same head

[strx7]

AW11 4AGZE is a TVIS type head???

[Drifter4ag]

yeah they are the same head

[crnkin]

I like head

[ROBODISCO_20v]

I wasnt even going to comment on that but why go for a silvertop when we are discussing a bigport 16v head to flow too much.

How can you have to much flow when turboing

[EVLGTZ]

I wasnt even going to comment on that but why go for a silvertop when we are discussing a bigport 16v head to flow too much.

How can you have to much flow when turboing

You need to put it into context with what the original poster was after.
Just a very basic low boost low power setup around 200hp. The smallport head suits this type of application.

[craigt]

SMALLPORT!!!!!!!!!!!
Had them both on a flow bench playing round with a velocity probe.
The large port gets turbulence because the area is too large.. and we are talking big block chev large. Redmist has a TWR modified cylinder head that was based on a largeport but welded up so that it is smaller in the runners than a smallport!!!! Do you want to argue with Tom???