benifets of 20v head over 16v head turbo'd

[pro-16t]

Yes i've searched high & low. Put aside rigoli's 20v turbo 405hp AE92, or yogi8u celica, 20v's should be left N/A or fastest et's whatever & i've searched old forums too! What are the real benefits of 20v head turbo'd has someone here had experience with both heads? as i have read it seems the 16v has superior flow capablities over the 20v or am i wrong? Internally which head is better suited to forced induction, having an extra valve per cylinder, vvti & quads puts it ahead in terms of technology but in all honesty going to be reliable to drive & get that many more kw?

Aiming for 200kw+

Here are my specs for gte

T28 bb
16v bigport head
mild port & polish
heavy duty springs
custom cams
custom plenum
ae101 block
shotpeened & linished gze rods
ACL forgies
full balance etc.

or
T28 bb
20v head
mild polish match port
lapped valves
quads welded up for runners
rb20 throttle body
custom plenum
ae101 block
shotpeened & linished gze rods
ACL forgies
full balance etc.

[30psi 4agte]

Its a touchy subject.

Pro's and con's for each have greatly been debated with no real out come.

In summary the 20v head will out flow the 16v big port in std form but the 20v having 3 inlet valves has almost no room to upgrade to bigger valves where the 16v has plenty of room.

Will a fully prept ( o/s valves...port work tec) 16v head be better than a modified 20v head ????....... Quite possible but in the end it comes down to how far do you want to go/ how much money do you want to spend ?

The 16v head will allow you to run more radical cams than the 20v as there is more room for larger lobes in the head. ( the 20v having the 3 inlet valves leaves minimal room)
Not to mention the smaller base circle of the 20v cam buckets restricting cam profile also.
So the 16v can gain ground here.

If you basicly want the max performance from the turbo 4a with the least amount of modification/ money spent then go for the 20v as its better straight out of the box so to speak.
Do you have a 4age already? if so what head do you have ?

[Billzilla]

I'd go for the 20v head.
The benefits are that they they have a much larger valve curtain area, and that's also why they flow more on the flow bench. They also suffer from flow interference, but this is far less of a problem with forced induction.
As mentioned, they can only run relatively small cams but again with forced induction you typically only need smaller cams.
They also have variable inlet cam timing, and that should help the turbo light-off faster.

[roadsailing]

if you go the 20 valve wya, don't weld up the quads!

just make a manifold that makes up to the bit that the quads bolt to, this has the fuel rail built in, and you wont be wasting a perfectly good set of throttles.

for turbo, i'd just use 16 valve, as it fits into a AE86 nicely, 200kw wont be a stretch with either setup.

[Sam_Q]

I have seen oversized 20V valves installed in a head.

Also if you do get a 20V I recomend a port job, even if its a basic one. The silvtop has some very nasty steps in the intakes

[pro-16t]

Its a touchy subject.

Pro's and con's for each have greatly been debated with no real out come.

In summary the 20v head will out flow the 16v big port in std form but the 20v having 3 inlet valves has almost no room to upgrade to bigger valves where the 16v has plenty of room.

Will a fully prept ( o/s valves...port work tec) 16v head be better than a modified 20v head ????....... Quite possible but in the end it comes down to how far do you want to go/ how much money do you want to spend ?

The 16v head will allow you to run more radical cams than the 20v as there is more room for larger lobes in the head. ( the 20v having the 3 inlet valves leaves minimal room)
Not to mention the smaller base circle of the 20v cam buckets restricting cam profile also.
So the 16v can gain ground here.

If you basicly want the max performance from the turbo 4a with the least amount of modification/ money spent then go for the 20v as its better straight out of the box so to speak.
Do you have a 4age already? if so what head do you have ?

This is what i have

T28 bb
16v bigport head
ae101 block
gze rods & crank


This what i'm thinking of buying & doing instead

cryo tuff heat treated
20v head
mild polish, match port
lapped valves
quads welded up for runners
rb20 throttle body
custom plenum
I'm spending about 3k-5k all up.

[30psi 4agte]

If you already have a big port head i wouldnt bother spending more money on a 20v.Save it and spend it else where.

The big port head loves forced induction. In my opinion they are the better head to use when going all out on a 4a........You cant beat the size of those ports !
Note: this is just my opinion not a proven fact.

i would love to flow my head against a 20v with similar mods to see which one is the better.

[psychofox]

If you're going to use the 20V head, ditch the quads and sell for profit, get a nice large plenum made up, something bigger than 3.2 Litres capacity. Whack a single throttle body for ease of tuning (like a XF Falcon one). Something like what 30psi 4agte has would be ideal, just made for the 20V head pattern. Yu may also want to make the runners so they are inline with the intake ports, so the air doesn't have to make a 15deg turn when it hits the head (have a look at the 20V inlet vs the port angle....much improvement can be made here)

As has been said, 20V don't like large duration cams due to the size of the buckets, but you're probably never going to go over 280deg anyway, so it's not a concern. And the VVT will help the off boost response. Also don't forget that the 20V comes with larger duration & higher lift cams the the 16V head out of the box (Bigport is 240deg/7.56mm vs 20V 250deg/7.9mm) so that's always helpful.

Here's a very interesting article about an Extreme Turbo 4AGE, they chose the 20V head...

http://www.bobnorwood.com/The%20Fast...0in%20Utah.htm

[Sam_Q]

oh I dont know psychofox. I am looking to run a nissan airflow meter on mine, then all those problems are solved. Although I am sure it would be much easier to tune with a simple setup like what you sujest.

I agree with you on matching of the port angle though, it might need a bend in it to make it not stick too high though.

Also I might be wrong here but I thought when it cam to the buckets the duration was less relevant than the lift (ie: max 9.5mm was it?)

[DX20VT]

Aiming for 200kw?

I bought a standard second hand silvertop 20V from the wreckers,
put a set of used AE101 GZE pistons in it with new standard rod bolts, head studs, and head gasket,
added my modified non BB T28 turbo, and at 18psi it makes 200kw+

Timing, Tuning and water injection.

No cams, No head work, all 100% genuine toyota parts internally.

[Cameron_Datto]

From what i can see , the 20v head is only a gain if your running a massive hp turbo like Rigolis,, if your running T28 .. there isn`t a massive gain . cause you turbo is the limiting the max flow .. flow makes it go ! and boost pressure is the restriction of flow so THE 20 V might make same power at lower boost .

[30psi 4agte]

not sure if i totally agree with ya there.
This is the great debate i was talking about

The 16v head big port ports can be opened up a great deal add to that some 1.5-2mm O/S valves and you have a massive flow potential.(some will argue greater than the 20v)

Now the air speed of the 16v port will prob be slower than the 20v due to having such a large port but a big turbo running large boost will have no prob in creating air speed.

The 20v and the small port 16v for that matter perform better mostly due to the fact that the ports are smaller and they managed to achieve a greater air speed/ efficency leading to an increased cylinder volume..... hence the higer hp output.
The 20v goes one better by having an even better ability to consume all of this air with the extra flow attained by the additional inlet valve.

Its abit of a weak argument i guess and my little speal here is far from explained propperly but in the end i believe size does matter when air is being forced through a port and the sheer size of a 16v big port head may just put it infront of the 20v

[Javal]

Alot of people say, (and this is say, i don't know from practical experience, and not alot of people do anyway) that whether you're going for forced induction of naturally aspirated power, Silvertop 20v is the best route to follow.

the head design allows better flow than a bigport (which are the worst flowing of all 3 4ag heads, for the reference), and will get you better numbers with less money / loss of driveability.

with the 20v you get all the good stuff too. 7 rib block, stronger crank (than bluetop [bigport 16v]), oil squirters n stuff like that. if you do as you say you're going to and put GZE rods and stronger pistons in it, it will make a rather tough and reliable 4agte.

Josh.

[30psi 4agte]

found this :



It doesnt really proove anything ....... i would like to know where he got this info though.


Head

Which one should I use? I hear you ask. Well this is probably the biggest mistake people make when turbo charging a 4A. When people turbo a vehicle they forget the principles of air being forced into a cylinder. When a manufacturer designs a normally aspirated (N/A) engine they need to increase air speed velocity into the head to create decent hp. In order to do this they will generally make the intake ports smaller.

The different heads;
20V variable valve timing
16V small port (100kW)
16V large port (86kW)

My research on the 20V head was very extensive as this was going to be my first option. A lot of people seem too mixed up in all types of gadgetry rather than practicality. In N/A form the 20V is second to none but in forced induction it actually rates last. Don't get me wrong but the small ports and quad throttle bodies don't mix well for high boost applications and the VVT isn't a necessity with the availability of adjustable cam gears.

Next is the 16v small port (100kW) and again the flow isn't as good as the large port (86kW). What you want is a head that will get the air in and out as quickly as it can. The large port head does this well since the ports are a good 1/3 bigger than the small port and the 20V.

What I finally ended up with was a large port head that I polished and only ported on the exhaust side with larger exhaust valves.

If you are after show then use the 20V but if you want go with ability to go to a larger turbo use the 16V large port

HERE: :http://www.mr2supercharger.com/4AGTE.html

[roadsailing]

A certain matte black KE70 with a turbo ZE and a 20 valve head springs to mind (was in ZOOOOM) i think it made 300 KWATW at last count.

it would be interesting to compare it to our resdient crazy power 4AGE.

the most important thing here is to turbo anything, i dont think you will really pick the difference, research is all well and good, but turbo selection will be much more important than what head you end up using.