SmallPort vs Bigport HEAD 4AGZ/TE power figures

[The Witzl]

i think you have a very misconstrued perception of what TVIS actually is....

[myne]

Its a system that blocks 1 of 2 inlet runners per port below ~4400rpm, resulting in the remaining runner gaining increased airspeed, for more complete cylinder filling at lower RPM.
Since each runner is more or less associated with a port, with a small adjoining area, what I said should, in theory have more or less the desired effect. No?

[oldcorollas]

Its a system that blocks 1 of 2 inlet runners per port below ~4400rpm, resulting in the remaining runner gaining increased airspeed, for more complete cylinder filling at lower RPM.
Since each runner is more or less associated with a port, with a small adjoining area, what I said should, in theory have more or less the desired effect. No?

the runner is blocked.... the ports are joined and cavernous

it's an interesting idea, but perhaps having both valves open, and yet a higher velocity, would be better... like it is stock...

[myne]

Yes... but with different cam grinds per valve

[nick.parker]

Hi,

Thanks for all the responses. I am running 14 psi to get 150rwhp @ 6900rpm. Probably my goal would be to get as close as possible to 200rwhp, without compromising drivability, and without going to turbo, but that nots completely out of the question down the track though.

I like the improvement in top end the 267s cams gave, but feel I may go for a smaller inlet cam to reduce overlap and get back a little more low end. So I think head design / work might become important for power if going to shorter duration cams?

The problem with installing TVIS is all my custom pipework is based around the inlet manifold bolting up without it, so it would be a bit of work to change...actually I would have the same issue with the smallport manifold too.

See a pic here:
http://e-wire.net.au/~nrparker/MR2/N...new_engine.htm

Regards, Nick.

[oldcorollas]

without changing head and manifolding, you could do a quick n dirty test by filling inthe ports and runners with epoxy as Dimitri suggested. as long as non gets ingested during the testing period, you can quickly see what difference a 15% reduction port and runner area gives...

[myne]

While you're doing that, you could also try making a thin tin temporary "gasket" that blocks half the ports just to test the effect tvis would have on your setup.

[Nim]

Yes... but with different cam grinds per valve

What? Why would you do this? This does not sound like a good idea to me.

[Dimitri]

if you want to retain your existing inlet manifold and use a small port head you can buy an adaptor from techonotoytuning.com . not trying to sell one to you but they ship to 0z alot and are great to deal with.

if you really want to make an improvement but keep your bigport head i can get you flow figures from one we did for testing. this has some pretty serious work including fill (epoxy) in the floor of the port, 3 angle intake valve seat cut, radius cut on the exhaust.

can also supply figures for similar porting but with 1mm o/s valves(7m or 5s, cant remember which ones he ended up using).

probably will post both flow charts for these plus comparison to small port head with same mods once hes all done, which should be pretty soon.

[nick.parker]

Hi Dimitri,

That would be some fantastic information. I will look forward to hearing. I have been wondering if slightly larger valves could be a good thing too. I have read a few experiences from the internet of people who have done this, one with a supercharged AW11 like mine with a formula atlantic sized valves fitted...he said it 'hauled' over all the other SC's at a track day......


Regards, Nick.

[oldcorollas]

if you want to retain your existing inlet manifold and use a small port head you can buy an adaptor from techonotoytuning.com . not trying to sell one to you but they ship to 0z alot and are great to deal with.

if you really want to make an improvement but keep your bigport head i can get you flow figures from one we did for testing. this has some pretty serious work including fill (epoxy) in the floor of the port, 3 angle intake valve seat cut, radius cut on the exhaust.

can also supply figures for similar porting but with 1mm o/s valves(7m or 5s, cant remember which ones he ended up using).

probably will post both flow charts for these plus comparison to small port head with same mods once hes all done, which should be pretty soon.

mate i'd be wrapped if you could even post vague info regarding bigport vs small port flow figures, especially after modding.
my plan is to run small port with up to 18-20 psi boost to begin with.. and startign with small port and enlarging ports as we go

[Rallystanza]

mate i'd be wrapped if you could even post vague info regarding bigport vs small port flow figures, especially after modding.
my plan is to run small port with up to 18-20 psi boost to begin with.. and startign with small port and enlarging ports as we go

I am building a 4AGTE at the moment, in regards to the head, I am using a smallport GZE head, A Bigport inlet manifold sans TVIS being replaced with a port adaptor from T3.

The head is receiving a fair old port and polish as well as running Wade 272 deg cams as well as upgraded valve springs,

I will be running 20-25 PSI of boost pressure.

When the car is all up and running reliably I want to experiment with switching to a cut and shut smallport inlet manifold, without T3 plate of course, and also working on the tracts of each manifold to see the results of each.

This is all a long way off but I will be sure to post result as I find them.

At first I thought the design of the T3 port adaptor could be restrictive, but the way it is designed could work quite well with aiding the forcing of the air into the head. But as I say, I want to check it out when its all running.

Cheers,

Jeremy

[Dimitri]

ill start a new thread when with the imfo when i get it.