inlet ports

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

after all the discussions about inlet port sizes on the F7 series, i thought this was quite relevant. Was looking at a page detailing the rebuild of a toyota 4AGE 1.6 MR2 mk1 engine. here's one of the pics

ports look of a similar size to the F7P/williams F7R, looks like the toyota engineers also felt that this port size was necessary...

comments?

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

Is that standard do you know??
That size port will be good for power at high revs. it depends alot on the shape/design aswell tho, as to how it performs elsewhere. also bore/stroke ratio will determine the mass flow at a given rpm, so affects required port size.

Also valve lift...if you want good gains with high lift, you need big valves (ref: L/D=0.25 blah blah) which means larger ports.

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

that is standard yes, rev limit is 7k or 8k on JDM ones i think. It's only a 1.6 too.

how comes the bore/stroke ratio affects the mass flow at a given rpm? isnt it just the capacity that will determine the mass of air drawn in per cycle, regardless of the bore and stroke which give that capacity?

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

Sorry, meant to say gas speed!
But it would have an effect on mass flow anyway due to volumetric efficiency

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

ok but how come the gas speed is dependent on bore/stroke ratio then? surely thats a function of valve area and mass flow, which itself is determined by displacement?

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

stan wrote:

Also valve lift...if you want good gains with high lift, you need big valves (ref: L/D=0.25 blah blah) which means larger ports.

so how come you've gone out of your way to find a megane head with smaller ports when you're putting in bigger valves?

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

shorter stroke=lower mean piston speed=low mean gas speed...conversly, greater stroke=greater mean piston speed=greater mean gas speed

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

Neal 19 16v wrote:

stan wrote:

Also valve lift...if you want good gains with high lift, you need big valves (ref: L/D=0.25 blah blah) which means larger ports.

so how come you've gone out of your way to find a megane head with smaller ports when you're putting in bigger valves?

bigger valves= greater mass flow rate, smaller ports will increase gas velocity

what i meant was, if you want to run high lift, more often than not you'll need bigger valves

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

stan wrote:

shorter stroke=lower mean piston speed=low mean gas speed...conversly, greater stroke=greater mean piston speed=greater mean gas speed

yeah but for a given capacity cylinder, the volume swept per unit of crank angle will be the same regardless of stroke or bore, will it not?

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

if the volumetric efficiency was the same at a given engine speed, yes. but it wont be due to gas speed.

but that isnt what you asked originally!!

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

what did i ask originally? Smile

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

Neal 19 16v wrote:

ok but how come the gas speed is dependent on bore/stroke ratio then? surely thats a function of valve area and mass flow, which itself is determined by displacement?

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

god your frying my brain man!!

ive been sat at my PC for 3 days solid doing an assignment on stress calculations of piston,con-rod, and crank assemblies...i keep seeing excell spreadsheets ive done every where i look !!

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

ive lost track of what it was that i was unclear on now... Confused

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

lol!!!

you were asking why bore/stroke ratio effects gas speed....
because with a longer stroke the piston travels faster, thereofre the air travelling behind it as it goes towards BDC moves faster. this means the VE for a large stroke/small bore engine will be different to that of a large bore/short stroke engine, even at the same rpm

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

oh yeah. i dont see why the gas speed at the valve will be different for different bore:stroke ratios.

Will two 2L engines identical in every way except the bore and stroke have different gas speed at the valve?

Retroholic Joined: 12 Feb 2004 Posts: 5685

WHOOOSSHH

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

indeed.

Retroholic Joined: 12 Feb 2004 Posts: 5685

You seem to be handling it much better than me

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

yes thats the early 4age head, but the later ones went to small ports because toyota realised we have been a bit stupid here!

I am not going to get in the way of you 2 ladies, well 1 lady the other a gay man, fighting, I find it amusing.

But I would pick a smaller port head every time.

i will see if i can find a pic of the later toyo head

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

well what do you know

typed in toyota 4age on google and th e1st page to come up

http://www.users.bigpond.com/vidore/toyota_4age_engine.htm

read the bit where it tells you the generations, 4th gen is when the ports were narrowed. Also this is the head the tuners go for due to the far superior power available from it throughout the rev range.