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Bigport 4age barrys apply here


kpr

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Closest thing to a stock 4age ive had  on the dyno. if you can call a 20v a 4age,  is my blacktop 20v.   has a little bit of a port and chamber zing.  link ecu and decat, otherwise stock.  makes 102kw.  I would expect high 90's from it if was stock.   I did another one the other day similar spec with pon cams  107kw.

The least ive made on a 16v is 94kw.   which was the late bigport head,  but lots of little things add up that aren't stock. the fancy exhaust side. tune set on kill. limited accessories etc.   would say well into 80's stock

If someone has a 16v 100% stock id happily run it up for cheap,  because would be interested myself

 

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What's funny about all this is that people will instantly go "yeeeee" at one motor and "pffffft" at the other, yet you could have a redtop smallport with absolute garbage hanging off it, or a perfectly sorted bigtop and they would be completely different engines in the opposite way of what people expect.

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2 hours ago, kpr said:

Closest thing to a stock 4age ive had  on the dyno. if you can call a 20v a 4age,  is my blacktop 20v.   has a little bit of a port and chamber zing.  link ecu and decat, otherwise stock.  makes 102kw.  I would expect high 90's from it if was stock.   I did another one the other day similar spec with pon cams  107kw.

The least ive made on a 16v is 94kw.   which was the late bigport head,  but lots of little things add up that aren't stock. the fancy exhaust side. tune set on kill. limited accessories etc.   would say well into 80's stock

If someone has a 16v 100% stock id happily run it up for cheap,  because would be interested myself

 

Damn, mine ALMOST got honours for most gutless.

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On 22/06/2021 at 22:38, kpr said:

So  bigport head vs smallport

The smallport head has bit less work and 10 year ago me porting.  so at a disadvantage.   I think it will have a little bit  in it over the bigport if same same.   But pretty interesting  to see how close they are all the way through.   same bolt-ons & cams.

 

valve sizes are the same yeah? so limiting factor = valve curtain area and valve seat diameter rather than port/chamber/etc.?

 

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yeah valves ,chambers, exhaust side the same as smallport

After being modified  the port is pretty similar from the valve back up to the port divider. short turn is basically the same.   so mostly only the dead space before the port divider being the major difference .  which doesn't seem to be an issue.   Seems the issue is, people think its an issue and make manifolds to suit the big opening. which will result in power loss esp in the bottom end.     the bigport heads have a lefty and and righty port, which is how it gains the bigger inlet area. this kinda runs down past the port divider a bit.  This and a few other little bits is why i say the smallport should edge it out, as can get a nicer shape without adding material

Im talking the early modified head here.  The late bigport head could be improved upon, but will always be the worst choice factory or modified. unless the port is filled and reshaped.

 

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Love watching all your vids! just abit jealous of your dyno! haha

I may have missed it but if it's not too late, how about a run with standard intake on bigport head with 193 cams? I found the smallpot version and it's quite impressive to see ~120kw with the factory intake, guessing bigport will be the same but curious to your thoughts?

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Yeah i'm pretty sure it will have very similar results.  Kinda shows its all in the runner length.  itb's not going to make much more power unless the runner length/size can be improved on.  In 4age's case thats a big yes, but most people dont.   Itb's make the engine run a whole lot nicer than the single also

This graph is picking holes in other peoples stuff...

blue; current junker bigport 193b engine
red;   smallport with with itb's,  headers, exhaust  193b cams   (so same bolton wise on paper as junker)
purple;   20v blacktop  stock headers, some kinda different  trumpets,  exhaust,  tomei poncams

 

 

1068809337_zacvsbigportjunkervssjesse.jpg.8d6c6dd90ade233ceca2331f5b2b2f02.jpg

 

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ahh yea so it's the good base of small mods(headwork, ex side, etc) that makes the cams look super impressive and give the mighty curve... then airflow from runner length/size that dictates peak power, but mess up the base and the curve can move around alot.

Wow that 20v is low! I have a friend with a 20v drift starlet (factory computer etc) and it goes really well, I really would have thought it was 110-120kw haha but guess his driving must be really good!

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Haven't done any real development on 20v.  but the ones Ive dyno'd have been far from impressive. especially through the mid range considering they have  vvt.   but again with the right bits should wake them up.   the green line is my stock ish 20v.  some minor tweaks to  head, aftermarket ecu and decat. otherwise stock.  factory on stock ecu i would expect them to be under 100kw. 

 

 

2114724611_zacvsbigportjunkervssjessevs20v.jpg.20a9a53b322d3f0fa713488f115b02ea.jpg

This one is a kick in the teeth to 20v (red).     Modified bigport head with stock little cams smaller  than 20v,  no vvt,  20v throttles, good header & exhaust. more power everywhere

1801907639_100oilvs20v.jpg.e9c8e0b44c2fab356f103a96a97739b0.jpg

 

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  • 7 months later...

Block itself has different sump bolt pattern to 16v, but just use 20v sump. external oil drain not drilled, but otherwise pretty much same.    pistons different, the valve cutouts will be in wrong place for 16v head. i dont know if will actually work, but would at lest be limited to little/factory cams.  rods same as late 4agze smallport. the 509gram ones.      so yeh swap pistons and same thing 

196631162_508763676927049_1406269904277756291_n.thumb.jpg.b93008706208155027603615b3d59446.jpg

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What lobe centers are the 20V cams in on ?  In the Yamaha bike versions the stock cams are on 100 inlet 110 exhaust.  That's measuring off the outer valves - the center inlet is 5 deg different.   It's pretty well known that they go better retimed to 104/106. Better spread and maybe a tad more top end - depending on the pipe.  Buit the biggest thing with the bike engines is getting the squish right, Stock is over 1mm - which simply doesn't work. Close it up to .035 - .039in and it wakes them up nicely.

The pointer to the problems with the 20V though is the Yamaha advance curves. First peak at 6500rpm 42 degrees.then a drop back to about 36 degrees.  2nd peak at about 8500 48degrees Then a drop to 30degrees at about 11500 - which is the rev limiter. The Prof from QUB who was working with Yamaha gave a talk to the Engine Recon institute some years back. He agreed that there were problems getting the mixture burning at certain rev periods. I suggested it was a turbulence problem caused by the center valve flow superimposed on the outer two.  He thought that was probably correct.

FWIW the race version 750 - the OW01 - tops out at 52 degrees advance. It's bigger bore than the other 20V engines.

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not sure sorry,  they have basic vvt  on intake. which advances the cam 30deg when on.  usually switching back off between 6-7000rpm.

They make best power with 28-30 degrees ign timing up top.  haven't come across any weird spots where they need more advance.  pretty much  like the same ign curve as 16v head

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On 26/02/2022 at 13:56, kpr said:

Block itself has different sump bolt pattern to 16v, but just use 20v sump. external oil drain not drilled, but otherwise pretty much same.    pistons different, the valve cutouts will be in wrong place for 16v head. i dont know if will actually work, but would at lest be limited to little/factory cams.  rods same as late 4agze smallport. the 509gram ones.      so yeh swap pistons and same thing 

196631162_508763676927049_1406269904277756291_n.thumb.jpg.b93008706208155027603615b3d59446.jpg

Cheers for the info man, might just grab the bit I need and trademe the rest!

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  • 3 weeks later...

What’s ya thoughts if twin 40 dellortos on a ae86 bluetop bigport motor?

 

never seen or heard of any dump figures compared to an injected motor.

 

 

 

ps I had a ae92 fxgt with redtop small port motor, lived on the limiter for 2 years/100,000kms before I sold it.

only ever killed a clutch plate(spring broke).

That was a great car

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I dunno how carbs work.   but end of the day its just a hole the air and fuel goes though.     If sized right  should be same same.  only real advantage carb has is fuel introduced further from valve so more cooling effect.   but yeh same can be done with efi

of course efi will run nicer.  higher the power will be even more in favor of efi.  as will need to run bigger carb/s  which will suck (or not suck enough to work)  at low rpm.

 

 

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18 hours ago, shizzl said:

What’s ya thoughts if twin 40 dellortos on a ae86 bluetop bigport motor?

 

never seen or heard of any dump figures compared to an injected motor.

 

 

 

ps I had a ae92 fxgt with redtop small port motor, lived on the limiter for 2 years/100,000kms before I sold it.

only ever killed a clutch plate(spring broke).

That was a great car

i have 45mm dellortos on my stock smallport seems to go well but never had on a dyno to no actual numbers

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