Head Port Size, Velocity Vs Horsepower

[Fabiotorta]

Even more curious, does anyone have some pics of the neo head ports?? Or throath size?? I can just find the n/ a.

Anyway 600kw if the intake is a restriction there should be massive problems of boost and temperature...and definitely not that power????!!!

But are the ports really smaller than rb II ser.???

[Fabiotorta]

Even more curious, does anyone have some pics of the neo head ports?? Or throath size?? I can just find the n/ a.

Anyway 600kw if the intake is a restriction there should be massive problems of boost and temperature...and definitely not that power????!!!

But are the ports really smaller than rb II ser.???

[GTSBoy]

If you want small ports, go look at 2JZGTE!

[discopotato03]

GTSBoy I never got the full story on what the exact head differences are between R33 and Neo turbo heads . I know the Turbo Neo chambers have a smaller capacity than the R33 RB25 ones but was never sure if they were shallower or the valve angles different . Also not sure how much smaller their inlet ports are .

I think I read that the Neo Ts torque peak is significantly lower than the 33 DETs but as you said different cam profiles are a significant part of a system rather than a major change in isolation .

If I was ever to rebuild a 33 spec 25DET it would use Neo spec pistons rods and head .

Neos were the last RB25T revision roughly five years after R33 25DETs , factory engineering is difficult to beat particularly when the trend was towards more power/lower torque peak and lower emissions - read lean mixtures with efficient combustion (reasonable timing numbers) .

A production road car is mainly about was sort of torque and drivability you get at part throttle loads . Efficiencies here are generally what emissions and consumption is all about because that's where a road car spends most of its time . It all changes at wide open throttle and full power at revs can be compromised to a degree . Very likely why the GTt had a slightly larger SMIC and turbine housing .

I personally don't think porting (modifying) is that important on an RB25 head unless you expect really high numbers and then a 26 is probably a better (less compromised) basis to play with . They don't pretend to make great part throttle lowish rev torque and the ITBs etc are aimed at better cylinder filling in the upper half of the rev range . AFAIK the ports/chambers in a 26 head aren't majorly different to R33 RB25 ones , Nissan just changed the side water jacketing and manifold bolt patterns to stop you cross dressing manifolds between 26s and 25s .

On paper the Neos 206kw isn't far short of the 26s 209 and a Neo with 26 manifolds and turbos may have made the by 1998 ageing RB26 look a bit pedestrian overall .

Hate to say it but all RBs are dinosaurs by todays standards .

A .

[Fabiotorta]

From what it looks like to me the neo engine has got a great low end torque at slower revs that is more than the non neo even at 4800 revs peak torque non neo.

Less fuel more power but since a neo is not easy to find i wanted to see if is possible get same result modifing non neo head.

The low end torque can be gained from better combustion like making more power at the same boost a bigger turbine housing doesn t help low end.

Anyway no one that knows what really looks like neo ports???

From the combustion chamber pics looks like the downdraft angle of the valves is reduced but what i am interested is the size!!!

I would be glad to have a non neo with tjat low end torque than power can be built with boost...

Anyone knows if swapping to a bigger turbo or bolts on that low end torque ability is lost??

[discopotato03]

I think the same era Stags used the same head , not sure if OE cams were the same though . Apparently Stag Neo engines are harder to sell because most don't want the 4WD block and sump .

Without more work than its worth you won't recreate a turbo Neo from an R33 casting . The Neo is a unique system of pistons chambers cams and valve train , and a different inlet manifold . A sum of its parts so unless you have the complete system you can't guarantee the same results . Probably easier to buy a good complete Neo (minus hot side) or equivalent Stag engine if you don't want to fit the correct pistons in your own block .

A .

[GTSBoy]

Anyway no one that knows what really looks like neo ports???

Dude. They're nearly 20 years old! Pictures are all over the internet.

[AngryRB]

The intake mani is definitely smaller in port size, the head ports dont appear to be visually different in port size between the heads to me, could be wrong.

Intake gasket matches R33 well but neo mani is smaller

Same Gasket matches neo head well same as R33

and again closer look at the difference of gasket to neo intake mani, can see alot more meat around injector area

Edited August 24, 2015 by AngryRB

[Fabiotorta]

Thanks a lot for your pics finally i know what they looks like and from what i see the runners are smaller on the intake mani and sligly inside the head but the choke point looks the same as the downdraft angle...actually the ports looks exactly the same as the non neo??? Now the question come,someone felt any differences going with aftermarket intake manifold?? Low end torque loss???

Thanks again for the pics, if you re gonna remove the valves could i ask some more pics to see the port better??

Cheers!!!

[GTSBoy]

Now the question come,someone felt any differences going with aftermarket intake manifold?? Low end torque loss???

Usually, yes. The shorter the runners on the aftermarket manifold, usually the bigger the reduction in low end (hopefully accompanied by extra at the top, but not always!)

[Fabiotorta]

So it is possible that a 45 mm intake, neo like, works well with short ports keeping speed and flow at a good level.

Probably an intake with 45 mm runners greddy style would keep low end torque...and probably is what i m gonna do!!!

I don t want to loose low end torque just to increase top end...i reckon on a turbocharged you can achieve both

[GTSBoy]

Greddy plenums generally definitely DO cost low end torque. They are the definition of the "short runner" manifolds.

[KiwiRS4T]

What you need is a supercharger.

[Ben C34]

Whilst it's admirable what yu are trying to do, "don't reinvent the wheel" comes to mind.

[Fabiotorta]

???? Don t know what that is but i love study and improve engines and i don t really want to spend all that money on a greddy plenum to loose low end torque...probably it flows a lot more and improve ram effect at high revs...probably it flows so much that on a mild tuned engine it just slow down air too much giving no improvement at all...it s like the 80 or 90 mm throttle body????? Isn t it big for nothing??? I mean if my engine at 500 hp needs 50 lbs/min why install a plenum that can flow let s say 60-70??? I would never use the potential of that component, maybe and i repeat maybe it is better a 45mm runner as long as i can with air stack to use that cross sectional area the best i can and maybe i would be able to get some ram effect as well.

I learned this by working on rally cars...match everything for what u really need by calculation, that makes a good engine....

[scotty nm35]

???? Don t know what that is but i love study and improve engines and i don t really want to spend all that money on a greddy plenum to loose low end torque...probably it flows a lot more and improve ram effect at high revs...probably it flows so much that on a mild tuned engine it just slow down air too much giving no improvement at all...it s like the 80 or 90 mm throttle body????? Isn t it big for nothing??? I mean if my engine at 500 hp needs 50 lbs/min why install a plenum that can flow let s say 60-70??? I would never use the potential of that component, maybe and i repeat maybe it is better a 45mm runner as long as i can with air stack to use that cross sectional area the best i can and maybe i would be able to get some ram effect as well.

I learned this by working on rally cars...match everything for what u really need by calculation, that makes a good engine....

Totally agree, that's why I like using the stock components. Long runners to help with midrange, then cram more boost in to bring the top end to where you want it.

Mucking around with head ports and runner sizing, even if calculating it with flow analysis programs, you would either need access to a flow bench or have temp probes in each exhaust runner and hope any flow differences can be adjusted out. Much harder to match 6 ports than 4.

[AngryRB]

Ford must of put some thought into runner lengths cause they have a variable runner length setup on the falcon, there's a row of butterfly's that when open make the runners longer and shorter when closed, all operated by a vacuum line,

[Ben C34]

Ford must of put some thought into runner lengths cause they have a variable runner length setup on the falcon, there's a row of butterfly's that when open make the runners longer and shorter when closed, all operated by a vacuum line,

Variable runners are quite common.

Adapt that setup to fit op.

[scotty nm35]

Those NA variable runners would love 30 pounds and 3 times the air speed. lol

[GTSBoy]

Ford must of put some thought into runner lengths cause they have a variable runner length setup on the falcon, there's a row of butterfly's that when open make the runners longer and shorter when closed, all operated by a vacuum line,

Variable runners are quite common.

Adapt that setup to fit op.

Those NA variable runners would love 30 pounds and 3 times the air speed. lol

Um......Red top RB20 anyone?