Intake runner diameter

[Duk]

Your not entirely correct. At a high enough power output 4 valve heads become inferior.

Is that above the Formula 1 level of engineering?

[wilbo666]

2 valve / cyl motorcycle engines are also coming back into fashion I hear?

Cheers
Wilbo

[ViPeR_NiPPleX]

24 valves per v8 race engine is cheaper vs 48, maybe that's the US of A drive? Can't beat surface area however imho. I'll take the 4 valves per cylinder anyday.

[oldcorollas]

i thought the argument was that if the engine spins slow enough, then 2 valve can be made to work as well as 4 valve... ie if you are spinning your race engine to 6000rpm or whatever..

ie, supposedly 2 valve can be made to work almost as well as 4 valve if engine is slow enough as the extra flow potential of the 4 valve is not used....

i am not totally convinced tho.. as it introduces a whole new set of compromises on port size

[Billzilla]

i thought the argument was that if the engine spins slow enough, then 2 valve can be made to work as well as 4 valve... ie if you are spinning your race engine to 6000rpm or whatever..

ie, supposedly 2 valve can be made to work almost as well as 4 valve if engine is slow enough as the extra flow potential of the 4 valve is not used....

i am not totally convinced tho.. as it introduces a whole new set of compromises on port size

Yes it's true. I found it hard to believe but on PF there was a good thread on it and now I'm a believer - however - the 2v engine has to have a pretty big cam and as mentioned above not be a revver and be big to just equal a good 4v engine.
The 4V is better at just about everything else.

[oldcorollas]

to paraphrase the thread (in a way )

If you have low targets, then an inefficient method when maxed out, can be almost as good as a more efficient method, which is not maxed out at the low target point...

ie, if you only want yout torque to peak at 4000 or 5000rpm on a large capacity motor, and are prepared to make the ports small enough to peak then, and restrict at higher rpm,
then a 2 valve head will only just fit the bill, whereas a larger ported 4 valve will make same torque at that point and still go higher...

(or said another way.. with your 1300 motor, a maxed out K engine is as good as a 4V suzuki motor, as long as you restrict the 4V motor.. or rev them both low enough so that the absolute valve curtain is not the limiting factor...??)

bill, did they reolve what would happen if you changed the 4V port size to peak at the lower engine speed?
ie, given same high port speed for both, is it better to have
1) a low lift, low overlap 4 valve head,
or
2) a high lift, long duration, long overlap 2 valve head? surely the overlap will have

the original thread was still comparing larger poted 4V heads, which would have lower velocity than the 2V...

then again... the 2V heads don7t seem to make as much torque per L as 4V in production engines, but is that due to cheap manufacturers? or limitations?

[jeffro ra28]

Yes, he's referring to 4 valve Heads that were made back some 30+ years ago in the good ol U S of A........ you know the same place where some still believe 2 valve Heads are somehow superior to 4 Valve Heads... lol.

The only reason intake runner diameters were larger on the Euro/Asian 4v vehicles 20 years ago then they are now is all to do with the port/valve angles as there is a max / optimal speed before the fuel/air mixture no longer remains uniform as it travels around a SSR. Ports now days are on the extreme end of being vertical (i.e. no SSR, no radius of any kind from the Injector location to the Valve seat) and this is why higher port speeds (ie. smaller runner diameters) are possible.

Davids article (linked above) clearly outlines the "downdraught angle" and its affect on portsize. So is he still reffering to 30 yo old 4 valve heads only? And arent we talking about a 7m here? How long ago was that engine designed? Its hardly modern!

[abently]

Anyone who has followed David Vizards ramblings knows that he was superseded by real Engineering back in the late 80's. Unfortunate in the sense that his passion couldn't keep him at the forefront in his field....

If you still believe that 2V Heads are still superior to 4V Heads, then it may pay to look at an LS1/2/3 Engine dyno plot and compare it to others of similar capacity but 4V. That should be definitive enough since the LS Engines have been engineered on a level playing field but retain just 2V per Cylinder.

I still challenge anyone to improve on any 4V Engine just by changing the intake runner diameter. 4V Engines came to the fore when Engineering started to understand the IC Engine and its parameters more mathematically. I feel sorry for anyone who thinks they're doing something factory didn't try.... yes they must have just picked that ID out of thin air and not tried any variations at all because the car only weighs 500Kg's so an extra 10% of power is overkill ofcourse...

I applaud the effort and enthusiasm, just wish you used all that energy to turn some ITB's for it instead.

[oldcorollas]

Anyone who has followed David Vizards ramblings knows that he was superseded by real Engineering back in the late 80's. Unfortunate in the sense that his passion couldn't keep him at the forefront in his field....

If you still believe that 2V Heads are still superior to 4V Heads, then it may pay to look at an LS1/2/3 Engine dyno plot and compare it to others of similar capacity but 4V. That should be definitive enough since the LS Engines have been engineered on a level playing field but retain just 2V per Cylinder.

I still challenge anyone to improve on any 4V Engine just by changing the intake runner diameter. 4V Engines come to the fore when Engineering started to understand the IC Engine and it parameters more mathematically. I feel sorry for anyone who thinks they're doing something factory didn't try.... yes they must have just picked that ID out of thin air and not tried any variations at all because the car only weighs 500Kg's so an extra 10% of power is overkill ofcourse...

I applaud the effort and enthusiasm, just wish you used all that energy to turn some ITB's for it instead.

have you seen the LS thread?
LS motors (almost all of them) onyl make 90Nm/L
similar sixed 4V motors are making 100-105Nm/L

i hardly think that is comparable.
4AG's were making more than 90Nm/L way back when
the playing field is not level. the LS engines are inferior compared to other similar size engines..

you're an idiot sometimes(?).
the port and runner size will be determined by the velocity you want AT THE RPM RANGE YOU CHOOSE...
the port and runner sizes are determined more by rpm range than by the number of valves...

except that you can get away with slightly smaller ports on 2V heads, as they are restricted by the valves at higher rpm... (ie, 90% of the flowing area)

thats like saying the bigport 4A makes more NA power in a near stock application than a small port...

[amichie]

The basis of my original enquiry into the port dimensions was not that I, nor anyone else here knows more about cylinder head design than the original designers (either at Toyota or Yamaha). It was just that their motives and design goals were different from mine.

It may be that large intake runner dimensions encourage exhaust gas recirculation (egr) at low - mid rpm with small throttle openings, in the same way that intake cam advance is used by toyota in their VVT systems to achieve the same thing. These are both basically emmisions reducing features that use the intake reversion.

The designers may also have wanted to flatten the torque curve throughout the rev range and simply tuned the inertia peak effects beyond the normal operating rpm range.

A have begun a bit of a survey of intake runner and port dimensions on modern 4v engines.

I will post it up when it starts to look useful. But it is clear that european designed engines use much smaller intake ports for a similar cylinder capacity.

[amichie]

Just another thought.

Has anyone tried using a deliberate mismatch from the inatke manifold to the head to reduce inversion? I know its common practice on exhaust ports but what about intake ports.

[abently]

Just another thought.

Has anyone tried using a deliberate mismatch from the inatke manifold to the head to reduce inversion? I know its common practice on exhaust ports but what about intake ports.

Common practice amongst the V8 guys dealing with the old Engines and class restrictions on what you can / can't use.

The best way to reduce inversion is in the Cylinder Head ports & valves themselves but if you are running extreme amounts of overlap, then everywhere possible becomes plausible.

Broad torque curve is influenced by the cam, have you considered just upgrading the cams ? Would be money well spent in the N/A sense of bang for buck mods.

[jeffro ra28]

Best way to reduce reversion is by using a cam that is correctly matched to your engine Or the use of VVT.

[amichie]

I have BC264 cams with adjustable cam gears.

Works well except when the ECU decides it needs to idle at 500rpm.

Getting off topic now but.

If I run lobe sep angles less than 110 degs I get crappy idle due to low vacuum. However it does have excellent midrange with tight lobe sep angles.

Most of the time I run it with 112 deg lobe sep angle and about 2 deg cam advance. Its a really good street grind but I'm sure there is more gains to be had in the midrange with some intake mods.

[abently]

Just looked at the BC264 specs, they are mild. Bit of a shame.

You should play around/document the actual opening and closing angles w.r.t TDC. Adjusting the lobe sep angle isn't a very accurate way of categorising the results...

If you can borrow a spare Intake manifold & Head, have it flow benched along with a plasticine/alloy trumpet and see if there's much to be had.