Roman's 4GR V6 Carina discussion thread

[Roman]

Things like bigport 4AGE and the early 3S engines had the huge port area, but then the TVIS system a little bit upstream that shuts off a runner to counteract it.
I guess if you looked at the "pinch point" when one of the runners is shut, it would go way to the other end of the graph. 
The 4GR originally has this similar system as well, to make the DI stuff work at low rpm.
Also I think the 2.5 and 3 litre GR engines (3GR and 4GR) share the same intake manifold, so the 3 litre engine has the same entry shape but less taper down to the bigger valves.
So again, probably a shit way to design a 2.5 litre engine but just works out well for manufacturing reasons.

It seems that in the era of fixed cam timing, there was a trend back towards smaller ports. 
But then as VVT emerged, it's back to having little downside to having a larger port again.
If you look at a 2ZZ the ports are absolutely huge, because I think the cam timing magic nulifies the major downsides of a bigger port.

I guess with a direct injection engine where there's no need to consider "wet flow" at all, there's potentially different constraints on port size/shape/etc.
Either way, hopefully not toooooooo long until I can quit the speculation, and move on to the excuse making stage. 
Been too long off the road already.
Hoping to have garage weather tight by this coming weekend but have also had some miserable weather lately.

[BiTurbo228]

14 hours ago, Roman said:

Things like bigport 4AGE and the early 3S engines had the huge port area, but then the TVIS system a little bit upstream that shuts off a runner to counteract it.

Yeah I still need to go through and caveat everything where I can find out there's odd designs that skew the data. Things like runner taper and funky intake gubbins or VVT could well change the design parameters. I'm on light duties at the moment as I've f'd my back so it's not like I have anything better to do...

I need to trawl through for some earlier Japanese 4v engines. I can't quite work out if big ports is just a Japanese design philosophy of the time, or if it's influenced by the Japanese cars being generally later than the European 4v engines (more 90s than 80s), and thus making more use of funky intake trickery. It certainly seems like comparatively small ports and valves is an Italian design philosophy in the late 80s/early 90s (excluding Alfa), so it could well be a cultural thing.

14 hours ago, Roman said:

I guess if you looked at the "pinch point" when one of the runners is shut, it would go way to the other end of the graph. 

If it does effectively fully close off one of the ports then yep, it's 1.8mm2/cc which is about the same as the S14 right at the bottom of the graph.

14 hours ago, Roman said:

Also I think the 2.5 and 3 litre GR engines (3GR and 4GR) share the same intake manifold, so the 3 litre engine has the same entry shape but less taper down to the bigger valves.
So again, probably a shit way to design a 2.5 litre engine but just works out well for manufacturing reasons.

Ah, I did wonder if the ports were more of a manufacturing ease thing. You get the same with the Saab 16v B engines, which all have the same valves and practically all have the same ports, regardless of displacement or aspiration.

They'd still be pretty huge for a 3.0l engine as well (4.3mm2/cc), so right up with your 20v Volvo whiteblocks. Could also be that eyeballing a CAD model of a picture of a headgasket isn't the most accurate way to measure the area of a port...

14 hours ago, Roman said:

Either way, hopefully not toooooooo long until I can quit the speculation, and move on to the excuse making stage. 

I expect the excuses stage will still require a fair dose of speculation  

Edit: Corrected an error with the RB20 which is now right at the tip top end of the port graph (3.9mm2/cc). Added in a few more older Japanese 4v engines to try and get a bit more representative. SR20DE, FJ20E and FJ20ET are 2.6mm2/cc which is middling, FJ24/RB25 NA/CA16DE have huge ports as well (3.0, 3.6 and 4.0 respectively). The only Japanese 4v engine in the bottom third of the graph (so far) is the little CG13 from a K11 Micra at 2.0mm2/cc, and that seems to be limited by a dinky 71mm bore.

[Roman]

Here's my take on why we've seen wildly different sizes on things like exhausts, ports, valve size being "ideal" as tech has changed and we've progressed through the timeline.

Carb era 
In the 60s or 70s when carburetors were common. 
You've got a situation where the carb is mounted fairly far from the head, and suspending the fuel as it's transported to the combustion chamber is an absolutely critical aspect of the engine performance. 
So you need small port sizes, small runner sizes in order to keep airspeed up. Even at low rpm.  
Then your fuel pressure is really low. If there is only 3-4psi of fuel pressure, then having any sort of pressure wave in the intake manifold can hugely affect the fuel delivery.
If at some rpm point there is a harmonic wave that adds or removes 2psi of pressure, then you've just lost or gained 50% of your fuel pressure differential. 
So as a general rule ports were small, valves were small, runners were small, and exhaust manifolds tried to avoid causing any massive peaks or troughs in the intake pressure. 
Compression ratios were low, in order to avoid issues with knock as there was no computer control over ignition.
So very little cam duration, and tuned lengths somewhat avoided. Cast exhaust manifolds quite prominent.
2 valve heads common. Possibly because a 4 or 5 valve head, it was impossible to realize the benefits of the extra valve area when airspeed needed to be high all of the time.

Early EFI era 
In say the 80s, EFI changed the game a bit by having a much higher fuel pressure and injectors mounted right by the head.
So now you didnt need super tiny intake runners to suspend the fuel with high airspeed. 
The fuel is delivered straight down by the valves ready to go.
So now runners an get bigger, ports can get bigger, valves can get bigger. 
You can realize the benefits of a 4 valve head, because you can have larger runners to match the higher valve area.
The higher base fuel pressure also means the motor is considerably less sensitive to differential fuel pressure changes from positive or negative tuned waves from intake or exhaust.
Having a tuned length exhaust manifold could be beneficial where it helps pull gas out, with comparatively little detriment when it's out of phase. As it's not disrupting the differential fuel pressure like with a carb.
So it's not going to cause stand off. 
So now you could have a bit more cam overlap / duration without any downside. 
Usually had fixed valve timing, basic ECU & injection, and still a reasonably low compression ratios on NA motors. 
When you have a motor with a static compression ratio of say... 9:1 or 9.5:1 theres a still room in the head for residual exhaust gas to reside in the cylinder once the exhaust stroke is finished.
So these motors were really sensitive to the benefits of having good extractors, and EFI made them insensitive to the downsides.
So even really dunga motors like a 4AFE had a really nice 4-2-1 extractor setup. While the carb version of the same motor made in the same year, just has a cast manifold instead.
EFI was the change at this point that allowed the removal of a lot of constraints on design for things like tuned exhaust. That had a root cause of fuel delivery issues.

The Medium EFI era
Then we move to about the 90s. Still usually fixed cam timing. But it seems like manufacturers were trying to maximize the powerband a bit more, and ECUs can deal with knock etc a little better. 
So we still see the decent 4-2-1 exhaust manifolds on everything, and more effort to try beef the powerband everywhere and improve economy.
So there's a range of different variable intake geometry coming out on motors. 
Things like varaible plenum volume, variable runner designs, and so on all gave decent benefits.
Compression ratios generally getting a bit higher into the 10s.
Motors were making more power but also getting better fuel consumption without knock issues.
Port sizes, tuned lengths etc could now be based around what the variable geometry systems, with fewer downsides than before.
So everything could get a bit bigger. Power levels go up, as yet more of the design constraints of low rpm drivability were loosened.

VVT Era 
Late 90s / early 2000s when variable cam phasers came in, it tipped the existing rule book on it's head again.
The cam phasers largely made any variable inlet geometry like TVIS obsolete. As it's diminishing gains having more than one variable system in place. 
Cam phasers became the simplest and cheapest way to broaden a powerband, so the rest of the stuff got the boot. 
It also seemed to allow engines to have port sizes and valve sizes to suit their peak power requirements,  with even less detriment to mid range or low rpm.
A motor could now have heaps of overlap when it's beneficial, and not when it's not.
Cam duration and lift became more aggressive, ports and valves could get bigger with no downsides.
So looking at a beams 3SGE engine which has VVTI,  for example. It has absolutely monstrous ports compared to earlier fixed timing heads.

Crappy exhaust manifold Era
Move to the early/mid 2000s and we're in an era where ECUs control and knock strategies etc are so effective, that compression ratios can go even higher. 
So ordinary to see 11:1 or more, even on economy engines.
When the compression ratio gets higher, and VVT is present. The motor is less sensitive to exhaust design (citation needed, just my observation)
So the motors can be made simpler and cheaper by putting a garbage manifold on, without any downside. 
So we're kinda back to the carb era of exhaust stuff, where we're not relying on a tuned length system anymore.
Despite some absolutely disgusting exhausts, motors of this era are making better overall power/torque/economy/etc than earlier designs that were heavily reliant on a tuned 4-2-1 system.

Direct Injection Era
Then Direct Injection comes along, which was another technology that just tipped everything on it's head like VVT or EFI did.
D.I caused a renaissance for the long abandoned variable intake geometry designs.
As to get stratified charge working at low rpm, there needs to be lots of swirl in the chamber.
Which you cant do with a 4 valve head and the huge valve area.
Now the 80s style TVIS block off plates are back in vogue.
Total intake port area can be huge, because it gets cut back in half by the TVIS type systems when needed.


Based on the above I dont think there's any hard and fast rules around what works, because everythings works or does not work within the constraints of the surrounding tech level of the engine.
As a motor can be highly dependent on a tuned exhaust manifold, or, not. (carb era engines, or late high comp EFI engines)
Or highly dependent on airspeed, or not (carb era engines, or DI engines, but not anything else in between)
 

[BiTurbo228]

Yeah I'd definitely buy that as a development trajectory, with the differing engines in the charts at different stages along it. You can certainly plot that trajectory through Japanese engines from things like the 20R with its teeny tiny ports, through the 5M with more generous ports to the 7M with massive ones. Need to get some good data on European engines of the 'Medium EFI and VVT eras' as I've only really got a handful of them to check against, and none are particularly up at the pointy end of port sizes (aside from the Volvo 20v anomaly and the Alfa 3.0l 24v). American and Ozzy engines tend to be poorly attested in the FIA record though, so there's limits there as well.

The exhaust scavenging idea would make a lot of sense as to why I see totally junk manifolds on BMW M inline 6s where a good 6-3-1 on a dodgy old Triumph OHV is utterly transformative. Always seemed like power and torque left on the table to me, but perhaps not.

Absolutely agreed that there aren't any hard and fast rules, and trying to apply averaged rules of thumb to engines is a bit of a fools game if you're not experienced enough to know what's what. Hence why I was trying to get a bit of a database going. That way you could look at your head (in my case a Rover 2600 that precisely one person has ever done anything with), look through the database for a couple of other engines with comparable design parameters, and maybe get a bit of a steer about what to do. Less 'become an expert tuner overnight through data crunching', more of 'try to get your first stab in the dark roughly in the right direction with an unknown head'.

[440bbm]

You also need to consider cost of manufacturing which doesn't seem to be a factor in your thought process.  While you have done extremely well to consider the mechanics of it you do need to consider the cost of the development and manufacturing. The cost increase to make 4v motors, even the change /addition to hemispherical heads were a huge jump in performance yet not every manufacturer had one. the design wasn't the hard part and was no major reason why they couldn't.  

then you had the ability and development of alloy heads, casting possibilites and how to manufacture these repeatable. How much easier casting methodologies and more intricate shapes..  It's not just down to carbs or not.  It was the time, where else can they save the money from in the cost of the car to the increase the cost of development and engine costs. there is so much more at play here. 

Its a never ending loop. the more you think about of cause/effect and the times back then the deeper the hole gets. 

when you start getting to the pre vvt era where computer design was so much stronger, understanding the technology and more people had a better understanding of materials, and how to manufacture things in specific ways and costs then more was achieveable. really, the early 2000's were where things really kicked off in terms of design/engineering and manufacturing.

 

its been pretty impressive when you see the course things have taken and over, such a short time frame. 

 

 

[shrike]

Going back to 3d printed parts, ie your merge collectors

Not sure if this has been posted before or if anyone is already following, but this guy is doing some fun 3d printed bits

https://youtube.com/@couchbuilt?si=MZG8Y9Jyiat2d8Fk

[Roman]

5 hours ago, 440bbm said:

then you had the ability and development of alloy heads, casting possibilites and how to manufacture these repeatable. How much easier casting methodologies and more intricate shapes..  It's not just down to carbs or not.  It was the time, where else can they save the money from in the cost of the car to the increase the cost of development and engine costs. there is so much more at play here. 

Its a never ending loop. the more you think about of cause/effect and the times back then the deeper the hole gets. 

Ahhh yeah I agree 100% ! 
The things that need to be taken into consideration at an OEM level are insane. And all of the constraints applied, and then trying to make it a sellable product with a warranty that lasts 100s of thousands of kilometers.
We're lucky as DIY tinkerers to have the freedom to do whatever the hell we want.

I guess the point I was trying to make, is that "old info" on the internet has a loooooonnnnggggggg lifespan.
And that generalizations about port size and so on, are only relevant metrics compared to other similar engines. 
The graphs that @BiTurbo228 posted are really interesting because they show what a huge variation there is on what some people might consider to be a hard and fast rule.

For example, some testing that David Vizard might have done in the 70s or 80s, about optimizing a 2 valve carb motor.
Studied port sizes, ratios, runner lengths, and so on.
This information is absolutely 100% valid, in that context. 
So for example, for that motor having good air speed is absolutely critical. Or you're getting fuel puddling in the engine.

But then on some EFI engines some dyno testing shows that runner diameter just isnt a critical factor anymore.
Going too big has virtually no downsides, and going too small absolutely kills it. (or whatever) 
Yet some people will spend $$$$$ on an EFI motor and choke the hell out of it with tiny throttles or whatever.
Because they've applied irrelevant generalizations to their particular engine.

I've seen enough formulas, theories, etc absolutely fall on their face when it comes to emperical testing.
That apart from following some very loose rules about how things should be (no super sharp edges on inlet runners) I think it all just comes down to testing testing testing.
Some people pick a formula, decide that's the best possible thing, then test it and just accept the results good or bad. Rather than testing more iterations to validate their concepts.
So thats why I'm itching to get to that point, this current part sucks and I apologize to everyone who's been reading my drivel this long without seeing any interesting results for better or worse yet.
Hopefully though I'm close to the finish start line 

[fuzzy-hair-man]

12 hours ago, BiTurbo228 said:

The only Japanese 4v engine in the bottom third of the graph (so far) is the little CG13 from a K11 Micra at 2.0mm2/cc, and that seems to be limited by a dinky 71mm bore.

The CG13DE shares it's head with the CG10DE so it may have been compromised on that front, compared to the Suzuki G13 the head is much smaller (makes it easier to fit in a mini).

The CG wasn't designed for power, it was only ever a shopping cart meant to be easy to drive, so awful inlet and exhaust manifolds, and very heavy flywheel. My cams are 274 duration so trying to have as long as possible to breathe through a small port?

A comparison to a later CR10DE, CR12DE, CR14DE may tell a bit of what Nissan found they could do with VVTI, bore, stroke and compression ratio stayed much the same (9.5 vrs 9.8 - 10)

[Truenotch]

@BiTurbo228 that graph is so cool. 

 

Can you add a manual dual VVTi 3SGE Beams to the graph? Happy to get measurements if you need them. 

[Roman]

I cant find a beams motor comparison @Truenotch, you able to snap a pic of intake port for comparison? 
As it's a really interesting before/after of a VVT motor.
Early 3SGTE port was wide to accomodate TVIS then absolutely pinched up like crazy. 
Disgusting. haha.

[shrike]

3 minutes ago, Roman said:

I cant find a beams motor comparison @Truenotch, you able to snap a pic of intake port for comparison? 
As it's a really interesting before/after of a VVT motor.
Early 3SGTE port was wide to accomodate TVIS then absolutely pinched up like crazy. 
Disgusting. haha.

What about stepped exhausts

 

[Roman]

It's quite common to see a step between the head and the flange, as there's no downside to it being slightly oversized. 
Acts to reduce reversion a bit. 
But unlikely to be worth the effort of the extra welding etc steps halfway down the pipes for a manufacturer.

 

[GARDRB]

Paging @kpr can we have a VVTi big port 4ag next to verify @Roman’s claims that port size doesn’t matter anymore once you introduce vvti

[kpr]

Bigport 4age is kinda fake news like romans  3s example.     The port entry is bigger,   but goes down to a smaller size at the port divider than smallport 4age.     So really the smallport  is the bigport head,
Smallport (the real bigport) head  makes more top end than a bigport and less off the bottom.     but a lot of  it is is also in the inlet manifold.

My turd engine was bigport vvti  and made more midrange than any other na 4age ive seen making the same peak numbers,  but invalid because above.    If it were a smallport head it would do the same because vvti is the cheat code.  but still doesn't cover up all the sins of a bad setup.   if you were to add lift (2zz / k2*) along with that vvti  you cover up more sins again.

From my testing the port entry is kinda blah, doesn't matter long as its not too small.   But  if its way oversized like one of the tvis engines.  making a manifold that suits the entry size is also not the move, especially  if you are going to end up with a reverse taper.       further down the port towards the valves is where its important

 

 

 

 

 

 

 

 

 

 

 

[Truenotch]

6 hours ago, Roman said:

I cant find a beams motor comparison @Truenotch, you able to snap a pic of intake port for comparison? 
As it's a really interesting before/after of a VVT motor.
Early 3SGTE port was wide to accomodate TVIS then absolutely pinched up like crazy. 
Disgusting. haha.

Here you go:

[Dudley]

I’ve heard the 5k head has a better short turn radius in the port then any 4age head except maybe the famous 12,300rpm formula Atlantic head in the orange cars, what are your thoughts on this @kpr?

[BiTurbo228]

@Roman You wait until you get into valve-to-port sizing. It's a more reliable measure on 2v engines, but those vary wildly in approach. Seems to be a fair few close to the 'ideal' ratio, and another big chunk going down a 'small port, massive valve' route, and a handful with monster ports for a tiny valve (like port openings bigger than the valve diameter). Some of the Homologation docs have some pretty detailed info on cam specs as well, but that would be a total bear to transcribe. I was wondering if some of the 'huge valve compared to port' engines were making up for mild cam specs by oversizing the valve. I suspect this is the case with my Rover 2600 engines. Super-needly cams with very little low-lift, but big valve compared to port so that small low lift translates to an adequate curtain area increase.

Really what you'd want to do is plot port geometry (including minimum area) and valve size against valve lift, cylinder volume and BMEP...controlling for all of the extraneous variables like fuelling, ignition, weird intakes, cultural trends and anything else you can think of. But at that point you're getting into producing your own engine model, and I'm rather hoping my back gets better before I get that bored  also, would probably take less time and effort to make the money to build 3 different engines of the one you want and test them...

Iterative empirical testing of the actual engine you're going to use is really the only sure-fire way. If you're lucky you've got someone like Vizard or @kpr who's done it for you and published the results. If not, that's where I was trying to get some kind of steer with the graphs so at least you can start with a semi-informed hunch (when added to all the empirical data of other engines that may or may not be applicable).

@Truenotch Thanks! And yeah sure. I've added in the earlier 3S-GE from an ST165 and it's up there with the big port, big valves Japanese crew (4.06mm2/cc ports, 3.53mm2/cc valves). Doesn't appear to have data on the later engines, so if you've got some calipers and a spare head that'd be dead useful!

As both @kpr and @Roman mention the FIA dimensions for port sizes can be misleading. I suspect what actually matters is the size of each valve's individual port past the split, but the FIA papers only state the dimensions at the cylinderhead face. Some engines are nice and have individual ports for each valve so you can get a better steer. I wonder how many early-ish 4v engines with huge ports are actually much smaller when you account for the actual port size.

I've got a fair bit of googling ahead of me I suspect to try and find that info out for as many engines as I can. Even if I can't find someone who's actually measured it, I could fudge something to get closer by taking the outer radius of a flattened oval port as indicative of the ports after the merger. Not even close to perfect, but probably closer.

@fuzzy-hair-man Useful to know! There's a fair few engines like that, that are obviously optimised for smaller displacements and have compromises when you slap them on bigger engines. We seem to think the Maserati 24v head is like that. It seems to be midrange when you put it on a 2.0l engine...but they also fitted the exact same head to a 2.8l.

Oh, and as a general comment I've been going through and cleaning up some of the data a bit. Not many big errors like the RB20, but getting a more refined area from the specified dimensions. Probably a little premature making graphs from it, but I was over-excited 

[BiTurbo228]

Right, double-checked all the data for accuracy, plus added in as many more as I can be bothered with on the FIA site. Up to 116 multivalve engines which is a respectable(ish) number. Only done the valve size chart so far, because if you want to know what true MS Excel pain feels like you're free to try getting all the data labels legible on a graph like this:

Some interesting things that struck me, mainly at the lower end of the chart. I know Saab B204s are capable of well over 200hp/l without changing the valves (1hp/cc!), despite the fact that they look woefully undersized (especially on the 2.3l). Maserati valves do look very small like we expected, but maybe that's not so much of an impediment if you can just ram boost into them. Also, TU5J4s are also capable of well over 100hp/l (as is the FJ24 240RS), again despite what look like relatively small valves.

I suppose we could conclude that anything that's not at the complete extremes should work well enough, and even extremely small valves are secondary to other concerns in boosted engines (possibly provided the heads flow well despite the valves). Very few, if any, of these engines are 'poor performing'. I haven't done a 2v chart yet, so it could well be that '99% of multivalve engines have enough valve area to make power' might be a better conclusion (though the Maseratis and Saabs are getting there at bigger displacements).

Oh, and to keep this on topic for a 4GR. Still looks like you won't be wanting for valve area for revs.

Ports next. Wish me luck...

[BiTurbo228]

...and port graph.

Discovered a few more caveats. I know for certain that the ST205 and Duratec have been measured on a diagonal. Most of them are nice and give you a true cross-section, but some don't and others are ambiguous (i.e. just give you a shape with no accompanying port diagram to indicate where it's taken). Others specify a port measurement a certain distance down the port (ST185 compared to ST165 is an example, as is the Delta Integrale, Maserati 24v and the Dolly Sprint).

I suppose take this graph with a real pinch of salt as the data is much more suspect than the valve graph at the moment.

[Truenotch]

10 hours ago, BiTurbo228 said:

@Truenotch Thanks! And yeah sure. I've added in the earlier 3S-GE from an ST165 and it's up there with the big port, big valves Japanese crew (4.06mm2/cc ports, 3.53mm2/cc valves). Doesn't appear to have data on the later engines, so if you've got some calipers and a spare head that'd be dead useful!

 

I can go one better and get a full 3D scan of the ports (we're scanning it soon to play with inlet manifold designs). We'll see how deep the Peel can scan....