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Standard RB26 head capabilities.

khezz

By khezz,
in Engines & Forced Induction

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khezz Rising Star

khezz

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This is purely for personal curiosity. 

We see these questions all the time. What sort of power can standard gear withstand. Rods, pistons, block, turbos, headgasket, fuel lines, injectors, gearbox etc etc etc. What about the head. 

There are lots of flow charts for the RB26 head but what are the real world results. Because most people will not do a 5 axis cnc port and polish or go for oversized valves, shomless buckets. 

When I was getting my headword done, the cost was over $10k. Most people will go for drop in camshafts, springs, maybe guides and retainers. Possibly a brush through the ports to remove some build-up thats collected over the years/decades.

So what's the most power that you know of that has been extracted through a "standard" head? No porting, no material removed of any kind. Just a change in lift and duration of valves. 

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GTSBoy Grand Master

GTSBoy

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2 hours ago, khezz said:

So what's the most power that you know of that has been extracted through a "standard" head? No porting, no material removed of any kind. Just a change in lift and duration of valves.

To be fair, this is a bit of a nonsense because if you're changing cams and therefore able to consider valve springs, then you can add enough spring to overcome any float issues that might be caused by high boost levels and you can run as much boost as the rest of the engine can handle. So, if you have tough enough rods, pistons and oiling, ability to run to very high revs (from the cams and springs) and sufficient fuel quality to handle the boost, you can just keep cramming more boost in and making more power.

If it were an NA engine then the question might be more meaningful. But the native flow capability of the head is not really the limiting factor until you have gone all the way out into rocket science territory with other parts of the engine.

khezz Rising Star

khezz

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7 minutes ago, GTSBoy said:

To be fair, this is a bit of a nonsense because if you're changing cams and therefore able to consider valve springs, then you can add enough spring to overcome any float issues that might be caused by high boost levels and you can run as much boost as the rest of the engine can handle. So, if you have tough enough rods, pistons and oiling, ability to run to very high revs (from the cams and springs) and sufficient fuel quality to handle the boost, you can just keep cramming more boost in and making more power.

If it were an NA engine then the question might be more meaningful. But the native flow capability of the head is not really the limiting factor until you have gone all the way out into rocket science territory with other parts of the engine.

There will be a limit. It would be easy enough to work out just by max air flow through ports but that's the absolute best case scenario which never happens in real world. 

I have always thought that standard intake manifold is no good over 700hp. In one of the latest motive Cootamundra videos there is an R32 running a standard manifold with well over 1000hp. 

It will be good to know what people have managed to do.

GTSBoy Grand Master

GTSBoy

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1 minute ago, khezz said:

I have always thought that standard intake manifold is no good over 700hp.

What was "true" for Jap tuners who couldn't deal with the ITBs in the 90s was never really true at all.

1 minute ago, khezz said:

It would be easy enough to work out just by max air flow through ports

And what is that number? What boost are you chucking at the head? Air flow keeps going up with more boost. The limits turn up elsewhere (mechanical limits in the bottom end, detonation limits from the fuel, etc etc).

khezz Rising Star

khezz

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1 hour ago, hypergear said:

Fully stock motor. I'm getting 425awkws at 26psi at moment on E85 fuel with a GTX35 size turbo. Probably around 460ish kw in rear wheel.  

Nice. So no cams?

What's it drive like?

Do you have any dyno graphs?

khezz Rising Star

khezz

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Posted (edited)
4 hours ago, GTSBoy said:

What was "true" for Jap tuners who couldn't deal with the ITBs in the 90s was never really true at all.

And what is that number? What boost are you chucking at the head? Air flow keeps going up with more boost. The limits turn up elsewhere (mechanical limits in the bottom end, detonation limits from the fuel, etc etc).

Well you would take the diameter of the inlet valve minus the area of the valve stem. There would be an absolute maximum volume that can pass through that area in CFM. Times that by 12 and then use that number to work out what is the maximum number in hp that that flow can provide on e85 or 98ron. I don't care about either number. If diameter didn't matter, why do people go for bigger turbos, injectors, exhaust. Everything has its limits. I just want to know what people have actually achieved. Like Andrew from Motive and Hypergear above.

Edited by khezz
hypergear Grand Master

hypergear

Posted
Posted

power.jpg

Stock engine with head studs. Coming from Rb25det Neo motor, this is abit laggy for how I like it to be. Working on a different turbo direct at moment for same power and better response. 
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khezz Rising Star

khezz

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1 hour ago, hypergear said:

power.jpg

Stock engine with head studs. Coming from Rb25det Neo motor, this is abit laggy for how I like it to be. Working on a different turbo direct at moment for same power and better response. 

Nice. That's some kick after 4000rpm. My lowmounts did thsame but with 200hp less at top. Are you going to keep it stock and see where you end up or do you have further build plans?

GTSBoy Grand Master

GTSBoy

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2 hours ago, khezz said:

There would be an absolute maximum volume that can pass through that area in CFM.

No. It is not that simple. What pressure difference between the plenum and the combustion chamber are you using to drive that flow? 100 kPa? 200 kPa? 300 kPa? 400 kPa? 500 kPa? There are people running that sort of boost on spark ignition engines. Each one of those larger numbers will mean more flow through the valve. It is not as simple as you seem to think it is. It's not even that simple in an NA engine where most people assume that you can only have almost exactly 100k kPa pressure drop across the valve, because there are many things you can do to get much better volumetric efficiency at certain points in the rev range. It is certainly even possible to get >100% VE on a stock head with the right cams and some intake tuning.

Boost is the great ruiner of your theory. Not enough flow? Just add more boost.

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hypergear Grand Master

hypergear

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1 hour ago, khezz said:

Nice. That's some kick after 4000rpm. My lowmounts did thsame but with 200hp less at top. Are you going to keep it stock and see where you end up or do you have further build plans?

I think Its already close to its maximum capacity at this point. I won't be able to run much boost into stock bottom end. So planning to upsize Camshafts that should increase the power to boost ratio. 

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khezz Rising Star

khezz

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2 hours ago, hattori hanzo said:

620kw/146mph on standard head

 

Machined for 272 cams, but didnt touch the ports etc

Im blown away. Would love to see the dyno graph. Whats the rest of your setup? 

I still have all my old HPI and Zoom magazines. I should repost the builders guide to rb26 from HPI magazine. There it says that 400kw is stage 5 and is only for the serious builder with a huge budget. How times have changed.

I guess that's why with porting, most workshops now say go all out or don't touch it at all. 

 

hattori hanzo Community Regular

hattori hanzo

Posted
Posted
2 hours ago, khezz said:

Im blown away. Would love to see the dyno graph. Whats the rest of your setup? 

I still have all my old HPI and Zoom magazines. I should repost the builders guide to rb26 from HPI magazine. There it says that 400kw is stage 5 and is only for the serious builder with a huge budget. How times have changed.

I guess that's why with porting, most workshops now say go all out or don't touch it at all. 

 

Most recent update on the 30/5/20 post

it is currently having a new engine built, with a CNC (Rams Head)

 

http://antilag.com/forums/showthread.php?58554-DITB-GTR-Build/page17

hattori hanzo Community Regular

hattori hanzo

Posted
Posted
2 hours ago, khezz said:

 

I still have all my old HPI and Zoom magazines. I should repost the builders guide to rb26 from HPI magazine. There it says that 400kw is stage 5 and is only for the serious builder with a huge budget. How times have changed.

 

 

the old zoom and hpi mags, although accurate in the day are so far out of date it isnt funny.

 

ECUs are now miles better

pump E85

turbo tech

 

r32-25t Grand Master

r32-25t

Posted
Posted
39 minutes ago, hattori hanzo said:

Most recent update on the 30/5/20 post

it is currently having a new engine built, with a CNC (Rams Head)

 

http://antilag.com/forums/showthread.php?58554-DITB-GTR-Build/page17

Have you got your head yet?

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