cant say i disagree there. they built the whole damn package to pull stumps at 2000rpm....
N54 head work
- Thread starter fmorelli
- Start date
cant say i disagree there. they built the whole damn package to pull stumps at 2000rpm....
its just a saying, maybe not very global. the point of the story is that the manufacturer optimized airflow for low rpm range because the engine spends most of its time there.
that's why i was wondering about the ramp rates in aftermarket cams. i figured there isnt much being gained in the head from absolute peak lift so the "STA - specific time area" would be maximized through how aggressive the came profile is. and the more aggressive the more acceleration / deceleration of valve weight the springs have to deal with. but clearly the design objective for market success would be "design a stage 1 cam so that the customer doesnt need to spend any more money but still shows improvement". and they would then find the line were stock springs work but still manage to stuff more STA in there.
note i am not debating the merits of anything in particular here the subject is just one of interest. i tried modelling the n54 in EngMod4T years ago and it struck me that the head made more power that it theoretically should, i put the differential down to the affects of DI. that is only helpful for the amount of fuel the injectors can stuff in while the intake valves are open, so the first 300-400whp or so. after that the head s8cks balls. its been too long since i looked at it but i'm guessing the exhaust port size becomes are restriction after doing port work closer to the cylinder, which is why its just better to start with a different head all together.
not to take away what is being done in this thread - i appreciate how the OP arrived in this scenario.
Sorry to say I won't have an A-B dyno test, as when this ultimately goes on it will be with other changes (i.e. turbos). I do plan to make a plate and get the head flowed so we know what the CFM is over stock. But I would imagine that kind of info exists elsewhere ... ?
My guy got back to me and so I'll take the head to him next week to assess next steps.
Filippo
My guy got back to me and so I'll take the head to him next week to assess next steps.
Filippo
According to my EA Pro sim, cams are good for +35bhp, the N53 head conversion alone for +55bhp, and both of them together +100bhp - i.e. more than the sum of each individually.
Yeah and unfortunately there won't be a before/after for mine either since I never dynoed stock and my turbos were SHOT before doing the head anyways.
In my case, wanting a streetable 600whp on Emix - and Omar points out that the 650s tap out lower than the 850s - the idea is to lower the boost not raise the horsepower. My understanding is that one way to look at boost is a measure of engine inefficiency. My hope is, by getting some restriction out of the very restrictive N54 head, running the low-lift Schrick cams (which have a better profile for flow), that we can lower heat and lower boost demand from the 650s turbos. This is about lowering the work the turbos have to do.
This is spitballing on my part.
Filippo
I would argue the only replacement for displacement, is revs. I would always prefer more displacement in general.
Given we are stuck at basically 3.0L for all intents and purposes and our undersquare design means the n54 will never be a 'real' high reving motor. It is what it is I guess.
This whole concept of boost being a measure of restriction is flawed, for as long as the turbo is operating in a reasonably efficient part its operating envelope I find it best to think of boost as a density multiplier on top of whatever the base engine puts out @ a pressure ratio of 1. For instance a bone stock N54 is good for ~220bhp @ 0 boost on the stock tune and with the stock turbos running stock boost. Your typical tuned FBO N54 running HP800s fares a little better, and is good for 240-245 due to the freer-flowing exhaust setup and lower pumping losses. A setup like mine however with cams and N53 head, is good for ~295bhp or thereabouts before any boost is added. To arrive at these numbers you take good ballpark SAE/DIN bhp figures and divide them by whatever density ratio you're running (in itself a factor of boost + intercooler effectiveness). In other words, adding cams to a naturally aspirated N54 will increase bhp/torque, as will porting of the cyl head. Adding boost just amplifies said gains, and said gains mean you need less boost to hit a given power target. Less boost means less heat, lower cyl pressure, and (at this level) greater adiabatic efficiency so its win/win on all fronts.
It'll never be a "real" high revving motor due to the DME's hard limit of 8100rpm. 4G63s and various Hondas are similarly oversquare, and that doesn't prevent them from revving to the moon. The piston speed of an N54 running @ 8100rpm works out to 24.2m/s which, while somewhat high, is far from being a limiting factor.
If Syvecs ever becomes a thing again it would solve a lot of our problems. I know it's expensive but honestly at $5k its a better mod than a port head IMO
I really hate the way we tune this platform. Not being able to alter a VE table is so silly
