cams and mani yet?

[Grip Ronin]

im still curious as to where is this motor losing power. a 2 liter with 12.5 compression only putting out 178 whp with a full exhaust and intake seems ridiculous. Working around hondas and nissans alot i know a 4cyl can make good power n/a. Has any companies started developing cams and checking the flow of the heads and intake manifold?? maybe thats whats suffocating this motor.

[Coheed]

This engine has great thermal efficiency, but I still think compared to the engines you are thinking of the Volumetric efficiency is a little behind.

I wouldn't expect it to pump out power like the K20, but it does get pretty close.

I'd like to see what cams can do with this engine. But I'd hate to see the engine lose that bottom end grunt.

[Opposed]

The heads flow great actually. Some tuners are revving this thing to over 8500 rpm with boost and it continues to make power. Most have suspected the VE to be affected by the stock intake manifold. I maybe know of one shop that is playing around with IM's and there have been some threads from Ferrea about valve springs and retainers and cams? that claim some big N/A numbers, but I haven't seen anything yet.

[OrbitalEllipses]

Originally Posted by Coheed

This engine has great thermal efficiency, but I still think compared to the engines you are thinking of the Volumetric efficiency is a little behind.

I wouldn't expect it to pump out power like the K20, but it does get pretty close.

I'd like to see what cams can do with this engine. But I'd hate to see the engine lose that bottom end grunt.

Depends on how aggressive the cams get. Something like a Kelford 264 grind doesn't typically lose much on the bottom end while still making gains on the top end. Something like a Cosworth manifold will typically lose some bottom end and trade it for top end.

[ziggz501]

I wouldn't mind losing some bottom end for some more aggressive cams. I want to keep this machine n/a, but its gonna be difficult if nobody puts out some quality internals. the one thing i loved about my old GSR was that it would scream if I wanted it to. I could care less if its bottom end torque was crap. drop a gear or two and floor it. i dun care what people say about vtec, a cam with multiple levels of aggression is beast.

[Grip Ronin]

yea some variable valve timing and overlap would be nice. i feel like im driving a LS motor compared to a GSR. might anyone know the stock cam sizes?

[Dimman]

Originally Posted by Grip Ronin

yea some variable valve timing and overlap would be nice. i feel like im driving a LS motor compared to a GSR. might anyone know the stock cam sizes?

I think it's ~255° duration in/ex. It's in a document on here, somewhere. Can't find it. Lift I don't know yet, but I would guess ~8.5ish mm.



Btw, the car does have variable valve timing and overlap. Dual AVCS handles it.

[Grip Ronin]

Originally Posted by Dimman

I think it's ~255° duration in/ex. It's in a document on here, somewhere. Can't find it. Lift I don't know yet, but I would guess ~8.5ish mm.
Btw, the car does have variable valve timing and overlap. Dual AVCS handles it.

it does? thats the subaru designed one right. no cross over or noticeable gains like mivec or vtec. i had saw somthing about this long before i bought the car but they never touched on it again and its not even a selling point. id assume since toyota made the heads they would have vvti

[Dimman]

Originally Posted by Grip Ronin

it does? thats the subaru designed one right. no cross over or noticeable gains like mivec or vtec. i had saw somthing about this long before i bought the car but they never touched on it again and its not even a selling point. id assume since toyota made the heads they would have vvti

AVCS and VVT-i are functionally identical cam phasing. The timing is continuously variable, which controls the advance/retard of both cams, which can change overlap on the fly.

You are probably confused with lobe-switching, 'lift' type setups, like VTEC and VVTL-i. Those change over to a secondary lobe that will have longer duration and more lift. Subaru's version is called AVLS.

Lobe switching and phasing can be combined. VVTL-i and iVTEC use both (but not always on both cams).

[xwd]

Originally Posted by Grip Ronin

it does? thats the subaru designed one right. no cross over or noticeable gains like mivec or vtec. i had saw somthing about this long before i bought the car but they never touched on it again and its not even a selling point. id assume since toyota made the heads they would have vvti

There are very noticeable gains. Try turning it off and see how the car performs.

I don't think they really hype it because all of Subaru's engines and most other manufacturer's engine use this these days. It's something expected not necessarily something special anymore. Subaru did develop the i-AVLS system as stated which is similar to VTEC.

Like others have said the intake manifold may be a source of some gains but that remains to be seen. The heads flow very well as seen in the turbo applications. It's a different type of motor, it makes more torque than most other low displacement NA motors in the 2500-3500RPM range but doesn't spin to 8500+ RPM where it can make more peak HP like most Honda engines. I for one don't like having to wring an engine out to 6000-8500 RPM to make power.

[FreshFRS]

Originally Posted by dwx

There are very noticeable gains. Try turning it off and see how the car performs.

I don't think they really hype it because all of Subaru's engines and most other manufacturer's engine use this these days. It's something expected not necessarily something special anymore. Subaru did develop the i-AVLS system as stated which is similar to VTEC.

Like others have said the intake manifold may be a source of some gains but that remains to be seen. The heads flow very well as seen in the turbo applications. It's a different type of motor, it makes more torque than most other low displacement NA motors in the 2500-3500RPM range but doesn't spin to 8500+ RPM where it can make more peak HP like most Honda engines. I for one don't like having to wring an engine out to 6000-8500 RPM to make power.

i'm inclined to think the the relatively small capacity of the stock intake manifold causes the car to run out of breath in the higher RPMs. it doesnt have enough capacity to support the consumption of the heads at high rpms. a bigger plenum would help in all cases except Positive Displacement superchargers where small plenums are ideal to reduce pressure loss.

[xwd]

The only hole in the theory is the car with a turbo doesn't run out of steam at higher RPMs until very high HP levels.

[cruzinbill]

Originally Posted by dwx

The only hole in the theory is the car with a turbo doesn't run out of steam at higher RPMs until very high HP levels.

Cus it was secretly designed for FI, just too convenient it does so well with it.

[Grip Ronin]

Originally Posted by Dimman

AVCS and VVT-i are functionally identical cam phasing. The timing is continuously variable, which controls the advance/retard of both cams, which can change overlap on the fly.

You are probably confused with lobe-switching, 'lift' type setups, like VTEC and VVTL-i. Those change over to a secondary lobe that will have longer duration and more lift. Subaru's version is called AVLS.

Lobe switching and phasing can be combined. VVTL-i and iVTEC use both (but not always on both cams).

ya i never really heard much on avls. i like the lobe switch so u can keep you low end grunt and breathe up top