questions on ej25t
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Joined: Aug 2003
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From: SoCAL
Car Info: ae86, 06 sti
questions on ej25t
aside the normal upgrades for ur turbos and intercoolers, does anyone actually ever buy better cams for the turboed ej25? if you have then what kind of cam? and how much total gain have you gotten? anybody ever try stroking the engine?
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I would not hold your breath for the cams for the USDM STi. That motor is not available anywhere in the World, and I doubt you will see some of the US tuners release the cams here.
Also, why would you want an aftermarket cam? With AVCS, stock cam should be spicy enought. Plus, its a big motor, so there are other things you can do and not have to mess with cams.
Stroking the 2.5 would be tough, as it is pretty much at the limit of the bore.
Also, why would you want an aftermarket cam? With AVCS, stock cam should be spicy enought. Plus, its a big motor, so there are other things you can do and not have to mess with cams.
Stroking the 2.5 would be tough, as it is pretty much at the limit of the bore.
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I am pretty sure that when he said "stroke" it, he meant increase the displacement. Becuase, increasing the stroke, would actually reduce the displacement. Or, I might be worng.
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From: BC, AB
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Increasing the stroke will increase the displacement, but you may come accross other problems, such as the crank not clearing the case, too much compression, buggering up the rod ratio.
Boring the cylinders will allow for an increase in displacement while retaining the stock rods, and crank. I read somewhere someone was doing a 2.7l conversion/kit. I suspect it is probably a combination of both boring and stroking.
Boring the cylinders will allow for an increase in displacement while retaining the stock rods, and crank. I read somewhere someone was doing a 2.7l conversion/kit. I suspect it is probably a combination of both boring and stroking.
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From: new milford, ct
Car Info: 02 silver impreza wrx
when you stroke a motor, u usually replace the rods, pistons and crank, b/c they all work in conjunction w/ each other to add more displacement, and create more power.
if you kept w/ stock rods, the angle at which they would come down at w/ a stroker crank, would most deffinately make them hit the cylinder walls.
usually, a lengthened rod is used, and a shorter skirted piston, to keep compression chamber the same size, but the stroke is much bigger.
there would also need to be some machining at the bottom of the cylinder walls to help a little bit w/ the longer stroke of the rod.
if you kept w/ stock rods, the angle at which they would come down at w/ a stroker crank, would most deffinately make them hit the cylinder walls.
usually, a lengthened rod is used, and a shorter skirted piston, to keep compression chamber the same size, but the stroke is much bigger.
there would also need to be some machining at the bottom of the cylinder walls to help a little bit w/ the longer stroke of the rod.
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To be honest with you i wouldnt mess with the cams at all on this engine. From what I understand about the engine the valves are Variable Valve Timing and assuming that you know how that works, changing anyhting witht he cams from stock would likely mess up the controll system, If the computer is telling the engine one thing and it reacts but has a different affect then you have a problem. Changing the size of the lobes from the stock cam can really be bad. If you wanted to go to titanium valves and springs you could probally do that and get some more power since it will be lighter, react faster and be more precision or even if they come out with titanium cam sure it would make it lighter but really unless you are going to redo the entire car, to gut weight from it you really need to start from scratch with everyhting, just doing the cam isnt worth it.
You are honestly better off getting a new turbo, turbo back exhaust, cold air intake, blow off, bigger intercooler, and when turboxs comes out with it a new UTEC computer for it and you will probally rock almost any and all cars out there and at the very least stay with them, but at least you will be able to take those kids who dumps 1000's into their hondas and will be trying to figure out why they cant touch you when you are like 200 ft infront of them, except for this car, i would like to see this race
http://www.lingenfelter.com/pac725ttls1y.asp
~thats the car designed
http://www.unclephilly.com/movies/li...hayabusa1.mpeg
~The same corvette racing a motorcycle
http://www.unclephilly.com/movies/Li...Hayabusa2.mpeg
~in car race of the motorcycle
You are honestly better off getting a new turbo, turbo back exhaust, cold air intake, blow off, bigger intercooler, and when turboxs comes out with it a new UTEC computer for it and you will probally rock almost any and all cars out there and at the very least stay with them, but at least you will be able to take those kids who dumps 1000's into their hondas and will be trying to figure out why they cant touch you when you are like 200 ft infront of them, except for this car, i would like to see this race
http://www.lingenfelter.com/pac725ttls1y.asp
~thats the car designed
http://www.unclephilly.com/movies/li...hayabusa1.mpeg
~The same corvette racing a motorcycle
http://www.unclephilly.com/movies/Li...Hayabusa2.mpeg
~in car race of the motorcycle
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From: new milford, ct
Car Info: 02 silver impreza wrx
theres nothing wrong w/ changing the cams on a variable valve motor. honda guys have been doing it for years.
all you have to do is get some sort of engine management, which will soon be readily available to the STI comunity.
if you want real big power gains, you might as well go all the way, while the motor is already out and apart.
you gotta pull the motor again if you wanna do cams at a later date.
all you have to do is get some sort of engine management, which will soon be readily available to the STI comunity.
if you want real big power gains, you might as well go all the way, while the motor is already out and apart.
you gotta pull the motor again if you wanna do cams at a later date.
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Car Info: 02 silver impreza wrx
pretty much, most companies w/ variable valve timing follow the v-tec idea cause it has worked very well for so long.
im not a honda fan by any means but they do last longer than almost anything else on the road.
im not a honda fan by any means but they do last longer than almost anything else on the road.
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Do not comfuse VTEC with Subaru's AVCS. That is a big mistake to think and more importantly say that out loud. 
First of all, VTEC is patented by HONDA so no one else besides HONDA uses that type of variable valve timing.
HONDA's VTEC is essentially a dual profile camshaft which shifts at a given RPM based on oil pressure. It is a simple "on/off" dual profile cam.
Subaru's AVCS is completely different animal. It uses slide cam sprokets with can advance or retard cam timing by +/- 30' "DYNAMICALLY". It is not "on/off". Cam timing is constantly adjusted by the ECU based on a whole bunch of parameters. It is controlled by oil pressure and duty cycle selenoid which controls how much oil pressure to allow to go into the sproket slide mechanism.
This system is similar to TOYOTA's VVT and BMW's whateverthehellitscalled.
On STi, only the intake cam sproket has AVCS. On Forester's XT, it is both intake and exhaust.
So, you can swap a "spicier" cam into a AVCS EJ motor and get good gains. For example, STi Spec C cams have more agressive profile than the regular STi's. That is on EJ20 AVCS heads. I have no clue if those cams can be used on USDM EJ25 AVCS heads.
First of all, VTEC is patented by HONDA so no one else besides HONDA uses that type of variable valve timing.
HONDA's VTEC is essentially a dual profile camshaft which shifts at a given RPM based on oil pressure. It is a simple "on/off" dual profile cam.
Subaru's AVCS is completely different animal. It uses slide cam sprokets with can advance or retard cam timing by +/- 30' "DYNAMICALLY". It is not "on/off". Cam timing is constantly adjusted by the ECU based on a whole bunch of parameters. It is controlled by oil pressure and duty cycle selenoid which controls how much oil pressure to allow to go into the sproket slide mechanism.
This system is similar to TOYOTA's VVT and BMW's whateverthehellitscalled.
On STi, only the intake cam sproket has AVCS. On Forester's XT, it is both intake and exhaust.
So, you can swap a "spicier" cam into a AVCS EJ motor and get good gains. For example, STi Spec C cams have more agressive profile than the regular STi's. That is on EJ20 AVCS heads. I have no clue if those cams can be used on USDM EJ25 AVCS heads.
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thats cool...i already knew how the vtec worked...i didnt really care much for it b/c its torqueless...butt he avcs is soo much better..great potentail...thanks for the info...sry bopit the misspelings my handa are ferezing and i cant taype
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Stroke is far the piston moves in the cylinder. Longer stroke, the further down in the cylidner the piston goes. Increasing stroke therefore increases displacement, but it also hurts you're R/S ratio (rod stroke ratio). R/S ratio is bassicly the ratio between how far the piston moves and how the long the rod is. The tradeoff is that with the longer rod you get more displacement, but you also force the rod to swing out sideways further. The more sideways the rod has to go, the more lateral stress is put on it, making it much easier to snap. This sideways motion also increases sideloading on the piston, IE it pushes the piston sideways agaisnt the cylinder harder, not what you want. So, it comes down to higher R/S, higher displacement, but lower revs. Lower R/S, lower displacement, higher revs.