400WHP on EJ20

Hey hope all is well everyone , Im getting ready to tie up my 02 wrx build , the last decision I have to make now is what I’m going to do about the shortblock , I’m looking to make 400whp out of this build , from what I’ve researched a new ej205 with forged internals can handle 400whp without to much trouble assuming the parts used and tune are of exceptional quality , but I am also considering iag’s 750 ej20 although I’m curious if that may be an overkill option for the power level I’m looking for , I’m not one to cheap out when it comes to my build in anyway but I do still respect opportunity’s to save money while getting the job done right. Does anyone have any experience or advice on building an ej20 to hold that power rating ?

(side thought , would a new ej207 v7 short block used with 205 heads be a cost effective option to hold the power due to the oem forged internals? Not looking to swap ecu’s)

JJ,

I've done it on EJ205 and EJ20x/y in stock form, but with an EJ207 shortblock I'm more comfortable running more torque.

300 ft lbs at 7000 RPM vs. 350 ft lbs at 6000 RPM to make 400 WHP.

I would put decent valvetrain and shimless buckets in the heads if you haven't already.

Hey Mike thanks for the reply , that’s awesome to hear , so I would be good to use my usdm ej205 heads on a new 207 block and be good to go forward right !?

With shimless buckets and upgraded valvetrain yes. I'd stick some stock STI cams in with the AVCS disabled for better flow.

Just be sure to control torque, avoid knock, all the usual stuff to keep the engine alive.

Hi Mike,

Why would you disable the AVCS?

If someone has budget for a full AVCS head conversion then I'd say go for it, but using EJ257 AVCS cams in EJ205 heads they have is a cheap way (usually 200 bucks plus a couple dollars in allen head plugs and a tap) to get a bit of extra power, without spending thousands on an AVCS head conversion, solenoids, gears, etc.

Got it, I read it as you have the heads with the AVCS available, but not using it.

Gotcha. I know some people like to remove AVCS, but I'm a fan of it as long as it's in someone's budget.

On a pure race engine that is going to be in a narrow operating window most of its time, then fixed cams optimised for that engine speed would be a potentially better option, but in a road car, or a race/rally car that is operated through a larger range, then the ability to optimise the cam timing would be worth while. I have seen some vehicles that have VVT get into all sorts of issues when using flat shifting, as the engine speed rapidly drops to a range that requires the cam position to move through a large range rapidly, and then come back out. This leads to the cams lagging a fair bit from the aim and not being optimal timing wise for the engine speed, so the engine bogs down or doesn't accelerate at its optimal capacity.

Stephen,

All good points thank you as always! Just in case anyone finds our general discussion interesting...here's a bit more...

I tend towards VVT unless a non adjustable has specs better suited to the application, or the engine cannot support oil flow to VVT and the rest of the engine. Serious drag car territory is where I find this most commonly occurs, but some engine platforms require it at more modest levels of modification.

I still use VVT cams on a lot of drag cars to help spool and extend the powerband for those times there's extra wheel spin, or the car gets out of shape and needs pedaled, or simply to help get a big turbo going without nitrous, torque converter, line lock.

I also know my view is somewhat impacted by my experience that I've never failed a VVT gear from flat shifting (yet), but I've seen a handful of fixed adjustable gears slip, and plenty of the non metal fixed gears break. I've also seen countless times how poorly cams degree without adjustment, so at least with VVT I feel we can easily move them around (independently if needed) and see what works best.

Maybe I take a more optimistic view of VVT by considering the brief delay before hitting cam target on a rapid shift to be far less of a performance concern than not having the cam advance capability at all. The unexpected VE change certainly isn't ideal, and I'm likely using workarounds I'm not aware of at this point because I've been doing it for so long. It's also possible my combination of cam target spread, oil pressure target, PID settings, etc. aren't making the issue as noticeable. I haven't had what I'd call a bog or issue, but that might just be a difference of what I think of when I hear the words bog or issue, and we are experiencing the same behavior.

I mostly see a delay to hitting cam target on rally cars and the occasional restricted non rally car since they're operating in areas of varying cam advance almost at all times, and rapidly shifting. My thought is those cars would usually be slugs without VVT, so I still consider VVT a big advantage despite it not being perfect.

Unrestricted circuit and drag cars I set up are mostly avoiding target delay by keeping RPM up where I'm not significantly varying cam targets during shifts.

As always, I really appreciate your insight Stephen. It's awesome to have you here.

It all depends on the range that the VVT is working in, most of the time with an engine that is used in a race car, the drop from the engine speed limit to the next gear on an up shift will not move the engine speed into the range that the cams are moving in, so it is not going to have an effect on them. Most of the VVT systems that I have worked on have the largest of the movement in the cams happening in the peak torque region of the engine speed, so relatively low in the engine speed range. There is however, a specific engine used in competition that has the majority of the cam movement happening in the mid to upper engine speed range and this is causing a lot of issues with the responsiveness of the engine after a shift.

Another area that can catch out the operation of the VVT system is a change in the oil viscosity used in the engine, especially an engine that has a cam driven DI pump/s. A fair amount of engines come out of the factory using a 0w-20 or 0w-30 oil so that the emissions are improved. However, what i have seen is that when these oils get hot (over 120 degrees) they have the viscosity of water and the cam control becomes sloppy as the actuators cannot maintain enough resistive force to overcome the spring load. With a DI pump it can become worse, I have seen FA2x engines lose all control of the Bank 2 inlet cam due to the load applied to the cam from the valve springs and DI pump (DI aim is around 20mPa) with higher oil temps. The cam just flops around, its position determined by the DI pump and valve springs, rather than the VVT actuator.

Great points. In I believe 2006 I took readings in the block's main gallery, back of the head, VVT banjo on an EJ257 over varied conditions and pressures. It reinforced how precariously VVT is fed compared to main bearings. Knowing the pressure drop from point to point really helped inform a lot of decisions I've made over the years. That was back during the aftermarket cam lobe/bucket failure era that we mostly steered clear of, and part of how we narrowed down potential causes.

I haven't researched the FA as deeply yet due to a refreshing lack of issues, but based on oil pressure in the block I've had all my folks with FA turbos running 5w40 since 2015, and F series NA stuff is 5w30 or 5w40 depending on use, climate, oil cooler. Factory oil temp monitoring helps make those decisions easy.

I'm still curious to see how many seasons my EZ36 holds up for with all the air shifting, road racing. I didn't know the exhaust phasing was pointless from a performance perspective when I put it together, so it's still a quad VVT setup. At some point I'll likely get bored and try aftermarket cams with exhaust VVT delete. The potential looks huge since the stock cams are super wimpy, but I'm already using half throttle opening to keep my engine within class limits so it's not high priority.

Yes, the Subaru AVCS actuators are given the dregs of what is left in the oil system to operate, sometimes its surprising that they even work at all.