I purchased a Forge RS BOV for my EVO X for many reasons, holds more boost, better looks, adjustable with modifications, and ofcourse some ricer goodness a nice "whoosh".

However, over the last two months I been throwing a p1241, which I had thought it was from not being tuned. I installed the BOV along with other power adding modifications while being tuned by a OTS map from COBB for the AP Tuner.

Many times a week the car would act up and throw a limp mode on the highway in 4th or 5th gear. The conditions generally were on a slight incline / hill. I was in a partial throttle/boost situation where the boost was below 4 psi. The characteristics were I was either trying to maintain a desired speed limit or maintain a steady speed on a incline, which generally requires lite manipulation of the throttle.

Fast forward to to July 24th. I was headed to CBRD for a custom tune for my EVO X. The 5 hour journey took longer than expected throwing a limp mode every 60 miles going through the mountains of PA. I got to CBRD, Chad got the X and got the tuning rolling. The tuning went smoothly with the car making great power on his low reading Mustang Dyno.

It was around 430pm, the tuning was done and I was headed to Washington D.C. for some RR. I got about 20 miles away from CBRD when going down about 75mph I hit the p1241 limp mode again. Calling Chad back up at CBRD I returned back for a revision of the tune.

Chad gladly made some modifications to the maps and I was off again back towards D.C. Chad made changes to the Torque Limit maps the reason why the p1241 gets thrown and the car goes into limp mode. Going about 13 miles away from CBRD I throw the p1241 code again. Call Chad backup to get advice, I unmarry the AP Tuner, and reinstall it. I then reload the custom map, and began the trip back to CBRD, while on the way back I throw another p1241.

Finally getting back to CBRD, Chad and I began a quest for the reason why code keeps getting thrown. Contacting BR, GST, HBspeed, etc... No one has a definite answer why this is happening after a perfect tune.

So after much debating and changing the maps one more time. Chad and I decide to change the BOV back to the stock one (luckily I brought mine as a spare). I was off again to D.C. finally at 830pm. The rest of the trip the car worked perfect no issues at all. So I figured that the BOV was the issue hear behind the p1241.

TEST:

Fast forward to today. I began testing to why the BOV was causing the issue with the p1241. The test consisted of a pretty normal little experiment. I first started with the stock BOV, I covered up the hole for the stock BOV in the inlet pipe. The I set the valve to be VTA, got the car up to operating temp at idle and checked the valve. The plunger was closed shut. I put a regular party baloon over the VTA exit. Let it rest at idle. The balloon stayed flat, and DID NOT inflate.

Performed the same test with the FORGE RS BOV. I put it in place of the stock valve. I set the valve to the softest setting (~7psi spring Tension as listed in the Forge Directions) with each click of the wheel the adjustment should be 0.519PSI so 37 clicks = 19.2 PSI + 7 PSI = 26 PSI. What my car is tuned for. I set the BOV to that setting what do I see to my amazement the FORGE RS BOV is still open at idle with 37 clicks. No need to ad a balloon to see if it is leaking. I turn the adjustment all the way in towards the positive side. I get maxed out at about 50 clicks. About 33 PSI total with spring tension. I look the FORGE RS BOV plunger looks closed. I put a ballon on the VTA to air side. Yes, it is still leaking, the balloon is inflating with the car just sitting at idle. I take the balloon off, and REV the engine. The engine revs, but the BOV plunger is stick/ spring is sticking. Because the RPM's take a few long long seconds to come down. Therefore, there is too much tension on the spring causing it to bind, when it is compressed even further.

Conclusion:

Do not buy the FORGE RS BOV, it does not work properly for the EVO X. It simply does not stay closed at vacuum, which will cause BOV to flutter and then throw a p1241. Stay with the stock BOV.

I am going to contact Mike @ Forge to talk about this issue, because otherwise it is a $230 dollar paper weight sitting around. If possible they can make spring to hold a bit more than 7psi at idle for the FORGE RS.

 

Please see my PM to you.

Your test outlined above is not really a valid test of anything at all. Our valve sounds as tho it's functioning perfectly fine.

The intake manifold vacuum will pull virtually any and all valves open at idle, which is not a problem in any way when running them in a recirculating configuration as they are venting back into the intake POST-MAF maintaining the closed loop system, actually NOT causing a loss of pressure whatsoever. Virtually all single piston push type valves will be pulled open by engine vacuum at idle. The only reason they wouldn't is if there is a leak preventing engine vacuum from acting on the piston, or if the spring tension is so great that the vacuum can't overcome it.

The reason our valves will be pulled open at idle is that the spring pressure is not so stiff as to keep them closed at idle, which would otherwise result in a spring tension so stiff that the valve wouldn't discharge properly at throttle lift....

....furthermore, our valves don't incorporate the small ridge up the back side of the OEM valve body which serves only to delay the valve's response at partial throttle/boost conditions, which also prevents it from being pulled open at idle.

Atmospheric valves are a different story entirely, and you do NOT want them pulled open at idle.

Please have a read of this thread:

https://www.evolutionm.net/forums/en...alve-tech.html

The issue you're experiencing is either due to improper tuning of the valve, a leak within the vacuum reference to the top of the valve, or some other leak preventing it from operating properly under load or during transition phases.

 

Thank you for the response Mike. However, even though you say there is nothing wrong with the design and saying it is functioning. It is causing tuning issues with the EVO X. The valve is positioned in the stock location and recirculated. It should not be the reason it is throwing a limp mode in this EVO X. I tried to run this valve, every possible way and I keep throwing the same CEL, only being fixed with the replacement of the stock BOV.

Therefore I see it as a way that the product is not working well with this platform, and causing some sensor to read the unmetered air incorrectly and throw a limp mode. I set the valve to basically 7psi and it open at idle, it will throw the p1241, I set the valve to the desired setting per the manual and I throw a p1241, and I set it to the max setting with plunger almost closed. The valve (sticks or spring sticks) and causes improper release of air, as throw a limp mode code.

 

I am doing some testing between the stock valve and Forge RS valve. The stock valve held to 26.3 psi in a 4th gear pull from 2000 rpm per COBB AP relative pressure (this is about 25-24.5 psi, since the reading is about 1 psi off per the Mustang Dyno at CBRD).

I put on the FORGE RS with the valve set a (-) all the way with 0 pretension. The valve held to 27.8psi from 2000rpm in 4th per COBB AP relative pressure (this is about 26-26.5PSI which is what my car is tuned for per CBRD Mustang Dyno pressure read out). It is very clear at his point that my stock valve did not hold pressure as well as the FORGE RS valve. However, spool response was very slow, since there was too little spring tension and the car felt a bit mushy at this point.

I set the FORGE RS to 3 turns (+) from the 0 pretension. The test from 2000 rpm in 4th yielded about 27.8 psi per COBB AP relative pressure. Held similar to 0 pretension valve setting. However, the turbo spool and response was much more lively. Spooling very quickly now, compared to the 0 pretension. I took it on the highway and tried to make it throw a p1241 I was not able to have it throw in about 10 miles of highway driving going from vacuum to boost changes. There was no rattle snake sound from the plunger moving back and forth.

I set the valve to 4 clicks (+), test from 2000rpm in 4th yielded 27.9 psi, which is very similar to the past readings, holding boost very well. The response is pretty crisp, no rattle snake plunger sound at highway speeds 65-75mph. I tried to induce the p1241 but no luck after another 10 miles. The release is pretty smooth. Holds boost well. Car is pretty drivable. Feels pretty stock, when comparing BOV's.

I will keep it at 4 clicks in for a week and see if I manage to throw a p1241 at any point in time. This about 9.1psi of spring tension per FORGE RS instructions, each click is 0.519psi however it is not always linear.

Stay tuned for further testing.

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When I was throwing the p1241 the valve was set to 22-24 click (18.5 psi to 19.5 psi), which was too stiff it seems causing a rattle snake sound and partial let offs.

I will keep adjusting the valve until I find a happy medium. Hopefully this will helps anyone else that has issues with their BOV or FORGE RS valve.

 

same here with HKS SSQV, P1241 as you mentioned above.
Many tests and re-tunes with no luck.

 

As of now, I think your best bet if you want to continue to use the HKS valve, is to set it to the softest setting and slowly work your way up. I think the fluttering of the valve that is caused in many aftermarket BOV causes some problem with the ECU handles tuning in the X.

CBRD told me they used the APS with no ill effects, problem is those are not rebuildable. Since they drill out the bolt tops. Nothing a bit of JB weld and a nice long think nail wouldn't fix with a pair of vice grips.

 

when i ran the forge RS on my stock turbo (evo 8 though), with the spring adjusted where it was "sopposed" to be, the car would buck tremendously on the highway when lifting off the throttle. this would certainly cause a code on the X. the solution to the problem was to adjust the valve as soft as it would go. almost entirely eliminated the bucking on the highway, still held boost well too. with the 35r im on now, i have it adjusted much stiffer, and it doesn't buck at all unless im in the throttle hard and gently lift off at high rpms.

my recommendation with the forge RS is to run it on the softest setting unless it is not holding boost well enough.

if you are still throwing the code, have CBRD try the new tephra airflow check disable... that should eliminate your limp mode issues.

 

Thanks Kevin, that's what I started doing. Set it to the softest setting and turned it up 4 clicks. So far so good, but time will tell. The FORGE instructions do not apply to the EVO's since then the springs get to tight.

Thank you for the advice.

 

I will never understand why people choose to keep a BOV on after so many problems, just take them off

 

Because my stock valve does not hold 26 psi...

Best it will do is about 25 psi before it starts to leak.

Plus sometimes you need a bit of trial and error to inform others and learn from mistakes or how to fix problems, otherwise we all would be driving around stock evo's.

I know everyone think that BOV's are only for the whoosh factor, but some require them since their stocker is the crappy one where it doesnt hold 27 or 28 psi like some do. It's a hit or a miss.

 

I dont understand how some people run 30+ on the stockers without any problem?

I understand what you are saying also, I tested 5 different BOV's on my old SRT-4 and 3 on my old EVO 8.

 

cant use the airflow fix on a cobb protune

cb

 

First, thank you for posting this thread as it finally convinced me to try the RS valve I took of my VIII on the X.

Are / were you running the RS VTA by chance?

I'm asking because I'm running mine recirc as intended for maf cars and it works perfectly. No codes at all and stock drive ability. I have it set 4 clicks in from full soft. Spool and throttle response are noticeably quicker than with the stock valve and I picked up an extra pound of boost from spool through fuel cut, despite the fact that my ebc was still set for the 1psi lower boost level.

Given the quicker response, it is possible that some of the limit tables may need adjusting after adding this valve, more boost at part throttle and or quicker spool can absolutely throw you into load cells you were not hitting with the stock valve. This is no different than any other breathing mod as they all have the potential to cause trustfull codes if your not properly tuned for the upgrades.

Btw, it fits just fine with the nisi lower ic pipe (the one the relocates the valve under the air box).

 

The X diverter valve is the same as the 9's DV.

They are so hit or miss as far as when they will leak. Many people have used the crushing method to make them hold more boost, I guess it works pretty well. My stock DV is holding 30ish psi just fine, but it would probably be wise for me to upgrade it soon.

 

mine works perfectly well no issues at all !!