Ive had more boost problems with this car than i can remember. i thought i had experienced every possible cause there was until now. Ive been through boost leaks, blown gaskets, cracked manifolds causing slow spool up, the infamous wga not being tensioned correctly, overboost, you name it. i found and fixed just about every one of the problems myself before asking for help but this one is beyond me.

Let me first start by explaining the events leading to this problem. I finally decided to get my car tuned and so it began. was on 28-29 psi on an evo 8 turbo with a 10.5 housing, forge wga, and hks evc. those are really the only things that should be relevant. tuner told me to turn the boost down to around 26-27 psi. i have never had the ebc "on" i have always controlled boost via the wg actuator by adding a turn or two of preload or loosening it. it is an 18-25 psi actuator diaphramless piston type actuator. i could spike to 29 and hold about 24 to redline with it preloaded way down. i loosened the preload some to get the tuners desired 26-27 spike. on one of the logs he noticed a boost leak. checked and sure enough the egr hose blew off. fixed that and continued. he then told me/ i would need to turn the boost down further due to excessive knock. i tried loosening the preload more, but to my surprise boost started to spike to 29 and hold 27 to redline. he told me he would just take out timing since i was having problems. when we finished i basically was tuned on a spike of 27-26psi and holding boost really well.

i was pleased with the results but confused on the underlying problem of why i couldnt loosen the preload and get the stock 18 or 19psi like i use to. pulled the wga out to rebuild it since i had a forge rebuild kit laying around. once apart one of the two o rings were torn. it was the top o ring and it had wedged itsefl between the cup and wg housing. i figured this is what was keeping me from boosting lower and that it was just binding the piston up not allowing it to open until 27psi. assembled it back together and reinstalled. this is were my new problem comes in.

i noticed when i reinstalled it, i had to turn the turnbuckle WAY out to get it to go over the flapper arm. i didnt think much of it and preloaded it the same way i always have, (barely fits on the arm, then turn it in 3 1/2 to 4 turns and reinstall). took it for a drive and i hit 12 psi? ok i knew something wasnt right so i checked all the lines and found nothing. so i cranked it down some more. this time it hit 15... turned it in some more, still 15 psi. well today i cranked the preload down to where i physically could not pull the arm back up onto the flapper. it still has plenty of thread left. Finally HERE IS THE PROBLEM when i went for a test drive it still only hit 15 psi, but i held it wot a little longer at 3500 than before and then boost went to the desired 26 psi? what i mean is boost will hit 15 psi stop and fall to around 12 (i can hear the wg open because i have an o2 dump) then it osunds like the wg slams shut again and boost quickly goes to 25 psi. It sounds and feels exactly like vtec would when it hits 15 psi falls then shoots to 26 psi. please help wtf could cause this? the tuner was nice enough to say he would review a few new logs since i rebuilt the wg just to make sure it was still spot on, but now i have this problem and i sure as hell dont want to spend another 400 bucks for a retune when i finally get the problem fixed. sorry for the rant just wanted to be specific and thorough with as much info as possible.

 

What kind of bov are you using? I had a similar issue where i would only half-boost unless at WOT, and it would spike up and down. In my case, it turned out that the tension spring in my BOV actually broke in half.

-Also, it's better to use a boost controller if you're changing boost all the time, why mess with the WG if its working?

 

I'm not sure if I missed it in your post, but what color spring is in your forge WGA? It sounds to me like you have the 14-16psi spring, and because you have so much preload on the WGA, your wastegate isn't actually opening fully.

Also, you want to make sure that when the forge WGA is put back together, you are installing it in such a way that the actual actuator arm moves freely under pressure. What I have seen with this particular WGA, is that if the spring/arm is slightly cocked to one side during installation, the wastegate will not open during high boost. The air inside the WGA will actually inflate the rubber boot around the arm, and escape through there.

Additionally, you said that your ebc wasn't "on." Are the associated vacuum lines all installed correctly to the unit?

 

Where's Sparky...

 

Vtec is fast yo...I don't know why you're complaining.....

 

All lines to everything are installed correctlyy and controlling the boost via wg should not be a problem since i have always done it before and it worked fine... wg spring is not 14 psi it is an 18-25 psi actuator. And spring is too rusted to tell what color it once was anyways. Also bov is fine holds 30psi when doing leak test which i have already done. Ill try to take a video and upload it

 

here are the videos. the first is the actual problem. the second video i turned the wg turnbuckle in 2 full turns from where it was in the first video, and the problem went away, but boost went to 30 psi which is no good lol. i then backed it off 2 turns to see if maybe something was binding and it fixed itself but that was a no go. also boost leak tested the car again today... no leaks, no surprise. pulled the wg actuator back apart, looked fine, checked with a compressor to see if it moved freely, it did so at 20 psi like it should. reinstalled, and going for a drive after i post this and will report back. let me know what you think with the videos. i honestly am leaning towards a shot turbo or blown gasket somewhere but keeping my fingers crossed.

http://s400.photobucket.com/albums/p...urrent=015.mp4

second video no problems boosting to 30 psi just spools a little slow.

http://s400.photobucket.com/albums/p...urrent=013.mp4

 

bump... please someone help. i would hate to have wasted 400 dollars on a tune for this to happen. bout ready to sell or part this pos out.

could it be the wg spring itself has went to ****? throwing out ideas here. i can literally preload it all the way to where i cant pull the rod back up on the turnbuckle and it still spools slow and blows the flapper open at 15 psi so maybe the spring has just lost all its tension?

 

I am never 100% convinced that EBC's are totally neutral and transparent devices even if and when they are supposedly turned "off". If it is connected then I'd like you to diconnect it completely from the vacuum/boost loop. Set it aside up on your bench in the garage for the time being. OK?

Remember the routine where you run a short length of hose directly from the nipple on the compressor discharge tube(aka "J-Pipe") to the nipple on the WGA. Well hook everything up this way and do some WOT runs. Play around with the actuator rod length seeing how the boost level reacts to this direct adjustment w/o the EBC in the loop at all.

If boost is still weird then I would definitely suspect your Forge piston-type actuator. You already disassemvbled it a couple of times and replaced the O-rings. It may be an clearance issue re piston/wall dimensionality.

I would just bite the bullet and buy the relatively less complex and functionally proven FP HD 18# actuator which should be good up to about 29-32# levels with a little modification. Or just get the 25# FP HD actuator if they have it for an VIII turbo.

Bottom line is that I think your fancy actuator is at fault. The piston-type is claimed to be superior in design to the diaphragm style actuator by Forge Motorsport. But, that is just a manufacturer's claim. The diaphragm style actuator is a proven design. The Forge piston-style actuator is theoretically superior but in actuality has not been proven under longterm use. You yourself had problems with it developing sealing issues.

Let's try a different actuator.

 

I started to suspect the spring was failing due to heat cycles and it had completely lost. its tension. I went the ceaper route first and spent 45 bucks on all of the springs they offer.. i installed the red spring which is 19-24 psi.it took 5 full turns of preload just to hit 18 psi. With the ebc on and halfway up it is dialed in at 25 psi but i doubt that it should take 5 turns of preload to hit only 18 psi. The search continues.

 

Let's stop and think about it just a little bit. You state above that the "Red" spring is rated at 19-24#. In this case, what do these two numbers actually signify? At 19# the waste gate puck is supposed to start to lift, or, "crack" off its seat on the turbine housing. By the time that seat pressure reaches 25#, the waste gate puck is full open. So, starts to open at 19# and is full open by 25#.

These numbers although useful in categorizing and differentiating the different spring rates available, tell us little or next to nothing about the rate of lift of the flapper valve when that particular spring is acting against it in an un-preloaded setting.. The rate of lift of the flapper valve can be altered significantly by adjusting the length of the actuator rod via rotation of the turnbuckle, and/or by cutting the rod itself.

In your case OP, I'd like to learn from you exactly how many PSI increase do you see on your boost gauge for each complete 360* rotation of the turnbuckle on that actuator? Is each half turn equal to one PSI? So, then each full turn is equal to 2 PSI? I am just guessing as I have never fiddled with the piston-style actuators myself.

If the Forge VIII piston-style unit is anything like the Forge VIII diaphragm actuators that I have used in the past then the actuator rod is excessively long and will need to be trimmed to improve response and resolution. This excess actuator rod length can help explain why the actuator does not seem to respond to those initial 5 turns which you dialed in. This is one of those situations where longer is not always better.

It has been noted before that Forge intentionally leaves the rods on their actuators extra long so that a single actuator rod can be cut to measure and made to work on the entire range of compressor housing/turbine housing combos possible for the VIII 16G turbo lineup. The same actuator has to be able to fit a turbo configured with the VIII compressor cover and a range of three different turbine housing sizes.

 

The manufacturers' claims for actuators is not always accurate in all applications. For example the Forced Performance actuators are claimed to be an 18# actuator but they are full open by 14# when installed with no preload. The Forced Performance 25# WGA is advertised as being a 25# actuator but when installed with no preload it is open by 18# in some cases. So, you can't suppose anything and manufacturer's claims should always be taken with a grain of salt when dealing with actuators. There is a certain amount of fudging going on....

 

Are you happy now?

 

If the actuator rod is relatively long and/or the internal spring rate is too light, and little or no preload is applied, it not only impacts the cracking pressure of the gate. It can and does affect the "rate" at which the valve opens or lifts.

That is, with the rod too long and too little preload, and a too light internal spring, the flapper valve may lift really easily and quickly for the first degrees of travel through its lift arc in the 18-22 PSI boost range. So, for example the puck may jump from a closed 16-19# up to 22# almost instantly before the spring compresses sufficiently to slow the rate of spring compression down significantly. Whereas with a shortened rod, a stiffer spring and more preload the valve not only stays on its seat longer and "cracks", or starts to lift later, the rate of lift is also significantly slower. So in the same 18-22 PSI range less exhaust energy is being bypassed and thus more energy is hitting and powering the turbine blades.

 

This is what happens when your usual professor calls in sick and you get a substitute lecturer(me, LOL) in your, Internal Wastegates 101 seminar.