Hey guys. Just got a new DBB FP Green with an 18psi actuator. When I run gate pressure I only make 14.5psi. Does that seem normal? Boost leak? Wrong actuator?

I did a boost leak test about a year ago with my old turbo and it was fine. Just wanted to know if I should be checking again or if it is in the normal range.

My old turbo made about that with a stock actuator.

Thanks.

 

Congratulations on your new turbo. How exactly did you determine what you call gate pressure? Are you using a MBC to control boost?

To determine gate pressure did you just turn your boost controller knob down to its lowest possible setting? Or, did you test with an air pump and a gauge? Or did you run a hose directly from the J-Pipe to the WGA? Are you sure that the actuator rod was adjusted to its lowest tension point?

At any rate, 14.5 PSI of base spring pressure is fairly normal for the FP HD 18 PSI actuator. Mine gave me a 14 PSI reading when I first tested it back when. So, I would say that everything is OK. Probably no boost leak. Perhaps you tested the stock actuator vs. the new actuator at varying levels of prelaoded spring pressure. Incidentally do you use a digital boost gauge?

 

I tested by first turning my HKS EVC off which operates just like plumping J-pipe to actuator. I then plumbed J-pipe to actuator just to be sure. Yes I have a digital boost gauge.

I also tested with an air compressor without a digital gauge. Starts to open at 15psi-ish and fully open by just below 20.

I have now preloaded the new actuator as far as it will go but it initially boosts to 14.5psi and then goes up to 20.3psi moments later so I dont think I have enough movement in the flapper so I will back it off a bit so it holds a solid pressure.

I thought it all seemed to be right but just wanted to run it past someone who had used an FP Actuator before. Threw me a little bit when an 18psi actuator made 14.5psi.

Thanks.

 

is your boost sensor tied into & right @ the j pipe? if not, your boost sensor is probably seeing pressure loss across the fmic, piping, leaky bov, etc.

quite honestly, i have never tried running my turbo plumbed from the j-pipe / discharge pipe to the actuator, so i cant share any personal results.

 

I would do a boost leak test.

 

Why do you say that you preloaded the actuator as far as it will go? If it initially boosts to only 14.5 and then creeps to 20.3 PSI...then it is not preloaded enough.

By, "as far as it will go.." do you mean that the externally threaded tip of the actuator rod has bottomed out inside the internally threaded turnbuckle? You are probably going to have to carefully cut 3/8" off the threaded tip of the actuator rod with a hacksaw. If you can only preload it to 14.5 PSI then the actuator rod is too long. Also, you'll want to do away with the backup nut that secures the turnbuckle.

Incidentally what is the peak boost target that you are trying to reach?

 

It is currently screwed down all the way to the backing nut. It held 14.5psi no problem before I figured the creep that was happening as the revs increased was due to having less travel in the actuator rod and the flapper not being able to open enough to relieve sufficient pressure to hold the boost stable. So I in fact need more preload??

Target is 28psi but I will be using an EBC. The preload at this point is to just improve the boost response a little.

 

Hmmm. This situation is interesting. It seems a bit odd that you should be describing severe WG spring bind affecting the actuator movement at only 14.5 PSI of spring pressure. As a practical matter, just how could you verify that the creep is in fact due to bind anyway? You are merely assuming that the 3-4 PSI of boost creep is due to bind and incomplete opening of the flapper valve, right? WG bind may seem like a logical explanation to you. But, I doubt that you are actually experiencing bind at only 14.5 PSI of spring pressure.

I have helped out peeps set up these same FP HD 18 PSI actuators for 27-28 PSI of preload. At the time, these guys were running their 16G's @ 30-32 PSI of peak boost on meth. AFAIK, they experienced no WG bind at those elevated preload levels.

I know for a fact that SpecOps Mikey is or was running relatively high levels of preload on that same actuator fitted to his Black. I would guess that Mikey is running at least 24-26 PSI of preload with no reported bind. I have personally preloaded the same actuator on my OS Green to levels of 23-24 PSI of preload when I ran 27.5 PSI peak. I never experienced WG bind at these levels of preload.

Now, these actuators do exhibit a characteristic boost spike that usually happens at somewhere between 18-22 PSI of boost pressure. So, as a result, most guys try to preload them to levels under or over that range just to keep out of that "spike zone". That is, they are not so great at controlling peak boost at between 18-21 PSI because they exhibit this characteristic built-in tendency to spike within that boost range. So if you were to try and set peak boost at 20 PSI for example then the actuator will spike it up to 22-23 PSI on its own.

I was wondering if you would be so kind as to post up your complete list of power modifications so that we can get a total idea of your setup. Especially, what is your post turbine housing exhaust system(elbow, O2 housing, DP diameter, test pipe, back exhaust etc.). Is the turbine housing on your Green ported or unported?

 

Yeah the wastegate bind is purely an assumption on my part by the fact that it shoots up to 14.5psi and the pauses momentarily before climbing to a touch over 20. The flapper still has about 10mm of movement in the arm.

Mod wise I have GSC S1 cams and ported manifold with invidia 3" dump, 3 inch custom down pipe, mil spec cat, 3" cat back all the way through. Turbo is not ported.

At stock pre load the spring was barely applying pressure to the flapper. The movement range has now been almost cut in half. I do understand what you saying though it may need just a touch more to get over that 14.5psi hump. Like I said I will be using an EBC for a peak boost of about 28psi so really my goal here is to maximise my boost response while having a stable gate pressure so my boost controller can control the boost effectively. (the HKS EVC asks for gate pressure in its settings.)

 

FP has been known to send out the wrong wga before...in at least one case that I can recall. I dont know that any of their WGAs have any identifying marks/#s on them. The 18psi that came on my green doesn't start to open til 20-21psi...preloaded the way it came from FP, I didn't adjust it at all. I can't remember the specifics of the case I referred to above, but the end of the story was FP sent him the wrong wga with a turbo he bought...but he had to send it back to them in order for them to determine what was going on.

 

My guess is that you actually have very little spring pressure as currently setup.

Increasing spring pressure(preload) will keep the flapper valve on its turbine housing seat longer, directing the entire exhaust flow axially straight through the scroll and past the blade tips by blocking off the tangential bleed through the bypass port. Ergo, all else remaining equal, you will get noticeably better turbo response and spool as the shaft will maintain rotational momentum and thus shaft speed.

 

Are you taking the boost reference for your EBC off the j-pipe nipple or did you "T" into the DV/IM line? I know very little about EBC's so I am guessing that they reference the same as a MBC from either of the two above sources.

 

The FP 18 PSI HD actuator actually likes to be preloaded at levels above 22 PSI of spring pressure. So, I would suggest that you remove the backup nut to give the turnbuckle a bit more range of adjustment and that we tighten it down a bit.

For levels of preload below the 19-21 PSI range, the stock actuator is actually the prime ticket. If you want to run the 18 pounder then you gotta setup preload properly.

 

As a practical matter, my advice would be to remove the backup nut and crank the turnbuckle down all the way until the tip of the actuator rod bottoms out internally....just for starters.

Since you intend to run a 30-plus PSI peak then you will want to run at least 24 PSI of preloaded spring pressure(probably more).

I think that you are going to have to cut a bit off the tip of the actuator rod to achieve that level of spring pressure though. But first, remove the backup nut and run the turnbuckle down all the way.

Now, keep in mind that a 18 pounder can be made to work well up to about 27 PSI of preloaded spring pressure. This is why I don't think the it is binding due to too short of an overall actuator rod length. It should work fine at the low levels of preload that you have it adjusted to.

But, this begs the question of why if you are gonna be running peak levels of over 30 PSI did you not just get the 25 pounder instead.

EDIT: I recognize it as largely my own fault that sparky has come to be considered by many, as being not much more than a cheap, actuator **** on these forums.

 

The intended boost range is more like 25-28psi depending on power output due to my stock motor. The reason for the 18psi actuator was boost creep issues with only running 2-3psi above the rated pressure. I feel 22psi of preload would be optimal here so I will try giving it some more tension and see what happens.