Asarus

Hi guys,

I need your feedback. Who uses a Guru modified wastegate ?

I experience some overboost problem since i mounted this wastegate on my car. My normal boost level is 1.2 bar. With the guru wastegate i have a boost peak at 1.5 bar (max of my gauge) during 1 or 2 seconds and then it stabilizes at the correct boost (1.2).

I tried to add the "Accuboost" from Boost Sciences (the "successor" of the reliaboost). I connected between the banjo bolt and the 3 way valve as indicated. It's worse ! With this item installed, my boost stays at 1.5 bar (or more, don't know, because my gauge is at the maximum). I just did very short tests as i really don't want to blow off my engine. I set up the accuboost in 4 different position (max, min and intermediates) and same problem.

I didn't connect the accuboost directly from the banjo to the wastegate because i need to lift the car for that, and i need to take an appointment with someone owning a car lifter (not so easy)

It looks like the wastegate spring is too hard to be opened easily and need an important boost level before to open. Maybe an other spring (progressive ?) would do the trick ?

My DME/KLR are my stock genuine french Cup chips (305 bhp)

So to make it simple :

* standard shimmed wastegate : 1.2 bar and a progressive drop down to 0.8 bar to redline
* guru wastegate : peak of 1.5 bar and then 1.2 bar, and 1.0/1.1 bar to redline (correct except for this ~#! peak)
* guru wastegate + accuboost (banjo/3-way) : 1.5 bar (or more) always

For american people, here are the quick conversions :
1.5 bar ~= 22 psi
1.2 bar ~= 17 psi
1.0 bar ~= 14.5 psi

shortyboy

well,i have the guru wastegate and mine holds 15psi to redline(might drop 1 or 2 psi).i also have a LBE(boost controller),guru chips,3bar fpr, guru wg and test pipe.i have my boost control connected straight to the wastegate,the previous owner had this setup.you might have a bad vaccum leak somewhere or it could be the cycling valve,alot of people take it out and go directly.my advice is to get a real boost gauge,factory ones arent so acurate all the time...hope this helps

Asarus

Thanks Shortyboy but :

* i have a real boost gauge and also an afm. As you say the factory boost gauge is not so accurate and anyway it's not able to give you the boost level above 1.0 bar (meaning 2.0 bar total, with the ambiant pressure)

* my car works well with my stock setup, that means (as this a genuine Cup car) : 3 bar fpr, cup chips, cold spark plugs, almost free exhaust

* as far as i know (and i check everything often), i have no bad vaccum leak... maybe my cycling valve is the problem but i should experience the same behavior with my "normal" wastegate if that was the case, shouldn't i ?

If i bypass the cycling valve and go directly from the banjo bolt to the wastegate, is that a sufficient test to know if my cycling valve is correct ?

Jake951

The 3 way valve is the cycling valve, I presume. A number of people, including myself, have found that the cycling valve presents a partial obstruction which reduces the pressure that is passed to the wastegate. If you bypass the cycling valve (do a search in the archives here for a detailed description of how to do this), you will get more pressure to the wastegate, which should eliminate the overboost.

macnewma

Yes, the cycling valve does slow down the air. I have noticed that with my Reliaboost inline with the cycling valve, I have the reliaboost at its lowest limit to produce only 15psi of boost. It should be producing less than that, but the cycling valve slows it down along with the reliaboost.

I have yet to remove my CV, as I am waiting for vacuum hose and some other parts, including a Tial WG. But from what I have heard, you will definitely want to remove the CV from inline with an upgraded WG. You should check with Danno at Guru to see what pressure the spring is rated to.

If your WG is rated at about 1 bar and your CV is slowing down the air, the CV is effectively raising the boost by itself.

Also, what is the Accuboost? I have the Reliaboost II, but I haven't heard of the Accuboost.

Max

Sami951

Try bypassing the cycling valve, ie. just put a straight line from accuboost to the wastegate. No need to remove all the stuff in order to try it out... Tommy's car was overboosting with shimmed stock wg and reliaboost, this sorted it out.

Asarus

Thanks

I will try this and if it solves my pb, i will change my cycling valve..

pk951

I have a tial WG, and before i installed my maunal boost controler. I was just useing the 08 spring off the WG, which is 11lbs of boost. If i ran this configure ration, i would get 11lbs of boost. but when used with CV i was getting 20lbs of boost.So it seem's that CV is made to work with stock set up not 15psi of boost. By pass the CV.

Asarus

Ok, i will bypass the CV to test but with my stock configuration (17 psi because Cup car) and the CV enabled, i had no pb...
The pb appeared since i changed the wastegate to put the Guru one (i didn't say this is a bad WG, i just say this is the source of my current pb in my current configuration). So maybe the CV "doesn't like" this WG, but i can confirm that my CV works well with the 17 psi of boost

macnewma

Right, your stock WG has a spring of like .3 bar, can't remember exactly. So when you combine that with the added boost (blocked air) from the CV, it comes out to stock. The Guru WG probably has a much stronger spring, like .8-1.0 bar, so when you combine it with the boost that the CV adds, it comes out higher.

You must remove the CV.

Max

MySwiss

pk951. You are running a .6bar (8.7psi) 35mm Tial,and not a .8 bar(11.6psi).So what you experienced is actually worse.

The best and safest solution,is to simply bypass the cv,and either use the wastegate spring pressure to contro,boost,or use MBC or EBC.

Good luck

Asarus

It sounds pretty logical when explained like that

I'm gonna try in the next days (i have a track event on the 24th of January and must fix this before) and keep you informed.

BTW, i have a brand new CV (for my street 951) so i can replace it to begin, and test if that changes something.. before to bypass it completely

Sami951

You don't need to replace the CV, it's probably not broken, it's just that it is designed to work with the stock wastegate like Max said... the guru wg needs more pressure to open, so either you need to bypass the cv completely, or get a chip that has a different cv controlling pattern (apparently this is a tricky thing to do as it's encrypted - most tuner chips leave the pattern alone) (I would assume the cup car chip gives more boost than the normal street car chip.. no?)

Asarus

This is right, i have 17psi stock with my Cup chips and the stock CV (not bypassed), and this is why i don't really understand when you say the CV is not designed to work with more than the stock "street" boost, because it works correctly with my car...

I'm ok to bypass the CV if this is the solution, no pb... but my pb is not due to my chips giving too much boost for the CV, as that works well with the "stock" wastegate. The problem is only with the upgraded wastegate with a harder spring...

macnewma

You could try replacing the CV with a new one, but you should have the same problem with a new one, maybe slightly lessened.

The CV ends up working in a similar way a jetted banjo bolt works. It basically blocks/slows the flow of air by design. It is not a defect of the unit.

Bypassing the CV also leaves you with one less part to introduce a vacuum leak.

Good luck and let us know how it goes.

Max