I agree with the above. This confirms that 30# and above is doable on the VIII turbo/9.8. Probably the OP's IX DV needs further crushing. But, ultimately I think that he'll find that his inability to boost any higher can be traced back to a lack of sufficient WG preload.

Assuming that the OP's turbo is configured with the 9.8cm vs. a 10.5cm turbine housing then the theory involving too little preload makes more sense to me. Why?:

Given the same motor flowing the same exhaust volume at the same velocity and the same EGT at the the outlet location of the exhaust manifold's collector flange, then exhaust pressure measured at the turbine housing's inlet will be higher if the turbo in question is fitted with a 9.8 vs. a 10.5cm housing.

Since the wategate bypass port initiates and is sourced directly at the turbine inlet then an increase in exhaust pressure at the turbine inlet causes a proportional pressure increase in the wastegate bypass port. This pressure increase in the bypass port directly raises the seat pressure acting on the face of the wastegate puck lifting it off its seat sooner and higher with the internally more reduced 9.8 housing.

Moral of story is that the smaller 9.8 housing requires higher levels of wastegate spring pressure(preload) to keep the flapper valve on its seat. The OP's flapper valve is reaching full open travel sooner and at lower seat pressures with the 9.8 housing.

As a practical matter the OP needs to upgrade his actuator to at least an 18# unit preferably the FP 25 pounder. At the very minimum he needs to preload the hell out of his stock WGA. Does FP even make a 25 # WGA for the VIII turbo?

 

Have fun spiking and falling off hard, pushing hot air and killing the turbo you being a vendor means nothing. And spiking 30-35psi of hot air for 3 seconds is pretty lame. 20-25psi atleast you can hold it. I have a 9 turbo and 30psi is stupid unless on E85 and even then, for how fast it drops off it's not that great. If you want more turbo, buy a bigger one.

BTW a vendor that talks to people like they are retards doesn't look very professional now does it?

 

Idk where you get your info from. How many people do you see that run 20psi? Stock cars? Also even a 20-25psi spike you are still not holding that boost to redline, if you want to hold boost, buy a bigger turbo. All stock turbos will taper, any turbo pushed to its limit will taper. Also just to clarify, 30psi on a IX turbo is impossible without E85/race gas, not stupid.

I'm also not sure if you are aware, but taper is not always a bad thing, and your power curve doesn't always follow your boost curve. My stock turbo did fall off, just like every other stock turbo car but I made peak power at 7000-7200. A lot of your power/turbo taper comes from the cam you chose. A huge cams will make much more power in the higher rpms, but will induce taper sooner due to the increased VE of the motor. Yes, you are losing boost in higher rpms but increasing HP.

Here is a dyno of my personal DBB FP Black that holds the world record, that is a proven fact that boost taper means nothing if you know how to mod a car correctly.



You run a "3 sec" taper to raise the boost in higher rpms as the boost pressure takes time to bleed out of the wastegate, usually increasing HP. The short boost spike usually doesn't even hurt the turbo because you are usually not over the usuable shaft speed of said turbo. Now if the stock turbo had a 30psi spike and help 30psi to 7000 than that turbo would only last a few pulls if you are lucky.

Oh and btw no one was talking about running 30-35psi. We said 30-31psi max. Spark was just saying it is possible to run over 30psi in general. I used to run 35psi on my stock turbo trying to blow it up. It was crazy fast (loads of torque/doesn't really make anymore power per lbs over 30psi) and sounding like a supercharger as the chra was imploding.

Sorry for coming off that way, as you don't know me. I'm not unprofessional

 

The OP is wanting to run over 28#of boost. Plain and simple. That is what this thread is about. This is not The Mickey Mouse Club, or The Captain Kangaroo Show. This is the Engine/Turbo/Drivetrain section of EvolutionM.Net. Mikey is the bonafide record holder, dude...duh!

 

I have always admired the guys and gals that push the stock 16G turbo(both versions: VIII & IX) to the limit powerwise. But, that is a bit OT.

Back to the OP's problem. If he is wanting to go for 28-32 PSI on the stock VIII turbo he should first get a heavy duty actuator that is up to the task. His unpreloaded stock actuator is allowing the flapper to be blown full open at 26-28#. Even the FP 18 PSI unit is not good for spring pressure levels above 27 PSI. It will do the job in a pinch if you trim the actuator rod a bit though.

I think that he needs to crush his IX DV a bit more as well. Finally he should get himself a good MBC and did I mention that he should preload his actuator up to about 26-27#.

 

You crack me up spark.

Mikey

 

30 psi on a ix turbo on pump gas is not impossible. 30 psi on a small 8 turbo with a 10.5 housing and 93 is very much so possible and i have the logs and video to prove that. im tuned right now on 27 psi with an 8 turbo 10.5 housing and boost barely tapers... it will depend on setup. but to say 30 psi is impossible is stretching it. do i need to post said logs and video i took earlier this afternoon? i may add the said logs had 0 counts of knock all the way to 4600 rpms when i let out because of it hitting 30 psi.

not trying to say you donno what your talking about since alot of your post are very informative and you do know what your talking about most of the time, but that statement was very wrong unless im misreading.

 

Yes It's possible, but ill never tell anyone to run 30psi on pump, or tune a stock turbo car that way. I won't openly admit to something like that, its not safe practice for a shop. I can see it now, a thread on evom "Mikey tunes stock turbos to 30psi on pump gas"... I'll stay away from that. Lol but yes, A lot depends on the tune/setup. If the car has a large 3.8 Garrett or 4" and well modified you can get 29-30psi on 93oct. I personally don't like saying that you can do that because one band tank of gas on 30psi and your car will be done. To many people on the forum will see one guy trying to push 30psi, think they can do it and start cranking the mbc in hope of making more power and blowing the car. Just to risky if you want my honest opinion. Also if you run lower timing you can run higher boost, which will also keep the boost from tapering quite so bad but I don't like to tune cars that way. I prefer moderate timing and moderate boost. I don't think 30psi on 93 is the right answer on the stock turbo. No need to post your logs brother I believe you

Mikey

 

Yes It's possible, but ill never tell anyone to run 30psi on pump, or tune a stock turbo car that way. I won't openly admit to something like that, its not safe practice for a shop. I can see it now, a thread on evom "Mikey tunes stock turbos to 30psi on pump gas"... I'll stay away from that. Lol but yes, A lot depends on the tune/setup. If the car has a large 3.8 Garrett or 4" and well modified you can get 29-30psi on 93oct. I personally don't like saying that you can do that because one band tank of gas on 30psi and your car will be done. To many people on the forum will see one guy trying to push 30psi, think they can do it and start cranking the mbc in hope of making more power and blowing the car. Just to risky if you want my honest opinion. Also if you run lower timing you can run higher boost, which will also keep the boost from tapering quite so bad but I don't like to tune cars that way. I prefer moderate timing and moderate boost. I don't think 30psi on 93 is the right answer on the stock turbo. No need to post your logs brother I believe you

Mikey

 

Sort of. A boost leak won't produce the same result as air flowing at WOT. There is a pressure difference between the BPV and the manifold, where the vacuum/pressure line for the BPV is referenced.
When you're doing a leak test the pressure is more stabilized w/o the pressure drop. If that makes any sense.