So running no gate at all, all exhaust has to go through the turbine and it only makes 12psi ?

Is it 12psi steady or does it rise/fall with rpm ?

Any info on pre/post turbine pressure ?

 

Check hot side of turbo. Maybe a chipped blade or the hot side housing maybe cracked. I've seen the things go on unnoticed.

 

Boost stays steady. Also tried another gauge and get the same reading. No post or pre turbine readings.

 

check for exhaust leaks?

 

Are you positive your BOV isn't cracking open? I have a jgs 60 bov pre intercooler (eBay unit, think its the same as cxracing) I couldn't make more than 5psi and when on the dyno I could see it lifting. It was plumbed with bottom port to the turbo compressor, top port between the throttle body and intake. So I just unhooked the bottom port off the BOV, made 15psi on the dyno. Later put the stiffest spring combo in the WG with both ports connected, when I went to crank it up I couldn't get over 17, unhooked the bottom port again and bam, 23psi when I backed off. How is yours plumbed? Do you have the stiffest spring combo available in it?

 

Could it be the BOV somehow? Nothing would make perfectly linear boost better than the BOV breaking open at a certain psi. Super cool setup, keep us posted!

 

The BOV is a HKS unit he bought for it. Only has one port for reference.

 

Did you do a measurement pre intercooler to see what boost is?

 

No. I should but I got a good bit of time in it already. Its more of a favor to him cause im not charging him much. We have several more things that could be checked. For one he has the comp beehive springs in there which are not a dual spring. Not sure if seat pressure is enough to keep them working properly.

 

Very unusual to see a steady boost level with no means of control at all.

Try blocking off or removing the BOV completely, same as what you did with the w/g

Does it sound like there are any boost leaks etc ?

 

I'd make a boost leak check rig and pressurise the cold side with shop air. Will tell you right away if it's the bov and it's always found several other small leaks on my setups.

If it's not the coldside, the hotside could have something obstructing it? Did you use any flex couplers?

 

Valve springs usually limit rpm and the motor just levels off, its just low on boost but rpm climbs steadily correct? If your BOV only has one reference I would imagine its on the top of the diaphragm and is referenced past the throttle body. When on the dyno cap off that line and regulate an air compressor down to like 20psi and hook it to the BOV and see if it changes.

 

In my personal experience I was still able to make as much boost as I wanted to with worn valve springs. I had patriot doubles with around 50k miles on them and they worked great around 12-13psi....once I got around 15psi the car just sounded like it was misfiring really bad in boost.

You could hear and feel it bad. Changed the valve springs and it went away.

Like I said it would make all the boost I told it to with the extremely worn valve springs it just didn't run right.

 

4.8 S366 turbo map Ran this. Even at 12 psi that turbo is pretty close to being done. Should still be able to get more out of the midrange though.

 

Well we have the culprit. The turbo was bad. Couple bov failures and it messed thrust bearing up bad. Had major shaft play. Here are some pics Jose sent me from the tear down. Should have it back together by the end of the weekend or first of next week. Relocating bov to right after the turbo since that's the highest pressure point.

 

Bad BOV or not, it shouldn't take out the thrust like that in such a shot time IMO.

I never ran a BOV on my 3.8 setups. Ran 28+lbs of boost on many different turbos without one thrust issue in 8+ years. (Auto trans only) Not saying a BOV isn't a good idea, just that you may want to take a look at your supply/drain setup too.

 

-4 unrestricted feed -12 drain. Plenty of fall on the drain side as well.

 

So got the turbo back, relocated bov to right after the turbo, got everything hooked back up and went for a drive. Turbo responds night and day compared to before. But hitting the top at 12psi. I believe the power output of this unit has been reached on this setup. Est around 600 rwhp now. Not traction at all 1st thru 3rd. 4th is questionable sometimes. Car feels good though now. He should be happy with this. More power is just gonna take better bigger parts lol. Everything should be good to go for a long time now. Here's a 3rd gear hit down hill to help traction lol. Notice afrs are pig rich but it's safe.



250 rwhp gain isn't to bad considering this little 4.8 made 352rwhp on 0 psi when first pull was made.

New cold piping and 2/3 turbo.

 

 

In for track results! Why you say this turbo is done on 12psi? Is it pumping lot of heat out? I went 7.39 @ 100 mph with this turbo leaving off idle, 10psi, 15* timing, on a 4.3l v6. Next pass hooked up the boost controller and it pegged my 20psi gauge and found other issues so I'm down til spring. I'm hoping to make it to 22psi on my motor with this unit lol.

I talked to you on fb the other week Stephen on nigels post btw.