Need boost help!!!

KL-Motor-Sports · 11-1-09, 13:57

Ok I bought this 1st gen mx6 from stealth and after I put on the Greddy Profec B I blew the turbo after it was spiking to 20 plus lbs. So I bought 2 stock Vj11 turbos from a guy who was building an F2T. The 1st turbo was used with zero shaft play and the 2nd was a rebuilt turbo that wasnt installed. So I put on the used turbo 1st and again blew it up using the ProfecB. So I put on the rebuild and took the profec b off and put in a Forged MBC and now the car wont boost passed 10lbs I even took the mbc off and it gos to 10lbs? So i put the mbc back on turned all the way up and it would spike to 15lbs put fall back to 10 rather fast.

My mods:
1. 2.5 dp and mandral bent 2.5 exhuast no muffler
2. Probintaor chip
3. HKS SSQ bov
4. K&N filter

Here is what iv done.

1. Checked for boost leaks. There is none.
2. Added a spring to the wg and this did work kinda.. it held boost when i was in 1st thru 4th but if i just put it in 3rd or 4th it would spike like crazy!
3. Shorted the lines to the MBC
4. Checked for turbo mani lecks. There are none.

now when I had the xsturbo MBC on before it would spike to 15 then fall back to 10. I took it to the track like this and I ran 14.6 @ 93 now I know thats not bad but it wasnt holding 15lbs it was more like 10. the thing is my 8th mile was a 9.3! thast a easy bottom 14sec pass so there is an issue with boost.

Now I dont know why its boosting passed 7lbs when put back to stock but either there is a 10lb spring or the 2.5 custom DP is making it overboost.

ANY IDEAS!!

KL-Motor-Sports · 11-1-09, 17:32

15 views and no one can help??

**ademan** · 11-1-09, 18:37

Quote:

Originally Posted by KL-Motor-Sports

Ok I bought this 1st gen mx6 from stealth and after I put on the Greddy Profec B I blew the turbo after it was spiking to 20 plus lbs. So I bought 2 stock Vj11 turbos from a guy who was building an F2T. The 1st turbo was used with zero shaft play and the 2nd was a rebuilt turbo that wasnt installed. So I put on the used turbo 1st and again blew it up using the ProfecB. So I put on the rebuild and took the profec b off and put in a Forged MBC and now the car wont boost passed 10lbs I even took the mbc off and it gos to 10lbs? So i put the mbc back on turned all the way up and it would spike to 15lbs put fall back to 10 rather fast.

My mods:
1. 2.5 dp and mandral bent 2.5 exhuast no muffler
2. Probintaor chip
3. HKS SSQ bov
4. K&N filter

Here is what iv done.

1. Checked for boost leaks. There is none.
2. Added a spring to the wg and this did work kinda.. it held boost when i was in 1st thru 4th but if i just put it in 3rd or 4th it would spike like crazy!
3. Shorted the lines to the MBC
4. Checked for turbo mani lecks. There are none.

now when I had the xsturbo MBC on before it would spike to 15 then fall back to 10. I took it to the track like this and I ran 14.6 @ 93 now I know thats not bad but it wasnt holding 15lbs it was more like 10. the thing is my 8th mile was a 9.3! thast a easy bottom 14sec pass so there is an issue with boost.

Now I dont know why its boosting passed 7lbs when put back to stock but either there is a 10lb spring or the 2.5 custom DP is making it overboost.

ANY IDEAS!!

it will boost past 7lb when you added exhaust in stock form. the stock boost is 7psi and 9psi on overboost, also when its colder out. adding intake and exhaust will get that 9-10psi on stock turbo since its less restricted exhaust.

now for your boost problem, are you sure you dont have a boost leak. use air compressor to check for leaks, make sure you dont have none.. you will be surprise sometime that you can find the leak while the car in vacuum only when its in pressure. they it leak causes the boost to spike or not get enough boost. trust me. i fixed goldylox and james car that way. it turn out to be the hose from the turbo to bypass valve.

other thing to consider again. if you dont have leak, the sstock plastic bypass valve are notorious for leaking expecially on high boost. check that make sure the diaghram is not blown and leaking your boost out

KL-Motor-Sports · 11-1-09, 19:04

Quote:

Originally Posted by ademan

it will boost past 7lb when you added exhaust in stock form. the stock boost is 7psi and 9psi on overboost, also when its colder out. adding intake and exhaust will get that 9-10psi on stock turbo since its less restricted exhaust.

now for your boost problem, are you sure you dont have a boost leak. use air compressor to check for leaks, make sure you dont have none.. you will be surprise sometime that you can find the leak while the car in vacuum only when its in pressure. they it leak causes the boost to spike or not get enough boost. trust me. i fixed goldylox and james car that way. it turn out to be the hose from the turbo to bypass valve.

other thing to consider again. if you dont have leak, the sstock plastic bypass valve are notorious for leaking expecially on high boost. check that make sure the diaghram is not blown and leaking your boost out

I knew you were going to be the 1st reply phil.

but to answer your ? yes I did do a compressor test on the system. I took a pvc end cap and put a valve in. this is what I did

So b/c the stock hose that comes off the turbo to the bov always cracks I found a perfect radiator hose that fits the turbo intlet and then the pipe for the bov. this is where i checked the system. like I said before there was a small leak where the fpr silinoid was but I fixed that now and still same issue.

**ademan** · 11-1-09, 20:21

Quote:

Originally Posted by KL-Motor-Sports

I knew you were going to be the 1st reply phil.

but to answer your ? yes I did do a compressor test on the system. I took a pvc end cap and put a valve in. this is what I did

So b/c the stock hose that comes off the turbo to the bov always cracks I found a perfect radiator hose that fits the turbo intlet and then the pipe for the bov. this is where i checked the system. like I said before there was a small leak where the fpr silinoid was but I fixed that now and still same issue.

see if the wastegate is functioning, disconnect the hose of wastegate and block it off, leave wastegate open, the boost should keep climbing

KL-Motor-Sports · 11-1-09, 20:41

Quote:

Originally Posted by ademan

see if the wastegate is functioning, disconnect the hose of wastegate and block it off, leave wastegate open, the boost should keep climbing

I kinda did that. I had the lines reversed on the Forg mbc and it went right to 20lbs.. Your saying I should take off the the wg vac line block it off and see if it cliams? Isnt what I did kinda the samething?

**Mazda Carnage** · 11-7-09, 19:05

Get a bleed style manual boost controller.
Run a hose straight from the turbo to the waste gate and T it half way, off the T run the bleed style boost controller and run the other end into the elbow after the air flow meter (T into the PCV hose).
The controller simply bleeds off air going to the waste gate, unlike all the ball /and spring types. You don't have a bleed style boost controller, they work the same in both directions.

To make the controller more efficient/sensitive, run smaller hose between the turbo and waste gate and bigger hose off the T to the controller....
Or insert 0.35mm welder tips in the waste gate hose at the turbo and at the waste-gate.

The reason ball and spring or one ball or any manual boost controller that sits inline with the waste gate line and uses a mechanical device to regulate (by holding back) the amount of pressure going to the waste gate Doesn't work well will the F2T and stock turbo is because unlike 90% of turbo applications with engines that breaths more as RPM's increase allowing a slow build of pressure at the boost controller which it can regulate and control as flow increases.
The F2 with it's low end power spools the tiny turbo instantly and the boost controller is resisting the maximum pressure it's set at and fighting to hold off the build up behind it possibly causing spikes, it looses and the ball or resisting piece is overwhelmed by pressure (Like folding a water hose for a few seconds then releasing it) and pined opened allowing all the pressure to reach the waste gate and boost falls.

It's funny but if you return everything on your car to stock and run the AC the boost controller might actually hold 15lbs, the more you make the engine flow the faster the boost controller will fail and boost will drop.

-------------------------------------

For even greater efficiency and convenience take the waste gates boost source from the charge pipe before the throttle body instead of from the turbo, this way the waste gate reacts to boost pressure after the inter-cooler and the boost controller no longer has to make up for the losses at the intercooler ....
For convenience run the boost controller in dash.

Use High quality, high temperature hose for the waste gate/ boost controller, avoid spikes past 16lbs on the stock turbo, that 20lbs you hit on your last turbo might have already shortened it's life.

Go to the junk yard and buy a T3 42/48 or bigger and run 11ps.