Hey everyone I just got my FP Red on last night that has a 25psi wga on it. I drove around for about 100 miles then did a pull on it and the turbo was putting out 25psi, all was good. well I pulled over and started turning in my boost controller to get back to 29psi, thats what it was at with my old red before I blew it up, and the boost psi dropped to 16 in first and 21 in second. I pulled over again and turned the controller in more with no change. I finally ended up cranking the boost controller way up and got to 21psi 1st 23 in 2nd and 28 in third. I have no idea why it is boosting so much different in other gears and dont really know where to check. Any advice is greatly appreciated, thanks.

 

Did a boost leak down test, no leaks, swapped lines going to the boost controller to make sure it was correct, no change is boost. I am thinking my wastegate isnt closing all the way?

 

Is your new Red configured identical to your old Red? Do they both have the same compressor cover(73mm, or, 84mm)? Did your old Red have the 25# actuator like the new one does?

 

Also, if the wastegate is preloaded differently on each Red, then the rate of spool and peakboost levels will be different even if the MBC setting is unchanged.

 

If you had the FP 18# actuator before and now you have the 25# unit and each is preloaded differently then you can get way different rates of spool and peakboost levels than you'd expect...even with the same turbo.

I think that since boost level is so low in the lower gears that you don't have the 25# actuator preloaded enough.

You are gonna have to preload the 25# unit to at least 24-25# for your peak boost level. You'll need to play around with the preload setting on the actuator. Ideally you want preload set at about 3# under your peak boost level.

 

In your particular case since you are aiming at a 29# peak boost target level in top gear, then you'll want to set WG preload(WG spring pressure) to 26-27#.

So, how do you go about setting up WG spring pressure to x desired level if you have an MBC in the control loop? The very first thing to do is take the MBC out of the equation. Basically, there are two ways to accomplish this.

The better way is to run a length of vacuum hose directly from the compressor housing discharge nipple to the nipple on the WGA cannister making sure to plug any open hose ends in your boost/vacuum hose assembly with golf tees and hose clamps.

The second, "Easyman's" way to remove your MBC from the loop is to leave the MBC connected but simply turn the MBC's knob out counterclockwise to its lowest(softest) possible setting.

Once you have disabled your MBC then take the car out for a WOT run in 4th gear. Check the peak boost reading on your boost gauge. I don't think that boost will even get up to 22-23# if set up in this manner. At any rate note the boost level.

Depending on what boost reading you see, then you start increasing spring pressure by rotating the turnbuckle on the end of the actuator rod inward, clockwise. Do a turn or two and hook it back up and go for a WOT run. Boost should increase a PSI or two for each complete 360* rotation of the turnbuckle.

Continue this adjustment process until you get spring pressure up to around 25-27#. Then insert the cotter pin as you are done with that. Reconnect your MBC. Now the final 3# to get your boost level up to the desired 29# you can dial in with your MBC knob.

 

I played with the pre load on it and got it pretty figured out. I had a 60mm red with a 18lb wga before. Now its the 84mm with a 25lb. With the mbc off, its hitting 27-28lbs 1st and 2nd and 30 in third so I think I got it figured out, thanks for all the advice.

 

28-30 PSI in third with the MBC turned to full soft is kinda high isn't it? This would mean that it will be a couple PSI higher in 4th and 5th gear pulls. You probably want to turn the turnbuckle out counterclockwise two complete turns.

How cold are the ambient air temps while you are doing this boost testing anyway? You'll want to leave some safety margin so that you don't overboost when the weather gets colder. When ouside air temps drop then your boost will creep up.

 

Yeah I had to turn it down, did a 5th gear pull and saw 34lbs. But now im at 21lbs 1st, 23lbs 2nd, 26lbs 3rd and 30 in 4th. I dont understand how the boost can swing this much through different gears? When I had my smaller fp red I am pretty sure it held consistent boost through all the gears.

 

Well boost will always be lower in 1st and 2nd and you shouldn't worry about that.

But boost should be similar in 3rd and 4th, with 4th being a lil higher.

Which type of MBC are you using?