Boost cut

Hi guys im not very familiar with boost cut :facepalm: at what boost does it kick in? is it possible to remove this safety feature?

Safety feature - Remove it.

I sense much win.

Seriously though, it's not boost related - it is flow related. It comes into effect as soon as your MAF reaches its limit. For the CA, the MAF and injectors max out very close to each other. If you disable it, you will boost more but the MAF will not read further. This will blow your motor due to running lean.

You cannot disable it, but you can set it unrealistically high with NIStune (wouldn't recommend it, though - since you can just scale it along with you fuel and timing maps). Otherwise you will have to consider another management.

I'm not sure if our version even has a boost cut. Who has ever hit it?

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Daniel wrote:

I'm not sure if our version even has a boost cut. Who has ever hit it?

It does. IIRC a T28 will hit it at 0.8 bar or something, but not 100% sure.

little box with 3 vac lines on the left side of the engine bay. over boosting it pulls back on the FPR causing the motor to run lean.

It can be bypassed by connecting the FPR straight to the manifold but leaving the unit connected to the harness.

Not really a boost cut just a simple way to stop over boosting. Maxing the AFM out is something different.

rat wrote:

little box with 3 vac lines on the left side of the engine bay. over boosting it pulls back on the FPR causing the motor to run lean.

It can be bypassed by connecting the FPR straight to the manifold but leaving the unit connected to the harness.

Not really a boost cut just a simple way to stop over boosting. Maxing the AFM out is something different.

True, but boost cut is there to stop possibly maxing out MAF. The issue is you run past the limit of the stock fuel map.

From the NIStune mapping guide:

kwl thanks guys wont be removing that anytime soon

I should add to this thread to complete the answer that Rat is 100% correct in how the ECU implements "Boost Cut". It effectively just cuts fuel supply.

Ive bypassed my boost cut without any issues, my car is stock standard though, i connected my FPR directly to the intake manifold and all the other vacuum lines running to the boost cut solenoid i simply blocked off, neatens up things alot and my car runs 101percent, spark plugs are looking good and motor runs without any hickups till about 6500rpm, never limited my car though. Ive heard from some guys aswell that the boost cut solenoid can sometimes go faulty or get stuck and cause feuling issues as maybe you FPR is opening when it shoudnt etc, so i thought might aswell just connect it straight to manifold, but keep the boost cut plug on the solenoid to prevent any ECU fault codes.

can that boost cut solinoid be used to adjust boost?

SonOfAnarchy ZA wrote:

can that boost cut solinoid be used to adjust boost?

yes if you can get something to manage it, my perfect power used it to manage my boost, eventually the solenoid got stuck and I replaced it with a VW boost control vavlve

Best thing would be to get an electronic boost controller.

rat wrote:

Best thing would be to get an electronic boost controller.

best thing would be to have the ecu control the solenoid so that your AFR stays on par when adjusting the boost 🙂

At the end of the day the electronic boost controller "kit" is just a controller and a solenoid, same as what that thingy is, a solenoid. Although the function is slightly different.