wilkinstan

Hello. I have owned my 86 951 since 2002 and now finally have the time to begin some minor modifications. I'm new to 951 tunintg so I know some people out there will have some good advice. I just got a MBC accuboost controller and have installed a VDO boost gauge to monitor boost pressure as I tune it. I don't want to boost past the cars stock boost of 12 PSI. So I've got a couple of questions regarding this which are-

1. Do I need to install an air fuel ratio gauge as well to safely tune this Manual Boost Controller since Im not going over stock boost? Or is the VDO boost pressure gauge adequate?

2. Are there really any advantages to using an MBC if not attempting to boost over stock boost? Sales Literature says that the MBC will stop premature boost pressure loss into the wastgate so that you can build boost faster. Can I do damage to the engine at stock boost levels using the MBC?

Sorry for all the questions but I am trying to learn as much as I can before beginning so that I can do things correctly. Thank You. - Stan

PorscheDoc

What other mods are you doing? You are not going to really gain anything by adding a MBC without doing any additional modifications. Most guys chip the car (Vitesse..hint hint), then delete the stock boost controller (Cycling valve), and run a manual boost controller like the accuboost, so you can run a level of boost as you desire, which when chipped is typically in the 14-15psi range which is quite safe with the correct chips.

edit:

So in summary, get a set of Vitesse Chips, and install your MBC. You will have a nice safe power increase.

35thSLP

I am running an accuboost without chips. I installed it after doing a vacuum hose replacement with a venturi tube and cycling valve delete. I do have better and quicker boost even though I am running stock chips at stock levels. I will be adding a chip soon. I think if nothing else it simplifies things under the hood and reduces the opportunity for vacuum leaks. just my .02 cents. I'll probably go with the chips from down under until I can swing the complete vitesse kit simply becuase of cost.

wilkinstan

Thanks for the good info. At some point I would like to put in a Lindsey Stage I or II MAF system with a 3'' exhaust but it may take me a while to get around to that. What exactly does the cycling valve delete accomplish? - If I don't do it is there still any use in installing the MBC? Thanks.

wilkinstan

I suppose I should have read the first reply more closely. I supose the stock cycling valve is keeping the car at stock boost levels - chips are required in order to tell the computer system how to properly mix air fuel ratio to deal with increased boost provided by an MBC?

Eyal 951

Your really not looking at much of a HP gain if you arent increasing boost.