Ive got a Greddy Profec B Spec2 boost controller and was just wondering a few things.

How accurate is the boost controller reading actual boost? Its just that Ive seen lots of cars with both boost controllers and boost gauges, wouldnt the boost controller show you what you are boosting?

Also with the set % values, 0% is just wastegate level, what then does 100% mean? (guessing it doesnt open the watsegate at all and allows turbo to spool upto whatever it can?)

Ive got the set % at 88% and am seeing around 13psi. How come if I move the set values up and down by 5% I am not seeing any change of peak boost?

Cheers

Mark

 

not sure how accurate it is...i used it as my boost gauge as well since i didn't want to run a traditional style gauge. I think it probably comes down to preference mostly. Some like the analog, some like digital.

yes 100% is like you have no wastegate, so you will boost to your turbochargers limit.

Your peak boost isn't only dependent on your Set value. With set at 88% you have to also adjust set gain (start boost) and gain. As a general rule of thumb, start boost should be a couple psi below your desired boost level. For example if you have your start boost set to 11psi, the controller will hold your wastegate completely shut until 11psi, once it hits 11, it'll start to open and shoot for your desired boost level.

So if your desired boost level is 13psi, and your set boost is at 11psi, after it hits 11psi, it'll try to regulate at 13psi. This is why if your start boost is too close to your Set % (desired boost), you will overboost. Like if your start boost is 12.5psi and your set % is 13psi, your wastegate will be shut until 12.5 but it won't have enough time to regulate to 13psi, so it'll likely overboost for a moment.

Alternatively, if your start boost is too far from your set %, say 3psi start boost and 13psi set %, then you might not hit 13psi at all because you might be bleeding off boost way before then. So to tune start boost, figure out how much boost you want to run, then set start boost at a couple psi below desired boost. Adjust your set boost up or down depending if you overboost or underboost.

Gain smoothens out the boost response.

That's the long answer.

Short answers = troubleshooting section in the back of the manual =P

 

Thanks Chris! Answered all my questions, did read the manual but found it a bit confusing. They should put your explaination in the back lol Currently I have my set at 88% and my set gain (start boost at 72). Might up set gain a little bit.

 

yeah the manual is a bit confusing...especially when the manual says set boost, but the controller shows set gain!! let me know if i can answer any other questions for you. =)

 

Generally speaking it is only safe to boost to twice the amount of pounds that the wastegate spring is i.e. 8# spring means the boost contoller is accurate to 16ish#'s.

The profec is about as user friendly as it gets. you will have a wastegate stiing = off
lo setting = whatever mine is 12
hi setting = whatever mine is 18