Not making expected boost

[99BlackW68]

I had my powerdyne bearings go bad on me about a month ago, and when that happened there was play in the impellar shaft and it contacted the housing making that impellar useless. so i bought the upgraded impellar from 928 motorsports which is supposed to make more boost at equal pulley sizes. before this happened i was seeing 7psi, but after we rebuilt it with the new pulley shimmed out as well, im only seeing 5.5psi, which doesnt make sense. i should be seeing more than 7 because of the new impellar and shimming it out. so...any ideas as to why this is happening?

[Shodown]

Re: Not making expected boost

Why did you make 2 threads about this problem?

LOL

[99BlackW68]

Re: Not making expected boost

cause they were different topics with different questions.

thanks for your help

[Shodown]

Re: Not making expected boost

Seems like the same problem...not enough boost and you want to know why, correct?

There is a 9 psi pulley for sale in the For Sale section.

Climate can affect boost as well. Hot/humid weather will cause a drop in boost cuz the the air is less dense with oxygen.

[99BlackW68]

Re: Not making expected boost

true, true.

this is also true but i should be somewhere around 9psi, but im below 6, climate cant make that much of a difference.

[Shodown]

Re: Not making expected boost

Are all of you clamps/couplers solid? No boost or vacuum leaks anywhere?

[99BlackW68]

Re: Not making expected boost

there are no leaks due to loose clamps or couplers.

thanks for throwin out possibilities. any others?

[Shodown]

Re: Not making expected boost

Do you have a vac gauge in the car or is it just a boost gauge?

[vr4gasm]

Re: Not making expected boost

i would call 928 and see what they have to say..

[99BlackW68]

Re: Not making expected boost

the gauge shows vacuum and boost.

[Shodown]

Re: Not making expected boost

i would call 928 and see what they have to say..

Yup, me too.

[redfbird99]

Re: Not making expected boost

sounds like you wasted a bunch of cash on a worthless "special" impeller. Hope you can get this sorted out..

[99BlackW68]

Re: Not making expected boost

nah, it was a vacuum leak. not like it matters though, still sellin the kit. I want to push up to 15psi intercooled so its turbo time.

and no that impeller wasn't a waste. even with the boost leak i could still feel the boost coming on much sooner in the power band. well...i am selling it now so i guess it was a waste haha, oh well, whoever buys it lucks out i guess :D

[Mighty Thor]

Re: Not making expected boost

You beat me to it. I was going to say that you might have a vac leak.

I had a vac leak on my boost gauge before and it made my rpm flactuate at idle. I couldn't find the leak till I remembered a couple of weeks later that boost gauge operates on vac. That fixed my problem.

I'm planning on getting this impeller someday. But It is over priced in my opinion.

[redfbird99]

Re: Not making expected boost

You beat me to it. I was going to say that you might have a vac leak.

I had a vac leak on my boost gauge before and it made my rpm flactuate at idle. I couldn't find the leak till I remembered a couple of weeks later that boost gauge operates on vac. That fixed my problem.

I'm planning on getting this impeller someday. But It is over priced in my opinion.

I agree, I dont see how it even helps much unless my powerdyne came with the improved impeller already, i was supposed to have a 5-6 psi pulley but saw 7 quite often with my kit, and it would definately shoot up boost quickly in the powerband.