grimesland

Hello group, I am new here and am having an issue with the boost pressure with the powerdyne SC I just installed on my 88 gt conv that has been converted to Mass Air. I can only seem to get around 2 lbs of boost. I have bypassed (plugged) the bypass valve and am fairly confident on the crank to SC belt tension. How tight is tight?? Too tight?? I am getting a whine from the unit so I have confidence the internal belt is ok. I have not changed the plugs yet but will today. With no more boost than I am seeing I doubt blowing out the plugs is an issue at this point. : / 93 octane. FMU, Boost gauge, fuel pressure gauge, etc. Car has headers, and flowmasters. Cats are still up there. Just doesn't have near the 6 lbs of advertised boost nor any performance improvement to really even mention. I like the whine though. lol

turbostang21

you should barely be able to twist the belt or move it. did you by the powerdyne new? why plug the bpv...just to make sure it wasn't leaking? where did you install the bung for the boost pressure gauge? how does it feel driving? that should do it for now...

btw very nice vert

grimesland

No, I bought the unit off the bay. 1,150+ shipping. "Yes, I plugged the bpv to insure it wasn't leaking. I tied the fmu, boost gauge and bypass valve to the (i think) brake assy nipple on the tree on the firewall. It was just plugged. My best friend has a supercharged convertible (87)and that is where he had his tied in. I didn't however feel his belt for tension as I didn't make it that far in one day and he lives several hours away. I keep hearing belt tension but that thing sure seems tight. As far as driving it has a very small improvement. When I am running around 3,000 and roll on the throttle in 3rd it will boost about 2 lbs. When I slam it to the floor at a stand still I barely will register + on the vac/boost gauge. Sure seems like slippage or leakage. : / Thanks for your time, Jeff

BTW nice stang to U as well

threeg502

Hey. I just thought of something. Your internal belt has cogged teeth right? Well, what if the teeth were stripped off. You might make some boost but it would be limited right? When you slam it from a stop the impeller has to accelerate quickly AND try to build boost. Seems like someting to think about.

grimesland

Another weekend of diagnostics. lol Installed the colder plugs gapped at .035. Reset the timing to around 8 degrees btdc. Completely bypassed and plugged off the blow off valve. Re-checked every clamp, hose, etc. Blew into my gauge line and saw almost 3 lbs. My freakin cheeks still feel like I blew up 50 balloons for a birthday party. : / I contacted the seller of the unit, since it was used, and I he told me it had about 300 miles on rebuilt head unit, with kevlar belt and ceramic bearings. If it is a lie, he told it. ??
One thing I did think of as a possible variable, the guy who sold it to me also mentioned the kit had a aftermarket ASP one piece crank over/under drive pulley. I am very confident in the unit and in the installation. I am leaning more toward calculating the ratio of the pulleys for my application and change accordingly. Something like (RPM) shift point X SC crank drive pulley dia divided by SC head drive pulley dia equaling something like a 2 to one ratio??? ex 6,000 X 6 inch crank pulley divided by 3 inch head pulley= 12,000rpm?
Does that sound correct or should my charger RPM goal be higher. Since I am seeing 2-3 lbs of boost, I am thinking of trying a 2.87 sc pulley, which would be estimated 4lb increase putting me at (hopefully) around 6-7 lbs.... Thanks, Jeff [sm=dontgetit.gif]

threeg502

Can you get the correct pulley diameter specs from powerdyne? Also
I may have a quick way to check those teeth on your internal belt. Remove the intake pipe from the supercharger. Loosen your belt till theres lots of slack. Then simply hold the impeller with one hand(or fingers) and try to slip the inner belt by turning the supercharger pulley with your other hand. Don't go too crazy of course ! If it slips at all that just has to be the problem. If not then I'll get off your case about it at least! I hope I've been some help.

threeg502

One other thing. With the 6" pulley driving the 3" pulley you have a 1 to 2 ratio. The 6" driving the 2.87" you have a 1 to 2.09 ratio. Thats not even a five percent increase, right?
I don't think that would give you the 4 psi increase you need. George

dsblk93gt

With the 9lb kit I had, I would be getting 3lbs by at least 3500 if I remember correct and peaked at about 7lbs by 5500rpm's. I think it has to be belt slip. I can't imagine what else it is. You should feel a good increase in power though..even with like 5lbs..

BTW..it should have a 6.5" crank pulley or 6.75 I think with the kit and a 2.93" pulley on the SC if it is a 9lb kit.