It appears I'm having some blower issues not outputting the correct boost levels. I initially thought it was a coupler leak or wastegate failure, but have narrowed it down to the Novi unit. Issue is that when I hit ~10 psi the boost starts falling flat on its face as I pull more engine RPM. I ran a boost leak test and confirmed there are no coupler leaks. I'm also running a wastegate and suspected either that or the boost solenoid may be the culprit. To eliminate the WG and solenoid, I re-routed the hose so that it places positive boost pressure against the diaphragm to hold the WG valve shut. Also turned off the solenoid in Flashpro. Again, confirmed with my leak tester that it holds boost and it did. When I run the car to redline the failure repeats.

I'm convinced everything downstream of the blower is working properly, which narrows it down to the Novi unit itself. See plot below. The Green trace is where I was, and purple where I am today. I am overspinning the blower, and probably done some damage to it. I'm not familiar with the failure modes of this blower and hoping someone here has some input. I do hit MAX blower run at 7562 engine RPM; however the boost issues occur much earlier in the run.

I plan to contact Paxton tomorrow to see if they've seen something like this before. There is no obvious issue on the blower from a visual standpoint. No oil leaks, no shaft play, no loud clunking, nothing. I'm running a 8" crank and 4.2" blower pulley.

 

Never heard of this before. Typically when you over spin a blower, the failure point is the bearings, and that is very apparent by the noise.

Sure your belt isn't slipping again? Lol

But seriously,I'm just not sure how boost escaping from the blower would be possible, and more importantly not have any audible recognition coming from it that something was indeed wrong.

 

For those who've done a boost leak test, how much leakage is deemed acceptable? (in terms of pressure loss vs time)

If I go to 15 PSI on the gauge, it'll drop 5 psi within say 5 seconds then slowly creep down to 0. I've claimed this to be nominal, but reading posts on other forums people have claimed to hold pressure for several minutes.

I can hear a very minor audible leak, but did not consider it significant. My logic was if I can fill up my boost leak tester using a 3/8" tire inflator whip hose past my target PSI (essentially overcoming the minor leak), the blower which produces much greater volume of air should have no issue.

I'm starting to think if I have a case of a mere boost leak.


Edit: ...and then I go full circle. If I can go to 15+ psi using my leak tester and puny hose then it must be the blower not pushing the boost. right??

 

How are you performing the boost leak test? Are you capping off the aftercooler outlet?

If you hear a leak try using a spray bottle filled with water and a touch of dish washing soap. Spray every and everything that holds boost.

 

Have you put any dressing on the belt? That plot looks like belt slip.

 

I'm performing the leak test by placing the tester at the inlet of the blower. The plumbing for the entire system is still in-tact. When I place my tire whip hose to fill up the tester, the gauge goes from 0-15 PSI very quick and keeps going up until I let go. I do have a very very minor leak, not significant enough to do what it's doing now.

As far as belt slip, I'm running a 10-rib belt. No way in hell it's belt slip! lol No dressings either.

 

Typically I have only boost checked the system between the blower and throttle body. I dont pressure test through the blower inlet to the valves of the engine, you will always have a leak doing the test that way.

I simply pressure test the aftercooler inlet to the aftercooler outlet and any components in between. So I put a vacuum line on the BOV and in your case as you mentioned youll want to make sure the wastegate is shut as well.

 

This^^ i was going to get at that. Ive never done a pressure test still connected to the TB. I was going to suggest a manual vacuum pump to hold the bpv closed. Like i said if you hear it, its not small. I had a Hose clamp and coupler that would hold boost till about 10-12 and it would bleed out through the edges. I found it with a spray bottle and a dash of soap.

Do you have the air pump hooked up the aftercooler? if so get rid of that also.

 

No air pump - MY06

I'll go ahead and do what you guys suggested, leak test up to the TB. I'll probably still do it at the inlet of the blower, to capture everything upstream.

In reality what I'll do first is correct the very minor leak I know of now, which is at the outlet of the blower. All the other couplers are air tight, I've already sprayed soap water and checked ok. The other suspect location is the wastegate v-band flange interface against the fire ring.

Thanks again guys. I hope it's that simple

 

You cannot do a leak test into the engine. The throttle vbody leaks, at least one cylinder will have valves open...and even if you remove the cams to have all the valves closed...you still will leak past the piston rings... So testing the throttle body to the engine is pointless