ajrothm

Your boost psi should steadily increase until you reach redline. The higher the rpms, the more psi or KPA you should see.. If it gets to where the psi stops climbing, that means the belt is slipping, inlet is restricted or the engine is consuming everything the blower is making.

Post a pic of the MAP KPA in HPT.

DOUG @ ECS

Sorry, I missed this. No normally I do not have to desensitize C5 knock sensors, but I have had a weird situation or two where I did. I usually then replaced the operating system in the PCM and it cured itself.



Your belt is slipping, make sure your adjustable idler under the head unit pulley is cranked all the way in. The belts can be .010 away from each other, they will never hit. If it is all the way in you may need the next size smaller belt installed.

Here's our belt install video if that helps;

neutron82

couldn't he also try another setting on the power steering idler?... that is assuming the idler is in the middle or top hole already then you might be able to move it down to avoid having to buy a new belt, assuming that's the issue

DOUG @ ECS

Absolutely thanks.

danieloneil01

Belt is all the way adjusted on the head unit. Guess I'll go buy the next size down.

Turbo-Geist

Looks like belt slip. More importantly, why is it reading 11.1 psi? My calculator says 187 kpa is 12.42 psi @ 6,000 rpm. If you didn't have belt slip, what would it be at 6400 rpm?

Also looks like the AFR may have been trending upward until the boost loss and fuel pressure was dropping.

ajrothm

Looking at the chart, it builds to 12.5 psi pretty quick then just holds there.. (Almost like it has the restrictor still in it). It kind of looks like belt slip but usually the boost will fall off harder then that at higher rpms. With that much belt wrap, I can't believe its slipping but... It could be slipping around the crank pulley. Maybe try going to a 1/2" shorter belt.

Your boost pid is not correct. 187 KPA is about 12.5 psi... If you're seeing that at 5500 rpms, you'll be over 14 psi easy at 6500 with no belt slip.. Keep an eye on your AFR/meth.

Btw we have a couple C5Zs rolling out to the car show in Pearland tonight if you wanna roll out with us.

danieloneil01

I had to manually put in the numbers into hptuners for the boost gauge. The AFR was not going up but down actually and I have no issues holding fat AFRs even without meth with my basic fuel setup. It was the first time running meth at 8 on the **** and I reduced the VE table a bit for the added meth. Not hardly a complete tune.

Highest rpm before shift. Looking at 3 runs it starts to drop boost close to 6k rpms and drops to 7-8 psi at redline.

danieloneil01

Thanks for the offer but I'm working nights. Guess I need to also look into setting up my boost gauge correctly in hptuners too. fuuuuuuuuuuu

ajrothm

Yeah I see the boost falling off... It shouldn't do that obviously, it shouldn't ever plateau as long as there is no boost leaks or belt slip.. That thing got up to 12 psi pretty quick then flat lined for a long time, that isn't right..

As RPMs climb, boost should as well...at least until you get to the point where the engine is eating it all up.... You're not even close to that with your pulley combo..

I'd check for boost leaks real well, check the BOV as well.. Then swap to a smaller belt.. More then likely its belt slip. A shorter belt will allow it to get tighter without getting the tensioner out of its range.. You have some killer belt wrap on the blower pulley tho..

danieloneil01

Does this look more accurate from my boost gauge?

5246 rpm
171.3 kPa
11.7 psi

danieloneil01

double post

danieloneil01

Bought a belt 1/2" shorter and it was just to short but not by much. I'll try one that's 90" this go around. But after putting the old belt back on it seems much closer together by the blower than the picture I posted earlier.

Turbo-Geist

187 kpa = 12.42 psig

171.3 kpa = 10.15 psig

Formula: kpa X 0.145037738 = psia then subtract 14.696 to get psig.

Example:
_171.3 X 0.145037738 = 24.85 psia rounded to the nearest hundredth

_24.85 - 14.696 = 10.15 psig

Another quick reference is stickied here: http://forums.corvetteforum.com/c5-f...reference.html

danieloneil01

Thanks for the equation.

danieloneil01

Got a smaller belt but really wanted a 90" but all they had was a 90 1/8" belt. It was shorter than the one I took off and a lot more than 1/8" since I'm assuming the old belt was stretched. But the new one still maxes out the tensioner off the blower. If it still slips I'll find a 90 or 89 7/8, but I;m going to get on it after work when it's a cool 80* outside.

I got on it after putting the old one back on last night and on the way home it held 12 psi much longer but still went down. But for some reason this time it didn't get any knock with 13* timing and my AFR was 11.2 to 11.4 most of the run. The KR always comes right before or after entering PE and never when I'm deep into a WOT run.

danieloneil01

So I'm trying to find the proper length. I bought a

K060895 90 1/8 which is to big and maxes out the blower pulley
K060885 89 1/8 which is to small

So what should I get next? Gates website shows

K060888 ............................... 89 1/2
K060891 ............................... 89 3/4

Obviously I can try the 89 1/2 first but is there such a thing as to tight?

I'm also going to replace the t bolt clamps from the blower to the IC to one size smaller since 2 of the 3 were maxed, i.e. tightened all the way. But I'm leaning towards belt slip and not a boost leak but I'm usually wrong on this ****.

ajrothm

I would do the 89 1/2". Remember its gonna stretch some after the first couple hits. No such thing as too tight if its aligned right... Hard on bearings yes, but less chance for belt slip... I tighten mine with a 3' pry bar.

danieloneil01

Yeah, the old belt was stretched quite a bit when I removed it.

danieloneil01

Got the right belt, K060888. I barely was able to get it on too. I have it on tight but will use a cheater bar to get it really tight.