chawkins2001

The car is heavily modded with belt wrap and 180mm CP with 77mm clutched upper. The boost curve is all over the place, what are your guys thoughts on potential causes. As a result, it is not making the power it should either!

Thus far I have smoked the motor with no leaks. I do have a new bypass valve on the way too to rule that out. Has anyone else experienced this type of curve and possible solutions.

Thx fellas

C32owner

Does seem way under power for that pulley setup, were you logging intake Temps as well? My boost also jumps around a bit like that. Never understood why, and I also have a bwk to illiminate any slippage.

chawkins2001

Yes, ended at 130*

BagMan

Just a thought. Needswings says that the surge tank gaskets start to leak at 14psi.

Here's link:
http://www.needswings.com/needswings...-gaskets-m113k

DVC

I've found that the BWK doesn't keep the belt from slipping if the S/C belt tensioner is weak. And they do get weak.

Hulk

DVC is correct

99lightning

Craig remember on the lightings magnum powers had that adjustable tensioner that's what the 55's need.

chawkins2001

Thanks so far fellas, might as well add a tensioner to the mix too

Hulk

99lightning that would be better than a bwk IMO.

Finny's idea for the tensioner adjuster was better but he never made it. He gave me the info on in but needed a sizable run to make it, too bad because the idea was great

seanol

Another thing to see if it is mechanical or not would be to datalog timing during the run. I use Torque pro. You can then plot it and see how much timing and where it is being reduced.

If the do not correlate with the dips you have a mechanical issue more than likely with what you have done so far. Less timing = richer mixture.

One other way to look at slip is a timing light. If it is adjustable for advance you can point it at the belt and if it slows down you will see it with the light. Takes some practice but works well for a final diagnosis. You may have to put a line on the belt with a sharpie so you can see it.

GatorMB

Did the curve happen after the mods or all of the sudden like something failed?

Hmmm?

Definitely something leaking or sensor amiss. The MAP runs the bypass valve.
If the engine is not too smoked find a way to close the BP valve for boost testing. C4 Dev might work,this will eliminate charge tank culprits and belt slip.
Caution when running the BP valve closed without custom tuning.

Cheers, Gator

I am old school when it comes to vacuum/pressure leak testing. They did not have smoke testing when I was servicing cars.

03svtkiller

Your probably heat soaking the **** out that b**** you should be over 15 pounds at least with that combo!! I no longer have a e55 so my advice is useless but I would say log it during a pull and see where timing is being pulled.. Gl bro

chawkins2001

It has a trunk tank, KC and meth. Started the pulls at 50* in these runs and ended at 130* so it is not to bad.

Hopefully the bypass and a new tensioner fix the problem.

bmwm3turbo

its just like mine buth whith overall lower boost
mine showed no leak either, and i have tried a secondary tensioner makes no more boost just snaps the bellts
hope you find a fix to this

chawkins2001

You use a brand new tensioner brotha? How much boost did you show, same power level?

Hulk

Craig do you the see the tensioner bouncing at idle?

bmwm3turbo

mine tensioner is 6 month old
my boost sometimes se as low as 13psi and spikes to around 18 psi
im on a 68mm pulley, bypass valve, or we are overspinning the sc is my guess

chawkins2001

No, stays in place.

Hulk

Doubt it's the tensioner then.

Try the bpv and hope that solves it man

StarvingArtist

Is this something you could share? Maybe someone else would make a few.

Hulk

I'll ask Finny if he minds me sharing

bmwm3turbo

i am happy now, did a pressure test this morning and for the first time i found an intake leak on the right side bank
hope this solves the ****ty boost curve and give som power

Ruthle55

Not that it really has any relevance, but even with a trunk tank/KC/Meth you're still ending up at 130 IATs at the end of what I assume is a 3rd gear pull?

BlackHammer

Glad to see you back. You had been quiet (silent) and was actually thinking on posting "What happened to RUTHLE55?"

OK, let's get back on topic. Good thread and feedback...

chawkins2001

Had you smoked the motor prior and it all came back tight and the latest pressure test revealed a leak?