Erratic boost reading

[KMinAF]

I installed the MBCV last night (correctly this time, one hose to the housing one hose to the actuator) but can not get a steady boost above 5 psi. When I try to adjust the controller (1/4 turn at a time) it will either spike past 8 PSI and settle back to 5 PSI or max steady at 5 PSI (about the center of stock gauge) Is it possible the BOV (stock) is begining to fail? I have tried blowing through it and it seems tight. I checked all hoses and clamps with NPF. The hoses to the MBCV are under 8" long, if the hose was not heavy enough would they "balloon" and cause a spike situation?

Adjustments were made in second gear pulling from 3000 rpm to about 4500rpm

 

[89turbotoy]

get a better boost guage the stocker is not accurate. then see if it is working

 

[KMinAF]

The boost pressure spikes past the gauge limit often hitting fuel cut. Also after 2 or 3 pulls then it maxs at the stock 4 -5. If I try to back off the BCV even an 1/8 of a turn then it maxs out at the factory 4 - 5psi. I think I might have a faulty BCV?

 

[starscream5000]

What are your mods? Based on the psi you are seeing normally, I'm guessing stock if things are running right. If this is the case, then you need to take off the MBC for now and worry about freeing up other restrictions first.

 

[OneJoeZee]

The stock gauge is usually accurate enough but just too slow to react. Get a better gauge, then get some better results. I could just about spool full boost on my car and let off before the stock gauge even moves.

 

[Poodles]

What are your mods? Based on the psi you are seeing normally, I'm guessing stock if things are running right. If this is the case, then you need to take off the MBC for now and worry about freeing up other restrictions first.

Yep, as the top end pull is gonna be smothered pretty bad, not to mention if you're a 5-speed your boost is low meaning you have a serious restriction or leak...

 

[supramike7m]

The stock gauge is usually accurate enough but just too slow to react. Get a better gauge, then get some better results. I could just about spool full boost on my car and let off before the stock gauge even moves.

agreed, same here. its crazy to see how slow the stocker reacts right next to a good gauge

 

[88YotaTurbo]

Same here, better a better gauge.

 

[KMinAF]

I have 3" pipe from turbo to tail pipe and KN filter KN filter.
Engine has approx 2000 miles since complete rebuild including Metal Head gasket

Sounds like I need a real gauge.

Any suggestions on brands and mounting locations?

 

[supra4ever68]

yeah i need to get one also....it takes a while to get up to my max 7 psi. Is that pretty good for a stocker?? my uncle had the turbo rebuilt but i don't know exactly what he did to it...oh and someone answer his question...i also need a good gauge.

 

[Poodles]

prosport

but anyway, you're reading pretty low still for having a free flowing system...

something else is up, be it a boost leak or something...

 

[starscream5000]

Boost leak, bad turbo, vacuum leaks...

 

[KMinAF]

I agree that any of those could be responsible for the erratic readings. I am in the process of puting together a Home Depot pressure tester just to make sure there are no leaks. All connections and ducting passed the visual inspection. The puzzling thing is that on the first pull the boost will read way high (beyond the gauge limit) but during subsequent pulls it maxs out at 5psi and never goes any higher as though there were no MBCV installed.
This week I will be installing a MBCV from Dr Jonezz on the chance the old valve is the culprit as well as a quality boost gauge.

 

[KMinAF]

I agree that any of those could be responsible for the erratic readings. I am in the process of puting together a Home Depot pressure tester just to make sure there are no leaks. All connections and ducting passed the visual inspection. The puzzling thing is that on the first pull the boost will read way high (beyond the gauge limit) but during subsequent pulls it maxs out at 5psi and never goes any higher as though there were no MBCV installed.
This week I will be installing a MBCV from Dr Jonezz on the chance the old valve is the culprit as well as a quality boost gauge.