can a MPS or stock MAP sensor missread

[b7g]

just as the title says, can the manifold pressure sensor go bad, or missread?
Just wondering, becasue of the trap speeds on a vf39 powered wrx were in the same territory as stage 2 wrx--max 98 mph, or about 16 psi. The mps reads 20 psi during logging.
It could be the driver though... But, I want to see if anybody knows about such instances.
Thanks...

[dumdum]

Originally Posted by b7g

just as the title says, can the manifold pressure sensor go bad, or missread?
Just wondering, becasue of the trap speeds on a vf39 powered wrx were in the same territory as stage 2 wrx--max 98 mph, or about 16 psi. The mps reads 20 psi during logging.
It could be the driver though... But, I want to see if anybody knows about such instances.
Thanks...

I have no idea what your talking about.What does psi have to do with your trap speed.Try explaining your situation better.

[b7g]

o'k...
I went to the track with my brother. I have a jdm 2.0 with a vf30 tuned to 20psi, he has usdm 2.0 with a vf39 tuned to 20psi. I was consistantly trapping 102-104 mph riding out the third gear, while the best trap he was able to get was 98 mph in his last run with a 6speed redlining 5th.
We came home and i did some logs...
His car has a boost gauge installed that supposedly is not very accurate (Autometer); the boost gauge at WOT in 4th gear shows 16-17psi, while the log is showing 20.x psi.
The above combined with his MAF readings of 260 g/s and comparing it to my car's 289 g/s made me think that it could be his manifold pressure sensor missreading.
Similar setups should yeild similar results...
Next step is to swap the sensor, but i wanted to check if it is possible or likely for it to be a culprit.
Thanks

[dumdum]

Originally Posted by b7g

o'k...
I went to the track with my brother. I have a jdm 2.0 with a vf30 tuned to 20psi, he has usdm 2.0 with a vf39 tuned to 20psi. I was consistantly trapping 102-104 mph riding out the third gear, while the best trap he was able to get was 98 mph in his last run with a 6speed redlining 5th.
We came home and i did some logs...
His car has a boost gauge installed that supposedly is not very accurate (Autometer); the boost gauge at WOT in 4th gear shows 16-17psi, while the log is showing 20.x psi.
The above combined with his MAF readings of 260 g/s and comparing it to my car's 289 g/s made me think that it could be his manifold pressure sensor missreading.
Similar setups should yeild similar results...
Next step is to swap the sensor, but i wanted to check if it is possible or likely for it to be a culprit.
Thanks

There is your answer.The MAP sensor only reads boost.The G/S are measured off the MAF sensor flow.I have no idea both of your full mods(intercooler,injectors,boost control) but your JDM motor has a redline of 8K and a turbo with a bigger top end due to the turbine housing.There could also be alot of other factors like the tranny he is using and his driving ability.

[b7g]

I did not get a chance to drive his car, but i probably should have to do a comparisson.
I do atribute my higher maf reading to better heads only. He has the rest of the system set up better than mine: Big MAF, huge filter, custom turbo inlet, Front mount, whereas my car has k&n drop-in, big top mount.
Both cars use stock bcs...
The driver ability is not excluded--it was his first time at the drag strip.

But nonetheless: is it possible for the MPS to missread a higher pressure?

[dumdum]

Originally Posted by b7g

I did not get a chance to drive his car, but i probably should have to do a comparisson.
I do atribute my higher maf reading to better heads only. He has the rest of the system set up better than mine: Big MAF, huge filter, custom turbo inlet, Front mount, whereas my car has k&n drop-in, big top mount.
Both cars use stock bcs...
The driver ability is not excluded--it was his first time at the drag strip.

But nonetheless: is it possible for the MPS to missread a higher pressure?

Not usually.I'm betting his gauge is off.

[b7g]

dumdum, do you know if 260 g/s is consistant with vf39 equiped wrx's? I was hoping for more air and load...
I will swap in my mps to see if that makes a difference, or see if i can log volts or check resistance in it to figure out if it is working right
I am going to finish minor corrections with the MAF scaling with that car and get a GMBCS. Retune boost and be done...

Thanks for your comments...

[dumdum]

Originally Posted by b7g

dumdum, do you know if 260 g/s is consistant with vf39 equiped wrx's? I was hoping for more air and load...

Sort of.The problem is you are looking at this from a 1 dimensional point of veiw.You have to take in account altitude,humidity,intake temps,tuning,supporting mods... 260g/s is pretty good for summertime.Airflow and load will always be highest at sea level and in colder,dry weather (winter).So it all depends on the conditions at the time you referenced that number.Thats like people who get hung up on dyno #'s. "My car has the same mods as Timmah's car,but his dynoed 30 hp more!What gives?" Well Timmah could be at a different altitude,running slighlty more boost/better tune,dynoed in the winter time,used a different dyno........so many variables.I know I will always see the most airflow,highest load,fastest spool up and best performance in the wintertime.So when I compare to other cars I look at where they are (altitude) and what the ambient conditions where when they got their numbers.