UKDriver

I've a C5 Corvette running about 5 lbs of boost.

I'm tapping into a 2 bar MAP that regulates my fuel pressure to send a signal to the CPU, bypassing the stock MAP located at the rear of the manifold

The stock 1 bar MAP sensor is in its usual location, just not connected electrically to the CPU - basically it plugs the hole at the rear of the manifold. What I noticed when doing this swap was that the MAP sensor seems awfully loose and since the switch over I'm not getting 5 lbs of boost, only 3lbs. I'm wondering if i'm loosing any boost at the rear of the manifold. Is there a maximum boost that these stock MAP sensors can hold on a stock manifold?

Anybody got views/experience on this? I notice that the Maggies have a much more robust arrangement to clip on the MAP sensor. Anybody done something similar for a stock manifold?

Ed @ Late Model Speed

iTrader: (4)

Sounds to me like you are loosing boost pressure through the factory MAP sensor mount. You might try replacing the rubber grommet, they tend to get a little worn and make the sensor fit sloppy. I have tuned cars with stock 1 bar MAP sensor up to 6-7 LBS.
Double check everything to make sure you don't have any leaks, that sounds like the problem.

Ed

ZL1Killa

iTrader: (17)

im running 5lbs and plan on going to 7lbs after I get my intercooler...not losing anything here

onfire

iTrader: (17)

Did you change the tune to accept a 2bar signal? Can't run a 2bar map on a 1bar tune unless you have a custom operating system.

UKDriver

Thanks guys

Running the HP Tuners 2 bar operating system, that all works fine with the Innovate LC-1, I just need to get into the 5 lbs region so I can tune in the VE table.

PITA if I have to remove the manifold again.

stevieturbo

Also check the line you are using to the MAP sensor isnt leaking either. This would give a false low reading.

How does your 2 bar MAP regulate fuel pressure ?

I was running up to about 20psi with the stock MAP sensor in its original location. Mine was quite loose too. Never had any problems with it.

Have you verified intake boost pressure with a gauge, as well as what you are logging with the ecu ?

Sluggish

iTrader: (10)

Thats the easy part, I can have my intake off in less than 10 minutes from the time I pop my hood. Its putting it back on thats time consuming. With a new gromet it should be fine. Remember the surface area of the sensor it probably a little better than a 1/2 square inch. So 2.5 to 3#s of pressure shouldn't be enough to move it.

ChevyChad

iTrader: (50)

I still have my stock MAP sensor in place and my car has seen 14psi without any issues. I have a 2 bar MAP I need to install, just haven't gotten around to it yet... But 5# should definitely NOT cause the stock MAP to leak. Go ahead and replace the rubber grommet just to be sure, but I don't think thats your problem...

UKDriver

Thanks again guys, that's encouraging.

New rubber grommet next time I'm in the States.

The Carroll Superpumper uses the 2 bar MAP to regulate the additional in-line fuel pump.

The logged MAP in HP Tuners matches the boost gauge, but will re-check the pipe work for leaks

SuperZ

iTrader: (2)

I ran 14psi on the stock map and mass air.Now I run a 2 bar speed density tune.It runs a little now but it ran just fine with the mass air too

black98ws6ta

iTrader: (77)

I wouldn't feel comfortable splitting the signal between the pcm and something else. Maybe that where the problem is...or does a manual boost guage verify you are not seeing 5 psi?

Frost

iTrader: (45)

should be ok doing this; the PCM and the other device should have *VERY* high input impedance to keep from having any load issues affecting the signal level output from the sensor.

black98ws6ta

iTrader: (77)

Alot of shoulds there....Id go spend the money for the 2 bar map that fits into stock location and call it done.

ChevyChad

iTrader: (50)

I may be selling my 2 bar MAP sensor that fits in the stock location. New in box, never installed. I'm probably going to stay with a MAF tune...

UKDriver

The manual boost gauge confirms the HP Tuners reading, so that bits working.

The whole reason I got into this mess is because I ordered a 2 bar map for a 1999 C5. The merchants at MSD (My Spark Disappeared) sold me one like the bottom one in the attached doc. I believed it because Robietherobot site recommended that style as well.

When I removed the manifold of course it was like the sensor in the top of the attached doc. So a quick work around was performed.

Lesson: Extract part before buying replacement - hey ho.