Very Little Boost
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Laughing Gas
Joined: Oct 2007
Posts: 773
Likes: 1
Very Little Boost
I bought a 1997 F350 7.3L w/ 100K miles. Truck is all stock and in great shape overall.
Only problem is that it seems to be making very little boost according to both seat-of-the-pants feel and an Edge monitor I have plugged into the OBDII port. At wide open throttle, say pulling onto the highway, the monitor shows like 7-8 psi max. Cruising around at steady throttle only shows 0-2 psi. The truck doesn't feel like a total dog, but it certainly feels heavy and slow, and I only get an average of 9-10 MPG to boot.
I'm not getting any CEL or codes. I replaced the air filter and fuel filter not too long ago too.
I gave a quick look at all the intake boots and joints and saw no obvious signs of leakage. I also popped off the turbo intake boot and felt for any play in the wheel. It feels tight and spins smoothly. The EBPV also seems to be working (in other words, it doesn't seem to be closed, because unplugging it has no effect on boost).
Am I missing something? Or are these OBS trucks actually just this 'slow' feeling? Does the OBDII port even give you correct boost pressure readings? Thing is, I've never owned / driven a 7.3L truck before so don't have any point of reference to compare with.
Only problem is that it seems to be making very little boost according to both seat-of-the-pants feel and an Edge monitor I have plugged into the OBDII port. At wide open throttle, say pulling onto the highway, the monitor shows like 7-8 psi max. Cruising around at steady throttle only shows 0-2 psi. The truck doesn't feel like a total dog, but it certainly feels heavy and slow, and I only get an average of 9-10 MPG to boot.
I'm not getting any CEL or codes. I replaced the air filter and fuel filter not too long ago too.
I gave a quick look at all the intake boots and joints and saw no obvious signs of leakage. I also popped off the turbo intake boot and felt for any play in the wheel. It feels tight and spins smoothly. The EBPV also seems to be working (in other words, it doesn't seem to be closed, because unplugging it has no effect on boost).
Am I missing something? Or are these OBS trucks actually just this 'slow' feeling? Does the OBDII port even give you correct boost pressure readings? Thing is, I've never owned / driven a 7.3L truck before so don't have any point of reference to compare with.
Lead Driver
Joined: Sep 2002
Posts: 9,524
Likes: 2,028
From: North Texas
7-8psi at what RPM? These are not wastegated, nor VGT so need RPM to really make some flow. I cruise 70 @ 2500rpm and do 3-4psi on a level grade. Full tilt at 3500rpm in 4th or 5th I see about 14-15psi on a stock tune. Truck has stock injectors, bellowed uppipes, 910 springs, full exhaust, plenums resealed, Adrenaline HPOP, updated CCV/plenum boots from Riffraff. Basic mods really.
These numbers are off my Edge Insight.
You probably have leaking uppipes, like every old 7.3 until addressed...this is a loss in turbine drive pressure, thus low boost.
These numbers are off my Edge Insight.
You probably have leaking uppipes, like every old 7.3 until addressed...this is a loss in turbine drive pressure, thus low boost.
Laughing Gas
Joined: Apr 2020
Posts: 1,231
Likes: 284
From: NT, See you in the
Where does the edge insight pull the boost from? MAP sensor?
Lead Driver
Joined: Sep 2002
Posts: 9,524
Likes: 2,028
From: North Texas
Yes, the MAP. I put one of those bypass valve things on it as I really doubt it was designed to see 30psi. Most I have ever seen on stock tune all sealed up was 15psi @ 3500rpm.
Laughing Gas
Joined: Apr 2020
Posts: 1,231
Likes: 284
From: NT, See you in the
I installed one for the same reason. I've read of a few SD guys having constantly replace their MAP sensor due to high boost so I figured the little insurance couldn't hurt.
Hotshot
Joined: Dec 2005
Posts: 14,375
Likes: 604
From: evansville in
If you want to see boost numbers you really better be getting after it . Check that pass side up pipe connection at the top where it goes into the slip joint. Usually that pass side starts leaking first.
Just driving around you won't see much it any at all.
when my truck was stock and ran I could touch 20psi if I hit it just right and the air was right. If it was hot or the trans shifted wrong or,or,or..
This in my opinion was best case scenario. My ol 96 sc would do like 15 but it was painfully stock ,exh,intake. That's prob realistic.
Just driving around you won't see much it any at all.
when my truck was stock and ran I could touch 20psi if I hit it just right and the air was right. If it was hot or the trans shifted wrong or,or,or..
This in my opinion was best case scenario. My ol 96 sc would do like 15 but it was painfully stock ,exh,intake. That's prob realistic.
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