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Blueovalnut · 02-29-2020, **(Subject: Boost pressure )**

Hello to all, I recently bought a used diesel pusher Motorhome that has been de-mandated. It runs good, but the boost pressure is 34-36psi while driving on flat highway at 65mph without towing anything. The highest boost pressure I’ve seen is 39psi during heavy accelerating. The 34-36psi on flat highway driving seems high to me. What do you guys think? Also at idle it has 2-3psi and sounds like a jet engine getting ready for takeoff. 2007 Cummins ISL 425hp in 42’ Motorhome. Thanks in advance for your replies and for letting me join the forum.

Nilao · 02-29-2020, **(Subject: Boost pressure )**

Almost sounds like a stuck turbo. Mine was boosting too much...would need insite to properly diagnose it though.

Blueovalnut · 02-29-2020, **(Subject: Boost pressure )**

Ok thanks. I have a laptop, but where's a good place to purchase Insite?

tree98 · 02-29-2020, **(Subject: Boost pressure )**

Wait stop right there!! You most likely have a bad delete, I would bet money on it. I'm not real familiar with the ISL but I'm pretty sure it has a VGT turbo on it. Most so called "tuners" don't know how to make a VGT work after a demandate so a lot of times you end up over boosting. I would think 39 psi on that thing might be enough to do damage. You need to have someone here look at that program. Also once Rawze comes along and sees us talking about an RV he might run you out of here lol,guess we'll see.

Here's what you need https://www.ebay.com/itm/401990863045
That's insite and the inline adapter that you'll need.

JMBT · 02-29-2020, **(Subject: Boost pressure )**

Check all your turbo piping and your CAC with a bottle of soapy water while the engine is running at a high idle. It sounds like you either have a bad leak in the intake system causing the turbo to spool up when it should be or a “bad delete” that has the boost set to aggressively. I would also check/replace your IMAP and exh back pressure sensors.

Blueovalnut · 02-29-2020, **(Subject: Boost pressure )**

tree98/JMBT I think your on track with me having a bad delete. Our Motorhome does have a VGT turbo on it. Hopefully Rawze doesn’t run me off his site I really appreciate you guys help and would like to get the tune looked at. Who do you recommend?

tree98 · 02-29-2020, **(Subject: Boost pressure )**

Unilevers, mommaburt, or Rawze himself.

hhow55 · 02-29-2020, **(Subject: Boost pressure )**

(02-29-2020 )Blueovalnut Wrote: Ok thanks. I have a laptop, but where's a good place to purchase Insite?

ebay

Wildcard · 02-29-2020, **(Subject: Boost pressure )**

I am gonna jump in here as an owner of the same engine and application. My boost under full load pulling a 6%grade is 30-32psi and I run around 8-10 ish maybe a little more on flat ground pushing 65-68mph. I would say you have a problem. And if you keep pushing the boost that hard you're gonna have a major problem. You need an Inline 6 or 7 Adapter and a clean laptop. You don't really want one that you surf the internet etc on for fear of virus. (Maybe that's just me) I wouldn't want any chance of corruption when dealing with flashing an ECM.

Then you have to sweet talk some names mentioned to help you out with programming.

I am currently in same boat waiting to do some custom tuning awaiting my for my adapter to arrive.