[c2513892]

Hi,

My n55 335i does not hold boost while driving on the highway, the only time i have boost is while accelerating, as soon as i stop accelerating the boost goes away, what do you guys think is wrong with the car?

[e92proper]

Ummm keep accelerating on the highway!! Lol just kidding. Possibly may have a boost leak? Check all connections.....from throttle to IC. May find a leak

[Sidewinderpb]

lol

[Jsoboti]

Ummmm what

[MacE90]

Smoke test? Search the forums!!!!

[weehe126]

You realize you only create boost from accelerating right? Are you asking why do you not have boost while cruising at highway speed?

[c2513892]

Wait is it possible to have boost while cruising at highway speed?

[shadow191]

If your engine is under enough load, you'll have boost. If you're cruising at a constant speed, you're probably not boosting. But as soon as you start accelerating, you should be boosting. It all depends on exhaust flow.

You don't create boost while parked at a stoplight either...

Originally Posted by c2513892

Wait is it possible to have boost while cruising at highway speed?

[c2513892]

"ou don't create boost while parked at a stoplight either..."

That was funny, thanks everyone your replays are much appreciated.

[bmw0bsession]

Lol this is awesome, I make like 1psi of boost cruising

[e92proper]

1st turbo car? And more importantly, how are you measuring boost?

[kseyfi86]

Lol you should be glad, something would be seriously wrong if it kept boost without acceleration. Not to mention you'd probably get like 6 miles a gallon. You'll get boost when you need it, not while cruising at a constant or decreasing speed.

[grizz311]

not sure if serious

[norsairius]

Haha, we all gotta learn this stuff somewhere.

In short, as others have said: your motor is only really making boost when you're accelerating. Otherwise, when you're cruising, very little boost.

You may notice that if you accelerate briskly and then let off the the throttle a bit (but not completely) after you've reached your desired speed but want to maintain it, you'll hear a little whistle/pressure release-type sound. It's just letting out that pressure/boost that's not needed anymore since the motor doesn't need all that power for accelerating. Cruising/maintaining speed doesn't require much power.

[1cleann55]

My diesel 6.4L makes 15psi while cruising . WOT it makes 50psi. So much torque it can move the earth.

But yes as everyone states on other cars you aren't supposed to be making boost at cruisING speeds.

[lrwatkins]

sorry its just funny

Originally Posted by c2513892

Hi,

My n55 335i does not hold boost while driving on the highway, the only time i have boost is while accelerating, as soon as i stop accelerating the boost goes away, what do you guys think is wrong with the car?

[Socket]

Originally Posted by c2513892

Hi,

My n55 335i does not hold boost while driving on the highway, the only time i have boost is while accelerating, as soon as i stop accelerating the boost goes away, what do you guys think is wrong with the car?

Read this thread, low boost commonly linked to cracked vac lines
http://www.e90post.com/forums/showthread.php?t=546560

[timothy2001]

And this is exactly one of the reasons why there are pros on this forum, for FNG's like myself who have no or limited knowledge and experience.

Hell, maybe even I can contribute here. Your turbo compresses air and shoots it into the cylinder to provide a boost of acceleration when you put your foot into it. When you are maintaining speed as in just cruising you should see little or no boost.

To the OP, keep asking away or better yet search first but I have found that this forum is really the best knowledge base out there. I was a Service Manager in a GM dealership for many years, and I worked on Gas Turbine engines in the Navy and I am pretty clueless about our cars.