Chevrolet Cruze Forums banner

1 - 15 of 15 Posts

·
Registered
Joined
·
57 Posts
Discussion Starter #1 (Edited)
Hi guys,

I installed a boost/vacuum gauge to see what the stock boost pressure is.

On average I see about 12-14 PSi range maybe it can get to 15 PSI in certain conditions.

Just curious if that seems about normal?
For the vacuum side with the engine idling I see about 10-11 inches, does that seem about correct?

I saw a video on Youtube stating that the stock A/F ratio @ W.O.T is about 10.3? Does that seem close?

The gauge might not be too accurate because it is inexpensive steeper gauge type. I just wanted something to measure vacuum & boost.

Thanks
 

·
Super Moderator
Joined
·
5,526 Posts
I have no definite information as far as boost specifications, however, the boost numbers you provide are, for the most part, in line with what is generally accepted as normal boost range on a unmodified system.
The A/F ratio is the norm for a wide open throttle condition......think of the throttle as nothing more than a fuel valve.

The, at idle, vacuum is lowish but that probably is because this itty bitty turbo is likely adding a bit of boost at idle.....the pinwheel is about the diameter of a silver dollar......so, you really shouldn't take that reading into consideration for general engine health concerns.

The only time idle vacuum is useful as a diagnostic tool is if the gauge bounces rapidly.......an indicator of a leaking intake valve or a vacuum leak at one of the four port runners.

Rob
 

·
Registered
Joined
·
5 Posts
Question so I have a 2017 Chevy cruze LT 1.4l turbo "LE2" .
I got myself a little bluetooth OBDII reader and an app called dash command, i have an AEM CAI, now my boost doesnt even reach anywhere near that maybe at like 5k rpms gets to 2 psi according to the app anyone else get that or is it just me and most likely I have the worst boost leak in history(also no codes pop). ATM I'm on deployment so cant really test it but any suggestions on how I should test it and what to look for been doing some research but find nothing other then new turbo due to bypass value being built in.
 

·
Registered
Joined
·
10 Posts
Question so I have a 2017 Chevy cruze LT 1.4l turbo "LE2" .
I got myself a little bluetooth OBDII reader and an app called dash command, i have an AEM CAI, now my boost doesnt even reach anywhere near that maybe at like 5k rpms gets to 2 psi according to the app anyone else get that or is it just me and most likely I have the worst boost leak in history(also no codes pop). ATM I'm on deployment so cant really test it but any suggestions on how I should test it and what to look for been doing some research but find nothing other then new turbo due to bypass value being built in.
Was it reporting correctly before the CAI install? My initial guess would be the OBD2 adapter PID settings in the app are not configured correctly. I had the same issue with mine (I use torquePro), and I have seen others with ultragauge reporting the same low numbers when not setup correctly. According, to [email protected]

Most aftermarket OBD2 gauges use the MAP sensor to determine boost. GM made some changes in 2016 to the way the MAP pids work so most aftermarket OBD2 gauges report incorrect values on 2016+ GM vehicles.
Check out this thread for some info....

https://www.cruzetalk.com/forum/377-gen2-powertrain/216305-3lbs-boost-about-1second-2.html#post3013970
 

·
Registered
Joined
·
1,988 Posts
Dash command isn't accurate. You'll get different numbers over torque pro. Which reads deeper vacuum and higher boost.

Or maybe torque isn't accurate. Either way, the 2 apps read different.

At my altitude. Full vacuum is 22.5. Torque hit that and maxed out at 5 boost.
Dash bottomed out at 10.25 and maxed out at 2.5 boost,.
 

·
Registered
Joined
·
114 Posts
Hi guys,

I installed a boost/vacuum gauge to see what the stock boost pressure is.

On average I see about 12-14 PSi range maybe it can get to 15 PSI in certain conditions.

Just curious if that seems about normal?
For the vacuum side with the engine idling I see about 10-11 inches, does that seem about correct?

I saw a video on Youtube stating that the stock A/F ratio @ W.O.T is about 10.3? Does that seem close?

The gauge might not be too accurate because it is inexpensive steeper gauge type. I just wanted something to measure vacuum & boost.

Thanks
10.3:1 air/fuel ratio is way too rich. I would expect to see W.O.T. a/f no richer than 12.2:1
 

·
Registered
Joined
·
6 Posts
Screenshot_20190321-190703_DashCommand.jpg
I'm not sure how Dashcommand and Torque would show different values, unless one of them has some damping.
With Dashcommand, you can log to a csv file and see the values as read.
This is a screen grab from a log replay.
2012 Cruze LT/RS box stock.
 

·
Registered
Joined
·
151 Posts
I have my vacuum/boost gauge ported into the throttle body. I get about 30 inches vacuum at idle, and on stock ecu it highest is about 18-20 psi if it’s pushing it hard


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
57 Posts
Discussion Starter #14
30 inches of vacuum seems really high especially for idle.
Also the boost seems high for a stock set-up. I would think your gauge needs a calibration check.
 

·
Registered
Joined
·
1,988 Posts
According to google.

30 in. vacuum at sea level. With a .5 in decrease for every 1,000 feet in altitude.

I got 25 in. in Cali at sea level. At home at 4,500 feet. It don't matter if I'm pulling vacuum in my 7,000 gallon tank trailer or a car ac system. 21 is all I get. I'm not sure what the torque app would read. I've barely used that gauge or the app much.

Boost pressure was 30 max in my semi in Cali. At the top of Donner pass at 7,500 feet it was 18 I believe. I don't think I even hit 10 in the Colorado mountains at 12,000 plus feet. I haven't been in that truck for 3 years now. I no longer have a boost gauge. And that's a semi with a much larger engine and turbo 3 X the size. I wouldn't expect our 1.4L to even come close to the same numbers.

Stoichiometric AF was 14.7 on the carburetors. 15.0 with fuel injection. Don't remember the number for idle and WOT. Or what it might be these days with today's Direct injection. I've been retired almost 20 years now.
 
1 - 15 of 15 Posts
About this Discussion
14 Replies
10 Participants
snowwy66
Chevrolet Cruze Forums
CruzeTalk.com forum, news, discussions and the best community for owners to discuss all things related to the Chevy Cruze.
Full Forum Listing
Top