boost vs boost est[imate]

[tunerdoc]

Can any one tell me what would cause a difference in the two readings? my boost gauge reading is 3-5 lbs higher than my boostest on a dsmlink. I have been chaseing boost leaks and have found most, I read a thread that comments on the reverse findings when the boostest is higher it indicate leak after MAF is thi the same indicator or does it mean something else?

Thank you
Doc

 

[SOADweskey]

If your IAT (intake air temps) are above 70* then your boost est will show lower than actual. I just setup a cold air intake on my car and it brought my boost est up much closer to my actual boost.

You could also have a leak between the MAF and the turbo that a boost leak tester wouldn't find. Check your intake pipe and all the hoses attached to it.

 

[daren_p]

Where are you comparing your boostest vs boost gauge? They should only match in the 5000-5500 range. Are you running the stock MAF or GM? (if GM, what config?) Have you verified your boost gauge? (have yet to see even a new Autometer bang on, & have seen them being 2-4 psi out)

 

[tunerdoc]

I am running a stock MAF,
The boostest vs boost comes from the dsmlink and a visual while running.
I will do the test again and stay at 5000 5500 I assume in 3rd gear.
I will check for leak after the maf how do you test the intake pipe?
Should I put the boost tester on the upper intercooler pipe for this test.?
Thank you for the answers.
Doc

 

[SOADweskey]

I don't know of anyway to test the intake pipe by pressurizing it. But since it isn't a pressurized pipe you shouldn't need to. I would just make sure all the connectors are on properly and tight and that it can't suck free air through your catch can line, or the vacuum line to the boost control solenoid, or from the third line on there that I can't seem to remember what it goes to now.

 

[daren_p]

You don't need to stay in the 5000-5500 range, I was just implying that the only area where boostest & your actual boost should match is in the 5000-5500 range, so when reviewing a log only look at this area as its normal for boostest not to be right on before this rpm range & it is also normal for boosest to drop off in the upper rpms, even though your boost holds constant. Temp will have an effect on boostest but not sure how far off of the ideal (think its based on 70F) you would have to be to see a 5 psi difference (what are your air inlet temps?). If you had boost leaks, your boostest should be higher then your actual boost. As I said above, I'd check your boost gauge as well, as its not uncommon for them to be a good amount out.

 

[tunerdoc]

Thank you both I will look into the above noted information and double check the logs for the changes.
The one line I didn't check was the catch can, I will do that tonight.

Thanks again

Doc

 

[DevilSperm]

You did right click, go to props and put in the right information didn't you? That will throw it off as well.

 

[T9S1i]

have you touched any of the airflow sliders?

 

[tunerdoc]

the air flow sliders are set a 50hz to 20 150 hz to 14.

Doc