Hey guys,

I have been trying to troubleshoot an idle problem since installing my cam. I know it's gonna idle rough (lopey) after the Hotcam, due to the 112 lobe spacing, so that's not what I mean.

Anyway, what I need to know is what is the typical/normal range for the MAF readings.... at idle and at various RPM's that you have noticed.... and also, what is the MAP sensor supposed to read? is this an actual vacuum reading?....

What happened was I had a ported MAF, and the car just would NOT idle with it plugged in, at all. It would straight-up die.... Now, I put my STOCK MAF ends back on, and it will actually idle and only rarely die, and my MAF readings are from 5 to 40, depending on rpm ranging from 500rpm up to 4000rpm (no load)..... and the MAP sensor, at idle is reading 16-18.... on my LT1 Scanmster.

Is this a normal range?

I know I have one vacuum hose lose -- I lost the fitting, so I have to get a new vacuum fitting, but it's not hissing, so I don't think I'm losing much vacuum there. It's the fitting that goes to the charcoal cannister (bundled with the fuel lines).

Thanks,

Michael

 

Thanks for the reply! I think the numbers should be the same, regardless of what scanner you use.... I didn't get real scientific with the MAf numbers, because I didn't wanna sit and rev too many times in my driveway, heh. The neighbors don't appreciate it

Thanks again, I really appreciate your numbers!

-Michael

 

Fred we have been at this one too many times... I got the 20HG measured with a Mechanical Vacum Gage. My scanner reads MAP in volts and I did all the Math you thought me to do using your web page and it turns out to be around 20HG of vacum.

In short 20Hg vacum measured with mechanical vacum gage and
20Hg vacum using math to calculate the volts measured
by my scanner.

Thats why I said

The actual reading is about 9.5hg and that "corresponds" to 20Hg vacum.

In my post I had already calculted the Intake Vacum and I wasnt reporting my scanner reading in volts that represent about 9.1 HG.

So In Short Fred, I think you always refer MAP as Manifold apsolute pressure (correct) and I always translate it to Inches of Vacum (correct to? nope but nice try huh? =) ). AY AY AY mama mia !! Now I have to use either Intake manifold Vacum and MAP to make sure there isnt any misunderstanding unless you end up reaching out the computer monitor and strangle me


Oh by the way Thanks to Freds explanation now it makes sense to me when he said he is pulling 16-18 on the MAP sensor reading... that corresponds to 12 - 14 vacum Hg. Now thats the vacum I have seen with engines using 12* Lobe separation, Just like Fred said.


Fred sorry for the misunderstanding, I am gunna use the term Vacum from now on as in 20HG vacum.


Marvin

 

grendal



Grendal. I am sorry I gave you the wrong information. I used the term MAP when I shoulve used Vacum in my first reply. Those terms are not interchangable. Please disregard everthing I said. Injuneers reply is correct. I am deleting my first reply so not to confuse other board members.


Fred I didnt post to **** you off. You dont wanna talk to me then its my loss. It was an honest mistake of my part.


I will be more careful next time.


Marvin

 

Hey guys, thanks for all the help.

While I have you here, I have another quick one. I went and tried to do some G-tech runs today, but traffic was too heavy. I managed ONE quarter mile run, and I was showing 11 degrees of knock retard on the SCANMASTER.. Yikes! How much power is that losing me?? Sounds like I'm gonna have to get an LT4 Knock module to go with my cam.

BTW, it was not a terribly great run. 13.5@107.... would probably be more like 102-103 at a real track, the way tracks measure it.... I ran this fast *before* the cam, so I know the KR has gotta be killing me.

Thanks,

Michael