MAF dropoff above 4900 rpm

[dougB]

My MAF values dropoff above 4900 rpm. Is this normal? In one DS file the values drop from about 200 at 4900 rpm, to 190 at 5200 rpm, (FYI, I'm running an extender chip - so values shd be doubled). I have sevral DS files if anyone's interested.
Doug

 

[dsa87gn]

are you getting knock ??

if not it sounds like time for valve springs

 

[TurboDave]

Originally posted by dsa87gn
are you getting knock ??

if not it sounds like time for valve springs

MAF dropouts are a function of the ECM, chip in use, and Translator settings.

Absolutely NOTHING to do with valve springs.

 

[dsa87gn]

Doug said they were dropping off, i took it as values lowering.
after 4900.

If valves are starting to float, couldnt it be sucking less air ?
If not ,sorry for mis-information..

 

[dougB]

Thanks for the feedback, but maybe I'd better clarify my question.
My DS MAF graph climbs to its peak value at about 4900 rpm in each gear, then the MAF graph turns downhill above 4900, at about the same rate as it was increasing - but my rpm is still increasing! I expect the MAF values to drop as the rpm drops, not before..

I was thinking, like dsa87gn, that the air was getting choked down - maybe my valve springs were floating, or, my stock MAF hose was collapsing, or my 204-214 cam was saying to me "didn't you read - not for turbo application".
(I'm getting some knock, but not around each of these MAF peaks.)

Dave - is dropout what I'm experiencing? Or was my choice of the term "dropoff" too close to "dropout" - during a quick read of my problem.
thanks
Doug

 

[BoostKillsStres]

The MAF dropouts that I used to have were shown on DS for only a frame or two then the signal is back in line usually the MAF would drop from 255 to abotu 43 then back to 255. I believe this is what Dave meant.

 

[REDS HOT AIR]

email me a d/s file
evtb@cox.net

oh and its not the cam

 

[dougB]

Red - I emailed you a few DS files.
Doug

 

[dougB]

I uploaded 5 DS files with the MAF dropoff problem to my sprintmail web space. The DS files are located here:

http://home.sprintmail.com/~bowen/

(I just figured out how to upload files)
The files are named RunA - Run E. The issue can be seen in the graphs - RPM and MAF increase to about 4900 rpm, after that MAF drops off. The car is traction limited so the dropoff does not show up in 1st gear. It shows up best in 2nd gear and somewhat in third. I'm tuning my combination, so boost varies on the files - some runs were about 20, others up to 25. What is causing the dropoff? I've not noticed it on other peoples DS files.
thanks
Doug