map pressure decreases under full throttle as rpm increases

[turnbull2003]

hi i did a few logs last night after a while of no tuning and taking my tune back to stock, and noticed that under full throttle the map readings would start decrease as rpm increases,
ie at 1782rpm and 100% throttle there was 102kpa but at 5480 rpm it had dropped off to 96kpa.

My question is, is this normal or does this indicate that i have restrictive intake/air filter?

[WeathermanShawn]

Welcome to the Forum:

Unless you are going full throttle up a hill or mountain it is not normal. Perhaps a manifold intake leak, bad MAF, bad catalytic converter..Too many things to guess at.

Check out this sticky for a start: http://forum.efilive.com/showthread....nt-Good-Tuning

[Mr. P.]

You definitely have a restriction somewhere; try making a run without the air cleaner element (maybe it's dirty?) I've also seen plastic CAI boxes & tubing collapse in on itself during WOT. And as Shawn suggested a clogged cat will cause this too.

Mr. P.

[turnbull2003]

thanks, i'll take it for a run tonight with and without the air filter and see what happens.

[The Alchemist]

hi, this is completely NORMAL for a stock intake system and you should not be concerned!!! I've seen 100's like this
Fitting a good high flow (less restrictive) intake usually ends up with 97 to 98 KPA at the rev limit netting 8 to 10kw at the wheels gain....sometimes more once you redo the timing as the load points change under full load with a different intake.
My 2c.
Cheers,
Mike

[macca33]

I'm with the alchemist on this one!

cheers

[turnbull2003]

hi, this is completely NORMAL for a stock intake system and you should not be concerned!!! I've seen 100's like this
Fitting a good high flow (less restrictive) intake usually ends up with 97 to 98 KPA at the rev limit netting 8 to 10kw at the wheels gain....sometimes more once you redo the timing as the load points change under full load with a different intake.
My 2c.
Cheers,
Mike

sorry to bring up an old thread, the intake was the cause, i fitted an otr and now at wot the vac starts at 102 and only goes to 100kpa and feels much more lively

[joecar]

Thanks for posting your results

[Naf]

Check your airfilter...I found mine was restrictive above a certain airflow and it caused my map to drop at WOT on the dyno...

YOu will notice the MAF will also decrease as the map decreases, these are signs of a restrcitive filter...You will also notice the mixture will lean out no matter how much PE or MAF you add

[Sid447]

Always considered it normal,

For MAP do drop off as speed rises due to an increasing positive air flow being forced into the intake system (ram air effect) which should be more pronounced with a straight OTR type intake.