Injected61

Is it normal for my MAP pressure readings to lower as rpm goes up? I seem to get more vaccum as rpm increases, I thought it would be less vaccum as RPM goes up. Is it possible to restrick air enough to cause this?
Air filter is new, the rectangular type that fits directly on TB (3" thick).

Tuned Performance

iTrader: (92)

A map sensor is not a vacuum sensor. How are you measuring manifold vacuum to see a increase when the throttle blades are open more ?

Ronny

iTrader: (1)

I think he is seeing higher MAP readings as RPM goes up. 100 MAP = 0 VAC 90-100 MAP= WOT

Tuned Performance

iTrader: (92)

I thought it was some new engine design, thats awesome increases vacuum with the throttle opening.

Ronny

iTrader: (1)

Maybe the vacuum pump to purge the crankcase is too large? LOL

Tuned Performance

iTrader: (92)

I think your on to something I will get started on making the zero bar map.

Injected61

I know the MAP sensor is not a vaccum sensor, its reads pressure,bad job of stateing my question. As the vaccum increases it takes away pressure, which is way I was saying the vaccum seamed to increase as RPM was going up.
I have about 10=11 hg at MAP sensor(about 18" vaccum) at idle and at 2500
RPM MAP readings of about 8 or 9hg does't that show that vaccum is increasing?

Tuned Performance

iTrader: (92)

koeo the voltage output for the map will show you voltage output for that elevation's pressure. Engine vacuum goes down when your throttle blades open manifold absolute pressure rises.

http://en.wikipedia.org/wiki/Pascal_(unit)

Ronny

iTrader: (1)

I will translate.... KOEO = key on engine off

There is a list of acronyms here somewhere....It was a thread started that many contributed to...

Orr89RocZ

iTrader: (20)

What kpa values are you seeing? I dont recall seeing Hg as unit of measure for map sensor.

You usually see abit more vacuum at higher rpm and low loads with most motors than you see at idle. Quick free rev in neutral will spike vacuum to higher levels. Handy for increased foot brake power when at the track

Kpa should increase with rpm only if load increases with it. Idle free revs can show increasing vacuum which decreases kpa. My car idles 65 kpa but i can rev to 4000 and see 40's kpa. But if i am driving at 4000 rpm theres load on motor i would see 70-80 kpa

If your at wot and see a kpa that decreases as rpms climb you have a restriction. Say 98 kpa at 5000 but 94 kpa at 6000 rpm at full loaded throttle

Injected61

It maybe no load, some of my datalogs are on jackstands with trans in gear?
I have some on highway, steady speeds and I still see similar type readings.
700 Rpm-37.7kpa 800 rpm-35.4 1125 rpm-32.1 1225rpm-30.6
This is way I was wondering if air cleaner could restrict it enough to cause this or what another possible cause?? I will kept looking for problem and thanks for your info.

Orr89RocZ

iTrader: (20)

On jack stands no load that seems normal. On flat highway light throttle, also seems somewhat normal/plausible. Engine may reach a more efficient spot there and beable to produce more vacuum. Timing advance and air fuel ratio could play a role there.

Also noticed on my car colder engine temps dont always produce the same kpa readings compared to hot at some similar driving situations. Sometimes my 2000-2300 highway cruise can be 53-55 kpa when i idle at 60's. First gear cruise at 2200 could also be 60-70 kpa. Load changes everything

RBob

iTrader: (1)

Orr89RocZ, some scan tools will show the MAP value in Hg, as it is an English unit, as opposed to KPa which is metric. Put the scan tool in metric mode and MAP is in KPa, and vehicle speed is in KPH. Strange stuff.

Injected61, without a load on the engine the vacuum will increase as the RPM goes up. As the engine load is lower as the RPM increases (HP is going up).

RBob.