9sectruck

iTrader: (9)

We just finished up and fired a 365" forged bottom end f1r procharger engine.
Cam specs are 239 252 623 624 114+4, (9.4:1)

I have changed map sensors re calibrated the map efficiency using hp tuners.
been tuning for a while and this thing is stumping me.. at 1000rpm it will only pull down to 100-102 kpa, touch the throttle nd rpm jumps to about 1300 and the map lowers to 80ish kpa... then slowly lowers rpm to 1k and kpa back to the 102 range...


we pulled the tube off the intake thinking the bov was not dumping enough air. went through the engine and check PR length to make sure we did not have a valve being held open.

pressure tested the intake (blow gun) through the hole drilled in the TB and can easily get boost to build with engine off key on.
can not hear or find any vacuum leaks any where...


any thoughts guys.. thanks

HexenLord

100-102 kpa means zero vacuum. Like your throttle is wide open. Your engine wouldn't idle at 1000 rpm with 100 kpa. Your readings must be off.

stevieturbo

Would agree.

Check your map sensor is scaled correctly.

Also, what size throttle blade are you using ?

98_SS

iTrader: (2)

90 mm blade and map is scaled correctly

RonSSNova

iTrader: (3)

Maybe pull the sensor off, connect to a vacuum tool like a mighty vac and see if it's accurate? Do the same just sitting in atmosphere, and add some pressure maybe from an air hose.

See if it reads what you expect.

What sensor are you using?

98_SS

iTrader: (2)

Did that it picks up vacuum and reads 105 with key on just doesn't change while running

98_SS

iTrader: (2)

Using a 3 bar map not sure of part number ecm is set up for 3 bar

stevieturbo

So you've confirmed map sensor reads down to say 30kpa, and at least to 105kpa as expected ?

When you log with engine running ( at least 10Hz ), is the map signal stable or all over the place ?

To have such low vacuum...ie none and the car idling at 1000rpm, it would indicate a major valve sealing issue, and it must be running pretty bad.

Compression test or leakdown test would do no harm.

98_SS

iTrader: (2)

Map moves maybe 2-3 points during idle nothing severe
yes can make it read 29 kpa at vacuum and above 105 when pressurized

98_SS

iTrader: (2)

It's not running bad but have not tried anything other then little throttle no test hits since we can't get vacuum it makes boost just fine

9sectruck

iTrader: (9)

We will do a comp. Test tonight.
Preload on all the lifters are about 3/4 to 1 full turn pass zero lash.
The car runs damn near perfect (via map adjusted at the 100-105kpa for fueling) no obvious problem while its running.

forcd ind

iTrader: (7)

use a mech vac. gauge and ck vac., cross it over to KPA-I have a chart if you need

9sectruck

iTrader: (9)

We will hook to the bov port as its a dead end for vacuum

HexenLord

I'm saying that the car cannot possibly idle at 100 kpa. 100 kpa is wide open throttle. The car would idle as if it had no throttle body. The reading cannot possibly be correct, not with a decent idle.

stevieturbo

As Hex says, the car cannot be idling normally at 1000rpm with 100kpa. It's just impossible.

98_SS

iTrader: (2)

Compression test done all cylinders are 147-150 nothing wrong there

9sectruck

iTrader: (9)

guys.....it idles just fine no hunting or anything.. iac is around 35-40 sits a pers at 1000-1050 rpm at 100-102kpa.

we will get a vid 2maro with the kpa reading/idling

samdogmx

iTrader: (14)

it may be idling fine, but the map sensor is not reading correctly if it says your at 100kpa

Rise of the Phoenix

iTrader: (27)

What does the kpa reading do when you give it throttle? Have you had it out on the street yet?

stevieturbo

Are you sure the map sensor is hooked up to the intake manifold correctly ?

Are you confirming any map readings with a mechanical gauge too ?