Weird Boost, Sometimes Higher, Sometimes Lower

[nuffsaid]

Hi all

I noticed that even on cool nights, sometimes my car boosts to 0.55kg/cm, and sometimes to 0.7kg/cm

Temperature is about the same, but sometimes it boosts higher, sometimes lower.

I dont know why its happening, any suggestions? Its a 34 GTT

[shif_tea]

what sort of boost controller do u have?

[nuffsaid]

No boost controller at all.

Pretty much stock except for full 3 exhaust and panel filter.

[nuffsaid]

I noticed that when the oil temp is relatively low, like 85 degrees and under, it can boost to 0.7km/cm.

However when the car is driven for say 25mins and more, the oil temp gets to 92degrees (day or night doesnt matter) and usually stays at that point.

When it gets to 92degrees, the boost level cant get past 0.6 kg/cm. Please note that I am reading all this out of my stock GTT boost gauge

Why is this? Because of all the heat in the engine bay, does the SMIC intercooler suffer from heat soak? and so cant boost as high? However, I can drive for say 15 minutes without hitting boost (some time for the intercooler to cool) and then when I do hit boost, it still only gets to 0.6.

1) Is it the SMIC? and is it supposed to cool down when driven without thrashing?

2) Is my factory boost gauge reading wrong perhaps as the car gets really warm?

Edited March 11, 2006 by nuffsaid

[Miller the hoon]

I noticed the same when i had no fmic

had it installed with no real rwkw gain but it boosted the same every time and held it better mor driveable

james

[nuffsaid]

Forget about the oil temps guys.

Thrashed it at 80 degrees, same boost level.

Engine bay is quite hot, I guess thats normal for these cars. I have removed the turbo heat shield though since I've installed a dump pipe.

Would this affect it?

Ill try giving it a hit in the morning, I bet it will get to about 0.7kg/cm.

[Sydneykid]

Forget about the oil temps guys.

Thrashed it at 80 degrees, same boost level.

Engine bay is quite hot, I guess thats normal for these cars. I have removed the turbo heat shield though since I've installed a dump pipe.

Would this affect it?

Ill try giving it a hit in the morning, I bet it will get to about 0.7kg/cm.

Get a decent aftermarket boost gauge, the standard map sensor is engine bay temp sensitive.

cheers

[nuffsaid]

I gave it a hit this morning, it made it to 0.7km/cm.

So perhaps the MAP sensor isnt reading fully right. Is it bad to remove the exhaust manifold heat shield?

Unfortunately the exhaust workshop who fitted my dump pipe has my heat shield (which he probably threw away), he recommended taking it off because it can cause rattling sounds if it touches the dump pipe. He has installed heaps of dump pipes and says that its normal to leave it off.

Edited March 12, 2006 by nuffsaid

[Abo Bob]

Nothing to do with the boost but get that heat shield and put it back on. Your exhaust guy is lazy.

[nuffsaid]

Thats if he hasnt thrown it in the bin yet! How important is it for me to get it back on?

Spoke to a couple of places, they seem to think its not necessary.

Edited March 14, 2006 by nuffsaid

[illusiVe]

not necessary, but helps keep temps down.. since its on the same side as the air filter..

[nuffsaid]

Got the heat shield back on and proper muffler to suit my exhaust, boosts normally now.

I think it was the crappy 2.5" muffler and heat soak causing boost to not reach its max.