[Mk2] [Turbo] Overboost problem

[mr2haz]

I am looking to buy a rev 2 turbo.

My concern is that it used to overboost, (currenlty running 1 bar). This problem has been resolved by removing the pipe from the map sensor and blocking it.

Should I be concerned about this? Is it a standard fix or is it a car I should avoid?

[karammander]

if they have blocked the map sensor port on the rev2 this will stop the standard boost gauge from working therefore not using the stock fuel cut. the previous owner has not used a fuel cut defencer, removing the map sensor is a rather crude way of getting around this. i would plug it back in run standard boost and test the car. if all is good buy a fuel cut defencer of xxxx and your sorted.

cheers karam

[mr2haz]

He told me he blocked this pipe because the fuel cut defence was coming in. he also informed the boost was going over 1 bar before he did this which he could see on the aftermarket boost gauge. since he has blocked this pipe it no longer goes over 1 bar.

Does this sound right, or is the person either confused or trying to pull afast one?

[dansREV2turbo]

i would go with ...fast one

the turbo has probably been off in the past, and now the gasket (or downpipe if the car has one) is fouling the waste gate

[mr2haz]

Would it be a easy/cheap fix? I am a bit handy with a spanner.

It does have a manual boost controller if it makes any difference?

[dansREV2turbo]

i presume the car has a standard turbo?

if it is the waste gate fouling, youll need to take the down pipe off, itll be even trickier if it still has the stock cat on.

im quite handy with a spanner but i wouldnt do it (thats why i watched ryan and stuart do it at 2bar tuning when my car was overboosting)

if you plug back in the map sensor and take off the mbc. and just run it at actuator pressure, watch the (aftermarket) boost gauge. if it is slightly controlled up to around 4000rpm then overboosts more and more as the revs climb i would say its deffo a waste gate prob.

also, with it being a rev2 youd need to check all the ic hoses are tight and not leaking under boost (this covered up my overboosting problem for a while).

another thing to remember is that internal damage *could* have been done from overboosting.
a leak down test should show any signs.

[mr2haz]

Thanks, this will all come in very useful.

When you say a leak down test to you mean an engine compression test? Check it is the right compression and if the head gasket is ok?

What figures should the compression test give?

I did remove the cat pipe on my last mr2 turbo.

I beleive the car to have a standard turbo. It also has standard exhaust if that makes any difference.

[dansREV2turbo]

i dont know what the test figures should be.

ive never had it done, i think a leak down is like a comprssion test but is better.
sorry cant remember its late!

someone correct me if im wrong.

also just thought (i didnt think of this before as i had a new one put on my car), that it could be a faulty actuator?

[mr2haz]

If the actuator is faulty would it not underboost?

Would this not also be ruled out as the car does not over boost with the pipe from the map sensor blocked?

Sorry for all the questions but I need to decide if it is worth buying the car and get back to the owner with my answer.

[dansREV2turbo]

no, it can overboost aswell if its not opening properly.

if you plug the map back in and the car hits fuel cut, thats where if would have been running lean with it unplugged.

i wound probaby avoid imo.