Today I took my car to have it rolling roaded at a garage i've used loads of times before.

 

To give you an idea my car is a 1992 JDM TT Manual Slicktop. It has got basic mods such as apexi filter, kakimoto exhaust, blitz ecu, apexi avcr bc, ngk plugs.

 

I setup the boost controller with a friend the other week who had installed a skyline engine into a 200sx so was pretty confident with installing an apexi avcr.

 

The one thing that baffled him a bit was disconnecting some plugs in the engine bay (is this something to do with the stock safety boost cutting in)???

 

Anyway

 

1st run ) 324bhp @ 4820rpm & 364 lb.ft (this boosted to 1.04 on my avcr)

 

The guy that was doing the r/r noticed there was 2 plugs disconnected in the engine bay either side of the inlet manifold (1 on the left 1 on the right).

 

He tried connecting the one on the left (passenger side) and doing the power run again.

 

2nd run ) 358bhp @ 4870rpm & 394 lb.ft (this boosted to 1.15 on my avcr which i was quite worried about as all we did was connect 1 plug up????)

 

We disconnected the plug again.

 

3rd run) 336bhp @ 4940rpm & 372 lb.ft (this boosted to a safer 1.04/5 on my avcr)

 

Anyone know why this is happening and what are those 2 plugs which have been disconnected? We didnt try connecting both of them back up...

 

I have recently been having a problem with juddering below 3krpm when the car is cold and thought it was an oxygen sensor. I did an ecu diag check and it came back saying the left oxygen sensor was not working as there was no flash at all from the engine light or ecu led. The right one was working fine.

 

The mechanic who did the r/r seemed to think that the 2 plugs which have been disconnected were the lambda plugs?

 

I can provide pics of the plugs if needed.

 

Any help/advice would be appreciated.

 

Chris

Sounds like you may have disconnected the o2 sensors instead of the stock wategate selenoids, if so car would be running very rich.

The ecu diag check found the right hand side o2 sensor to be working properly though?

 

Shall I go out and take some pics of the plugs which are disconnected?

Those two plugs weren't the connectors for the wastegate solenoids were they?

It sounds like you disconnected the safety boost solenoids, these limit the boost on the engine when knock is discovered, keep your boost to one bar or you will knacker the turbos/engine!

I have got the boost set at 1 bar on my avcr though and the boost was going safely to 1.04 bar everytime. But when we connected this plug on the left which had been disconnected, it automatically boosted to 1.15 bar without any adjustments to the avcr.

 

Picture from left side (passenger)

 

 

Picture from right side (drivers)

 

 

Also, is that the ptu thats cable tied to the inlet mani on the first pic?

Those look like the correct plugs to me. Also that device is the Throttle Position Sensor.

Anyone got a pic where the PTU is then? Wanted to check if its been upgraded or not

Those are the right plugs to disconnect.

So my car is making 336bhp and 372 lb.ft @ 1.04 bar.... is this about correct?

 

I was hoping a wrong plug had been disconncted because i've only recently started to experience the juddering below 3k rpm whilst the engine is cold (since the boost controller was installed). Maybe it is the left o2 sensor which has gone afterall.

power seems right, maybe should be a bit higher at that boost. You've disconnected the correct plugs, and reconnecting them will in turn give you more boost as you discovered.

 

The juddering could be a small vacuum leak

 

re the O2 sensors, they're not used when the engine is cold so that's not what's causing the juddering