k9any

Hi People

I have a MY97 UK Wagon, my only mods are stright through de-cat HKS zorst, Blitz induction and Dumpvalve. Since I have solved my 7PSI max boost problem by ordering the correct pipe with restrictor my car has been running very well and very quick. I am hitting 15PSI on max boost and it holds this to redline.

Today the weather over hear was cooler than previous days and i was returning from Preston and decided to go over the top via the M65......on a long straight i floored it through the gears.....when i put it in fifth and floored it the car picked up well and then it just felt like all the power had gone and i'd hit a brick wall...a split second later the power was back.

Is this the 17.5PSI safety cut off?

I didnt know i could hit that sort of boost with my modds.....

Is it time i invested in a fuel cut defender?

anyone had similar experience?

Ray

Leviathan

Overboost & fuel cut
to much boost.

nom

Better to fix the problem than fit something that avoids it!
Overboost; something to do with holes in the right place, I think
JB's the expert on this one, I think. I cheat & use the ECU instead He was dabbling before he got into that stuff & learnt lots of new & exciting ways of saving cash & being a real Scots

Boro

iTrader: (1)

Overboost in simple terms is where the boost pressure produced by the Turbo exceeds a predefined maximum. Once the limit is reached the ECU cuts all power to the engine for a fraction of a second. The result of this when accelerating hard in second gear feels like running into a brick wall

Or a more detailed explanation is:


The wastegate is held shut so that boost is generated and when the desired boost level is achieved the wastegate is then opened. However this is mechanical stuff controlled by electronic stuff - electronics can react quickly whereas mechanics can not.

What you find is that when the wastegate is opened the turbo is still accelerating, so for a moment the boost continues to rise until the turbo speed falls. This moment of higher-than-desired boost is overboost. Complex boost controllers try to "guess" when the desired boost level will be reached and then open the wastegate in time, so as not to overshoot it.
Causes of overboot include the T piece clogging up with oil. Also if the orifice (brass hole restrictor) is placed in the wrong line, it will also overboost. Depending on which model it is, it should either be in the line from the turbo to the T-piece or the pipe from the solenoid on the right side of the struct tower to the inlet manifold.

97 98 cars seem to suffer this the most. The hoses from the wastegate can be cleaned and the problem still comes back. Also dealers have removed the restrictor that is in the line to the wastegate and fitted a larger holed one, this lets the car boost to a lower level. Problem solved. Some dealers are drilling the hole slightly larger. Beware they do not drill the hole to large or your boost will suffer.

Paul aka Boro

k9any

Hi Boro

Thanks for the info....judging by what you have said i may have put the pipe with the restrictor in the wron place.

MY97 UK.....I have the T piece with three pipes going off it.

1. The pipe on the left hand side of the T piece goes to the boost solonoid.

2. The pipe on the Right hand side goes to the Actuator (i think)

3. The middle pipe on the T piece is the one which i replaced with the restrictor in it and it goes to the inlet manifold (i think)

Does this seem right to you?

Ray

k9any

even if this is the wrong place to put the pipe i love the extra boost created, and it has only hit fuel cut off once.

If my A/F meter is reading rich and the KnockLink reading is ok i think i will just invest in a fuel cut defender and raise the fuel cut off slightly.....good idea?