SCOOBYD00

Jap V4 STi runs 1 bar usualy on full throttle or just over after decating - however spikes to around 1.4 quickly then back to 1.0 - only really happens under hard acceleration.

Is this normal - could it cause any damage - should I consider boost managment to stop this?

Any thoughts welcomed

Cheers

dr_jones

iTrader: (1)

If you have a two port solenoid then this is relatively common.
I have a V3 JDM Sti and was seeing 1.3 spike then down to a steady 1.1 bar - I sorted this by installing a variable restrictor in place of the small brass job that you will find in the actuator line (the same can be acheived [albeit relatively difficultly] by drilling the OEM restrctor orrifice out by microscopic amounts.

Anyhoo the upshot of this is I anc now controll the spike at will by adjustment of this valve.

zhastaph

Mine does exactly the same, though not as high as 1.4 bar. The problem is caused by the fact that the turbo spools up much quicker and much easier when the cat is removed, it then overshoots the target boost of the vehicle.

The likelyhood of the car detting when it boost spikes is high, mine does. A KL will show this. And if it is detting, then Yes it can damage the engine. If you have a KL and no activity on it then you should be fine. If you don't have a KL then assume it is detting and take it easy.


There are number of options;

1. I'm going for a Dawes on mine, this is a manual boost controller and will stop this problem as it will take control of boost away from the ECU. These are cheap, about £45 from JW Racing (if it ever turns up ). Other manual boost conrtollers are also available, some of them are electronic and adjustable from withinside the dash.

2. As DR Jones says, drill the restrictor out just before the T piece in the boost control line. Though you'd have to be sure of what you are doing as a 2 big a hole will lower your boost. I've got to admit I do like the idea of his adjustable one.

3. A remap.

SCOOBYD00

Thanks guys,

For such direct support! I did not expect such concise response - sweet

Going to order a Knocklink this month. Then I'll either cry or conisder a wee bit more boost.. howver 1 bar is more than enought through the rear wheels of the type r!

Cheers

red wrex

Hope you dont mind if i butt in, but my friends uk turbo has been decated and i noticed it goes up to 1.5 bar and then slowly lowers to 1.25

sounds like its spiking, where would he need to adjust to stop it detonating on an MY98

SCOOBYD00

1.25! Standard UK car should not run that much boost surely! (need back up on that one) My STi runs 1.0 maybe 1.1 but spikes at 1.4ish after decat (less restriction so the turbo spools up faster as I have learned)

I tried a jap WRX MY95 than only ran 0.7 Bar - when pushed to 0.9 started to cough!

Make sure the boost gauge is correct & get it checked over before it gets expensive IMO

What do standard UK spec MY98's run?