terzo42

been using optimax for 4 months or so and about every 10-12 tankfulls i get a tankfull that causes overboost every time im on full boost,when the tank is empty i fill up again and the overboost stops,this doesnt happen on any other fuel so the question is why does it happen and does anyone else get it?

Flat 4x4

NO, but my engine did melt down at a track day once and I still have my suspicions on the factors involved in it, as everything else was as it should have been - best oil, long cooling down, no over-revving etc.

Anyway, paranoia to one side, I'm one of the few people who still remains unconvinced by Optimax over BP or Esso SUL

chrisp

Not had any problems with Optimax. What other mods do you have, VTA dump valve ? decat ? induction kit ?

terzo42

only mod is full decat but that is just recent i was getting it on the standard car before that and it is deffo the fuel that causes it pretty wierd eh!

chrisp

Have you got a boost gauge ?. It maybe the optimax is allowing you to run more advance due to the high RON and it is overboosting slightly. I guess you only get the overboost in 5th ?

terzo42

no boost gauge and get it in fourth aswell,car also accelerates faster until it boosts why only some tankfulls do this is beyond me m8

Trick

might be a daft question - but what are the symptoms of overboost?

chrisp

Overboost liking hitting the brakes hard when on full boost, very scarey. My car has never done it but been in a turbo car that has and you are peeling yourself off the windscreen

You may find its only certain tankfuls because its the weather which is causing it. If its a warm day then the car wont boost as much. Cool damp day and the air charged affect is like having water injection fitted and you will get more boost. This why people think they have an extra 30bhp on a cold day than a hot, because effectively they may have .

I would get it in and checked, the decat wont help the situation as the turbo spools up quicker and may make an overboosting problem show its head more often.

I am definitely not a mechanic and not had the problem on my own car so I may just be talking crap . If it was my car I would seek specialist help and thats the best advice I can give to be honest.

terzo42

hi chrisp just came back online the car was checked out by stan palmers when it first started and they found everything normal and no fault codes ,it does it in all weather conditions and was doing it before decat,there must be something unstable or summat with the optimax cos as i said its only on optimax it happens and only every 10-12 tankfulls its bloody annoying m8

TonyBurns

iTrader: (3)

Have you cleaned out your solenoid?
Getting excess oil in there can give the same symptoms as overboosting (i had this problem) but in some cases the full decat will also push you closer to the line when it comes to overboosting.

Tony

terzo42

ye m8 palmers cleaned the solenoid,just seems to be occasional optimax tankfulls

chrisp

Without a boost gauge it going to be very difficult to monitor it.

I know my car use to run 1.2bar but after my recent 30K service and a ITG panel filter was fitted rather than the paper one it now occassionally boosts to 1.3bar, I have the boost alert set to 1.2bar. Maybe its the filter, or plugs, or the overall service etc but the car definitely pulls better, runs better and boosts slightly higher.

Without the gauges I wouldnt know what it was doing. My mates think they are a bit of fun and flashy but actual very useful to know whats going on.

Flat 4x4

Isn't this obvious or did you ignore my reply ?

Use Super Unleaded instead of Optimax for the next 10-12 tanks and if it doesn't overboost you will have a solution.

The repairs to my car cost £2500 under warranty but had nothing to do with the fuel - probably.

StickyMicky

i think my 97 wrx hit the fuel cut thing the other day

was very starnge as it was in 2cnd gear coming out of a roundabout
the tank was half full, so no fuel surge

did a ecu reset that day and i use optimax and a bottle of millers, so i wasnt expecting it but it just died for a split second and carried on

very strange