2005 STI Turbo Problem - Help

Did you put anything less than 97 RON in it?

R

That 'wirr' could be a not working or sticky bov. This could explain the low boost at low gears. Maybe just a loose vacuum line of the bov.

SFC

I've been putting Sunoco 94 octane in it... Which I think is more than fine.

-Bryan

SFC,

That is something I was thinking of, it feels like there is a leak somewhere in the pressure of the turbo somewhere.

I was thinking (in my small knowledge of turbo's) that I thought the BOV kept the pressure in for a short period of time to keep power on tap, and to build some boost pressure prior to jumping on the gas so that the power will come up quickly.

It also felt like the turbo overall didn't have as much boost pressure overall as in the past, even when it was working.

Am I correct in how I'm describing the role of the BOV in the turbo system?

Thanks, Bryan

From: "SFC" Subject: Re: 2005 STI Turbo Problem - Help Date: Monday, July 26, 2004 1:24 PM

That 'wirr' could be a not working or sticky bov. This could explain the low boost at low gears. Maybe just a loose vacuum line of the bov.

SFC

The BOV allows excessive pressure to "blow-off" when you take your foot off the gas (during shifts, when braking, etc, etc..). If it is stuck open it will allow the boost pressure to be recirculated back to the intake instead of going into the throttle-body. In other words it would act like a leaky intercooler hose in some respects which would explain the lack of boost that is building AND why it feels like there is less power being made.

I would start by having them check if the blow off valve is stuck open and then maybe checking to see if you IC hoses maybe came loose or if, like someone previously mentioned, that a vacuum line came off somewhere.

I have a WRX and the manual tells me not to put anything less than 95 RON in it, it even says this on the fuel door. I normally use 97 and 98 RON. I would expect an STI to run at higher boost therefor requiring higher ron fuel to cope with the higher compression.

Using a low RON fuel does not allow as high a boost pressure due to the fuel igniting before the spark. Id get the tank full of 97 at least then get an ECU reset done at your dealer. Your timing may have been retarded excessively to deal with the low RON fuel, you may also have damaged the engine.

Ross

Doubtful you damaged the engine. A friend's 01 Passat 1.8T has used nothing but 87 octane since new. Now at 120K no engine problems due to that. Many many other problems but none octane related. No manufacturer would produce an engine that can be damaged by wrong octane. They would replace too many under warranty.

You want 97+ in there or you are just gonna be getting knock and the ECU will whack back the timing and make it as slow as a pig - im forever getting that when trying to run my GTFour on supermarket 95. The difference is phenomenal.

J

And to follow up on what i said - they also dont like the fact that you have hot intake temps due to the car sitting and heat-soaking the intercooler, so the ECU will limit the boost until the IC cools down, which can take a surprisingly long time > 15 mins on my car.

I ran some tests recently - my standard airbox reached >50C when stopped for

3 minutes, and never got back below low 40s in 20 miles of off-boost driving after that. And thats before the turbo and IC. J

Good explination of the bov function. It could also be a ruptured membrane of the bov. Bosch (plastic) bov have a bad rep of this. Simple test: just suck on the vac. line which goes to the valve, if you can't get any vacuum it's the membrane.

SFC

"WRXtreme" schreef in bericht news: snipped-for-privacy@corp.supernews.com...

Where the heck do you guys get 97+ octane? The highest I can find is 94 around my neck of the woods (Central Ohio).

I think you might have a bit better performance, but can't imagine an engine 'NOT' running right as every idiot would be in getting their car serviced.

Have been running my 2.8L 5Valve V6 Passat for 90K miles on 92 Octane and haven't ever had any engine problems or knocking. Runs like the day I bought it...

Sorry, you are US - here in the UK we can get up to 98.9 ;) Thats what my baby runs on, but at 6.25$ per imperial gallon its not cheap!

You want to check in the manual to see what it is meant to be run on. Mine is supposed to run ok on 95 but it really doesnt for anything other than grandad driving.

Its not turbocharged, which makes allllll the difference to knock. And generally you cant hear knocking that the ecu can so in all honesty it could be and you just dont know it.

But since it runs fine in the first place then gets worse I'd look at my other answer to your last post - it may be a combination of the two.

Try some octane booster in a tankful and see how much nicer she feels.

J

In the US, we measure with the (R+N)/2 method, while most of the rest of the world uses RON (the R part of R+N).

I don't have a conversion handy, but my '02 WRX wagon with the 2.0 turbo requires 91 R+N/2 gasoline. Anything rated above 94 in the US is fairly exotic race gas. In Phoenix, the highest octane I can find is 91 - and we're only about 1000' (300m) above sea level. In New England (where I'm from) you can easily find 93 and 94 octane as premium.

The RON only rating gives the fuel a numerically higher octane rating - so I think WRX's sold out of North America require 95 RON which is about the same as 91 R+N/2 fuel.

Your RON numbers aren't the same as our octane numbers here in the U.S. I can't even *get* Sunoco 94 in the boonies where I'm at -- the best I can find is 93 octane. AFAIK, Sunoco 94 is the highest-octane fuel you can buy in the States without going to leaded race formulas or adding your own octane boosters. The manual for my Forester requires 91 octane or higher. While I haven't read the STi manual (not fortunate enough to own one), I'm confident that the fuel he's using is fine.

- Greg Reed

I'm not sure we are all speaking the same language. I think that American 93 octane is equivalent to our (Godsown's) 98 RON.

Or something like that anyway

OTOH I could be wrong.

-- GW

You don't need 97 Octane. For one thing, in North America, octane is measured as R+M/2. They are talking about RON; which is the Research Octane Number (and its how they measure it in Britain). It is always higher than the R+M/2 value. The MON number is usually lower than the RON, which is why R+M/2 (also called AKI or Anti-Knock Index) is somewhere in the middle. 98 RON is approximately equal to 93.5 R+M/2. The owner's manual recommends 93 AKI (which is R+M/2) so you should be fine on Sunoco 94. However, Sunoco does contain some ethanol, and though it shouldn't cause a problem, it will produce slightly lower power than 94 AKI gasoline.

I suspect, as one poster suggested, that it could be you BOV, or you may have a leak in the downpipe.

actually, its RON+MON/2. Where RON=Research Octane Number and MON=Motor (I believe, been told it mean Mechanical as well) Octane Number. It is rare to find anything higher than 94 octane in US pumps using this method of measuring octane. There are a few stations (Holiday in Minneapolis/St Paul for example) that sometimes carry 100 octane street legal race fuel at the pump.

You are right to assume that 95 RON is approximately the same as US 91/92 octane fuel.

has a pretty good explanationon how this works, it also goes into detail on how to use Toluene as anoctane booster. I am not endorsing nor shooting down this idea, like anyother "mod" you do to your car or fuel, you are proceding at your own risk.I personally use it in my car when I run high boost at the track, but othersmay not feel comfortable using Toluene in their vehicles. Sorry forhijacking this thread, this was the first article I could find thatexplained RON+MON/2.

Just an add on... this stuff does work well ,but it is pretty hard on the rubber parts of your fuel system ..