JamieMacdonald

Just fitted a boost guage to my MY97 UK Impreza Turbo in preparation for a Dawes device and also just to see how things are running.
I've noticed that the highest boost I can achieve is about 11psi, this seems the same in all gears and it stays bang on 11psi all through the rev range.
At Idle it's about -16, or is that 16 psi vacuum Not too worried about that anyway but what should that be.
Should I be getting more boost? The car has a Magnex centre section and backbox along with a K&N panel filter.
Cheers, Jamie

sasim

11 psi sounds about right to me, and it's probably -16 inHg at idle

Stuart

JamieMacdonald

OK, so it seems that 11psi is the norm, but I WANT MORE

When I get my dawes device, what level can I safely run at on the stock components? 15,16,17,18.....19 psi???? When does the ECU cut the fuel and is just below this level safe?
Or do I just have to 'plug n play'?

J

john banks

You'll soon find it. If you don't find it by 17 PSI it is not working and I suggest you go no higher. Dawes AFR is a good idea to monitor the mixture.

Katana

I've had ny car running at 18 psi. Turned it down recently to 11 psi and it seems slow as f**k. Still, I'll keep it this low until my AFR arrives.

john banks

Don't need to be quite so reactionary Katana? I won't have a heart attack if you run a bit more as long as you don't overtake me

JamieMacdonald

Katana, is your car a UK Turbo too? Does it really make that big a difference?
How do the characteristics of the car change when the boost is increased?
I like the sound of this
J

JamieMacdonald

I'm gonna reset my ECU now that I've used a couple of tanks of Optimax, just need to find those pesky connections under the dash!

One wierd thing I've noticed is that sometimes when I boot it in 2nd gear, the engine seems to hold back and the boost guage only reads about 5psi, then when I change into third it's fine! What is this and what does it mean!

Cheers
Jamie

Katana

Damn, missed this thread.

Mine is an MY93 WRX. If you're wondering what john banks is saying, well, boost is only part of the equation. I just want to get it higher for "***** sizing" purposes.

Its like doing something because you can.

jonmyers

My MY99 ran at about 12psi held, with little extra 'peak'. With the dawes device I wound it up to just over 16 psi before the fuel cut-out occurred. It now holds at just over 15 with no fuel cut-out. The device is very easy to adjust and set-up and gives an excellent boost <groan...!) to performance for the money.
Thinking of the Tek2 now though, so then it’ll be coming off.

mega_stream

MY99 runs 16psi peak, 14.25 held without any ecu or boost mods

ustolemyname??stevieturbo

iTrader: (1)

Jamie. If your car is a new impreza, I read somehwere that there is a strange boost reduction feature when nailing the throttle at a certain speed like that, to reduce noise from the exhaust for some weird government regulation. I think that if you put your foot down a little slower, ie gradually, it doesnt do it. Maybe someone here has more info on it?

JamieMacdonald

That sounds about right stevieturbo - what a stupid design eh?

mega_stream, is your car fairly standard? I rarely see over 11psi in my MY97 but people have told me this is ok (see above). Either mine is too low or your's is too high, or the boost guages are well inaccurate!

Jamie

Marc R

Hi Jamie, my car is uk MY97 and car holds 0.9 bar which is 13.1 psi and peaks at 15.7 psi. WOT in 5th for peak. Mods are blitz filter, forge VTA, magnex cat back running on optimax. Have dawes to fit but waiting for Afr before blowing stuff up. MY97 has boost of 0.9 bar according to subaru FAQ, not sure if this is held or peak, think it is held with fuel cut set at 1.2 bar which is 17.4 psi. Hope this helps a bit, I will probably go for 16.5 psi held as long as peak isn't above fuel cut as don't want to fit a defender.

Marc

cube

Jamie,
11psi does sound low for a MY97, I had a boost problem (only 8psi max) last year that I discovered after fitting a boost gauge to my MY97. After rectifying it held 13-13.5psi and peaked at 15 after fitting a full decat, before the decat peak was 14-14.5.
Your figure sounds like the kind of boost developed by the TD05 used upto MY96.

Cube.

JamieMacdonald

Hi Cube, what was the cause of your low boost? Sorry to be thick but what is the difference between peak and held? My car usually peaks at 10-11psi (on WOT) and stays at this all the way up the rev range.
Would it be a good idea to see why my boost is low before fitting a Dawes device?
I did an ECU reset today and the check engine light was blinking normally i.e. no problems found.

Jamie

cube

Hi Jamie,

My low boost was caused by the previous owner having fitted a bleed valve incorrectly. Stock levels were returned after removal.
I had the car for a while with it like this and it's disappointing performance raised my suspicions.
Held boost is the sustained boost typically easier to read in 4th or 5th. Peak boost is the initial surge that the turbo can't maintain. If your peak and held are so low and the same, then I would have it looked at, you may have a contaminated wastegate solenoid, or the tubing to it may have oil deposits in them which apparently is common, especially after servicing when the engine may be overfilled with oil.
Let us know how you go on.

Cube.

mega_stream

All mine's got is a Scoobysport downpipe, HKS Hiper system, P1 intercooler. Readings are coming from Defi

JamieMacdonald

Cheers for the info, I think I will get some brake cleaner to clean out the Wastegate solenoid, is it best to do this with the engine running? I also read something about connecting the 'under dash' connectors at the same time....

Jamie

cube

Engine off, but yes connect the black and green connectors and turn on the ignition, you may have to depress the accelerator as well, and the solenoid will chatter away like a good 'un.

Cube.

JamieMacdonald

Sorted! Cleaned the wastegate solenoid and boost control valve etc. now peaking at 15 psi and holds 13.5 psi which is a bit more like it!
Didn't expect it to be something so simple!

I think I'll still get a Dawes, if only to get rid of that stupid noise reducer regulating thing.
One more thing - when people recommend max boost pressure e.g. 17.5 psi with a Dawes, is this the peak or held boost?
I'm hoping it's the latter

Jamie

Richard Curtis

Jamie,

I have a dawes on my UK 97, with s/s downpipe, fully decat, similar spec to you.

What you will find is that the peak and held are virtually the same, I don't get any overshoot at all.

btw. I've got mine set to 15psi with no probs at all, if you go much above that you will hit fuel cut (its lower on the earlier cars, pre 99).

I'm fiting a unichip with fuel cut defender on the 17th to up the boost to around 17-18psi. If interested I'll try and get dyno runs before fitting the chip and post them to show the power your likely to achieve.

Rich

RT

Jamie, I've heard that a possible drawback to the Dawes is the half-throttle boost properties. I've never used it so I can't comment further. Perhaps you'd want to check it out a little more.