12PSI Boost

[CoolPC]

I got a pod filter for the Stagea the other day and when I was putting it in I thought I'd also stuff around with the boost control a bit. In the end I found out that if I bypass the boost solenoid (the standard one) I get a nice increase in boost to 12PSI. Car pulls nice and hard, it's not spiking, just a nice curve up to 12PSI. Not too bad really!

Edit: Am a bit worried about my ceramic wheel though, I can't remember what the max boost for these turbos is? Anyone have an idea? I searched the forum but couldn't find what I was looking for...

[Jay95R33]

Hmmm, I thought bypassing the stock solenoid would keep it on the low (5-6psi) level..

What did it run stock?

J

[Sydneykid]

I got a pod filter for the Stagea the other day and when I was putting it in I thought I'd also stuff around with the boost control a bit. In the end I found out that if I bypass the boost solenoid (the standard one) I get a nice increase in boost to 12PSI. Car pulls nice and hard, it's not spiking, just a nice curve up to 12PSI. Not too bad really!

Edit: Am a bit worried about my ceramic wheel though, I can't remember what the max boost for these turbos is? Anyone have an idea? I searched the forum but couldn't find what I was looking for...

My recommendation is the usual 10 PSI. :Paranoid:

[mad wagon]

stock it does 5psi, and quite sure max for the stockies is 13psi.

why stuff around with the hoses when u can get the t/s gbcv for $100.

got mine on 8psi to keep it tamed and not guzzln but on w/e its on 11 and the tee works good.

[Sydneykid]

stock it does 5psi, and quite sure max for the stockies is 13psi.  

why stuff around with the hoses when u can get the t/s gbcv for $100.

got mine on 8psi to keep it tamed and not guzzln but on w/e its on 11 and the tee works good.

Fantastic, so I can tell all my mates to drag you off during the week? :whip: Personally it would drive me crazy, I prefer to use the throttle to control speed and fuel cunsumption, after all that's what it's there for. :burnout:

[mcnamg]

id prefer an ebc with a track boost level and an everyday boost level then i could drag anyone i want with the touch of a button.

[Sydneykid]

id prefer an ebc with a track boost level and an everyday boost level then i could drag anyone i want with the touch of a button.

Except when you forget to push the button. How embarasment :Paranoid:

[mcnamg]

yeah true you could look very stupid when a car that you know you can beat smokes you and you look at the boost controller and think to yourself aww crap

:)

[Sydneykid]

Now that you mention it, it's raining cats and dogs here, an SS ute a couple of weeks ago, a GTS last week, where is that annoying bloke in the XR6 turbo..... :Owned:

[CoolPC]

I know you can get a T/S boost controller for $100.- but I'd rather go without a boost controller than buy T/S stuff because I've always had bad experiences with them. If anything I'll go a full EBC with dual solenoids, i.e. E-01 or AVC-R.

Anyway, driving the car all day yesterday, it doesn't hit 12 PSI boost (more like 11 actually) unless I really give it some stick but if I do it does have some serious nuts, enough to put a grin on my face and it wasn't able to do that for me before, me being used to the GTi-R and all. It doesn't seem to be leaning out at all, if anything it's running a bit rich - as expected, but that's just me going by the colour of the spark plugs and exhaust fumes looking/smelling rich. Also get the odd pop through the exhaust.

I reckon the boost is ok the way it is, just need to get an S-AFC and whack it on the dyno to make sure the A/F is right, until then I'll hook the solenoid back up just in case it is leaning out afterall.

One thing that's annoying me a bit is the induction noise, it's about twice as noisy as in my GTi-R and the BOV sounds like an atmo venting one...

How come you guys mention stock boost of 5PSI? I thought it was 8PSI, but limited to 5PSI until around 4500rpm? Even without the pod filter I was getting 8PSI when going flat stick...

Also, bypassing the solenoid doesn't reduce boost, it increases boost. The solenoid closes a bypass (i.e. a leak) in the hose coming from the intake and going to the wastegate actuator, i.e. the hose that tells the wastegate actuator how much pressure the turbo is currently making. When the solenoid isn't bypassed the wastegate actuator receives more pressure than if it is bypassed (and as such the waste gate will open sooner = less boost).

Technically all that should happen with the solenoid bypassed is an increase of boost to the 4500rpm+ level, so it should have ~8PSI. I'm guessing because of my pod filter and exhaust I'm seeing 11PSI because there are no other leaks... or possibly the solenoid never fully opens and always reduces boost a bit and now it can't do that anymore.

Anyway, the point I was making is that the boost is very much solid, not spikey or anything, in fact it's as stable as it is in my GTi-R with a Profec B-Spec, if not even more stable! I really don't see why I should have an EBC at this stage simply because I'm getting the perfect increase for tuning already, rather spend the money on an S-AFC and FMIC. And as SydneyKid said fuel consumption can easily be regulated by how much you put your foot down, but I checked and even on 11-12PSI all day yesterday I used around 15L/100ks driving moderately hard (had the gf in the car ) whereas before I was getting around 14L/100km.

[Sydneykid]

OK I'm confused, this is how I see it.....

The wastegate spring rate has to correspond to the lowest standard boost setting. The solenoid then bypasses some airflow to get more boost (than the lowest) when the ECU says it's OK.

When you disconnect the solenoid, only the wastegate spring controls the boost, so you get low boost all the time. Because that's what the spring rate is in the wastegate actuator.

So

wastegate spring rate = 5 psi

up to 4,500 rpm the solenoid allows full airflow (boost) to the wastegate actuator

so the wastegate opens at 5 psi

over 4,500 rpm the solenoid bypasses some air flow to the wastegate actuator

so the wastegate opens at 8 psi

The way I see it the only way CoolPC is getting 11 psi, is if his turbo is equipped with an 11 psi wastegate spring.

Or have a I missed something?

[Jay95R33]

Yepp, that's it SK.

I'm 99% sure that the setup in the Stagea's is the same as the setup in the R33 GTS-t's.

At one stage I had a hose going straight from the inlet crossover pipe to the wastegate. Once I did that Idodn't see anything over 5psi.

CoolPC - I think your one of the lucky bugga's with a 11-12 psi wastegate.

J

[CoolPC]

No I don't. You guys need to have a look at where the hoses are going on the solenoid!!

The solenoid is connected with one end to the hose coming from the plenum and going to the wastegate actuator. The outlet of the solenoid is connected to your intake (i.e. it vents back into the intake as it should).

If I bypass the solenoid, I *always* have a small leak going to the intake, hence the boost increases, just as if I had the solenoid set to all the way open.

If I hook the solenoid back up then the solenoid will close that leak (my guess is close it a little for 8PSI, close it all the way for 5PSI), thereby reducing boost.

Got it??

You guys are saying the solenoid's function is to introduce a leak, but it isn't. The function of the solenoid is to reduce/close a lsmall leak that's always there.

Have a look at the hoses, you'll see

[Jay95R33]

I think I'm picturing your setup wrong... (it is a Friday and my brain slows down ).

So you've got a T piece there instead of the soleniod ? Is that right ?

So from the inlet crossover (plenum) pipe you've got a hose going to a T piece, then from the T piece, one side goes back into the intake and the other side goes to the wastegate ?

What I'm getting confused about is that heaps of blokes have hooked the solenoid up so it's always open (give it constant power) and only getting an increase to 8psi.

But this might be a new method of increasing your boost on the cheap

J

[mad wagon]

just get frigen boost tee, the t/s got a little diag., very easy to follow and connect yaself, and just adjust the knob to what the boost gauge is sayin when you give it flat stik.

[CoolPC]

Mad, I already told you what I think of T/S stuff, I just don't have much faith in it, you get what you pay for. I know how boost control works, I've been working on turbo cars for many years, I don't think I'd need a diagram to hook up a simple bleed valve. Your bleed valve does exactly what I've done, it introduces a small leak into the plenum->wastegate actuator connection.

I do agree with you that a boost controller of some sort is a better alternative, especially because the weather is now getting quite hot and I'd rather turn the boost down to exactly 10PSI rather than somewhere between 11-12PSI because I really don't want to risk detonation in my 50,000km motor

Here's a diagram of the stock RB25DET solenoid setup:

I appreciate the fact that ppl have grounded the solenoid to achieve 8PSI boost all the way but that's because the solenoid has a restriction inside it even when it is all the way open.

[CoolPC]

[...]

So from the inlet crossover (plenum) pipe you've got a hose going to a T piece, then from the T piece, one side goes back into the intake and the other side goes to the wastegate ?

[...]

J

So do you, but yours has got the solenoid between the T-piece and the intake which I removed on mine.

[Jay95R33]

Cool, I understand now

So instead of going from the T piece through the solenoid then back into the inlet, you've just gone straight from the T piece to the inlet.

Your a brave man, not saying that you don't know what your doing, but the first thought in my head would've been 'hmmm, what happens if it bleeds too much air...'

But I suppose good throttle control the first time you try it would help

J

[CoolPC]

Wouldn't be doing this without a boost gauge, that's for sure...

[DAVE CONNOR]

Nice discussion, I've been trying to work it all out for days over here in the U.K. I had a replacement engine put in, and the dashboard turbo meter was stuck on -3 so I thought there was something wrong with the way the solenoid was piped in. I,m gonna try to bypass the solenoid or mess with the voltage ( will it be the black or white I earth! I'll have to wait and see.) If any one could explain why a boost gauge running from just before the intake manifold is also showing a negative on tickover, it would be helpfull. When I put my foot down, the gauge increases to a positve, but I feel that it should start from zero. Thanks, enjoy the sun. ( Dave Connor )