Tips on finding missing boost

[-Nemesis-]

So i've got my set up running and thought i'd start a new thread for this question.

I'm running a P1SC Procharger, it runs through a 3" pipe to the intercooler (2 90 degree bends) than up into the AFM, then a 3.5" pipe to the throttle body (I did this because the AFM outlet is 3.5" and the TB is a bit bigger than 3")

My charger is running a 3.40" pulley, my set up is much the same as spf_lexus on here, who is running a 3.60" pulley. He has managed a comfortable 7psi on his, but i'm struggling to hit 6psi with a smaller pulley.

So anyways, just wondering if people have some tips on where the boost could be going?

I've removed the breather > throttle body, though I admit the hose blanking the TB is a little dodgey (only has the standard spring type clamp on it.) All the little vacuum hoses remain in place, don't seem to be popping off.

Anything I missed? Any tips on tracking leaks? I tightened all the intake clamps again last night.

 

[cribbj]

You could try blanking off both ends of your system, from the SC to the TB, and pressurising it with a bit of air and check for leaks using soap suds around the connections. Many of us with Supras have had to do this after installing a new FMIC or other intake mods.

Expanding rubber plugs used for sealing plumbing piping are good candidates for plugging the ends, then if you can manage to fit a standard automotive Schrader valve (tire valve) into one of them, or elsewhere in your piping, you can pressurise the system with a normal bicycle pump. Alternatively, you could just pipe it up with normal fittings, etc. and use a small compressor.

5psi or so should be fine; much more than that and you run the risk of creating an air cannon if one of the pipe plugs decides to pop out... :scared1: I definitely wouldn't "point" this assembly at anything that's breathing or breakable while it's under pressure.

 

[-Nemesis-]

Thansk for that tip mate, was actually reading up on that tonight after posting, certainly sounds like the most decisive method. I'll have to go get some gear first...

Any chance the 3.5" pipe from the AFM to TB would drop pressure? I thought it would be optimum seeing as the AFM is 3.5" outlet.

 

[Turbo4L]

Has spf_lexus got an intercooler? if not thats the reason.

 

[-Nemesis-]

Yep, front mount, possibly bigger

 

[spf_lexus]

Now my noodle is really baked lol. I didn't know you had the 3.40 pulley, and about the larger intake after MAF. Any chance you could try swapping the larger piping to the 3''? You have an IC like me... and that takes air to fill... and sucks up some boost. Now once filled it still needs to fill the larger intake tract as the flow is rushing in but slows down last second to fill the larger intake tract. If anything it might just give better boost response. The 3'' ID supports well over 20PSI of flow before it's a restriction and that would make one mean 4-runner! The dimensions of the IC are 12x24x3''.

 

[spf_lexus]

Ok you got me into my charger again!! dammit Nem!! lol I'm off to get a case-o-beer and Elvis, my English bulldog dog mechanic (he sleeps inside while I wrench).

 

[Turbo4L]

What is the diff between the twon intake before supercharger.
Could you both put up pics of your engine bays for me.
Thanks

 

[-Nemesis-]

At the moment I only had a small pieced of 90mm pipe and a filter on the end.

This arvo I changed the 3.5" section out for a 3" section of pipe, no test runs yet. Taking it to the beach tomorrow, will let you's know what happens.

 

[spf_lexus]

So I test drove my procharger today. Took her up to Denver, a 2.5 hour drive each way. I averaged 22MPG at 70-75mph. Thats with me passing a few semis and white knucklers. Picked up my new Corbeau seats and ratcheting harnesses. It was pretty stable with the occasional hiccup, easy to deal with tho. I must say the car feels like I shed 1,000lb off. Muuuuuch smoother after the valve job. My idle is exactly the same as N/A. One thing I noticed was that I was loosing some vacuum/comp thru my valves because at idle my boost/vacuum gage would "vibrate" back and forth making a clear reading hard but now it's so still it looks like the engine isn't even on.

I feel I MUST share my sighting today. 10 minutes on my way out of Denver I see an all too familiar silver shape massaging it's way thru cars as it merges into the fast lane "In freaking front of me". Know what it was?
-Brand spanking new 2008 skyline GTR. I wonder just how many were in Colorado? odds have to be up there...

I have had the biggest cool-aid smile all day :biggrin:

 

[stevechumo]

If you want the boost to come in earlier (with faster air velocity) , run a small pipe such as 2" from the supercharger to the IC, then run 3" pipe to the TB. I'm very positive you'll see full boost at lower RPM.

 

[-Nemesis-]

The 3" section made no difference today, lucky to hit 7psi...

I tried testing the manifold boost retention yesterday by making up a blank with a valve stem in it, as discussed up above.

At first I attached it to the throttle body inlet, but with the throttle body closed. Attaching my compressor the air just kept going in and in, but I couldn't hear it coming out over the sound of it going in lol, it wouldn't build pressure though. I assume it was heading down the Idle Control Valve pipe? I would have thought that first little section would build and hold pressure straight away.... Just the throttle body itself, which now has the ICV plumbed to it, the bottom breather is blanked off. But no, would not build any pressure...

 

[-Nemesis-]

Just did some reading, I have a feeling my Idle Control Valve might not be shutting properly. Especially seeing as some times when I pull up and idle, the engine sits at 1300rpm or so, sometimes it comes back down after 10 seconds or so, sometimes today (only SINCE the charger) it wouldn't come down at all, just sat well over 1000rpm and everyone looking at me like i'm a wierdo!

So if the ICV isn't closing properly, it could be sapping boost through there yeah?

 

[XR8tt]

I could be wrong here ??
But I think the size has NOTHING to do with boost to a point.. Maybe top end rpm power ??
I would look real hard at belt slipping or leaks ??
If you could measure boost pressure at blower and stages through induction ?? Before the restriction I assume you would read higher boost..Then less after ??

 

[spf_lexus]

One thing Lex pointed out for me was my ICV. he states NOT to route the large 1/2'' vacuum line from the intake tract, said the boost at idle would throw my idle all over the place... and it did! This was my fix, I just took the PCV boss thats under the TB and used that as my ICV intake, and routed the PCV with a breather. Now at idle your ICV won't be sensing boost because it will be behind a 9/10th shut TB. Also you shouldn't
have any PCV valves getting boost, easy way to cause gasket issues. I used replaces my dirty valves and ran breathers. Wish I would have went one step farther and added a catch can (smells like oil/gas sometimes).

 

[stevechumo]

Connect the IAC line to the 3/8 line right behind the TB plate and you won't have any problem with the IAC.

 

[-Nemesis-]

Umm aren't both of those feeds stil in front of the throttle body plate though? The plate is just before the manifold, right at the back of the throttle body.

My ICV is fed from the throttle body, plumbed from where the traction control TPS used to be, so actually closer to the engine than that 3/8 bung.

Still, i'm not thinking the feed to the ICV is faulty, because my idle is very stable, just sometimes after boosting it stays high, which makes me think it's not closing properly and makes me hope thats where my boost is going...

 

[spf_lexus]

the line runs underneath the TB to port just on the inside TP.

 

[-Nemesis-]

My TB looks different to Steve's anyway as it had traction control, which has 2 throttle plates. The main throttle plate looks to be in the same spot though.

I can't see how the port can be behind (non boost side when closed) the throttle plate though. The throttle body is attached to the intake manifold directly and the throttle plate is right at the entry into the manifold. There simply isn't enough room on the throttle body for a boss to be behind the plate, and if it was it would get vacuum at idle anyways, not air that has passed through the AFM....

The throttle body 100% definitely goes: Intake pipe > silicone coupler to TB inlet > PCV Valve/boss > TB plate > Intake manifold

We must be talking about different things. There's simply no in/outlet on the engine side of the throttle plate, on the throttle body.

Still, if there's a problem, like I said, I think it's the ICV itself not where it gets air. My bypass dumps tonnes of air at idle anyway (enough to hear over engine) so it shouldn't be seeing boost at idle.

 

[-Nemesis-]

Well I cleaned it out yesterday. Idle is smack on 700rpm all the time, no change in boost pressure though.

I also tried blocking the pcv line from the manifold to see if the valve was letting boost past. Still the same.

I'm beginning to think that it's just my piping design is less efficient than yours spf, that and maybe .2" pulley size doesn't make much of a difference anyways. Maybe for my theory on early boost I need like a 3.0" pulley...