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Old 11-15-2006, 12:06 AM   #1
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Default Where is the Boost???

First, updated pics and stuff for the vbGarage and sig!

Second, this one has me stumped.
No matter what I do, the highest boost I'm seeing is 5psi. I have double and triple and again checked all couplers and vacuum lines and they are cranked tight... I also didn't leave a parts receipt in the IC inlet. I think my Gauge might be reading about 1psi low... but the numbers here reflect the gauge and not any error correction.

Here are my test runs and the wastegate configuration, runs made in 1-4 gears and are very consistent:
Boost source routed direct from Manifold to WG: 1.5psi
Boost tapped direct from Turbo (build in tap) to WG: 1psi
Source tapped off turbo using MBC: full closed 3psi, full open 1psi
WG actuator w/no line attached at all: 5max settle at 4.

I was under the impression that if I removed the line from the WG, that it would spool indefinitely... but it had a clear peak and then steady over several runs. I repeated these tests several times with same results.

I can draw two conlusions:
#1, my wastegate is shot.
#2, this one might suck:
If you've been following my build, you know the the whole turbo except for the turbine housing is 2G DSM. The turbine housing is off of a SR20det replacement turbo, but not a direct OEM replacement. Both turbos are .48/.49 and made by Garrett. I would assume that the turbine wheels are identical... but don't have the original SR20det wheel to compare. If the SR20det wheel was somehow smaller than the DSM wheel, then the exhaust gas would expel through the wheel without spooling it, limiting boost.

What do I do? I can live for now with 4-5psi as I'm still just breaking it in, but in a week or so, I'm gonna want more.
Thanks in advance!


Last edited by Braineack; 11-15-2006 at 01:01 AM. Reason: show that junx off!
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Old 11-15-2006, 12:46 AM   #2
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Are you 100% sure you don't have an exhaust leak pre-turbo? It doesn't take much and can be pretty subtle, I had to find my leak with a piece of vacuum hose in my ear like a stethascope.

Shim your wastegate actuator, maybe the spring in the waste gate isn't strong enough?

Should be pretty easy to narrow down.

Jay
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Old 11-15-2006, 01:04 AM   #3
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make sure the arm is as tight as possible.

have and air compressor? verify giving it a small amount of air will push the arm out.

hear a ticking sounds at idle as reving near the turbo?

should make max boost with no signal to the wastegate, could be a leak pre-trubo or the wastegate is still open even when the wastegate is fully closed.
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Old 11-15-2006, 09:10 AM   #4
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yes you could also take of the charge pipe and crank it to see if you are getting a good amount of air blowing through there.
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Old 11-15-2006, 11:44 AM   #5
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how plausible is a clogged cat?
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Old 11-15-2006, 12:04 PM   #6
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If you have a compressor, do this:

Get a PVC elbow and cap from Home Depot. Get either a compressor fitting or a tire valve, drill a hole in the cap and install it. It should look sorta like this:



Replace your MAF with this and tighten the clamps. Set your compressor pressure regulator to 0 psi. Attach compressor to the fitting. Increase compressor pressure to 15 psi or so. If you have a boost leak, bad IC pipe, clamp, or core, it will make a hissing sound. Makes things much easier to find than simply tightening everything and hoping.

Damn that's a pretty big pic. Fixed with smaller thumbnail.

Frank


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Old 11-15-2006, 12:17 PM   #7
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that looks like an adjustable wastegate take off the mbc and play with that.
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Old 11-15-2006, 12:52 PM   #8
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Quote:
Originally Posted by turbopezz View Post
that looks like an adjustable wastegate take off the mbc and play with that.

adjusting the rod can only do so much, plus he's done that if you read test #1-4.
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Old 11-15-2006, 01:14 PM   #9
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Quote:
Originally Posted by samnavy View Post
I also didn't leave a parts receipt in the IC inlet.
OK, so that's out.

Quote:
Originally Posted by samnavy View Post
#1, my wastegate is shot.
That's my initial reaction. Are you using the SR20det wastegate actuator?

Is the resistance there when you manually open the wastegate?
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Old 11-15-2006, 04:04 PM   #10
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can you open the WG withh your hand if it is supposed ot hit 8-10 psi then you shouldnt realy be able to.
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Old 11-15-2006, 06:29 PM   #11
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Quote:
Originally Posted by magnamx-5 View Post
can you open the WG withh your hand if it is supposed ot hit 8-10 psi then you shouldnt realy be able to.
Yup. I can just grab it with two fingers and pull it all the way open with little effort. How hard should it be to pull open? I've got two more wastegate actuators at home from the DSM's that I'm not using. I'll grab one of those and compare the effort needed.

The PVC clamp and valve LEAK TEST method is also a great idea. I think I'm going to build one of those as well... makes for a great troubleshooting tool in general.

The wastegate rod is adjustable. I took a couple turns out of it and "pre-loaded" the spring. I'm going to try a few more turns and see if it will hold some more boost.

Leaving one of the local bases today I gave it a little more than intended in 2nd gear and totally lost the rear when the boost hit. I rotated a good 30* before I caught it... pointed the thing straight at the curb and really scared myself. I've gotta learn to drive all over again.

Thanks for the good advice... IT FEELS GREAT TO FINALLY BELONG.
I LOVE YOU GUYS!
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Old 11-15-2006, 06:37 PM   #12
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Quote:
Originally Posted by samnavy View Post
Yup. I can just grab it with two fingers and pull it all the way open with little effort. How hard should it be to pull open? I've got two more wastegate actuators at home from the DSM's that I'm not using. I'll grab one of those and compare the effort needed.
No way it should be that easy to open. What's the stock boost on the actuator? My DSM actuator is "tough" to manually open and its an 8 psi unit. I suspect you'll find significant difference between the two.

Quote:
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a little more than intended in 2nd gear and totally lost the rear when the boost hit. I rotated a good 30* before I caught it... pointed the thing straight at the curb and really scared myself. I've gotta learn to drive all over again.
Sounds a little scary, but in a good way.
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Old 11-15-2006, 07:44 PM   #13
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yeah the wg should offer a decent amount of resistance when you try to pull it open. How fast is that turbo spooling? You should be seeing full boost around 3200rpm in 3rd gear, if you arent its either of these two things....failed wg causing exhaust to bypass turbine wheel causing slow spool...or it could be your exhaust wheel not passing all the exhaust gasses through it since you said the Sr20 wheel was a little smaller.
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Old 11-15-2006, 09:35 PM   #14
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Quote:
Originally Posted by AndyFloyd View Post
yeah the wg should offer a decent amount of resistance when you try to pull it open. How fast is that turbo spooling? You should be seeing full boost around 3200rpm in 3rd gear, if you arent its either of these two things....failed wg causing exhaust to bypass turbine wheel causing slow spool...or it could be your exhaust wheel not passing all the exhaust gasses through it since you said the Sr20 wheel was a little smaller.
All this info makes sense. I am seeing a full 5 or so psi by about 300rpms... but that's with no boost line to the wastegate. I am not sure about the stock sizes or the two Turbine Wheels. I'm not sure if it's smaller or not... it's just a speculation.

I'm going to go preload the WG some more and see what happens. Be back shortly!
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Old 11-15-2006, 10:20 PM   #15
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Two more pieces of good news.
#1: The two DSM WG actuators I have here are SIGNIFICANTLY stronger than the one I'm using... by a factor of two at least.
#2: I took two more complete turns of preload on the rod... and saw an initial peak of between 9-10psi... once 11psi (the clutch wasn't even pretending to hold any of this BTW)... and then drop down to a steady 7-8psi. It varied from pull to pull, but that's the average. So, the turbo will produce the boost, and the turbine wheel is probably the right size.

So, I can conclude that the wastegate I'm using is simply worn out. It appears that it was a lower rating to begin with and now is just shot. I'll be reconfiguring this weekend to mount one of the DSM wastegates and see what I get.

I'm still running pig-rich and pulling 8* out really early to be safe. Hopefully I can get a nice and steady 8-9psi out of the DSM, run it for a week or two taking it easy on the clutch just to be sure everything is settled. I'll plan for the clutch swap and a "re-tightening everything" session the the first weekend in December.
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Old 11-15-2006, 10:23 PM   #16
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My garrett WG on my GT25R is like uber hard to open. I have to really put my arms into it. I'm not sure what its rated, but from UofACATs post it sounds like I have a 12+psi WG. I don't think it should open with minimal force no matter what though.
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Old 11-16-2006, 12:49 AM   #17
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How much fuel pressure are you running?

I just threw my 1.8 injectors back on and at 110psi of fuel they can fuel 9.5psi with no trouble.
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Old 11-16-2006, 09:26 AM   #18
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yes i am right once agian. way to go now get a clutch.
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Old 11-16-2006, 10:15 AM   #19
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Quote:
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yes i am right once agian. way to go now get a clutch.
you are so smart, youre my hero. :gay:
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Old 11-16-2006, 11:22 AM   #20
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Quote:
Originally Posted by braineack View Post
How much fuel pressure are you running?
I just threw my 1.8 injectors back on and at 110psi of fuel they can fuel 9.5psi with no trouble.
Well, I don't know. I've got the Walbro 190 with the base pressure on my AFPR set as recommended by Begi... I think 48-50psi, so I set 49psi. It idles great.

The needle valve on the FPR is set for max rate of rise for now. During my runs last night, it would scream right up to 10-11psi when I would lift. It would definitely have gone higher. I could feather it and keep a steady 7-8psi but at the expense of the clutch.

I have no way of knowing what A/F is had during those runs, but I had no knocking or ill feeling about the way it was running. The motor sounded fine and pulled like crazy against the slipping clutch. I'm not sure what it would be like at a steady 11psi with my foot to the floor (I think it would be somewhat lean with the 1.8inj's).

I took a turn out of the rod this morning before coming to work and was seeing initial climbs to 8-9psi and then steadying around 5-6psi...which was still a little more than the clutch liked. If I get the clutch all the way out before really nailing it, it will hold, but forget about keeping any throttle at all during shifts.

Right now my only boost control is the WG spring itself... the vacuum line to the actuator is disconnected and it seems to be working fine as I've described above (although that is contrary to every wastegate principle out there). I'll get it swapped out this weekend and see where we stand with the MBC inline and tuned. I don't see why I shouldn't be able to run 9-10psi steady... we'll see how it runs in that range or if the clutch will keep up.

PS... new motor mounts feel awesome... between that and the turbo, I've gotta teach myself how to drive all over again.

PSS... still looking for some inj's to match my RX7 MAF (anybody got some used 305's or 330's they wanna part with... or just a comprehensive list of donor cars I can search through ebay???)... I want that 10psi!!!
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