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Previous Next Up Topic Engines / Subbug - Subaru Power / Turbo reference signal? (10988 hits)
By @Jeff GS Date 2008-11-25 22:01
OK, so beginning to work out all the pluming to/from the turbo - coolant lines, oil, etc.  Started thinking about how to tie the wastegate to manifold pressure, and really can't decide where's the best place to reference it?  Also need to plumb in the cockpit boost gauge, which would seem to need the same reference signal, plus the MAP sensor for the computer?

There's a small hose fitting right on the turbo outlet side, a mere inches away from the wastegate reference fitting.  Seems like the cleanest way to do it would be to just connect the turbo to wastegate directly?  Or would it be better to run a hose from the manifold plenum (and downstream from the intercooler) to the wastegate, and MAP/Gauge?  Several fittings there to use for this.  Hmmm, also need to reference the fuel pressure regulator!  Help!  What's the best routing for all this??

By Jay H (X-20) (ManxVair CC) Date 2008-11-26 04:19
The waste gate sensing line needs to go between the compressor and the throttle body. When the throttle shuts and the turbo is still spinning, the sensing line needs to know that the turbo is building pressure and it lets the waste gate open so the turbo won't stall or "water hammer". Some compressor housings will have a fitting right on the housing itself. I believe GReddy turbos do. I'd have to go look at the stock subi because I can't remember, lol.

Ideally, the boost line will be on the manifold AFTER the throttle body. This will give you a true boost reading. If you simply tee into the waste gate sensing line, you may see a spike each time the throttle plate is shut, until the waste gate opens... most likely it will cause the needle to jump.

MAP sensor should also be on the manifold after the throttle plate for the same reason listed above.

I would also tie in the fuel pressure regulator to the manifold itself after the throttle body. There's little sense in tying the FPR sensing line to the intake upstream of the throttle body, as each time you get off the throttle the injectors might spike.

After the throttle boby = most accurate location for all engine related (ie: injectors [FPR], boost gauge, MAP sensor line)
Before the throttle body = most accurate location for turbo related (ie: Waste gate)

A word of caution... If you reference the waste gate downstream of the throttle body, the potential exists to break impeller vanes due to water hammer. That's what the experts say anyhow.

By @Jeff GS Date 2008-11-26 12:18
Thanks Jay!
I left off one other item - the blow-off valve.  I know it needs to be referenced like you've described for the wastegate - to relieve pressure when the throttle is snapped shut.  That makes sense the WG needs to be "vent" exhaust pressure then too, killing boost.
I was able to trace some vacuum lines from the OEM "bundle of tubes" that fed the injectors and vacuum lines around the engine.  There are several tube fittings on top of the plenum section of the manifold for connections downstream of the throttle.
My TD04 WRX turbo (not the IHI turbo that came on the engine originally) does have a fitting right off the turbo discharge tube, which seems ideal for connecting right to the wastegate.  The BOV will be in that same vicinity so I could tee it into the same line.  This would be more or less independent from the rest of the engine vacuum lines.  My only concern there was the WG would see boost right out of the turbo, where I think it would be highest, not downstream past the elbows, intercooler, connections, etc. where it will have likely dropped some.  That could cause premature WG opening?  Guess a boost control valve could be used to compensate.

Also took note of the fitting sizes on turbo and wastegate - 3/16" (and for some reason the BOV is 1/4"!).  That seems about right for the general vacuum line plumbing for WG/BOV/Turbo and also the boost gauge in the cockpit.  I'll have to double check the Megasquirt MAP fitting size, but the FPR is 1/8".

Now to deal with the oddball turbo inlet/outlet sizes......  Inlet is 2.205" and outlet is 1.890".  Finding it difficult to source silicone connector elbows/reducers/etc. for these unusual sizes.  2-1/4" and 2.0" would be so much easier!

By Jay H (X-20) (ManxVair CC) Date 2008-11-26 14:23
"My only concern there was the WG would see boost right out of the turbo, where I think it would be highest, not downstream past the elbows, intercooler, connections, etc. where it will have likely dropped some."

That is possible. Ideally you would want the sensing line after the inter cooler for something that won't suffer from "heat soak", like a 1/4 mile car or something like that. This may be negligible, but my thinking is that referencing the sensing line downstream of the inter cooler would allow the turbo to continue to compress (Utilizing the inter cooler for a slightly longer duration than might be possible if the reference line was upstream of the inter cooler).

I'm sure you know the inter cooler works as a heat sink, and actually cools off long after you have boosted, so if it gets heat soaked, the thermal efficiency is lowered, and detonation may happen the next time you roll on the throttle. My thinking is to minimize the amount of work the inter cooler may be subjected to, hence my suggestion to reference prior to the inter cooler. I don't have any scientific data though to support my thoughts on location. It may make no difference though in real world driving.

"That could cause premature WG opening?" I suppose that's possible, but if the inter cooler is compressing (cooling the air charge and making it more dense) Then the inlet pressure won't reach WG opening pressure until the charge after the cooler is at set pressure. On the other hand, if you did manage to heat soak the inter cooler, then you might consider it prematurely opening... but if the air charge isn't becoming more dense as it goes through the inter cooler, then either side would work for a reference.

Like I say, I think its probably negligible either way you do it because you're talking about a fraction of a second to build up pressure when the turbo is at speed and the throttle goes shut.

Guess a boost control valve could be used to compensate. I'd watch out for these... I've never been a fan myself personally. Many of the cheap ones simply use a needle valve to bleed off pressure from the sensing line to the atmosphere. Why would you intentionally overcome a safety device designed to protect your investment? A holding valve is a little different, in that it holds the pressure completely away from the WG only until the pressure is met, then it sends it full force (not vented off to atmosphere) to the WG, so there is no chance of an issue (As long as it is power shut and spring open in case you have an electrical issue) I'm not sure they even make one that springs shut and powers open, but if they do, don't get one of those. That's all you need is a bad connection to fail to open the valve and your turbo grenades itself.

Hope this helps. :-)

By @Jeff GS Date 2008-11-26 23:15
Thanks for the feedback Jay!

BTW - just how flexible are the silicone hoses anyway?  That is, how much in size will they stretch up?  1/8" diameter? (in the 2" size range)

By Jay H (X-20) (ManxVair CC) Date 2008-11-28 15:30
No prob Jeff,
I think it may depend on the quality of the hose. I doubt it will stretch much. 1/8 inch might be possible to get on, but I'm not sure how much luck you'll have getting it fully seated on the fitting. I think I had one that needed a little stretching to get on. I'll bet it was 1/8" and it took some work to get seated so it could be clamped. I'd have to go back through my documentation to see for sure the size/difference.

By @Jeff GS Date 2008-11-29 14:06
Thanks Jay.  Looking again at my turbo, I think I'm going to make up some "adapter" rings and just shrink-fit and locktite them onto the existing connections, bringing them up to standard english sizes.  Need to get the turbo mounted up first though, get a better idea of exactly how the piping for it will be routed.

By Jay H (X-20) (ManxVair CC) Date 2008-11-30 05:25
When Paul made my intake, one of the adapters could not be sourced, so a strip of metal was welded on radially on the smaller diameter, making essentially both pipe OD the same (or close enough) to use a straight connector. This may be what you're thinking of doing... almost sounds like it.

Here's a shot of the intake and the ring to make up the difference in size.
By @Jeff GS Date 2008-11-30 20:05
Nice looking J-tube Paul made.  Looks like a couple of NPT fittings on there - what are they for?

One of the biggest hurdles I find of trying to combine available and inexpensive engines and components that come with them - in this case the JDM Subaru engine and turbo - with readily available aftermarket parts is the metric to english conversions required.  This seems like one of the biggest challenges to adapting one of these engines to a custom vehicle.  It's nice that outfits like Outfront and others have already designed and manufacture a lot of these items, but when any deviation is made from what they offer, then you're on your own so to speak.

I hadn't given the turbo connections too much thought once I'd gotten the cooling and oil connections worked out for AN fittings - just figured I'd pick up some silicone hoses and hook it up.  After all, there are plenty of hose retailers out there!  Frustrating though when you find out what's commonly available in hoses doesn't fit what you have!

I think "re-sizing" the connections on the turbo is probably the best solution.  I need to connect the inlet to an elbow and then to an air filter.  The outlet will need to connect up to an intercooler, likely a 2.5" fitting there.  That will be the trickiest part to tackle as the turbo has a nice lip to secure the hose fitting which will need to be mostly removed in order to fit a thin-wall tubular ring over it to re-size the connection.  Yes - the idea is the same as Paul used on your J-tube, except I will be installing a press-fit re-sizing ring directly onto the turbo.

By Jay H (X-20) (ManxVair CC) Date 2008-12-01 00:07
Paul did a fantastic job. He's a great tig welder, which is something I have yet to learn let alone master. I stick with Mig for now.

The larger of the two (on the left in this pic) is for the Intake Air Temp sensor for the MegaSquirt. The smaller one on the right is for the water/methanol injection. I went with "Devil's Own" injection kit as suggested by Albert. It's a super high quality item.

I hear what you're saying about the fittings. Paul sent me a diagram sketch with sizes and such and asked me to assist in sourcing the proper silicone hoses. Some were to be reducer hoses. I had no idea how difficult it would be to find anything outside of the norm sizes until I did a little research myself. I think Paul had learned from the engine he did before me. He mentioned that sourcing the proper hoses was probably the biggest challenge of the build. You need to keep a straight head, especially if you have some variables IE; you haven't ordered or built the intake yet, so that size may be subject to change based on available hose sizes. It all gets confusing.

This is the best picture I have of my intake plumbing. It may give you an idea on filter plumbing. We needed to angle the tubing between the filter and compressor to help the filter clear the body.

Here's a shot of it installed from the back

Hope these add something to your project.
By @Jeff GS Date 2008-12-01 23:18
Now I've got it Jay!  BTW - LOVE those MASSIVE rear tires!  Melt 'em down any yet??  And what's that I see between the wastegate and turbo vacuum line feeds???  Looks like a little boost control going on??  :-)
Man, that sure is a lot of wiring and plumbing!

OK - back to the thread drift....
I found a source for 1.875"/48mm silicone hose couplers.  That'll take care of the outlet side of the turbo.  I know I will have to fab up a hard-tube connection from turbo to intercooler and I can adapt the turbo end to connect to the 1-7/8" size.  Will likely use 2.5" tubing for this, and connect directly to IC with a like size connection.
For the inlet side, I can't find anything that's matches the 2.205"/56mmm size.  However, the straight machined surface can easily accept a mild press-fit adapter and take it up to 2.5".  With that there are plenty of options for intake tube and connections.

Also came across a nice BOV from Samco from the same company.  The OEM plastic valve seems a tad skimpy, the Samco valves aren't too pricey and up-size the hose connections from 3/4 to 1".  I can tap this in between the IC and throttle body, and back to the inlet tube at the air filter.

I think I've got a plan!

FWIW, the outfit that has the hard to find 1-7/8" connector hose is:

By @Jeff GS Date 2008-12-02 00:45
Oh yea,
One other question:  What size line did you use for the MAP signal to your MS?  Is it the same line that sends the signal to the boost gauge?

By Terry F Date 2008-12-02 04:11
I've ordered from several times, zero problems...
By Jay H (X-20) (ManxVair CC) Date 2008-12-02 06:12 Edited 2008-12-02 06:24
Melt 'em down any yet?? Mostly just the trannys! LOL. I'm on number 3 now since the Subi engine. I really need to have one built up or build one up myself!

And what's that I see between the wastegate and turbo vacuum line feeds???
What? you mean at the end of the little red hose? You spotted my little boost controller. MS controlled of course. :-) Good eyes.

Here's where the boost gauge hooks up to on the manifold. It's an 1/8" compression ferrule on the intake manifold. It's hard to see because it's tucked behind some hoses, but I doctored the photo a little for easier viewing.

I don't recall the hose size needed for the MAP sensor. As a matter of fact, I have two MAP sensors, one for the MS and the other for the Devil's Own W/A Injection, so I would have to go back "under the hood" to refresh my memory on what size it is.

When can we see some pictures of your project engine?

By @Jeff GS Date 2008-12-02 17:33
Afraid no new pics lately - but here's one from a couple months(?) ago:

Building the exhaust header has occupied 95% of my buggy-play time lately.  It wasn't easy snaking around all that suspension, trans and linkage, etc to get it to come together at the rear!  I'm almost up to the turbo mounting flange currently - have one more straight section to fit and tack.  Would have gotten to that point last weekend except the weather didn't cooperate!  :-(
I'm determined not to take any new pics until I reach that goal!  Never built a custom exhaust before, so it's been a huge learning curve.
Also taken a little longer as my welding skills are not what I want for this - so I tacked both sides up with my MIG, up to the merge point and took them down to my welder friend for final TIG work.  Wanted to make sure nothing moved too much before I jointed both sides together.  I then decided to add in a flex joint near the merge elbow, more fitting time, yadda, yadda.  Getting close though!  Next tacking opportunity will require final joining of both sides and will have to be done mounted on the engine/in the car.  Hopefully I can get that done before the hard Winter weather sets in.....

Lots of new parts on order though!  Plumbing fittings, new accelerator cable, rear sway bar bits...   seems like I'm always doing several "projects" in parallel working on it!  Hopefully lots to show on the next round of pics.

Previous Next Up Topic Engines / Subbug - Subaru Power / Turbo reference signal? (10988 hits)

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