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bureau13
Joined: 07 Sep 2017
Posts: 480
Location: South Florida
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 Posted: Sat May 23, 2020 12:02 pm Post subject: Preferred location for mounting underhood MBC |
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I have acquired a Turbonetics MBC, which at least for now, I've decided to mount under the hood. I will tee off of the wastegate controller line, through the MBC and down to the top vent on the wastegate. Since the vacuum lines to/from the wastegate are 1/4" ID I replaced the Turbonetics hose barb fittings with larger ones to fit this hose. The only remaining question: Where to mount the thing? Anyone have any favorite spots for something like this?
My current thoughts are up by the firewall on the passenger side. I've got some room there although not sure I left myself enough hose length to get there and back.
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1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)
Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen) |
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Carrera RSR
Joined: 08 Jan 2010
Posts: 2309
Location: Somerset, UK
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| Posted: Sat May 23, 2020 5:25 pm Post subject: |
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Dash mount it. You will need to fiddle with it to get the boost level right.
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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bureau13
Joined: 07 Sep 2017
Posts: 480
Location: South Florida
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| Posted: Sun May 24, 2020 3:55 am Post subject: |
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It seemed easier to do it under the hood, and I don't plan on fiddling with it a lot once it's set, but you're definitely right in that it would be a pain to get that initial correct set point with it out of reach under the hood.
| Carrera RSR wrote: | | Dash mount it. You will need to fiddle with it to get the boost level right. |
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)
Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen) |
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chuck21401
Joined: 20 Feb 2005
Posts: 530
Location: Annapolis, MD
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| Posted: Wed May 27, 2020 6:05 am Post subject: |
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This is my temporary set up and recognize that it isn't ideal.
It does take some fiddling to get the boost level right. I found that even a 1/4 turn can make a huge difference.
I've found that the boost level is mostly consistent...but after a long run the boost level creeps up. I'm wondering if it has to do with heat....and if that is the case...would need to find a cooler spot under hood.
Here's another option if you'd like to mount a boost controller in the cabin.
https://retro-sport.com/porsche-boost-knob-adjustable-control-917-924-930-934-935-962
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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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bureau13
Joined: 07 Sep 2017
Posts: 480
Location: South Florida
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| Posted: Wed May 27, 2020 8:29 am Post subject: |
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Interesting...I wonder why a device like that would be subject to heat soak? Doesn't seem like it would, really. Looks like the exact same one I have. I lucked out in that I found a lightly used one in perfect condition on the 'bay for about $30. That other one looks nice but $1500? Yikes!
So if I'm looking at your picture correctly, you have it installed in single-port mode, right? Why did you go that way instead of using the top port?
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)
Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen) |
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jacobroufa
Joined: 18 Nov 2016
Posts: 531
Location: Belvidere, IL
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| Posted: Wed May 27, 2020 8:43 am Post subject: |
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| bureau13 wrote: | | So if I'm looking at your picture correctly, you have it installed in single-port mode, right? Why did you go that way instead of using the top port? |
Also curious about this. Taking notes for my MBC 
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1980 Porsche 931
1981 Porsche 924 Weissach |
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Carrera RSR
Joined: 08 Jan 2010
Posts: 2309
Location: Somerset, UK
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| Posted: Wed May 27, 2020 5:53 pm Post subject: |
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I wouldn't use a 'modern' small bore boost bleeder on our waste gates. They cannot handle the volume of boost needed by the large waste gates. You will over boost.
I would not restrict boost to bottom port only either. Again risk of overboost.
The air regulator/boost controller needs to be fed to the top port of our WG's to control counter pressures of bottom port.
The stock over boost switch will not cut fuel until circa 1.2/1.3 bar boost. By then the damage may already be done on a non IC'd motor.
_________________
1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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chuck21401
Joined: 20 Feb 2005
Posts: 530
Location: Annapolis, MD
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| Posted: Thu May 28, 2020 3:58 am Post subject: |
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| bureau13 wrote: |
So if I'm looking at your picture correctly, you have it installed in single-port mode, right? Why did you go that way instead of using the top port? |
Yes. Single port mode.
Originally my main goal was to get get back to stock boost. My wastegate wasn't working correctly and I was seeing 15psi. I was able to get back to stock boost...and wanted a bit more power at euro boost level. I didn't want to drop the exhaust again to access the top side of the WG....so this was the quickest solution.
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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler
Last edited by chuck21401 on Thu May 28, 2020 5:26 am; edited 1 time in total |
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jacobroufa
Joined: 18 Nov 2016
Posts: 531
Location: Belvidere, IL
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| Posted: Thu May 28, 2020 4:10 am Post subject: |
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https://www.grainger.com/product/SPEEDAIRE-1-8-General-Purpose-Air-Regulator-4ZM07
Is this the regulator you are using? Looks the same as in Dan's build (shown here: http://www.924board.org/viewtopic.php?p=338230#338230)
Have been looking at which regulator to buy and I saw this one at Grainger that looks to match. I was wondering about some of the offerings at McMaster just for options since I can order fittings from them as well (which Grainger doesn't seem to have?) but they're listed as differentiated where on Grainger's site they are not -- by relieving and non-relieving types. Which kind of regulator valve do we need?
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1981 Porsche 924 Weissach |
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jacobroufa
Joined: 18 Nov 2016
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chuck21401
Joined: 20 Feb 2005
Posts: 530
Location: Annapolis, MD
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| Posted: Thu May 28, 2020 4:43 am Post subject: |
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| Carrera RSR wrote: | | I wouldn't use a 'modern' small bore boost bleeder on our waste gates. They cannot handle the volume of boost needed by the large waste gates. You will over boost. |
The turbonetics MBC has a larger bore, but it has to be paired with larger fittings and tubing for our purposes.
I have the original tubing/fittings and can take some pictures to illustrate the difference.
| Quote: | I would not restrict boost to bottom port only either. Again risk of overboost.
The air regulator/boost controller needs to be fed to the top port of our WG's to control counter pressures of bottom port.
The stock over boost switch will not cut fuel until circa 1.2/1.3 bar boost. By then the damage may already be done on a non IC'd motor. |
I appreciate the concern being raised. Another option might be to install a different spring in the WG.
I plan to install the intercooler soon...I've been watching old school HKS electronic boost controllers online...they are available and I believe would require the two port set up.
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chuck21401
Joined: 20 Feb 2005
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Location: Annapolis, MD
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chuck21401
Joined: 20 Feb 2005
Posts: 530
Location: Annapolis, MD
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| Posted: Thu May 28, 2020 5:14 am Post subject: |
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| jacobroufa wrote: | https://www.grainger.com/product/SPEEDAIRE-1-8-General-Purpose-Air-Regulator-4ZM07
Is this the regulator you are using? Looks the same as in Dan's build (shown here: http://www.924board.org/viewtopic.php?p=338230#338230)
Have been looking at which regulator to buy and I saw this one at Grainger that looks to match. I was wondering about some of the offerings at McMaster just for options since I can order fittings from them as well (which Grainger doesn't seem to have?) but they're listed as differentiated where on Grainger's site they are not -- by relieving and non-relieving types. Which kind of regulator valve do we need? |
It looks very similar but check the specs; port size on that one seems a bit small? I bought a used Turbonetics MBC on ebay for around $30. Here's one...coincidentally from the same seller: https://www.ebay.com/itm/Turbonetics-Manual-Boost-Controller-Kit-0-25-PSI-10402-25-Turbo/153948137302
There are different models; I have the 0-25psi model. See: https://turboneticsinc.com/store/index.php?route=product/category&path=47
I bought the metric to hose barb fittings online. I bought the larger bore hose barb fittings for the MBC at Pep boys along with the 1/4" hose.
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Carrera RSR
Joined: 08 Jan 2010
Posts: 2309
Location: Somerset, UK
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| Posted: Thu May 28, 2020 8:06 am Post subject: |
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| chuck21401 wrote: | | Carrera RSR wrote: | | I wouldn't use a 'modern' small bore boost bleeder on our waste gates. They cannot handle the volume of boost needed by the large waste gates. You will over boost. |
The turbonetics MBC has a larger bore, but it has to be paired with larger fittings and tubing for our purposes.
I have the original tubing/fittings and can take some pictures to illustrate the difference.
| Quote: | I would not restrict boost to bottom port only either. Again risk of overboost.
The air regulator/boost controller needs to be fed to the top port of our WG's to control counter pressures of bottom port.
The stock over boost switch will not cut fuel until circa 1.2/1.3 bar boost. By then the damage may already be done on a non IC'd motor. |
I appreciate the concern being raised. Another option might be to install a different spring in the WG.
I plan to install the intercooler soon...I've been watching old school HKS electronic boost controllers online...they are available and I believe would require the two port set up. |
You can get to the top port from above with a few top of engine ancillaries pulled out the way.
_________________
1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252 |
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bureau13
Joined: 07 Sep 2017
Posts: 480
Location: South Florida
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| Posted: Thu May 28, 2020 8:56 am Post subject: |
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Chuck, you and I were following a very similar path, until you lucked into that Trust controller. You don't see those too often! Got to put that beast inside 
I too bought a used Turbonetics and 1/4" fittings, although if I decide to put it inside I may try it with 1/8" just to route smaller hose.
It's funny about that Grainger...that looks way too close. Turbonetics must have just bought the 1/4" version, added some fittings and a bracket and added $70 to the price, lol. Glad I didn't buy a new one...
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)
Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen) |
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