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Old 08-21-2000, 06:12 PM   #1
Shik
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Wink Boost Cut uncovered

A hair above 13psi. That seems to be the magic number when the ECU crashes the party

After talking with Stuart Logan from AZ (AZ-GT?), he let me know that he was running 13psi with no intercooler and has yet to have a problem with the car going lean( judging from his Air/Fuel ratios). He also mentioned that ~ocasionally~ he would hit boost cut so going by that info, I would think it is fairly safe to say that the stock fuel sytem is capable of keeping up with boost levels within the boost cut( again, around 13psi). I plan on taking my car up to the Subaru dealer(ex-employer) and seeing what the Select Monitor says the O2 voltage is, just for my own curiosity. But, the way I figure it, if Subaru put the boost-cut up that high, they obviously feel that there is no real danger up TO the boost cut, right?

Boost cut, as many of you know, simply feels like you hit a brick wall for a second. The power doesn't fade off or anything, it's just that you are going, then all of a sudden not going, then going again.

Right now I have the boost set at about 12.5psi just in case I get some boost creep or a cold crisp day comes along. I get about 11-11.5psi in 1st gear which is much more fun then 8-9psi Then in the rest of the gears it's about 12.5 and seems to hold just fine so for now the stock BOV seems to be working. The stock clutch also seemed to work just fine but we'll see.

The car is still no rocket by any stretch of the imagination, but it is without a doubt a very fun street car
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Old 08-21-2000, 07:14 PM   #2
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13psi huh? I did a little hose 're-routing' as you suggested in another thread, the only thing different I did was instead of running a long length of hose to a tee next to the intake manifold I just went directly up to the map sensor with a two inch piece of hose to a tee. Boy was I surprised to see the needle on my boost gauge swing up to 12psi!!! With no other mods, just switching the hoses around I got 12psi! and I haven't even hooked up the 'budget' bleed valve yet! She does pull nice though.......seems to spool up MUCH quicker too
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Old 08-21-2000, 07:55 PM   #3
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That's right I'm running 13 lbs of boost and according to my air-fuel meter the ECU keeps my mix plenty rich. I haven't experienced any detonation and have been running this combo for about 4 months. I'm not going any higher without an intercooler.
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Old 08-22-2000, 02:35 AM   #4
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Fantastic Pete! At least the cars get to stretch their legs a bit with some added boost

Stuart, thanks for the info. BTW, your poster should be in the mail today or tomorrow. No one has a poster tube long enough so I have to buy two and piece them together . I'll let you know when it goes out.
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Old 08-22-2000, 07:23 AM   #5
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Pete, where exactly is the MAF?

I'm new to Turbos, so bear with me. I know where the Boost Solenoid, Wastegate and a few other parts are, and i'm quite sure i know what the MAF is but i don't know if we're talking about the same thing...

Here's a picture of the intake side of my engine. It's a bit dark but could you possibly point out where you hooked who to what?
http://www.xmission.com/~dac/images/93/engine.jpg

Well i guess since we've got at least 3 guys running 12+ PSI with 90+ octane fuel, intercooler or not, Subaru was being VERY conservative with the boost on this car.

I can understand their thinking though, i'm sure most used turbos have had some twit put 85 octane gas in before. Idiot-proofing is nice, but when it marginalizes performance i have to shake my head. I'm sure the car would have sold a lot more if it'd had 180hp and 200 lb/ft of torque...

I wonder if my Auto is up to it...

[This message has been edited by DLC (edited August 22, 2000).]
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Old 08-22-2000, 04:53 PM   #6
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Until I had my Legacy Turbo converted (AT - MT) I was running 1 BAR (14.5 psi) comfortably. Our IHI's are not efficient after 0.9 BAR (13 psi) according to many Subarist in Japan b/c of heat. An I/C is needed.

A simple boost controller or boost cut controller can be installed to override the present boost cut.

I highly recommend getting a ball bearing IHI turbo currently used on the WRX. I am planning on going this route soon. This setup will allow us to get 1.35 BAR (18.8 psi) or more and will spool much faster. I was told that the TC will be a simple swap since all the bolts and piping are identical.

(sorry I miss typed 1.35 to 13.5)

[This message has been edited by Subarist (edited August 23, 2000).]
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Old 08-22-2000, 06:50 PM   #7
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DLC, I edited your picture in Photoshop and Emailed it to you, should clear things up

Subarist, please share with us your 'simple boost cut controller'. 13.5 bar would equal 202.5 psi (1-bar = 15-psi correct?) Unfortunatly the newer model ('97 and newer?) turbo's and intercoolers are differant and will not be a direct 'bolt-on'. I have a '97 and a '99 WRX TDO4 turbo and a '97 dual inlet WRX intercooler which I am in the process of fitting to my '92 Turbo Legacy, the issues I am running into are:

Turbocharger:
compressor outlet is clocked in a differant position than stock - remedy - reclock

inlet is straight on TDO4 whereas stock has an extremely sharp 90 degree bend - remedy - find/fit a tight 90 elbow :/

Intercooler:

this boy is a tight fit! Remove dual inlet intake assembly and discard! build covers for exsisting inlets and seal them off as they will no longer be used. Cut hole in end-tank for new inlet, don't forget to add the splitter in the end tank. Relocate outlet 3 inches over to clear clutch master cylinder. Relocate BOV outlet to clear throttle assy. Shorten outlet and/or throttle body so the core will fit between the firewall and throttlebody. Come up with some sort of mounting for the intecooler.

Other then these minor issues it is a 'straight bolt-in'
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Old 08-22-2000, 07:11 PM   #8
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I just did the mod Shik described earlier, not the one to get me 12PSI.

The reason being is that i can't gauge what it actually is till i get a gauge!

I'm going to order one up, get it installed then try the 12PSI mod and see what it does for me.

In taking apart the whole intermediate intake from the MAF to the turbo i found a small hose was disconnected and taped off. I also found a connector of the plastic box that had apparently been hot-glued at one time and had a piece of electrical tape near it, but not covering it. The hose is the one that goes in the bottom of the boost solenoid. Not having the proper tools to reattach it i've simply let it go to atmosphere and plugged the hole in the box.

Any idea what this actually does and if i should try to reattach it to the box?
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Old 08-22-2000, 07:12 PM   #9
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Subarist, just so some people do not get the wrong idea, simply swaping to a WRX turbo will not allow you to run 18+ psi( unless it is on a Toyota Supra, that is). With 380cc injectors( supposedly), I somehow doubt that they would be of much use at that high of boost levels anyway, let alone the pump(although I don't know the exact flow characteristics, I'll be switching to a Supra pump just to be safe).

Also, what are you planning on doing with the newly discovered , to put it nicely, "air flow challenged" heads on the Legacy turbos? I mean, going by the flow bench data from Cobb Tuning, these things really are disasterous when it comes to making power, and worse yet, it was found that there really is no room for any kind of substantial improvement, so porting is not the best option. Even at 13psi, top end improvement was little at best on my car. Not that the boxer motors are high reving motors to begin with but you are not going to be at 3000rpm at 18psi either.

Adding a boost controller to the map sensor line is the best bet because it does not eliminate the cut-off completely, but rather lets you raise it to where ever you want it.

Pete, how bout taking off of work for a few days and getting that baby done so we can drool

[This message has been edited by Shik (edited August 22, 2000).]
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Old 08-22-2000, 07:53 PM   #10
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Any ideas on my last post?!?

Oh, and what model vdo gauge should i look for at Summit, they don't have a browseable database...
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Old 08-22-2000, 09:23 PM   #11
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Dave, I'm guessing here but I would think the bottom hose on the BCS in the "bleeder" hose. The BCS basically bleeds off boost to maintain it's target boost psi.I'm assuming the bottom hose routes the boost that was "bled" off , back into the intake. To be on the safe side it should be connected to where it originally was. It probably doesn't make much of a difference but just to be on the safe side. All of this is assuming I am correct of course

As for Summit, to be honest I'm not sure if that is where I saw them so cheap but I think it was in a flyer they sent me. I get mine from Extreme Motorsports because 1. I know they have the one I want, and 2. They sell a nice installation kit for a few extra bucks and it makes installing it a breeze. You might want to try there.

[This message has been edited by Shik (edited August 22, 2000).]
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Old 08-23-2000, 10:07 AM   #12
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I am sorry about the typing error on the 13.5 Bar. It should be 1.35. There are HKS & Greddy Boost Cut Control units, if all you want to do is intercept and alter the signal. As for a boost controller, there are the manual and electronic kinds which I recommend.

I do agree with our headers and down-pipe being the week point in our car. The European Turbo has/had a header that looked much better (design wise) but I forgot to take pictures and I have no-idea who has them now.

As for fuel, you will need to get a bigger fuel pump. The JC/Holley (sp?) pump will be my recommendation. It is a simple installation, practically a swap. A fuel controller is needed too, but that is a necessity along with a boost gauge and exhaust temp gauge if you are increasing boost so....

As for increasing the boost to over 1.35 Bar, I remember JC Sports had their first car running smoothly at over 1.35 bar. I don't think he had different headers back then and it pulled all the way. I know that there are several companies trying to get a header for us. JC tested the Borla header on a NA and a TC car and found out that it was useless for the TC car where as you did see some gain in a NA car; other than the obvious mistakes Borla had.

"'97 and a '99 WRX TDO4 turbo" - I thought most, if not all the WRX from Japan used the IHI ball bearing turbo. Let me check with my source. I am sure that the IHI ball bearing is a simple swap. As for the IC, everyone here as their own nightmare. I think it is much easier and cheaper (?) to get one made than to fit a WRX IC.

DLC, I second Shik on the boost solenoid valve. I have mine disconnected but that is b/c I use an aftermarket boost controller. (I think we are talking about the same thing) I'll double check on this though. Nice to hear that we have a wagon turbo willing to do mods. I wish I had a wagon.
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Old 08-23-2000, 10:20 AM   #13
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Well, i'll see if i can find a place to connect that to, if the original spot is unusable as it looks.

Most people gasp when i tell them i bought a Wagon. I'm a single guy and so most of them look at me funny or laugh. So what, i've always liked a smooth wagon
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Old 08-23-2000, 10:22 AM   #14
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My first Subaru was a wagon, but I rolled it. If I had $1000 more, I would have bought the turbo wagon instead. The wagon can be very intimidating when lowered.

Have fun!
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Old 08-23-2000, 01:42 PM   #15
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Subarist, I believe the only ball bearing IHI turbos that Subaru uses are the STi models, the standard WRX gets a standard IHI or Mitusbishi but if memory serves me correct, IHI's are exclusively used now... but I could be wrong

If you have any questions on WRX turbos( years, models, applications, etc.) drop Jay-UK a line. The guy is absolutely brimming with turbo knowledge and he has personally probably used the good majority of them. Friendly fella as well.

As far as the intercooler goes, easier to get one made to custom fit? Without a doubt. But price wise I've heard of people getting the WRX intercoolers for under $200 US. I do agree though, if you have the extra money to spend, get one made.

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Old 08-23-2000, 02:50 PM   #16
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You are right. The BB TC was for STi models. How much is the tubing to rework the WRC IC to our car? Is the Legacy IC compatible with ours? Just wondering....

DLC, I like your page. Keep up the good work.
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Old 08-23-2000, 05:01 PM   #17
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Hmm, I got my intercooler for $135

Shik, only problem with taking off of work is that I will then do my scab work - this is how I pay for my toys I am still in the 'gathering' mode, need exhaust gaskets and compression fittings to fit the EGT sensor, aluminum and silicone tubing for the intercooler, a couple of AD595AQ chips for the thermocouple display, etc..........

Dave, go to: www.autometer.com They have a complete product listing online, Summit sells all of there products I got the 2-5/8" Phantom boost gauge. There is even a green condom in the box to put over the light bulb to make the gauge glow green to match (kinda) the dash. Where are you going to put the gauge? I made my own pillar mount for the boost gauge but now I need to put the EGT somewhere, and the fuel pressure too! Ohh, just remembered, go to: www.carparts.com/gift and enter this coupon code: 2209009. This will get you $50 off on your first order of $100 or more, no BS and fast service, got my EGT gauge from them.

Subarist, sorry, had to raz ya on the 13.5 bar typo, my bad! I don't think the header is a weak link until you get over 375hp or so (guess), the cylinder heads on the other hand don't flow to well. Several people have swapped the DOHC heads onto our motors with success although knowone is giving details. I would guess one would need to swap all of the pulleys and not much more.
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Old 08-23-2000, 09:17 PM   #18
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Thanks Subarist!

I ordered the vdo from Extreme Motorsports. It was probably more than i should have paid but oh well...

I'm not sure where i'm going to put it and i've not given it a ton of thought to be honest. Since i'm not going to be tweaking mine too hard till i get an intercooler, and even then it's going to be mild on account of the fact that i'm stuck with an Auto, i might just have to make it moveable a bit but so i can stash it, say in the glovebox as well. I guess that's if it has a flexible hose...
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Old 08-23-2000, 09:27 PM   #19
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DLC, try to get an aftermarket transmission cooler. This will help your AT a little.
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Old 08-24-2000, 06:15 AM   #20
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The Turbo AT came with a larger AT cooler, to the best of my knowledge, but since all of the reviews of the turbos that i've found are the 5-speed, i'm going to have to make sure.
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Old 08-24-2000, 09:51 AM   #21
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The cooling system that came with the car is no use if you want to slightly up the boost. i went through 2 trannies before I finally did the conversion. However my friends here that have AT with the JC Sports Turbo kit have little problems if not any after installing a tranny cooler.
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Old 08-24-2000, 10:10 AM   #22
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Well then, i guess i need to get a bigger cooler...or swap it out for a 5-speed.

I take it you had more than one auto in your car and you've switched over?

What trans did you go with and what kind of cost would i be into if i were to choose that route instead?

Since i'm going to have to drop $800 to fix the Torque Bind problem i'd rather have a good shop swap in a 5-speed and put that money into it and have the only 5-speed turbo wagon in the US

And i'm dying to know if the JCSports Turbo Intake is worth it. What extra noise can i expect and what kind of performance and mileage gains did you personally witness?

[This message has been edited by DLC (edited August 24, 2000).]
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Old 08-24-2000, 10:56 AM   #23
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Yes, I was tired of swapping/fixing the tranny every 24 months, so I finally had the swap done. A regular aftermarket tranny cooler would be fine, I think. It is easy to hook-up, and it adds an aggresive look to the car.

FYI, your car won't be the only MT Turbo Wagon in the US. There are several in Colorado.

I have a regular Impreza/Legacy Tranny with hydralic clutch system. The turbo tranny is too hard to comeby and expensive too. I was told and agree that the stock tranny can with stand a lot more than what people say.

As for installation cost, it'll be about 6~8 hours in labor, parts will depend on the trade-in value of your tranmission. The turbo AT is a very thought after item, so if it is in good condition, you may be able to make some cash. The wiring takes the longest. I had mine done by JC Sports, but there are others out there that can do the swap. You'll need a MT crossmember, MT tranny and rear diffs that match. People have said that you might have to swap out the ECU, but it can be done without that. Talk to several independent Subaru shops. I'm sure they would like to get the AT tranny.

As for the JC intake, I like it. It is noisy at first, but you'll get used to it. We did do some GTech runs and with an exhaust system, I saw a gain of about 15%. With plugs and wires, the number was closer to 18%.
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Old 08-24-2000, 11:06 AM   #24
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So a normal Legacy/Impreza 5-speed will work? I know the original ones weren't hydraulic so i assume that you've got one of the later hydraulic ones, if i assumed correctly.

The trans is ok except for that bunged part, a common thing in AWD ATs. It shifts very well and even bucks a bit into third, a good sign indeed.

Since i'm only over here in UT, 550 miles from JC, I could realistically drive over and have JC do it, depending on the time involved. I'll give them a call and see.

I guess i was being a bit pretentious about having the only turbo wagon 5-speed eh?

Did you see any mileage gains with the intake? And does loud just mean the usual growl at WOT?
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Old 08-24-2000, 11:17 AM   #25
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Mileage gain, probably none; loss, probably none. But it could be b/c of the way I drive the car.

It is load, expecially under full throttle and when you let go you can hear the wastegate dump the air out. Sounds cool. It actually sounds like any TC car with an aftermarket intake.
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