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Old 05-10-2001, 01:46 PM   #1
Jimmy
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Post Turbo Question for all you turbo people out there

Iam getting a turbo from ASR its the one from the group buy. Iam only going to run 5psi he said with a the intercooler it comes with i should be pushing 240-250 hp.

do you thing the subaru engine will be able to handle it or do other mods need to be done

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Old 05-10-2001, 01:50 PM   #2
blaster88
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I think the ASR kit has everything you NEED to run. I don't know what gauges it includes, but you should have boost and EGT at a minimum.

5 psi should be about 215 hp, not 250-260.
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Old 05-10-2001, 01:56 PM   #3
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It close to a stage 2 turbo and only 215 thats it
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Old 05-10-2001, 04:08 PM   #4
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EGT, and boost are definitely needed. You'll also need a clutch, and exhaust.

I would say at 5psi you would be in the low 14sec range, quarter mile wise. That would be at least 230hp.

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Old 05-10-2001, 06:42 PM   #5
blaster88
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We are all guessing, here, until it hits the dyno, but you can try the RayHall Engineering turbo power calculator. .

Crank in the numbers (bore = 3.92 in, stroke 3.11), and all the rest, a 72 deg day (22 C), and 85% VE at 6000 RPM (probably high), and a 65% efficient compressor with a 70% efficient IC, you only get 208. You can argue the efficiencies one way or the other, still doesn't move the number much. You have to push 8lbs before you see 240.

A real quick back of the envelope would be able to tell you what neighborhood you would be in on boost. This is GROSS oversimplification, so no nitpicking, but the engine is a big airpump, and at atmospheric pressure (14.7 lbs at sea level) it makes 165 hp. If we were to double the air going through it we could double the hp, so 14.7 lbs of boost should put one close to 330. To get 50% more hp, you are looking at 7.35 lbs - that is needed to get 82.5 more horses - or about 240-250. (Remember, this is at the flywheel). And that would be ideal, but of course we don't live in an ideal world, so those efficiencies come into play. And yes, turbos are different and flow air differently at the same pressure.

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Old 05-10-2001, 07:56 PM   #6
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Blaster,

I DID use dyno results in my calculations, I just didn't include them in my post. My car made 215hp and about the same torque at 5psi, to the front wheels. The stock coming in at a mere 120hp. After a little arithmatic I would say that put me right around 260hp.

He won't be using a stand alone computer, nor will he have 550cc injectors. Nonetheless I still believe he will at least be in the 230hp range.

I don't have the dyno graph for the 5psi run, but I do have one for my 7psi run. I can post it up if you would like to see it.


MattC

[This message has been edited by MattC (edited May 10, 2001).]
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Old 05-10-2001, 08:23 PM   #7
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Nevermind the power, when you run those numbers, it makes it look like an intercooler is pretty pointless.

Temp before intercooler is 50C, after is 39C if ambient is 22C.

Right now, running 5psi on an MY00, I'm getting very slight detonation if I don't run about 97 octane (50% Sunoco 94, 50% Sunoco GT). I'm beginning to wonder if an intercooler will be very effective at such low boost...

BTW, 5psi is lots of fun, even if it is only 220HP
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Old 05-11-2001, 08:21 AM   #8
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Is it worth turboing the car.........

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Old 05-11-2001, 08:33 AM   #9
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Definitely.

I am running 5lbs of boost, and whether I got 50 or 80 hp out of it, the car is significantly faster.

Only a month an a half into it, but the stock clutch works (it will slip some if you nail it at 75 or so) but I don't know for how long. You will want something other than the stock exhaust.

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Old 05-11-2001, 09:56 AM   #10
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what eletric toys do you have blaster88 for you kit

iam getting mine from asr

5psi I have a jcsports 2.5 cat back
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Old 05-11-2001, 10:13 AM   #11
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Jon,
what sized turbo are you running that you are having detonation at such a low boost? What are you running for fuel management?
Joshua
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Old 05-11-2001, 10:31 AM   #12
blaster88
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Jimmy -

The only thing I have is a zener diode to keep the ECU from freaking out about the MAP voltage, and you won't need that on a 99.
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Old 05-11-2001, 10:56 AM   #13
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cool I can't wait to get the turbo
blaster88
what are the 0-60 times

also is the drivetran hold fairly good
thanks for the info
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Old 05-11-2001, 09:34 PM   #14
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Joshua, it is a T3-S70 turbo. It is not pinging because of mixture--it has plenty of fuel. EGTs are happy everywhere. The RRFPR and high flow pump work like a charm.

We're getting a tiny bit of knock right around 4000RPM at full throttle when it's hot outside. Based on what others have said here, and what Trey Cobb told me about MY00's having pretty aggressive timing, we figure that's the problem. The fact that I have Cobb's street cams adds another variable, but I don't know what effect they have.

Next step is an intercooler, although the numbers don't sound too impressive from that calculator. If J&S ever gets their new knock sensor + timing retard into production, that may be just the ticket.
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Old 05-11-2001, 10:05 PM   #15
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Jon,

When I was running 5psi I would get pinging at around 4k when going wide open if it was hotter than 80 or so outside. This was on my MY00 RS with Vortech SFMU, Vishnu fuel pump.

I added a Rallispec intercooler and since then I haven't had a single ping and we are already seeing 105 days here in AZ. I have romped on my car after it has been sitting outside all afternoon and it is doing fine. EGT's are right where they should be.

I was amazed at how much of a difference the intercooler made.

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Old 05-12-2001, 12:06 AM   #16
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I don't have any 0-60 times - it is assuredly faster, though.

Liek I said, only 6 weeks into it, so hard to say on the driveline. However, I don't think anyone who has stayed with low boost has had any issues. It's when the boost monkey gets on your back that the problems come. Larry (ImprezaRSdotcom) experienced an explosive decompression of his transmission when he dialed it up to 9 lbs, I think. And there weren't any warning signs.

I expect I'll have to replace my clutch sooner than normal. How much sooner is anyone's guess.
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Old 05-12-2001, 12:13 AM   #17
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Why pinging occurs:

1) Ignition timing too advanced
2) Too low octane gas
3) Lean A/F ratio
4) Exhaust gas backpressure (restrictive exhaust)
5) Intercooler - inefficient, too small, etc
6) Ambient heat - too hot outside

Every above reason lowers detonation threshold.

Detonation is extremely destructive. Temperature can reach 18000 F at the center of the explosion, and nothing in the market (forged pistons, rods, etc) can withstand sustained detonation. Also, at 6000+rpm detonation can occur ~50 times per combustion champer in one second.

*ANY* detonation *MUST* be addressed.
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Old 05-12-2001, 09:09 AM   #18
Jon Bogert
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Thanks Aaron, that's the plan.

MiXer, I'm not sure why you need to use that tone... are you a 3rd grade teacher used to speaking to children? Or did you just copy that out of Corky Bell's book...
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Old 05-12-2001, 09:27 AM   #19
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I copied it out of Corky Bell's book. I just thought ppl wanted to know.

The "tone" wasn't intentional... English is my 2nd language. Sorry.
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Old 05-12-2001, 10:52 AM   #20
Kevin Thomas
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I can not see anyone not liking 5psi of boost unless you are used to turbos. I have been driving with 5psi of boost since Mid-1999 and I am completely satisfied. I have yet to turn up the boost. *No Nos jokes* If a wee 5psi can take me from mid 17's to high 15's with an autotranny, I can't see how someone wouldn't be satisfied with their RS going from high 15's-low 16's to low 14's with 5psi of boost. Hell, it'll go to high 13's on a cold night. Just don't let the evil boost monsters get you.
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Old 05-12-2001, 09:18 PM   #21
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Miscellaneous ramblings...

I did some gtech times before and after my small legacy RHB5 turbo kit, with 5 psi, rising rate fuel pressure regulator, JCS torque chip II, and 2.5" exhaust. I live at 6,000 feet, so the times will be a little slower than at sea-level:

Before while stock, 65 degrees outside and 91 octane:

0-60 = 8.98 sec
qtr mile = 16.7 sec @ 84 mph

After 5 psi turbo, 35 degrees outside and 96 octane:

0-60 = 6.22 sec
qtr mile = 14.65 sec @ 97.5 mph

Those times are consistent with "200 hp to the wheels" in a 3,050lb car with driver according to some HP calculators, even though we think it was more like 175-185hp based on other similar kits. According to Shiv, the RHB5 is good for a max of about 230hp, and I don't know how close I was to that when I ran those qtr mile times.

Another thing is that the hp/lb boost varies from kit to kit, and runs between 10-15hp for each lb of boost. For example, a 3" exhaust kit will make more power per lb of boost, a lightweight flywheel and lightweight pulley will let the turbo spool up faster and show more power on the dyno, proper tuning with programable ECU will make a difference, a higher compression ratio and larger displacement will make a difference, better intercooler efficiency will make more power, less drop in boost across the intercooler will show improvement, etc...

Where blaster88 says 7.35lbs = 240-250hp, that would be 11 hp/lb which sounds right. But, Shiv gets 296hp at the wheels from 13lbs of boost vs 98 hp on the same dyno without a turbo = 198 hp gain = 15 hp per lb. If he gets 360hp at the flywheel with 20% drivetrain losses, it is still 15hp per lb of boost using 165hp stock. So, there is certainly no "set in stone" magic number for hp/lb of boost.

Lastly, at 6,000 feet we have less roblems with detonation and can run higher boost. That's why I can run 7 psi on 91 octane, and 8-9 psi with octane booster, and no timing controller. However, we tested our prototype boost referenced ITC this weekend, and I could run 9+ psi with 91 octane gas!! EGT's were only 1475 vs 1400 without the ignition retard. As we fine tune it and work out the bugs I can try 10 psi. I can't wait till it is ready for sale, and I won't need octane booster anymore. Of course, I will probably add water injection as a backup. They say I can run 12-14 psi on 10:1 pistons with that...

Then I'll have a chance to blow up the tranny again

Larry www.SubaruPlanet.com
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Old 05-13-2001, 04:25 AM   #22
blaster88
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I said it was GROSS oversimplification. taking the ratio of boost:atmospheric pressure and multiplying by stock will give you a neighboorhood.

Other mods affect performance, obviously, so hp is not strictly a function of boost. Also, obviously, the TEC II can make a significant increase in power from a turbo Impreza. Shiv's numbers (I thought it was 265 at the wheel, but either way) show at least a doubling of stock horsepower at 13 lbs max, given he has a programmed boost curve.

My point is that the ASR kit, as shipped, is probably not going to turn 240-250 hp in an Impreza. I am sure it is capable of it, with the addition of engine control like the TEC II.

Hmmmm. I think I may be talking myself into one. Must...control...urge...to...spend...
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Old 05-14-2001, 01:15 AM   #23
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ImprezaRS.com

who's RRFPR are you using? can you link me?

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Old 05-14-2001, 01:30 AM   #24
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Blaster is right about other mods making a huge difference in what your HP yield is at a given amount of boost. I have a knife edged crank, forged pistons, ported heads w/ valve job, and a cam. That combo @ 5 or 7 PSI boost is producing allot more power than it would stock. Having boost will go a distance toward overcoming restrictive intake and heads but doing it right makes allot of positive difference too.
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