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#1
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New Overheating Clue
Just got some new information about the overheating that occasionally plagues our cars. Seems that the water pump for the 4 cylinder Subaru engines has a tendency to cavitate over 6700 rpm. It might be that our water pump has the same problem. Cavitation occurs because the water pump creates an area of lower than atmospheric pressure that allows the coolant to boil at a lower temperature, creating steam bubbles in the coolant stream. That might be why a higher pressure radiator cap would help this problem, causing the bubbles to collapse sooner, before they have an opportunity to create havoc.
I have had a lot of difficult finding an "import" size high-pressure radiator cap. I have ordered a Crucial 1.4 bar cap (approx 20 psi), from Crucial Racing Products. Will be at Pocono next Friday and will post how it works.
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____________________________________________ 95 LS-i Red, 31,xxx; bone stock for now; Daily Driver 94 LS-i Emerald Pearl, 106,xxx,; 246 whp; Tomyx snorkus and HKS Cold air intake; PWR aluminum radiator, silicone hoses; Inline thermostat; enhanced coolant routing; external power steering and oil coolers; Phenolic intake manifold spacers; 2004 WRX 5 speed transmission; ACT Clutch Kit, Heavy Duty Pressure Plate, Lightweight flywheel, performance disc; Group N motor mounts; ‘07 WRX 4-pot front calipers, cryo-treated slotted Tribeca rotors; Hawk HPS ferro-carbon pads; Frozenrotor rear slotted rotors; SS brake lines, Axxis Ultimate pads; Rota Torque 17x8 wheels; 245/40-17 Bridgestone RE01-R's; Koni inserts with Ground Control coilovers, Eibach springs; K-Mac camber/caster adjustable strut mounts; Urethane swaybar bushings; Bontrager rear sway bar; Urethane differential bushing; Custom Whiteline adjustable rear lateral links; Outlaw Engineering forged underdrive pulley; custom grind Web intake and exhaust cams (11 mm lift, 250° duration); solid lifters; CP custom aluminum forged 11 to 1 pistons, Brian Crower coated SS intake & exhaust valves; Brian Crower upgraded springs w/ titanium retainers; NGK sparkplugs; RallyBob (Bob Legere) ported and polished cylinder heads; Eagle H-beam rods; ACL Bearings; Cometic Head gaskets; ARP head studs & fasteners; Hydra Nemesis EMS; Wideband O2 sensor; 740cc Injectors; Walbro 255lph fuel pump; Upgraded WRX starter; Equal length SS headers (3 into 1); dual Magnaflow cat converters; 2 into 1 into 2 SS exhaust with Bullet muffler; OT Fiberglass hood; Oil pressure gauge; Programmable shift light, 2017 Subaru Forester XT, metallic dark gray, 29,xxx 2005 Porsche 911 Turbo S Cabrio, 24,xxx 2006 Subaru Outback LL Bean, 166,xxx sold 92 LSL Dark Teal, Smallcar Shift Kit - sold Last edited by shotgunslade; 03-22-2008 at 10:57 AM. |
#2
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Any aftermarket STi cap will fit our cars. I have a 18.6psi ( I think) Sti radiator cap on my OEM radiator right now
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Former: 1994 Barcelona Red(x2), 1995 Brilliant Red, 1992 Liquid Silver, 1992 Ebony(x2), 1992 Pearl White (x2) Current: 2017 Ford Raptor 2017 Kawasaki KLR 1995 Guards Red Carrera 1995 Spec-ish Miata - track car 1957 CJ-5 |
#3
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Quote:
Good point. Now we just have to find a better water pump -Bill
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Retired NASA Rocket Scientist Most famous NASA "Child" - OSIRIS-REx delivered samples from asteroid BENNU to Earth in Sept. 2023 Center Network Member #989 '92 Fully caged, 5 speed, waiting for its fully built EG33 '92 "Test Mule", 4:44 Auto, JDM 4:44 Rear Diff with Mech LSD, Tuned headers, Full one-off suspension '92(?) Laguna, 6 spd and other stuff (still at OT's place) My Locker |
#4
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Quote:
~ Chris
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2020 Subaru Outback Touring - Wife's first Subaru 2005 Volvo V70R - 5-cylinder love! :Heart: ** SOLD **1998 Subaru Legacy 2.5GT Wagon - MOST RELIABLE car I've ever owned ** SOLD **2006Subaru WRXSTi (Former "Boxer4Racing.com / Continential Tire" STi) - Built EJ22t block / EJ207 JDM STi "big port heads" - 9,000rpm MONEY PIT!!! ** SOLD ** 1995 "Tree-Hugger Green" SVX L AWD(5 MT) --- "Gumby" 130K miles #399 in MY95, my original love... |
#5
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Damn... and I just ordered a new water pump to go with my 60k mile service parts, too...
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#6
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Dan,
Do the wiz kids at your firm have the tools to model the EG33's water pump? (yeah, I know we're flowing water, not air) -Bill
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Retired NASA Rocket Scientist Most famous NASA "Child" - OSIRIS-REx delivered samples from asteroid BENNU to Earth in Sept. 2023 Center Network Member #989 '92 Fully caged, 5 speed, waiting for its fully built EG33 '92 "Test Mule", 4:44 Auto, JDM 4:44 Rear Diff with Mech LSD, Tuned headers, Full one-off suspension '92(?) Laguna, 6 spd and other stuff (still at OT's place) My Locker |
#7
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New Overheating Clue
<<New Overheating Clue>>
what kind of over heating problems do the SVX have? I have never heard of this with the SVX I had. most of the overheating problems that Subaru owners have are self inflicted (they don't know how to properly bleed the air out of the system. ) |
#8
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This is "track-induced" overheating, not every day, run-of-the-mill overheating
-Bill
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Retired NASA Rocket Scientist Most famous NASA "Child" - OSIRIS-REx delivered samples from asteroid BENNU to Earth in Sept. 2023 Center Network Member #989 '92 Fully caged, 5 speed, waiting for its fully built EG33 '92 "Test Mule", 4:44 Auto, JDM 4:44 Rear Diff with Mech LSD, Tuned headers, Full one-off suspension '92(?) Laguna, 6 spd and other stuff (still at OT's place) My Locker |
#9
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What he said. Running at high loads above 3,000 RPMs for longer-than-normal periods.
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#10
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How do you do that
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Paul 1969 Corvette 1995 SVX L Safety Option Package, HID's & Awsome Braking (Svxfilies/TomsSVX), JDM Clear Corners, JDM Boxer Engine cover, Transmission Cooler, AND NOW JDM FOLDING MIRRORS! 1995 Corolla 2003 Highlander |
#11
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RallyBob has a good post on how they do this for the EG33RS race car. Think it's in the 285 WHP thread.
-Bill
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Retired NASA Rocket Scientist Most famous NASA "Child" - OSIRIS-REx delivered samples from asteroid BENNU to Earth in Sept. 2023 Center Network Member #989 '92 Fully caged, 5 speed, waiting for its fully built EG33 '92 "Test Mule", 4:44 Auto, JDM 4:44 Rear Diff with Mech LSD, Tuned headers, Full one-off suspension '92(?) Laguna, 6 spd and other stuff (still at OT's place) My Locker |
#12
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Those of us with MT's, at the track, will continuously take the engine over 7000 rpm. I've hit 7200 at the end of straights when I didn't want to upshift before the corner.
I'm wondering if an underdrive pulley might also help. Any comments from underdrive pulley users. Any downsides? Dead batteries, overheating while idling, etc? Bill: Yes we have the software, and even have the expertise to do liquids. What we don't have is the expertise to do a 2 state problem. Pumping cavitation is a very very complex problem. Just because we have a set of chisels doesn't make us Michelangelo. Dan Dan
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____________________________________________ 95 LS-i Red, 31,xxx; bone stock for now; Daily Driver 94 LS-i Emerald Pearl, 106,xxx,; 246 whp; Tomyx snorkus and HKS Cold air intake; PWR aluminum radiator, silicone hoses; Inline thermostat; enhanced coolant routing; external power steering and oil coolers; Phenolic intake manifold spacers; 2004 WRX 5 speed transmission; ACT Clutch Kit, Heavy Duty Pressure Plate, Lightweight flywheel, performance disc; Group N motor mounts; ‘07 WRX 4-pot front calipers, cryo-treated slotted Tribeca rotors; Hawk HPS ferro-carbon pads; Frozenrotor rear slotted rotors; SS brake lines, Axxis Ultimate pads; Rota Torque 17x8 wheels; 245/40-17 Bridgestone RE01-R's; Koni inserts with Ground Control coilovers, Eibach springs; K-Mac camber/caster adjustable strut mounts; Urethane swaybar bushings; Bontrager rear sway bar; Urethane differential bushing; Custom Whiteline adjustable rear lateral links; Outlaw Engineering forged underdrive pulley; custom grind Web intake and exhaust cams (11 mm lift, 250° duration); solid lifters; CP custom aluminum forged 11 to 1 pistons, Brian Crower coated SS intake & exhaust valves; Brian Crower upgraded springs w/ titanium retainers; NGK sparkplugs; RallyBob (Bob Legere) ported and polished cylinder heads; Eagle H-beam rods; ACL Bearings; Cometic Head gaskets; ARP head studs & fasteners; Hydra Nemesis EMS; Wideband O2 sensor; 740cc Injectors; Walbro 255lph fuel pump; Upgraded WRX starter; Equal length SS headers (3 into 1); dual Magnaflow cat converters; 2 into 1 into 2 SS exhaust with Bullet muffler; OT Fiberglass hood; Oil pressure gauge; Programmable shift light, 2017 Subaru Forester XT, metallic dark gray, 29,xxx 2005 Porsche 911 Turbo S Cabrio, 24,xxx 2006 Subaru Outback LL Bean, 166,xxx sold 92 LSL Dark Teal, Smallcar Shift Kit - sold |
#13
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Quote:
Agreed. But I thought you were hiring "budding Michelangelos" out of college? This would be a case to ask Subaru Engineering how they model cavitation. Shame we don't know anyone "on the inside" -Bill
__________________
Retired NASA Rocket Scientist Most famous NASA "Child" - OSIRIS-REx delivered samples from asteroid BENNU to Earth in Sept. 2023 Center Network Member #989 '92 Fully caged, 5 speed, waiting for its fully built EG33 '92 "Test Mule", 4:44 Auto, JDM 4:44 Rear Diff with Mech LSD, Tuned headers, Full one-off suspension '92(?) Laguna, 6 spd and other stuff (still at OT's place) My Locker |
#14
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Quote:
For a street engine I typically slow the water pump down by the same amount it is overdriven. In other words, if the pump spins faster than the crank by 10% (example: 6600 rpm pump speed @ 6000 rpm crank speed) I will reduce that speed to 90% of the crank speed (5400 rpm pump speed @ 6000 rpm crank speed). Nothing scientific about it, just trial and error on my part. For racing I will knock the overall pump speed down by 35-40%, but this can create overheating at slower speeds so it's not recommended for road use. |
#15
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Hey, Bob, not to get too off topic in this thread, but do you happen to have the part number on that PS pump?
-Bill
__________________
Retired NASA Rocket Scientist Most famous NASA "Child" - OSIRIS-REx delivered samples from asteroid BENNU to Earth in Sept. 2023 Center Network Member #989 '92 Fully caged, 5 speed, waiting for its fully built EG33 '92 "Test Mule", 4:44 Auto, JDM 4:44 Rear Diff with Mech LSD, Tuned headers, Full one-off suspension '92(?) Laguna, 6 spd and other stuff (still at OT's place) My Locker |
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