Blown Engines?
11-29-2003, 06:38 AM
#4
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The racing EVO spec engines which were running around 600hp (and I am talking real hp not 996 turbo board hp) suffered from throwing a rod, apparently it was always the same rod. This was overcome by a little secret mod used by top teams which involved turning one bank of pistons around 180deg to balance out the big forces caused in an inherently out of balance design of the flat 6. The bonus of this mod was a 5% increase in power due to the extra efficiency gained - does my car have this mod ? - of course
The stock rods are a weak point when bringing the torque above 700NM (500lb/ft ish) despite having EVO spec Porsche Motorsport rods, my engine managed to bend one of them - it was noticed at rebuild so didn't have a grenade to deal with. Carrillos are the answer
The stock rods are a weak point when bringing the torque above 700NM (500lb/ft ish) despite having EVO spec Porsche Motorsport rods, my engine managed to bend one of them - it was noticed at rebuild so didn't have a grenade to deal with. Carrillos are the answer
11-29-2003, 09:36 PM
#6
Burning Brakes
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I've seen one 993tt engine gernade on the front straight at Willow Springs.
I followed up and it appears the lad thought he was running racing fuel. He was but it was a mix which turned out to be 94 octane. The detonation caused the spark plug insulator to seperate in the cylinder which at speed created some unfortunate damage.
I followed up and it appears the lad thought he was running racing fuel. He was but it was a mix which turned out to be 94 octane. The detonation caused the spark plug insulator to seperate in the cylinder which at speed created some unfortunate damage.
11-30-2003, 06:09 PM
#7
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I blew up a stock 993 Varioram motor in turn 8 at Willow Springs was
trying to keep up with a 944 Turbo, it let go around 5200 RPM's.
It happened on the straightaway section of turn 8 felt like the gearbox locked up and then a loud bang sametime rear end wanted to come around
smoke was filling the cockpit, pushed the clutch in, regained control and
coasted back into the pits. It all lasted about 2 seconds. Once in the pits
my co-driver tolled me it was done, oil poured out onto the exhaust and
on the track luckly nobody crashed. Pulled the motor out and saw one of the the rods was sticking out of the case, rod was missing a bolt. Motor
survied a couple of misshifts, and many rev-limiter cut outs, lasted about
500 miles before it let go.
My recommendations now: No revs over 5500 RPM if stock 3.6 motor,
if turbo I would keep it down to 5000 RPM, keep a close eye on the
gauges, don't want to run it hot, pay attention to any unfamiliar noises
if it dosen't feel or sound right pull in (unless your winning). In my case
it let go without a warning should of changed those stock rod bolts.
Regards,
John
trying to keep up with a 944 Turbo, it let go around 5200 RPM's.
It happened on the straightaway section of turn 8 felt like the gearbox locked up and then a loud bang sametime rear end wanted to come around
smoke was filling the cockpit, pushed the clutch in, regained control and
coasted back into the pits. It all lasted about 2 seconds. Once in the pits
my co-driver tolled me it was done, oil poured out onto the exhaust and
on the track luckly nobody crashed. Pulled the motor out and saw one of the the rods was sticking out of the case, rod was missing a bolt. Motor
survied a couple of misshifts, and many rev-limiter cut outs, lasted about
500 miles before it let go.
My recommendations now: No revs over 5500 RPM if stock 3.6 motor,
if turbo I would keep it down to 5000 RPM, keep a close eye on the
gauges, don't want to run it hot, pay attention to any unfamiliar noises
if it dosen't feel or sound right pull in (unless your winning). In my case
it let go without a warning should of changed those stock rod bolts.
Regards,
John
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11-30-2003, 11:56 PM
#8
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John - You might be just kidding. I hope so. My car doesn't make full power until 5000 rpm - I have learned to avoid the rev limiter most of the time but I let it run. I ease the clutch out and run through the first 4-5 gears shifting just before the rev limiter at least a few times each month.
I think that if your 993 bought it at 5500 rpm, something went wrong. A manufacturing defect. The defect could have been in the way it was put together or a metalurgical defect etc..
I have asked this question so that I could get a better feel for whether I should expect my modified 993 tt engine to have a short life. So far - so good. I think my Porsche likes to be driven relatively hard and I think it's designed to take it. That's why I like it so much.
I owned a 1976 911 with a modified 2.8 ltr high compression carburated engine. Drove it hard with good results - owned a 1991 C2 Cab - drove it hard - had a transmission / flywheel problem but never a hickup from the engine.
I was looking for some horror stories but I am not hearing anything unreasonable I'm happy to say.
Mike
I think that if your 993 bought it at 5500 rpm, something went wrong. A manufacturing defect. The defect could have been in the way it was put together or a metalurgical defect etc..
I have asked this question so that I could get a better feel for whether I should expect my modified 993 tt engine to have a short life. So far - so good. I think my Porsche likes to be driven relatively hard and I think it's designed to take it. That's why I like it so much.
I owned a 1976 911 with a modified 2.8 ltr high compression carburated engine. Drove it hard with good results - owned a 1991 C2 Cab - drove it hard - had a transmission / flywheel problem but never a hickup from the engine.
I was looking for some horror stories but I am not hearing anything unreasonable I'm happy to say.
Mike
12-01-2003, 12:44 AM
#9
RL Technical Advisor
Mike:
These engines are very durable as long as they are not overreved with the stock rod bolts. These will only take being stretched so many times before yielding. We've done quite a number at the 480-520 HP level and as long as they are fed good gas (94 octane), they hold up quite well.
The only other vulnerability are the OEM valve spring retainers. These are sintered metal and we replace them with titanium ones when the car will used on the track.
These engines are very durable as long as they are not overreved with the stock rod bolts. These will only take being stretched so many times before yielding. We've done quite a number at the 480-520 HP level and as long as they are fed good gas (94 octane), they hold up quite well.
The only other vulnerability are the OEM valve spring retainers. These are sintered metal and we replace them with titanium ones when the car will used on the track.
12-01-2003, 03:32 AM
#10
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Steve is right, and highly respected. My motor blew up under race conditions (high-revs all day long). At the enduro races a lot of the turbo cars don't even finish, motor is under a lot of stress, the heat from the turbos and high boost they are running will cause things to fail. The
turbos are always in the front of the pack but it comes with a heavy price
tag.
On the street a turbo car is hard to beat I've heard of a stock TT with over a 100K miles and still running strong proves Porsches are reliable cars, as long as long the maintance is kept up. Hopefully my engine builder will
finish by Christmas and I will be a happy camper.
Regards,
John
96 TT
72 911's
72 Bug rally car
turbos are always in the front of the pack but it comes with a heavy price
tag.
On the street a turbo car is hard to beat I've heard of a stock TT with over a 100K miles and still running strong proves Porsches are reliable cars, as long as long the maintance is kept up. Hopefully my engine builder will
finish by Christmas and I will be a happy camper.
Regards,
John
96 TT
72 911's
72 Bug rally car
12-02-2003, 01:01 AM
#13
Three Wheelin'
Carrerars3.6,
You said your engine survived a couple of missed shifts -- seems to me this is why it blew up later, assuming it was overrevved when the shifts were missed.
TB993TT,
I thought a flat-6 IS inherently balanced, as are a straight-6 and a (60 degree) V-12. Can anyone clarify this?
You said your engine survived a couple of missed shifts -- seems to me this is why it blew up later, assuming it was overrevved when the shifts were missed.
TB993TT,
I thought a flat-6 IS inherently balanced, as are a straight-6 and a (60 degree) V-12. Can anyone clarify this?
12-02-2003, 01:44 AM
#15
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The stock 993TT motors are very strong: at least I think so.
- I was running 1BAR boost for 2 seasons on my Internally STOCK motor with the K24s on the car. I drive the car pretty fast and have a heavy foot and I never had any problems with it.
- Your enemy is HEAT. Keep the heat down and you will be fine.
- I had NO auxiliary Oil cooler installed (which everyone keeps saying is a must have if you dont want to grenade a motor). The temp on my car never went above the half-way mark even while idling in traffic.
- You can't blow an engine by "over-revving" while accelerating.. That's what the rev-limiter is for. The only way you can blow the engine is by missing a downshift (ie. putting it in 2nd instead of 4th while in 5th).
Some recommendations:
- Remove the dust tray from the bottom of the engine (that plastic shield they install down there is meant to keep debris from getting into the motor and turbos but it also keeps in alot of heat).
- Install free-flowing mufflersor get the bypass pipes like I had. Also, racing cats (ie. FVD) help keep the exhaust moving along and reduce the backpressure tremendously. It helps to dissipate the heat better and keep the turbos running efficiently.
- Get an auxiliary oil cooler (TurboS or GT1 style). It will help even more if you track your car or are in an extremely warm climate.
- I was running 1BAR boost for 2 seasons on my Internally STOCK motor with the K24s on the car. I drive the car pretty fast and have a heavy foot and I never had any problems with it.
- Your enemy is HEAT. Keep the heat down and you will be fine.
- I had NO auxiliary Oil cooler installed (which everyone keeps saying is a must have if you dont want to grenade a motor). The temp on my car never went above the half-way mark even while idling in traffic.
- You can't blow an engine by "over-revving" while accelerating.. That's what the rev-limiter is for. The only way you can blow the engine is by missing a downshift (ie. putting it in 2nd instead of 4th while in 5th).
Some recommendations:
- Remove the dust tray from the bottom of the engine (that plastic shield they install down there is meant to keep debris from getting into the motor and turbos but it also keeps in alot of heat).
- Install free-flowing mufflersor get the bypass pipes like I had. Also, racing cats (ie. FVD) help keep the exhaust moving along and reduce the backpressure tremendously. It helps to dissipate the heat better and keep the turbos running efficiently.
- Get an auxiliary oil cooler (TurboS or GT1 style). It will help even more if you track your car or are in an extremely warm climate.