I absolutely agree with everything that has been said . The power band
for supercharged & turbo charged engines are different, although
improved turbo designs have widened the lower rpm power range. I can
only speak from my SC experience.
When I first decided to attempt a SC engine reliability was & street
ability was a priority. My original motor was tired so I decided to pull
the engine & give it to a local speed shop I had known for years but had
no personal mechanical experience with. Never having built a motor from
the ground up & wanting my first summer with the new motor to go well I
opted to let them build the motor. After getting the motor back it was
in the car & driving with in a couple of weeks. The added power was
intoxicating. The car ran well but never seemed 100%. I learned allot
over the next two years about how to build a motor the hard way. With in
500 miles after putting a fresh motor in the motor developed leaks from
the front engine block, rear seal & oil pan. The oil pressure was anemic
& the car was using a QT of oil every 500 miles by next summer. I drove
the car like this for two years until I couldn't take it any longer. It
became evident that the engine rebuild was done poorly to say the least.
In the fall I pulled the motor again. After doing a tear down I
discovered the handiwork of a looser. Five out of six top piston rings
were cracked, the valve guides were knurled , not replaced, gaskets were
missing & lots of silicone RTV was holding the motor together. The list
goes on & on but you get the idea. It's amazing what black spray paint
can hide.
This time I did my homework first. It was time for me to try my first
engine rebuild. I located a machine shop that builds pro drag engines
that was recommended through friends who had personal experience with
them. I met with the owner for over an hour & discussed the rebuild & my
past disaster. He was a great guy with a stellar reputation. He agreed
to do the machine work & I would collect the parts a do the assembly,
this way I could check everything and only blame myself. We discussed
specs & improved tolerances with a blower in mind. By assembling the
motor piece by piece I saw things that could be improved or pay special
attention to during the build. After all is said and done , this has
been the best mechanical experience I have ever had.
To make an all together long story short, this motor has about 15,000
miles on it . It doesn't leak a drop, uses a Qt of oil every thousand
miles & runs really strong. I don't abuse it , but it is driven the way
it was intended. The key to a solid engine rebuild is quality parts,
preparation & execution. The motor has to be built for the end result in
mind. If an experienced mechanic builds a motor with badly machined
parts & sloppy tolerances the end result is a piece of crap.
This motor uses 6-7 lbs of boost , produces gobs of torque & HP between
2,500-5,000 rpm . Keep in mind that a typical normally aspirated high
performance engine has higher compression & more carbueration to make
high rpm HP. The blower makes user friendly street HP with out winding
up to rpm extremes. I'm using 7.75:1 stock compression & can pull a tree
out of the ground at 2,500 rpm. The boost & increased stress is
momentary. A high compression performance motor is under additional
stress all the time & especially at high rpm. The comparison I'm making
are for street performance motors. I'm not sure how this would apply to
race engines & how a SC triumph engine would perform under long time
constant boost.
Time will tell what long range effects will have but I will be honest &
report the good as well as the bad. Keep in mind that Dick Taylor has
been running a turbo's 6 for years with his engines lasting well over
100,000 miles at higher boosts than I using.
--
Mitch Seff
Oceanside, N.Y.
75 TR6SC
http://www.triumphowners.com/384
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