Oil and the Ford Escort 1.9 Liter Motor |
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Background |
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Anyone who reads the circle track press or who has dynod a Spec Racer Ford
motor knows the following: The lower the oil pressure, the more horsepower the motor
produces. One very convenient way to lower the oil pressure is to run lighter weight
oil. The problem with this is that in SRF racing, the horsepower gains only occur on
the dyno -- and not on the track. In
fact, on the track, the SRF racer with the lowest oil pressure probably is making the
least HP. Several well-known racers have wondered why their motors had low
horsepower after they had spent a lot of money on dyno time peaking their
motors -- including the use of fancy zero weight type oils. The balance
of this page explains why, what to do, and a few favorite tips about oil. |
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The
Symptoms and the Whys |
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The symptoms of this problem are pretty straight forward. They are: 1) the
motor wont wind up past the low 5,000 rpm range, 2) the motor starts missing in
turns at high rpm, 3) the motor takes a long time to recover from an over-rev. Many
people have described this situation as the car goes into a default mode in the
electronics, or seeming like youve hit a rev-limiter built into the EEC system
(the problem sounds very similar to a drag racer sitting on the line, at full throttle,
with the rev limiter holding the engine back). Well, heres whats really
happening. The lifters are losing their
oil. The valves arent opening completely and the motor cant
breathe. This is due to insufficient pressure to keep the hydraulic lifters full of
oil while they are being repeatedly compressed by the valve rocker arms. The higher the
rpm, the less time the lifter has to refill with oil -- with the refill amount determined
both by pressure and the time available to refill. As time goes on at high rpm, the
lifters gradually lose their oil fill and the lift drops. This continues until the
motor starts missing and self-limits the rpm. This is not conducive to winning
races. As an aside, when you over-rev the motor and the motor starts missing, what
is happening is that the lifters have come high enough out of their bores to totally lose
their oil. The burbling that occurs afterward is the result of the time
it takes to refill the lifters with oil. Its not the electronics punishing you
for less-than-adept driving.
The reasons that the lifter bleed-down
doesnt occur on the dyno are that typically the oil wont be anywhere near as
hot as on the track and you dont typically hold sustained high rpm on the
dyno. We routinely measure 270 degrees F oil temp in the pan of our motors. On
the dyno, weve never exceeded 180. I think this is true for most people.
That 90 degree temperature spread makes a big difference in the oils viscosity and
therefore the oil pressure in the motor. |
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Heres
What To Do |
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The secret is to run enough oil pressure to keep the lifters fully open at your
maximum anticipated rpm (probably around 6,000) and no more. Higher oil pressure
doesnt increase lift and does cost horsepower. Unfortunately I cant
tell you what the optimum pressure is -- it appears to vary by motor and motor age.
I can only tell you this, if the car is basically running ok (i.e. good pull off the
corners), but has a miss at high rpm, try a heavier oil. In general I run a 10w-30 weight synthetic oil. If
the weather is really hot, Ill blend in some 20w-50. I never run one of the
zero weights because of the loss of valve lift when the oil gets hot. In
very cold weather, Ive been known to partially tape off the oil cooler air flow exit
to raise the oil temperature. |
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Miscellaneous
Oil Info |
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I frequently get asked about what to do with oil. Here are my
suggestions. On a new motor, run mineral based oil (not synthetic) until the
motors parts are fully broken in. I believe this takes 3 to 4 typical race
weekends (practice, qualifying, warm-up & race) to accomplish. After that,
switch to synthetic oil. Switching earlier wont help. I try to run
Valvoline products both for their quality and their support of racing. Ill
substitute Mobil 1 if I cant find Valvoline synthetic at the moment. I
dont run any oil additives. I believe that changing motor oil every other
event appears to prolong the productive life of the motors. Below youll find a table of info on Valvolines
SynPower full synthetic oil. Note the Kinematic Viscosity at 210F to
understand why we sometimes mix in some 20w-50.
Typical Properties |
SAE
5W-30 |
SAE
10W-30 |
SAE
20W-50 |
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Gravity, API |
34.9 |
34.9 |
34.0 |
Flash Point, COC, C |
242 |
250 |
260 |
Pour Point, C |
-42 |
-42 |
-42 |
MRV TPI Viscosity, cP |
9100(-35) |
7400(-30) |
9500(-20) |
CCS Viscosity@ -10C, cP |
--- |
--- |
3200 |
-20C, cP |
--- |
2300 |
--- |
-25C, cP |
2300 |
--- |
--- |
Kinematic Viscosity@ 100C, cSt |
10.07 |
10.30 |
20.55 |
40C, cSt |
58.36 |
64.04 |
157.28 |
210F, cSt |
10.31 |
10.53 |
21.12 |
100F, cSt |
63.90 |
70.44 |
174.58 |
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Viscosity Index (VI) |
160 |
149 |
152 |
Phosphorus, % wt. Max. |
0.10 |
0.10 |
0.10 |
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Rev. 2/21/98 |
Feedback |
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I welcome your comments or ideas on this information. Feel free to drop me
a line via Comments for the Bros. Barry |
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