Oil and the Ford Escort 1.9 Liter Motor

Background
Anyone who reads the circle track press or who has dyno’d 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.

The Symptoms and the “Whys”
The symptoms of this problem are pretty straight forward.  They are: 1) the motor won’t 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 you’ve 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, here’s what’s really happening.

The lifters are losing their oil.  The valves aren’t opening completely and the motor can’t 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.  It’s not the electronics punishing you for less-than-adept driving.

The reasons that the lifter bleed-down doesn’t occur on the dyno are that typically the oil won’t be anywhere near as hot as on the track and you don’t 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, we’ve never exceeded 180.  I think this is true for most people.  That 90 degree temperature spread makes a big difference in the oil’s viscosity and therefore the oil pressure in the motor.

Here’s What To Do
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 doesn’t increase lift and does cost horsepower.   Unfortunately I can’t 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, I’ll 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, I’ve been known to partially tape off the oil cooler air flow exit to raise the oil temperature.

Miscellaneous Oil Info
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 won’t help.  I try to run Valvoline products both for their quality and their support of racing.  I’ll substitute Mobil 1 if I can’t find Valvoline synthetic at the moment.   I don’t run any oil additives.  I believe that changing motor oil every other event appears to prolong the productive life of the motors.

Below you’ll find a table of info on Valvoline’s 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
 
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
 
Viscosity Index (VI) 160 149 152
Phosphorus, % wt. Max. 0.10 0.10 0.10
Rev. 2/21/98
Feedback
I welcome your comments or ideas on this information.  Feel free to drop me a line via “Comments for the Bro’s”.  

Barry

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