1926 Model T RPU
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Update.
So i am probably closing in on 1000 miles in this RPU. I drive it whenever the sun is out and its been great. That said, i did have one issue that i was not expecting.
At speeds under 5 mph, when the front wheels hit a stepped series of bumps with no steering or braking input, they would oscillate from side to side (aka death wobble).
I went through all the steering hardware and found nothing loose (everything is new). I also went through the steering box adjustments and took out all the slop i could.
Axle is 7* caster and I am running 1/8" toe.
Still had the same result. So i started researching steering dampers / stabilizers. I opted for the VW style damper.
Built some mounting tabs and dropped it in. No more wobble. Steering feels tighter and more stable.
The Science Of Straight Axles - Street Rodder Magazine
So i am probably closing in on 1000 miles in this RPU. I drive it whenever the sun is out and its been great. That said, i did have one issue that i was not expecting.
At speeds under 5 mph, when the front wheels hit a stepped series of bumps with no steering or braking input, they would oscillate from side to side (aka death wobble).
I went through all the steering hardware and found nothing loose (everything is new). I also went through the steering box adjustments and took out all the slop i could.
Axle is 7* caster and I am running 1/8" toe.
Still had the same result. So i started researching steering dampers / stabilizers. I opted for the VW style damper.
Built some mounting tabs and dropped it in. No more wobble. Steering feels tighter and more stable.
The Science Of Straight Axles - Street Rodder Magazine
tfeverfred
Well-Known Member
I use 1/16" to 1/8" toe in. Check out the link above in his post. It's a very good read.
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took this to its first cruise night. it got lots of attention. i was parked between some classic hot rods and really noticed how small and low this thing really is.
Fail on my part for not getting some pics.
I do have an update. My commute is a little over 1 mile, so the engine never really gets up to temp.
Sitting in the parking lot watching everyone drive way while you wait for your engine to come up to temp sucks too.
My solution to this was to add a remote start system. $39 and took me about an hour to install.
Fail on my part for not getting some pics.
I do have an update. My commute is a little over 1 mile, so the engine never really gets up to temp.
Sitting in the parking lot watching everyone drive way while you wait for your engine to come up to temp sucks too.
My solution to this was to add a remote start system. $39 and took me about an hour to install.
one finger john
Active Member
I'll ask the obvious question - a working thermostat should get it up to operating temperature in minutes. Cooling system too efficient ? Is the engine properly tuned ?
John
John
tfeverfred
Well-Known Member
Just curious..... how are those seats working out for you?
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perfect.
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Short version: TBI runs better in closed loop.
MODES OF OPERATION:
The ECM uses voltage inputs from several sensors to determine how much fuel to give the engine. The fuel is delivered under several conditions, called "Modes." All modes are controlled by the ECM, and are described below.
Starting Mode:
When the ignition is first turned ON, the Electronic Control Module (ECM) turns ON the fuel pump relay for two seconds, allowing the fuel pump to build up system pressure. On Heavy Duty models, a fuel module will override the ECM two second timer and the fuel pump will run for twenty seconds and then shut OFF if the vehicle is not started. This circuit corrects a hot restart (vapor lock) during high ambient temperature conditions. If the engine is immediately started, the fuel pump will continue to operate. If the key is left in the ON position, but the engine is not started, the ECM will turn the pump OFF. The fuel pump will remain OFF until the ECM detects the crank signal, or in the case of a faulty fuel pump relay, the oil pressure switch detects approximately 4 psi of oil pressure which will then bypass the fuel pump relay.
Fuel delivery from the injectors (which deliver fuel in all operating modes) is controlled by changing the amount of time the injectors are turned on or "pulsed" by the ECM. The ECM checks the Coolant Temperature Sensor (CTS), Throttle Position Sensor (TPS), and the crank signal, and determines the proper air/fuel ratio for starting. This ranges from 1.5:1 at -36°C (-33°F) to 14.7:1 at 94°C (201°F).
Clear Flood Mode:
If the engine floods, it may be cleared by pushing the accelerator pedal down all the way. The ECM then pulses the injector at a 20:1 air fuel ratio. The ECM holds this injector rate as long as the throttle stays wide open, and the engine speed is below approximately 600 rpm. If the throttle position becomes less than approximately 80%, the ECM returns to the starting mode.
Run Mode:
The run mode has two conditions, called OPEN LOOP and CLOSED LOOP.
Open Loop:
When the engine is first started, and engine speed is above 400 rpm, the system goes into OPEN LOOP operation. In OPEN LOOP, the ECM ignores the signal from the Oxygen sensor, and calculates the air/fuel ratio based on inputs from the coolant temperature and Manifold Absolute Pressure (MAP) sensors.
The system will stay in OPEN LOOP until the following conditions are met:
1. The oxygen sensor has a varying voltage output, showing that it is hot enough to operate properly. (This depends on temperature)
2. The coolant temperature is above a specified temperature.
3. A specified amount of time has elapsed after starting the engine.
Closed Loop:
The specified operating conditions vary with different engines, and are stored in the programmable read only memory (PROM). When these conditions are met, the system goes into CLOSED LOOP operation. In CLOSED LOOP, the ECM calculates the air/fuel ratio (injector on-time) based on the signal from the oxygen sensor. This allows the air/fuel ratio to stay very close to 14.7:1.
Acceleration Mode:
The ECM responds to rapid changes in throttle position and manifold pressure or air flow, and provides extra fuel.
Deceleration Mode:
The ECM responds to changes in throttle position and manifold pressure and reduces the amount of fuel. When deceleration is very fast, the ECM can cut off fuel completely for short periods.
Battery Correction Mode:
When battery voltage is low, the ECM can compensate for the weak spark by:
1. Increasing the amount of fuel delivered.
2. Increasing the idle speed.
3. Increasing the ignition dwell time.
Fuel Cut-off Mode:
No fuel is delivered by the injector when the ignition is OFF. This prevents dieseling. Also, fuel is not delivered if no reference pulses are seen from the distributor, which means the engine is not running. This prevents flooding. Fuel cut-off also occurs at high engine rpm, to protect internal engine components from damage
Testing and Inspection
fletcherson
Well-Known Member
Back when the TPI stuff came out, I became involved in swapping them into older carbed cars, etc, and the wiring harness kits were very expensive, so I learned how to make them work.(7 wires out of the massive oem harness) One can fool the computer into doing what one wants with the addition of specific resistors in specific locations, i.e. the etc(temp sensor) circuit, etc... I am NOT as involved in the late model stuff, but I think you could design a alternate circuit to bipass the actual engine temp to fool the ecm into going into open loop sooner with the flip of a switch. That was a pretty common performance upgrade, as the goal was to reduce the engine temp to achieve a denser mixture to get more fuel through the engine. A 160 thermostat, was common, but we had to then address the coolant fan, etc... there were various work arounds, but resistors were very cheap and effective. That may or may not have enough affect on the other monitors to set a hard trouble code, but with some homework and trial and error, it's doable. I'm too old and out of patience at this stage, but back in the day, that was a challenge....beat the system! lol.
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you hit the nail on the head. i have a pre 86 block with a 93 TBI intake.
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