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Stripped Down 4.0 OHV


stano316

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Hello Everybody,

We have a 98 Ford Ranger with 4.0 OHV that we race in the 24 hours of Lemons Race series. From last season to this season we have been in the process of ripping everything out that is not needed to run. My question is what is the bare minimum as far as sensors and wiring that is needed to let a 4.0 l run. We have Tuning software from SCT, so we can work and play with quite a bit. We are stripping down the wiring harness to make it easier to trouble shoot problems later on that may happen during the races. Thanks.

 


RonD

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1995 and up Rangers used EEC-V(104 wire) computers so needed a bit more input from sensors than the EEC-IV(60 wire) computers
But the EEC-Vs are better for tuning

Crank sensor is the big kahuna, won't run with out that, sets base spark and injector timing
CAM sensor is used for sequential fuel injection, better power
MAF/Air Temp sensors are in one 6 wire unit in 1998, and you need them for best air/fuel mix
ECT(engine coolant temp) sensor, computer will run in Open Loop without this sensor to tell it coolant is warmed up.
TPS, acts like an accelerator pump did for a carb, MAF sensor detects changes in air flow when throttle opens, but there is a delay, the TPS gives computer an instant "heads up" to increase fuel flow when you step on the gas.

O2 sensors, two upstream and one down stream, in 1995 and up
The upstream O2s are needed to give computer feedback on the air/fuel mix in Closed Loop operation
Downstream is basically just used to tell if Cat converters are working OK

"In Gear" sensor, Digital Range sensor on autos, clutch pedal switch on manuals, when in neutral computer activates a 3,000rpm REV Limiter

Speed sensor, computer will often go into Open Loop if it is not getting reliable MPH, in 1998 thats from rear axle VSS via GEM module behind radio
GEM converts 20,000+ pulse per mile from rear axle VSS to the 8,000PPM the computer and speedometer are pre-set for
You can buy separate interface for that but GEM doesn't weigh that much

IAC Valve is a control not a sensor but is needed for proper idling and choke functions on cold starts
 
Last edited:

stano316

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Great, thanks
 

RonD

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Oil pressure and coolant temp SENDERS are just for the dash board gauges
Some models also had an oil level sensor, also just for dash board "light"

Forgot the EGR and EVAP systems
If there is an EGR system then engine will run better with it than without it, but if you are able to tune the engine then it can be removed, but CEL will come on from DPFE sensor removal
EGR system cools the cylinders to lower NOx emissions under load, as engine load increases so does engine temp, adding exhaust gases to air/fuel mix slows down the heat up process in the cylinders.

Secondary effect is when cylinders run cooler during acceleration computer can run a more aggressive spark for better power, WITHOUT fear of Pinging on 87 octane fuel.
4.0l OHV was not prone to pinging so might not matter in that case.
Just a heads up if you do remove EGR system and do get pinging you will need to adjust spark to prevent that.

EVAP is a strictly an emission system, no change in engine operation without it.
EVAP prevents gas fumes that are produced in the gas tank as you drive, gas sloshes around, from escaping to the atmosphere.
EVAP applies a small vacuum to the gas tank when engine is running, this sucks out any fumes and they are burned in the engine.
Computer does monitor EVAP system so CEL will come on if it is removed
 

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