Adjustable Fuel Pressure Regulators
02-09-2003, 06:30 PM
#16
The 81 is the vehicle that I am talking about. I just took everything apart for the 4spd auto transplant, so I installed the MSDS headers, and will install the ADJ FPR. I wanted to wake it up a bit with the headers and X-over and dual 2.5 to the back. The 4spd really has pepped it up, but not much seat time because I have been looking for a place to fab the exhaust up.
02-10-2003, 06:22 AM
#17
Rennlist Member
Hi Brendan,
Yes, I noticed your non standard '81 car with a 4 speed auto...........
With the mods you have done, if the exhaust does help scavenge a bit better, then a rising rate FPR would probably help a bit.
But there may be other ways to tickle the CIS system up a bit.
I am sure others on the list can help you there.
Yes, I noticed your non standard '81 car with a 4 speed auto...........
With the mods you have done, if the exhaust does help scavenge a bit better, then a rising rate FPR would probably help a bit.
But there may be other ways to tickle the CIS system up a bit.
I am sure others on the list can help you there.
02-10-2003, 12:02 PM
#18
John - This is an 81 USA, so it has L-Jet fuel injection. The CIS would be a euro motor.
I bought an adj. FPR from 928spec, but I don't think its rising rate though....
I bought an adj. FPR from 928spec, but I don't think its rising rate though....
02-10-2003, 06:54 PM
#19
Rennlist Member
hi Brendan,
Oh well, shows how much I know about US market cars !
You can richen up the mixture across the whole range with an L Jet by adding a resistor in series with the water temperature sensor. I made up a switch box with values form zero ohms up to about 1000 ohms. You can then find the optimum.
If you only want enrichment at WOT you could use the WOT switch and Some circuitry (Like a relay) to add the additional resistor just at that point.
Another trick we used to use on L Jet (I had an old Opel Manta with a 2.4l long stroke engine) was to reduce the spring tension in the MAF. This will also richen up the action.
Oh well, shows how much I know about US market cars !
You can richen up the mixture across the whole range with an L Jet by adding a resistor in series with the water temperature sensor. I made up a switch box with values form zero ohms up to about 1000 ohms. You can then find the optimum.
If you only want enrichment at WOT you could use the WOT switch and Some circuitry (Like a relay) to add the additional resistor just at that point.
Another trick we used to use on L Jet (I had an old Opel Manta with a 2.4l long stroke engine) was to reduce the spring tension in the MAF. This will also richen up the action.
02-10-2003, 08:05 PM
#20
Ah, the old spring trick. 944 guys have played with that.
But that resistor trick is a new one on me!
Can you expand on that a bit?
But that resistor trick is a new one on me!
Can you expand on that a bit?
02-11-2003, 12:08 PM
#21
Rennlist Member
OK Brendan - the L jetronic brain compensates for a cold engine, which needs a richer mixture (due to fuel condensation).
To control this it uses the water temperature sensor (usually known as temp sensor 2) for an engine temperature signal. The sensor is negative temperature coefficient, so it has a high resistance when cold, and a lower one when hot.
So if you put an additional resistor is series with the sensor, it fools the brain into thinking the engine is cooler than it actually is. Then it richens up the mixture.
This will richen the mixture across the whole range, so you may get worse mileage per gallon.
Loosening off the spring also gives a quicker response to rapid throttle opening.
Hope this helps.
John
To control this it uses the water temperature sensor (usually known as temp sensor 2) for an engine temperature signal. The sensor is negative temperature coefficient, so it has a high resistance when cold, and a lower one when hot.
So if you put an additional resistor is series with the sensor, it fools the brain into thinking the engine is cooler than it actually is. Then it richens up the mixture.
This will richen the mixture across the whole range, so you may get worse mileage per gallon.
Loosening off the spring also gives a quicker response to rapid throttle opening.
Hope this helps.
John