Carb versus EFI

clutchdust

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OK guys, so I bought an early 240z a couple weeks ago that's already been converted into a track car. It has already been gutted and, well, it's basically a tube frame car at this point. The only thing that's still Datsun is the skin. It does have a Datsun L6/5-speed in it that I will use as my foundation. Currently as it sits, all I know it needs to run is an intake, carb, fuel cell and battery. The car was set up by the previous guy to run the shitty Datsun FI system. That's going in the shitcan, because it is basically shitty. However, I am considering going with a salvage yard TBI system. My concern is that the engine I intend to put in next year might require high octane gas, even leaded gas. I'm not sure but I don't think I can run leaded gas with an O2 sensor, which would be required if I end up going FI. Or am I wrong?
The other option is obviously to go carbureted and be done with it. My concern there is setting up a carburetor for high G track events. I'm guessing I will be fighting fuel starvation at some point and wondering what I can do to minimize that. Suggestions?
 
just run tbi open loop. closed loop wont help you much without a cat converter anyways. Even in open loop TBI is light years better then a carb.
 
Only if your open loop tuning is dead on accurate, otherwise it will run better in closed loop, it has nothing to do with a cat con.
 
Only if your open loop tuning is dead on accurate, otherwise it will run better in closed loop, it has nothing to do with a cat con.

BUT most O2 sensors will not tolerate lead too well, but they can be had for lead tolerance....

:goodnight:
 
Toss the whole damn thing.

I'm wondering how hard it would be to put an LS-1 in that car. Then you could at least work with shit some of us know. Not me though. It'll sound better than that 6 popper too,.

Far be it for me to interject into things i have no experience in, but. I thought you're in open loop at high throttle openings anyway which is all the time on a track. Also it takes some time for an O2 sensor to crap up with lead. Buy a new one every year or find out how to clean them up. How many hundreds of miles do you put on a track only car anyway? Not that many. If i remember right the Bosch 02 sensor were good for 10K miles before they crap up with leaded gas.
 
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Far be it for me to interject into things i have no experience in, but. I thought you're in open loop at high throttle openings anyway which is all the time on a track.

An 81 would be that way. All the new port injection is in closed loop after a 30 second warm up, and stay that way.
 
Far be it for me to interject into things i have no experience in, but. I thought you're in open loop at high throttle openings anyway which is all the time on a track.

An 81 would be that way. All the new port injection is in closed loop after a 30 second warm up, and stay that way.

I thought O2 sensor could only measure 14.7. For max acceleration you'll have to be richer say 12.5. How does it tune to that point if it can't see it?
 
Far be it for me to interject into things i have no experience in, but. I thought you're in open loop at high throttle openings anyway which is all the time on a track.

An 81 would be that way. All the new port injection is in closed loop after a 30 second warm up, and stay that way.

I thought O2 sensor could only measure 14.7. For max acceleration you'll have to be richer say 12.5. How does it tune to that point if it can't see it?

Doug or TT would know. I do not.
 
Far be it for me to interject into things i have no experience in, but. I thought you're in open loop at high throttle openings anyway which is all the time on a track.

An 81 would be that way. All the new port injection is in closed loop after a 30 second warm up, and stay that way.

I thought O2 sensor could only measure 14.7. For max acceleration you'll have to be richer say 12.5. How does it tune to that point if it can't see it?

Doug or TT would know. I do not.

O2 sensors can measure more then 14.7 - but you need a wideband O2 sensor. The short story behind that is narrow band O2 sensors are designed to set a specific voltage at a EGT. With a warmer attached (wideband) to the O2 sensor, it can measure a wider range of EGTs temperatures.

As for leaded O2 sensors, that's beyond my knowledge base.... lead kills the cells in cat. converters, but the situation has never come up with running leaded fuel and a sensor... would the lead adhere to the sensor and make it read a different temperature (more accurated, produce a different voltage at specific temperatures?) IDK.
 
Toss the whole damn thing.

I'm wondering how hard it would be to put an LS-1 in that car. Then you could at least work with shit some of us know. Not me though. It'll sound better than that 6 popper too,.

Far be it for me to interject into things i have no experience in, but. I thought you're in open loop at high throttle openings anyway which is all the time on a track. Also it takes some time for an O2 sensor to crap up with lead. Buy a new one every year or find out how to clean them up. How many hundreds of miles do you put on a track only car anyway? Not that many. If i remember right the Bosch 02 sensor were good for 10K miles before they crap up with leaded gas.

Wideband O2 sensors can last for awhile using leaded gas if you are careful to make sure they are heated properly. I have heard racers using O2 sensors preheat the sensor before starting to prolong its life. My friend at Competition Marine has told me he has been successful in cleaning them. I will have to ask him how that's done.

Common Turtle, You mean to tell me you run full throttle on the track at all times?? That old pumpkin hauler must be a real squeaker. :lol:
 
Well, at least for the time being, this has become a moot point. Ran across and bought yesterday a 280 parts car that was already equipped with a dual Weber set up. Will be going with that until I'm done with the other engine, then I'll worry about this comparison.
 
I thought O2 sensor could only measure 14.7. For max acceleration you'll have to be richer say 12.5. How does it tune to that point if it can't see it?

Heres the long and shoprt of it for NB02 sensors.

From RR's paper:

The proportional and integral fuel correction logic is complex. There
is no way that I can cover all aspects of the ecm logic. This paper
is designed to give a working view of what the ecm is trying to
accomplish. I have also covered some changes that can help when
tuning hot street engine.

The proportional PID term starts with the O2 sensor reading, and ends
with a correction to the final calculated PW. The PID proportional term
always works in the opposite direction of the immediate rich/lean O2
sensor reading.

The purpose of the PID proportional controller term is twofold. First,
it is used to attain the desired AFR quickly. Second, it is used to
maintain the switching of the O2 sensor about the desired AFR point.

The PID controller term starts with the O2 Error Term. This is the
amplitude of error (or difference), between the O2 sensor and the
desired O2. This value is used as a lookup index for the actual
proportional error term.

The combination of the proportional term and the INT term is referred
to as the closed loop correction term (CLT). When in open loop, neither
the proportional term or the INT term as used.

There are two filtered O2 sensor values kept by the ECM. One is a fast
filtered value that follows the changing O2 sensor reading closely. The
second is a slow filtered value that lags the changing O2 sensor reading. end "

Now the other fueling is based in part on the NB resulting BLM.

WOT uses desired value (12.5/1?) last BLM seen and also a calc based on CID injector size and fuel pressure values( a setting called base pulse constant in .bin)
 
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