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has anyone built a 383 using stock tbi setup?

I would think that anyone going this direction would have an Air'Fuel ratio meter piggy-backed onto the stock O2 Sensor. May not be the ideal wide band for tuning, but at least you'd have an idea of where it's running.

Also, when the TBI 454 first came out a friend of mine with a 1t DRW Cab-over camper tow rig logged the resistance values of the computer's temp sender. Then he built a box with a rotary switch and several different resistors. In normal driving the switch was set to by-pass out to the sender. When he started to pull a hill he'd switch to a "cooler" setting. My understanding was that the computer would comp by adding more pulse width. He said it took some fiddling to find the best for all cases resistor, but once he'd found it that the engine pulled hills better and ran cooler too.
This may not be the best idea, but it's intersting anyway.
 
HarryH3 said:
This one line tells the story... The reason that it's weak on the top end is that the injectors simply can't provide enough fuel to feed the engine. It's running WAY too lean. Lean burn = excessive heat. Excessive heat = melted pistons. You're risking your engine... :doah:
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On the contrary, I've datalogged the computer many times and the AFR is pretty steady in my RPM range (I rarely take it into 4000+ RPM). The problem with my setup is the crappy stock TBI heads.
 
The AFR gets 100% ignored on OBD I computers once the throttle goes to wide open. The ECM just assumes that it's giving the right amount of fuel. As long as you keep the revs low, it will survive for some time but you're playing with fire. Exceed the capability of the injectors while the engine is under load and the combustion chamber temps skyrocket. Do it for too long and aluminum begins to melt. The result is ugly and expensive.
 
HarryH3 said:
The AFR gets 100% ignored on OBD I computers once the throttle goes to wide open. The ECM just assumes that it's giving the right amount of fuel. As long as you keep the revs low, it will survive for some time but you're playing with fire. Exceed the capability of the injectors while the engine is under load and the combustion chamber temps skyrocket. Do it for too long and aluminum begins to melt. The result is ugly and expensive.
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I'm aware of that, that's why I haven't been romping it... very little highway travel, mostly street. The computer tracks up to 3200 RPM I believe -- that range is fine, so I don't take it into 4000 range unless I'm trying to pass or whatever.... don't really need to otherwise. It's got some balls on the low end.
 
If I'm not mistaken, the O2 sensor doesn't simply "quit" at WOT, it's input is simply ignored. Barring a wideband, I'd simply datalog and make sure that the O2 sensor is staying on the "rich" side under those circumstances. Horribly inaccurate at anything other than 14:1 yes, but at least you'll know you are on the rich side, and not lean. :)
 
Most commonly WOT or nearly so takes the computer out of closed loop. Once in open loop there isn't much need for an O2 sensor. This is addressing pre-OBDII computers. No idea what those do.
 
No need, right, but the oxygen sensor doesn't just quit working, right? Input ignored, yes, it's pre-programmed (which is why you can't just say it runs right without datalogging) but I do believe you can still get data from it.
 
SnackPack said:
I'm aware of that, that's why I haven't been romping it... very little highway travel, mostly street. The computer tracks up to 3200 RPM I believe -- that range is fine, so I don't take it into 4000 range unless I'm trying to pass or whatever.... don't really need to otherwise. It's got some balls on the low end.
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Another good reason to go with EBL. This has a full fuel table right up 6 thousand and granade me to death!:D
 
dyeager535 said:
No need, right, but the oxygen sensor doesn't just quit working, right? Input ignored, yes, it's pre-programmed (which is why you can't just say it runs right without datalogging) but I do believe you can still get data from it.
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As long as the exhaust gas temp is above some thresold temp (600*f is the number commonly bandied about - no idea if it's correct or not) the sensor will produce a signal. What the computer does with it is another story......

This is why I figured that anyone in the development stage would have a gauge piggy-backed onto the sensor. Datalogging is good for sorting out what to do next, but some warning of impending doom while driving would be good too.
 
Never make large changes, or as you mention, you go from impending doom to imminent danger. :)
 
I know what you mean... When learning to program the chips, it was fascinating seeing what changes would yield certain differences. I would try a couple things just to see how they affect the engine while not moving (like trying to get idle steady) and sometimes be surprised by the results. It takes patience.

It's kinda like flying a plane... it's all in small adjustments.
 
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