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TBI set up in big block '82 Eldo

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  • Cody Carson
    Several requests have been made for my TBI set up info. I use the stock Eldorado computer & PROM chip. It runs a larger GM TBI. This is an experimental set up,
    Message 1 of 1 , Aug 8, 2002
      Several requests have been made for my TBI set up info. I use the stock Eldorado computer & PROM chip. It runs a larger GM TBI. This is an experimental set up, and I do not guarantee that it will work for your application. I only was able to log 212 miles on my swap before the salvage yard 472 started to knock, so I don't have enough data to prove that it works continuously, however, the only trouble code I got during those miles was the TCC indicator letting me know that the car would not shift into 4th gear (a problem that was there prior to pulling the 4100 out-and was next on my list to fix). All indications so far are that this works, but I am prepared to switch to a 4bbl carb or Holly Projection if it does not.
      I did a lot of reading on the stock computer system operations for the different years of Eldorados that had the same body style. Starting in '82 there was no knock sensor (if memory serves, the '82-85 computers were the same in the 4100 cars except for some PROM chip data differences that should not effect anything for the swap.) My reading told me that the computer was primarily concerned with proper air to fuel mix ratios. It adjusts timing by air temp and density-even adjusts for altitude-but not for knock or internal engine noise. It uses one O2 sensor for the mixture in closed loop. It is a simple Digital Fuel Injection that has a very useful feature- the onboard diagnostics allows me to check trouble codes while driving by pressing two buttons on the climate control and getting an instant readout on the screen-no need to take it in to the dealer. This OBD system is primitive in that the computer has no way of knowing what size the engine is, or the base timing setting, or the compression ratio, or the internal noise that the engine makes. In operation it is similar in the type of system sold in aftermarket TBI applications except that I cannot adjust fuel and timing curves via a laptop----and I should not need to thanks to the digital operation when in closed loop. The only area of concern I had was in the engine warm up stage when the computer would operate the 472 as if it was a 250.
         My goal was to put in an engine that was twice as big, use fuel injectors that were rated twice as much with a TBI that flowed twice as much air, run a compression ratio that was equivalent, set the base timing so that the advance was tuned to the larger engine, and let the computer do the rest, by transferring ALL sensors from the 4100 engine to the 500, and transfer the TPS and idle control motor from the 4100 TBI to the new TBI. My goal was a 500 with a 670 CFM TBI, and eventually that is the set up that will be in the engine. The 500 I got from the salvage yard had a cracked block, the 472 I got as a replacement looked like it had a recent overhaul. I was unable to find a 670 CFM TBI so I wound up with a 400 CFM unit off of a 200 HP '90 Seville. (I went ahead with the swap so I could see if the idea would work before I spent the extra money on a new Chevy truck 454 TBI and then had to drill and tap mounting holes for the external idle control motor.) I transferred all sensors and smog equipment except for the catalytic converter (when budget allows, I will mount two high flow cats under the car so I won't get any fines and so muffler shops won't be so afraid of the car.)
      I mounted mechanical gages to watch how the computer manages the engine, and so far so good-now I just need to get the time and money to do the swap all over again, this will be the third time.
        I wanted to the swap this way not only for the gas mileage benefits, but also because the computer operates my MPG sentinel, cruise control, converter lockup, fourth gear shift, fuel pump, and several other functions that I can't remember at present. Other than the chrome valve covers, and chrome breather, I wanted the car's engine compartment to appear as a factory stock model, and not attract any undue attention to the modifications. I wanted to build the Eldorado that GM should have, and do it the way they could have.

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