Performance PROMs for carbed turbo buicks?

[riviera_turbo82]

Good afternoon everyone--

I wonder if anyone knows of a source, or someone with sufficient skills to tinker, to provide a performance chip for my '82 Turbo Riv? Many years ago, I had installed a Kenne Bell 1TXB cam in this car, and really didn't give much thought to the gas mileage. Fast forward to 2007, and gas above $3 a gallon, and now I am very sensitive to the cost of gas.

With the stock ECM and PROM and the 1TXB cam, the computer just keeps telling the carb to dump more fuel into the engine at cruising speed. I believe the lower vacuum reading from the 1TXB cam makes the computer think the engine is under heavier acceleration... all the time. I leaned down the carb, and even went to smaller primary jets and metering needles, but still can't get the mileage good enough to be "presentable". I'm averaging about 14 mpg, and not driving very aggressively.

Before I go the route of swapping back in a stock camshaft to satisfy the computer, I wanted to ask-- what are my chances of finding a performance chip or credible chip burner?

I had considered going the route of a MAP signal voltage modifier, but am concerned (with the turbo engine's going from vacuum to pressure in the MAP signal) that this approach may not be fruitful. Anyone have success in that respect?

Thanks, and best regards, Christopher Burns
'82 Turbo Riv, in Rochester, New York

 

[b4black]

How did you change the primary jets on an ECM controlled carb?


Have you ever used a scan tool to check what the ECM is seeing? With a o2 sensor, the ECM can only work with rich and lean. If it stays rich all the time, it will throw a code. When has the sensor last changed? It might just be "lazy".

 

[riviera_turbo82]

Good morning b4black--

I changed the main jets and metering rods the very same way you would do in a non-CCC quadrajet. I have probably a dozen CCC carburetors hanging around that I've amassed over the years, several for my turbo Riv, and several for the series of Olds 307 cars I've had (Toronado, Fleetwood Brougham).

Different years of all these cars have used different sets of primary jets and metering rods as the "ideal", factory combination; the jets and the rods are numbered, a higher number (bigger diameter) is leaner for the metering needles; a higher number (bigger opening) is richer in the jets. I presume this is information not commonly known, as I was not able to find anyone to sell me replacement primary rods and jets. And there was certainly variation year by year... My original 17082249 had 50U primary needles, and 70 jets. A Tomco rebuilt 17081243 had 45U needles and 67 jets. A 17082143 I got on eBay came to me with 48U needles and 68 jets. Given my troubles, I rebuilt the carb currently on my car and put in the leanest combination of the above, the 45U/67. I assume nobody has really spent much time exploring the variations in jets and needles in the CCC carb environment, as each stock engine presumably has an "ideal" combination of needles, jets, and the measured height relationship between the M/C solenoid travel and the base of the jets.

To your additional questions-- my latest, ACDelco O2 sensor is now about three months old, and sends a very sensitive, responsive signal. I do have a scan tool, an OTC Monitor Elite, and without it I would never have known quite what was going on. While the O2 reading does vary "normally", at cruise the computer maintains a mixture with an O2 reading of about .67-.75 volts, not the target .47 or so turning point between lean and rich. I can set my idle needles to get the M/C solenoid to cycle at a dwell of about 30 degrees, and or an O2 voltage around .47 volts. But again, at anything beyond about 10 or 15% throttle opening, the vacuum signal due to my higher-lift cam falls low enough to fool the (stock PROM) ECM into thinking the engine is working hard, and thus it runs it richer.

To your comment about throwing a code, if I let the car idle for anything more than about five minutes, I will get the Check Engine light as the O2 sensor stops seeing a varying oxygen reading. As soon as I rev it up, it goes away-- this has always happened with this car.

So back to the original question, any ideas on who can burn me a new PROM with a modified vacuum signal curve?

Thanks again,

Christopher Burns

 

[Freddie's Buick]

....To your comment about throwing a code, if I let the car idle for anything more than about five minutes, I will get the Check Engine light as the O2 sensor stops seeing a varying oxygen reading. As soon as I rev it up, it goes away-- this has always happened with this car......

In the 1981 service manual it states:

On some models O2 sensors will cool off at extended idle. In order for the O2 sensor to operate it can not be less than 600F.

At that 'cool off' point there will be no signal coming from the O2 sensor.
This puts it into an 'open loop' operation, (ie: no variation). Some ECM's will throw code 44, (Lean condition/Bad O2 sensor).

To restore proper operation run the engine at part throttle .

So, as you see on some of these cars this is normal.