86 l98 cam
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3rd Gear
Joined: Nov 2007
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86 l98 cam
hey guys, just a quick question. I read someplace that an efi engine that uses a mass air flow can adapt to changes like cames air filters etc. Is this true because i wanted to put a little bigger cam in my l98. I just am not sure if the computer can make the adjustments for it or not.
Safety Car
Joined: Sep 2003
Posts: 3,598
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From: Orange County NY
St. Jude Donor '10-'11-'12-'13
To a degree, yes. Once in closed loop, the ECM will make the necessary fueling adjustments and they will be stored in memory. But, the ECM can only adjust by so much either way (rich or lean). If more fueling adjustment is needed, a modified PROM tune is required.
The timing curve does not adjust. If the cam you choose would benefit from more timing in some areas and less in others, again you'd need to modify the PROM tune.
In both cases, a cam that is only slightly bigger than stock wouldn't necessarily require a tune in a MAF car.
The timing curve does not adjust. If the cam you choose would benefit from more timing in some areas and less in others, again you'd need to modify the PROM tune.
In both cases, a cam that is only slightly bigger than stock wouldn't necessarily require a tune in a MAF car.
Last edited by byebyeL98; Dec 10, 2007 at 12:58 PM. Reason: add "in a MAF car"
Racer
Joined: Oct 2006
Posts: 275
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From: Brentwood CA
To a degree, yes. Once in closed loop, the ECM will make the necessary fueling adjustments and they will be stored in memory. But, the ECM can only adjust by so much either way (rich or lean). If more fueling adjustment is needed, a modified PROM tune is required.
The timing curve does not adjust. If the cam you choose would benefit from more timing in some areas and less in others, again you'd need to modify the PROM tune.
In both cases, a cam that is only slightly bigger than stock wouldn't necessarily require a tune in a MAF car.
The timing curve does not adjust. If the cam you choose would benefit from more timing in some areas and less in others, again you'd need to modify the PROM tune.
In both cases, a cam that is only slightly bigger than stock wouldn't necessarily require a tune in a MAF car.
Couldn't agree more!! 
Navigator
Joined: Jul 2005
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hey guys, just a quick question. I read someplace that an efi engine that uses a mass air flow can adapt to changes like cames air filters etc. Is this true because i wanted to put a little bigger cam in my l98. I just am not sure if the computer can make the adjustments for it or not.
Duration @ 0.050 I 212 E 218
Lift I 0.449 E 0.456
Lobe Seperation 112
With this cam, which is slightly more agressive then the stock cam, I found that the engine was running slightly lean across the full operating RPM range. When I looked at the BLM readings they indicated that the ECM was compensating by about 10% across the full RPM range (BLMs were all at about 140 or so). Since the INT numbers were almost right at 128 it was obvious that the ECM was able to compensate for the new cam.
The car ran fine without any ECM changes, although I did end up burning a custom chip to add a little more fuel and bring the BLM numbers closer to 128.
Based on my experience, you should be able to use a cam that is slightly more agressive than the one I used, and the ECM should still be able to compensate without a custom chip.
Note that the ECM only compensates for a rich/lean condition when it is running in closed loop. When the engine is cold and the ECM is using predefined settings, it will not run as well.
