Hi Mike,
I'm going to take a guess that this is to do with your 6lt project. From memory you were going with the E38 controller so I'll tailor some info on that.
With the LS1 PCM, the majority of tuners would go with a MAF-less tune, but with the late model E38, there is no clear favorite. Some of the reasons for this ( in my opinion ) are...
- Tuning knowledge.
- Larger stock MAF size.
- Speed of the E38 PCM.
- Additional tables in the E38 PCM.
A good example of the differences in capability of the stock E38 controller is the fact that EFILive sees no compelling reason to offer full Custom Operating Systems for the E38. The usual response to requests for an E38 COS is "It's already in the stock calibration".
So I guess I should list some advantages of each type of tune.
MAF:
- The MAF will compensate for air density / IAT automatically.
- The E38 uses the MAF signal to operate certain tables directly.
- If you have a street car and EPA rules require the MAF to be "in place and operational", then there is less chance of trouble.
- The MAF can be tuned just like the VE table, so accurate fueling can be achieved.
MAFless:
- The MAF can be a restriction in the intake path and reduce max airflow at WOT. removing it also removes this restriction.
- There is no "delay" in air flow calculations from the MAF. Because the MAF is usually some distance from the TB, it takes time for air flow changes to reach it and then for the MAF sensors to react.
- For larger CAMs, if the MAF is too close to the TB, a "reversion" condition can occur where the airflow over the MAF sensors becomes unstable and the MAF reports incorrect data.
There are probably lots more, but those would be a few common traits of the two tunes.
Of the two, there is no doubt that a MAF tune is quicker and easier to set up, especially for a daily driver and more so if the car is an auto. One of the areas that seems to rely heavily on the MAF is the fuel dynamics. In a manual car you can get lean spikes on gear changes unless you do a lot of work when running MAFless. In the end though, I think MAF or MAFless will be a personal choice. To help that choice along, I'd think about the following...
[indent]
- What is the vehicle going to be used for?
- Daily driver, lean toward MAF
- Weekend drag car, lean toward MAFless
- Bit of both.... either.
- How will the vehicle be used?
- Lots of mid throttle work, gear changes, lean toward MAF.
- Only really idle or WOT, MAFless.
- Bit of both.... either.
- What are your tuning skills like?
- Bit of a beginner and not too sure, leave the MAF.
- Tuning god and can convert lambda to AFR for any given fuel type in your head.... MAFless
- Somewhere in between and want to learn, either.
Again from memory, I think you were setting up a boat, so it will probably respond pretty well to a MAFless setup, given you won't be on and off the throttle all the time ( unless we are talking jet boat racing ). I think the main reason for MAFless in drag racing, is the fact that the MAF can take longer to respond to changes, and when all the action can be over in less than 10 seconds, every millisecond counts. If on the other hand the action lasts for 10 minutes, the MAF response may be made up for in other areas ( like dynamics ) that may make it a better option.
Simon.