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Educate me on SD / MAF

1K views 4 replies 3 participants last post by  EZA 
#1 ·
As I have stated before I'm new to LS engines but reading all I can to increase my knowledge. My project is a 98 S10 step-side short bed, L33,
4L65E, 3:42 / 8.6 DB. Only modification to the engine is an LS6 intake manifold and a ZO6 (LS3) cam and hopefully a set of cast exhaust manifolds. I have just read an article on speed density vs mass air flow sensor, so I have a basic understanding. Which do you think would be the better for a street driven vehicle as describe above and why. Can the engine above be set up to run with either, I using the pcm that came with the L33 and a fully integrated CPW harness.
 
#2 · (Edited)
So Speed Density is old school... and was only used OEM for a few short years. The benefit of Speed Density is its a lot easier to dyno tune for especially on high horse engines. Its done for a few other reasons. MAF sensor position and placement, as well as correct MAF scaling in the tune, is critical to making a MAF tune work well. Unfortunately this can be tough if the MAF sensor is located too close to an elbow, or the filter is too close etc, MAF sensors need very laminar streamlined flow to read correctly. Throttle tip-in is also a bit harder to tune well with MAF on bigger displacement engines since the delta between tip in and WOT is larger in absolute airflow g/s so getting the scaling right is a bit tougher. It also works well for custom intake setups e.g. holley/edlebrock mid-rise/high rise w/ 4b tb etc. Many aftermarket self-learn systems such as Holley's HP EFI are functionally working on SD principles allowing them to omit the MAF altogether in some setups.

I started out MAF tuned, and it ran ok and made good power, but always had some idle/hot start and throttle tip in issues. I had it retuned this year using an SD tune, and it runs way the heck better. Picked up a few horses on the dyno, but more importantly has great start hot and cold, and much better tip in throttle response. My MAF is still there and still reading, just being ignored by the PCM, but I can still use it for validation if I want to.

The downside of SD is elevation change. if you drive from sea level up the rockies you're gonna have a problem usually. However if you're like me and your elevation doesn't change more than a few hundred feet one way or the other in your local driving area, then SD is fine.

MAF also handles seasonal change and temperature/humidity extremes better provided the scaling is correct, whereas SD can take more dyno tuning time under different conditions to really flesh out the tables to run well into winter, though I drive late spring/summer/early fall only so not an issue to me.

Any LS engine of any year can be set up to run either.

You can and will find shops that are expert in, and prefer one or the other. my first tuning for MAF was done by SPI Tuning on Dundas, Ontario, and the SD tuning was done by AGP Performance in Newmarket, Ontario. Both well regarded very good shops, just happens my build works better under SD setup.

If someone was using a crate LS3 with x58 PCM and DBW TB, and a stockish type intake/maf placement, there's no reason or benefit to going SD and MAF will work better. But on older 24x systems, earlier gen MAF sensors, and wonky placement or engine build parameters, SD can make life a lot simpler.
 
#3 ·
Just the input I was looking for, thanks! I live in Florida, no change in elevation here and only a few months out of the year that the temperature goes under 90 F. I'm thinking SD might be the way to go for me, so now I will really start to research the tech. side. I will also check with CPW as I will be doing a totally integrated harness for my swap. Thanks again!
 
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