what is the exact reason(s) speend density is better?
04-23-2011, 07:03 PM
#1
TECH Fanatic
Thread Starter
iTrader: (19)
Join Date: Sep 2007
Location: houston TX
Posts: 1,497
Likes: 0
Received 0 Likes
on
0 Posts
what is the exact reason(s) speend density is better? a friend and I were talking about the pros and cons of running speed density. the extent of my knowledge of EFI doesnt run past the Fbodys so my only legitamate answer was to eliminate the restriction in the intake path.
He generally stays with the Grand Am/Grand Prix's and Cobalts, just about anything with a 3.8 liters and we got into a debate about why Im setting my camaro up to run SD.
anybody feel like enlighteneing me? searching pulled up nothing FML
He generally stays with the Grand Am/Grand Prix's and Cobalts, just about anything with a 3.8 liters and we got into a debate about why Im setting my camaro up to run SD.
anybody feel like enlighteneing me? searching pulled up nothing FML
04-24-2011, 12:24 AM
#2
it isn't better. maf is better unless you are doing something to screw up the maf like maxing it out with boost (ie. too much airflow) or confusing it with a HUGE cam.
I am running speed density due to driveability issues under 1500 RPMs with a MAF but I have a totally different motor than the one that came in my car.
for a street or street/strip car, run the MAF fo sho.
I am running speed density due to driveability issues under 1500 RPMs with a MAF but I have a totally different motor than the one that came in my car.
for a street or street/strip car, run the MAF fo sho.
04-26-2011, 07:36 PM
#3
One isn't better than the other for a certain reason. If you have a tuner that knows what he is doing, either is just as good as the other.
You will feel the difference with the SD tune as far as it being more responsive quicker. With the MAF, it has to adjust.
Not sure I am explaining it worth a crap. But if you stomp on it with an SD tune, you should feel it "jump". It is more seat of the pants feel.
If you drag race any, and you were able to run a MAF tune and then an SD tune, you would be more consistent with the SD tune.
Either way, the tune is in the tuner. As long as you have a good tuner, SD or MAF tuned will work great.
People will tell you that if you live where the temp constantly changes, you need to keep your MAF, but if you run a search on google, you will see many people in those states running SD tunes and not having issues.
You will feel the difference with the SD tune as far as it being more responsive quicker. With the MAF, it has to adjust.
Not sure I am explaining it worth a crap. But if you stomp on it with an SD tune, you should feel it "jump". It is more seat of the pants feel.
If you drag race any, and you were able to run a MAF tune and then an SD tune, you would be more consistent with the SD tune.
Either way, the tune is in the tuner. As long as you have a good tuner, SD or MAF tuned will work great.
People will tell you that if you live where the temp constantly changes, you need to keep your MAF, but if you run a search on google, you will see many people in those states running SD tunes and not having issues.
04-26-2011, 08:25 PM
#6
But would you agree that their operating systems are designed from the ground up to run in SD where GM MAF operating systems are not, but as a back up for when the MAF fails. There are older GM vehicles that were SD with no MAF. Why do you suppose GM went back to using a MAF when they could be saving the cost of that part on hundreds of thousands of vehicles?
04-26-2011, 08:44 PM
#7
tell me how you see it as contradictory and I will tell you if it is....
You see, I have a fair sized cam in my non-factory motor where I also had the MAF mounted near the TB. To me, the second comment backs up the first one.
Point: If I had a smaller cam, I would have a MAF.
You see, I have a fair sized cam in my non-factory motor where I also had the MAF mounted near the TB. To me, the second comment backs up the first one.
Point: If I had a smaller cam, I would have a MAF.
Trending Topics
04-26-2011, 08:46 PM
#8
But would you agree that their operating systems are designed from the ground up to run in SD where GM MAF operating systems are not, but as a back up for when the MAF fails. There are older GM vehicles that were SD with no MAF. Why do you suppose GM went back to using a MAF when they could be saving the cost of that part on hundreds of thousands of vehicles?
04-26-2011, 09:34 PM
#10
TECH Addict
iTrader: (10)
Join Date: Jun 2004
Location: Commerce Twp, MI
Posts: 2,918
Likes: 0
Received 0 Likes
on
0 Posts
IMO - I would assume that a traditional tune that utilizes an accurate VE with a propper MAF cal is optimal for most LSx based cars seeing as though that's how the PCMs were designed to operate. Unless you have some crazy setup that's pushing the limits of the factory PCM (i.e. maxing out the MAF or some huge overlap in a cam that distorts the MAF signal due to reversion), I can't imagine another solution being better. SD isn't a bad thing. But, if you can measure airmass with equal or greater accuracy than calculating it based on a mathematical formula, why not go with the measurement?
You have to remember, when GM set out to design the PCM....they didn't take into consideration that you were going to be digging into it and making changes to their cal. It's designed to work on a stock car that runs in closed loop with a factory engine. Assuming you accurately account for the mechanical modifications you made to the car**, I would think getting the PCM to work in the same manner is going to be best.
**This is a big assumption considering we don't have full access to the PCM....and the tables we do have access to - we're making educated guesses about how they work and the purpose they served in the eyes of the OEM calibration team.
You have to remember, when GM set out to design the PCM....they didn't take into consideration that you were going to be digging into it and making changes to their cal. It's designed to work on a stock car that runs in closed loop with a factory engine. Assuming you accurately account for the mechanical modifications you made to the car**, I would think getting the PCM to work in the same manner is going to be best.
**This is a big assumption considering we don't have full access to the PCM....and the tables we do have access to - we're making educated guesses about how they work and the purpose they served in the eyes of the OEM calibration team.
