Another MAF vs Speed Density question - changing altitudes
Thread Starter
Teching In
Joined: Jan 2012
Posts: 8
Likes: 3
Another MAF vs Speed Density question - changing altitudes Hey guys, I'm swapping a LQ9 with rectangle port top end into my 1996 Bronco. I'm getting mixed input on if I should run MAF or speed density. The truck will spend a lot of time split between being at sea level and then going through the mountains. Its an adventure vehicle.
How does speed density react to altitude changes compared to a MAF? What should I run known it will semifrequently go up the mountains in the PNW and surraounding national parks?
How does speed density react to altitude changes compared to a MAF? What should I run known it will semifrequently go up the mountains in the PNW and surraounding national parks?
TECH Regular
Joined: Dec 2020
Posts: 423
Likes: 132
From: Ohio
Ask your tuner
Speed density generally does not do well with altitude change if you do not have an additional map sensor going to atmosphere to reference air density
At least this is what my tuner told me
I will not have altitude changes but may still run an additional map this way to not make the correction do the work if I wind up going on a long road trip
Speed density generally does not do well with altitude change if you do not have an additional map sensor going to atmosphere to reference air density
At least this is what my tuner told me
I will not have altitude changes but may still run an additional map this way to not make the correction do the work if I wind up going on a long road trip
TECH Fanatic
Joined: Jul 2022
Posts: 1,036
Likes: 390
From: Alaska
02 Tahoe, 2 Bar SD tune: No MAF.
Magnuson pushes 11 pounds manifold pressure.
I tuned it in Alaska, at 50 degrees Fahreneit ( summer) at SEA Level.
Drove it through Canada, Montana, Wyoming, Colorado to Texas, Ran great at 105 degrees in Texas.
SanteFe New Mexico, 7000 feet and 80 degrees F: No problem, full boost, smooth idle.
Ran up to south rim of Grand Canyon ( 9200 feet) ran great the whole way, no problems.
We put 11,000 miles on in 3 weeks, 3 canadian provinces and 11 states without issue. Rotated tires once, changed oil once. Other than that, never turned a wrench.
Back in Alaska now. It's been 8 years, that little 4.8 Liter has ZERO oil consumption, and has had NO issues..
.
Short story: Speed Density will run anywhere, at any temperature or elevation, with out issue.
It's ALL about SPEED x Density, with a little help from your IAT Altitude affects density, which is calculated based on MAP and temperature. No need to separately take baro readings or any other such nonsense. Tuners that tell you it won't work are either stupid or lazy (or both).
edit-- Millions of factory vehicles were SD only and the manufacturers used the same tune selling them in Denver as the ones sold in Daytona.
edit-- Millions of factory vehicles were SD only and the manufacturers used the same tune selling them in Denver as the ones sold in Daytona.
Last edited by gametech; Jun 19, 2024 at 01:21 AM.
Trending Topics
TECH Fanatic
Joined: Jan 2018
Posts: 1,059
Likes: 198
If you go to a higher elevation, yes the air pressure goes down.... But the entire point of speed-density is to determine how much air gets into the combustion chamber with each intake stroke, based on the density of the air in the manifold and the speed the engine is running at. So it's constantly measuring the air pressure in the manifold, and it doesn't know or care whether that pressure is low because the throttle isn't all the way open, or if it's low because the car is at high altitude.
In theory the atmospheric pressure makes a difference in exhaust backpressure, which in turn could affect cylinder filling. If your cam doesn't have overlap (which I'm guessing is the case for a Bronco) then I'd be shocked if that made a measurable difference in VE. I do kinda wonder how much if matters (or if it matters at all) for cams with a lot of overlap though.
In theory the atmospheric pressure makes a difference in exhaust backpressure, which in turn could affect cylinder filling. If your cam doesn't have overlap (which I'm guessing is the case for a Bronco) then I'd be shocked if that made a measurable difference in VE. I do kinda wonder how much if matters (or if it matters at all) for cams with a lot of overlap though.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
