mafs to speed density

[themb2g]

I'm looking to cut out the MAFS and go with a speed density set up. Has anyone done this? What changes fo you need to make other than reprogramming the computer?

[classic70]

As far as I know just reprogram the pcm.

[Custom 68]

it depends, mine is turbo so I opted to get rid of my MAF. In general it would have worked even in my setup but I had a bend in my piping right before the sensor and it would not read correctly. I also had the chance to go to a 2 bar system, now with FI I can read and control the computer when in boost.
If you are not FI then the change over is easy but I will ask why? I ran mine with mine originally for years with it and it was no problems. You can just disable it in the tune then your are running SD only, you will need to add a air intake temp sensor and wire it into your harness to the MAF.
Anyway unless you are having problems or just dont like the looks of the MAF and cant get it to fit right I would leave it.

[Wasted Income]

I switch over to speed density in all my LS swaps, not just my turbocharged ones. Personal preference I guess, but they all run great. Plus the clean look is nice. Calibrating the MAF if you change any of your intake plumbing is kind of a PITA also.

Like Custom 68 said, you'll need to wire in an IAT sensor, and make a few changes in the tune. Best to run a 2/3 bar OS (in EFI Live), that way when the MAF is failed (to force speed density) you get both your low and high spark maps.

[themb2g]

Originally Posted by Custom 68

it depends, mine is turbo so I opted to get rid of my MAF. In general it would have worked even in my setup but I had a bend in my piping right before the sensor and it would not read correctly. I also had the chance to go to a 2 bar system, now with FI I can read and control the computer when in boost.
If you are not FI then the change over is easy but I will ask why? I ran mine with mine originally for years with it and it was no problems. You can just disable it in the tune then your are running SD only, you will need to add a air intake temp sensor and wire it into your harness to the MAF.
Anyway unless you are having problems or just dont like the looks of the MAF and cant get it to fit right I would leave it.

Where does the air intake sensor go and do you have a picture of one set up?

[Custom 68]

I will need to snap a picture but I just drilled a hole in my intake tube and installed it there.
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[themb2g]

Thanks, that would be great.

[prostreet1967]

Originally Posted by themb2g

Where does the air intake sensor go and do you have a picture of one set up?

i have seen where someone removed the purge valve on truck intake and tapped hole and threaded IAT in there.

[BR3W CITY]

Usually it would go in the intake track; I imagine that doing it in the manifold might be less accurate, from both air turbulence and an increase in temperature from using in-manifold air.

[1969x11]

Originally Posted by prostreet1967

i have seen where someone removed the purge valve on truck intake and tapped hole and threaded IAT in there.

^^^^This...works like a champ.

[themb2g]

Originally Posted by BR3W CITY

Usually it would go in the intake track; I imagine that doing it in the manifold might be less accurate, from both air turbulence and an increase in temperature from using in-manifold air.

I was talking to the Spectre Tech the other day and he mentioned to put it 8" to 10" from the TB. I would love to run it in the Purge Solenoid spot though. Would the inaccurate readings lead to poor efficiency/less power? What is the negative part of the inaccurate readings?

[Super73]

I do it with most my customers cars and my personal ones as well.

I have a 1 bar SD tune from hp tuners that allows you to use both high and low spark tables. If you force a fail with out the custom OS you are limited to the low spark table.

But simply put the process looks like this for drive by cable (drive by wire is much different).

Disconnect MAF
If vette or truck harness, rewire an AIT (99-02 fbody harness had then seperate)

In the tune:
Copy high spark table to low table
Change Power enrichment EQ to 1.14 in all cells (this will command 12.9 @ WOT)
Change enrichment rate to the max (4 in most cases)
Disable Cat Over Temp if you don't have cats it can screw with fueling at WOT
Disable Decel Fuel Cut Off
Disable Ltrims and bump their on threshold to 280*
Under engine diagnostics, change all MAF codes to no SES light and Fail on 2nd event

Now you can clean up the VE table to get the proper AFR.
Posted via Mobile Device

[themb2g]

Originally Posted by Super73

I do it with most my customers cars and my personal ones as well.

I have a 1 bar SD tune from hp tuners that allows you to use both high and low spark tables. If you force a fail with out the custom OS you are limited to the low spark table.

But simply put the process looks like this for drive by cable (drive by wire is much different).

Disconnect MAF
If vette or truck harness, rewire an AIT (99-02 fbody harness had then seperate)

In the tune:
Copy high spark table to low table
Change Power enrichment EQ to 1.14 in all cells (this will command 12.9 @ WOT)
Change enrichment rate to the max (4 in most cases)
Disable Cat Over Temp if you don't have cats it can screw with fueling at WOT
Disable Decel Fuel Cut Off
Disable Ltrims and bump their on threshold to 280*
Under engine diagnostics, change all MAF codes to no SES light and Fail on 2nd event

Now you can clean up the VE table to get the proper AFR.
Posted via Mobile Device

Thank you! Do you have a picture of what the sensor looks like? I have two separate harness's, one from an 02.

[Super73]

02 fbody?
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[Wasted Income]

Originally Posted by BR3W CITY

Usually it would go in the intake track; I imagine that doing it in the manifold might be less accurate, from both air turbulence and an increase in temperature from using in-manifold air.

Not true. I've found that I get much better / stable IAT readings with the sensor in the intake (at the EGR port on a truck intake for instance).

The plastic will not heat soak like an aluminum tube will, and you are getting the ACTUAL temp of the air in the intake, which is what matters...not what the air temp is a foot or more away from the TB.

I've done it that way on several setups, works great, and cleans up the wiring a bit as well.

[themb2g]

Super 73 I have two harnesses. One from an 02 Avalanche and the other out of a 07 express 3500.

[Wasted Income]

Originally Posted by themb2g

Super 73 I have two harnesses. One from an 02 Avalanche and the other out of a 07 express 3500.

Those are two totally different harnesses, with two totally different purposes.

The 02 harness is a DBC harness, and has a provision for an IAC valve.

The 07 harness is a DBW harness and does not have the IAC plug, since they use the TB for IAC.

They also require different PCMs.

[BR3W CITY]

Originally Posted by Wasted Income

Not true. I've found that I get much better / stable IAT readings with the sensor in the intake (at the EGR port on a truck intake for instance).

The plastic will not heat soak like an aluminum tube will, and you are getting the ACTUAL temp of the air in the intake, which is what matters...not what the air temp is a foot or more away from the TB.

I've done it that way on several setups, works great, and cleans up the wiring a bit as well.

How much do you think the tube actually heat soaks? I see iat (off my scangauge) at anywhere from 95 to 117 the past couple days, with it in the high 50's low 60's outside.

[Wasted Income]

With my turbo setups, I've seen them heatsoak a lot...that will happen with 200+ degree air coming out of the turbo.

N/A still heatsoaks, but not as much.

[jorgensensc]

So if there are advantages to running speed density, what are the disadvantages? Obviously GM decided to go with MAF over Speed density for some reason.
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[Wasted Income]

The biggest disadvantage in my opinion is that once the tune is dialed in, if you change anything (air filter type or routing, exhaust, cam, heads, etc) it will need a retune of the VE table.

The MAF lets you get away with more changes by compensating (within reason) for these changes.

Here's some reading for you.

http://www.pcmforless.com/index.php?...ning&Itemid=56

[faribran]

so, what are most using? MAF or Speed Dens?

[Custom 68]

if I were to guess I would say MAFS since it is factory on most of these engines. If they are turbo or other FI I would say SD.
Like said above getting rid of the MAF does look nicer and might be easier for fitment.

[BR3W CITY]

I also weigh in, that MAF is nice when you do long road trips through multiple types of drastically different temp and density air, technically giving you the most "accurate" tables for the input its given.

From what I glean from speaking with members here and on ls1tech and yellow bullet, this is nice for fuel economy and cold start ups etc, but has little noticeable difference under most people's use. SD will be able to "make" more power.


Wasted- you had me staring at the gauges as to what my intake temps were all yesterday.

[Jon01]

You guys are getting tied up in semantics.
As long as the tune has the appropriate adjustments to IAT timing tables you'll be fine.

I've only done 1 full on SD tune, 4-5 years ago. It was a 427" LSx, solid roller, ported AFR's, etc...basically a max effort N/A motor.
Otherwise everything gets a MAF. It's failed to tune the VE table but once that's completed it's re-enabled and tuned.