You bring up a good point, but if the IAT sensor is heatsoaked, isn't the entire airbox/filter/whatever also heatsoaked? If so, wouldn't this heat be legitimately transferred to the intake air? I'm just curious how much sensor lag is really involved. I'm not arguing the point, I'm actually curious.

 

Heat soak on the sensor is a real problem.It's mostly fake.If you move the sensor into the intake you'll see.

 

In my case,

my home track is at 5200ft over sea with summer DAs around 8k.
I usually go to another track that is at 500ft over sea twice a year
and planing to go to TX (edimburg) this year.

with a SD tune i would need to re-tune at each location?

 

Reread the thread dude your question is already answered.
NO.

 

thnk you grumpy

you see weather changes.. but at same altitude..

hot and cold is one thing...

thin air and lots of air is other..

but thanks.

 

This does not make me look forward to my SD tune anymore. I don't know my *** from a hole in the ground when it comes to tuning so I'll be relying on a dyno tuner to do so. Where I live weather changes very drastically and I've heard about this downfall about SD. The power I will be tunning leaves me with no choice though. The Maf is garbage.

 

CLSD is cake though, and definitely what you need for that turbo.

 

Don't sweat it. A lot of the pros/cons discussions you see in this forum really boil down to people chasing that last 1 or 2% error that most would never worry about. It really isn't as bad as a lot of people (including myself) make it sound.

 

I totally agree about needing to SD tune, I have no choice. With the boost close to max I am sure I can produce 1000fwhp. Its not what I am going for and will most likely run 650rwhp or so 99% of the time being its a street car.

I wish I could tell you I know the differnece b/w CLSD and OLSD, LOL I am sure and hope my tuner does or I'll be travellig somewhere that does. My buddy has done allot of tuning, both N/A and FI so he is going to get me running and close to complete. Just want to take it to the dyno to get tweaked and see what it lays down of course too!

This thread just has me worried b/c I was hoping for a one shot deal, if not atleast once annually at the minimum. I plan to leave everything as is since I am slowing piecing everything together to do it once and do it right the first time. If SD is going to be this much of a pain in the *** to tweak for weather it looks like I am going to have to learn myself I used to tune my last turbo car, I modified the **** out of my 95 Eclipse GSX but I know its going to be allot deeper than

BTW thanks Frost you were inspiration for me to do this build as I have the same kit as you but with the upgraded 80 compressor wheel. I read your build thread among many others, and just watched your video again as a matter of fact, LOL I remember when it started thinking, how does someone get the money for all of that. Well now I am doing the same thing, HAHAHAHAHA

 

CLSD and OLSD tunes are not that hard to do. I just spent $1000 on HPTuners and several extra credits. My new turbo car will be a 3BAR OS. It will be OLSD. I have tuned every LS1 car I have owned via a HPT SD tune of some sort. Never once did the MAF get put back on the car. I rarley changed a thing due to weather. Gotta love KY where you get up in the moring and its 40 degrees and by mid afternoon you are frig'in melting because its so hot and humid.

 

Well in Canada its the same thing but for only 4 months or less. About 5-6 months max of capable driving weather. I am going 2bar for now anyways. I'll have to pm my engine builder/tuner to see if its OL or CL. Any reccommendations on what to go with? The way you guys are talking the OL is better but can have more issues correct? As long as the tune is safe though either way you should be ok for weather variances correct? Its not like I have a huge *** cam either to throw another wrench in the mix, LOL

 

Well I missed this post, in that case we are Golden! As long as my dyno tuner is good though. He should be from the projects he has done thus far.

 

I love SD so SD all the way! My car was tuned in hawaii and now i live in missouri and have driven all over the midwest and south east US and AF stays good and car runs great! My car has been driven in -10 deg wind chill to

 

Nice, well I hope it works out well for you. I have enjoyed mine, even with the headaches that it brings.

 

Ya thats why I have learned from your thread. Solid mounts, wrap steering column, power steering, etc, etc With turbo's and great power come comprimises but I think once the bugs are worked out it should be fine. Plus the guy helping me install the kit has installed it and worked the bugs out himself too. He's the guy tuning it, btw, he said he likes to use CLSD but I still have to read into it yet, LOL

 

I've improved my heatsoak issue via fitment of a 160F thermosat. I live in some pretty extreme heat in northern Australia and its not a problem. Sure it soaks a bit while stationary, but once underway temps fall pretty quickly. Give it WOT and its back down in a few seconds. Besides its only going to command rich anyway so no safety issues are present. My main point though is that with EFI LIVE's VE/IAT Factor feature, going SD offers sound fueling calculations in all conditions. Altitude has never been an issue as the PCM knows BARO and will account for it accordingly. Temperature is the only issue and as I've highlighted its been covered in custom O/S 3 and above. VCM doesn't offer this feature as far as i know and frankly I too would be concerned if I didn't have this factor in my tune. But living in an area where temperature ranges from 32F-113F I'm sure you can understand my concern.

 

There is no WOT in stop and go traffic, but there is lots of time for the car to sit still and soak. I don't know what traffic is like in Aus. Temp here ranges from about 18/20F to 103F so about the same spread.

I'm not trying to be argumentative, all I really want is for someone in this thread to COME OUT AND SAY, there is no 100% spot-on SD tune; the complexity of buttloads of variables and their physical relationships makes any working algorithm, that we can understand, mostly over simplified.

 

"There is no 100% spot on SD tune" . J/K.

 

They also have tables that are very interesting, so much that a real CAI would require retune to be done right. At least the hemi is a somewhat real Ve table, not the old stuff that was done on the jtec based stuff.

Ryan

 

There is a big temperature "input" to the speed density air
mass value. There appears to be a lot of fancy GM fiddling
done to the IAT data. Question is, where in the intake tract
does sensed IAT equal the "right answer". Given all the stuff
you can't see and nobody knows, the spurious thermal input
from "heat soak" and so on.

For a plain calculation you need MAP and MAT (manifold
absolute temperature) for the density, and RPM for the
speed. What you have, is IAT on the wrong side of the
throttle blade. So MAP sees the expansion, but the IAT
does not, it must therefore be faked in the code. I don't
know why GM didn't integrate the IAT with the MAP sensor
(so MAT and MAP, same air sample) but they didn't and
we have to live with the spaghetti.

There are IAT and ECT adders for open loop mixture, at
least on some models. If you used them you could help
the "weather problem". But you need a lot of data over
a large range of variation and the weather may not
cooperate in the timeframe you'd like.

Whether or not you intend to run "speed density only"
the SD tune is the heart of it all, the MAF is only an
"overlay" that is used under specific conditions. For
transient throttle, low RPM driving (like, oh, the street?)
speed density still weighs heaviest. So you ought to
get it tight regardless.

Realize that the usual tune-to-AFR-error method has
as much sensitivity to fuel delivery -assumptions- as
it does to airflow calibration. You fix airflow blindly, you
can get to a "clean" SD tune that goes to hell as soon
as you hook up the MAF, then you have to lie about
the MAF characteristic to get agreement, and then the
torque model is bent so your idle air is nuts and your
transmission line pressure, on and on. Since the fuel is all
straight up guessing (PCM has no input or feedback on
true fuel pressure or delivered fuel) try to guess well.

If you end up with VE table values way over 100% or
way under 90% at full MAP, 4-5000RPM, bet it's not an
air model problem. At least, not entirely.