To SD tune or not?
To SD tune or not? Getting closer to firing up my 427 NA build. LS7 heads and intake. 238/254 112+4 cam. All other bolt ons. Hearing all different recommendations of SD tune or not. Question to those who have been there. Would a SD tune be the way to go or should I just get a bigger MAF and go from there? This will be a DD with just playing at the track and some road course fun. How much will weather affect an SD tune?
Thanks
Thanks
Getting closer to firing up my 427 NA build. LS7 heads and intake. 238/254 112+4 cam. All other bolt ons. Hearing all different recommendations of SD tune or not. Question to those who have been there. Would a SD tune be the way to go or should I just get a bigger MAF and go from there? This will be a DD with just playing at the track and some road course fun. How much will weather affect an SD tune?Thanks
OLSD FTW.
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Joined: Aug 2005
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From: Sunny London, UK
SD Weather question is invalid vehicle still uses IAT and especially MAP. If weather messes with the tune its not the fact you are fueling using SD its the tune thats wrong.
(eg) Ask Chrysler why they use SD on their hemi's if weather makes it crap out.
(eg) Ask Chrysler why they use SD on their hemi's if weather makes it crap out.
Christian
The problem with OL tuning is the dang bias table that biases between ECT and IAT. You can be perfect on a 40degF day and the car WILL lean out in the summer heat. You would think this to be bassackwards; it is, the error is in the bias.
Marcin has some sweet rocket-scientist formula that you need MATLAB to use that tunes this table; I have had little luck with making manual changes to it and observing result.
If you are hardcore OLSD then answer this, how do you get around this issue as it is not a small one? Most people that run this way get touched up a few times a year.
Marcin has some sweet rocket-scientist formula that you need MATLAB to use that tunes this table; I have had little luck with making manual changes to it and observing result.
If you are hardcore OLSD then answer this, how do you get around this issue as it is not a small one? Most people that run this way get touched up a few times a year.
Running OLSD here, and found that my combo was liking an AFR richer when in the low 50 and leaner when in the high 80 outside, all other factors related to humidity and atmospheric pressure beeing considered...and no elevation involved here.
Does that make sens for you?
Christian
PS: you need a lucky day to find sun in London...
Does that make sens for you?
Christian
PS: you need a lucky day to find sun in London...
It is the opposite of what I have seen on many cars, and opposite of what is popularly posted as results on HPTs forum. It could be from a relocated IAT or your bias table is different than OE. How do you propose to properly tune the bias table?
-edit- wait you said that's what it liked, not where the fueling would move to, my bad.
-edit- wait you said that's what it liked, not where the fueling would move to, my bad.
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OLSD will run better and if done right you will have no worries.I run my personal turbo charged truck like this and haven't touched the tune since it was done in the summer.A/F is the same no matter what the weather is.
Now,the downfall of OLSD. You need to retune it whenever you change something.If you change Cams,intakes,even TB's(sometimes) or even the exhaust configuration. Just make sure the parts are 100% before doing a tune like this.
Now,the downfall of OLSD. You need to retune it whenever you change something.If you change Cams,intakes,even TB's(sometimes) or even the exhaust configuration. Just make sure the parts are 100% before doing a tune like this.
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The problem with OL tuning is the dang bias table that biases between ECT and IAT. You can be perfect on a 40degF day and the car WILL lean out in the summer heat. You would think this to be bassackwards; it is, the error is in the bias.
Marcin has some sweet rocket-scientist formula that you need MATLAB to use that tunes this table; I have had little luck with making manual changes to it and observing result.
If you are hardcore OLSD then answer this, how do you get around this issue as it is not a small one? Most people that run this way get touched up a few times a year.
Marcin has some sweet rocket-scientist formula that you need MATLAB to use that tunes this table; I have had little luck with making manual changes to it and observing result.
If you are hardcore OLSD then answer this, how do you get around this issue as it is not a small one? Most people that run this way get touched up a few times a year.
I am in Fla. Talked with a tuner that said with no weather changes SD tune is fine but with temp. changes I should probably keep the Maf. From what I've learned from this forum SD tune is the way to go. Tuner made it sound like keeping the MAF would compensate for the weather change. My experience is with SBC, BBC with carbs. I know how to adjust those. It's these computer controlled MF'S that I'm trying to learn. 
I want my tune to be a one time deal. Don't plan on any more changes from here. Do I need to consult a different tuner?
He did say that Sd tune would give better overall response but added the weather change deal. Just wanting to know from people with more experience than me. Alot of $$$$$ in this setup and don't want to screw it up. Screwing up seems to come easy to me.
Sorry I didn't really look deep into the responses. Looks like I need to look deep into the tune. Other factors to consider other than the MAF.
Thanks
I want my tune to be a one time deal. Don't plan on any more changes from here. Do I need to consult a different tuner?He did say that Sd tune would give better overall response but added the weather change deal. Just wanting to know from people with more experience than me. Alot of $$$$$ in this setup and don't want to screw it up. Screwing up seems to come easy to me.
Sorry I didn't really look deep into the responses. Looks like I need to look deep into the tune. Other factors to consider other than the MAF.
Thanks
Last edited by bigblockb; Feb 2, 2008 at 11:55 PM. Reason: dumbass not understanding answers
The only way SD tuning will be a one shot deal is if your tuner has God-like abilities. Once an SD tune is done right, weather won't matter. However, the earlier mentioned IAT vs ECT bias tables are a bitch to get right without experimenting in different weather. Fortunately, if your tune has any safety margin it will be OK even if it isn't perfect. Even a halfway decent SD tune will probably be within the same or less variation than a factory tune on an unmodified car.
The way around the bias table problem is by tweaking JUST THAT table in different weather. Everyone seems to tweak their VE or IFR to adjust fueling for different weather. This approach will NEVER get the bias right. It took me most of a year to fine tune my friend's Escalade in OLSD to the point that we have absolutely no worries when his wife takes it out (she drives it like she stole it). Also, if PE, IFR, or VE tables are fudged to make up for some other part of the tune, then the IAT bias will be near impossible to dial in. BTW, the bias tweaks are really touchy in some areas. In others it seems that they make hardly any difference.
So it would probably be better if I got the software and learned what is going on myself to change any tables that affect them? I know given time and experience I could adjust the tune accordingly, but if going with a big MAF (100mm) would help solve the issues I would do that.
I understand what you guys are saying and it seems if I went with the SD tune I would want the ability to adjust the tune to compensate for any variable I might encounter?
Yeah it was 80+F here today. Sucks!!!
I understand what you guys are saying and it seems if I went with the SD tune I would want the ability to adjust the tune to compensate for any variable I might encounter?
Yeah it was 80+F here today. Sucks!!!
A great tune is COMPETELY outside the parameters of what a person can expect a pro to do. It just takes too damn much time to do on a $/HR basis. Many pros can give a very damn decent tune. Unfortunately, unless they work for slave labor rates, you can do better yourself after LOTS of tweaking. I recomend buying tuning software to anyone who is serious about performance. BTW, there are VERY few instances where a bigger MAF helps anything. These are almost solely limited to big CI NA combos. Even in those limited instances, the gains are only a few HP.
"The way around the bias table problem is by tweaking JUST THAT table in different weather. Everyone seems to tweak their VE or IFR to adjust fueling for different weather. This approach will NEVER get the bias right. It took me most of a year to fine tune my friend's Escalade in OLSD to the point that we have absolutely no worries when his wife takes it out (she drives it like she stole it). Also, if PE, IFR, or VE tables are fudged to make up for some other part of the tune, then the IAT bias will be near impossible to dial in. BTW, the bias tweaks are really touchy in some areas. In others it seems that they make hardly any difference."
Unless you have a 98-01 PCM right? Then you do what when the weather changes? Play with IAT only? We can modify the BIAS to be 1.00 (here for what that does: http://www.hptuners.com/forum/showth...highlight=bias) but it does nothing on the older PCM's.
I'm asking so it's clear. Thanks
John
Unless you have a 98-01 PCM right? Then you do what when the weather changes? Play with IAT only? We can modify the BIAS to be 1.00 (here for what that does: http://www.hptuners.com/forum/showth...highlight=bias) but it does nothing on the older PCM's.
I'm asking so it's clear. Thanks
John
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Joined: Aug 2005
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From: Sunny London, UK
Its the old 80/20 rule 
CLSD is a good compromise, trims will take care of 90% of daily use. If you set WOT to something like 12.8:1 then if it wobbles around a bit things should still be good.
I agree its the Bias table that needs sorting. Add heatsoak in to make things more tricky. Bias cant tell if things are heatsoaked or not. Just IAT and ECT
CLSD is a good compromise, trims will take care of 90% of daily use. If you set WOT to something like 12.8:1 then if it wobbles around a bit things should still be good.
I agree its the Bias table that needs sorting. Add heatsoak in to make things more tricky. Bias cant tell if things are heatsoaked or not. Just IAT and ECT
I am a big fan of CLSD, and if the cam is big, you can get it to idle OL using the PE table down low. I don't really see much of a variation in WOT fueling, it was always the cruise area when trying OL running.
how do you account for the varying degrees of heat soak? During the summer in stop and go traffic the IAT really heatsoaks as opposed to highway driving and is very slow to change as the car gets moving and it should be reading lower...