I am really confused. I put pacesetter LT's, 3" true duals on my car with flowmaster super 40's. Now i need to tune it but i can't figure out which way to go. I live in wyoming so no one has a dyno with ls1 edit around here. So my options are:

1) Mail order tune- (i have both good and bad)

2) An agressive chip (jet pcm stage 2)- (but are they as good as a mail order tune? And i will still have my SES light on)

3) Get a loan from the bank and buy LS1 Edit and figure out how to tune- (NOT LIKLEY)
I know either way i will need to buy a cooler t-stat and a CAI . This causes more ?'s

1)What temp t-stat (160 or 180)
2) i have read about people descreening their maf. Does this help?

Thanks for all of the help.

P.S. If you have any other ideas that I should do that are not too expensiv, send them my way.


00 Z-28 Pacesetter LT's, 3" true duals w/ Flowmaster Super 40's

 

Why do you feel you "need" to tune it? All your mods did to the tuning was lean out the A/F ratio due to the more efficient exhaust flow. The FIPK or whatever you choose for CAI will also lean you out some. This is all good since the factory programming is way too rich. In other words, your stock tuning is now closer to ideal anyway due to your mods.

My opinion, since $$'s an issue and time to devote as well, don't worry about tuning it and leave it alone. You're looking at a pretty small gain at this stage anyway.

BTW most opt for the 160 stat and also bypass your tb coolant to keep the tb cooler. Again, you dont "need" a CAI mod or the stat ...neither one.

 

Actually, its not likely he leaned anything out at all. His exhaust and (future) intake improvements increased the breathing capabilities of the engine. The MAF sees the increased air flow, and the PCM adds the required fuel to match, using the 14.7:1 hard coded for closed loop, and using the PE mode target A/F ratio calculations for WOT.

That's the advantage of mass air control... the MAF sensor picks up the results of your improvements, and programming is not required (within reason).
Why is your SES light on? The only reason correctly installed headers would cause the SES light to be on would be if you deleted the cats, and did nothing about the after-cat O2 sensors. That is easy to correct with "sims".

Or is the SES light on for some other reason?

There's some good info on mods for the LS1 engines in this book:

Chevy LS1/LS6 Performance, Christopher Endres, HP Books
http://www.amazon.com/gp/product/155...46364?n=283155

 

True, at cruise the closed loop helps to keep you in the stoich area. At WOT you are hitting targeted values like you say though, which the MAF cannot completely compensate for unless I've misunderstood a lot of what I've learned (like you say, "within reason")....otherwise then why do we even bother adding fuel in the PE vs RPM table when we add lots of air from say ...heads/cam or a blower? Anyway, basically I was getting at the same point you are ....that the tuning isn't "necessary" and if anything it's more ideal and/or leaner now than it was before....that's all.

I also wonder if he has rear O2 sim's, since he'd get the light if the cats are gone and no sim's on OBDII....esp w/true dual setup it makes me wonder ...

 

I did delete my cats and i did not buy o2 sims because i thought that i was going to get a tune/ which would take care of them. I guess i thought i needed a tune because I have read in many places that after an agressive exhaust change you need a tune to get the most out of your headers. There was one person that put duals on his car and dynoed less power. After he got a tune he had around 30 more hp.
I have read that my car has a touque management thing on it. Does deleting this help considerably seems how i have an auto. Also how about descreening the MAF? Thanks for all the help!

 

To make the most of it it will help some to have some fuel taken out. I'm not sure why someone would lose power from headers unless they were causing false knock retard. Sometimes there are clearance issues and upon torquing of the engine the header(s) bang into something and the knock sensor reacts to it. They may have found a lot of false knock and disabled knock retard in his tune ...regardless I can't think of any other logical reason he would have lost power from the headers. Here I'm assuming headers went along with those duals though, is that not the case?

I've mislead you in a way. LS1's are tuned a bit more conservatively than LT1's from the factory, so there is more to pick up in tuning an LS1 than an LT1. I'm just saying you shouldn't "need it" and should be seeing a power gain regardless, unless there's a problem like false knock retard being created by the mods. I'd think you'd pick up no more than ~20 HP from a tune at this stage but every combo reacts differently. It also depends on how "on the edge" you want your air/fuel ratio to be ...this is about your comfort level concerning what's safe. N/A ride like yours the A/F would probably be safe at 13:1 but I don't have experience tuning N/A cars. You won't know this anyway unless you tune on a dyno w/wideband, which I think is excessive for your application ...but to each their own. I would guess you could pick up 10-15 hp from a tune, possibly a bit more. Descreening the MAF is a nice free mod as long as it doesn't affect your idle and driveability (usually doesn't) ...go for it. Isn't your ASR (torque management or "acceleration slippage regulation" ..I think) able to be turned on and off via a switch on the dash? If so it should not be a performance issue. If you can't turn it off then I'd say it's definitely hurting you when you encounter wheelspin on the street.

 

I do have an ASR button on my dash but i didn't know that's what people called the "tougue management". I thought it was something that kept your motor from putting all of the tourque to the rw as a saftey device. But now I know.
I am now kind of dissapionted that I will not be getting a boost in performance from a tune. I was looking forward too that. Looks like I will just be getting some o2 sims and a 160 deg t-stat. Hopefully the 02's take care of my ses light.
One of you were saying that after my exhaust my computer is adding more fuel. Would this explain my 2 mpg drop in fuel mileage, or is there something wrong. If there is sometihing wrong could it be fixed with the stage 2 JET PCM chip i asked about earlier, our would that just be a wase of money.
if everything is fine with the extra fuel my engine is getting, I shouldn't have to do any tuning for say..... a 100-125 shot of dry nitrous. Because my understanding of using nos is that one needs extra fuel for the nos to react with.
Thanks Alot!!
bty the nos should be coming after i get the whole computer thing figuerd out.

 

I know you don't want to hear this but you're obviously new, I feel you should wait a bit and research things in here before you proceed with something like nitrous. There are "wet kits" and there are "dry kits" ...the wet kits have provisions for extra fuel and inject the extra fuel and nitrous downstream of the mass air flow. Dry kits are simpler and inject the nitrous alone upstream of the MAF, the computer adds the appropriate does of fuel. N2O isn't my thing so I can't give much advice on that but the forum we have in here for it could be very helpful for you. It seems like wet kits are more popular and probably safer. When properly setup the nitrous will not even activate unless there is "x" amount of fuel pressure, this is a must for a safety feature against detonation. People in here are very successful with 75-125 shots on stock motors, I wouldn't push it any further without a properly built bottom end unless you're ready to rebuild anyway.

Are you sure the 2 MPG drop in mileage isn't related to a little more of the right foot wanting to hear that exhaust note? Also, are you sure it's not weather and driving conditions related as well? ....2 mpg is a pretty small variance and can happen pretty routinely unless you're talking about consistent highway. I wouldn't think the exhaust would cause a drop like that. When we say the computer is adding fuel to compensate for extra air that just means it's trying to achieve the best possible air/fuel ratio (stoichometric 14.7:1) for good mileage and it will still target a very rich ratio (like 10.8:1 or so) for power enrichment (say ~1/2 throttle or more), as these cars are setup to run pig-rich under higher loads to protect the warranty from idiots who put 87 octane in a 10.x:1 C.R. engine. In theory though (believe me a lot of how these computers work is theory and people don't agree on it) when driving hard, in one way you should be using more fuel and in another way you should be using less. The more fuel scenario is that the MAF measures x-amount of air and supplies x-amount of gas, so if you can flow more air at WOT you'll use more gas right? Well, not exactly, the less fuel scenario is that once you hit WOT there is no longer any learning, the computer doesn't respond to the voltage read by the O2 sensors. It continues to read the MAF but at the same time targets pre-set fuel values in the Volumetric Efficiency table (in some cases, some not) and the PE vs RPM table (always, I think). So it can correct fuel as far as reading the MAF goes, but can't alter what it does in the other tables. Therefore let's say you've dyno'd once with stock exhaust and once with aftermarket that flows better, the dyno run with the aftermarket exhaust will show a leaner reading since more air was able to get through and the computer had only limited ability to compensate. This was why I originally said that your tuning is now closer to ideal anyway. Where you were once probably hitting say 10.8:1 A/F now you may be hitting more like 11.0:1 which is still too rich to be ideal but not as rich as before. Now during cruise, the computer is in closed loop and one way or the other attempting to correct the fuel to stoich (14.7:1) so cruise and low throttle mileage should be largely unaffected. But, then you have to consider other variables like possible low rpm torque loss from the reduced backpressure, this could cost some mpg at low load cruising due to needing more throttle % to attain cruise, but not 2 MPG I wouldn't think.

Lots of variables man, sorry to be so wordy. In a nutshell I don't think you should lose that much mpg due to the exhaust, perhaps the SES light from the missing O2 sims is contributing some ...I don't know if that would goof up closed loop some, maybe.

BTW stay away from the JET junk IMO. I don't think you can get a "chip" anyway, your car is OBDII if I'm not mistaken which means either Hypertech or similar programmer, Tunercat, or LS1-Edit. I would recommend keeping stock tuning until you feel comfortable with the idea of tuning it yourself with LS1 Edit or Tunercat, especially if you already have laptop or can reach a long cable from your PC to your car. Logging software is free. Good molded cable will cost you around $100. I think my total for LT1 Edit, Datamaster, and the cable was around $300. I was paranoid so I bought a Scanmaster too which is permanently mounted in my middle A/C vent (good idea on a forced induction application since it displays knock retard and O2 voltage as default). Bottom line, if your main goal is nitrous and 75-125 shot is good enough for you, stock tuning should be fine.

 

My plans for nitrous was the NOS kit from Summit made specifically for my car, which is safe for stock engines they say. As for the computer tuning, i thought ls1edit was 1000's of dollars. If it's only $300 for the entire setup, then i would be better off spending my money on that rather than a $250 chip which i have never heard of people using. Maybe ls1 edit is a little more vs lt1edit, but i am willing to spend the extra for unlimited tuning capabilities. How much is the scanmaster thing you were mentioning, and do i really need it seems how i am still N/A.

The whole decrease in MPG is still there no matter how I drive. Cruising only down the interstate at 80 mph (2300-2400 rpm) on my tank of gas i am still getting 19-20, while i was getting 21-22 when i first got it a year and 10,000 miles ago. may it is just my tranny getting worn. i have noticed it running 100-200 more rpm for the first 3-4 miles when i first get on the interstate, then it will drop down. oh well, i'll figure it out eventually.

Thanks a bunch for all the explaining you have done.

 

LS1_Edit is $450 with the cable.

 

Another 100 - 200 rpm on the interstate for the first few miles? I'm guessing you have an automatic, good news on that is there is more benefit to be had from tuning since you can firm up tranny shifts, revise shift points, etc. To me that sounds like you've encountered cooler weather and your torque convertor is just waiting longer to go into lockup. The cooler weather will make for poorer mileage anyway, but especially when your converter isn't locking due to it. But you said your "tranny might be getting worn" so perhaps you're not even entering OD for a good bit of your commute (or your converter isn't locking at all).

Sorry, I guess LS1 Edit's a little pricier than I thought ...it's still worth it IMO if you plan on modding a decent bit. Especially if you do heads/cam later on. Most don't run a Scanmaster permanently mounted like I do. I'm not sure they even make it anymore, you might want to do a search if interested. I like to have my eyes on knock retard and fuel pressure at all times (so I also run a fuel pressure gauge full time) because those two things are critical to monitor with supercharging.

 

Scanmaster is still being sold, in LT1 and LS1 versions. $250.

For scan software, he needs something other than DataMaster (OBD-I only). I have AutoTap for my OBD-II vehicles, but I hear there are better things out there for the LS1.

But... AutoTap EFILive will allow you to both scan PCM parameters, and to change the settings in the PCM. Worth learning more about.