I've been reading a lot about scaling the ve down 60-80-90 for idle on cam cars to help with cold and hot starts but I also read the write up that Team ZR1 did about how the ve table should not be touched and that people who scale the ve are tuning wrong. He even put up actual dyno pulls with and without changing the ve. The car actually lost horsepower scaling the ve. I tried this last night leaving my ve stock and the only problem I had was on start up. It takes a couple of seconds to find the idle. How do I cure this? My car is 2000 LS1 Camaro, cam is a 226/230 .575/595 112+4, Raf is 9.0, IAC park position is 21, Iac counts are low twenties, idle is 850. Any suggestions, or do I need to scale the ve fix this. I believe TeamZR1 said that on some cars you might have to scale it a little bit but i'm not sure. Any advise would be greatly appreciated, thanks.

 

Stop reading TeamZR1 and read a bit wider. Try some different things.

You are probably finding its rough until it goes into closed loop.
IMO you should retune (not scale) the VE to match the engines new VE. Thats exactly what the VE table is for!

If your engine changes why wouldnt you change it?

 

The engine is only rough at start up for a few seconds till it finds its idle, It doesn't matter if it's open or closed loop. Messing with the ve at idle tends to lean it out too much causing positive ltrims. Can I just lean the ve out before my idle map?, like 15-55, will that help it start better? I'm new to all this and i'm just trying to understand, sorry if these questions are stupid.

 

Plenty -O- info in the very first sticky in this forum. I used it to get my car to idle stable at 650rpm. Starts up cold just like stock. Team Who?

 

Yeah I looked at all of the stickies that pertain to ve, its just what Teamr1 claims that has me thinking twice. He's the only one i've seen with proof that backs his claim. Doing the nogo method on ve does help my car at start up but it gives me high ltrims, i'm not saying it doesn't help but is that the right way to go. He says that he has gotten a ton of people coming to him to fix their tune and talks about how the main thing wrong with the car is that someone hacked the ve table. Once he put it back to stock and made some other tweaks it was fine. By the way the car that he tested with the stock ve and the modified ve has been stroked, cammed, heads, headers,ect.

 

The individual mentioned has also claimed wideband O2 sensors aren't needed to accurately tune... He's also one of the very few individuals that would rather tune with LS1 Edit or TunerCat and use excel spreadsheets to tune rather than having an integrated scanner (most of his posts generally seem to be an attempt to bash people on other boards, and to state that EFI Live and HP Tuners are both junk)

There's a reason this guy's banned on many boards (this one included) (that's not to say that all the info he's posted is useless.... it's just more of his posts are comical than useful)


One thing to keep in mind witha big cam and the fuel trims... w/a big cam there's alot of overlap... so for the most part wideband and even narrowband readings can't be trusted... even w/the ideal fuel mixture, because there's a short period of time where both the valves are open, there will be some raw fuel pushed out into the exhaust stream... plus between 400 and 1200 RPM , power isn't necessarily the important thing... you tune the car to idle... when racing that's not even part of your powerband (dunno if I've ever even seen a dyno for a car starting that low of RPM... other than hypercrap and such which use power gains at low RPMs as a marketing gimick)

Regardless of the method used, the end result is only as good as the tuner

 

There are many band aid approches out there. Just a few short years ago before people tuned with a WB 02 like a LM-1 or the like and a good scanner program like HP Tuners, people rescaled the VE, used IFR to "adjust" Ltrims and guessed in other areas after seeing patterns, but it got the job done.

If you want your car tuned correctly, you need to have your VE table tuned via a WB 02 within 2% and then tune the MAF table within 2%

 

you sure? you might wanna ask around for other peoples' proofs.

there's a wonderful thread on monodax's forum where he makes 'physics based' claims that contradict each other, and then he proceeds to bash people and companies by name only because they don't agree with what he thinks is physics. i dunno who pissed in his cheerios, but as a businessman i thought you supposed to be nice to people.

i know i make a lot of fairly out there statements (just like zr1 does), but because of it, i try to back it up with hard science, and provide full derivation for everything i do. partially to show i have nothing to hide, partially because i'd love to have someone double check my work. so far i haven't had any big 'oops i was wrong' moments yet. until he can explain to me how car mods do not affect VE, or how MAF should not be altered when you change the air tract, i'm sticking to my version of things.

what really pisses me off is his 'we know already everything there is, thus everything new must be wrong' approach. it's thinking like this that threw Galileo in jail and tried to force Copernicus to recant his ideas.
<rant off>

 

This was also posted in that thread on Monodax. I'd like to think that Ed Wright and GM calibrators do know what they are talking about. I tried to get some comments on this a couple of weeks ago.

 

Thanks for all of your responses, I figured guys like horist, redhardsupra, wait4me and nogo are more on the money than the one and only guy that says something totally different. I didn't realize what kind of rep he had on these sites. Don't worry, I trust you guys more then tzr1, I was just curious why he said something different and basically trying to say that what you guys believe works, is wrong. For me being new to this, you guys really helped me out with all of the good info. you pass along. I greatly appreciate it. Anyways, thanks for the advice and i'll definately be listening to you guys from now on. Mike

 

I'd like to ask him, "So if the Car doesn't have CATs, is the WB accurate then?" lol

 

Does anyone want to comment on what 2xLS1 said?

 

I'm not saying I agree or disagree with what Ed is saying, but he is a premier tuner and does have inside connections with GM. I think it merits some discussion though.

 

As a 36 year old "kid" who tunes with real modern day Automotive Test and Monitoring Diagnostic equipment (EFI Live, Moates Road Runner, LC-1 wideband, and Autometer Fuel pressure sensor) I find it entertaining that a "GM Calibrator" who is still using the PCM's fuel trims as a tuning tool "Grins" at my and others efforts clearly and demonstrably posted all over this board.

 

sure mike, this is pretty much a different take on 'why do we tune VE' question which i answered Why tune VE?

but to add to this, i've also completely derived the Speed Density model, which greatly enhanced my understanding on why we _need_ to change VE.

but beyond all the technobabble, there's also just simple common sense: why are we exchanging parts for bigger, smoother, mandrel bent, etc? where does power come from? in NA motor, you have fixed displacement, RPMs are limited by reliability, and pressure goes up only up to the atmospheric. the only other ways of improving airflow is to either lower temperatures (aka increase density which squeezes more mass into the same volume) or to improve VE. the reason why leaving VE stock is ridiculous to me, is the nature of aftermarket parts and how they affect the system. LT's greatly improve midrange. most big cams trade off low end for high end (efficiency wise). heads usually improve through the full range, but more toward the high end. there is no easy way to describe all the different VE changes across various RPM and MAP conditions, other than the VE table. (this gets much complicated these days with variable lift/duration cams and other high tech gizmos, but that's a totally different discussion)

PE/IFR tweaking, ever so popular with the oldschool guys, describes only a subset of VE. PE is RPM based and IFR is MAP/ManVac based, so if you put them together you end up with a similar functionality to VE. their downfall however is that they only describe proper fueling for _one_ row/column of VE, while VE proper is an actual table, with all values filled out. therefore, unless your IFR table has one value across the whole table (and it doesn't unless you have a really kickass fuel system), and your airflow is directly proportional to RPM only, without any swings in efficiency, IFR/PE tweaking is a 'tune' for one and only one situation--until recently such 'tuners' been able to get away with it, as the domestic crowd is interested in WOT only, and lousy drivability is called 'lope' and 'drive-in sound' and is somehow considered cool.
so yes, IFR/PE tweaks have their place--if i had to tune a track only drag car and had 5 minutes to do it, i'd probably use this method and not feel too guilty about it. however, if that's all there's required of you, WOT performance and no drivability concerns, a carb would provide better atomization and it would be a much cheaper solution.
that's what i see PE/IFR tweaking as--carb tuning for people who are forced to deal with EFI.

to deny the fact that VE changes with mods is equivalent to deny that mods change VE. since that's the whole goal of modding, i'd say that's a bunch of horsepoo. we mod, we get more airflow, we make more power, and since there's only that many ways to achieve that out of a NA motor, VE must change.

 

He also used to have the nickname "Ed Wrong". Dont know much about his tuning personally, but just what Ive read.

 

I don't think anyone is saying the actual volumetric efficiency of the engine is not changing with mods. What I gather from reading others opinions on the VE table is how much and when it is actually referenced when a MAF is still in place, thus the need to make changes to it. I don't think there is any disagreement on the need for VE tuning in a true SD mode.

 

If VE table tuning isnt needed when making extreme changes such as cam, heads, etc. then why do GM TPI, LT1, and LS1 VE tables look so different? There all 350 cubes, there abouts.
Nuff said.......
And as far as Ed Wright comparing GM hardware to DFI, well, they are at their core, both sequential, feedback systems, based on most all the same principals. So tuning a GM PCM "like they're DFI" isnt too far off base.

 

PE tuning is the quick way out. Make some impressive #s on the dyno and OOOHHHHHHHHHH,AAAAHHHHHHHHH, the easily impressed are just that.
Never seen PE tuning cure ANY cam driveability problems. OR idle problems.
That being said, the closer the VE table is to correct, the LESS PE needed to achieve a given A/F ratio

 

If you ask me, I think some feel that if they say **** with enough confidence, there won't be anyone to question what they have said....and then it'll be taken as fact.

The VE needs to be tuned if you want a car that performs well on a consistent basis. Stop looking at it in terms of theoretical percentages and look at it in the default units: ((Grams*Kelvin)/kPa) That to me says that the engine can flow 'x' amount of air with a given MAP pressure at a given charge temperature. Modding a motor is often described (in the most basic terms) as improving it's ability to breathe. Whether you do that with headers, an intake or a camshaft, you're increasing that VE number as the engine breathes easier. In terms of some mods like a camshaft, this may not be true across the board though. A stock camshaft can breathe easier at say 600rpms because of it's design. That's why it is represented with a higher VE - because it requires more fuel to maintain a 14.63 AFR at that RPM. Aftermarket cams don't require that much fuel because the amount of air they can deliver at that same 600rpms isn't as great. Therefore, they require a lower VE value, which translates into less calculated fuel delivered to the cylinders.

The problem mentioned above about the engine cycling rich/lean every second only pertains to closed loop. Granted, you can get a VE very close using narrowbands in closed-loop operation. But, that will only work for ~75% of the table. WBO2's aren't thrown off as claimed above because we tune in open loop. There's no need for the PCM to cycle the AFR because the NBO2's aren't doing **** in open loop.

All in all, believing half of what you see and less of what you read on here is a good approach to learning. So take it with quite a few grains of salt...