dbaker

The Halltech Honeycomb screen will help with this prob.

Sure helped on my 02Z ( unscreened) maf.

\db2
Carolina

Mr.Zee

I'll check it out, thanks dbaker, Mr.Zee

enoniam

Here's a rather blurry example that I found that someone on HPTuner's website posted. It's arranged somewhat like how you described although the rpm increments are different and instead of MAF frequency it uses manifold pressure, because this is how the GM PCM splits this up into different fuel trim cells.

As you can see these cells are independent of how the underlying table's rows and columns are set - yes there are more than 16 combinations making up 16 fuel trim cells. (Numbering of cells starts at 0 not 1).

enoniam

You've mentioned several times that it appears your PCM is maxing out its calculated flow at 233cc/sec. I don't normally use cc/sec units - I normally use g/s.

I plugged in 233cc/sec (after converting to 0.000233 cubic meters/sec) into an online unit converter and find it equates to less than 0.5 cubic feet per minute (CFM) which is a VERY low max flow rate. A 650 CFM carb isn't all that large and I would expect our engines to easily pull in at least 600 CFM.

Are you sure you're 233 is actually cc/sec???

Mr.Zee

Boy did I screw up! No wonder nobody would respond to this.Yes Enoniam,you are correct with grams/sec.Looking at my shop manual confirmed this.I know better,Ijust got confused.After all,cc's would not be an accurate unit,because it would vary with altitude,temp. ect.Grams would be a consistant measurement,even though it would vary in density,it would still be a gram,rite?Please excuse my brain fart!I also misquoted the MAF range.The manual states the Scan tool range as 0.0-655g/s,converting the frequency signal from Hz to g/s.It says the scan tool displays o-31,999Hz.My concern was the MAF stopping consistently at 233grams/sec. at WOT stock.Then when installing VR intake,the Maf didn't change one gram, still 233g/s at WOT.Since we know it gets more air (well documented on fast list),I have a suspicion this may correlate with my high LTFT's.I've been told I need to change the cell parameters?

enoniam

233g/s of air mass flow should support somewhere in the neighborhood of 200-250 hp. Most likely your engine is putting out a lot more than that. It sounds like your tune is flat-lining at 233. The max value for the MAF calibration is 512. Sounds like you've got a dorked-up tune. I'm guessing someone tried to do some scaling to get around the 512 limitation or the g/s/cyl limiations at some point because generally the MAF cal curves will hit the 512 limit before the max frequency limit, with the result being that the steadily increasing curve will flatline somewhere at 512. I've done this in my supercharged truck's tune due to running out of flow headroom in its Spark Advance tables. Got to go back though and keep running the MAF cal curve back up towards the rescaled 512 value.

Mr.Zee

As far as I know,the car was purchased stock,by me,at approx. 30,000 mi.The only parameter tweaking done was an' injector slope' change,in an attempt to bring the LTFT's close to 0 from the +23% ave. I was showing at cruise(1800-2300 rpm in top gear) after installing the Vara Ram Intake.The Diablosport tuner maxxed out at 25%,and I recall going -10 first,and -13% second change,to arrive at 0 LTFT.The tuner stated 'going negative tells the computer to add fuel,going pos. tells it to pull fuel.I took it on a 400mi. trip to lake Tahoe and back,and was too concerned about being too lean,having to make such a huge tweak,and not having a wide band oxy to ck afr,I removed VR,and returned to stock tune.My tuner can't do Maf adj.,nor does it go into ECM cells.I need to purchase a tuner that can change all parameters,to correct MAF problem.Also it needs the capability to manage a supercharger which will inevitably be installed(6psi Procharger).I've been jockeying between HP tuners and EFI live,also there are newer tuners out there that supposedly do all the calc. for you,but I don't know their limits.I want a one time investment that will fulfill my needs for good.Motors are my passion,so I'm not concerned with being 'over my head'.If I need help I will find it,until I can learn enough to safely use it.Any opinions on whats best for me? Z

enoniam

I've been an HPTuners user for I think nearly 10 years now. I like it. For the individual interested in tuning his car and maybe a few others I think that HPTuners and EFIlive are pretty close. What I would think would be the deciding factor for you would be if you know anyone using either one who can help you, bounce tuning ideas off of, etc., then going with what they are using would be best. You can email scans and tunes back and forth to share ideas and get second opinions. If you don't know anyone personally using either product than what are most people (and the ones most active in trying to help others) at this and other forums you belong to using. I know HPTuners has a pretty active forum - I would guess EFIlive may as well but I don't know. One other factor that may or may not be that important to you is the EFIlive is coming out of New Zealand, HPTuners folks are in greater Chicago.

The area that I think EFIlive has an edge is in its support of professional tuners doing mail order tunes. They sell some less expensive interfaces marketed solely at these folks who can mail them to customers (after receiving a deposit for their cost) so that they can then have their customer email the scans to them and they can tweak the tune and email it back to the customer who can then load it using that interface. When the customer is happy he can send the interface back and get his deposit back. HPTuners sells 2 levels of interfaces. Compared to their lower priced one the higher priced one can record data without having a laptop in the car hooked up to it and it also has analog 0-5v discrete inputs and outputs so that users can also log 0-5v signals coming from wideband sensors, fuel pressure sensors, trigger something, etc. I personally use those to record data out of my wideband sensors, and since my main tuning laptop has a dead battery I greatly appreciate being able to record scans on the interface and then take it into the house to download into the plugged in computer.

Mr.Zee

I very much appreciate the input.Right now,I'm changing my harmonic bal from stock to the super damper,(pinning it),in order to be set up for Procharger in the future.Meanwhile,I've got an elec. water pump,catch can,short throw shifter,coil overs,t1 sways,and more,to install.I'm going to research the forums,purchase tuner,and start a little at a time,learning tuning,while always consulting availiable help.I understand its possible to set up to toggle to a higher performance tune,when needed?Meanwhile I'll always be reading Corvette Forum.You'll be hearing from me again,and I feel I've gained more priceless knowledge from you guys.Respectfully, Mr. Zee

Sox-Fan

I'm late to the game here, but with respect to the Vararam, we had a hell of a time tuning mine before adding the Halltech screen that dbaker referenced. That made a lot of difference.

Mr.Zee

Saw your message. Being that I never could resolve my maxed LTFT problem, I pulled the Vararam. Now that I'm working on upgrades again, the Halltech screen info was uplifting to say the least. Called Vararam, and got all negative feedback on screen. Determined to resolve this, I ordered Halltech anyway.Haven't been able to reinstall Vararam and screen yet but will soon. I'll post the outcome. Thanks Z

Sox-Fan

I don't even have the Vararam anymore. Threw it in the trash. The honeycomb screen did indeed make a world of difference, but in the end even that couldn't overcome all the rest of the Vararam weaknesses.

Zip Corvettes

WAIT +25% LTFT????? Have you checked for a Vaccum leak, there is no CAI that will throw the A/F off by 25% or more. The max the LTFT can do is 25% and you should get a cel after that. YOU have a vaccum leak, and since you just installed that CAI I would go back and look at all the fitting after the MAF. It doesn't matter how much more air will flow through the new CAI, when it passes through the MAF it get read and the the ECU adjusts the injector pulse to give the asked for EQR based on the Stoich table. If the CAI were flowing too much air than you would be past 512g/sec and a maxed out HZ scale on the maf. Sounds like you just have a vaccum leak. Unless you have a SC on your car you should not be maxing out the MAF.