Mr.Zee

Hi There,I installed a Vararam air intake on my 04 zo6,thats when the problems started.Upon checking real time data with my Diablosport tuner,my Long Term Fuel Trims went up to +23to25 at WOT.With stock intake,the Maf always showed 233cc's/sec. of airflow at WOT.With the Vararam,I still showed the same,233cc's/sec.I've read that my computer 'learned' this amount while running 'stock' intake.This is the first time for any 'bolt ons'.Also, when taking a logging trip down the freeway at cruise(approx.2300rpm. top gear),I could fell surging in the motor.It was a windy day,but never felt it before.It proved to me it was getting a reaction to the air intake,especially with the change in FT's.No vacuum leaks.I read this intakes effect would be compensated by the computer,up to 10% without throwing a light.Well it did that too.Any help please? Thank You,Mr.Zee

aaronc7

I ran this intake before on my car (03 Z06). It gave me around +10% fuel trims which I was able to correct with tuning. At 25% I would suspect a post-MAF leak....double check.

I also got low rpm surging... no tuning was able to get rid of it. If you look at the MAF flow or voltage in a datalog, you'll notice it a lot more noise or "spikiness" in the signal with the Vararam compared to stock. I believe the design causes extra turbulence in the airflow across the MAF...no really nothing you can do about that.

Mr.Zee

Thanks for your help.What about my maf pegging at 233cc's/sec?Obviosly the vararam is supplying more air,and I would think this would account for the high ft's.If you get a chance to compare the stock readings to after installing Vararam,I'm curious if it shows a difference in maf readings.

aaronc7

Fuel trims aren't a good way to measure or determine more air/more power.

The MAF outputs a voltage or frequency (Hz) to the ECU and then the ECU/mapping uses the value to determine how much air is actually flowing for that given moment and injects x amount of fuel for y amount of air. The ECU uses fuel trims to add or pull fuel as required to maintain the target AFR of 14.7 using the factory narrowband O2 sensors. There's other factors at play but that's the basics.

For example at idle on my car... MAF frequency is right around 3000hz, which my MAF table in the ECU "knows" is right around 8 grams / second of air... and my fuel trims are spot on in most circumstances. So it's safe to say that my motor uses around 8 g/s of air at idle since fuel trims are spot on.

If I go and change intakes and my fuel trims go up to +20% lets say... we know that my engine really is only using around 8 grams / second of air to maintain whatever idle rpm I have set. The reason I would be seeing the +20% fuel trims is because the MAF frequency being sent to the ECU is now different -- let's say the MAF frequency is now 2500 hz. In my MAF table, that hasn't changed, 2500 hz = 6.4 g/s of air. So the ECU was initially injecting 20% less fuel as it was "seeing" less air as well with the new intake. Fuels trims brought it back up using the O2 sensors as feedback into the control system.

So long story short, when installing that new intake it's just changing the characteristics of the airflow across the MAF, which causes the ECU to 'think' it seeing more or less air than before, when in all actuality it's probably about the same amount of air for a given condition (idle, cruising at 60 mph in 6th gear, whatever).

To compare your MAF g/s (at wide open throttle) before and after accurately you need to get your fuel trims spot on... then you can accurately gauge the new setup is flowing xx amount more air, etc.

Bottom line, you need to make sure there are no leaks in the system post-MAF (20% fuel trims still seems high to me)... and then ideally you would get the MAF table 'retuned" so fuel trims are +/- 5% or so. This will help ensure proper AFRs at WOT.

Mr.Zee

aaronc7,Thank you for your input. Mr.Zee

tblu92

Any efficient CAI especially a Vararam will make you fuel trims go way positive--- Actually this is a good thing --it's showing that your P/T fuel is lean due to more aiar being inptted into your engine---
However--you need to drive your car 50-75 miles in all types of driving to let the KLTFT's settle down before making any corrections as you will be constantly chasing your tail
Remember---any positive LTFT "just before going to WOT will be added to your WOT fueling as well as a safety---Any negative LTFT wi;; always lock on "0" JBWOT
you want to always shoot to get your P/T LTFT's at "0"or slightly negative--so the ecm will not add fuel at WOT--- Just think at P/T if your LTFT's are +20 at WOT you are addinging 20% that is horribly rich and lazy !!! Most don't realize in order to dial in your WOT fuel---you must 1st get all your LTFt's at "0" or slightly negative or you will never get the WOT AFR spot on

Mr.Zee

This was a while back,and I was so concerned,I removed VR,and I didn't mention my SLP LT headers.I was scared being too lean.The Rep.atVR kept saying I was"pig rich",while myDS predator tuner said, "+FTrims add fuel".I'ts starting to make more sense now.I pulled my LTFT's back about 20%(close to 0),and WOT back half of that(as the tuner told me to).Then aborted the whole thing(removed bolt ons),and went back to stock tune.I still run ave.+10%LTFT stock.Im working on it now.But will soon be on the road.I'd like to do a propane ck for vacuum leaks.But even went to dealer,who tested it,and said, LTFT's are in the +6 range,runs strong.I'm confused,any more input would be appreciated.Thanks,Mr.Zee

aaronc7

If you ever get back into the modding game and are sticking with relatively basic and common mods... i highly recommend looking into getting an EFIlive Autocal w/ remote tune support. That's what I did- I have a flash tool that I can use to datalog, save, load tune files and I have unlimited revision tune support from a well known/respected tuner. Cheaper than getting HPtuners or EFILive "full suite" and miles better than a handheld tuner with 'canned' tunes only. PM me if you would like so more info.

enoniam

As noted on your other thread about basically the same thing, you need to adjust your MAF calibration settings so that your LTFTs are running slightly negative. I shoot for between 0 and -5 for most of them.

Note that I said most of them. You have dozens of stored LTFTs. You have nearly 2 dozen for each side of the engine. Under "normal" operating conditions you have 16 fuel trim cells for each engine bank, and each one of those 32 cells stores its own LTFT. (Non-normal LTFTs are stored for warm-up, EVAP system testing, etc.)

Each bank's normal 16 cells are arranged in a 4x4 matrix by engine rpm and intake manifold pressure. At WOT you will be in cells 12, 13, 14 or 15 under "normal" conditions. In reality you will spend little time in 12 because that is the lowest engine speed range and possibly mostly in 15, the highest rpm range. You don't have to be at WOT to get into these cells with the possible exception being 15 as at low engine speeds it doesn't take too much throttle to get high manifold pressure.

In a stock (non-speed density) tune the main contributor to where you LTFTs end up, assuming no air leaks, bad O2 sensors or other improper operating condition, is the MAF's output and how that gets correlated to an airflow value via the tune's MAF calibration factors. The Vararam intake is flowing air through the MAF a bit differently, causing it to "see" less of the airflow.

You can be running a good LTFT at idle or just cruising down the road but those situations will not put you into fuel trim cells 12-15. When the engine transitions into a different fuel trim cell it uses the last stored fuel trim for that cell - the LTFTs can therefore jump instantaneously.

From what I've seen the handheld tuners don't show what fuel trim cell you are in and therefore average them all together and therefore while they can show as in your case you have an airflow calculation issue they aren't always real useful in helping to identify exactly where the tune needs to be tweaked. HPTuners and I'm pretty sure LS1Edit can give you that info to help fine tune your tune.

tblu92

The positive fuel trims are added to WOT fuel wherever Your MAF HZ signal is "JUST BEFORE GOING TO WOT" So depending on when you floor the throttle the positive fuel trims can lock on the positive trim way down in your RPM's--Typically it's around 3500 to 4000 HZ on your MAF table or even as low as 2000 RPM !! You can carry that added 25% from a positive fuel trims from 2500 and it will carry thru out the entire WOT range---That is why its so important to dial in all your P/T fuel trims from idle up to about 4000 RPM's or 7000 HZ--- These adjustments can be made specifically only where you need them if you data log your HZ table with LTFT's as the data---
You do not want to add the 25% over 7500 HZ because that is typically WOT--but if you clean the LTFT's at P/T they will all go away at WOT from the adjustments you made in P/T----
Also you are just guessing at your "actual WOT AFR if you are NOT using a wideband 02 sensor---
CAI will typically make your WOT fuel leaner
LT headers will make it richer

Mr.Zee

Gentlemen,I very much appreciate your input.This makes me realize,even more,what a project I've gotten myself into.I purchased this car 3years ago.My original plan was to install LT headers,VR intake a Diablosport tuner,and retune to these bolt ons.Sounded easy,but you can see what the results were.Now to mention the rest.I'm now working on the installation of the Phaat coilovers, sway bar elec. water pump,catchcan,short throw shifter,and last but not least my p1sc1 procharger.I know that's a big order.I've got the mechanical skills.But as you can see,just started evolving into OBII tuning.(I was on hiatus for 20 yrs.) I plan on going back to where I left off on the engine bolt ons.But am torn on having it dyno tuned,or purchasing EFI or HP tuners because I want to learn,but not at the cost of making a mistake and imploding my motor.Is it possible to upgrade from EFI Live?Well I;ve got a lot of work to do.Any input is appreciated,and I'll be back for more help after phase 1(before supercharger) Thanks,Mr.Zee

aaronc7

With a supercharger, I would opt for the HP tuners pro version or the full EFI Live flashscan tool... these options are more $$ but they allow you wire in a wideband input, which you will definitely want. First though, you should probably figure out who is going to be tuning it... talk to that shop or guy and go the route that they prefer. Probably not the wisest choice to learn on a supercharged motor that may already be approaching the limits of what's considered safe.

enoniam

Word

enoniam

I don't think I agree with this - maybe it's just my poor understanding of what you are trying to convey.

I don't know how you can describe how this works without describing the fuel trim cells - you seem to not want to address them???

I've tried to attach an image that I just stole from someone on HPTuners' forum that shows where fuel trim cells 0-15 apply on the 4x4 matrix of engine speed versus intake manifold pressure. At least in HPTuners the cell column and row breakpoints can be changed, but I don't think changing them is done by many tuners. As can be seen in the table rpm-wise, it is pretty much broken into idle engine speed (below 900 rpm), just off of idle (900-1200), normal cruising (1200-2200), and accelerating/high speed (above 2200). Manifold pressure wise you are pretty much looking at no load (below 33 kPa), light load (33-55 kPa), medium load (55-77 kPa) and high load (above 77 kPa). (I may be a bit off on the cell column/row breakpoints - these values are from my memory...)

At WOT (without forced induction) you are going to have close to atmospheric pressure, which is generally around 100 on this scale. That puts you in cells 12-15.

The engine stores the last LTFT it had on each bank for each of these cells. The LTFTs are only adjusted when in closed loop operation using data from the upstream O2 sensors. WOT is NOT closed loop. The computer goes into Power Enrichment mode and adds fuel. The stock narrow band O2 sensors cannot accurately read the AFR outside of stoich (14.7 AFR) so since the computer is now blind it is no longer operating in closed loop making use of O2 sensor feedback info.

You don't have to be at WOT or in Power Enrichment mode to get to cells 12-15. I forget some of the stock setting off hand, but you have to reach a certain (high) amount of throttle opening to get into that mode. So you can be at say 75% throttle which will give you a lot of intake manifold pressure in many circumstances putting you in fuel trim cells 12-15 and still be in closed loop and therefore setting the LTFTs for those cells.

If when driving you were already in fuel trim cell 15 then I agree going into WOT you are going to keep the same positive LTFTs that you had before going into open loop operation. (If they were negative they jump to 0 at WOT.) If you are instead in fuel trim cell 11 or less when you hit the throttle the computer isn't going care what your LTFT was when you hit the throttle - it's going to see the manifold pressure go up and jump into one of the high load LTFT cells. If it goes to cells 12-14, it will then change the LTFTs when it gets into the next higher cell as the rpms push is along through cells until it gets to 15.

In my 03 5.3 LS-based truck, I can get into fuel trim cell 15 pretty regularly when I go uphil and the truck either unlocks the converter or downshifts into 3rd. (Between the truck's big cam and high stall converter it sees 3000 rpm in regular driving pretty regularly.) In my much lighter vette it isn't going to see cell 15 nearly as often because in normal driving the slightly larger engine doesn't have to work nearly as hard to push the much lighter and more aerodynamic vehicle.

I don't know how much "normal" driving puts your vette into cell 15. If you aren't an aggressive driver and between your car's gearing and your typical highway cruising speed your car doesn't see much time in the rpm range shown for cell 15 there may be a fairly small window of operation where the cell 15 LTFTs are being set. At the very LEAST you probably need to add to the MAF calibration at that point. Unlike tblu92 I don't normally think in a particular MAF frequency point or range - I look at what my calculated MAF airflow is in my data logs for where I need to adjust, find values close to that in the MAF calibration and adjust those points, whereever they may be on the frequency scale. Obviously there are limits but I'm also usually concerned with P/T. It is true as tblu92 stated that the LTFTs are established at P/T, because that's where you're operating in closed loop, but one has to keep in mind that there's a lot of them. However if you are off by as much as you are at P/T and with the minimum amount of airflow you are going to see in cell 15, which is pretty high, there's a good chance your MAF calibration is going to be off all the way to the top end.

Mr.Zee

All I can say is,I'm trying to soak all of this in I can.In answer to a couple things.First,I believe I may have mistated at the beginning when I said +25%LTFT at WOT.I remember Diablosport intruc. telling me to drive 50 mi. or so then do a real time data at 2000-2300rpm in6th(70-75mph)cruise consistently for 15min.Then ave.out yourLTFT.If it ave.+15%,then go in and add -15% to get to 0 to-2 ideally.Then it says to go to wot FTand go 1/2 of -15 or say 7,and adjust -7 on WOT.They claim on comparing to dyno tune with wideband A/F,this is very accurate.And yes Ido plan on getting wideband. thanks, Z

enoniam

I've never used the Diablosport tuner myself, but after reading the above I seem to recall that it doesn't have the capability to tweak the MAF calibration but instead tweaks the fuel injectors calibration instead. I say that since you have been instructed to subtract 15% if you have a 15% LTFT which fits adjusting the injectors' calibration - you'd need to add 15% or so if adjusting the MAF's calibration.

The downside to adjusting the injectors' calibration instead of the MAF's is the use of the calculated airflow by the PCM to figure out spark timing, although it may not make much of a difference for your CURRENT WOT since your spark advance table probably just hits close to 30 degrees at healthy airflow/rpm combinations and just stays there.

When you go forced induction you may well need to ramp down your spark advance and not have the spark table flatten out as it is probably doing now. Then when you make induction changes that affect how the MAF is reading airflow if you were to correct the airflow calculation instead of just accounting for the fueling difference with the injector calibration then your spark timing tables are kept "calibrated" as well.

tblu92

Maybe it's because I am using EFILIVE and you are using HP
you don't understand what I am saying--However I am sure about this I learned this in my training ---
Not really sure what you mean by cells 1 thru 15--In efilive to data log and correct LTFT's you use a PID with :

Rows are in RPM (0-8000) 500 increments
Columns are in MAF Frequency ( 0-12000) 500 increments
Data in LTFT's ( left bank 1 or right bank 2)
That would give you aprrox 400 cells in that PID that can record LTFT's---NOT just 15 ---

Mr.Zee

Hey guys,Your input has refreshed my memory. It's been a while since I've driven and attempted tuning my vette.Diablosport called it 'logging and adjusting injector slope'.And,no, their tuner wont adjust MAF,nor does it get into computer cells.First they ask you to drive for 20 min. to warm up engine,then to log the following pids;LTFT,Banks 1&2,Oxy sensors up&downstream,RPMs,Spark adv.Then do a cruise in top gear at 1800-2300rpm for 15 min.Then it says to do a WOT(stab it in 3rd at 2500-3000 to red line,or go thru the gears floored.)This was the beginning of my disappointment.I recall the FT running 23-25% at cruise,and Icant remember atWOT,but I think the same.Next time I'll take note of PT before WOT or PE(power enrichment).Their the same right?Anyway then you recalibrate your FTs to 0 to -2,then take half of your adj. and apply to WOT FTs.Now this is without wideband 02's,but if I'm understanding rite,the 0 FTs should be 14.7afr,and when PE kicks in, it goes to bout 12.5/1 afr for safety so it's not too lean at WOT.I do understand w/supercharger,my MAP needs to change from ambient air ceiling to plus 1 atmosphere pressure to handle 6-7 psi.Also timing retard to compensate for bigger f/air intake,ect.But one thing I always wondered, was how this so called 'engine management system' that's included in the Procharger Ca.Em.cert.package just 'flashes',or re-maps the ECM,and your ready to roll.They make it sound so easy.Needless to say the DS tuner,even though you can 'custom tune' with it,they say,has left me disappointed.Sounds to me like HP tuners or EFI pro,is what I will need. Z

tblu92

Ok now I understand the confusion---Tuning 101 dictates only make changes in the tables that are directly affected by the modded parts--
Only re-calibrate the injector flow rate IF you change injector sizes
In your case you added a CAI so the part that is affected by the greater airflow is your MAF---It is seeing more air than stock and is continually adding fuel
I don't think with Diablo you can re-scale the MAF table--So you are trying to correct the LTFT's with the IFR table---Not the correct way---You may see some changes but it will never be spot on---It's like putting a band aid on your wrist when you have a cut finger !!! You need HP or EFILIVE

Mr.Zee

Thanks tblu92.Yes,I want to make one investment,that will take over on latest tech where DS left off.I do understand what was mentioned about a change in the consistency of air passing the MAF after Vararam intake.But we all agree that more air is entering plenum,but this is what I still have a problem with;I researched my shop manual(the 2 volumes for GM techs,165 bucks worth)it goes into much detail.And it states the Maf for my car has the potential to read ccs/sec.up to 700.As I previously stated,at stock, DS tuner showed consistant 233cc/sec. flow at WOT(didn't ck.HZ,but will).After installing VR intake,got the same reading.Something tells me this lack of increase, points to the ECM not allowing a change in the parameter the factory flashed into it.Make sense?If I'm correct,then the ability for EFI live,or HP tuners to go into cells,or parameters, and remap my maf should correct this problem,yes? Z