That's correct, or so it seems. I have over 500 drag strip passes on my car, and last Tuesday installed the Vararam (which I got from a forum member) and went to the track on Wednesday. The first run started the "sputtering/surging", and today I went back with an extra MAF. The car has tuning in it from LS-1 Edit or EFI Live because I have both, but today and Wednesday was the EFI Live tuning (always worked better then LS-1 Edit) and neither MAF made a real difference.

 

ESBESQ:
1) I have a stock datalog for an 02 Z06 (mine) I can send. I will try and post w/link later today.

2) Stock ~= 0.92lb/min at IDLE and ~42lb/min at WOT ~= 6200rpm. Note, at WOT the airflow
BETTER CHANGE!! else the airbox was a waste. At WOT, I use the O2 sensors as a measuring
tool. If avail, wideband o2 sensor before/after.

3) There are 2 ways to basically fix the Airbox problem that are easy.

a) My method of MAF DATA adj ( which I don't think predator allows and which I now think is best )

b) decrease fuel inj size starting at ~5%, then datalog. This is essentially a way to lie to the pcm and think it has smaller inj that it has.


RED98C5:
Have tested MAFs on dyno. Screened = ~5rwhp less. Both have different MAF cals in pcm.

NOTE, the airbox requires a slight change in your tune!!! Its obviously slightly diff than your old airbox.

Would like to recommend HP Tuners to you guys. easy to use datalog system included.

 

You are 100% correct....I meant to say that my car runs in closed loop when in vacuum...not open loop. Thanks for your explanation though.

I also believe I found the error when I put the car on my lift the other day...I was going to check the 02 sensors. I noticed that the driver's side wasn't connected....I must have not got it snapped or locked into place originally. So everything was fine for awhile then it must of came out.

I only hope that the brief time I ran the car it was too lean on that side....with an 02 disconnected...does it run lean or rich?

 

I'm no expert, but it seems to me that you now need to modify your tuning. When I starting having the problems that you appear to be having, I called up Vararam and spoke with their tech guy. He said that the Vararam throws in more air than the system is accustomed to. He said that even a dyno will not calibrate properly for the Vararam because the Vararam increases the air supply by up to 30% while the car is moving and since the dyno is performed on a stationary platform, it will not sense this increase in air. Thus, if the dyno-tuner doesn’t set the parameters to compensate for the Vararam while you’re driving the car, then the tune will be off.

Consequently, more air being pushed into to the intake causes a lean condition and when you add a preexisting tune to the mix, the system is leaned out too far. Evidently, since the Predator's tune (and I suspect your tune as well), already creates a lean condition to begin with, the PCM cannot adjust and goes into limp-home-mode. That’s what causes the car to run crappy. I was nearly flooring to move up to and past 80 or 85 MPH.

The Vararam guy's suggestion was to "bring in the timing curve, making it 2% faster" and "raise the air-fuel ratio 1 point across the board," making the system run closer to "8% richer." If you can make sense out of that, then you'll probably be able to solve your problem. If you can't (like me), then you should uninstall the tune. Needless to say, I opted for uninstalling the tune since Predator essentially refused to help me figure out how to do what the Vararam guy wanted me to do. When I did this, I found that the factory setting worked very well particularly when it "learned" how to cope with the Vararam; it now makes very good power.

However, according to 427CPE above, the Vararam still needs a tune to get it keyed in properly. In this regard, I defer to 427CPE since he seems to be very knowledgeable about this. I’m going to try to figure out if I can use the Predator to carry our his suggestions. However, since it turns out that I'm functionally retarded when it comes to tuning the PCM with the Predator, I’m also looking into a professional tune.

In either case, I have to say, even without the tune, I think the Vararam works great with the stock program; so I can't wait to see what it can do with the right adjustments on the PCM.

GOOD LUCK.

 

YOU ARE THE MAN!! Thank you. I presume that the 02' Z06 is the same as the 03' (mine) right? I know there was a difference between two years; I don't remember if it was between the 01 and the 02 and/or the 03 and the 04.

Anyway, I think I remember seeing that the Predator has a MAF read out in the real-time diagnostic mode. However, I don't know whether I can adjust it or not. I know that I can adjust the LTFT with the Predator and I beleive the power enrichment and all that stuff. I'd appreciate it if you could let me know whether adjusting these parameters will get me to where I need to be.

I'm going to take the car out on a drive today and I'll try and log some numbers - hopefully my girlfriend can do it right since she'll be sitting in the passenger seat.

 

Don't adjust Power Enrichment vs RPM (PE) yet. Make sure you have the MAF dialed in first then if you want to mess with top end fuel, go ahead. The 02 and 03 I know have the EXACT same MAF data. I had both an 02Z and 03Z.

Log the car mainly at two points.

Make sure the engine is warmed up first, then:
1) IDLE for about a minute or two. NOTE: When you crank the engine, its open loop. So best done after a short drive.

2) WOT I recommend a firm acceleration to WOT without spinning tires but make sure you are 100% TPS. Let off < 6400 rpm.
Do this 2 or 3 times to get a few samples. Also, another easy way
is to drive about 55, then put it in 4th and floor it for a second or two. This is a good way to spot check the mix.

Send me your logs and I'll make some recommendations IF you are interested.

Stock Z06 Datalog (Comman Sep) CSV
Stock Z06 Datalog (Excel) XLS


NOTE: Be careful about tuning for optimum power when its hot out defined as > 98F Intake Air Temp(IAT). At this point the pcm starts pulling spark at -1 degree up to a max of -8. This will kill power and cause a slightly richer mixture. HOWEVER, when its cooler out you will end up with more spark and a leaner mixture. I tend to run my engine at factory a/f conditions.

 

The problem is that the Predator cannot "log" the data like your program. The best I can do is have my passenger take down a reading or two while I drive. The Predator is nothing more than a $400 piece of crap! Anyway, I digress; also, the values that you have for your LTFT are way different than what I got while driving at or about 75 MPH for a sustained duration of time. To this end, I got 18.75% on bank 1 and 17.19% on bank 2 for the LTFT. That doesn't sound right particularly since your's are in the 7.8 and 6.3 range at or about the same rpm (+/- 2000). Also, my MAF value was around 3.

So either I'm reading this data wrong, or I'm doing it wrong altogether. Whatever the case, after seeing your log, I like to make it a point by saying that the Predator is a $400 piece of CRAP!!

But i digress yet again. So, does this info help you figure out what I'm talking about in anyway?

 

Actually, you were successful. You just told me your fuel trims are WAY HIGH and therefore your engine is lean. Those are exactly what I would have expected. You pcm needs a tune up. What are your STFT?

At this point, if you want your engine to run right, you are going to have to do it yourself. You have clearly indicated by LTFT your pcm needs a tune up.
Also, did you get a WOT 02 reading?

 

WOW! I thought for sure I was doing it wrong. The STFT is hard to guage because it changes nearly every second. It goes from negative values all the way up to +19% depending on whether I'm gassing it or not. As for the WOT, I tried and practically ran out of road - I live in LA, not much room to WOT it out here. I'd probably have to do it later at night time.

I'll try it on my way home tonight. So, my understanding is that I should drive it at or around 75-80 mph for a good 10 minutes and then hold it open in 4th for a few seconds - while taking the reading of the 02 sensors, right?

If that's the case, I'll try it - but the damn thing gets up to 120 in a heartbeat and it's hard to keep an eye out for the cops and other motorists while reading the Predator at the same time - however, somehow, I think I'll manage.

 

No!! Try around 55mph in 4th or 5th then the car won't take off so quick. Also, try and get a WOT in top of 2nd if feasible.

Get STFT at IDLE only. Try and see what the range is.
I expect they will be high.

Either way, your LTFT tell the tale of the leaned engine using a Vararam and others like it.

 

We'll do; and again, YOU ARE THE MAN!

By the way, the LTFT was taken while I was driving around 75 MPH right at or just under 2000 RPM; I don't know whether that matters or not.

 

I would prefer see:

IDLE: STFT and LTFT while car is warmed up and not moving. Based on my testing, these are very good indicators of how far off the maf pcm calibration is. My theory is there is no flow difference for a stock vs aftermarket airbox, therefore any measured difference of airflow at idle represents the correction needed.

WOT: O2 readings at either at top of 2nd and/or lugging 4th at 55 or so.
I know its hard to believe, but I have found even on lugging throttle conditions, the A/F measured by the O2 is close to the same as it is at WOT at 6400+rpm.

In my case, I'm able to turn on the laptop pc and let it log while I drive. So I just create the driving scenerios, then pull over at look at the data. A WHOLE LOT safer!

 

The difference between you and me is that you didn't buy the Predator, so you didn't get ripped off. However, it's better than nothing, I guess. Although I much rather have spent the $400 on the HP Tuner program that you recommend. Live and learn.

 

Here's what I got:

O2 From 65 MPH in 5th to WOT: 915; 935; 915; 940 (I couldn't do it from 55MPH because people kept pulling in front of me.)

STFT 1 @ Idle: -0.78% to -3.13%
STFT 2 @ Idle: -0.78% to -3.13%

LTFT 1 @Idle: 23.44%
LTFT 2 @Idle: 21.88%

One thing though; I forgot that you also wanted the LTFT at idle and when I remembered, 20 minutes had passed since I had driven it; so I took it out, drove it around a bit, tried some WOTs in 2nd and then I pulled over and took the reading. As for the WOTs in 2nd, the best O2 readings I got before having to slam on the brakes were around 940ish -even then I wasn't sure that it was a complete WOT pass. WOT in 2nd gear is very hard to do without getting into trouble around here.

I hope I did it right.

 

[QUOTE=ESBESQ;1560727638]Here's what I got:

O2 From 65 MPH in 5th to WOT: 915; 935; 915; 940 (I couldn't do it from 55MPH because people kept pulling in front of me.)

STFT 1 @ Idle: -0.78% to -3.13%
STFT 2 @ Idle: -0.78% to -3.13%

LTFT 1 @Idle: 23.44%
LTFT 2 @Idle: 21.88%

QUOTE]

WOT: Slightly rich. If it was hot outside, I could see the IAT taking out some spark and causing this.

STFT: At that second indicate, too rich and are pulling fuel at a normal rate.

LTFT: Indicates correction for a lean condition.

If I were tuning your car, I would clear the fuel trims and get a baseline.

From looking at the data above, it appears as if your pcm has somewhat corrected the lean condition, and is now running slightly rich on top and at idle. Its hard to tell with small data samples though. Your LTFT counters this indicating corrections for a lean condition.

So, you look "safe" for now (based on the limited data), but still need a tune up. Keep in mind I sample about 20,000 data lines.

 

I'm surprised that the LTFT's are that far off at idle with a vararam. I have a vararam and I don't recall them being that far off. I ended up making it about 10% richer across the board (idle thru WOT) with the vararam...definitely not 25%.

Looks like fouled O2's or a vacuum leak if you're at 25% at idle. Before you do any serious tuning, make sure both of those possibilities are investigated. If you have a logging program that charts data, you should see sharp changes in the 02 voltage. If its "lazy" it will have rounded curves and the range of the voltage will get smaller and smaller (eg. a good 02 will jump from approx .1 to .9 volts...but a lazy one will often only go from .4 to .6).

I'm no professional tuner, but 25% at idle doesn't look right for just bolting on a vararam. JMO.

 

I had to go 14.8% w/Stinger. The Vararam on my last car had numbers right at 25% in some cases. I think I adjusted it 13.5% when I did it a LONG time ago. I ended up firing the Vararam for the Halltech Tunnel system way back when. Turns out more midrange power w/Halltech anyway and same top end.

 

Thanks; I really appreciate your help. There's a pretty reputable place out here that turns out could tune the PCM using the Predator - 4 Wheel Specialties Unlimited. It'll cost around $75 and I figure it's worth it. Although, do I really need it or should I just let the computer keep learning the Vararam?

Whatever the case, the Predator really turned out to be worthless! It can't even data log properly. What a rip off.

 

Several people in this thread have said they needed to richen the mixture after installing a Vararam.

Is that to say that a Vararam will make a stock Vette run lean, even after PCM learning?

It would explain some of the power gains, but would also be dangerous for the motor if A/F is running above 13:1.

 

I won't rag on the Predator, but companies who make those hand held tuners can take them and ...well you know.

HAVE THEM RETUNE YOUR SYSTEM!!! You can thank me later. Also, your datalog is incomplete, so while STFT/WOT show rich, more samples would give a much clearer picture.

Note, if you are a real cheapo, I have written software to use a $159 B&B USB and DB9 cable to read the SAE data and store it in XLS files. I have not released it the public, though I do use it from time to time on my FORD Ranger. You would need a laptop though.

I would NOT drive my car using an aftermarket airbox without a tune. This difference is that significant. For the love of Corvette HP, have some one tune your 50K vehicle.

I used to hate on the Vararam and I still think the +pressure claims are bogus, but its as good as any other airbox I guess when the pcm is tuned for it. I will give it an A++ for cooler air induction instead of underhood air draw and it will surprise you when tuned right I'm sure.