Andrew91GT

iTrader: (6)

http://naca.central.cranfield.ac.uk/report.php?NID=581

LS1-Inside

Thanks Andrew, but if you really want to help - read the whole thread.

Showing 80 year old studies on carbureted engines, does not explain why my AFR is wobbling, and why i'm loosing like 20hp on back to back runs. Nor does it qualify as data explaining how this problem is only costing me 2-4 hp, when you can clearly SEE 20hp gaps on consecutive pulls. Instead, it's a smug, useless response to a question, obviously not wholly comprehended...

Sorry if i seem a bit brass, but I'm getting tired of smug responses with misguided answers. I was only looking for any additional input before i can get back down to my Tuner. I was hoping to get a group of ideas or potential problem areas that i can help Brainstorm with my Tuner on.

Thanks to those w/ real input.

-Dan

Andrew91GT

iTrader: (6)

Oh noes, your A/F varies just a bit. Call the Waaahmbulance.

I posted up a scientific paper showing that large changes in A/F over a specific range, lambda slightly less than one gives a very small percentage change in power production. Another guy posted up similar information based on his dynoing many engines. If you don't believe that scientific testing on internal combustion engines might apply to your situation then good luck in your search for your "missing power".

LS1-Inside

Like i said - you don't understand the problem man. You're refusing to look at it from the right POV. You're so smug that you found a white paper you can reference and regurgitate to anyone who has a potential problem that you don't realize my AFR isn't what's causing the problem, it's a Symptom. The AFR is most assuredly changing as a result of some other issue with the car, and that Issue is whats causing the Reduction in power. The Wobble in AFR is a symptom, and I was hoping people could help recognize that Symptom and help toss out ideas as to what causes that.

But Keep regurgitating your useless information and pretend to understand what you're talking about, and I'll keep telling you no thanks...


-Dan

Frost

iTrader: (45)

Look at your own DJ graph at the wobble... it's different in every pull and yet the HP varied what... 4 hp? Why are you saying you are losing 20 hp on back to back runs? It's printed on the DJ graph... Don't even tell me that you are comparing those 2 different dynos and calling that a loss.

LS1-Inside

Like i said previously - look at the 5800 RPM range. There's a 20HP gap between blue and green run.

This isn't a problem with my Tune. As you can see in the Mustang dyno - the AFR is laser flat - the PE tables don't just "Change" something else is happening here that is effecting the airflow, and the AFR wobble is a symptom... In addition - my Runs are Identical up until the High RPM, and on top of that, my friends who ran their Vettes at this DynoDay put up 3 consecutive runs that were all right on top of each other, no upper RPM TQ fluctuation, or AFR variances.

It looks to me like sometimes as early as 4500 RPMs for some reason the air supply starts falling short - (Which causes a momentary Rich Condition, and Also a loss in TQ NOT directly from the AFR change, but from LESS AIR) then the ECU compensates by leaning out some (AFR Comes back up to normal) but then once again, less air comes in, causing the Rich AFR again, and the cycle repeats. I have a VaraRam air intake - which had a shitty shitty seal (which i fixed) and Tom and I are thinking try Stock Intake - or No Intake, and see what that changes, as at least one experiment.

Even IF this was just an AFR change - and no other problems, what could cause the ECU to just decide to **** up the Tune? These Tune's are "Microsoft" products, they don't just "Go Bad".... assuming there was NO air delivery (or something else) problem, why would the AFR just start wobbling? And even so - Tom kept a copy of my tune - and he doubts that he'd be able to flatten this out, because he's sure it's not some issue with the Tune.

Maybe your White paper has ideas on Magically Corrupting EPROMs that turn Flat AFR's into Sin waves? lol

-Dan

MeentSS02

iTrader: (11)

You really just need to drop this until you get some more facts in line. You need to log a shitload of data before you go making these random hypotheses...timing, airflow, etc. And I'll tell you one more little secret...going to your tuner with an armful of guesses from the internet will only serve to **** him off...for some weird reason, he'll probably think you don't trust his ability to tune your car.

LS1-Inside

You may be right - but he and I both already talked, and he's positive it's not his tune. He has a few ideas on where to start, and I don't know about the rest of you, but when I bring my car to a shop I like to be able to have some input, i like to be able to discuss the problems, and give feedback, or even suggest possible problem areas. I was hoping to have some input to help Brainstorm with Tom when I got down there. (That was the sole purpose with the thread. I didn't want to have to argue with people trying to get them to understand that i KNOW .4 AFR doesn't drop 20HP, but instead get them to recognize there is some other problem and AFR Wobble is the Symptom, but apparently that's not possible...)

It's a 2 Hour drive to his shop, and I can't go anywhere once i'm there, so wild guesses, and hypotheses were acceptable... I can't just drop the car off and tell him have at it... He knows i'm going to have to hang around - and actually listens to my input and answers my questions. I appreciate your input, but Tom is a very polite, professional guy and he's happy to talk to me about the issues, and I'm happy to have him shoot down my theories... lol

And Listen to me when I tell you I'd BE THERE NOW if the road was open! LOL Did you see that flooding? It's crazy! Parts of I-5 were under 10ft+ of water! The alternative route was a 7 hour drive one way!! I think this morning they finally got some traffic through, maybe a lane or a back road or something is going, but realistically I'm going to have to wait until it's back to normal before i venture down there...

I guess I just saw a lot of posts where people had some random problem they inquired about, and the Members were happy to throw out lots of guesses and help the person start narrowing down problem areas. I've never seen someone complain about a loud ticking noise while Forum Members INSIST it's a rock in their Tire. I guess I just expected a few people to chime in with some places to look... So far, Airflow and Timing are the only two areas. I appreciate those of you who added useful comments!

-Dan

Black02SS

iTrader: (36)

How about this is what Frost is trying to say I believe. Your AFR being wavy isn't attributing for your lost of HP as you claim. If you did lose HP, its from something else as the AFR won't make that much of a difference on a N/A car, trust US.

If you put the car back on Tom's dyno and see the wobble, I'll be you won't be more then 7hp down. The wobble isn't costing you anything, its something else if ANYTHING. How does the car feel? How does it drive? Taken it to the track yet? This is a reason I hate dyno's on some cars. I know of cars that don't make 400hp on a dynojet yet trap 120+mph in a full weight car.

LS1-Inside

Thanks Black02SS - You understand what I was trying to say, if anything AFR is a symptom of some other problem.

Sometime in this following week i should have it back down at Toms, I think I-5 is opening back up this weekend... maybe... If the AFR were flattened, you're right - i might only see a couple HP. Tom always said his Dyno was usually pretty close (a little low) compared to the local Dynojets. But he also said its quite peculiar that my car made MORE TQ on the dynojet, but id tapered off fast, and i made significantly less HP. I suspect my result on his dyno will be similar - something like 360tq, and 380 TQ whereas i was 362 and 400 a few weeks ago. I'm really interested in the results and the resolution!

-Dan

LS1-Inside

(Moved my reply from the wrong "old" thread (379hp) to this one...)

So - I talked to an Engine Build Engineer from VaraRam Industries and he said it sounds like I may be getting knock retard up top... Tom's been super busy as of late, and I won't be able to get into his shop until march... but i have an appointment... heh

The engineer said he's seen worn valvetrain components trigger false 'knocks' that the knock sensor picks up, and pulls timing with... He said KR could cause a waver in AFR and could easily show a good TQ loss for "No Apparent Reason" in upper RPM.

My Tuner told me my rockers were worn when he did the initial H/C/I install, but he said they'd still work - they just need to be replaced shortly... So i bought all new stock rockers. Before Installing them, I got a chepao OBD II scanner than can read all the sensors and monitored the following 3 sensors while making a couple passes:

Ignition Timing Advance Cyl#1
Absolute Throttle Position
Engine RPM

The scanner had a limited resolution of about 1 update per 600-1000 RPM... Not particularly great... but maybe good enough.

On my first two passes, I'd go WOT and see timing like 28, 27.5, 29, and for some reason around 4700-5800 (depending on the run) I'd see timing at 23.5, then it would jump back up tot 27, and 30, before the run finished.

I'm no expert... but that looks like timing is getting pulled for some reason... I can't see the knock sensor count, so I don't know for sure if it's Knock Retard.

I replaced the rockers and made the pass again, last night. After 2 passes i saw timing like 28, 29, 30, 30, 30 - on my first run (~2500-6500 RPM) and on the second pass like 28, 27, 30, 30, 29...

No Dips to 23...

I can't say conclusively that i've even fixed anything, but It's an interesting note. As soon as I get it down to Tom's and back, i'll be sure to update with any more progress.

-Dan