Fbodyjunkie06

iTrader: (10)

Coil packs could be going bad, spark could be blowing out, frayed spark plug wire etc. etc.

Sounds like a spark issue to me...

TracyRR

iTrader: (8)

new wires and plugs with no change. If the stock rockers don't help, i'm going to hang some new coils on it. I agree with you and chris, it does seem like it would be blowing the spark out or valve float.

stevieturbo

It could be overfuelling. What wideband are you using ? and is it confirmed as accurate and able to read very rich mixtures ?

Either that, or it is an electronic issue. Either crank or cam trigger problem.

El_Diablo

iTrader: (9)

Subscribing. You're so much further along with your Vette than I am with mine. haha My 408 with tfs 245s is going in the Camaro though and we have the same valvetrain so I'll be watching this.

TracyRR

iTrader: (8)

I'm using AEM. I compared it to what geoff at EPS has on his dyno. It was within a couple tenths of his, mine was richer.

Nitroused383

iTrader: (10)

Did you do a case learn when you installed the new engine? You can bump up your dwell time to around 5-5.5 msec it will help out a bit. I had ls1 coils and my afr would show lean spikes through out the run, swapped to some D585 heatsink style truck coils and all my lean spikes disappeared. Picked up around 90rwhp on the dyno when I swapped coils. This is after I tried multiple plug gaps, plugs and different wires. Confirm your map sensor and map sensor offsets are set correctly.

stevieturbo

Why did you change the coils ? Where you experiencing any problems ? Or just decided to change them ?
What sort of power were you before/after ?

Nitroused383

iTrader: (10)

I had crazy lean spikes in boost and the car didn't run right at all. My coils had 125,000 miles on them at the time and I couldn't get a smooth afr curve. I had been trying to get things dialed in for well over a month before I put it on the dyno. I was diagnosing my issues on the dyno and nothing seemed to be helping (plugs, gaps, wires etc...) As soon as I swapped the coils while on the dyno I went from 500 hp / 435 tq to 580 hp / 532 tq, it would hit a wall right at 3800 rpm when full boost hit (7lbs). I have multiple hptuners logs and dyno sheets. I guess I lied it was actually 80 hp / 97 ftlbs.


Here is what the AFR looked like before I swapped coils

TracyRR

iTrader: (8)

You will get there diablo! With the boards help, i'll get it worked out

Nitroused, i'm new to tuning (efilive) so what is a case learn? I just checked, my coil dwell time for 14 volts is set between 3.6 and 3.2 msec (tapers down with increase in rpm). So i should set everything to 5 - 5.5 msecs? I'll look into the truck coil thing also. also, what should my map sensor offsets be? Thanks!

TracyRR

iTrader: (8)

Unfortunately, no difference on the dwell change. Just like before, it pulls hard to about 5600 and then flattens out above that.... hovers around 5800ish or so. Anyone have any stockers i can try or buy? Thanks

Nitroused383

iTrader: (10)

I am not familiar with EFI life but I know you can do a case / crank relearn with EFI live and hptuners. Anytime you install a new engine or crankshaft you need to relearn the crank position. You could be commanding 20 degrees of timing but the actual timing events could be way off. Kind of like setting your timing marks for a distributor while at top dead center.

What part number is the map sensor you are using? Do you log your wideband afr on your scanner, does it stay smooth or break up while under load? Is the map KPA staying smooth or is it getting wavey above a certain rpm?

Here is a good video to watch that explains a little bit about dwell timing and the difference between ls coils http://www.youtube.com/watch?v=C1WH0OExQyA

icicleboy

Nitroused383,

do you realize that your commanded AFR was changing when you had lean spikes? This had nothing to do with the coils you were using. Your AFR went lean when the computer commanded a leaner mixture.

TracyRR

iTrader: (8)

hey nitroused, that was pretty interesting... this might not be my issue but i'm still going to upgrade coils to the d-585's. Also, i'll research the case relearn with efilive. Thanks man!

Nitroused383

iTrader: (10)

No my commanded AFR did not go lean at all, this was just one example of my logs where it went spikey like this. The only change in Commanded AFR was when boost enrichment enabled which put it at 11.3:1 commanded. Always in 3rd and 4th gear, yes the coils were the issue but thanks for your input. Maybe you are refering to the lean spikes in between shifts, which doesn't matter one bit at all. I will sell you my old coils if you think they are good.

No problem Tracy, you will get it figured out. Somewhere between the crank learn, coils and stock rocker arms

TracyRR

iTrader: (8)

hey nitroused, what parameters did you use in your tune with the d585 coils? ie: dwell, ect...

stevieturbo

It is highly unlikely the coils are the problem.

Im using standard 2001 LS1 coils with around 4.0ms dwell time and have no issues.

Are you using a stock crank ? Has this engine always suffered the problem ? Will it rev cleanly sitting stationary ?

TracyRR

iTrader: (8)

hey stevie, no, i don't think the coils are the problem at this point and at the boost level i am at now. Just sounds like an inexpensive upgrade for when i crank the boost up (25 pounds) at the track. This is a compustar crank and the car runs great in all conditions except for high rpm's while in second/third gear. First gear, with limited traction will buzz 6600+ rpm's.... I really think it is still floating the valves still because of the heavy rockers and the XER lobes. My previous motor would spin to 6500 rpm's and i was using the same coils. Thanks for helping. tracy

stevieturbo

So you can rev to and sustain 6600rpm when sitting stationary ? All the time, every time ?
And does it do it regardless of boost pressure ?

I doubt it's valve float. Ive used a couple of different cams and even with plain average springs never had a problem.

I'm now using a GT9 cam which has pretty aggressive lobes from what I understand, and with the Patriot Extremes mine will spin to 7k with ease.
Their installed seat pressure on mine is nowhere near what you have. ( assuming the pressure gauge thingy I have is accurate )

TracyRR

iTrader: (8)

Yes, in first gear it will hit 6600+rpm everytime but will not do the same thing in second/third. I have not run less than 13 pounds with this combo. I would have thought i have plenty of seat pressure but won't rule out valve float until i bolt the stock rockers on this weekend. If that doesn't do it, i have some larger exh housings i will bolt on even though my backpressure was pretty good. Thanks for the info!

TracyRR

iTrader: (8)

Update: I installed the stock rockers and went for a little logging..... With just changing back to a stock rocker, it makes much more power above 5000 rpm's. I had to turn down the boost (at least two pounds) to get this thing to somewhat hook in second gear like it did with the yella terra's. Because i had limited traction, i need to blast it again at a lower boost level to confirm my results but it looks like it was freaking valve float!! I can't believe a little less weight on the rockers makes that much of a difference with my combo..... I will update if anything changes but thanks for all of the help guys!!

p.s.... i also wanted to mention that it leaned up the afr above 5000 rpm's by almost a point!! I had previously had to pull some fuel in that area and now i know why.....It obviously is flowing more air now.