Patrick G

iTrader: (14)

With your A/F ratio looking OK on both runs, I suspect an exhaust restriction. Even NA, your hp and torque level off way too early for the mods you have. This is exagerated on the spray. Try unbolting your exhaust from the headers back and re-dyno. If the "turbo" mufflers were installed backwards, you'd have one HUGE restriction.

98Z28CobraKiller

iTrader: (17)

So I'm the only one that sees the solonoids shutting down?

I agree about the hp is leveling off a bit early. It should pull to about 6500RPM, right?

I just dont understand how it could be the exhaust on the nitrous pull. If the exhaust were plugging it at 600hp, wouldn't it hold the 600hp to 6500 or 6000RPM atleast? If I had flanges on the LT's I would drop it in a heart beat but I had slip collectors with clamps that are indented into the exhaust pipes. It would require more than "unbolting my exhaust". Besides, the mufflers are 3" in and 3 1/2 out. There is no way that they are on backwards. One of the nitrous guys has got to have seen this problem before. I did some scanning, gonna go luck at that.

98Z28CobraKiller

iTrader: (17)

Here is what I think is the problem. This is a scan of a 2nd and 3rd gear WOT blast. You can see that the voltage is dropping at 6K RPM to 12V. You can see that in 3rd gear, it happens at a slightly higher rpm. I imagine that in 4th gear (where the dyno pull is happening) it is happening alittle earlier and may be dipping alittle lower in voltage. I suspect that in the nitrous pull, it is happening even earlier (5K RPM) and causing the voltage to dip even more. Does anyone know how much voltage is needed to hold the solonoids completely open and what happens when you get slightly less voltage? I suspect that they close close gradually and do not just shut off below the required voltage.



Any thoughts? I dont hear the belt slipping. Will a tired alternator behave this way?

383LQ4SS

iTrader: (33)

Id check all grounds, swap alternators, and get a Katech tensioner....check out your battery as well. You likely wont hear belt slippage. You could go ahead and gap your plugs super tight at say .026-.028 and retest. See if it gets better.

I think its ignition related, caused by either battery, alternator (or combo of those two) Grounds, or terrible belt slippage at WOT.

To me it seems like the noids are staying open. Your AF was altered all the way to 6700 rpm like the noids are staying open. Seems ignition related to me.

98Z28CobraKiller

iTrader: (17)

My daily driver is an 2004 GTO. I have to check and see if the alternator is the same. If it is, I will swap it out to see if it makes the problem go away. I am going to buy one of those fancy Optima batteries just in case and it seems to be the battery of choice for performance aps. I am running all stock guage grounds. I will beef those up as well and return with more info.

I really do believe that the noids are closing. When they are wide open (peak power), you can see that my AFR is down around 10.9 or so. As the power trails off towards NA, the AFR goes up with it. Please note that the chart that I posted showing the Voltage was done will running NA. I spoke to some people at the track last night (didn't take the car) and was told that the noids draw a good bit of current so it is very possible that the 12V number that I am seeing at 6K could be at 5k while spraying and anything below 12V (as I move towards redline) is causing my noids to start closing. It is my understanding that this is the way a progressive controller works by restricting the voltage to the noids and slowly increasing it.

I will hopefully have more info in the next couple of days. Currently, I am in the middle of installing a tunnel mounted torque arm that is giving me fits of rage. I guess that I should have pulled my interior out before I started on this. Oh well. Can't complain as the Torque arm was a free hand me down.

383LQ4SS

iTrader: (33)

But the thing is...noids dont start closing. They are either closed completely....or open completely. In your scenario they would be open....until the voltage drops below the threshold and then they will simply close..all the way. It may be possible they flutter in very rare instances..but not likely.

BTW a progreessive controller will flutter the noids... or cycle them on/off rapidly just like a fuel injector.

But either way....fully investigate your electical issue and you will likley find the problem.

Bader-X

iTrader: (2)

hope you solve the problem .... I`m waiting to see what was wrong and if that dip of voltage @ 4k or 5k rpm goes ....

maybe you used 100-125 shot by mistake? the tourqe is good and the HP is down 25-40 hp maybe.

V-10 Killer

iTrader: (22)

Doesn't the alternator shut off at high rpms?
I'd agree that either the battery is getting weak, or you're overloading your ground points. Are you grounding all your solenoids at the same point?

98Z28CobraKiller

iTrader: (17)

Thanks for clearing up how the progressive controller works. I thought that they could be partially opened. Hmmmmmm.

98Z28CobraKiller

iTrader: (17)

definetly 150 shot. Where it is at 5K is correct, it should pull on that slope clear to 6600 RPM instead of falling off. I didn't mess with the electrical today as I was finishing the tunel mount TA.

98Z28CobraKiller

iTrader: (17)

Well, I been trying to figure out my problem still. I was convinced that it was a voltage problem after doing some scanning. I bought a yellow top Optima (Deep Cycle) and a brand new (not rebuilt) alternator and I still have the same voltage drop under full throttle and it is worse with the nitrous. I took off all of my grounds except the ones that are attached to the back of the heads and cleaned them and the contact surfaces with a wire brush. I checked the ones of the back of the heads and they are tight. The surface is clean as I just installed them in January. Would belt slip cause this problem? I don't have an underdrive pulley so stuff is spinning at full speed. Not sure what else it could possibly be.

Z284U2TRY

iTrader: (5)

I think your fuel is running out. That racetronics is good for what 600rw. a/f curve looks like it is leaning out whats the fp look like on spray? Are you pulling fuel from the rail?

98Z28CobraKiller

iTrader: (17)

Yes, pulling fuel from the stock rails. I don't have a fp gauge so I'm not sure. What does running out of fuel have to do with the voltage dropping? It has to have something to do with the ignition. I just can't peg it.

98Z28CobraKiller

iTrader: (17)

Gonna go buy a service manual and see if I missed any of the grounds. I can't believe that I am the only person on here that has had this problem. Damn this is sooooo frustrating.

rubbersidedown

nevermind- i read again...

98Z28CobraKiller

iTrader: (17)

Got it worked out. I think that it is normal for the voltage to drop under the heavy load. I have not verified it on another car. Perhaps someone could. Anyway, it was something very obvious. It was my plugs. When I originally put the motor together I had a different cam in there. That cam was installed a tooth out and I had some pretty severe detonation. I could have sworn that when I switched the cam I switched the plugs from the TR55i's to the TR6's. Well, apparently, I didnt. Soooooo we pulled a plug and saw a 57 gap with a severly pitted plug. It seems that I was blowing out the spark at 5300RPM on the nitrous and the reason that the fuel was leaning out rather than getting richer is that I wasn't burning the fuel, It was coming out raw thru the tail pipes and thus not reading on the wideband.

Thanks for the help. Now I need to get back on the dyno.

98Z28CobraKiller

iTrader: (17)

Well I got back on and made 504 corrected and 521 uncorrected rwhp today. I hit 638 rwhp and 625 rwtq on the 150 shot and an empty bottle (corrected). We had to put the Benz-o-matic to the bottle to get the pressure to 900psi. I'm pretty happy now!