What's this dip in my graph from?
 

Cam only car. Moser 12 w 4.11's. 175 wet kit.
2000 Camaro SS 6spd. LS1

I originally thought that dip in my graph was from it sucking the rails dry so I went ahead and installed new rails on the car. Is this possible? I haven't had a chance to redyno since the last time.


Attachment 728074

using a sniffer really kills the reading at the exact rpm but for reference look at the start of the run and you'll see that the wideband is ~500rpm delayed. So the AFR @5200 will actually show up ~5700. Rich and either knock sensors pulling timing or it was breaking up from excess fuel would be my guess but it's hard to speculate without seeing a datalog.

The whole tune up looks rich to me and the NA tune needs some work IMO as well. Looks like its fat in a few spots as well and doesn't match the torque curve very well.

Based on your cam only statement I have to ask if your still running the Stock injectors (99-00 had the smaller 26# injectors)? Both your runs on N/A and Spray show the issue I had with a small Dry shot on Stock injectors with AFR going up in the upper RPM's...

Logging the fuel pressure and IDC will clarify your issues.

You can see I was running out of injector with a fairly modest Dry shot...

http://www.retrorelics.net/jim/Board...ingDry32x2.jpg

I am still on the stock injectors. Installing the injectors wouldn't be a problem for me... how hard would it be to get the car running after I installed them? I have HP tuners.

With HP tuners or EFI Live all you have to do is swap out the injector parameters to the new injectors, then flash the tune to the PCM. Its pretty easy.

I would use HP tuners to log your injector duty cycle and verify the issue.

You can also set up a PID for Fuel pressure and add that to logging by adding a gauge to the rails.

Injectors arent the issue here.... NA fueling is perfectly fine and actually needs leaned out in some spots but comes back right at the end of the pull where it needs to be.

Being a wet kit the nitrous on his setup isn't causing anymore load on the injectors. If he is still running a MAF it will actually reduce injector duty cycle a fuzz because the nitrous/fuel displaces some of the airflow that could normally flow through the intake. This will show with lower MAF Hz readings on the jug compared to off the jug. It's very minimal but if you pay close attension it's there.

To fix this setup you first need to get the NA tune dialed in. Then work on your nitrous fueling with conservative timing. On a 175 shot shoot for ~15* to start off with to get fueling dialed in then creep up on timing until the plugs start showing some heat and verify fueling on each timing adjustment. Don't target turbo like AFR/Lambda... no need in all that richness on a nitrous car! NA fueling is desired and use less timing to keep excess heat out of the chamber. Rich and more timing hurts parts and runs slower.

Speaking of plugs... what plugs were you using on the nitrous hit?

I was using tr6's as this was the go to plug a few years ago on here. The card been sitting for three years and I just recently got it going again so I haven't sprayed it yet. However I bought some br7s that I'm putting in the car before the spray.

I would use a ngk 4554 on that setup.

Pump gas?

93. I'll be mixing in a few gallons of 100 unleaded when I spray in the future.

Boryke has stock heads, so he may need tapered seat plugs. I'm unsure if those Ngk 4554 gasket seat plugs would work or not.

i had semilar dip on my set up, but mine was much worse

can you post a full detail on your set up

i may able to help you,

Forged 347. Diamond Pistons lunati rods, blocked decked .010

I was on the stock fuel rails during these runs, but I've since upgraded. I have a racetronix fuel pump kit with a 255 warlboro

FM14 Cam, stock heads.

Nitrous kit is a harris speed works sudden impact kit with their larget solenoids. Microedge windowswitch and controller.

do you have stock fuel pump? just curious as I'm including that upgrade first in my build up to ported 243's and Fast 102/102. I've been told by builder to upgrade fuel pump first, then maybe injectors but we'd find out real quick.

All of the oem gm cathedral port heads I've come across can run either setup just fine. There is a flat pad just before the taper seat that the gasket will seat against. Plug protrusion is still similar as well because the gasket seat plugs are .750" reach where taper seats are only .706-.708" reach. The gasket takes up the slack there. I convert alot of power adder guys to gasket to aid in a better plug seal. The little details add up.

James hit it perfect, its just rich take some fuel away from it and try again, rails, pump, injectors are not an issue here. Its rich

I didn't know for sure, so thanks for the info. :thumb:
Jet charts are usually set up on the rich side from alot of companies, along with the rwhp rating different as well. What size jets do you have in the plate?

The graph alone isn't much to go on but if I had to guess from past experiences, I'd say the dip is a result of knock and the pcm pulled timing. Based on your a/f even na I'd say your tune needs some work.