Still not got a tune on my car. I have advanced my timing to adjust for poor throttle response, poor low end power, and hesitency/stumbling.

I have found that with the advanced timing, I cannot boost over 5-6psi in first gear. I have adjusted everything I can think of on my AVC-r but cannot get it above 6 psi. However, without making any further adjustments to my AVC-r, I had decreased my timing and ran the car. It again had the same issues as before, but found I was able to now boost to the setting on the AVC-r which was about 8-9 psi.

What would my timing have to do with boost pressure?

 

Do you have a detonation sensor varies boost? If you're running too much timing and the computer senses detonation, its possible it could lower your boost pressure as an added safety net.

Nice Z31 BTW.

 

I would put the timing back to stock if you can especially since you are boosted. It seems like there are regular issues with the car that need to be fixed before a dyno tune, if it is stumbling, etc we have to figure out what is causing it. Here is a post about the emanage ignition harness but has some timing information.
http://forums.maxima.org/3580695-post13.html

 

I do have a knock sensor, but the ecu has no say in my boost pressure. My AVC-r electronic boost controller has no knock sensor as a part of the system. I had originally thought what you suggest was the issue. But, it doesn't seem to fit for me.

If the ecu is retarding timing when I have it manually advanced, then it should retard it to about what I had detuned it to when I was getting higher boost. When I manually retard my timing, I see higher boost but it runs like crap and has less power throughout the entire power band.

What role does timing play in exhaust output, velocity, and pressure? At the moment, I am assuming I am running rich and advancing my timing is allowing the engine to burn up the fuel properly. This is why I'm losing power with retarded timing. But, if I am burning up all the fuel with greater timing, then wouldn't the increased power help push/accelerate exhuast through the turbo therefore increasing boost response and ability to spool up? The delima is this scenerio does not play out. Furthermore, it is only an issue in first gear.

I had also thought at one point that this was a problem with my AVC, but once I decreased timing and saw greater boost, I knew something was up. I appreciate the input and feedback!

 

I'll read up right now. But I'd rather have the timing advanced so that it is drivable and not be able to see higher boost than have poor drivability and higher boost. I honestly associate the stumbing and poor drivability to the tune on the car....which is simply something I downloaded. I don't know where to even start tuning the car myself!

 

Read post. Makes sense. Doesn't answer exhuast question or why you recommend avoiding dyno.

I've been making things better on the car over the last year or so. Such as intercooling, installing aluminum piping and T-clamps, electronic vacuum pump as well as a Walbro fuel pump. I am currently repairing an exhuast manifold leak off the right bank. I do wonder how much this plays a role in my boost pressure. But, again, this is primarily an issue in first gear. Regardless of leak, why would retarding timing allow me to boost higher in first gear?

The other thing I know I need to change, is that after I installed my intercooler, I redid my intake piping off the manifold which did away with my port at the throttle body which ran to my solenoid valve operating my internal wastegate. It is presently connected to the port on the turbo compressor side. I will be welding another port off the throttle body piping to run my solenoid.

 

Advancing the ignition timing ignites the mixture in the combustion earlier in the piston stroke, allowing for a more complete burn before the exhaust valve opens. Retarded ignition ignites the combustion later in the stoke, allowing some of the still burning mixture to exit out the exhaust valve. This results in higher EGTs and more energy to spool the turbo.

 

I buy that. I absolutely believe I have high EGT's. Thanks!

I think this is exactly why I've blown several exhuast manifold gaskets off the right bank. It is currently disassembled and will be utilizing the copper exhaust gasket spray when re-installing the manifold and crossover gaskets. I've talked to several boosted guys who say this stuff really works and is a must for high performance and turbo applications. I replaced some of my manifold wrap and found that the thin rust layer had "shed" off under the wrap (flaked off). I assume this happens only under high manifold temps. Beneath the flakes, the manifold looks shiny, smooth, and new.

Did you guys know they make copper gaskets for a 240 and Sentra but not a 300z? A SENTRA!? Good greif.

I'm going to lower my boost settings (not try to attain high boost) and install a larger exhuast pipe.