I would hardly consider 5.6 psi to 9psi a HALF of a PSI boost spike as you stated. You are completely wrong, it only takes one millisecond to blow a motor and if you experience a bad boost spike for a second, it COULD damage the motor. EPHASIZE COULD...
The point I am trying to make is that is is easier to control big amounts of boost than it is to control small levels of boost. I personally have seen SEVERAL Z's with boost spike/creep issues. most likely due to the wastegates springs under or over sized.
What most people do not realize is that once a turbo spools up it basically is producing all the psi it will and the wastegate is controling how much of that boost is actually being kept and how much is being bled off..Hence forth the term wastegate.

 

greddy kits tend to spike about .5 psi around peak torque.

if your spiking from 5.6 - 9 psi then you did something wrong.

 

I seen on that the guy would occasionally spike to 13-14 psi.BAD...

 

yea... he did something wrong.

 

The good news is that most cars can handle alot more boost at lower rpms without detonating so a small spike is usually ok.If you are on the edge though then a 1/2 psi spike could kill your motor if it starts to detonate which would be dependant on boost levels,timing advance and octane of your fuel,etc........I know that a single 38mm Tial wastegate can handle 640 WHP if your boost is high enough

 

not sure who or what you are referring to..but i made 603rwhp corrected (540rwhp actual estimated)...ernie as well, sharif, charles, tim in TX....ummm...many more to come...what is the point..please specify

 

Not at all. We tune cars on the dyno all the time, and datalog the spike.....less than 1 second in duration, and his minimal effect on A/F ratios. And typically, the spike is occuring at much lower RPM, and much lower cylinder pressure zones. Therefore, the chance of engine damage is nill.

95% of the boost controllers on the market will never control boost with the level of precision you have in mind. There are always minor fluctuations during boost transitions.

 

ops...guess I was a little late with my reply.

 

I don't plan on running 9 psi all the time, very rarely actually but i just wanted to know that if i wanted too, i can fill my car up with 100 octane on the weekend and have a map set for 9psi are 100 octane, im thinking a properly tuned map for this should be fine, so i should expect 450whp? Good thing i still have my nitrous kit ( 9psi of boost + 100 octane, and a good tune, AND a 55 shot of nitrous? what do you guys think? )

 

Who ever said anything about boost spiking from 5.6psi to 9.5psi??? Sharif said that if you run a 5.6psi spring and CONTROL the boost up to 9psi then you could get a small spike to 9.5psi when you first stab the throttle. Hence the HALF OF A PSI.

I have NEVER heard of any Turbocharged 350Z that had a proper install having boost creep issues. In fact the more prevalant problem is guys not producing the peak boost that they should be.

 

Woah on the nitrous....that much cylinder pressure, plus the instant hit of NOS will be tough on a stock motor. I think you will find that 450whp is enough to destory nearly every car on the car.

 

Like Shariff said, if you add N20 to an already increased cylinder pressure and temps, you will most likely blow up on a stock block.This will start by most likely melting valves and throwing your rods into tiny pieces..Have fun..lol

 

What? Wastegate controls wheel speed not boost. The blowoff valve controls charged air. Please explain.

 

Both statements are bit incorrect.

The turbo isnt building and spinning at its peak or creating all the psi it will create.

Turbos dont produce PSI, they produce airflow. The airflow creates a positive pressure in the manifold, but the volume of air can change, even though pressure is constant. The wastegate is designed to route exhuast gas away from the turbine exhuast housing, once the preset boost level has been reached. Without a boost controller, the wastegate will begin to open as soon as positive manifold pressure is acheived. This is why a boost controlel improves turbo response, becuase it keeps the wastegate complete shut until the set point is reached.

The BOV vents air in between shifts, and does not regulate airflow or boost pressure.

 

Plenty of VQ30 guys have run nitrous on top of boost. In fact it's usually referred to as the "intercooler in a bottle". Nitrous works GREAT with boost because it helps significantly lower intake temps while adding a LOT more power with a minimal (if any) increase in cylinder pressures. Remember you're not adding MORE air with nitrous, you're making the air that's already there much richer in oxygen.

Neither you, nor anyone else on this forum knows what the power limits on the stock VQ35 motor are. We know that it's very picky about detonation, but we don't have a solid power number that VQs consistantly fail at. They are all over the board...from under 300whp N/A to over 400whp boosted.

BTW - nice job avoiding replying to my last post.

 

The cylinder pressure does increase with the nitrous...even though no additional air is being injected.

I guess this motor seems very sensative to a lot of things, and nitrous, IMHO, adds another level of uncertainty to the mix.

 

I think we're talking about two different things. When I think of cylinder pressure I think of the air and fuel being compressed. With nitrous you still have the same compression because no additional air is added, but when the mixture is ignited the force on the piston is greater.

I think more than sensitivity, we're seeing uncertainty of how the ECU actually works in this car and weither or not a piggyback can effectively "trick" the ECU while massive amounts of extra air and fuel are added to the mix.

 

[QUOTE=BriGuyMax]I think we're talking about two different things. When I think of cylinder pressure I think of the air and fuel being compressed. With nitrous you still have the same compression because no additional air is added, but when the mixture is ignited the force on the piston is greater.
QUOTE]

Cylinder pressure during combustion is defined as the pressure that is created during the power stroke. Anything that increases power will increase cylinder pressure.

I hear ya on the unknown variables. But that fact is, that the VQ motor isnt as strong as some other platforms, such as the Supra, Skyline, and others.

 

[QUOTE=Sharif@Forged]
Definitely true...as it shouldn't be expected to be as it's not boosted from the factory.

 

I guess i will have to hold off on the nitrous.... for a little while