what kind of math did you use to come up with this?

 

FWIW - at 28psi and 4 degrees timing, mine made 356 TQ. This was on a Dynomite Dyno which reads between a Dynojet and a Mustang. Keep in mind I had stock cams, and intercooler on pump. How much timing you running at peak tq with that much boost?

SQ

 

remember that the 28psi of boost goes around peak power only after that drops boost gradualy...... I have between 2 and 5 degrees..... in that area where the high boost hits...after that i have a little more...and the afr goes nice...all the way.
Today I couldn't post the chart because I'm still at the dyno and couldn't get home soon enough but tomorrow I will post the chart.

 

Well, your car likes more timing at such high boost than any I've tuned. 23-24psi on 93 usually knocks after 3-4* at peak load on the cars I've encountered. 25-26psi with 5-6* is just something I never see here.

 

Bat - to - PSI conversion with altitude correction:

http://www.dragsource.com/index.php?...s&calctoview=8

 

Timing numbers are just like dyno numbers, there's so many things affecting them, it's better not to get hung up on them.
Different cams, different exhaust, type of fuel, air temps and other things are going to make a difference as to what timing you can run.

People trivialize them too much: "I run 8* and you have 2*, therefore you and your car sucks a fat one!"

 

i punk all of you on timing on 91 and meth i run 24* peak timing and im not bsing either spiking 20psi holding 19ish at redline.

 

So you're able to run advanced timing on meth and low boost? That's impressive.

 

You need your posting privileges removed...

Conversation is about peak timing, which means peak torque timing. You run 24* by redline, not at peak tq.

 

Pre-ignition will melt a motor down in seconds, I've seen it happen when nitrous was involved (failed fuel solenoid), and it's not pretty. Check your plugs for early signs of pre-ignition. I would like to see the varying EGT temps of 21, 23, 25, and 28 psi. With the AFR / timing optimized for each boost level on a load bearing Dyno. I think 28psi is doable but I'm personally not ready to have that small of a margin of safety. I'm presently spiking 25psi tapering to 20psi on 93oct with my daily driver and thats about as far as I'm going to push the stock turbo / internals.


I found this here and it's good info so I'll post the applicable paragraph - http://www.sdsefi.com/meltdown.htm

Performance Considerations and Tuning Effects

On a given fuel, the maximum and mean cylinder pressures that can be achieved are limited to a certain figure. This is known as the knock limit. Trying to achieve cylinder pressures above the knock limit WILL destroy the engine. At wide open throttle, cylinder pressures can be altered by changing boost pressure and ignition timing. If the knock limit on a given fuel occurs at 700 psi PCP (Peak Cylinder Pressure), this limit could be achieved by using 5 psi of boost with the timing set at 30 degrees BTDC (Before Top Dead Center) or at 12 psi with the timing at 15 degrees BTDC. The engine will be considerably more efficient running less boost and more timing and the thermal stresses will be reduced as well.

TE (Thermal efficiency) is affected by CR (compression ratio) and ignition timing. As the timing is retarded, PCP is developed later in the cycle. This allows more energy to be lost through conduction into the water jackets because the piston is further down the bore and the rod has a less advantageous angle on the crank pin to deliver force to the crankshaft. Retarded timing also raises the exhaust gas temperature considerably. This raises the thermal stress on the pistons, spark plugs, valves, exhaust system and turbocharger. In severe cases of retarded timing, the mixture is still burning when the exhaust valve opens. Because turbochargers are driven by the energy in the exhaust stream, high EGTs caused by retarded timing produce so much energy at the turbine that even a fully open wastegate cannot control the boost pressure. All in all, retarded timing is counterproductive to producing an efficient, durable, powerful engine."

 

From what I have seen on alot of Evo's on our dyno, as long as you keep an approx 8* advance or more over the rev range (3500 to 7500 or so), meaning the timing curve advances 8* or so from peak torque to the rev limiter, EGT's aren't much of an issue.

Of course not all the Evo's that come through our dyno have EGT's, but I always check the ones that do and I have one on my personal Evo that has seen eleventy billion hours of dyno time on lots of different setups and fuel.

I am very mindful of EGT's here in 91 octane California land, espically since we specialize in ecu-boost control here at the shop, which holds more boost through the midrange and up top compared to other boost control, and of course, we are timing and boost limited with our fuel octane.

The times I do see EGT's getting closer to danger territory up top is when the car is flow limited with more back pressure, but you are trying to shove in a bunch of boost up top. A stock Evo 9, with upgraded ecu-boost control comes to mind. If you try and hold a bunch of boost up top on these, the timing has to be so low that the EGT's start shooting through the roof up top. For that reason, you don't try and shove a bunch of boost down their throats.

Just my experience...

 

Thanks for sharing your experience. Good info.

 

Bryan - how much boost can a stock ix run safetly?

 

I usually tune them for 17-18psi at 7k, on 91 oct, at 10.9-11 AFR

Pretty much every stock 9 with upgraded ecu-boost has gained approx 3Xwhp/3Xwtq peak.

 

lol my masters in automotive engineering hangs on the wall in front of me and it says not a large drop but it's just simple Physics. pressure in a rubber hose=increase in volume...meets with decrease in pressure or what seems like a spike in boost. it's not as much as this man says it is but it does make since.. but im not knocking what you say i see great power out of evo's with the stock piping.