Thanks ... yeah, I realized that today while I was on the road ... I was thinking, "Wait ... 1.5 bar is ~22 psi ... I'm gonna get reamed for messing that one up." Thanks for the correction though.

 

i run 25 psi spike on my car but it tapers off a lot at redline i am using a halman mbc

 

The key here is that everyone is assuming that the 96 octane gasoline sold in the Phillipines, the 98 octane gasoline sold in the pumps in Korea and the 91 octane gasoline marketed in the U.S.A. are all rated using the same standard, when in fact they are not.

In Japan and most countries in Asia gasoline is rated according to its Research Octane Number(R.O.N.). To make a long story short, 98 octane(RON) gasoline is equivalent to the 91 Octane R+M/2 grade gasoline sold in the U.S. They have identical knock resistance. They are just rated differently but(again) their knock resistance is identical.

Thus, my Evo VIII purchased new through a dealer in Honduras, Central America has a factory sticker inside the gas fill door stating that only 98 Octane R.O.N. gasoline be used. But, 98 Octane R.O.N. gasoline has the same knock resistance as 91 Octane (R+M/2).

So, tread carefully when raising the boost level on your EVO.

 

the best way to know what is safe is have it tuned. i guess u r using petron blaze. when i was there i have tried caltex(texaco here), shell, petron and most know racers there uses petron for their pump gas. based on my research when i was there 95ron in the phil is more or less 93 oct here in the US. first off if your car only has tbe better put back the stock boost levels and start tuning from there.

 

Using an AFC is going to mess things up. Leaning out your fuel curve is going to increase the timing some.

You can run as much boost as your car will allow you to until it knocks. There is no set number. Mods, tune, driving habits, quality of gas all plays a part of this.

Lot of bad info in this thread. Get a logger and see what the car is doing.

 

you can boost until you get knock right? or become too lean?


I'm not sure, thats why I trust my tuner...........

 

Dennis ... come on. That's not very good advice.

Knock isn't the only thing limiting boost. You have to consider things like the compressor's efficiency range and of course how well the head studs will hold. You can try to trade more boost for lower timing and get away with a little more power, but do it too much and you'll see high EGTs and greater possibility of failure.

I'm not sure why you are mentioning AFR's and advanced timing, though you are partially correct. Leaner AFRs don't technically increase timing advance since the spark still fires at the same time. You will reach peak cylinder pressure a little earlier with leaner AFRs with is the same effect as increasing ignition advance.

And yes LayinLo .. trust your tuner. I have a feeling he's a really good guy.

You can technically boost till you get knock, but it's not really safe. You need to be wary of high EGTs and possibilities of lifting the head with excess cylinder pressure. A more efficient oil and coolant system will help you run a little more boost safely ... so will upgraded head studs that don't stretch.

 

Even a maxxed out turbo can run the stock headstuds fine. Most people see 21psi by redline this is fine for stock studs.

EGT's are a horrible way to tune. Most gauges are slow and inconsistent. The compressor's efficiency range, come on, how many modded evo's are still in that range?

Leaning out with an afc changes the airflow map and you can drop down on a timing table. Lower airflow = more timing. Only reason I mentioned af ratio is because the afc messes everything up.

Tune till you knock, then back it down a little for a safe margin. Knock happens for the most part during peak cylinder pressure. If your not knocking, your making power regardless of cylinder pressure.

 

Nice Ovenmitt!..Exactly!

 

You are forgetting that the stock turbo only "maxes out" at 21 psi in the high RPM range. You can run upward of 30 psi on the stock turbo in the 4000 RPM range. That kind of boost will break something if you don't have the right setup.

I didn't say tune by EGTs ... I said be aware that high boost raises EGT. When EGTs get high the changes for detonation and pre-ignition are higher. Also, the extra heat can weaken engine components over time. AFR is better to tune by in my opinion as well, but EGT should never be completely ignored.

I see what you are saying now. You are absolutely correct in regards to the AFC.

Yes, tune till you see knock ... but I recommend tuning till you see knock with timing and not boost. Choose a safe boost level and then tune timing from there. If your boost level requires negative timing to avoid knock, you are likely running too much boost.

 

This is what i always have heard from respectable tuners. That said I would take consideration with what people commonly do but do not take it as set in stone. Every car is different and everyone has different variables (octanes of gas available, altitude, ect.). Start at a conservative boost level and see if you can push it, CAREFULLY. Make sure you are monitoring the correct information, knock, AFRs, EGTs and just be conservative about it. Personally where I live (pretty much at sea level with 93 at every station) I plan on getting tuned for 24psi if not more depending on what my tuner and I feel is safe.

 

Boost level without knock depends on octane, air temp, and exhaust pressure. Knock depends on temperature and pressure of the air and fuel.
HP depends on the density of the mix, how fast it burns, and where the peak pressure hits (about 20*). With all the stuff above in mind, in addition to ignition lag, spark, cam timing, and swirl, you adjust the timing to get the most powerful bang at 20* and there you go. So who cares about how much boost because flow is more significant. I like cheese

 

[quote=TouringBubble;5142278]Dennis ... come on. That's not very good advice.

Knock isn't the only thing limiting boost. You have to consider things like the compressor's efficiency range and of course how well the head studs will hold. You can try to trade more boost for lower timing and get away with a little more power, but do it too much and you'll see high EGTs and greater possibility of failure.

I'm not sure why you are mentioning AFR's and advanced timing, though you are partially correct. Leaner AFRs don't technically increase timing advance since the spark still fires at the same time. You will reach peak cylinder pressure a little earlier with leaner AFRs with is the same effect as increasing ignition advance.
leaning the apexi afc will add timing that`s a fact. when you lean the afc it changes the value from the maf sensor to lean it. so the ecu thinks you are partial throtle when you are actally full trhotle so the ecu uses a more agressive timing map. see an article from RRE of an evo 8 mr they explain it better than me for sure. they used larger injectors to add more timing with a afc. the article tittle was caveman tuning or something like that. evo 7 use 20-21 psi and no problem. i use 21psi with stock headstuds for 40k kilometers and had no issue.
fuel. i think were you live you got 95 oct RON research octane number that is pon + mon /2. 93 is the us is PON pump octane number . 97oct ron is like us 93 oct pon more or less.
hope i helped a bit good luck on the car