Hey people

Anyone here know how much hp they have gained on their Evo 9's by just leaning out the AFR and adding a few degrees on the timing map?

 

There really isn't much reason to tune without increasing the boost, but I'd guess there is about 20 hp to gain from only timing and fuel tweaks.

 

around 10-15whp:

 

I don't know about evo 9's but I picked up more power by adding timing than boost. If I tune to the edge at 20 psi and about 14 degrees of timing up top the car is noticably faster than if I tune for say, 23 psi and 9 degrees of timing up top, which seem to be the timing numbers that my motor starts seeing knock at. I would rather be able to tell people im on 20 pounds than 23 as well.

 

You are right. It comes down to what the motor and fuel can handle before knock becomes a factor. Ideally, you want more boost, more advance, and leaner fuel.

You will make the most power with peak cylinder pressure at 15* ATDC. If you can reach that point, the more boost you have, the better. However, most of us on pump gas will never actually hit that 15* spot.

 

If he wants to race in the SCCA AS or STU class he cant raise the boost, so tuning for just timing and A/F ratios are critical.

Marc

 

You are correct ... in ST classes you can't change boost levels. However, in S classes you can't tune the ECU at all ... He might be aiming for STU. I think you are right.

 

Touring,
Lets be honest though...how many of those STis and EVOs in STU are running stock boost. Well, ok, I'm sure most are, but...Its kinda hard to prove they are not. $hit, some might even have semi bored out cats. They can hide $hit good now a days.

I was talking with my favorite speed shop yesterday and they were even giving me hints on how to cheat. I refuse to cheat unless I feel I am losing because of cheaters. At that point I will call the shop and get a custom tune with RAISED BOOST, and a bored out high flow cat.

 

I feel the same way ... I hear a couple of specific STU STi's fly by while I'm working the course and you can hear that something is up.

I've been in a few debates about boost control in BSP on my regional forums. Many people claim that manual boost control is illegal in SP classes and I say it's not according to the '07 rules. Either way, I did the research to make sure I was legal and not to stretch the rules in my favor. I'm using the ECU to control boost ... it doesn't matter to me.

I got a few comments saying "no one checks anyway" and I didn't like that. What's the use in winning if you know you're cheating?

 

I fully agree with this comment, yet if the cheaters make it so hard for me to win because of their 25 psi EVOs & STis.....then you know the rest.

 

I hit 14 degrees peak on 20 psi. Close enough for me.

 

The logged ignition timing is not the same as the point where cylinder pressure is the highest. There are lots of factors .. engine speed, spark timing, plug gap, fuel used and flame front propogation. You can't really measure when peak cylinder pressure occurs using the basic tools we have.

Just as a side note, your 14* timing advance means 14* before TDC ... you want peak pressure 15* after TDC. Advanced timing makes power by creating peak torque earlier and therefore closer to that 15* sweet spot. A leaner mix speeds the fuel burn and can also make the cylinder pressure peak sooner.

The slower the motor turns the less advance you need because the crank is moving slower but all other variables are unaffected. If you're tuning nearly to the knock threshold at every RPM interval, you are likely at peak cylinder pressure at similar times on the combustion stroke, even with more advanced timing up top. the spark timing is basically chasing the piston if that makes sense ...

 

It does make sense, thanks for taking the time to explain that to me.

 

the reason why you guys aren't seeing any more power when adding more boost than 20psi is because the IX turbo is hitting its efficiency level at about 19-20psi (at redline) .. so after that its just blowing hot air

 

Tephra, you're right. My method is sort of riding the compressor map ... use the big boost when you can (down low) and taper it down when heat becomes a problem. My boost curve constantly tapers from 26 at peak (3300) to 19 at 7400 or so.

Karta, you're welcome. I try to help when I can. You are correct in saying that you make more power with less boost ... it's completely possible and logical. With lower boost you are less likely to encounter knock and can therefore get that peak pressure where you want it.