I just recently got my ECU+ and had the opportunity to log a few runs out at my local 1/8th mile drag strip. My 2005 EVO has a 3" TBE, K&N filter, Halman MBC, APS BOV, Zeitronix WB w/ Boost & EGT logging, and of course, the ECU+. I noticed a weird "spike" with the boost and would like to know if it's something I need to be concerned about.

My first 3rd gear pull through the 1/8th mile looked like this:
(I started logging way before I actually ran at the track- so that's why it starts in the 100's)

22.9 PSI (spike) at 139.76 seconds (5706 RPM) (Knock .98 v) (af 10.70:1)
21.2 PSI at 139.96 seconds
19.1 PSI at 143.2 seconds (7657 RPM) (Knock 1.29 v) (af 11.40:1)

So, I have a spike of 22.9 PSI and it drops down to my target boost (21-ish) literally 0.20 seconds later- then tapers off to 19.1 PSI at my shift point.

Is this 22.9 PSI spike for a fraction of a second that big a deal? You can see my AF is still pig rich and there is no real knock.

I decided to turn up the boost a bit for another run and this was my result:
24.7 PSI at 19.44 seconds (Knock 1.86 v) (af 10.70:1)
21.5 PSI at 19.60 seconds (Knock 1.56 v) (af 10.80:1)

Should I be very worried about that boost reading for that fraction of a second? (24.7 psi for .2 seconds bad?) Is my hallman MBC malfunctioning? Do EBC's have these spike issues?


Thanks

 

Well, i have no idea about knock voltages but if those voltages stand for knock, then yes you should be concerned. Most all boost contolers are known to spike, EBC usually are worse than MBCs. I see there that the af jumped durning the 1.29v knock and that doesn't look too good either (maybe you let off the throttle to return the A/F to the part throttle map, maybe some detonation or something. And then when you turn up the boost, you have 2 knocks if those voltages do stand for knock. If they do then you have to dial down your turn and MBC for now and figure out where you problem is. Knock is killer. Just a note, i'm no tuner, so please do not rely on this information, i'm just giving my opinion. Maybe in someone here on the board can explain these knock voltages and how severe they are they can shed some more light on this. I would suggest for now to run no more than 10.9A/F and to turn down the boost just so problems don't arise

 

From what I understand, the knock voltage is simply the voltage the knock sensor (i.e. microphone) is hearing. Just the act of driving around town and the noises associated with the motor running causes the voltage to increase- indicating a noisier condition. I've read on the forums that 2.5v or higher may indicate possible knock and even then it's not always true.

My timing seems to be advancing nice and smoothly regardless of the increased knock voltage and even during the boost spike. My EGT's weren't out of the norm either.

I read that 24 PSI is a horrible thing for the evo (with my setup)- that it's on the ragged edge of the efficiency of the stock turbo; the heat is starting to negate the hp gain from the boost; etc etc.. but I'm not trying to run 24 psi.. it just happens to 'peak' that way for .2 of a second and then it falls to my real targeted boost level of about 1-2 psi over stock on 93 octane.

Anybody else have some input on this?

-nix

 

I guess this means it's not a big deal...

 

you sould see a slit spike, then it will settle back down (if you want to be safe just turn it down a little); alteast with the hallman mbc. Can you log your timing? if your ecu is pulling timing that should also tell you if your car is seeing knock.

 

Timing seems to be advancing fine with no pull-back. I figured all the signs say I'm safe.. just.. I see posts saying that even a slight boost spike is the end of the world for your motor in the long run. I'm wondering if I should invest in a different brand boost controller- one that won't spike. If I pull back the boost on the MBC to lower the spike- then I won't be able to hit the boost level I want (1-2 psi over stock on 93 octane) and it will taper too much towards redline. I'd be better off using the factory boost controller.

 

no, your fine. They all taper off. Not only that, but knock on my motor (w/ cams) is @ about 1.88V

 

What do you guys think about this run.. I was tuning the car.. setting up my fuel and timing tables. I see "knock" spikes every time I shift. I think it's the transmission/tires/gears making a sound and causing the knock voltage to spike momentarily. So, that would be fake knock I take it. The car pulls incredibly. I didn't really get crazy in 1st and I shut it down just after hitting 4th gear.

Opinions? Comments? This is my first attempt at tuning a car.

BTW: 93 octane, roughly 65 degrees outside, 05' EVO w/ TBE, K&N, stock fuel pump, Halman MBC, APS bov. (and yeah.. ecu+ w/ zeitronix wb)

 

I set ecu+ to pull timing and add fuel at 2.5 if that helps you at all.

 

I've got ecu+ set to pull 2 deg of timing and 2 % fuel at 2.90 volts knock. My '05 seems to be noisy. Just shifting can cause lots of knock voltage.