Threw a code... found a leak

[RobbieNelson]

I threw a code yesterday. P0171... Long Term Fuel Trim(LTFT) lean I reset the code and finished off the evening. Today I do a bit of datalogging and find that my LTFT in general is acting a little "screwy". I figure I've got a vacumme/boost leak somewhere. I get to lookin and the intake side of my diverter valve is as loose as a drift car. Looks like I never even tightened it up after installing my boost controller. I tighten it up and go on a test run. The car seems to run much better. I was probably running lean and getting knock retard. Wish I would have know about the problem before the Upgrades track day. My slips are kinda useless to me now. Oh... well. When you mod, you'll have things like this come up.

[Feedman]

I guess I don't understand...

Since you are MAF equipped, how would a vacuum leak cause a lean condition?

The MAF is compensating for x amount of air by providing x amout of fuel.

That target a/f mixture isn't going to be reached b/c x amount of air isn't reaching the cylinders.

When combustion starts, there is going to be more fuel than air b/c of the "leak", which is rich....

Loss of power yes? But no knock should be detected...


That is my limited understanding, please correct me if I am wrong..just curious.

8)

[RobbieNelson]

I figure I've got a vacumme/boost leak somewhere. I get to lookin and the intake side of my diverter valve is as loose as a drift car. Looks like I never even tightened it up after installing my boost controller.

The leak was between the mass air sensor and the turbo. This area is always in a vacuum state when the car is running. Actually, I'm not sure about the pressure during a blow-off condition.

x air metered
y air leaking in
f(x) fuel delivered
x+y air entering the cylinders

[MnAiXsImMoA]

are saying you got and after market boost controller of you were just putting your old one back on and messed something up?

[RobbieNelson]

are saying you got and after market boost controller of you were just putting your old one back on and messed something up?

Hallman Pro RX manual boost controller

I'll post some pics later. I may even post some before and after datalogs. :D

[Feedman]

are saying you got and after market boost controller of you were just putting your old one back on and messed something up?

Hallman Pro RX manual boost controller

I'll post some pics later. I may even post some before and after datalogs. :D


Anyword on the "extra powaz"...

?

8)

[RobbieNelson]

Anyword on the "extra powaz"...

?

8)

The lines that go up past 30 are mass air flow. The other lines are calculated boost. The ECU on the EVO doesn't have a manifold pressure reading. However, you can calculate it based on air flow. The formula is as follows:

F=mass air flow in lb/min, P=pressure in psig

P=(((F/RPM)*388.4)-1)*14.7

Broken down by units:

F/RPM = (lb/min)/(rev/min) = (lb/min)*(min/rev) = lb/rev

at standard ambient temperature and perssure there are 1.168 kg/m^3 of dry air

1.168kg/m^3 * 2.20462lb/1kg * 1m^3/1000l = 0.002575 lb/l = 388.4 l/lb

so... (F/RPM)*388.4 = liters/engine revolution

Since my engine displaces 2 liters every 2 revolutions... 1liter/revolution would be 0psig.... 0liter/revolution would be -14.7psig... 2l/rev would be 14.7psig

so... P=(((F/RPM)*388.4)-1)*14.7

[MnAiXsImMoA]

you love math dont you :D

[narfdanarf]

that's close to 300 horse in a fairly efficient engine configuration. Good job robbie!

[RobbieNelson]

you love math dont you :D

After:
Trig
Algebra
Calculus I
Calculus II
Calculus III
Linear System and Signals
Linear Algebra
Differential Equations

... yeah, it's kinda in my blood. There's some physics in there too!

[RobbieNelson]

that's close to 300 horse in a fairly efficient engine configuration. Good job robbie!

Thanks for the words of encouragement!

[MnAiXsImMoA]

as long as you understand what you put up there than sweet maybe i will get it someday :P

[sweeteffx]

you love math dont you :D

After:
Trig
Algebra
Calculus I
Calculus II
Calculus III
Linear System and Signals
Linear Algebra
Differential Equations

... yeah, it's kinda in my blood. There's some physics in there too!


Yea, that's why he gets paid the "big bucks" so to speak. ha ha