How to do leak test PRE-TURBO

[mrQQ]

Hi,

my car is running lean at WOT. Lex told me to do full leak test. It is leak free past turbo, but how do I test it pre-turbo?

If I connect it to air filter place, then it will leak through maf o-ring, as it is not meant to hold boost?

[btstarcher]

It shouldn't leak past the O-ring. How lean are you at WOT? Are you sure it's not just the MAF calibration?

[Snip]

In another topic he states that it's lean by approximately 10%.
Could also be maf calibration instead of a leak?

[mrQQ]

Apparently, it doesn't leak at all while testing.

It COULD be MAF Calibration, but I took Lex's JBR 3" as a base, which is 20% over stock, and its still lean by 10%. Even Lex said that it doesn't look normal...

Jbr is 2.875" ID.. stock is 2.61811.. so it's exactly 20% larger cross section, and not 30%..

[Snip]

According to your numbers the JBR is approximately 10 % larger then stock.

100% = 2.618, that means 2.875 is 109.8%

So if lex's maf calibration is 20% more, then there you have your 10%
And according to your profile you have a cp-e cold air intake, so the maf calibration from cobb ots should be pretty close i think.
My cp-e xcel nano sri was pretty close with the cobb ots maf calibration.

I say you should redo the maf calibration

[mrQQ]

No, not like that. Cross section is radius squared, so:

2.875^2 / 2.618^2 ~= 1.2

So that's a 20% increase and that's exactly what I have my MAF cal at. But from the logs, it's still 9% too lean. There is no way that 3" JBR is flowing 29% more than stock MAF....

[Snip]

No, it's pi x diameter if you calculate it in another way, or pi x radius squared i believe.

Then it's (3.14 x 2.875) / (3.14 x 2.618) = 1.098 so roughly 10% increase.

[Ranyard]

Originally Posted by Snip No, it's pi x diameter if you calculate it in another way, or pi x radius squared i believe. Then it's (3.14 x 2.875) / (3.14 x 2.618) = 1.098 so roughly 10% increase.

Pi X Diameter or Pi2r is circumference, Pi X r^2 is area, or cross section. totally different things.

[Snip]

I agree Ranyard, i had the formula wrong. I stand corrected.

But area is also 1/4pi x diameter.

Then i still get roughly 10 % of increase

(0.25 x 3.14 x 2.875) / (0.25 x 3.14 x 2.618) = 1.098

Where am I missing the point then? :-)

[mrQQ]

no, still the same pi and 1/2 cancel each other so all that remains is r1^2 / r2^2 which is 20%..

[Snip]

but let's say you have 2.618 and you want to go to 2.875.

if you take 10% from 2.618 = 0.2618

add that to 2.618 = 2.8798 which is roughly what you want.

Adding 20% is 2.618 + 0.5236 = 3.1416 is not what you want.

I'm getting a bit confused now because i don't see what i'm doing wrong, because the formula with pi x r2 indeed gives 20% increase, but the other formula (1/4 x pi x diameter) gives 10%, and adding 10% to 2.618 also comes closest to 2.875, instead of adding 20%...

[mrQQ]

You are forgetting the square. Formula is pi x r squared.

[Snip]

Indeed,

again i stand corrected, the other formula i forgot the squared, it's 1/4 x pi x diameter^2

then you will also get 20% increase.

Sorry for disturbing your topic guys

But ontopic;

Since you can't find a leak, what is the smallest inner diameter of your cp-e intake? is that the same diameter then the JBR?
Otherwise it may be off there?