How much header leak needed to ruin mileage?

[BJM]

I had my header crack fixed when I bought my car 3 years ago. I never liked the fact that everyone on this board says the stock headers are stainless and this guy denied it. He said it was normal carbon steel. Anyway I have always had crappy mileage and the header does not look bad but there is white powder residue along one side of his weld. I don't know if this is stuff blowing out or just weld residue.

How much of a leak is needed to throw things off? BTW I never hear it leaking out of there.

 

[blackbuick87]

Any leak will. Any loss of exhaust before the turbo will slow the spooling of the turbo, hurting off the line performance and top end. If you are not confident you can weld it right, Postons and ATR sells a replacement header for that side for around $250

 

[cmokem]

If it is in fact a carbon steel "aftermarket" header...the little things like rust and impurities will eventually take its toll on the turbo.

I see a bit of the "white" powdery stuff on mine from time to time...if it were exhaust..I would think it be more blackish..like the inside of the tailpipe than white.

Just my 02 worth

Bob

 

[BJM]

Its definitely the stock header, the car was mint original when I bought it. I am worried about what kind of filler rod the guy must have used when he welded it up. Like I say, I have always had poor mileage and the crack was welded up before I had ever even used a single tank of gas so I cannot do a before/after comparison.

What type of stainless steel is it anyway?

 

[cmokem]

Its prolly some kind of 400 series stainless I would guess..not a real good grade at any rate. As far as the filler rods go though...it is very hard to weld stainless with anything less than a stainless rod.....not saying it can't be done...but the welders at work throw a fit when they weld stainless..if the welding rod has impurities in it.

Beside the bad mileage is there any other symtoms, poor spool, noise, etc
What is the blms at cruise??

HTH's
Bob

 

[BJM]

I wish I had a straight answer for the BLM numbers. My cruise BLMs and idle BLMs were always higher than the WOT values. I am guessing this is because at high flow rates my leak (if tis real) would not count for much. My BLMs are now completely different since my stock MAF died and the translator settings can move the numbers around a lot. I found that my highest BLM was the WOT one at 158 when I set the MAF to the 3" LT1 setting. I now use the lean 3.5" LS1 setting and now the numbers are all less than 128.

I have to take off the oil pan this winter anyway, while I have the crossover off I will remove the manifold too.

 

[cmokem]

I found that my highest BLM was the WOT one at 158 when I set the MAF to the 3" LT1 setting.

What chip are you using...most chip burners lock the blm at 128 at wot.

Bob