I just had a pair of evom headers installed on my 997tt last week. The before and after difference are pretty noticeable while the boost comes on a bit quicker and harder under full throttle acceleration. My butt dyno wouldnt say it gained a whole lot of peak horsepower but i definitely felt the increase in torque from the lower rpms all the way up to 7k redline.

The more noticeable difference that i noticed is in the noise and sound factor as it whizzles (even sounds like i had an exhaust leak) a lot more all across the rpm range. Is this increased whizzling sound normal by swapping out the thicker gauge oem headers with these stainless steel thinner wall headers? The spooling of the turbos is very noticeable especially with an aftermarket exhaust system. I just hope this noise is not from any leakage from swapping in new headers... How can i distinguish the difference between header gasket leakage versus a possibly normal whizzling sound with these new headers?

Does anyone have any experience with my similar diagnosis above? Thanks!

Sam

 

Sam it is totally normal. With headers comes an increase in the turbos being much more audible.

 

we pretty much always use them on any 997TT or 996TT's with K24s and above to get rid of the lag.... On 997TT's we've noticed pretty much a 200rpms drop in lag...

 

Thx ALex. Are there noticeable difference in the sound level upon installation of these evo headers from oem ones?

 

I have more Turbo noise with mine also. Franly, I think it's a cool feature. I sometimes find myself nailing it in high gear just to hear the turbo sounds over the exhaust. Like a jet engine spinning up! I love it.

 

yea the spooling of the turbo at low rpms are very obvious on my tt. At first, i thought i had leakage on the header install but after testing both modes with getting consistant 15psi and 17psi, I dont think the whizzling sound is from any leakage.

 

I had the increased "whish" sound as well but when the exhaust was installed (It had not arrived at the same time the headers were installed) the sound retured to normal.

Having the headers installed first and then the Milltek(sp?) exhaust installed later clearly demonstrated the big increase in performance when both parts are installed - along with the software flash that was installed at same time the headers were installed.

I don't think the headers are worth it by themselves and you get the added turbo sound which I personally didn't care for. The exhaust is probably the better way to go if doing just one part of the exhaust system.

 

YEP YEP..i definitely have leaks on both my new EVO headers as I stuck my head and hand this morning under morning warmup as i heard and felt it. I will need to bring the car back to the shop and have them look into it. Does anyone know if we have to use any aftermarket sealant (cooper seals) along with the factory header gaskets? I wonder if i am loosing boost and increasing turbo lag by this leakage.

 

Who did the installation for you?

 

i would rather not disclose the name of the shop as they have done some great work on my cars in the past. I guess they skipped the beat this time around. Oh well, at least it is only a leak on the headers and not a blown motor! hahahaha I ordered new gaskets and will have this fixed by end of week. Just sucks that i've been driving the car around sounding like **** after the header install for the past 2 weeks. I cant wait to really feel the difference and hearing what it supposed to sound like when it is fixed..

 

Common to have to retorque the header bolts after a few hours, leaks are not unheard off, even on one piece flange designs!

 

Sam,
They say you can re-use the stock gaskets. My brother had a similar problem on his 996 with some aftermarket headers, turns out the headers themselves weren't true/flat on the motor side plange. Def check that when they pull them off with a straight edge, do that prior to overtorque-ing the bolts, they only take 25ft lbs and are easy to snap. No sealant should ever be used on headers, I've probably installed headers >100 times on various cars and never had to retighten a bolt. If it's leaking there is a problem with the gasket, the header, both, or a loose bolt( read not tightened as opposed to 23ft# instead of 25#). In short, the aftermarket headers are more likely the culprit than installer error IMO.
GL
C

 

I've had the opposite experience with header bolts. After a few heat cycles the metal expands, contracts. Don't rule it out just yet.

 

thx fellas. I am also going to use new cooper nuts 12mm instead of the 13mm oem ones. I should have this leak problem fixed by end of week. I cant wait to really get on this car now that stage 2&3 are complete. Should be a blast to drive this summer until new turbos and retune ecu goes on this fall. ahhahahahahaha

 

Yes, but not enough to cause a significant/audible leak imo.
Do yourself a favor and check the trueness of the header flange.