Right, the title does not make much sense does it? Well thats what Im wondering about.

I Just put an SDJ header on on my 12A which already has a Holley and racingbeat intake manifold. I was thinking a 60 hp boost with these components, but its not much of a noticable gain over the stock exhaust lacking the muffler.

It has a 2.5" collector. So I put on a 2.5" straight pipe all the way back and drove it about 20 miles to my girlfriends, but mostly in traffic. I didnt get much chance to open it up (above 3000rpms is one of the loudest things Ive ever heard, in fact it easily drowns out my stereo at full blast which is quite loud.) I mostly shifted by 1500rpms and just barely tapping the gas.

For one stretch I let it go wide open throttle from about 2500 to about 4000rpms in 5th and it did not feel that much more powerful that my prior exhaust which was the stock manifold and cats, no muffler. (Cats did enough muffling)

I wouldnt say theres any actual loss... But I felt more of a power boost from my k&n filter than the sdj header so far.

So Im wondering what the deal is?

Im thinking that perhaps the header changes the powerband, so it doesnt make the full powergain till about 7000rpm? With out a muffler that would for sure deafen any surrounding life. I checked and there was a small leak from the header, where one of the bolts broke taking the stock manifold off, also there was a tiny leak between the collector, and pipe. But Idont thikn that could rob all the additional power, from that small of a leak

Ill put a thicker gasget between the collector and the header, and tune the carb a little, EZout the broken bolt, then see, but any one that knows anything Id like to hear!

 

SDJ headers are supposed to be a notch above Racing Beat! I have RB headers and I always feel the diffrence after the install. Well keep us posted on your results

 

It sounds like you've given a butt dyno test in the wrong half of the RPM range. Muffle it and see how it feels in the 4000 to 8000RPM range

 

Ill definately keep you posted, I should be getting a muffler very soon, and before with the stock cats and manifold, it didnt come to life below 3500rpms but after was

 

Yeah, if you were running it off the header, then that high-rpm power problem (power being shifted upwards) would be exacerbated.

 

Which header did you put on the car? There is more than one version with quite different tuning specs. I don't seem to remember a street version, is there one?

 

I found it on Ebay under sdj header, and all the description said was racing.

Well, I Bought a muffler at Schucks for $25. Its a raptor (Made by Flowtech) AND GODAMN THIS CAR HAULS *** NOW!!!!

The Header totally changed the powerband, and the engine doesnt start coming to life till about 3000rpm but at 4500 is when it fully awakens, and 4500 to 7500 in gear is like a split second. This set up must have taken off about 2 seconds of the 0-60mph time

Thats what my problem was, It was too loud to take above 4500, and that says a lot coming from a metalhead hahahh.

I looked around for a super80 Flowmaster muffler, And the only place I found one they wanted way to much but for the price Im definately happy with my Raptor, sounds nice too, has a nice growl at idle

 

Awesome! Good to hear some results with these parts, too.

 

No flowmasters!....go Borla xr-1 after the sdj with a magnaflow at the end.

 

Perhaps I should post this... I had the muffler at the tail end of the car, in fact it stuck out past the liscnese plate. I moved it about a foot from the header, and ran the straight pipe from there, and it seems like it lost a little power moving it closer... just slightly, not much.

 

placing your muffler the correct length from your engine will change things, but i think you should put the car on a dyno with these different parts to make any determinations.

 

wow, i never knew a muffler could do that??

 

i've never actually done it. Something a teacher i had at UTI taught me. Just an old time drag racer. A way to pick up horsepower in drag classes that rerquired a muffler. Same with a set of headers, or similar, something about when making tubular headers you leave them all very long down the car and then draw with a crawy down the side of the each primary tube. Where the crayon stops melting is suppoed to place the collector, or the muffler, and then the primarie's are supposed to collect a certain distance up from that. I don't remember exactly. Could be all myth. I've heard the muffler placement saying on several occassions.

 

Well, I moved the muffler back to the rear of the car again, and its MUCH BETTER than being closer to the header. Backfires way less, and more top end power. Im going to post this in a new topic as well...

My car all of a sudden seems to have dropped just about all oil pressure and squeels extremely loud and high pitched. The onnly thing I can compare the squeel to is a banshee. It is related to the engine rpms, and unfortunately is NOT the belt, alternater, water pump. I started it with the belt off for a few seconds, same noise... any help?

 

LOL

don't start it any more until you figure out why you lost oil pressure..dude thats fuct, that squealing noise is probably some dry component in your engine now

 

It makes sense that the muffler closer to the engine makes less power than farther back. It should. It's more of a restriction there. Remember that everything going through the muffler contributes to flow. This includes heat. Hotter air has molecules that are farther apart. This means that the same amount of air molecules takes up more space the hotter it is. As the exhaust travels farther back, it cools down as the exhaust heat dissipates through the pipes and effectively takes up less space.

 

Thats pretty technical. You wouldnt think that the molecules would make that big of a difference, being their so small and all... Couldnt be further from the truth theyre the basis of everything, and Im glad to have been able to felt the differance first hand. BIG improvement, not to mention better milage - averaging 20mpg - From now on, my mufflers stay at the back of the car! Infact moving the cats back further may be even more of an improvement (if I ever get any)

 

Is this thread for real?


-Ted

 

No, Not really, I was done with it a while ago...