So after I put a 2 1/2" catback I lost .2 seconds on my 1/8th mile time..
My best run had been a 10.0 with y-pipe and CAI. I put an underdrive pulley, short ram intake and a catback and lost two tens.. wtf? after talking to some people around here they all agree i probably dont have enough back pressure so i'm losing some power.. this really bites.. i'm going to try to find a cheap 5th gen muffler for some added back pressure and leave the excisting pipes

 

yeh the bigger pipes usually benefit forced induction better, even though your top end will benefit from this.

 

Your friends dont know what they're talking about. Back pressure is not what loses power, its exhaust velocity as i have learned. Look elsewhere for your problem. Maybe knock sensor/maf/coils/plugs.

 

What were the conditions?

What was the DA on both runs?

 

can you post the full time slips from both runs....its hard to say anything just based on your e.t.'s

 

Back preasure is not your problem, if you still have your cat in your lots of back preasure. I agree that your time loss is most likely condition related. It does not sound like a big deal if you go to the track every weekend for the next month and still see slower times then you might want to think about changeing things.

 

If you dont have forced induction or any serious engine mods I suggest you swap your 2.5" B-pipe for a 2.25", that should give you all the back pressure you could ever need.

 

Quoted for the truth, before i read some things i always thought you needed back pressure for N/A cars.

 

Do NOT listen to this post

 

If you had a full cai and went to short ram thats your main problem

 

Do the maintenance on the car. Do you know how old your y-pipe is. I have seen one case where an org member was slower on times and couldn't figure it out until he removed his y-pipe. The flex section was collapsing in. This was resolved by putting in a new flex section.

 

As stated above ... you switched to a short ram. BIG mistake. Both have their flaws, but a short ram benefits low and hurts top. CAI benefits top and hurts a little low.

 

You could easily just have had a worse launch or reaction time this time around. Definatley post the slips, you could also just be getting used to your mods, give it some time it'll slip under your personal best probably.

Also look at maintenance stuff and also track conditions could've been worse than last time.

 

You gotta be kidding me. To keep 2.25" tubing he might as well just put the stock tubing back on. You want back pressure, stick a big potato up the car's muffler, THAT will give you "all the back pressure you could ever need" lol

Phenryiv1, I think we need to have a sticky here that compares and contrast back pressure and exhaust velocity, because there is ALOT of missinformed people out there that dont know the difference between the two and try BS advice/ opinions because of it., you know what? I'll make one right now, Im sick of this, lol.

 

oh and to the OG poster, please give the full details of the runs from before and after, not enough info being provided right now to make a certain determination.

 

Oh it sounds like u put all those mods in at the same time. Not sure but maybe u need to let your ECU cope with the changes first. And ya, if thats not the case, check your sparks, coils and knock sensoe before you do anything major with your exhaust setup...

 

Actually its the other way around... CAI hurts top end cause of its longer tubing...

 

you speak truff

 

Regardless if his 60' times aren't the exactly same then his concern is pointless.

 

do you have the slips man ? need to see your 60 foots on both runs and compare temps.

 

http://forums.maxima.org/showthread....16#post5569616

as promised

 

Aight, so I cant find the slip for the 10.0 run but I'm pretty sure I have the one from the 10.2 run. Heres what I had done on the 10.0 run: (Note, everything I have on the car is brand new and I installed it myself) CAI, Y-pipe, headers, 225/50r16 tires.

This is for the 10.2 run: Same tires, I changed the intake to a short ram instead of the cold air, and i installed an underdrive racing pulley, and i added the 2 1/2" cat back.

Now, that night at the track was conciderably warmer and more humid (being florida) than the 10.0 run. I ran again this last thursday (a week later) and didn't even come close to that. I think I ran another 10.2, but that was my best run. I ran mostly 10.4s and 10.3s. I'll put some pics of the time slips up in a sec. I have a lot of them, but not all of them so i'll post what i have.

 

http://pic17.picturetrail.com/VOL812.../236974854.jpg

 

http://pic17.picturetrail.com/VOL812.../236976290.jpg