Back when my car had the stock manifolds and open stock catted Y-pipe with no mufflers, my car went 8.29 @ 89.67 mph with 275/40/17 Nitto drag radials on Corvette ZR1 wheels borrowed from some guy at the track. Tire pressure was 20 psi. I was hooking great with a 1.81 60'. I believe it was about 60 degrees that night about last month.

So last night I had a best ET of 8.49 and had a best trap of 88.76 mph. Worst ET was 8.64 and worst trap was 87.63 mph. This time, I have Pacesetter long tube headers and an open TSP ORY-pipe with no mufflers. I also had on stickier 255/50/16 BFG D/Rs on lighter 16" 3rd gen F-body wheels and only pulled a 2.01 60' at best. Tire pressure was also 20 psi. Car did seem boggy off the line...

Car weighs 3500 lbs with me in it.

I wonder what is wrong. Stock tune not liking my new bolt-ons? I was shooting for solid 90-91 mph traps with bolt-ons, especially these nicer headers and ORY-pipe. This is messed up... Any insight on what a potential problem would have been for my ETs to suck last night?

 

Sounds like a couple off things decreased your ets. One, without the muffler and open y pipe you lost some torque which slows down your 60 foot and ets. Second if your tires are larger in size (tall) this can decrease your 60's. Hope this helps.

 

My car ran a 13.4 at 104 with a 2.0 60ft when it was stock. After adding my Pacesetters, I ran slower than that for a long time with equivilant 60s. Maybe it was the hot weather, but I was hitting mid to high 13s left and right. The weather cooled and I went back a few times, running consistent 12.9s at 106 with a 1.9 60ft.

I do know that my car runs stupid rich since I've added the exhaust. It'd probably gain a tenth or two from a good tune. Make sure your o2s are in perfect working condition, as well as making sure your ignition system is all tight. Then agian, like Cliff said, you may be hooking TOO well.

 

I checked online and the original Nittos I used were 25.7" tall. The BFG DRs I had on yesterday were 26" tall. I remember putting up my Magnaflow Catback up for sale earlier this month or last month so I'm actually not sure if the past runs were done with mufflers or not. But you'd think that with the extra top end the headers would have given me last night would have made up for it up top and bumped my traps to at least 90-91 mph... And yet, I've been seeing people claiming over 20 rwhp/20 ft-lbs tq over the stock manifolds. Hmmm... I dunno. Unless density altitude was lower even if the temperature was lower in the 50s, maybe that could have played a role in slightly worse ETs, but still ok for bolt-ons...

 

When I put on these headers, I've been told to replace my stock upstream O2s with the C5 Corvette downstream O2 sensors so I wouldn't have to get an extension for my old O2s.

 

I think if you could of just equaled you best old sixty of 1.8 you would have ran a new best mph and et. Those tires should have worked I don't understand how you sixty got worse.

 

Sounds like your bogging a bit off the line, higher you psi helps with bogging.

 

How did you extend your o2s? I did mine the ghetto way by splicing the wires and extended them myself, but ended up having problems. I then bought 'Vette (Bosch #13111) replacements and they've worked flawlessly.

Legend on the street is that some people have made little no no gains by installing long tubes untill tuned. Hell, I only gained 2mph and that was with an improved 60ft and better weather. I think there's more left in mine with a decent tune.

 

Pull a plug or 2 and see if your car is running rich. I'm still betting your torque is down with out a muffler and a short exhaust.

 

Like BADHAWK51 said, somethings not right that your 60ft. was so much worse than before. I would at least try a mail order tune now that you have LTs.

 

I'd get a dnyo tune, sounds like the stock tune just didn't like the mods, sometimes this happens. My car seemed to work well after my header install with a stock tune, but this was my 2000 year car, may be different from your 98 computer. Even after my dyno tune my car picked up even more. before was 290 hp and 319 tq, after the tune was complete it was up to 305 hp and 334 tq. I'm sure your tune is off, jsu go to a good dyno shop, usually those are better then mail in tunes. If the guy is good that is.

Any SES codes on? sometimes headers mess with 02 readings

 

tune def.

 

DA difference between the nights? Could be part of it.

 

its all in the tune

 

your 60' got worse because you removed all of your low end torque! A fairly stock motor needs some backpresure and you have none. Thus your 60 sucks, and in the 1/8th you don't have time to make up for that with top end HP. Run a 1/4 or get a mufler. A converter will help alot because it will get you up in the rpms so you are making the same torque as before.

Other option is to add about 300 hp so the free flowing exaust is effective for your car.

 

Update: I finally got a personal best in super cold FL weather we've been having lately. 8.14 @ 90.12 mph, 1.78 60'.