No here's the problem. You're talking about LT1s and were talking about LS1s.
You've started this huge todo because you didn't get 20 hp on your LT1 and I would bet money that any stock LS1 would get 20 or more from Long tubes with a good catback.

 

Moving the O2's further downstream throws off the computers calibration and makes it think you are running too lean. You really aren't running too lean, but the computer thinks so, and dumps in more fuel. This is why(in laymens terms) you need to tell the computer that the A/F ratio isn't lean, so it doesn't have to dump in so much fuel. This is the prime reason you need a tune after longtubes. This is why people make nice gains with a tune after doing longtubes. And to 95firehawk: One of the best reasons for getting longtubes is for low rpm torque production. You lengthen your primaries to enhance torque production and increase the scavenging effect. The mac mid-length headers show close to the same peak hp gains as longtubes, but less power below 4,000 rpm. This is because of the longer primaries and their ability to enhance low end torque production. Your kind of gains could be seen with big 1 7/8 primaries on a STOCK car that's untuned. Otherwise 1 3/4 longtubes are without a doubt good for 20+RWHP. Why do you think they are so popular? It isn't just because they look cool. You will see bolt on cars with longtubes dyno 350rwhp, but how many with stock exhaust manifolds dyno that??? A real strong one might dyno 320-330 rwhp, if they are lucky. Hmmmmmm 20rwhp less!

 

AL SS590 M6 ~ LS1 cars arent the only ones that respond to bolt-ons well. Its pretty much the norm to gain over 20RWHP with long tubes. He just seems to be the freak incident.

Black9TA8 ~ 99% of the guys on the LT1 forum are installing long tubes WITHOUT a tune and still seeing 20+RWHP gains, same conditions for heat humidity etc. You DO NOT need a tune for headers. And my fuel mileage went up for sure around 2 mpg city driving after a long tube install without a tune. Bottom line is your wrong. Anyone that has installed long tubes and lost power has something wrong with their car. It does not make it run so rich that they loose power.

The real reason there is power behind a tune, especially with headers:

LT1 & LS1 cars run rich from the factory. In power enrichment mode (Close to full throttle, to WOT), the computer takes a reading from the TPS and injects a significantly lengthens the injector pulse widths. They can commonly run as rich as 10.5 to 1 at WOT. Ideal would be in the 13ish area. When you get a tune for an LT1/LS1 car that is stock/minor bolt ons, nearly all the increased power comes from leaning the mixture out. The more modified the vehicle is, the bigger the gains it will show. Therefore, a mail order tune before headers may give you 5-10 RWHP, a mail order tune after headers, cai, catback, etc could show potentially more.

If you are debating on whether to get headers or not, get them. And dont listen to Black9TA8 about needing a tune.Almost every person who gained 20RWHP DEFINATLY didnt have a tune. Every other person I have ever seen both in person, on the board, or at the local speed shops, have all shown very decent gains with headers and no tunes, and slightly better with a tune. You will not loose performance with long tubes, and as long as your car is running well ( New plugs wires filters etc) you absolutly will see nice gains. At least 15 RWHP with long tubes. Actually I would be sort of dissapointing if I only gained 15. Wait until you are done with all your bolt ons to get a tune. Its absolutly retarded to spend 100$ for a mail order tune every time you buy a new bolt on for your car. What are you gaining? Id like to see before and after dyno results with a new part with a tune, after the computer has been given time to "learn" and adjust the mixture on its own.

As for 95firehawk:

You either burned a plug wire, or are getting flase knock. Its common to loose some low end torque, say 10 lbs, but only under 2500RPM's. There is something wrong with your car if your not seeing gains pretty much from 2500RPM up in both torque and horsepower. O wait, maybe you need a tune to make any gain with them headers ...

As far as that goes, heres something to think about ... The oxygen sensors measure sense oxygen, moving them 12 inches isnt going to change the exhaust content when its in a sealed header And before you even say it, the resistance in the extra wiring of the O2 connectors would, if any difference, cause it to lean out even more. And if our cars (LT1 and LS1) run lean from the factory at WOT, then once you are free-er flowing with headers, lid, etc, wouldnt it slowly be leaning itself out as its getting more air in, but, according to you, not accomodating for fuel? That would put us closer to the ideal AF mixture. Making even more power. Bottom line, you DONT need a tune. It helps, but your car is NOT going to get bad mileage, horrible driveabilty, or loose horsepower off of headers or other bolt ons without a tune.

 

Trust me on the tune thing. Have you aver datalogged a car after longtubes? I'm not saying some cars don't see gains with longtubes untuned. And yes you can run your car untuned with longtubes. Your car runs rich from the factory, and will even run richer with the relocated O2's. Datalog pre and post LT's and see what happens. You get your car tuned and re-calibrate the computer for the new O2 location, and you will see good gains. How come you guys can't understand this? You can also put a cam in your car and run on the stock tune, but you will run rich down low and lean up top no matter how long you give your car to compensate. Your air/fuel ratio must be dialed in if you want to run right. And HardcoreRM 125, it isn't that your computer can't compensate for the header, it's that it doesn't know how, because it's basing it's adjustments for a car with the stock O2 location. Of course the computers can compensate somewhat for mods, but it needs known parameters. Moving your O2's downstream throws this right out the window. It's the same reason you can't just throw bigger fuel injectors in your car and expect the computer to compensate. Your car will run like crap. It will be trying to adjust and make it's calculations based on the stock injector calculations, which doesn't work.

 

How can it throw it off? Your exhaust mixture is the same 12 inches down as it is in the stock location. It also is still reading the exhaust from all 4 cylinders per side, just like it does the way their plumbed into the manifolds. Since its a sealed system, I dont see how the exhaust mixture can change that drastically, especially since its only 12 inches. I mean, i understand what your saying, but its not like their being moved several feet, its only a matter of a few inches?

Is it because the sensor remains colder in a header than it does in a manifold that gets heat soaked really fast? Where as the headers you could almost toch them where the O2 comes in? I really dont see the headers cooling and affecting the exhaust mixture that much? But I'm not going to claim to know everything ... I would like to know how it affects it though, further away or not, what is the difference that makes it run richer?

 

I have a true Bolt-on queen. well for now anyway.

Lid, filter and a Borla Exh and catted Y w/ LT's.... That's basically it... Dyno'd 336/346 after an LS1 edit.

 

Not trying to be a jerk, but those #'s are kind of on the low average side. I wouldn't call it a bolt-on queen.

 

Agreed. After my lid and cutout, i was putting down 330 to the wheels. So 336 after lts, catback, and lid, those arent the best numbers. Definetly not bolt on queen worthy.

 

He's running through cats though. His car is a 2000, so it wouldn't have the LS6 intake manifold right? I dont really follow the stock minor factory changes through the years. Their not bad numbers either for cats, and only a intake/exhaust.

I would say those numbers are pretty close to what it should be at. Say 300-305 stock RWHP, + about 30 for an exhaust and intake.

 

Yes!

 

Mine is a 2000.....and i have cats....and stock manifolds.

 

Those #'s are just from dyno queen status IMHO. Calling your car a dynoqueen suggests that you are putting down higher than average #'s for the mods you have. 336rwhp is not higher than average for a longtube car by any means. Strong cars like Aklaims can put down 330 with a lid and catback. I definately wouldn't consider 336rwhp for any LS1 with longtubes a "dynoqueen." I've seen strong cars dyno 350rwhp with just longtubes....now that's what I call a dynoqueen.

 

i think it was the 01-02s that came with the LS6 intake,

but i was thinking the other day that the older cars had the LS1 intake and were actually rated lower, as to where the newer ones had some differences adn the LS6 intake, o intake and headers with exhaust may make slightly more power

but im not sure, i dont know much about my LS1s

 

so....does anyone know the price of tea in china?

cause i've heard that it's a steal...



when is this thing gonna get locked....

 

You are correct, all 01-02s came with the LS6 intake. And all of mine were .15 faster in the 1/4 than non ls6 intake ls1s ive driven.