Possible Cattman Headers!!
I haven't said anything about this project because I wanted to do the testing first, but I'm quite pleased to report that I've put a beautiful set of prototype headers on my 97 Maxima and they make some pretty good power. And they sound incredible!
Here's the basic information...
Test car: 1997 Maxima 5 speed, 103,000 miles on a well used engine that's a little weak and a bit past its prime (as indicated by its relatively low "before" dyno run); baseline measurements taken with a JWT intake, Cattman Cattback exhaust and a stock Y-pipe.
Baseline run w/ stock Y-pipe: 167.5 max hp @ 5000rpm; 182.6 max torque @ 4000; avg hp 132.2 from 2300-6100 rpm; elapsed time 10.32 seconds from 2300-6100 rpm
Run w/ prototype headers: 183.9 max hp @ 5000rpm; 197.5 max torque @ 4600; avg hp 143.1 from 2300-6100 rpm; elapsed time 9.83 seconds from 2300-6100 rpm
Although the difference in maximum hp is 16.5 (about 20hp at the crank) and in maximum torque is 14.9 (about 18 ft/lb at the crank), the largest differences between the two runs are 18.6hp @ 5400rpm (about 22.5hp at the crank) and 18.5 ft/lb at 4800rpm (about 22.4 ft/lb at the crank).
I'd also note that the "average horsepower" is a very useful comparative figure. You could have a modification that spiked the power at upper rpms but not have a large effect on horsepower across the rpm range. These headers increase the average horsepower by 10.9, which is a BIG impact that indicates that the increases in power occur significantly across the entire rpm range, not just in some concentrated range.
Based on my experience, figuring all other things being equal (and noting this is a very well-used engine, burns some oil, etc.), I'd say these headers make about 25% more power than a performance Y-pipe.
I don't know what the price will be for a set or exactly when they'll be available. They'll be somewhat more expensive than a Y-pipe, but not a lot because they will probably be made from mild steel (rather than stainless) to keep the cost down. Given that my set took an experienced mechanic about 6 hours to install, installation will obviously be more expensive.
Oh yeah, the sound... These aren't louder than a Y-pipe, but they sound sweeter due to the equal length primary and secondary tubing -- much more melodious and without the slight harshness in tone that Y-pipes have under heavy acceleration. I'm not kidding, it really makes the car sound cool.
I have a typical DynoJet graph as well as the table printouts (at 100rpm intervals). Also have an Excel spreadsheet containing the two runs for analysis purposes. Will be happy to send copies to any who inquire (contact me directly at email@example.com).
No chance to look into this yet, but these headers should be useable on the 1999-2001 CA/NLEV engines too, though it may be necessary to add an exhaust sensor someplace. It not impossible that they might work on the VQ35DE too, we'll see.
Brian C Catts