First let me say that my dyno #'s from over a year ago where 304.6 rwhp and 338 rwtq. That was with FMS shorty headers, MAC h-pipe and a Flowmaster catback. That was probably at ~160,000 miles. Now I've added a Magnaflow catback, Pypes X-pipe and BBK long tube headers. I currently have 176,500 miles on a stock short block. New numbers from the same dyno. 301 rwhp and 323 rwtq. Got the same numbers adjusting the A/F ratio from 12.5 to 13.1 The car blew out a ton of smoke after the run, and smelled really rich. The parameters on the new dyno say 84 degrees F, but it was around 68. And it also says 8% humidity? This is an import dyno shop, there were 7 VTEC engines laying on the ground (seriously!). The manager was convinced that my AFM power pipe was a turbo. So I'm not sure if the lower numbers are from the high mileage and abuse or the dyno operators. Most of my friends in town have gained alot of hp and trq switching to long tubes. Unfortunately the next closest dyno is 2 hours away. I'm hoping to get out to the track on Sunday to get some numbers. The guys at the dyno had difficulty printing out a graph and could only give me a speed vs hp/tq variable. I'm hoping to get a rpm chart tomorrow. The pull started at ~3500rpm and stopped at ~6200rpm I'll try to post some graphs later tonight.
Hmm. Sucks when dyno sessions never go as planned. You have a mail order jms chip right? How did you adjust the a/f then? They should have started the pull lower at 2500, not 3500. Lets see what the track says.
I adjusted the A/F ratio with the regulator. The JMS chip suggests a fuel pressure of 40psi, then you can adjust if from there to richen/lean the mixture They started the pull at 3500 because they're an import place. They didn't realize that I make more hp at idle then their cars do at redline. I have a video, don't know how to post it though, anyone want to host it for me?
Playing with the regulator isn't the ideal way. But lets see what the track says. I know what its like to spend a bunch of money in mods and see little difference. I did an fti cam, valve springs, longtubes and milled the headed .020" and gained a bit of low end power, gained nothing up top and also gained a horrible lean condition. Gained 2 mph at the track. I should have left my 302 combo the way it was and never tried changing it. Should have kept the nitrous too. I wasted a ton of money "upgrading" my combo and trying to fix it. If only I knew then what i know now. Oh well, I got a 347 now
Hey Chad Here is some info which is a general kind of thing but not in every case does this info apply. I have seen things in the past that show lt's have more efficiency over shortys in the low to mid rpm range. Some of those tests have shown that shortys and lt's can be quite close in the upper rpm range. Grady
All you really changed that MAY give you a noticeable difference is the longtubes since you already had a pretty good setup before. I wouldnt be hopeing for more then like a 10 hp gain with the new setup. I bet it sounds alot cooler tho. Do you have your old graph? Can you see if you made more/less down low where it actually counts?
If I recall catbacks differ only by like 2 horsepower..like literally from one muffler to the next. I have seen conflicting info between longtubes vs shorties and the x-pipe vs h-pipe and have wondered if its just marketing hype when it comes to these mods and HP. What's the butt dyno tell you?
I'm going to try and upload the graphs tonight, I think it was my computer at work that wasn't letting me. Search for my other thread on the sound comparison. I think I like my old set up better. But now my co-workers can't hear me leave work, and my wife can't hear me leave the house so thats a bonus. The NMRA race pages published a dyno comparison between the Magnaflows and Flowmasters on a bolt-on 5.0, the Magnaflows gained 9rwhp. But hey, what do dyno numbers mean? Anyone have the SAE correction factor equation? I'm a little worried that my graph says 8% humidity. There's more then 8% humidity on Mars.
Interesting... This is one of the reasons I never did this to my car. The very few people I have found that did what you have just done didn't gain much if anything at all. BUT, like the others are saying I'd be VERY interested in seeing what the track says as the dyno sometimes lies! LOL! Good luck, and keep us posted.
The LT combo probably produces more overall power (area under the curve). Peak numbers don't mean much. THe track will show this... =-)
The bbk headers aren't the best in terms of power making. They aren't equal lengths and the collector necks down from 3" to LESS than 2.5". Sh itty design IMO. I had the 1 5/8" on my 302 and now the 1 3/4" on my 347. I should have went with 1 3/4" hookers as their equal length and have a real 3" collector. Here is a h/c/i 302 shorty vs longtube dyno sheet from a guy on corral (96cammin2v) Notice the big gains in the 2500-4200 range.
Just what I was trying to get across in my post above. When I saw Chad's original post I had a feeling something like this might be going on with his combo and that is the reson the peak numbers did not change much when he compared the results of the two pulls. Grady
Here's the video. Thanks for the link urban 96, lots of good videos on there. How can I download videos from that site? http://videos.streetfire.net/player.aspx?fileid=781BB154-6345-484A-BCDD-E6D47D9C3DA4
Sounds good, but it would sound better with the 2 chamber flows Looks like you spit out a little blue cloud of smoke at the end after he got off the throttle.
