Attn: HKS Hiper Owners!!!
08-16-04, 01:02 AM
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Attn: HKS Hiper Owners!!!
This was brought to my attention by Brian at BNR last week when we were talking figures over the phone before our tuning session that finally came around this past Thursday. I should have known better but I never thought to lay down and stare up my own exhaust long enough to notice it.....
HKS Hiper catback exhaust units are constructed with a baffle that's welded into the cannister. It throws you off since there's 2 holes drilled for installing silencers in the tips. The baffle is on up inside of the cannister and it has a flat round section that presses up against the last part of the packing and then bells inwards towards the midpipe, where it extends as a pipe that is about 2 and 3/8" as Brian measured. The baffle extends about half way to 2/3's of the way back over the cannister packing. Not only does this design shrink the piping diameter, it also causes ridiculous turbulence at the exit location of exhaust gas since it backs up the flow and spins gas around as it hits the back of the baffle trying to get out. I took up the annoying task of cutting it out. It wasn't near as easy as I thought it would be, so I thought it was worth it to take some pictures and post it as an informative thread for those of you who have this exhaust and need that 3" all the way through. I believe this design was geared more towards the idea of keeping exhaust flow closer to stock than reducing sound. After I cut it out, I didn't notice too much of a difference in sound, however it gets rid of the flappy pulses at idle and I think it takes out some of the higher pitched sounds at heavier throttle usage.
Shot of the baffle:
Shot of unsuccessful attempt to sever the baffle from the internals of the cannister by grinding through the three visable welds its attached by:
Those welds are probably the only ones that are made to install the baffle during manufacturing, however with all the heat around that area and after driving the car so many miles on that ehxuast, I'm not sure if its true with new out-of-the-box units or not: the outer part that mounts flat on top of the end piece of packing is extremely difficult to separate- so difficult infact that I was unable to do so and found that grinding down those 3 welds was a was of time. The easiest way to do it yourself is with some good strong cutting bits. Cut around the bell of the baffle in a way so that you will have a smaller portion to remove through a bigger hole in what's left. Otherwise, you'll end up cutting the baffle off to separate it and then cutting or grinding down what's still attached before you can actually pull it out. I ground through it half way and ran out of bits so I had to go to the store the next morning and pick up some cutting discs- I would have cut through it from the beginning but I did not have any cutting bits for my dremel.
Here's a shot of the cut out portion of the baffle. You can see the chunk next to it- part of the bell of the baffle that I had to cut off to get the main piece back out of the pipe:
Most of the bell of the baffle was torn up when I was cutting through it using various techniques, so it doesn't appear to be the way I'm suggesting that it be done.
Here's the final shot of the exhaust- back to the piping diameter we prefer for having a loud exhaust:
It was fairly ragged around the parts of the baffle that wouldn't come out, so I went at it real good with a metal file and grinder bits on a dremel.
Hopefully this post will be somewhat useful to all of those who have this exhaust and are unaware of the baffle's existance. May all your flows be increased upon reading this post.
-Dave
HKS Hiper catback exhaust units are constructed with a baffle that's welded into the cannister. It throws you off since there's 2 holes drilled for installing silencers in the tips. The baffle is on up inside of the cannister and it has a flat round section that presses up against the last part of the packing and then bells inwards towards the midpipe, where it extends as a pipe that is about 2 and 3/8" as Brian measured. The baffle extends about half way to 2/3's of the way back over the cannister packing. Not only does this design shrink the piping diameter, it also causes ridiculous turbulence at the exit location of exhaust gas since it backs up the flow and spins gas around as it hits the back of the baffle trying to get out. I took up the annoying task of cutting it out. It wasn't near as easy as I thought it would be, so I thought it was worth it to take some pictures and post it as an informative thread for those of you who have this exhaust and need that 3" all the way through. I believe this design was geared more towards the idea of keeping exhaust flow closer to stock than reducing sound. After I cut it out, I didn't notice too much of a difference in sound, however it gets rid of the flappy pulses at idle and I think it takes out some of the higher pitched sounds at heavier throttle usage.
Shot of the baffle:
Shot of unsuccessful attempt to sever the baffle from the internals of the cannister by grinding through the three visable welds its attached by:
Those welds are probably the only ones that are made to install the baffle during manufacturing, however with all the heat around that area and after driving the car so many miles on that ehxuast, I'm not sure if its true with new out-of-the-box units or not: the outer part that mounts flat on top of the end piece of packing is extremely difficult to separate- so difficult infact that I was unable to do so and found that grinding down those 3 welds was a was of time. The easiest way to do it yourself is with some good strong cutting bits. Cut around the bell of the baffle in a way so that you will have a smaller portion to remove through a bigger hole in what's left. Otherwise, you'll end up cutting the baffle off to separate it and then cutting or grinding down what's still attached before you can actually pull it out. I ground through it half way and ran out of bits so I had to go to the store the next morning and pick up some cutting discs- I would have cut through it from the beginning but I did not have any cutting bits for my dremel.
Here's a shot of the cut out portion of the baffle. You can see the chunk next to it- part of the bell of the baffle that I had to cut off to get the main piece back out of the pipe:
Most of the bell of the baffle was torn up when I was cutting through it using various techniques, so it doesn't appear to be the way I'm suggesting that it be done.
Here's the final shot of the exhaust- back to the piping diameter we prefer for having a loud exhaust:
It was fairly ragged around the parts of the baffle that wouldn't come out, so I went at it real good with a metal file and grinder bits on a dremel.
Hopefully this post will be somewhat useful to all of those who have this exhaust and are unaware of the baffle's existance. May all your flows be increased upon reading this post.
-Dave
08-16-04, 09:44 AM
#2
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VERY interesting. I do wonder if they tried to choke the exhaust down for some reason - there's probably a reason that thing is in there.
Have you ever seen the silencer that goes in the tip of the HKS Hipers? I know Apexi had 2 different style silencers for the N1 - one that was a "can" with a bunch of muffler packing, and another that looked kind of like a funnel with no packing. Anyhow, if HKS has the funnel style, I wonder if the funnel's end is supposed to fit into that baffle or something.
I'm planning on the HKS Hiper for my cat-back, since I like the N1 can style, you can get a silencer for it (VERY handy on long car trips), and it's mighty cheap, not to mention it's HKS quality. This is good to know!
I'd like to hear further impressions after you live with the car for a bit - any difference in sound or loudness, differences in power, etc.
Good work!
Dale
Have you ever seen the silencer that goes in the tip of the HKS Hipers? I know Apexi had 2 different style silencers for the N1 - one that was a "can" with a bunch of muffler packing, and another that looked kind of like a funnel with no packing. Anyhow, if HKS has the funnel style, I wonder if the funnel's end is supposed to fit into that baffle or something.
I'm planning on the HKS Hiper for my cat-back, since I like the N1 can style, you can get a silencer for it (VERY handy on long car trips), and it's mighty cheap, not to mention it's HKS quality. This is good to know!
I'd like to hear further impressions after you live with the car for a bit - any difference in sound or loudness, differences in power, etc.
Good work!
Dale
08-16-04, 10:16 AM
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Thanks for the reply, Dale. As far as sound goes, I used to have sort of a light flapping sound at idle that I noticed after I ported my motor. Its no longer there. I guess it was just from the exhaust pulses hitting that baffle's turbulent region at the end of the exhaust. Up on throttle, you can't hear it because the exhaust pressure is more constant. It only "flaps" at idle because the pulses are separated.
About the power difference, I am running a very aggressively ported engine, with lots of fuel and a TO4R. I had it on the dyno last week but I was unable to tune out the boost on it because I have a corroded fuel pump relay that I forgot to replace. All the rain out in Indianapolis trashed several relays before I figured out what was going on and fixed the problem. The car was pulling mid 300's of horsepower with the boost turned down after Steve Kan set the car up right, but I wasn't able to get any real numbers when we couldn't fix that fuel pressure from falling off. The problem with numbers is that on my setup, there are so many people I'd be in range with who are using exhausts that don't come with complimentry baffles that can't be removed like the one in the Hiper, so I wouldn't really be comparing. I can't really weld that thing back in there and do a dyno session on it though.
For baffling the exhaust, that thing really didn't do much. I think it was really more for adding safety backpressure so that the stock exhaust flow level wasn't completely thrown out the window with the swap. That exhaust is pretty old of a model and I think HKS had a couple others with that lower, closer to stock flow. I didn't notice any complete incredible sound change, but I finished pulling it out right before I drove down to Alabama for this tuning session and I wore ear plugs most of the way- mostly because you'll pay for it with a longer drive like that if you don't. Maybe I'll drive it around this afternoon and see if I can tell the difference. After I get tuned, I am going to be shopping for a more street-happy exhaust setup to use with a different midpipe that doesn't resonate so much and a catback that cuts out those loud rotary overtones to a reasonable degree.
About the power difference, I am running a very aggressively ported engine, with lots of fuel and a TO4R. I had it on the dyno last week but I was unable to tune out the boost on it because I have a corroded fuel pump relay that I forgot to replace. All the rain out in Indianapolis trashed several relays before I figured out what was going on and fixed the problem. The car was pulling mid 300's of horsepower with the boost turned down after Steve Kan set the car up right, but I wasn't able to get any real numbers when we couldn't fix that fuel pressure from falling off. The problem with numbers is that on my setup, there are so many people I'd be in range with who are using exhausts that don't come with complimentry baffles that can't be removed like the one in the Hiper, so I wouldn't really be comparing. I can't really weld that thing back in there and do a dyno session on it though.
For baffling the exhaust, that thing really didn't do much. I think it was really more for adding safety backpressure so that the stock exhaust flow level wasn't completely thrown out the window with the swap. That exhaust is pretty old of a model and I think HKS had a couple others with that lower, closer to stock flow. I didn't notice any complete incredible sound change, but I finished pulling it out right before I drove down to Alabama for this tuning session and I wore ear plugs most of the way- mostly because you'll pay for it with a longer drive like that if you don't. Maybe I'll drive it around this afternoon and see if I can tell the difference. After I get tuned, I am going to be shopping for a more street-happy exhaust setup to use with a different midpipe that doesn't resonate so much and a catback that cuts out those loud rotary overtones to a reasonable degree.
08-17-04, 01:11 AM
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I drove the car around a little bit tonight when I dropped the movies off at Blockbuster. Needless to say I didn't wear my ear plugs since I wasn't getting on the highway for extended periods of time. The car does sound a little different. I can't quite explain the change but I'm sure it just makes it sound like an N1. The only difference left is the build of the cannister packing.
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08-17-04, 11:01 AM
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Hey Phil,
Cutting that baffle out is a really shitty job if you avoid my mistakes. When I was grinding those 3 welds down, I kept at it hoping that they would just pop loose but I was very wrong. I ended up wasting a lot of time and broke a lot of dremel bits. Its really best to just go at it with cutting discs and sever it along the bell of the baffle like I suggested. Then you can grind down the outside from there or cut off any larger pieces that would take too long to grind down. The baffle itself is made of steel and is not very malleable, even when a good portion of it has been cut through. I tried several times to make a hole with a carbide bit large enough to get a screw driver in and then try to pry it askew so that I could get a file through the cut to grind out some more room to work with. That never worked, even with very little of the baffle still holding on. Just cut if off, grind it down and get all the pieces out of there. Watch the packing screen when you're cutting though- I bit into mine a little bit when I was losing visability around my wrists while I was cutting.
Cutting that baffle out is a really shitty job if you avoid my mistakes. When I was grinding those 3 welds down, I kept at it hoping that they would just pop loose but I was very wrong. I ended up wasting a lot of time and broke a lot of dremel bits. Its really best to just go at it with cutting discs and sever it along the bell of the baffle like I suggested. Then you can grind down the outside from there or cut off any larger pieces that would take too long to grind down. The baffle itself is made of steel and is not very malleable, even when a good portion of it has been cut through. I tried several times to make a hole with a carbide bit large enough to get a screw driver in and then try to pry it askew so that I could get a file through the cut to grind out some more room to work with. That never worked, even with very little of the baffle still holding on. Just cut if off, grind it down and get all the pieces out of there. Watch the packing screen when you're cutting though- I bit into mine a little bit when I was losing visability around my wrists while I was cutting.
