when you pair sequentially the exhaust pulses from those cylinders join in such a way as to enhance upper rpm power.

you must understand the firing order of the engine first before you understand anything else. in looking at the firing order of the engine, begin with the first cylinder being fired and then what the other 3 cylinders are doing while that 1 cylinder is being fired.


you must also understand the firing order in terms of crankshaft degrees where each stroke of the 4 stroke motor occupies 180 crankshaft degrees.

once you sort that out, you then know how each exhaust pulse leaves the engine in what order relative to the other exhaust pulses.

when you join the 2 energies of 2 exhaust pulses at a merge collector on the header you join their energies together to help expel the gases faster and create more scavenging at cam overlap.

 

Thanks, MD. I'm guessing for my NA power requirements, this will not be much of an issue, since all of the headers that fit my Teg's stock cat seem to be non-sequentially paired. I won't be able to broaden the powerband through this method. Also, looking at my legal requirements, I don't think I have choice; those CARB exempt headers which are only made by the bigger companies such as Comptech or DC sports (unless someone out there knows better). From what I have seen, they are non-sequential. Nonetheless, its better that I know, than not. I'll do some further research, especially on firing order and the behavior of each cylinder in reference to each other.

Thanks again.

 

most USDM cat sized tri-Y's (if not all) are non-sequential. you really don't have a choice there. we learned that these severely limited your gains back in 1999 and usually top out at a 8-11 whp gain.

only the hybrid tri-Y's that gain 17 whp or more with fuel tuning adjusted to their breathing are sequential with bigger diameters including at the collector.

if you are going for squential pairing in a USDM sized collector, you're limited in the US to 4-1 layouts.

 

More information on this subject

 

Thanks for this info guys. The discussion and the link was very informative. This totally enhances my understanding.

 

This is all very good info. For the header part of my system, I will be going with the Comptech 4-2-1 header with a 2' collecter....great reviews by most members, emphasis on midrange characteristics (which is good for my LS), and seemingly good build quality/materials. The only thing that worries me is that the merge collector length seems to be on the short side.

I have some reading to do to fully understand what the exhaust does from the cat back, but in the meantime, I wondering if its worth it for my pure bolt-on only LS. It seems as if all the work in shaping the powerband is done in the header (wish I knew this back in 92 for my fart can civic), and the exhaust system, from the catback, only facilitates this. I'm teetering on saving my money on this and not buying it if there is no power gain relevant to my goal of broadening midrange power.

 

To clarify my previous post, after getting this 4-2-1 comptech header and keeping the stock cat, does anyone know if it would be worth getting the catback portion of the exhaust?

Thanks in advance.

 

Exhaust system is defined as the entire system which removes the exhaust gas from the head. on a street car it starts w/ the header, moves to the cat, then onto the b-piping and finally exits out of the muffler. Its not just one part, its a system of interrelated parts that work together to acheive evacuation of the burnt fuel mixture. Think of it like a basketball team. You can't win if you only have 2 or 3 players, you need the starting five (in this case a header, cat and catback) if you want to win the game.
Of course upgrading one portion is better than nothing at all. But you won't realize the full benefits of each individual part until you get them all working together w/ each other harmoniously to reach your performance goals.

 

Thanks Blueteg. The basketball analogy is good, however, if you talk to guys like MJ, KB8, etc, they would argue otherwise, hehe.

I understand the exhaust works as a team or system. However, from my previous posts, I am determined to stay within california state law and whatever other restrictions there are. This means CARB exempt headers, adequate noise level exhaust, stock catalytic converter (in Cali, after 98 are required to keep stock cat). Its very constraining, but I'll stick to it since it affects my life with this car.

As a further background to my specific goals, I had been in discussion with John G. from Hytech on actually buying the entire system, I/H/C/E for my LS 4 door from him. I thought great, this is the one that all the truly knowledgeable people on TI.net talk about. It has all the desired characteristics. However, when I asked him if the system he makes is CARB exempt, he said no.....hence no go for me (for those interested however, John did say his full system will pass smog).

So in trying to stay within these design goals/restrictions, my only choices are those crappy 4-2-1 headers with 2" collectors. The reason I asked about sequential pairing is that, though I somewhat understand the reason behind each point in header design as discussed in MD's article, I do not understand the relative importance of each design characteristic....sequential primaries in a 4-2-1 vs. long 4-1 primaries, long merge collector, etc. If I must forgo something, what is more important to have for an LS where I am trying broaden and emphasize the midrange?

After all that, unfortunately, my choices are few. I came to the comptech 4-2-1 conclusion because it is a well-made header. It seems I really have no choice in the matter. If all things are equal for these headers, I will err on the side of daily drivability and quality.Hence, comptech TIG 4-2-1 w/ 2" collector.

And relating to my question about the catback exhaust portion; will the stock cat flow enough to make any catback exhaust system I have impart an effect? How important is the cat in terms of flow; is it so much a choke point that the benefit of $700 hytech exhaust is even worth it (I'm not in this for looks)? So, in a very LARGE nutshell, is my dilemma. I'm trying to make an informed decision within the constraints of the law, (not to mention quality, reliability, etc).

Thanks for helping me out (and for sticking through this post), both you and MD.

PS. AZ with no AC? I thought AC was an AZ state law! Just playin, I went ASU, and I used to bike to class in the 112 degree heat. Its a dry heat....

 

Well in order to give you an idea of will getting a cat back help with your stock cat... in my car right now a 91 GS... After installing an AEM CAI and feeling a pretty nice power gain (probably cause I had a stock filter on my stock instake from 91 to 2003).. I went and put a Greddy cat-back on the 91 and felt a larger gain than when I put the intake in, keep in mind I still have stock headers and cat.. so even when you have new headers and a stock cat... you'll still feel the gain

hope I helped, Jeff

 

I'll let the CA people like austin and SurferX with complete Hytech exhaust systems chime in here since I don't live there and don't know your CARB exemption and emissions licensing procedures.

I think we've milked the diameter sizing and exhaust flow speed/backpressure thing to death here in the articles and included former Skunk2 engine builder and LS VTEC inventor Steve Rothenbuehler's dyno (in CA) of his B20VTEC with and without a backpressure restriction after the cat in the exhaust article. No need to have a seance to resurrect that dead horse to beat it to a pulp again. if you don't get that concept then so be it because I don't think anyone can explain it any simpler.

 

surfintegra91, thanks. Its interesting that you had more of a perceived gain after the exhaust. In this instance, the stock cat is not the rate limiting factor.
Our setups are a little different, but the subjective info is valuable nonetheless.

I would be interested in what SurferX does with his Hytech system when it need to get smogged....we are both OC people by the way, so we cant really get anymore similar than that in regards to the laws. I was ready to get the entire Hytech system, but was really disappointed when they weren't CARB legal.

Mike, with all due respect, I did not ask anyone to simplify it for me. If that was the perception, I apologize. I was afraid this would be the case when reading my post, and seeing that I was also a noob. I was only asking for a point of reference or personal experience on sequential primaries (and later, other exhaust characteristics), and whether their presence makes a difference for my relatively low output app and goal. I don't have any (point of reference or real world experience with exhaust systems), and I do not want to go in blind purchasing this system.

I again, apologize to Mike and to all. I really am trying to learn something here and make an informed decision, even something as simple as my header/exhaust decision on my lowly 4dr LS. Tryin to do it right the first time, as it is said so often in these forum. Thanks again to all.

Patrick

 

You will pass smog with the HyTech system, my car was the guinea pig to see how the Renault OEM cat he uses performed on the B-series motors.

If you're worried about CARB stickers and other assorted things then there is a smog station right next to HyTech that knows about performance mods, engine swaps, etc. and will smog you. All that matters is that your emissions are clean and the necessary hoses are connected in your engine bay. Austin and I were there with someone from Sport Compact Car magazine (I forget who, it's been awhile) who had a hybrid Civic with a JDM ITR engine that was getting smogged.

 

Thanks surferX. That system was/is my first choice....I would be interested to see what other California members experience are in terms of this system and smogging it, without the benefit of a smog station that knows performance mods. Did anyone not pass visual inspection?

on the other hand, if what you are saying is true, driving to Irvine every other year to get smogged isn't a bad trade-off if the rewards are as great as touted.

 

I haven't seen one of these headers designed for an LS yet, and I haven't heard about anyone having one let alone dynoing it so I have nothing to show as far as B18B performance on these types of headers. The HyTech system is very expensive and I would get it only if I knew it was absolutely proven to perform better than anything else out there (which I did, because it was proven on the B18C).

It sounds like you want to stay pretty mild and keep everything universally legal, which is understandable. You may be happy with just a standard I/H/E (leave the stock cat) and you don't have to spend a whole lot of money. To make more power sometimes you have to step outside the normally defined boundries, and spend that extra money. I'm sure you've read through alot of the information we have here and know what has to be done, it's just a matter of wanting to actually do it.

And you live in Orange County, wherever you are Irvine can't be more than 15-20 miles from you. Is your work like next door? "Driving there every other year may be worth it", whatever

 

Live in fullerton, work in Costa Mesa - drive straight down Harbor everyday. From my limited knowledge, Hytech seems to have all of the characteristics I would want, but as you said, it has not been proven on the B18B. As for cost, $2250 for the H/C/E, as well as a lengthed B pipe for 150 (2400 total). That is pretty steep, esp. for an unproven system....I could do a swap and replace my 120,000 engine for a little bit more. The fact that it is not legal and unproven killed the deal for me. So, those are high prices to pay, and I do not want to do that, even if gains are large. I just don't see the value right now of going Hytech (for me and only me).

I see that there won't be a ton of difference in the lower end 4-2-1's w/ 2' collectors. So asking about sequential primaries, etc was essentially a moot point, when my needs were more simplistic or mild. I only get stifled when I go for bigger gains (which I am not).

I probably will go for a mild I/H/E setup after weighing my goals and cost. I think I will like the gains I see and will be happy with them, judging from the threads, articles, and as you and Jeff say. Thanks for your help again. I'll post what I did when I'm finished.

 

Cool, and you can show us what you ended up with at the big TI road racing meet in Buttonwillow this summer right?

 

Haha, its a possiblity, depending on the wifey and my 1 year old clone. I'll find a way....