DaveGS4

iTrader: (2)

Jaime - if you're "in" you commit by doing like it says in the original post (pasted in again below).

fever

In.

jmecbr900

Done as you commanded, sir.

I'm now officially "in".

aristo400

Those C's headers are beautiful... But before jumping in, will these headers be equal length? How hard is it to remove the headers? It looks tight in there. I will need to know these question before purcahsing them. Thanks.

Also, I live in California but doubt the smog guys would even notice. It shoudn't even affect emissions.
It might be a little louder since the cast iron manifold is excellent at holding in noise.

-Jeff

JBrady

Jeff,

Yes, the Cs headers "look" pretty but if you look closely the tubes actually interfere with each other and that makes for a sub-optimal "working" part. The pictures are not to indicate actual final look just an idea of concept. I suggest you re-read the entire first post and in fact this entire thread as I have addressed the tube length and the installation unkowns. Quickly, no, not equal length nor required for the power we are targeting. Equal length primary tubes are only effective in a small RPM range. The rest of the time it is all about flow, velocity and scavenging. For any value the equal tube style would need primaries neary 3 feet long each and that obviously is not going to be a shorty style header. The shorty design should do very nicely just like the shorty design for the Tundra for which the dyno chart is shown. Installation is not easy, and as yet an unknown. Also, the stock manifolds are tubular not cast iron. Here is a link with pictures of the stock manifolds:

https://www.clublexus.com/forums/sho...hlight=air+box

LOTC

Sent PM, I am in

Guru

I'm in too. If he can make longer length primaries I'd be willing to pay a bit extra. I'm making custom downpipes/test pipes anyway so to me it doesn't matter. I have full TIG welding capabilties here.

JBrady

Dan, why do you want longer primaries? If you build a long tube equal length header you can create an additional scavenging effect in a narrow RPM band but 6" vs 12" vs 18" is not going to get that effect. What we are wanting is scavenging throughout the RPM range. To do this we want to preserve the velocity and energy of the port. This takes a smallish diameter primary pipe and carefully formed merge areas taking care to keep the collector volume at each merge as small as possible and aerodynamically efficient. After that you get the catalyst which is not much help but required. Then the rest of the exhaust system. If the rest of the system is also designed to scavenge (same principals, larger pipe diameters) the whole system will "pull" from the exhaust ports IOW scavenge. Make sense? If you want tuned equal length headers you will need around 30" primaries to put the "tune" at 6000rpm.

3dog

iTrader: (1)

hey count me in 99 gs400 sent my pm ivan

Lexkost

Will they be smog legal in California ?

3dog

iTrader: (1)

with the headers and a good exhaust will we also need an air intake to maximize the benefits. ivan

DaveGS4

iTrader: (2)

Please read the entire thread. This was covered already Look starting with a post by "FutureGS400"

DaveGS4

iTrader: (2)

I don't know for sure (and no one really does since these headers are new), but I'd guess the effect would be similar to having an intake only or intake + exhaust. They compliment one another and work better than they do individually. Of course the 'combination' of mods that will work best is unknown at this point.

aristo400

I just think that equal length headers will produce more top-end power without sacraficing any low-end power. That's why I asked about equal length headers.

If your local craftsman can produce headers with welds and bents as good as those C's headers I'll be very very impressed with the work. Well, I'm in if, the headers install do not require removal of the engine.

-Jeff

BTW, Your right about the headers. I thought they were cast iron manifolds. My bad.

JBrady

Jeff, of course you have already received my direct email reply to your request but I would like to address your above statement "more top-end power without sacraficing any low-end ". Of course this is not meant to retort you as you are very knowledgable on this subject. Rather to help the majority of readers that are not exhaust experts and must rely on what others tell them.

While I agree it is of course theoretically possible to produce a higher power exhaust header/manifold by optimizing the length to the RPM window targeted... the real world situation shows that the added expense, increased installation difficulty and deviation from factory emissions configuration make long tubes a poor choice for 99% of road cars. Also, the KEY to making power is optimizing flow. This a accomplished by creating the lowest possible pressure at the exhaust port during the last half of the exhaust event when in cylinder pressures are dropping rapidly and the pressure differential becomes most important. Long tube headers isolate the individual ports and create a resonance tune effect dictated by tube length and diameter. This tune only happens in a small RPM window. Above and below that RPM the main effect is due to velocity scavenging. Velocity scavenging is the key to the HFVS header and is designed to enhance the effect from low to high rpm. The performance difference between the HFVS and a very well designed ELLT (equal length long tube) design is unlikely to be noticeable from the drivers seat. A poorly designed ELLT will actually hurt performance in various RPM ranges compared to even the FACTORY manifold

I for one would be very unhappy to spend big bucks and make all the sacrifices needed for ELLT only to have a car that is LESS responsive in most driving conditions.

So, for an expert like yourself the ELLT is maybe a reasonable choice but I wanted everyone to understand they are not sacrificing by using the HFVS design with a good cat back secondary system (key to the overall performance of ANY wide RPM operating system).