How did you derive that?

EDIT: My calculations confirm that 300 cfm (about 21 lbs/min) is about good for 300 hp, so double for a true dual exhaust and you are spot on - just wondering how you came up with that though as I think my calculations are too low (according to Corky Bell's book).

 

Do you happen to know how much difference in HP the ceramic 400cell vs. metallic 300cell cats will be?

 

I think Rick mentioned less than a coupe hp loss (NA). The metallic work better (as a cat) and flow better and last longer - so no real downside to them (other than price).

 

the Metallic HFCs can be purchased in 2.5, 2.75 and 3.0" OD.

the ceramics are 2.5 or 3.0" OD

initial price, well, i posted this up to get interest, if you'd like a custom set. PM me and i'll see what i can do. they'd like to goto production i think it'll be a good idea.

 

Can the 3" pair up with any lower sized flange? (within reason)

i.e. Do the bolt holes on the flanges line up regardless of the pipe diameter?

 

These are the same CATS that FI uses...flow characteristics will be identical.

 

OK - so other than a BUNCH of experience in building cars over the years and testing different combinations to know what will work best - in many applications, any REAL estimate is only that - an estimate.

Nobody can REALLY say exactly what diameter is best - unless you have a common and reliable baseline to compare with. So, for instance - saying that a certain diameter pipe will work up to a certain amount of HP - really means nothing, unless you have actually tested several scenarios, etc.

The real basis for the maximum HP/performance gains vs diameter to choose for the pipe, all depends on pulse equalization, and speed of flow. That speed requirement will vary based on amount of air that is ingested into the engine, the amount of fuel being burned, the efficiency of the scavenging effects (headers, X or H pipes or Y pipe) and then how fast or slow the velocity should be for optimal performance.

Bigger is not always better - in fact it is usually overrated (unless FI or especially turbo). If the pipe is too large, the gases cool down too quickly and force backpressure and HP loss, as the engine must force the fresh gases through the heavier cool gases. If the pipe were smaller in this case, the gases would not cool down prematurely - thereby raising HP.

With that said - The greater amount of air intake and fuel delivery, will directly equate to effectively and efficiently handling the exhaust/waste pressure being exerted. The hotter the gases can stay in the pipe through their travel through the exhaust system - the more power the car will see.

There is a reason why most companies offer products like this in certain sizes - maximum performance with an ear to sound quality. An NA application using 2.75" pipe - may be OK - with an engine build/high compression, etc. Trying to re-invent what is already out there, doesn't make a bunch of sense, unless superior quality, service and backing are in the mix with a potential design improvement.

Rick

 

Yea - between testpipes and 400cell HFC's - the TP's will have ~3HP more. If Metallic 300 cell - add another -1 or 2 HP gain.

Rick

 

Thanks Rick. I think the data above seems to indicate that pipe diameter more directly impacts flow than the cat at airflow levels commesurate with the output of a 600 hp engine. That said, a 2.5" diameter pipe was not flow tested so I have to average the crappy 2.25" flow # with the 2.75" when I know the relationship is likely not linear.

EDIT: In other words, if 2.5" pipe had been tested and found to be similar to 2.75, then I wouldn't look any further (beyond the FastIntentions 2.5" metallic HFC that I have now). If they flow more closely to the 2.25", then I would consider a new set of cats.

 

We've heard/had the CATS on cars with many levels of performance - up to 550+ HP on an FI/turbo car. I can't recall who it was at the moment though. Performance on the system, with the cats (metallic), was massively effective at providing proper flow and tuning ability.

Typically, you would want to have a 3", possibly more, exhaust system for a turbo car - over ~450 HP. for the SC's - it's the perfect combination.

You are very correct in realizing that there is ZERO linearity comparison between the 1/4" of pipe diameter. Mods make a huge difference. I love it when some say that intake mods have zero effect on exhaust. Well...if you are getting more air, and adding more fuel, you'll have MORE combustion, therefore more by-product and pressure from that by-product being expelled from the system.

Tuning the proper pipe diameter, with appropriate mufflers, resonators and bends, is the tuning side of development and R&D that takes much time and expense. And this level of work has to be done on many cars, various years and various configurations to make sure it's done right once offered publicly.

Rick

 

I'm looking to get 500 rwhp on Sharif's DynoDynamics with the full FastIntentions exhaust (with the metal cats).

That's about a 550 rwhp dynojet #. That's 600-650 at the crank.

We'll see if Sharif can hit that target this week using 700bb turbos on 93 octane. My fingers are crossed cause I have a feeling I'm pushing the limit with this exhaust. Your anecdotal evidence of someone else hitting 550 gives me some hope.

 

I can't wait for the result...

Rick

 

You know I want some Cheston. 70mm stainless to match the Greddy EVOTTs out there is a good move. Did you get the flex sections put on your exhaust?

 

Rookie:

No. goin to add the flex portion soon.



Rick- If you'd like to start a new post on Fast Intentions HFC in another thread, please be my guest.

The reason why we went with 2.75" HFCs is to match the Greddy EVO TT exhausts as well as to mate with the turbo downpies of my Turbo system.

RCDash: If a 2.5" is good enough for you, then please go to Rick for them. Technosquare is still in the development for other sizes and toying with other OD sides/applications. i.e. dual cats to a Ypipe for a single outlet exhaust... etc.

this post was to follow up on my make-your-own-HFC thread, and shouldn't be turned into who's HFC is better, as it seems it has.

also please note we only went up to 400CFM on the flow bench. that is NOT THE MAX FLOW of these HFC. just the bench test results from our test setup.

if you'd like to see higher flow numbers, i can arrange for that test, along with other brands if people so choose, given availability of products.

thanks

Cheston

 

Very preliminary data shows about 400 whp at 9 psi and drop off above 6000 rpms (I have JWT S2 cams and a 3/8" spacer).

EDIT #2: Now that I look at other builds, this is not so bad . I think I need to give this a chance... We'll see what happens when we turn the boost up to 15 psi...

Chebosto or Rick: if you guys can find me 3" pipes with metallic cats (300 cell or less), I think I'd be willing to upgrade (sell my 2.5" hfc) just to rule it out as a source of power drop off at high rpm.

I'll shoot Tony an e-mail to see what he can do. I want to keep my FI exhaust - so this seems like a reasonable next step.

EDIT: I need these ASAP - PM or let me know who to call to inquire - thanks.

Does anyone make "blow off valves" to reduce exhaust backpressure that will fit into say the O2 bung so that they are removable? Something not so obvious as exhaust cut-outs (which will not pass visual inspection here in NC even if closed).

 

Well as an update 2.5" 300 cell FI high flow cats appear to support at most about 420 whp on a DD dyno at 12 psi, roughly equivalent to 460-480 dynojet at the wheels. That's not enough for me considering the money put into the other components, so for the time being I am moving to APS 3.5" test pipes and will look forward to new applications in the future, such as 100 cell metal CATS w/ 3" inlet/outlet.

 

Have you guys tried looking at berks metallic cell substrate cats thoseare another HFCs i have seen on this site .

 

those are 2.36" - TOOOO small.