High flow cat (HFC) question
Thread Starter
Joined: Oct 2010
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Here is a uk dealer that has the 63mm Berk listed https://www.tarmacsportz.co.uk/berk-...-flow-cat.html
I'm sure there are other sources here in Europe though
I'm sure there are other sources here in Europe though
Thread Starter
Joined: Oct 2010
Posts: 254
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My guess is that a 70mm HFC would be less bad than the stock cat, but it's probably worth the extra money to get a 63mm HFC instead.
With stock cat optimal VTEC point is probably around 5000rpm, HFC flows much better which is why you can lower it to under 4k.
But you still need something to alter the factory tune, like flashpro or an aftermarket ecu for example.
With stock cat optimal VTEC point is probably around 5000rpm, HFC flows much better which is why you can lower it to under 4k.
But you still need something to alter the factory tune, like flashpro or an aftermarket ecu for example.
Joined: Nov 2013
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From: Norfolk UK
https://www.s2ktuning.co.uk/Exhaust.html
Thread Starter
Joined: Oct 2010
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Not much of a noticeable change,its much lighter and just a better sound, using OEM exhaust,
https://www.s2ktuning.co.uk/Exhaust.html
https://www.s2ktuning.co.uk/Exhaust.html
Joined: Jan 2017
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My guess is that a 70mm HFC would be less bad than the stock cat, but it's probably worth the extra money to get a 63mm HFC instead.
With stock cat optimal VTEC point is probably around 5000rpm, HFC flows much better which is why you can lower it to under 4k.
But you still need something to alter the factory tune, like flashpro or an aftermarket ecu for example.
With stock cat optimal VTEC point is probably around 5000rpm, HFC flows much better which is why you can lower it to under 4k.
But you still need something to alter the factory tune, like flashpro or an aftermarket ecu for example.
Thread Starter
Joined: Oct 2010
Posts: 254
Likes: 8
I know it sounds logical to pair a 63mm exhaust with a 63 hfc and a 70 with a 70.
I think so far everyone's response was based on logic.
Has anybody ever done an actual test to see how "bad" a 70mm hfc is for a 63/60mm exhaust. If it really has a negative effect?
On the good side, based on logic, I would think that a 70mm hfc with the same ammount of cells as a 63mm hfc, would actually have a better flow than the 63.
There must also be a reason why honda chose 63mm for the exhaust and not 70 or 75mm. Which means bigger is not by defenition better. Which raises even more questionsmarks for me...??????
All with regards to a stock NA ap1 engine.
I think so far everyone's response was based on logic.
Has anybody ever done an actual test to see how "bad" a 70mm hfc is for a 63/60mm exhaust. If it really has a negative effect?
On the good side, based on logic, I would think that a 70mm hfc with the same ammount of cells as a 63mm hfc, would actually have a better flow than the 63.
There must also be a reason why honda chose 63mm for the exhaust and not 70 or 75mm. Which means bigger is not by defenition better. Which raises even more questionsmarks for me...??????
All with regards to a stock NA ap1 engine.
Joined: Jan 2017
Posts: 756
Likes: 65
I know it sounds logical to pair a 63mm exhaust with a 63 hfc and a 70 with a 70.
I think so far everyone's response was based on logic.
Has anybody ever done an actual test to see how "bad" a 70mm hfc is for a 63/60mm exhaust. If it really has a negative effect?
On the good side, based on logic, I would think that a 70mm hfc with the same ammount of cells as a 63mm hfc, would actually have a better flow than the 63.
There must also be a reason why honda chose 63mm for the exhaust and not 70 or 75mm. Which means bigger is not by defenition better. Which raises even more questionsmarks for me...??????
All with regards to a stock NA ap1 engine.
I think so far everyone's response was based on logic.
Has anybody ever done an actual test to see how "bad" a 70mm hfc is for a 63/60mm exhaust. If it really has a negative effect?
On the good side, based on logic, I would think that a 70mm hfc with the same ammount of cells as a 63mm hfc, would actually have a better flow than the 63.
There must also be a reason why honda chose 63mm for the exhaust and not 70 or 75mm. Which means bigger is not by defenition better. Which raises even more questionsmarks for me...??????
All with regards to a stock NA ap1 engine.
https://www.s2ki.com/forums/s2000-modifications-parts-193/performance-60-70-mm-tp-s-hfc-s-842575/page3/
Joined: Jul 2014
Posts: 13,832
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From: Chesterfield VA
How does this HFC and exhaust setup allow for a lower VTEC engagement point?
I can look at my fuel tables and all the the goodies but how to do this is beyond my expertise so I look but don't touch. Greg (Gernby/Gurnby?) knows and transformed my DBW car! -- Chuck
Joined: Aug 2013
Posts: 4,151
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From: Sweden
Stock exhaust is 60mm.
70mm and 63mm HFC use the same core so flow through the core is not a problem.
The problem is the big step down in diameter from 70mm to 60mm, this causes lots of turbulence and hurts performance.
Read through Gernbys thread linked above it's very good information, clickable link: https://www.s2ki.com/forums/s2000-mo...-hfc-s-842575/
70mm and 63mm HFC use the same core so flow through the core is not a problem.
The problem is the big step down in diameter from 70mm to 60mm, this causes lots of turbulence and hurts performance.
Read through Gernbys thread linked above it's very good information, clickable link: https://www.s2ki.com/forums/s2000-mo...-hfc-s-842575/
Joined: Aug 2012
Posts: 8,759
Likes: 1,861
My winter car is an Infiniti G37. With that car, just fitting a pair of hfc's yields a pretty decent power increase (and uncorks a nice amount of sound). Just bolting them on its an instant increase.
Its like that for many cars. But not for the S. Its so well tuned from tbe factory, rhat fitting aftermarket parts often yields a reduction in power, or adds so little its barely perceptible, and cost $1k+.
But, if you fit a correctly sized hfc, AND add tuning which lowers vtec, you get a very healthy boost in mid range power. The key is the lowering vtec rpm, which requires a tuning solution such as Flashpro.
The hfc itself doesn't add any power. And, you can lower vtec rpm with the stock cat, however that combination will actually lose power. The reason is an inherent resonance that occurs with the stock cat. Its not that the stock cat is too restrictive, its just the shape happens to have this resonance, and the shape of aftermarket hfc's happens to have a whole lot less of it (and a test pipe has virtually none). This allows lowering vtec rpm without loss of power.
If you aren't going to add a tuning solution and lower vtec rpm, then a hfc is almost worthless with this car.
However a hfc with such a tuning solution is the best bang for buck power increase available for this car.
Its like that for many cars. But not for the S. Its so well tuned from tbe factory, rhat fitting aftermarket parts often yields a reduction in power, or adds so little its barely perceptible, and cost $1k+.
But, if you fit a correctly sized hfc, AND add tuning which lowers vtec, you get a very healthy boost in mid range power. The key is the lowering vtec rpm, which requires a tuning solution such as Flashpro.
The hfc itself doesn't add any power. And, you can lower vtec rpm with the stock cat, however that combination will actually lose power. The reason is an inherent resonance that occurs with the stock cat. Its not that the stock cat is too restrictive, its just the shape happens to have this resonance, and the shape of aftermarket hfc's happens to have a whole lot less of it (and a test pipe has virtually none). This allows lowering vtec rpm without loss of power.
If you aren't going to add a tuning solution and lower vtec rpm, then a hfc is almost worthless with this car.
However a hfc with such a tuning solution is the best bang for buck power increase available for this car.