HKS Exhaust diameter

[Nikw91]

A lot of companies like Remark include 3” front pipes with their exhausts.

Naturally, it drove me crazy that HKS charged more and didn’t include front pipes with their exhausts.

According to this video, the HKS Hi Power exhaust starts at factory 2.38” and slowly expands to 2.75” inches.

So a 3” aftermarket front pipe is going to be just about as bottlenecked as with the stock exhaust.

Essentially, you’re paying for a 0.37” (15%) bigger diameter on SOME of the HKS exhaust.

Where a 3” full exhaust is a 0.62” (25%) bigger front pipe and FULL exhaust.

Would HKS bottle neck big turbo builds?

Sponsored

 

[HondaHoon]

The largest bottleneck in the exhaust system is the factory catalytic converter located in the factory downpipe. Of course, I do not have actual data as proof of anything. However, if I were to guess, any of these aftermarket exhaust systems is going to flow adequately for upgraded "drop in" turbos such as PRL, Kuro, Kuro+, RV660.

When it comes to "catback" systems for the FL5. The main things you are gaining are exhaust note, volume, weight savings, and appearance.

Again, IMO, the only part of the exhaust system that is going to restrict flow SUBSTANTIALLY and in turn give you the largest benefit in replacing is the factory downpipe.

 

[Nikw91]

The largest bottleneck in the exhaust system is the factory catalytic converter located in the factory downpipe. Of course, I do not have actual data as proof of anything. However, if I were to guess, any of these aftermarket exhaust systems is going to flow adequately for upgraded "drop in" turbos such as PRL, Kuro, Kuro+, RV660.

When it comes to "catback" systems for the FL5. The main things you are gaining are exhaust note, volume, weight savings, and appearance.

Again, IMO, the only part of the exhaust system that is going to restrict flow SUBSTANTIALLY and in turn give you the largest benefit in replacing is the factory downpipe.

Thank you, but you completely missed my point. It’s pretty common knowledge factory downpipes are super restrictive.

That is why I was talking about the HKS exhaust diameters being the same as OEM 2.38” diameter at the front pipe and then only getting up to 2.75” diameter.

Up until this video, I couldn’t find any HKS exhaust diameter sizing anywhere.

The point was that big turbo builds with upgraded fuel systems on our cars become limited due to back pressure from stock exhaust sizing even with an upgraded front pipe.

So if you have a big turbo build or plan to go big turbo like me, the HKS exhausts will probably not fix any back pressure issues like a true 3” exhaust like Remark would that is 3”from the front pipe back, for example.

 

[HondaHoon]

1. Specify what BIG TURBO you are referring to. G30-825, Kuro+, RV660?

2. Based on this assumption you are going to support this with 2000cc inj. DW430c, Flex w/E85, full engine build, etc. As there are people who install a Kuro+ and choose to be limited on power because they wish to not mess with ethanol, E40, E60 or full E85.

3. I specifically stated, I did not have the data. But if you have any doubt whatsoever that the HKS is going to have any restriction to whatever your power end goal is. Go 3 inches or higher.

4. According to Rampage. You hit the nail on the head with the factory exhaust being restrictive. If HKS is similar in diameter. HKS manufactured their exhaust system to do EXACTLY what I said above.
Improve exhaust note, volume, weight savings, and appearance.

5. 27Won is coming out with an apparent true 80mm system and yes many other brands go 3in all the way back as well. Stick to those.

Based on this information I have provided, and your data. I will answer your question directly. DONT BUY THE DAMM HKS EXHAUST BROTHER!

...smh...wish you the best

 

[AspecR]

Thank you, but you completely missed my point. It’s pretty common knowledge factory downpipes are super restrictive.

That is why I was talking about the HKS exhaust diameters being the same as OEM 2.38” diameter at the front pipe and then only getting up to 2.75” diameter.

Up until this video, I couldn’t find any HKS exhaust diameter sizing anywhere.

The point was that big turbo builds with upgraded fuel systems on our cars become limited due to back pressure from stock exhaust sizing even with an upgraded front pipe.

So if you have a big turbo build or plan to go big turbo like me, the HKS exhausts will probably not fix any back pressure issues like a true 3” exhaust like Remark would that is 3”from the front pipe back, for example.

True the current HKS exhausts on the market won't fix much. Most get the HKS exhaust system for the sound and not necessarily the power increase though. Maybe the latest one they showed will help fix those restrictions. 500whp can be made on the stock exhaust system though so pretty much any exhaust you by nowadays is for the noise.

 

[Nikw91]

1. Specify what BIG TURBO you are referring to. G30-825, Kuro+, RV660?

2. Based on this assumption you are going to support this with 2000cc inj. DW430c, Flex w/E85, full engine build, etc. As there are people who install a Kuro+ and choose to be limited on power because they wish to not mess with ethanol, E40, E60 or full E85.

3. I specifically stated, I did not have the data. But if you have any doubt whatsoever that the HKS is going to have any restriction to whatever your power end goal is. Go 3 inches or higher.

4. According to Rampage. You hit the nail on the head with the factory exhaust being restrictive. If HKS is similar in diameter. HKS manufactured their exhaust system to do EXACTLY what I said above.
Improve exhaust note, volume, weight savings, and appearance.

5. 27Won is coming out with an apparent true 80mm system and yes many other brands go 3in all the way back as well. Stick to those.

Based on this information I have provided, and your data. I will answer your question directly. DONT BUY THE DAMM HKS EXHAUST BROTHER!

...smh...wish you the best

1. I apologize they way I might of came off in my reply. Didn't sleep much due to a teething 10 month old and replied while I was still half asleep so I was probably not in the best mood. LOL

2. I also assumed most FL5 owners know about the OEM downpipe restrictions since it seems like a very high percentage of us void warranty with a downpipe and jailbreak. (especially in south Florida, its rare to meet a untuned FL5) LOL

3. That is some good info on the 27won 80mm exhaust! I will certainly check that out! I had no clue!

3. Yes, Kuro+ or considering even a "smaller" big turbo in the MHI along with all fuel supporting mods with ethanol.

4. This whole post started because a local member with a big turbo set up is having the backpressure issues previously mentioned and wanted a HKS exhaust. It appears neither he, or a handful of others who messaged me on my instagram, knew about the measurements of the HKS exhaust. So I was just trying to inform people who are in the same boat since the information is not readily available on dealer websites.

 

[Nikw91]

True the current HKS exhausts on the market won't fix much. Most get the HKS exhaust system for the sound and not necessarily the power increase though. Maybe the latest one they showed will help fix those restrictions. 500whp can be made on the stock exhaust system though so pretty much any exhaust you by nowadays is for the noise.

Yeah, completely agree.

So when does the stock exhaust start causing back pressure issues? I know of one person around the 500whp having issues and have read a few posts.

Is 450whp or 475whp figures that would really start to benefit from a true 3” exhaust?

 

[AspecR]

Yeah, completely agree.

So when does the stock exhaust start causing back pressure issues? I know of one person around the 500whp having issues and have read a few posts.

Is 450whp or 475whp figures that would really start to benefit from a true 3” exhaust?

It depends on the turbo but probably around the 450whp is when a true 3 inch exhaust starts to come into play. 27won, Functionwerk, Tomei, etc

 

[Evox787]

Yeah! 27 won, and have a bōsōzoku exhaust while you’re at it ! Those teething issues are really something—nothing you do seems to help, for either the parents or the kid.

 

[Nikw91]

Yeah! 27 won, and have a bōsōzoku exhaust while you’re at it ! Those teething issues are really something—nothing you do seems to help, for either the parents or the kid.

What's wrong with the 27 won exhaust?!

Was starting to kind of lean towards Remark exhaust. They seem to be good quality, reasonable and sound good.

And 100%, sucks seeing your little one in pain on top of losing hours of sleep.

Don't hate! Guys that have bosozoku exhausts love them as much as they love their husbands!

 

[HondaHoon]

I vote remark

 

[Evox787]

What's wrong with the 27 won exhaust?!

Was starting to kind of lean towards Remark exhaust. They seem to be good quality, reasonable and sound good.

And 100%, sucks seeing your little one in pain on top of losing hours of sleep.

Don't hate! Guys that have bosozoku exhausts love them as much as they love their husbands!

If it’s 3 inches and good quality without the JDM tax, then I guess none of them are the exact spec you’re looking for. They have strict laws over there, so manufacturers probably lean toward building products that conform to their market.

Here in the States, not every company produces high-quality products, to say the least. And you can’t really say anything negative about it because their fans—and the people who buy the product no matter what—will insist it’s great and that they’ve never had any issues.

Of course, fandom works both ways. If something isn’t JDM or made by a company their community admires, people are quick to call it low quality or a bad investment, even if that’s not really true. Hope you’re little one get better I passed that twice and isn’t funny at all see them how they aren’t regular behavior.

I vote remark

 

[minimedic]

I have the HKS Hi-Power exhaust and can confirm the little area of diameter reduction that meets up to front pipe. And I can also assume it was engineered with the intent that remainder of exhaust would stay stock as the overall majority won't change more than that. Which is true in my case engine wise, so for me it was nice the touch to smooth the transition to 3" dia.

 

[Nikw91]

I have the HKS Hi-Power exhaust and can confirm the little area of diameter reduction that meets up to front pipe. And I can also assume it was engineered with the intent that remainder of exhaust would stay stock as the overall majority won't change more than that. Which is true in my case engine wise, so for me it was nice the touch to smooth the transition to 3" dia.

You switched to a 3” exhaust? You could tell/feel a difference?

 

[minimedic]

Meh, I wouldn't feel confident saying either way. I bought it for sound and look anyways. Any power is a bonus and likely marginal at best. But between HKS exhaust and adding PRL intake, it sounds how it should IMO. noticeable without being obnoxious.

Sponsored