Bolt-on K20 EK dyno: 2.5" vs 3" exhausts - Club RSX Message Board
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Old 07-11-2008, 03:28 PM   #1
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Bolt-on K20 EK dyno: 2.5" vs 3" exhausts

Well, I got done tuning my car.

I put on a Thermal 3" exhaust yesterday, and it made quite an improvement over the previous SMSP 2.5" counterpart.

The solid line is from today (92 degrees in the dyno garage) and the dotted line is the old 2.5" exhaust (73 degrees in the garage).



Now only if I could add some intake length and move that pesky resonance hump further up. Seeing as my chasis is a little more restrictive to intake design with a K20 than RSX's, I may have to get creative one of these days.

Here is the full modlist:

K20A2
Stock from valve cover to oil pan
RBC manifold
11" intake with velocity stack/filter combo
Tri-Y long tube header
3" Thermal exhaust
Tuned with K-Pro on my shop's dyno

As always, comments and question alike are always welcome.
- Derek
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Old 07-11-2008, 03:35 PM   #2
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Looks like I need to go 3inch.

How much tuning was done when you went from the 2.5inch to 3inch exhaust?

Last edited by k24_dc5; 07-11-2008 at 03:38 PM.
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Old 07-11-2008, 03:36 PM   #3
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numbers/graph looks good considering the mods you have
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Old 07-11-2008, 03:40 PM   #4
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Originally Posted by k24_dc5 View Post
Looks like I need to go 3inch.

How much tuning was done when you went from the 2.5inch to 3inch exhaust?
To be honest, it only needed another 5% fuel all over generally speaking. VTEC engagement moved down alot, too, so the high cam VTC map needed ALOT of adjustment.

- Derek
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Old 07-11-2008, 04:14 PM   #5
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wow, good gains
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Old 07-11-2008, 04:25 PM   #6
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who made the header? What size flange on the header? What was the minimum inside diameter of the SMSP and Thermal? Just b/c an exhaust uses a 2.5" pipe, doesn't mean that there aren't parts inside the muffler/resonater that less than 2.5".
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Old 07-11-2008, 04:32 PM   #7
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who made the header? What size flange on the header? What was the minimum inside diameter of the SMSP and Thermal? Just b/c an exhaust uses a 2.5" pipe, doesn't mean that there aren't parts inside the muffler/resonater that less than 2.5".
It's actually the SSR knock-off being sold by Batlground Engineering on K20A.org. I purchased the header when I did the swap a couple months ago.

It is a 2.5" flange outlet.

The SMSP was a true 2.5" inner diameter with Magnaflow straight-through 2.5" ID resonator and muffler. In fact, I am still using the 2.5" resonator section right after the connection to the header, and have to flare up to 3" about 12" past the header flange.

So technically, I have a 2.5" to 3" exhaust.

- Derek
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Old 07-11-2008, 05:28 PM   #8
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Nice gains. Lower air temps would have netted you even more. I dynoed a 3 inch in March and got gains of 7 whp and 15 wtq.

Didn't lose anything on the bottom end either did you? I wonder how many dynos it will take to prove to people that there are gains to be had with a three inch on a stock K20a2?

What kind of dyno is it?

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Old 07-11-2008, 05:34 PM   #9
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Quote:
Originally Posted by luvmyrsx View Post
Nice gains. Lower air temps would have netted you even more. I dynoed a 3 inch in March and got gains of 7 whp and 15 wtq.

Didn't lose anything on the bottom end either did you? I wonder how many dynos it will take to prove to people that there are gains to be had with a three inch on a stock K20a2?

What kind of dyno is it?

luvmyrsx
Agreed, my IAT's were 110 degrees average, and I kept the ECT at 185-ish degrees for the runs.

And no, no losses down low at all. In fact, the car feels a good bit better cruising in the 3,000 RPM range now, and laying into the throttle slightly.

It is a brand-new (as of the end of May) DynaPack Evolution 3000 model.

- Derek
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Old 07-11-2008, 06:41 PM   #10
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Quote:
Originally Posted by D-Rob View Post
It's actually the SSR knock-off being sold by Batlground Engineering on K20A.org. I purchased the header when I did the swap a couple months ago.

It is a 2.5" flange outlet.

The SMSP was a true 2.5" inner diameter with Magnaflow straight-through 2.5" ID resonator and muffler. In fact, I am still using the 2.5" resonator section right after the connection to the header, and have to flare up to 3" about 12" past the header flange.

So technically, I have a 2.5" to 3" exhaust.

- Derek
hah. Good ol Mike. He's no longer with batlground anymore though.

Interesting results. Was the muffler on the SMSP a straight through muffler?
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Old 07-11-2008, 08:48 PM   #11
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hah. Good ol Mike. He's no longer with batlground anymore though.

Interesting results. Was the muffler on the SMSP a straight through muffler?
Yep.

- Derek
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Old 07-12-2008, 01:39 AM   #12
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Yep.

- Derek
Son of a bitch, I can't believe this, I build a head and hit 229 and you add an exhuast and hit 222....bitch :-P
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Old 07-12-2008, 06:10 AM   #13
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Son of a bitch, I can't believe this, I build a head and hit 229 and you add an exhuast and hit 222....bitch :-P
he does have a swap in a civic..they tend to make more power....
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Old 07-14-2008, 02:14 PM   #14
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he does have a swap in a civic..they tend to make more power....
i dont see wut your saying. its swapped but its still a k20a2 with an rbc, velocity stack a header and exhaust. you can have that on an rsx to. so how does it being in a civic make it have more power?
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Old 07-14-2008, 02:17 PM   #15
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i dont see wut your saying. its swapped but its still a k20a2 with an rbc, velocity stack a header and exhaust. you can have that on an rsx to. so how does it being in a civic make it have more power?
I think he means when K20-swapped Civics go on your normal DynoJet, the output is a little higher, as most swapped Honda's lack things like power steering and A/C, and also have smaller diameter wheels/tires, which result in a torque multiplication, thus giving a higher number.

This test was performed on my DynaPack, though, so no wheels/tires were present.

- Derek
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Old 07-15-2008, 10:19 AM   #16
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I think he means when K20-swapped Civics go on your normal DynoJet, the output is a little higher, as most swapped Honda's lack things like power steering and A/C, and also have smaller diameter wheels/tires, which result in a torque multiplication, thus giving a higher number.

This test was performed on my DynaPack, though, so no wheels/tires were present.

- Derek
i see what your saying. thanks.
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Old 07-30-2009, 02:05 AM   #17
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Derek, were both 2.5" and 3" exhausts straight-through? What about resonators? Thanks.
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Old 07-30-2009, 08:20 AM   #18
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wow that is a pretty big improvement
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Old 07-30-2009, 11:22 AM   #19
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Quote:
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Derek, were both 2.5" and 3" exhausts straight-through? What about resonators? Thanks.
Quote:
Originally Posted by D-Rob View Post
The SMSP was a true 2.5" inner diameter with Magnaflow straight-through 2.5" ID resonator and muffler. In fact, I am still using the 2.5" resonator section right after the connection to the header, and have to flare up to 3" about 12" past the header flange.

So technically, I have a 2.5" to 3" exhaust.

- Derek
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Yep.

- Derek
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Old 07-30-2009, 11:24 AM   #20
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nice gains man, i always love your work

but i have question, while back ago, i switched to full 3" inch exhaust with bottle neck on the header flange. and i was surprised my power and torques was dropped so bad. around 10whp and 15wtq after full re-tune. i wonder what is the coz of that ?
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Old 07-30-2009, 11:29 AM   #21
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nice gains man, i always love your work

but i have question, while back ago, i switched to full 3" inch exhaust with bottle neck on the header flange. and i was surprised my power and torques was dropped so bad. around 10whp and 15wtq after full re-tune. i wonder what is the coz of that ?
Hadi,

You need a gradual increase from the header to the exhaust
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Old 07-30-2009, 11:32 AM   #22
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thanx for the quick answer, i do this with my new K24 built.
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Old 07-30-2009, 07:36 PM   #23
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Hadi,

You need a gradual increase from the header to the exhaust
could you explain this to me Mike? i couldn`t understand properly.. do you mean that there shouldn`t be a bottleneck or it should be a setup like Darek`s 2.5" to 3" (having 2.5" resonator than the piping becomes 3"?)

thanks
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Old 07-30-2009, 07:51 PM   #24
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you got three cars??
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Old 07-30-2009, 10:04 PM   #25
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you got three cars??
LOL. No.

This thread is super-old from when my personal car was naturally aspirated.

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