After a couple months of running around at the 211whp/152wtq power level in my K20A2-swapped coupe, I decided it was time to change something and get a little more pep from her.

So, a friend of mine who had just recently gotten rid of his turbo EM1 offered me his Thermal 3" exhaust at a very reasonable rate.

The results speak for themselves, the 3" exhaust made more power EVERYWHERE compared to the 2.5" ID exhaust that was previously on the car.

The solid line is the 3", the dotted line is the 2.5" exhaust.



Once more, this is a stock internal (from valve cover to oil pan) K20A2, and the only mods are an RBC intake manifold, 11" intake with velocity stack.filter combo, and long-tube Tri-Y header, tuned on K-Pro.

I believe there to be more power in the midrange is I could get some more length out of the intake, as the resonance is occurring much too early.

- Derek

 

Nice gains, is it much louder? Oh and get that car to the track

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 96Spec Ek &raquo;</TD></TR><TR><TD CLASS="quote">Nice gains, is it much louder? Oh and get that car to the track </TD></TR></TABLE>

Actually, it's not much louder. The muffler I had before was smaller in dimension than the Thermal. It's much deeper, and about the same volume.

As far as the track goes, it trapped 84mph in the 1/8th on my current street tires in 90-degree heat a couple weeks ago at the 211whp power level.

We'll see what the cooler weather this fall does for her, as well as a set of slicks.

- Derek

 

Thats really nice. Im running a 3" exhuast on my setup.

 

Don't you know with 3" exhaust you'll lose power.

3" FTW.

 

Header collector size?

 

on my k20 setup

i had rbc manifold, short 90* bend intake, rcrew cams, rcrew header, rcrew 3" exhaust, and it made 228whp and 165 torque

3" exhaust on 2.0L

 

this was already proven on k20a.org lol but, its good to see some one post this up on here with a graph. im suprised it made more power throughout the whole graph, i was expecting a slight loss in the lower rpms

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mar778c &raquo;</TD></TR><TR><TD CLASS="quote">Don't you know with 3" exhaust you'll lose power.

3" FTW.</TD></TR></TABLE>

"but you can only use 3" on turbo carz"!!!!111!!
lol

I'm glad to see more and more people realizing that is BS. I don't remember who said but I believe it was a header builder who said "anything past the last collector is just a restriction"

Nice gains

 

3 inch ftw

 

3" + dump =

 

 

wow..big gain between 4 and 4.5

 

Im interested in the collector size also?

Does it go from 2.5 and merge or taper up to the 3in system?

Then i think of all the reverse meagphone set ups that neck down to 2.5 on 2lt + B and K race headers ???

Anyone shed some light on this?

 

3" put a 4incher on there and watch the power climb like no other

 

3" thermal is what I have as well. I'm glad you did the test, I've been telling customers 3" is actually not too large for a long time now.

 

sorry to be off the topic. A built b20 will benefit from a 3' exhaust or 2.5' will be sufficient?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by benson03 &raquo;</TD></TR><TR><TD CLASS="quote">sorry to be off the topic. A built b20 will benefit from a 3' exhaust or 2.5' will be sufficient?</TD></TR></TABLE>

3" &gt; 2.5".

I run 3" on a 1.8L.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Slaz &raquo;</TD></TR><TR><TD CLASS="quote">Im interested in the collector size also?

Does it go from 2.5 and merge or taper up to the 3in system?

Then i think of all the reverse meagphone set ups that neck down to 2.5 on 2lt + B and K race headers ???

Anyone shed some light on this?

</TD></TR></TABLE>

The collector size is actually smaller than 2.5". It appears to be a 2.36" collector, which flares up to 2.5" at the flange. Most 4-2-1 headers don't feature a true 2.5" final collector.

Actually, my exhaust does not make the transition to 3" until about halfway back the car, and still utilizes the 2.5" ID Magnaflow resonator.

- Derek

 

So from the 2.5 magna flow its just mated flat to the 3in system hole?

No flaring or transition as such?

 

D,

Thanks for settling this silly debate. I will ask to get this stickied.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Slaz &raquo;</TD></TR><TR><TD CLASS="quote">So from the 2.5 magna flow its just mated flat to the 3in system hole?

No flaring or transition as such?

</TD></TR></TABLE>

There is a 2.5" to 3" flare in place after the resonator.

- Derek

 

I wonder if the power would increase if the collector was 2.5" and went into a 3" before the resonator. 3" is the way forward non of that backpressure bullshit!

 

Nice results

This is a pretty much a fact 2.0L+ 3" will gain you decent numbers.

 

Some people will still argue 3" is worthless, even after seeing that graph.