Cobra Exhaust HP Loss Explained, Please?

[user 773]

I know there is a thread out there on exhaust and eveyone's opinion on which is "the best". Having set my heart on the "look" of the Cobra slashcut slip-ons, I was wondering if anyone can explain (with data/details) why the Cobra (reportedly) drops your HP.

Too restrictive? Too free flowing?

Do you run rich or lean after install?

Can the HP loss be corrected with a jet kit (Cobra or other)?

I am not a big fan of the "sport bike" can look on a VMax (personal taste, to each his own) and would really like to replace my megaphones with the "hot rod" look of the Cobras.

Finally, for Cobra owners out there (and I know you are out there 'cause I've seen how nice the pipes look installed), what has your ACTUAL experience been with these mufflers? Performance? Sound?

As always, you all ROCK!

DS

 

[vmax190]

I gained hp and the sound is unreal

 

[4gasem]

I haven't seen a Cobra bike over 105 but granted I don't see them all... 2 of them were 95bhp. My bike with the needles spaced up one and one size larger jet made 122BHP and then 124 with Morley's kit which doesn't look like much but it's WHERE it makes the power and WHEN that counts...

Most lose HP over stock because they are too restrictive. You will actually have to go down a jet size to keep the AFM right.

Cool looking (one of the best IMO) but not worth the power loss. Take a look at what Exactrep has for sale. They have some slash systems too.:eusa_dance:

 

[user 773]

I haven't seen a Cobra bike over 105 but granted I don't see them all... 2 of them were 95bhp. My bike with the needles spaced up one and one size larger jet made 122BHP and then 124 with Morley's kit which doesn't look like much but it's WHERE it makes the power and WHEN that counts...

Most lose HP over stock because they are too restrictive. You will actually have to go down a jet size to keep the AFM right.

Cool looking (one of the best IMO) but not worth the power loss. Take a look at what Exactrep has for sale. They have some slash systems too.:eusa_dance:

They do, indeed, but I forgot to mention that $$$ is also a factor. I would consider the Marving setup if I sould get one at a reasonable price...

If the Cobras are truly more restrictive than stock, would drilling out the recessed cap inside each one restore the stock flow? I realize I would also be risking a possible degredation to the sound by doing so...

The whole A/F dynamic is such a mystery to me... For example, if airflow is restricted, how does more fuel (which in a carb is pulled through by airflow, no?) get into the system??? I could understand this if the intake was restricted... Like I say, I would like to figure out how to have the look of the Cobras without losing HP and in order to do that, I guess I need to study the physics of carburation...:ummm: I would also like to be able to eat, have shelter, etc, and therefore can't lay out $1,000 for mufflers...

 

[44 magnum]

If the Cobras are truly more restrictive than stock, would drilling out the recessed cap inside each one restore the stock flow? I realize I would also be risking a possible degredation to the sound by doing so...

Hey Bro, I can't give you hard data regarding the a/f ratio or dyno numbers, but I what I can tell you is drilling out the caps made mine sound even better in my opinion. I drilled (3) holes in each of the pipes' caps (12 holes) using a 5/16" bit. (Obviously I visually spaced them 120 deg out of phase so they'd look okay even though you can't really see them unless you're looking for them.)

Then I took a really long 9/16" bit and drilled out the bottom plate of each of them. I was really afraid it would be way too loud but thankfully it's not.

I hoped it would 'lean' the motor out quite a bit, but the f'er still runs rich.

 

[user 773]

Hey Bro, I can't give you hard data regarding the a/f ratio or dyno numbers, but I what I can tell you is drilling out the caps made mine sound even better in my opinion. I drilled (3) holes in each of the pipes' caps (12 holes) using a 5/16" bit. (Obviously I visually spaced them 120 deg out of phase so they'd look okay even though you can't really see them unless you're looking for them.)

Then I took a really long 9/16" bit and drilled out the bottom plate of each of them. I was really afraid it would be way too loud but thankfully it's not.

I hoped it would 'lean' the motor out quite a bit, but the f'er still runs rich.

What I don't understand is how the Cobras (stock, no holes drilled) can "sound" better by all reports and yet be more restrictive????

....sigh. :ummm:

 

[4gasem]

My suggestion is to start a little savings account and start saving for a true system. The best sounding slip on IMO is the Super Trapp. Best looking is the Cobra.

Kerker, Marks and Walkers seem to perform pretty evenly across the board. I don't count UFO... lol :damn angry:

I think the Cobra's have smaller primary inlets or something... Maleko89 knows...

 

[maleko89]

Yeah, cores and inlet size are pretty damn small.

 

[user 773]

My suggestion is to start a little saving account and start saving for a true system. The best sounding slip on IMO is the Super Trapp. Best looking is the Cobra.

Kerker, Marks and Walkers seem to perform pretty evenly across the board. I don't count UFO... lol :damn angry:

I think the Cobra's have smaller primary inlets or something... Maleko89 knows...

...ah-HA! That would explain why drilling the end caps would have no effect on the A/F...

Why would Cobra make a pipe look that badass if it decreases performance?!?!?

...sigh v2.0

 

[user 773]

Yeah, cores and inlet size are pretty damn small.

So nothing short of modding the !#*&! out of the Cobra mufflers would match stock flow...

Bastards... :bang head:

 

[maleko89]

Yeah, you could pull the baffle but it would be pretty loud.

 

[user 773]

My suggestion is to start a little savings account and start saving for a true system. The best sounding slip on IMO is the Super Trapp. Best looking is the Cobra.

Kerker, Marks and Walkers seem to perform pretty evenly across the board. I don't count UFO... lol :damn angry:

I think the Cobra's have smaller primary inlets or something... Maleko89 knows...

My little savings account is going towards a Morley overhaul...

 

[user 773]

Yeah, cores and inlet size are pretty damn small.

Another question...

Aren't the Cobras a 4 into 4?

 

[Noxx72]

Well I'll be damned, that's what's wrong with my 2001 Max. I just got it last week, and I've been thinking "this seems a bit rich rich and stumbly in the low / mid". Sure enough, the "custom" pipes that were one the bike when I bought it are the Cobras mentioned above. Sonnofa.....

 

[user 773]

Well I'll be damned, that's what's wrong with my 2001 Max. I just got it last week, and I've been thinking "this seems a bit rich rich and stumbly in the low / mid". Sure enough, the "custom" pipes that were one the bike when I bought it are the Cobras mentioned above. Sonnofa.....

Well, if you want to get rid of 'em.... :biglaugh:

Speaking of A/F ratio, am I already rich @ 4000ft. above sea level with stock jetting?????

 

[Noxx72]

Well, if you want to get rid of 'em.... :biglaugh:

Well I'll admit they look nice, and they do sound fantastic. I'm going to assume the previous owner didn't re-jet for them. It's nice to have an answer fall in my lap tho, as for the last few days I've been asking myself "Am I paranoid, or is this sucker rich?".

 

[kozy]

I know that a lot of people aren't fans of UFO, but they do make an exhaust that looks almost identical to the Cobra's and I'm sure would sound a helluva lot better.


Has anyone ever heard of Kerker making slip-ons? I swore I saw a pair of Kerker slip-ons on eBay the other day.

 

[vmaxfast]

Yes kerker makes a slip on Have a set just setting in the garage they do sound nice even better when you pull the wrap off the baffles.

 

[kozy]

Yes kerker makes a slip on Have a set just setting in the garage they do sound nice even better when you pull the wrap off the baffles.

Sitting in the garage....on the bike or collecting dust?
I wonder how close the sound is to that of the Kerker 4-1 if you put comp baffles in it.

 

[vmaxinID]

I know there is a thread out there on exhaust and eveyone's opinion on which is "the best". Having set my heart on the "look" of the Cobra slashcut slip-ons, I was wondering if anyone can explain (with data/details) why the Cobra (reportedly) drops your HP.

Too restrictive? Too free flowing?

Do you run rich or lean after install?

Can the HP loss be corrected with a jet kit (Cobra or other)?

I am not a big fan of the "sport bike" can look on a VMax (personal taste, to each his own) and would really like to replace my megaphones with the "hot rod" look of the Cobras.

Finally, for Cobra owners out there (and I know you are out there 'cause I've seen how nice the pipes look installed), what has your ACTUAL experience been with these mufflers? Performance? Sound?

As always, you all ROCK!

DS

Hey neighbor!

If you dig deep enough thru this forum you will read I have a "loaner" set of Cobra 4-4's up for grabs.

I live in Pocatello and I will be down in SLC on Nov 6th. in the EARLY morning to fly to Florida.

You wanna "demo" them over the winter let me know.

Plus we gotta get started on the South Idaho/ North Utah Ass kickin' Picknickin' party! (Summer 09!!!)