Open headers vrs. full exhaust

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360dartgts

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I am kicking the idea around to install a set of race ready electric cutouts on my '69 Dart for raceday. Anyone have experience in power change with the cutout vrs. full exhaust?
 
Unless your build in such a way to take advantage of it you won't see a thing.

Let me clarify……

Lets say you have a 360 with a nice street strip build…….. And you already have a good exhaust system….. Like TTI headers with a 2.5" x-pipe system dumping into some free flowing mufflers…. You probably won't see much if anything.


Really… We need more info.


Electric cut outs would be nice if your system is choked down for nice quiet street driving and you want to open it up for race day.
 
My duster runs the same e.t.'s through the complete exhaust or with the cutouts open at the strip..just a LOT louder...
 
As mentioned above, it all depends on "your car" and the way the cut outs are designed, the exhaust has to flow smoothly. If the cut outs and exhaust aren't designed correctly, you can cause turbulence in the exhaust and it can actually be slower.
 
I've had the opposite experience. When I take the exhaust off my amx I have to jet up 4 sizes to reap the benefits of .15 in the quarter.

The exhaust on my amx is 3 1/2inch to an xpipe then out with 3inch.
 
Consider your exhaust system as a part of your tuning. If you run open headers or have too LARGE of a system, you could take the bottom end torque out of your motor and actually run slower....... (Seen it)
 
I have a 410 in my Dart with a 4spd. 507hp/504tq I stepped TTI headers going thru full 3" exhaust with H Pipe and DYNOMAX mufflers out the tips. I installed a set of Cut outs and I believe the car is quicker with them SHUT! I have not took it to the track as of yet but it doesn't come on as hard with them open. I have exactly 18" from the collector to the tips before the exhaust hits the atmosphere. It sure sounds mean when you open them up!

410 stroker motor 010.jpg


410 stroker motor 003.jpg


410 stroker motor 005.jpg
 
Mad, that is a thing of beauty. Looks very well done.
I normally hate the idea of cutouts because of all the problems I see with them. But that looks really good!

How are the electric cutouts holding up for ya so far?
 
I question wether the cutouts are as good as true open headers,I have seen other questions about this as well form racers.The few guys I know who unbolted their exhaust completely ran faster,but a couple guys who installed cutouts didnt see anything significant?.These were relatively fast cars-(11s to 10s)-Ive never ran uncorked becuase I drive to and from the track.
 
IMO the only time cutouts would benefit, is if your pipes are too small for your engine, in the same case, if you have had your pipes tuned for lower cruising conditions (which would restrict flow in the higher rpms). Because if your pipes were already the right size, or too big, cutting the exhaust off early with cutouts won't change a thing. It will make it sound beastly though 8)

I could see where the turbulence could cause a problem if they are a bad design. And I agree with Revhendo, if you haven't took the time to learn how exhaust comes into play, I really recommend checking out this forum post. http://my.prostreetonline.com/forums/archive/index.php?t-1639.htm
 
POS Dakota said:
Mad, that is a thing of beauty. Looks very well done.
I normally hate the idea of cutouts because of all the problems I see with them. But that looks really good!

How are the electric cutouts holding up for ya so far?
Click to expand...

Thanks for the compliment. I did all this myself in about 6 hours without a lift. Probably would have took 2 hours with one!!

They work just fine and it sounds mean as all get out with the flip of a switch which is cool. Would I do it again?? Probably not....

I will see if they affect times if I ever get time enough to take it to the track
 
The guys that aren't seeing any changes are you just removing the exhuast and not seeing a change or are you jetting up and still not seeing a change?

I'm under the impression a jet change would be in order....

I think you would see exhaust in nhra stock and super stock if there was anything to gain. I realize those engines aren't stock but still...
 
well also it has to do with the length of the headers and collectors, and cam. because with and without an exhaust will change the wave characteristics bouncing back and forth from the cyl to the headers/collector flange...
 
I have raced and dynoed my Dart full exhaust and open cutouts without any jet changes. Picked up 30lbft of torque, no hp gains. Track numbers were about the same 12.80's with my 60fts a little better..Figure the times and mph were same because of leaning out on the top end...
64 Dart w/ street 360,eddy heads,solid cam,airgap,750dp. exhaust-hooker 1 5/8 full length headers, 2 1/2" summit x pipe,dymomax ultraflows,tti tailpipes.

Hope this helps
Bob
 
Cut outs are cool for when you want to scare the fart pipe ricers next to you at red lights that keep revving up their lawnboy engines and looking at you with great eagerness and anticipation, not realizing that they are about to get their *** handed to them.
 
tubbedamx said:
I've had the opposite experience. When I take the exhaust off my amx I have to jet up 4 sizes to reap the benefits of .15 in the quarter.

The exhaust on my amx is 3 1/2inch to an xpipe then out with 3inch.
Click to expand...

Are you dropping the exhaust at the track??...you'd deffinately see a gain if jetted correctly..but he's talking about through the dumps...
 
stroked 340 said:
Are you dropping the exhaust at the track??...you'd deffinately see a gain if jetted correctly..but he's talking about through the dumps...
Click to expand...

I don't drop all the exhaust, I just pull the mufflers. That leaves headers to merge collectors into an x-pipe and a little bit of pipe leaving the x-pipe.

I still think through the dumps there something to be gained if its jetted correctly...Like anything take it to the track and have some fun
 
tubbedamx said:
I don't drop all the exhaust, I just pull the mufflers. That leaves headers to merge collectors into an x-pipe and a little bit of pipe leaving the x-pipe.

I still think through the dumps there something to be gained if its jetted correctly...Like anything take it to the track and have some fun
Click to expand...

You might be right,next test and tune i'll be playing with the jets..:thumblef::thumblef:
 
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