Open exhaust Hp gain?

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megacab

megacab

Leglhi
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Seeing what the consensus is on open exhaust.Im going back to the track next week,and would like to pull my exhaust for some et gain.Last time at the track the duster ran a 10.36@130.That was with a full TTI exhaust,3 inch with an x pipe,magnaflow muffs and the rest of the exhaust over the axle and out to tips at the bumper.My question is in my quest for a 9 second time slip would pulling the exhaust give me some more hp?I know that just in weight alone it would have to be good for something,as it weighs a ton.Last time at the track it was 105 degrees,with a 4900 foot elevation.Everyone noticed a 2/10 increase in their et over their normal times from the humidity.Usually the track is @ a 1500-2000 foot elevation.Weather is supposed to be much better this time.Its possible my car might have ran in the 10 teens in better air,so im trying to find every little increase of horsepower.Would it be worth it?
 
dgc333 said:
With a 3" exhaust you won't pick up a lot of power, single digits.
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I agree..I have 3" exhaust on my duster with dumps right after the collectors,car runs the same numbers with or without the dumps open..
 
I'm thinking that every combo is different. Take collector extensions, and maybe some bigger jets. Try to baseline w/ exhaust, then open it, using 18" extensions.
If 100 lbs. is a tenth, that weight has to be worth 5 hundreths.
 
SpeedThrills said:
I'm thinking that every combo is different. Take collector extensions, and maybe some bigger jets. Try to baseline w/ exhaust, then open it, using 18" extensions.
If 100 lbs. is a tenth, that weight has to be worth 5 hundreths.
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I agree, each car is different and at higher RPM's tail pipes and mufflers can take some away.

Also, cut outs and dumps don't help much because the exhaust doesn't have a straight shot out the pipe. The only way they work is if you set it up where the exhaust goes out the collector and strait through the cut outs about 18" from the header with out any obstructions or bends and have your exhaust pipe come off the side of it just before the cut out and curve back from there. But you still have the weight of the exhaust and cut outs.
 
Also, cut outs and dumps don't help much because the exhaust doesn't have a straight shot out the pipe.
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Just curious you've proven this by running your car at the track??..what does your car run for times??...
 
hi, not trying to pour water on your fire, I assume the chassis is certified to run 9 sec ? you have fire jacket, pants, neck collar, shoes, and a FAA physical? I've seen guys touch that magical 9 sec, and not allowed to run till all those requirements have been met. and to get to exhaust, a straight collector does help over a bent style dump. just food for thought.
 
No thats a good question.The car isnt certified for that speed.I have a jacket and just whats required to run in the 10.60 class that i was shooting for.But im not interested in running in the 9's just yet.Im just so close im curious if i can get there with minimal tuning.Once i get that time slip im going to back off and run the class i was shooting for.Its honestly for curiousity and im not going to lie,a little bragging rights for a few of my chevy friends.I was thinking that being it wasnt tuned when i took it to the track,we were all expecting it to be somewhere in the mid to high 10's.When it broke into the low 10's without touching it,the game was on to see if it could run 2/10th's faster.Thanks for the input.It was running a little rich corked up,so i was hoping dropping the exhaust would show some gains.Like i said,if nothing else it weighs a ton.I'll let you know what happens.
 
On my "Brand-X" car which is supercharged, my cutouts produced the same E.T. to the hundredth OPEN as they did CLOSED. It did sound awesome under boost though. :)
 
"It was running a little rich corked up,so i was hoping dropping the exhaust would show some gains." -End quote.

You said you're expecting better air next time out.- That, and dropping the exhaust may take care of that richness without rejetting.
 
stroked 340 said:
Just curious you've proven this by running your car at the track??..what does your car run for times??...
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Why the attitude? You don't know me, you don't know what I have done or not done or where I come up with my thoughts on the subject. When it comes down to it, that is all they are is different peoples thoughts/opinions on the subject.

I don't normally reply to negative comments made on any of the sites I hang out on but I find it a little strange and insulting that you your self said the same thing just a few posts earlier and then you decide to question me?


stroked 340 said:
I agree..I have 3" exhaust on my duster with dumps right after the collectors,car runs the same numbers with or without the dumps open..
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As far as whether or not I have proven this by running my Fish, the answer is no, I just got this car going and I haven't taken it to the track yet. I find it hard to test cut outs on this car though when all I have for exhaust is a pair of bullets and 20" of pipe coming off of that. If all you are trying to do is probe me to see what my car runs then be patient. This car holds a lot of sentimental value to me and I will see what it runs when I get the car where I feel comfortable taking down the track.


My Fish is not the only car I have built though, I have built several cars over the last 27+ years and between them and several friends cars I have found cut outs don't help much unless you set them up correctly. If they have bends or just dump out the side of the pipe, they can create turbulence which restricts the flow of the exhaust and gives you no more benefit over having it go through the mufflers and tail pipes.


My apologies to megacab other members for this rant.
 
Blownfish said:
Why the attitude? You don't know me, you don't know what I have done or not done or where I come up with my thoughts on the subject. When it comes down to it, that is all they are is different peoples thoughts/opinions on the subject.

I don't normally reply to negative comments made on any of the sites I hang out on but I find it a little strange and insulting that you your self said the same thing just a few posts earlier and then you decide to question me?




As far as whether or not I have proven this by running my Fish, the answer is no, I just got this car going and I haven't taken it to the track yet. I find it hard to test cut outs on this car though when all I have for exhaust is a pair of bullets and 20" of pipe coming off of that. If all you are trying to do is probe me to see what my car runs then be patient. This car holds a lot of sentimental value to me and I will see what it runs when I get the car where I feel comfortable taking down the track.


My Fish is not the only car I have built though, I have built several cars over the last 27+ years and between them and several friends cars I have found cut outs don't help much unless you set them up correctly. If they have bends or just dump out the side of the pipe, they can create turbulence which restricts the flow of the exhaust and gives you no more benefit over having it go through the mufflers and tail pipes.


My apologies to megacab other members for this rant.
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No attitude..i'm just asking a simple question if what you say is correct i might try it next season..
 
less resistance= more power, atleast that's how it's been for me. like the other guys said going from 2.5 to 3 inch won't make a huge difference but having cutouts right behind headers will help.
 
stroked 340 said:
No attitude..i'm just asking a simple question if what you say is correct i might try it next season..
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My apologies to you then, I just read it wrong.

There are a few good magazine articles on this subject. unfortunately I don't remember which one, I got tired of all my magazines taking up space and dumped most of them at a swap meet a few years ago.
 
When i tried opening my dumps right after the header we experienced more torque and 006/007 reaction time but no major et gain. If the ext is tuned correctly that might be what you'll find also. but if you can drop your 60 foot time down that does equal major # on your et
 
I ride Harleys and have learned a lot about exhaust from them as it is way more pronounced with only two cylinders. Straight open drag pipes mess with low end torque and jetting. a longer pipe with a small neckdown or baffle makes more power than wide open pipes. I,m sure cars respond the same. I have always run collector extensions and cut them off where they stop burning the paint.the motor benefits from a venturi effect as the gasses flow out and cool. So im in agreement with headers making more power if they are tuned properly with extensions.
 
daredevil said:
I ride Harleys and have learned a lot about exhaust from them as it is way more pronounced with only two cylinders. Straight open drag pipes mess with low end torque and jetting. a longer pipe with a small neckdown or baffle makes more power than wide open pipes. I,m sure cars respond the same. I have always run collector extensions and cut them off where they stop burning the paint.the motor benefits from a venturi effect as the gasses flow out and cool. So im in agreement with headers making more power if they are tuned properly with extensions.
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I agree.
 
daredevil said:
I ride Harleys and have learned a lot about exhaust from them as it is way more pronounced with only two cylinders. Straight open drag pipes mess with low end torque and jetting. a longer pipe with a small neckdown or baffle makes more power than wide open pipes. I,m sure cars respond the same. I have always run collector extensions and cut them off where they stop burning the paint.the motor benefits from a venturi effect as the gasses flow out and cool. So im in agreement with headers making more power if they are tuned properly with extensions.
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Daredevil, best answer to the Question, Thats part of the reason I went with an H pipe with dumps.
 
The TTIs are not a race header so I doubt they will be very good to tune with collector lengths... but you can try. You will lose a bunch of weight tho, and that will always be worth some ET. Pull everything but the tailpipes (wire them well so the tips dont get hammered and the pipes dont wiggle) and I'll bet you can shed 40-60lbs.
 
briankaplan said:
What do you guts think of the dumps after the X pipe?
On the Duster I have opened them with good results.
That way you still get the effect of the X.
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I've been playing with a new setup I put in the car recently. I have Pypes X-Change 3" along with the QTP electric butterflies and their digital controller with an RPM activated switch. I have it configured so the exhaust is running through the mufflers up to 2500 RPM and then automatically opens.

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I haven't run it enough times to determine if there is a difference but it sounds cool. :supz:
 
Thanks for the info guys.Didnt pull it after all,but ran this weekend at the track.It ran pretty consistent and made it three rounds into the final before i broke out with a 10.28@131 on my 10.30 dial.Car ran great,and had 1.44-1.46 60 fts.I wish i had a transbrake haha
 
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