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View Full Version : Removing baffles in Corsa exhaust tips?



Jamesbon
05-22-2007, 07:46 PM
Yes, I know, already searched and found that "a machinist can remove 'em easily" or one can simply order new ones.

I'm crafty and want to know how the machinist does this so easily.

I took 'em off tonight, started grinding the internal welds, then got pissed and threw them in the bed of the 'ol Ford for the machinist to work on tomorrow. Seems if one had a 3 7/8 hole saw you could "simply" drill through. Then the challenging part would be getting those circular plates out which are larger than the I.D. of the tip.

...If I only had a mill in my garage....

slamdry
05-22-2007, 08:24 PM
why dont you just buy a set of plain tips off ebay and then reself the baffled ones, they go for some decent coin used.

mrfixxall
05-22-2007, 10:08 PM
Two words,plasma cutter! thats what i used in the past...Now i just replace them..

Jamesbon
05-23-2007, 07:57 AM
...cuz i want instant gratification. :)

Dropped them off at the machine shop this morning. You're right on the money mrfixxall. He said he'd "sneak in there with a plasma cutter." Piece of cake.

I was also hesitant to buy new tips then possibly have to drill new holes and such. This way I bolt them back up in exactly the same place and no waiting for new parts to arrive. I have a THREE day weekend staring me in the face :yes:

Thanks for your input fellas!

Donziweasel
05-23-2007, 08:31 AM
I did not like the look of the Corsa's, so I put a set of Livorsi's on. Look great and the bolt pattern is almost identical. They were jus a little off, so I took a dremmel and just enlarged the hole a little on the right side. They have a set of baffles which just screw in. I can take them out in a minute or on more conservative lakes, screw them back in in under a minute.

http://www.livorsi.com/catalog/flaps.htm

http://www.livorsi.com/catalog/flaps.htm#MUFFLER_INSERTS

Alwayz Sumthin
05-23-2007, 10:58 AM
I had the same swirl cans on my Liberator, I also used a plasma cutter and then a die grinder with special bits for the stainless steel and then bolted them back on the boat only to half a day from start to finish and picked up 3 mph and alot better sound. Either way you decide new/used good luck.

Jamesbon
05-23-2007, 11:37 AM
Thanks "Alwayz." I'll be happy with the new sound. I'll do back flips if I pick up some speed!

Just picked 'em up....Can see STRAIGHT through 'em now :) 45 bucks.

...maybe I can leave work early to go tinker....don't tell the boss....

Alwayz Sumthin
05-23-2007, 12:13 PM
007 - no problem, hope all goes well, make sure you use enough sealer to prevent leaks. Enjoy.
Scott

mrfixxall
05-23-2007, 01:41 PM
BTW, make sure the tips have internal flappers in them..If they dont your gonna have to install a set..

Rootsy
05-23-2007, 01:49 PM
i removed them from the 16... bought corsa regular tips.. the thru- bolt holes lined right up with the new holes in the straight tips... no issue...

brivander
05-13-2012, 12:21 AM
I had the same swirl cans on my Liberator, I also used a plasma cutter and then a die grinder with special bits for the stainless steel and then bolted them back on the boat only to half a day from start to finish and picked up 3 mph and alot better sound. Either way you decide new/used good luck.

So I'm reviving this from the dead...what liberator do you have (had?) and what engine? I've got the 221 with a 502 and am planning on doing, but the 221 tips of course aren't standard they are oval and Cora's wants over $400 to make custom tips. I have stainless marine manifolds and with the exhaust setup on this boat (down and out to the sides) I can't image back flow being an issue. 3mph seems unreal!? Was that a heavily worked over motor? I've got to believe this are killing some power for me I'd be tickled to gain half that, I'm seeing just over 67gps with my worked over mill (new this year, 539hp on the dyno) and am just getting it dialed in. If you are still around let me know.

Carl C
05-13-2012, 05:52 AM
His profile says that he hasn't been here for 2 years. I thought this was a new thread until I saw Rootsy's post. :)

brivander
05-13-2012, 07:44 AM
Ah, I can't get to his profile, I hate to bring back ancient threads, but figured he may even have the same boat. Worth a shot, I'm just going to pull them and have them cut out I know this is a fairly slow hull but it seems like it should run a bit quicker, it pulls though the midrange like crazy and feels like it hits a wall at ~65 and creeps up to just over 67, on the dyno we saw no such thing at the rpm I'm running. I need to step up 1" in pitch on the prop as well to bring the revs down a bit.

Carl C
05-13-2012, 07:57 AM
Bringing up old threads is no problem. It's kind of cool sometimes. Just giving you a head's up not to hold your breath waiting for a reply. :)

brivander
05-13-2012, 12:32 PM
LOL. Trust me, I'm not holding my breath! I've found some really useful stuff on this site and have only really chimed in one other time about OMC outdrives, since I don't have a Donzi. That being said, anyone can feel free to contact me for donations :) Figured others may have some ideas too, worth a shot anyhow :)

I re-read my original reply and I sound like a retard, that's what I get for typing it on my phone :boggled: My english is typically better than that!

brivander
05-13-2012, 08:37 PM
It's a 1992 221, the newer style. This boat ran 63mph on the stock 502 (stock with Stainless Marine manifolds), I'm running a 21" Ballistic to about 5300 (the KC I have is a 1.43 ratio). I also have a 22" Raker and a 23" Ballistic. I'll change to the 22" prop and try it since I made peak power at ~5150. I am going to have Bblades do a prop for me but not until I make the rest of the changes...seriously something is choking it off and the only thing restricting it are these baffles (was dynoed in full trim with wet exhaust), it pulled strong up to 5500 on the dyno, where it was only down 18hp from peak. I tried cracking the engine hatch to make sure it was getting enough air, no change. I have the same phenomenon with the stock 20" Raker it starts at the same RPM but obviously a lower speed.

EDIT: fuel pressure is solid the whole way up the RPM range.

I have no delusions this is a fast hull, but there is clearly a restriction. Time to uncork the tips and go from there.

FYI a 211 was my last boat :)

brivander
05-14-2012, 07:36 AM
Interesting, that's the first negative comment I think I've ever heard about Bblades, I'll keep that in mind.

Ghost
05-14-2012, 08:41 AM
I don't exactly understand how a dyno creates resistance to to the motor, and how much resistance it gives, or when/whether it varies. And thus I don't know how a motor "tops out" on RPM when run on a dyno. Does it run up to a set RPM working against a set resistance, so long as it has the torque to get there? Or something else?

But I ask because you said your motor made peak power at 5150. And it thus would have made peak torque below that, right? And so wherever it made peak torque, it was falling off in torque ever since, all the way to 5500 RPM on the dyno, where torque had fallen so far it was now 18 HP under peak HP, despite the increase in RPM. (HP = RPM x torque / 5252)

So when actually pushing the boat, won't the motor climb in RPM until it reaches a point where the torque required to go faster starts to exceed the torque it is already putting out? Such that like you observed, somewhere in the range of RPM where torque is falling, it tops out?

Put another way, why would one suspect there was anything abnormal here at all, with exhaust flow or anything else? If the motor made peak TORQUE up at 5500, that'd be different. But you're topping out with your torque falling off, just as one would predict.

After all, based on the torque needed to push your particular boat over the range of speeds, every motor has to top out somewhere. If way overpropped, that could even be before peak torque is even reached. But propped correctly, it will be somewhere after peak torque. And thus the only way to find out where it will top out is by actuallly testing with the actual boat (the dyno can't know or show or measure where that will happen). All you can see on the dyno is what the torque curve looks like, and thus in what range topping out will happen (somewhere fom peak torque to something higher).

Since it sounds like you are hitting the wall at about the same RPM with multiple props, doesn't that further suggest this is likely the case? You're just running out of torque?

Just trying to think this through,

Mike

brivander
05-14-2012, 09:56 AM
I don't necessarily disagree with your thought's with the exception of the props -- if you lower the speed of the boat (by going from a 21" to a 20" prop) at a specific RPM, it does requires less torque and it's still "hitting a wall" at a specific RPM not really sure how to describe it other than that, it's obvious in the boat. If I put the 22" prop on and lower the RPM we'll see if this still occurs. The point being, it feels like something is holding it back, maybe nothing is wrong at all, but it sure feels like it. Seeing that somebody else hacked out these baffles in this thread and picked up significant speed would verify that if it was real world #'s.

Either way, by taking the baffles out I can confirm if that is happening or not fairly easily, and I don't mind the extra noise. I'll change to the 22" prop, then I will cut out the baffles. If the 22" prop lowers me to a point in RPM that I'm flowing less exhaust volume, that may help as well. I don't want to change to many things together.

Ghost
05-14-2012, 10:12 AM
I agree completely in principle about the different props requiring different torque based on pitch, but I wasn't sure how clear and how close in RPM that wall was with the two different props. (Plus, if torque is falling quickly, and with vagaries of slip and other things, I can imagine running out of torque could still happen at or close to the same RPM for the two props.)

Now I'm curious, just how crisp is the wall you're hitting? Sounds silly asking, but worth eliminating the simple--do you have a rev limiter? I can imagine if you do, they might bump it way up for a dyno test, to explore what the motor will really do, and then send it home with the limiter set a little above peak HP. I know, it'd be crazy for it it be that simple, but just an idea. (Of course, it'd be awesome if what you needed was not more exhaust flow but more pitch. :))

Regards,

Mike

brivander
05-14-2012, 11:27 AM
It's not a rev limiter, because I don't have one :) It's feels like it just lays over. My mechanic at work is going to cut them out for me this weekend with his plasma cutter, so I won't even try the 22" prop until then.

I'm not expecting miracles here, but if I gain a few mph, we'll know pretty quickly :shades:

brivander
06-04-2012, 09:20 AM
Cut them out and re-ran, over 3mph improvement in speed on GPS, picked up over 200rpm!!!

There were two sets of baffles, so I had to remove the tips, cheapest speed I've ever bought. So glad I found this thread. WOW does it sound awesome now.