Tuner Dope

[nitro_rat]

I had a couple different tuners on the bench today, interesting comparisons...

I used the 225PM tuner as a "baseline" because all you guys are probably familiar with that one.

459357
225PM bottom, early 1750 integral tuner top. The length is almost identical to the installed length of the 225PM tuner.

459358
225PM top, 2.4 200 "bell" tuner bottom. This tuner is also found in the 150 XR2. It's about an inch shorter.

459359
225PM bottom, 2.5 150/175 long tuner top. This one is a real choker, if you cut it to the 225PM length it is identical in size so don't throw it away!

459360
This one is interesting. 225PM bottom, 1981 2.0 150 top. Identical except the 2.0 tuner doesn't have the exhaust relief holes. I don't know what other motors this tuner came on but it's a good one!

It's interesting that the basic length for performance applications stayed the same throughout the run. The exception is the 2.4 200 "bell" which falls a little bit shorter. I don't have a 280 style oval tuner or a Bob's to compare, those are the other styles you might be likely to come across. I do know that the Bob's won't fit in the can with the liner in place.

[Merc 2.5]

I got one those 150 tuners from 81 150 and I thought sumone swapped it for short one but I guess not. Thanks for the post. think I'll go drill a few holes in it now haha

[mach351]

I remember pulling one of those tuners out of an Xr6 150 and literally laughing out loud.

[nitro_rat]

I got one those 150 tuners from 81 150 and I thought sumone swapped it for short one but I guess not. Thanks for the post. think I'll go drill a few holes in it now haha

As long as you don't need the extra relief it will work better without the holes!


I remember pulling one of those tuners out of an Xr6 150 and literally laughing out loud.

Yeah, the XR6 had the long tuner. This one came from a 2.5 175 EFI. It's funny that the XR2 was a hot rod 2.0 but the XR4 and XR6 are neutered 2.4's and 2.5's!

[Kennay]

Any thoughts on whatever tuner would be in a 93 2.5 200?

[Chaz]

As long as you don't need the extra relief it will work better without the holes!

At idle with the runner underwater, it's a given the exhaust will follow the path of least resistance and make use of the holes.
At WOT do you think the holes ... ?
1) blow exhaust out of them.
2) column speed will vacuum fresh air in.
3) do nothing.

I reckon by the mid-late 90's they figured out that air stalls out in sharp corners ...
In some cases, it will actually go the wrong way. Put a piece of yarn on a wire and move it around inside of a port, collector, manifold runner .. you'd be amazed at what you see .. ;)

Some say that this is a 300 Drag tuner that also came on a few 280's ... :rolleyes:

https://i.imgur.com/oXdj5fpl.jpg

This one is on a 1999 or 2000 .. 280 mid. From what I'm told this is considered the "standard" tuner they settled on .. ( musta ran out of the other ones or vise~versa)
Ex sperts, feel free to chime in ... :)

Gotta love the color of real gasoline .. :thumbsup:

https://i.imgur.com/oBQkM5Ol.jpg

[nitro_rat]

At WOT do you think the holes ... ?
1) blow exhaust out of them.
2) column speed will vacuum fresh air in.
3) do nothing.


Chas, I'm torn between 3 and I don't care...

I do know that if your particular application doesn't require the holes there's no reason to drill them. At "ski" height my old 1750 doesn't always like to idle happily (I have a hydraulic plate) so I'm going to drill some reliefs in the integral 1750 tuner. I'll probably do some smaller ones than the promax style, more like the ones in the 2.5 long tuner.

The old 1750 plate also puts the tuner cooling water into the exhaust stream. I think I'm going to fill those holes and drill some behind the tuner at am angle like the newer plates have. Kinda a 1/2 @$$ dry stack...

Thanks for adding the hi-po tuner pics. I can't afford to play with that kind of stuff!

[tux974]

Chaz, after taken a better look at your top tuner picture looks a bit smaller then a 280/300 drag and what the 225PM SS motor came with. The second picture is a 280 tuner. The smaller tuner were also used on other motors for a reason though.

225PM SS tuner
459370
459371
459372
459373
459374
459375
459380
459369459382
459383
459384

[Chaz]

Chas, I'm torn between 3 and I don't care...

My reason for asking was, your statement about working better without the holes. I think the first reaction (mine too) is an exhaust with a hole in the pipe or muffler .. this can't be good. But in reality, a rusty header or blown out gasket leaks "out" because of pressure in the pipe. A tuner because of it's divergent shape "pulls" exhaust out, from the tip back to the port. I'm sure the hole will "shear off" some of the column, but to really pull air "in".. the hole would need a bump at the leading edge and to send air out it would need a bump on the far side of the hole. Much like how a NACA duct works. So in essence .. #3 .. the hole does nothing to write home about ... in case you ever decide to care .. :cheers:

Mr. Tee,
The mid-can that plate-tuner came out of "has been thru a lot of modification" LOL So I don't know for sure and it's no longer here so I can't measure it .. :o

I do have a pic from the side with the hyroglifics written on it .... :D
When I first saw it, I thought that someone had cut it off a bit haphazardly. Then I noticed the casting flaws in the bell .. and changed from thinking someone had cut that particular one, to ... someone cut one haphazardly, and they quickly put that one into production ... ;)

Chaz = thinking, that's only part of your collection .. :thumbsup:

https://i.imgur.com/qzkW6Lk.jpg

[nitro_rat]

My reason for asking was, your statement about working better without the holes. I think the first reaction (mine too) is an exhaust with a hole in the pipe or muffler .. this can't be good. But in reality, a rusty header or blown out gasket leaks "out" because of pressure in the pipe. A tuner because of it's divergent shape "pulls" exhaust out, from the tip back to the port. I'm sure the hole will "shear off" some of the column, but to really pull air "in".. the hole would need a bump at the leading edge and to send air out it would need a bump on the far side of the hole. Much like how a NACA duct works. So in essence .. #3 .. the hole does nothing to write home about ... in case you ever decide to care .. :cheers:


I'm sure there is some in and out through the holes at some points during throttle opening and closing events but at steady WOT I'm fairly sure the holes are "invisible" to the exhaust flow.

Now to really stir the pot, which tuner is BEST? :D

[Merc 2.5]

Seems like round tuna gonna flow better but hell idk ,, I'd still like to try me 1

[rjdubiel]

For 90% of us, we would not know the difference. That is my opinion. Its like some props that ya run and just guess what one is faster. One may have ya all over the place to keep control and you think that one was way faster than one that just seemed all tame and stable, but once you put some measures to it the slow feeling one was faster. Most of us do not have the equipment to actually know the very small gain or loss of different things. I have a brand new 280 adapter and tuner at home and a hogged out BP one pc plate and tuner. I doubt I would know the difference between the two. Maybe I am wrong.......

[Chaz]

I'm a goin wiff this guy, he got it figgert out ... :eek: :leaving: :D

https://motoredbikes.com/attachments/003-jpg.73161/

[tux974]

Found this custom home made modded tuner in a mid.
Started from this:
459443
To this, 2" shorter: Found it laying in the can bolts fell out or broke.
459444

And the stock Bob's which work very well in many applications.

459445
459446

[powerabout]

I'm sure there is some in and out through the holes at some points during throttle opening and closing events but at steady WOT I'm fairly sure the holes are "invisible" to the exhaust flow.

Now to really stir the pot, which tuner is BEST? :D
Al stoker has data for OMC's and says for top end weld them up

[HStream1]

Last year I was involved in some Dyno Tuner testing of different configurations. And I can say the factory Oval Drag Tuner Made More HP and Torque than all of the factory Tuners tested. We then tested same Oval Drag tuner one ceramic coated and the other Not. And the ceramic coated tuner made 2 more HP and 2 Ft Lb more torque. Would anyone feel that difference in lets say a 1400/1600 lb River rocket Boat? Probably not. But on a Super light Drag boat running 800 ft they would.

Then theres the Top secret Tuner Charlie and i worked on together. Well lets just say its still Top Secret until such time as i decide to no longer plant my Keester in a drag boat ;) :cool:;) .


Now to really stir the pot, which tuner is BEST? :D

[HStream1]

Then theres this thing. 459450