Raceman, please help me pick out best tuner for top speed

[RUNWME]

HEHE I hope I got your attention
Raceman,

I have noticed you say many times that tuners dont effect power. I have also seen where people have said too long of a tuner can bog an engine out of the gate because you have to push the water out of the tuner before it can accelerate well. (especially on heavier hulls with engine mounted deep in the water)

It seems like the best set up would be to saw the tuner off flush with adapter plate. Less weight, and better intitial acceleration when you first stab the throttle.

What do you think? Shorter the tuner the better?

David

[Raceman]

I don't guess I have a good answer to that question, mostly because I've always evaluated my engine modifications by top end reads on a speedo and later Radar and GPS. I saw T Rex doing stopwatch 0 to 40 or 50 speeds at Jasper a couple of years ago and I wish I'd done some of that in the past. I have had a boat that wouldn't get on top because the tuner was jambed in the water when off plane that I fixed by popping holes in the side of the tuner.

There are a lot of contradictions in tuner design if you look at them over the years. Many if not all of the early Merc inlines had NO tuner, but then when Merc came with the Merc 1000 in 1962 it had a very long one. This was the highest horse engine they'd ever built. The Twister and Twister 1's had what amounted to a very long tuner, since the log on the side of the engine exited not far above the gearcase and it was a uniform diameter all the way down. This was a high RPM motor with lousy low end. The T2, which out horsepowered the Twister and Twister 1 and was also a high RPM motor had a shrter tuner than the other 2, but it was still considerably longer than the 1500XS which didn't have the power or RPM potential of the T2. The first T3 tuners were very long and the second ones were not only shorter, but of larger diameter. That's about the time I started foolin' with em a lot and I couldn't tell any difference between the two designs, but again only evaluated em in terms of top end speed and seat of the pants feel. The T4, maybe Merc's highest output race engine was operated in a 7K plus RPM range and it had no tuner at all.

If you cut your tuner off, I think you'd have a better chance of water back up the chest and I also expect that you might feel some difference around the powerband somewhere, but I doubt you'd see much difference on top. I guess I had the same idea that they'd make a huge difference from seeing what simple adjustments to the stinger on expansion chambers would make on an old 2 stroke bike I used to dirt drag, but after years of swappin' for just one more that another person swore helped him, I finally got it through my head that there wasn't any magic there. I recently changed to the newest Toomey chambers on my Yamaha Banshee, and it's surprising the difference in hit over the old pipes, and the differences in sizes and shapes of the cones and stingers and overall length seems marginal at a glance.

I've also found it interesting that the newest Merc tuners are equal lenght on both sides, even though the cyls on one bank are obviously farther from the tips. One of the aftermarket ones I had (Bob's I think) was the same way. Seems like if the length was all this critical as the aftermarketeers would have us believe, it'd be important to have the stagger the same as the height difference between the even and odd banks of cyls.

If I was trying to design an optimum tuner, which of course has to be a compromise at best, I think I'd make it the same cross section as whatever the exhaut chest was cut to and the same length below the bottom 2 cyls as the spacing between the cyls on a given bank.

Unless a tuner is found to be restrictive, which some people claim on a V6 150, I really don't think it's important. I think most of what matters happens a multi cyl engine is in the chest before it ever gets to the tuner.

[mach351]

Hey raceman - wasnt there a guy on here a while back that was messin around with installing expansion chambers on a V6 Merc? Whatever happened to that?

[Raceman]

It was John Lentzkow (sorry if the spelling ain't close John, the hooked on phonics tapes weren't around when I learned to spell). He made an exibition pass at one of the ODBA races in 2002 I believe. I never saw his setup, but I think they said he was pleased with the upper RPM power and the powerband was pretty narrow. I think he was going to do some additional development on it, but seems like I remember something about him quittin' racing. I don't know about the last part, but he was on the bank next to our tent at Jasper in 03 and wasn't racing there if I remember right.

[Markus]

Raceman wrote:


If I was trying to design an optimum tuner, which of course has to be a compromise at best, I think I'd make it the same cross section as whatever the exhaut chest was cut to and the same length below the bottom 2 cyls as the spacing between the cyls on a given bank.



If I remember correctly, that is how Yamaha's race pipe is designed.

[RUNWME]

Thank you for your responce. I was hoping you would say Lop them off and you will accelerate harder with no loss in top end. Seeing as how I have very limited supply of parts, I will just leave them alone :D

Thanks agian, very thought provoking

[tripledude]

I THINK Lentkow's expansion chambers were banned??? Bruce Mason is supposed to be trying them this year on his OMC V8 at the Blarneys Island races in northern Illinois. After playing on and off with the v8 for the past few years, he's supposed to have finally had someone build it who should know what they're doing. In the meantime, Lentzkow has bought a Harley, put a supercharger on it and ridden off into the sunset.

[Dave S]

Thats a good title for any one talk'in about tunna fish.

[Dave S]

Wrong pix