there were a couple of the boats that had people videoing out of them that showed us flying by them that I saw on here awhile back.
There are also huge disadvantages to the turbo though. First, lag, this is not an advantage. In marine envoirments, the turbo lag can add significant problems to plainning time or ability. With advances in transmissions and gearing, this can certainly be helped, but in the performance world, it's yet to be financially feasible for most. Also, lag time certainly comes into account for customer driving satisfaction. Lag comes into play during rough water operation, throttle on/off, as well as rpm limiters, which drops boost. You also have tremendous temps from the turbo's.
When emissions come into play, turbo's also cause issues with Cat light off time, as they can't spool up to create enough heat, and therefore turbo's in auto's are typically pretty dirty for cold starts.
Now comparing roots to turbo is no comparison, but a screw compressor can certainly have significant benefits. The centrifugal did not fix turbo problems, they were able to enhance the lag time, therefore it's better, yet still very, very there. Blower surge, boost drop off are all still there. Yet, you have the parasitic losses so you don't get that extra HP.
From what we see in the automotive OEM, there has been a tremendous surge for turbo's, and now we see a drop and a surge is coming for screw compressors, on diesel and gasoline applications. High boost levels, 20-30psi, smaller engines.
that is the reason we had to spin one engine the opposite direction. the bummer was when we wanted to spin my props in instead of out. think about that one. we had to pull the engines out and put them on the opposite side. it will sure be nice to finally have transmissions in the boat again next summer.
but seriously, I do not think the lag is a big problem, mine did have some lag getting on plane due to a 1-1 gear ratio with a 34' prop, but after that the boost gauge would go up and down about as fast as your hand moved the throttle up and down. if you are saying that a tenth of a second of lag is going to mess people up I dont think so. I think the way a turbo works on load will help when you are getting on and off the throttle in big waves because if you go wide open throttle with a blower before you enter the water and break a drive or transmission because you landed with full hp and with a turbo you enter the water with wide open throttle it will only be half the power for a split second to let the trans and drive not get the shock load of full hp.
and I still say that most people do not know how to apply the situation, and some people may have turbos with way too much lag and there are alot of people out there that are only getting 30 min use out of a turbo and blowing it up, but mine does not have lag and I have the same turbos that we originally built the engines with 5 years ago.
Last edited by BigSilverCat; 11-26-2007 at 05:09 PM.
Hey Tyson, when are you going to let me build you an intercooler/intake/EFI?
Ive run twin turbos in a 30 ft Superboat with two small chevys for 11 years. Motors havent been removed from boat since installed in 1993. Have 1000s of hours on them in Mississippi River. Control the rpms, fuel, boost, hell everything it is the computer age. Use your brain not your check book. Try different things. It might work it might not. But dont wait for Merc to do it. And put some of that 6 figure paint on it. If Merc cant buy it, bolt it on, they wont do it.
Merc is still #1 with me. Where would we be without them.
Turbo's have to be matched to engine size and were the power range is desired. They can be used to boost low mid os high end. They can be matched for torq or HP. The variable geometry stuff can be matched to most all these isssues and sizing can be less of an issue. The variable geometry turbo's can also smooth over dips in the engines power curves.
Power can be had at low RPMs tons of torq. Turb's dont like a lot of overlap or duration lift is more important. Thus the hot cam stresses are not an issue. Economy and emissions are up do to less raw fuel being shot out the exhaust. O f course the guys that just want a lumpy exhaust note your out of luck.
Have seen a lot of big power N/A and blower boats having a difficult time hooking up out of the hole. Used to chuckle about turbo lag vs blower lag at the drags. Blower lag being smoking the begebies out the tires launching.
Can turbos be done cheep ... Well this 6cyl Rambler waggon we did turned 11s in the quarter. Was a daily driver took it to the strip 3 years after the last trip to the strip only didd 13s. After a couple days of scratching our heads changing plugs checking wires , distributor, compression we finally replaced the radiator cap we used as a intake manifold pop off valve and were back into the 11s.
I went with turbos on a boat when after driving my 16' Donzi classic decided I needed mufflers if one wanted to listen to the radio since the only muffler I could find were too big to install in the boat.
All this electronic gadgetry wow. Getting ready to go turbo again after threatning to on mmy last 3 boats. Now with boost referanced fuel pressure regulators, boost referanced timing retard, custom boost referanced carbs I will be whistling once again.
There is no doubt turbos are the way to go, smooth power all the way through if you use the right turbo application. I've played with them on cars for years, can't say much on boats though.........but I would believe it would almost factor the same if you set out and played with it long enough.
I personally drive a turbo diesel (were no new guess powered ones I could SC and tow boat), I also do many computer calibrations for other diesel applications. Were also heavily involved in some direct injected and diesel applications where we've been part of the testing of both, screw and turbo, and the majority of people are now looking for screw compressors as the future. No matter how good a turbo was matched to engine efficiency, optimizied psi's, etc, there is still lag. It's certainly gotten better over the years, but it's still there. Diesel applications make it worse, but it's still there.
In a racing application where acceleration is key, the lag is still typically a problem. Some laugh about traction, but the fastest cars, turbo'd or PD'd work on the traction in order for the car to go faster. To me, it's better to have the power at your finger tips, then not at all. If I want to give the motor/drive 1500lbs of torque at 2000rpm (just throwing # out there), then it's best to have it. The operator is in control of how much power to give the trans/drive by how much throttle is given.
Again, as I said before, the turbo's are incredible, and make mind blowing power levels, something no other force induction method can achieve, but drive-ability and emissions are simply not comparable. They may be plenty good for most consumers, can't argue that, but there is no comparison to drive-ability.
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