Our housings came from Holset or KKK, the inlet of the exhaust is divided - one side goes to small dia of turbine wheel the other goes to the large dia of wheel. We are only talking .750 difference from outer to inner, the wheel itself it machined with a step in it. These are not the typical housings you find in the automobile field. Our housings can from Holsets race program and they are similar the housing that a low 1,800 rpm L-10 truck engine would have.
Yes, the friction part you are corrrect, there is friction, my point was simply it is less than packed sealed bearing and will last longer.
The water cooled housings, if you don't have ample exhaust gas flow / temperature you just need a smaller dia inlet housing which usally has a smaller dia wheel.
The point was to say "I know turbo engines last longer, but the blower gasoline engines are better suited for offshore performance".
I guess I took the long way around , huh?
Panther - I see you on the river then sometimes!
I have an all seafoam green 32' SeaCraft with Bahamas registery on it. I'll wave when I see you this spring/summer!
Donzi - the reason you see no or little differenrce is simply what you run is very low HP/CUI. When you run high HP engines you will see a slight difference. Our production engines were about 1.1 hp/cui while race engines could be 1.67hp/cui. Don't forget when using closed cooling your water temp is a constant deg also and that is around 220-230 degress up around a turbo. We ran both closed and seawater cooled engines, there with 70-80 deg water coming in you would see a very slight difference. But, I agree with you it makes no difference. I was just responding to someone saying "what about?"
VGT turbos are the mature version of we wroked on almost 20 years ago. It is varing the amount of opening on the turbine side of the turbo to keep exhaust manifold presure high enough the spin the turbo at slow speeds. You need to understand Holset used to build us special stuff years ago just to test and we would have lengthy calls with engineering. What we made was crude and rude but provided test data and worked well for what it was.
Ever hear of compressor stall? We were running an engine at Cummins Eng Co one time and when the boost came up about 62 psi - we heard a boom!!!!
After shutting down and find no damage we tried it again and again and again. It made booms everytime the boost got that high and we would notice the boost would drop in half and if we throttled back and then just brought it up to 60psi it ran great?????
We got Holset on the phone who just overnighted us that turbo and they said "can't be, impossible". Cummins engineers got on the phone and said look "this is happening".
It took Holset 3 days to find someone that relazied that are compressor tips were exceeding the speed of sound, causing sonic booms and going into a stall mode just like a jet engine!!!
I'm going to dig up some old dyno sheets etc and post them here, you guys will be amazed what was being done almost 20 years ago!!!
Full on compressor stall is unbelievably violent. You've just got to cringe at what the thrust bearings are seeing when that happens.
What teams did you work for back then Joe?
Habana Joe: Thanks for posting your insight. This is what the tech section used to be like on OSO. Thanks also to the others who I know have done their homework on this subject.
We have been working with a well known engine builder and racing team this season. I believe this is the first time that a Class 1 boat has been campaigned with a belt driven centrifugal blower on the engine. This is sometimes very rough ocean racing, but lag has not been a problem, because of the belt drive. Under these throttling conditions you might expect belt problems, but they have never broken or thrown a belt.
My point is you can have the efficiency of the centrigual compressor without lag. What you give up in power potential (compared to the turbo) is not as important as the ability to throttle and besides, the maximum power in the class is limited in two ways, by a restrictor and by the threat of dyno testing by the sanctioning body. You also get to have a huge intercooler on top of the intake, since the blower is mounted in front of the engine. This is important since octane is also limited in the class.
Turbo vs. positive displacement blower? Maybe the belt driven centrifugal can bridge the gap. Depends on your application.
Guys thank you also, very nice to talk to a group that understands technology (even if it 20 yrs old, ti still the same problems)
Who did I work for - I started a company called AMT which did hi-po work for Navistar on the 6.9 L, then we did the 7.3L and we marinazied both of them as well. We then moved over to Cummins who had just started to marinize the B 5.9 engine.
At that time Yashiro Kitami started a boat company called Super Hero and wanted some hot rod diesels for smaller boats. They took over my AMT gave me % of (the only person with a peice other than Kitami) Super Hero Racing Development. The rest is history, I will upgrade my memebership tonight and post interesting reading from years ago!!!
Our job was to push the diesel envelope with current production iron so to avoid the high cost of the Seatek engines. At that point Cummins wanted to market the hot rod engines as baby Seateks. Well you know how that went, lot history behind closed doors!
Cummins 5.9L - the best, we had 600 hp versions with the 2 valve heads!!!! Two major problems with hot rod B's:
1) oil cooler is mounted on the side of the block of clylinder between#1 , it restricts the flow of water around that hole causing over heat. Every overheat score will be either number 1 or 2. Remove the cooler and mount remote, it is very hard to do but saves alot of blown motors. That lesson took 3 engines to figure out!!!!
2) the head gasket was very thick and the pistons actually cleard the block deck. Fire got around them and caused swelling of the piston top. The pistons tops would hit the deck when they rocked o the down stroke - that first knick would spell the beginning of the end!!! take the pistons out and cut a 10 deg tapered going .200 down from the top. The piston can rock and swell but never hit the sides. That costs several engines as well!!!!
Someone asks about the overdrive boxes. We made them from scratch but later played with a very cheap easy version of them. Lenco who makes the planet gears sets all the drag cars have in them has/had an in-line reduction unit. Take that and turn it around it's now overdrive!!!! It is a closed box, so make a hole in the bottom and use a reseve oil tank with a little 12 V pump to circulate the oil and run it through a cooler!!! It worked like a charm!!!!
Now to dinner with the kids and talk to you guys later -
Hey - thank you all for listening. I've moved to a fishing boat the last 6 years with the kids and just can't shake the desire to go fast in big water again - someday!!!
The problem with using a centrifugal blower in a driven (rather than turbo application) is that the boost is proportional to speed, this means that the low speed boost is poor when compared with a conventional supercharger.
You are right in that the efficiency of a centrifugal blower when on boost is significantly better than any rotating lobed supercharger but you do lose out on low end boost unless you have a variable speed ratio to drive your centrifugal blower. I'd imagine this would affect your on to plane performance compared with a coventional blower.
Variable drive ratio blowers are being developed (we're developing one at our company at the moment) but these are all being aimed at downsizing engines in the European market. eg 2-3l high boost and fast response.
On the variable turbo point: you need to have a variable area turbine so that you can get the power out of the turbine over a range of gasflows (so you can improve the boost in the low speed region) but it helps if you have a variable compressor too otherwise your shiny new high power variable turbine just pushes your big compressor straight into surge at low speeds and high boost pressures. Ideally you need to have balanced turbine and compressor capablities.
Great to hear the racing stories, look forward to hearing more!
Yes the new VVT technology makes a huge difference in turbo performance
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