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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #21  
Old 02-26-2010
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I think those Bloom Boxs run on strawberry daquiries. Maybe the Wombat can hook his prop up to one of those....
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Old 02-26-2010
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Originally Posted by sailhog View Post
I think those Bloom Boxs run on strawberry daquiries. Maybe the Wombat can hook his prop up to one of those....

Would that mean a pretty pink exhaust ? I'd like that, though the Wombet being a recovering 70's feminist would likely find it too girly.


The issue really is the size of the turbo methinks. I'm coming to agree with the idea that a low boost turbo is an acceptable compromise though I'd still prefer naturally aspirated I reckon.

The ability to maintain is probably not an issue given my overall mechanical ineptitude. The last time I changed the spark plugs and points on a car I put the distributor cap on backwards. Apparently that does not do the engine timing much good for some strange reason.....or so the tow truck driver told me anyway....
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Hiya Fuzzy,
I inherited the engine (oversised) but I try and keep it all clean and lubed and we try to sail as much as we can.
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Last edited by St Anna; 02-26-2010 at 06:30 PM.
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Old 02-26-2010
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Originally Posted by klem View Post
... A moderately sized turbo will do a really good job of providing the necessary air to the cylinder.

... I have worked on a lot of both and the turbocharged engines do not give me any more problems than the naturally aspirated ones.
Klem,

It seems you know a lot about engines.
There is an option to mount a turbo on the engine of my car. I have noticed that the turbo would not bring much more power (138 to about 180hp) but the increase in torque was huge. We can generalize this? A turbo engine will have a substantially bigger torque at working revs?

If so it seems to be a big advantage over aspirated engines, in what regards a marine engine.

Can you tell me if this is so?

Regards

Paulo
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Paulo,

What is the engine that you are looking at turbocharging? Gas or diesel?

I will start with a caution about putting a turbo on engines that were not originally designed for them. If you don't change anything, you will increase cylinder pressure from compressing more air which can have adverse problems such as a blown headgasket. If the engine came with a turbo option, then this should not be a problem. You can lower the cylinder pressures to reasonable levels with a turbo by dropping the compression ratio (changing pistons or a thicker headgasket) but that is undesirable as the engine will not start as well and it will be less efficient. The other option is to try to make the cylinder hold up to higher pressure by putting in stronger head studs, heavier valve spring, and an o-ring in the headgasket. The ultimate diesel to modify is the 6bt cummins (5.9ltr offered in dodge pickups) and if you look at turbodieselregister.com or dieseltruckresource.com, you will see a ton of information on how to keep your head gasket intact.

To answer your original question, it really depends on your setup and whether the engine is gas or diesel. Gas engines are air throttled and stoichiometry (air/fuel ratio) really matters so you have to be a lot more careful with turbocharging. Diesels are fuel throttled and stoichiometry doesn't matter very much except at very low air/fuel ratios which is why we add turbos. Since a turbo is a thermodynamic device, it is a function of the amount of heat energy exiting your exhaust. This is directly proportional to flow rate (rpm) and temperature (egt).

Talking diesels only, the size of your turbo will really determine how it affects your hp/torque curve. The idea is that by forced air induction, you can inject more fuel into the engine. Really small turbochargers will have a large effect at lower rpms and will not provide much air at high rpms because they are out of their efficiency range and are injecting hot air instead of cold air which is not as efficient. This leads to a large increase in torque (lower rpm) and not a large increase in horsepower (higher rpm). A very large turbocharger will not spool at lower rpms but will provide a lot of good cool air at high rpms which results in not a large increase in torque and a large increase in horsepower. Because neither turbo is good at both, you will often see them in series referred to as "twins" which provides good airflow throughout your entire rpm range. If you compare a turbo and a supercharger, the supercharger is really good at low rpm where the turbo is not spooled yet and the charger is really good at high rpm. If you look at a naturally aspirated engine in general, the airflow is proportional to the rpm so the higher the rpm, the more fuel you can burn and the more power you can get.

I should add that what I said above made a few simplifications. I ignored different turbo housing sizes, turbo wheels, etc. Airflow is king in the modern diesel engine as we try to get more power for a given displacement and a turbo plays a large role in that. Boost is simply a measure of resistance in your intake so actually one of the best things that you can do for improved airflow is to port the head on the engine (this is for racing only, not cruising boats). In modern diesel racing, the vast majority of the research is in turbos these days although there is a lot of research in fuel injection and drugs as well.

If your car is actually gas, then the above explanation is true in very general terms but some of the specifics are different. The relative boost range for even racing engines is totally different, ~20psi for gassers versus ~150psi for diesels.

If you give me an engine model number, I can let you know if I know anything about that engine. You can read a turbo map to get in the ballpark but being able to learn from someone else who has already hotrodded a specific engine is much better. Like anything, selecting a turbo is about compromises.
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Quote:
Originally Posted by klem View Post
Paulo,

What is the engine that you are looking at turbocharging? Gas or diesel?

I will start with a caution about putting a turbo on engines that were not originally designed for them. If you don't change anything, you will increase cylinder pressure from compressing more air which can have adverse problems such as a blown headgasket. If the engine came with a turbo option, then this should not be a problem. ...

If your car is actually gas, then the above explanation is true in very general terms but some of the specifics are different. The relative boost range for even racing engines is totally different, ~20psi for gassers versus ~150psi for diesels.

If you give me an engine model number, I can let you know if I know anything about that engine. ....
Know doubt you really know a lot about engines.....

Yes it is a gas engine. A Toyota 1ZZ-FED and the turbo is made by TTE, the guys that make the Toyota F1. It was tested and approved in Japan, by Toyota. That basic turbo plus a more complex tunning can boost that engine to 260hp. Now, I have a 70.000 kms engine, do you think I will shorten substantially the engine live if I mount the original turbo package, I mean the one that brings the engine to a bit more than 180hp?

Last edited by PCP; 02-26-2010 at 08:14 PM.
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Paulo,

I wish that I could say that I knew a lot about that specific engine but I have never worked on one and I don't want to give bad advise for lack of knowledge on my part. I have a lot of experience hopping up diesels but only a bit of experience modifying gassers.

If the package was a factory option, that probably means it was relatively conservative. I would look on the car forums for how the cars with that option have held up relative to the naturally aspirated version. If the only difference was the turbo and fuel program, there will not be a problem with adding those at this stage. Just make sure that the headgasket, studs, etc are all the same on your car as the turbo version. Something to consider is not only will you be putting more stress on the engine but also the rest of the driveline. On a lot of cars, the first thing to go is the clutch or u joints, not the engine. Since all drivers are different, you will see a lot of variability in reliability posted on online forums but there are usually enough people posting that you can get a good idea of whether a certain mod has problems or not.

Good luck. I hope that I didn't take this thread too far off track.
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