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Author Topic: MTDI in a boat  (Read 7955 times)

Reply #105July 03, 2018, 08:09:26 pm

LabradorSteak

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Re: MTDI in a boat
« Reply #105 on: July 03, 2018, 08:09:26 pm »
It was under full load. Jet pumps absorb a certain amount of power at any given rpm. The absorbed power curve is exponential (I think?) so I have been changing the impeller in the jet pump to allow the engine to rev higher. At 2100 with the set up I had I am probably making 40-50hp. I was thinking if I can raise the fuel a little I may start making more boost and I assume that power will follow.  I'm starting to worry that I have too big of a turbo???

Matt

Reply #106July 03, 2018, 09:36:25 pm

vanbcguy

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Re: MTDI in a boat
« Reply #106 on: July 03, 2018, 09:36:25 pm »
Sounds like you need more fuel! Steady state EGTs around 1200F at full power would be quite safe. It does take heat to make boost; your EGTs are fairly low if that is loaded up.

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Reply #107July 04, 2018, 12:25:12 am

LabradorSteak

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Re: MTDI in a boat
« Reply #107 on: July 04, 2018, 12:25:12 am »
I will head down to the ramp tomorrow and turn the screw!!!

Will my egt's continue to increase with rpm or is it directly a function of fuel per combustion cycle?

Will adding more air (boost) decrease the egt's per combustion cycle? (Assuming that the pump puts the same amount of fuel in per stroke irregardless of rpm)

If I keep the fuel down and find a way to increase boost (this is theoretical) is there an upper limit of boost psi or is it just cylinder pressure as a combination of both boost psi and fuel?

Thanks, Matt

Reply #108July 04, 2018, 01:31:04 am

vanbcguy

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Re: MTDI in a boat
« Reply #108 on: July 04, 2018, 01:31:04 am »
It's a bit different in your application than the typical automotive rig. Generally in a car or truck increasing RPMs by down shifting reduces load, and EGTs go down.

Your setup is probably going to be at full power for long periods of time; that's partly why I say 1200F for the EGT limits. If you were in a car you'd never be at peak power for more than a few minutes at most, so you can get away with more - most folks say 1400-1600F for a turbo engine. That's intermittent power rather than sustained though. Different ball game.

EGTs go up with fuel and down with air. Increasing boost lowers EGTs, until your intake air temperatures get too high anyhow. Increase fuel, you'll probably see an increase in boost (considering you have almost nothing now!) - you can turn up the fuel till your EGTs get high, then increase boost to get them back down, repeat until you get the power you're looking for or the boost levels go past what is safe for your engine and turbo.

I can't recall the details of your build now, but 15 PSI intercooled in a steady state with EGTs around 1200F will be safe for anything. You can crank things up from there assuming you have built the engine appropriately.

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1994 Jetta - AHU M-TDI - Jezebel Jetta
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Reply #109July 04, 2018, 01:47:28 am

vanbcguy

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Re: MTDI in a boat
« Reply #109 on: July 04, 2018, 01:47:28 am »
Also, some thoughts...

Are you targeting 2100-2500 RPM? Or is that just the most you can hit with your current setup?

I watched your video above - were the EGTs getting to 740F and stopping there, or did you just abort the test there?

I don't hear any turbo noise really, nor do I see any signs of the silicone couplers taking pressure. At the moment I'd assume you are not making boost.

I too am wondering about the size of your turbo. 2100 RPM is about where a K24 starts to come to life, a GT2052 is about the same size though a bit newer of a design. Can you hit 2800-3000 without changing anything else? Looking back through your posts you were talking about something like 3800 RPM which is quite a lot more air.

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« Last Edit: July 04, 2018, 02:01:35 am by vanbcguy »
Bryn

1994 Jetta - AHU M-TDI - Jezebel Jetta
2004 Jetta Wagon - 1.8T - Blitzen

Reply #110July 04, 2018, 05:52:30 am

LabradorSteak

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Re: MTDI in a boat
« Reply #110 on: July 04, 2018, 05:52:30 am »



Also, some thoughts...

Are you targeting 2100-2500 RPM? Or is that just the most you can hit with your current setup?

2100-2500 is all I was able to hit.  I have the impellers available where I would like alot more power at that rpm and I could put in the bigger impellers and get more power absorbtion which will equal more thrust.  Bigger impellers are like somewhat like having a higher gear (where a higher gear equals more thrust) but you only get to use one gear.  The more thrust I get the more I can cary and the faster I can get on plane.  Also the more thrust I have at any given rpm means that I can cruise at a lower rpm using less fuel and less noise made.

I watched your video above - were the EGTs getting to 740F and stopping there, or did you just abort the test there?
On the pull in the video I probably just stopped but there were pulls where I kept it on until it leveled off and stayed at 740.  I wasnt able to get it more than about 740 ever.

I don't hear any turbo noise really, nor do I see any signs of the silicone couplers taking pressure. At the moment I'd assume you are not making boost.
I am going to use even smaller impellers to see if I can get more rpms under load and see where and if I build thrust.  Unfortunately, even with the impellers I have in there now I would not be able to get on plane because I am not making enough thrust...I need more power.

I too am wondering about the size of your turbo. 2100 RPM is about where a K24 starts to come to life, a GT2052 is about the same size though a bit newer of a design. Can you hit 2800-3000 without changing anything else? Looking back through your posts you were talking about something like 3800 RPM which is quite a lot more air.
I would love to make full boost at 2400.  I dont want to have to run at full throttle so I would ideally like to have the power to turn big impellers up to 3800.  That would allow me to easily cruise around 2400 and have power to spare when I needed to jump on plane quickly or had a lot of weight in the boat.

One thing I dont remember if I stressed was the need to not make smoke.  I will be using this on a river with other people mostly on rafts and paddle boards.  Rolling coal would be like pulling into the middle of a park and blowing smoke in the middle of someones bbq.

Another thing I have thought about is the possibility of an exhaust leak or a boost leak.  I dont think I am making any boost now but it is possilbe that I have a leak somewhere and cant hear it or just dont know what I am listening to.  I know the sound of a gas engine exhaust leak and I assume it would be the same but that is just my assumption.

Thanks for all the help, Matt
[/quote]

Reply #111July 04, 2018, 12:07:11 pm

vanbcguy

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Re: MTDI in a boat
« Reply #111 on: July 04, 2018, 12:07:11 pm »
Ok, gotcha.

Smoke is wasted fuel, nobody wants that. The engine MAY make a little smoke accelerating - ie if you slam the accelerator to the stop you'll probably have some smoke till the turbo catches up once things are tuned right, however it should be minimal and avoidable by easing in to full power. The LDA will let you control that too - I'm assuming you have it connected?

Definitely turn up the max fuel screw. Levelling off at 2100 / 740F means you are quite short on fuel.

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Bryn

1994 Jetta - AHU M-TDI - Jezebel Jetta
2004 Jetta Wagon - 1.8T - Blitzen

Reply #112July 10, 2018, 01:41:30 pm

LabradorSteak

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Re: MTDI in a boat
« Reply #112 on: July 10, 2018, 01:41:30 pm »
I haven't really thought about this but I am running stock nozzles with 195xxxmi on them.  Am I ever going to be able to flow enough fuel with these?  I have a bigger turbo, bigger exhaust, and bigger pump.  It seems like the restriction is the injectors. 

I am thinking about this stuff now because I am unable to test.  I don't have a vehicle to pull the boat to the water.  I went away for the weekend and two hours after leaving my car wouldn't shift out of park.  So my wife drove my truck to rescue me and the kids.  We used the truck to finish the trip...almost.  On the way home the truck died so we rented a car to get back to the first car (which had been repaired by then) and drove home.  This next weekend I will be driving 500 miles round trip to pick up the truck.  For now I don't have a tow vehicle to take the boat to the water. 

That was my $3000 weekend.   ::)

Reply #113July 10, 2018, 02:37:04 pm

vanbcguy

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Re: MTDI in a boat
« Reply #113 on: July 10, 2018, 02:37:04 pm »
Stock nozzles won't make your HP goals, at least not without a ridiculously long injection window. The longer the injection event the more smoke you're going to have too, as well as higher EGTs.

Larger nozzles have poorer atomization which can lead to soot. They also have a harder time at idle since all of the required fuel gets delivered in such a short time - very large nozzles will give you a rougher noisier idle.

That's at the extreme end though - Race 520s or anything else in the 0.260 or larger sizes. I have 0.275s in my car - I get a large puff at startup and a light haze at full power. The bad spot is low RPM transitions though - give it more than 50% accelerator below 2k RPM and the smoke can be a bit much. Easing in to the accelerator slowly eliminates that for the most part.

I'd work with what you have now till you know everything else is working properly - when you are hitting 20+ PSI and your EGTs are maxing out you should look at changing nozzles. Likely something in the middle of the road would meet your needs, particularly keeping smoke in check.

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Bryn

1994 Jetta - AHU M-TDI - Jezebel Jetta
2004 Jetta Wagon - 1.8T - Blitzen

Reply #114July 10, 2018, 09:25:30 pm

LabradorSteak

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Re: MTDI in a boat
« Reply #114 on: July 10, 2018, 09:25:30 pm »
I got to use a friends truck today and ran the boat up the river.  As I expected I couldn't get on plane but it did move up river.  I turned up the fuel screw and got the egt's up to around 840f.  More screw turning just resulted in black smoke and no increase in egt's.  Still no boost registering.  I bought a cast iron exhaust manifold with a mount for a t3 turbo that will be here friday.  I am going to remove all of the water jacketed stuff that goes before the turbo and do some testing to see if it helps.  I have to start eliminating potential problem areas until I get something that works and then start adding things from there.  Right now I have so many joints and potential leak points that finding a single problem seems unlikely.

Also, I realized that a small log exhaust is as small as the adapter that I made to mount the water jacketed exhaust so there shouldn't be any more potential hot spots and it eliminates alot of complexity and weight.

Matt.

Reply #115July 10, 2018, 10:35:33 pm

vanbcguy

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Re: MTDI in a boat
« Reply #115 on: July 10, 2018, 10:35:33 pm »
I do recall seeing another TDI boat running in to a similar problem with water jacketing pre turbo. Don't forget, a turbo runs on heat, so if you're cooling the exhaust down significantly before it gets there you're removing its ability to work. On the other hand insulating coatings and the like would certainly help keep the heat where it needs to be.

Oh, also, the Rover pump has a much smaller cam plate than a VW. If you still have stock nozzles it will need a longer injection window to send as much fuel as a stock VW pump would in the same time. See earlier statements about smoke from long injection durations...

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Bryn

1994 Jetta - AHU M-TDI - Jezebel Jetta
2004 Jetta Wagon - 1.8T - Blitzen

Reply #116July 11, 2018, 12:25:17 am

libbydiesel

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Re: MTDI in a boat
« Reply #116 on: July 11, 2018, 12:25:17 am »
Don't forget, a turbo runs on heat, so if you're cooling the exhaust down significantly before it gets there you're removing its ability to work.

Indeed!  Don't cool anything pre-turbine other than the cylinder head and let that be as hot as is safe.  The turbine is a waste heat scavenger and removing any heat unnecessarily before the turbine will only hurt its efficiency. 
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Reply #117July 20, 2018, 11:58:18 pm

LabradorSteak

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Re: MTDI in a boat
« Reply #117 on: July 20, 2018, 11:58:18 pm »
I found a lot of exhaust leaks.  The only way that I can explain that I didnt notice them is that the engine seemed really loud (not the exhaust).  The leaks didnt sound like the leaks I have heard from gas engines.  Anyway, that is what I am dealing with now.  I bought a cast iron manifold off of ebay and an adapter to directly hook my turbo to the manifold.  Hopefully this will get the turbo blowing some air.  I should be able to finish and test it (at least in the driveway) this weekend.  It is hot here (up to 108*) so I may just sit inside and think about working on the boat.

Matt.

Reply #118October 05, 2018, 06:50:05 pm

LabradorSteak

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Re: MTDI in a boat
« Reply #118 on: October 05, 2018, 06:50:05 pm »
I have been busy with a lot of other things but I have done a little on the boat. I got rid of the water cooled exhaust and the big manifolds and am using a small cast exhaust. I got rid of all of the exhaust leaks and when I I pulled off the hose I was able to feel air blowing out of the turbo for the first time!!  Unfortunately I am still not registering boost and I can't get my egt's much above 800. As I turn the screw I start to make more and more smoke but no more power and my egt's don't get any higher.

I am stuck at a point where I am not making enough power to get the rpm's that I need to create boost to make more power.

I don't understand why I can't get my egt's higher than 850.

Matt

Reply #119October 07, 2018, 12:24:20 pm

libbydiesel

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Re: MTDI in a boat
« Reply #119 on: October 07, 2018, 12:24:20 pm »
Something is amiss if you are getting smoke with low EGTs and the engine is not accelerating.  In other words, a steady state 800F full load should not make smoke at all.  Even before the turbo spools up you shouldn't see any significant smoke until EGTs are over 1200F if all is correct.  It sounds like something isn't letting air in correctly.  Intake restriction, e.g. plugged air filter, collapsing intake hose, rag in the patient, etc...?
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