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Author Topic: MTDI in a boat  (Read 8790 times)

August 16, 2016, 02:29:29 pm

LabradorSteak

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MTDI in a boat
« on: August 16, 2016, 02:29:29 pm »
First, I am so glad I found this site.  Thanks.

I have been reading a lot about mTDI set ups and still have a few questions that may be obvious but the answers have escaped me. 

Background...I have a lot of experience with jet boats and gas engines.  I understand EFI and have rebuilt engines.  I have had an ALH in a 99 bug that I worked on so I know the basic architecture and the basics of eTDI.  Some basic assumptions I have may be totally off base so feel free to get simple with me.

1.  do the injectors work like a gas injector where there is a gate that opens and closes or are they just a nozzle?  If they are just a nozzle why are they so expensive?  and if they are gated like a gas injector why does the injector pump meter and time injections?  and what tells them to open and close?

2.  Why not use a waste gate and BOV to control boost when using a VVT and discarding the computer?  then just leave the turbo at what ever level you want to or even a lever that allows you to adjust it for optimal performance at the current driving conditions.

3.  Am I missing something or are there more parts to the mTDI set up.  Right now all i can see as parts are the:
 
          a.  engine...consisting of block, head, pistons, valves, cam, manifolds, oil pump, etc...mechanical stuff to move the air in and exhaust out.
          b.  Turbo...either VVT or WG BOV controlled
          c.  Injector pump and plumbing to supply fuel
          d.  Mechanical water pump and cooling system.
          e.  Front of engine stuff turned by belts off the crank...waterpump, alternator and injector pump

All of these things are individual systems that don't talk to each other and the only connection is the timing belt and moving air.  No sensors tell one system to do something different because of another systems status.  Basically no sensors or wires of any kind any where other than the alternator, starter motor, and shutoff valve.

Is this correct?  I seriously feel like I am missing something.  The injector pump is a complicated mechanism but other than that...???

Thanks, Matt.




Reply #1August 16, 2016, 03:13:53 pm

libbydiesel

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Re: MTDI in a boat
« Reply #1 on: August 16, 2016, 03:13:53 pm »
1.  do the injectors work like a gas injector where there is a gate that opens and closes or are they just a nozzle?  If they are just a nozzle why are they so expensive?  and if they are gated like a gas injector why does the injector pump meter and time injections?  and what tells them to open and close?

Later PD and CR injectors are different, but the injectors fitted to TDI engines with the electronic VE injection pump are purely mechanical in operation.  The injector nozzle is very precisely machined.  It is basically an outer part that has a 'seat' and an inner needle/pintle.  The pintle lifts when fuel pressure pressing acting on it overcomes the spring tension that keeps it seated.  At that point, fuel sprays out.
 
Quote
2.  Why not use a waste gate and BOV to control boost when using a VVT and discarding the computer?  then just leave the turbo at what ever level you want to or even a lever that allows you to adjust it for optimal performance at the current driving conditions.

A BOV is not a turbo control mechanism.  It releases intake pressure which simply hurts engine efficiency.  BOVs are sometimes employed as an engine safety device, but never as a turbo control and never should be. 

In contrast, a wastegate operates on the exhaust side.  It opens a valve in the exhaust that allows exhaust gases to bypass the turbine.  Variable vane turbos (VVT) adjust vane position to control boost.  None of the exhaust gases ever bypass the turbine.  When the vanes close (direct the exhaust gases more perpendicular to the blades of the turbine), the speed of the turbine increases but they also restrict the exhaust flow and cause higher exhaust manifold pressures.  When the vanes are more closed, you get more boost, but you simultaneously hurt engine efficiency by increasing the restriction of exhaust flow.

There are basically two ways to use a wastegate to control a VVT and both are far from ideal.  One way is to make the vanes stationary at moderate position.  An external wastegate can then be used to bypass the turbine.  In that version, the VVT has been functionally turned into a wastegated turbo with the slight advantage of being able to adjust the fixed vane position to make the turbo 'larger' or 'smaller'.  The second way would be to affix the 'wastegate' actuator directly to the vane lever.  The vane position would be adjusted based on boost pressure and max boost would be regulated.  The downside to that control is that it will always default to closed vane position.  This hurts engine efficiency by causing excessive exhaust restriction at all times other than max boost. 

Quote
3.  Am I missing something or are there more parts to the mTDI set up.  Right now all i can see as parts are the:
 
          a.  engine...consisting of block, head, pistons, valves, cam, manifolds, oil pump, etc...mechanical stuff to move the air in and exhaust out.
          b.  Turbo...either VVT or WG BOV controlled
          c.  Injector pump and plumbing to supply fuel
          d.  Mechanical water pump and cooling system.
          e.  Front of engine stuff turned by belts off the crank...waterpump, alternator and injector pump

All of these things are individual systems that don't talk to each other and the only connection is the timing belt and moving air.  No sensors tell one system to do something different because of another systems status.  Basically no sensors or wires of any kind any where other than the alternator, starter motor, and shutoff valve.

Is this correct?  I seriously feel like I am missing something.  The injector pump is a complicated mechanism but other than that...???

That is correct.  The injection pump accomplishes all of the tasks of fuel injection and ignition timing. 
Use, abuse or ignorance of any information is at your own risk, confirmation or refutation is your own responsibility, no further 'proof' will be given, take it or leave it, YMMV,terms subject to change without notice, avoid contact with eyes or skin, contents known to cause cancer in California

Reply #2August 16, 2016, 04:35:21 pm

LabradorSteak

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Re: MTDI in a boat
« Reply #2 on: August 16, 2016, 04:35:21 pm »
Thanks for the reply.

I plan on using an ALH and a 300tdi rover IP to make 200-250hp reliably.   Drivability is not an issue since driving a jet boat is like driving on a flat road in one gear.  It takes a set amount of hp to turn the jet pump at a certain speed regardless of the boats speed.  I am sure that there will be a reasonable learning curve but thats half the fun.

I know I have a lot more reading to do and will ask many more simple questions in the future.

Are there recipes for building these motors?  My experience is mostly with small block gen1 Chevys where if you put in cam A with Carb B and exhaust C you should make about X HP. 

Thanks, Matt

Reply #3August 16, 2016, 05:14:31 pm

libbydiesel

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Re: MTDI in a boat
« Reply #3 on: August 16, 2016, 05:14:31 pm »
If you are going to operate the engine at a steady rpm/power then there is no advantage to a VVT.  I would recommend using an appropriately sized wastegated turbo.  TDI club will have more info pertinent to higher power output builds.  Just a heads up... there's a fairly significant bias on that site against mTDI's. 
Use, abuse or ignorance of any information is at your own risk, confirmation or refutation is your own responsibility, no further 'proof' will be given, take it or leave it, YMMV,terms subject to change without notice, avoid contact with eyes or skin, contents known to cause cancer in California

Reply #4August 17, 2016, 11:09:22 pm

vanbcguy

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Re: MTDI in a boat
« Reply #4 on: August 17, 2016, 11:09:22 pm »
Alcaid on here can set you up with a good turbo. There's a good thread on TDIclub from about a year ago with a TDI boat power plant - I think it was a Mercury but I can't recall.

Sent from my XT1097 using Tapatalk

Bryn

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

Reply #5August 18, 2016, 12:51:07 am

LabradorSteak

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Re: MTDI in a boat
« Reply #5 on: August 18, 2016, 12:51:07 am »
I have been reading on TDIclub and it seems that 170-200hp on an ALH is not very hard or expensive to do.  There is no consensus of how much a stock ALH will tolerate before detonating.  That is understandable due to the many conditions which engines run.  I think being able to consistently run at 100-150hp between 2000-3000rpm is what I will need.  A good way to look at what a boat motor does is like a truck towing uphill.  Every hp made is used...there is no coasting...if less hp is made then the boat/tow vehicle slows down.  The boat has a constant supply of cool/cold water to lower temperatures but running any engine at peak torque under full load is not a recipe for longevity.  So I am thinking that the further under the curve I can operate the less stress the motor should be under.

I don't have an engine yet.  I want to make sure that I am headed in the right direction first.  I had a friend who tried to TDI a samurai and ended up buying two engines before he got it right.  I don't want to head down the wrong road.  There will be enough of a learning curve to fight through and I don't want to make it harder by starting off wrongly. 

The engine I have been looking at is a lightly refreshed ALH (new bottom end bearings, new water pump, new 17/22 turbo)  There are good deals on low mileage PD engines but I understand these are not necessarily mTDI-able.  I have found lots of AAZs for a reasonable price.  So I am still searching.  If anyone has any contacts or leads I am interested. 

Thanks again for all of the help...Matt.

Reply #6August 18, 2016, 01:25:49 am

libbydiesel

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Re: MTDI in a boat
« Reply #6 on: August 18, 2016, 01:25:49 am »
If you are consistently pushing 150hp or more, I would use an ALH with upgraded rods, a wastegated turbo that is efficient at that power, water-to-air intercooler.  I would focus on max power at 3500 rather than 3000.  The advantage to the VNT turbos is off-the-line performance with good higher rpm efficiency.  It sounds like you don't need 'off-the-line' performance, so the added complication of a VNT would be a downside.  I'm a big fan of VNT turbos, but this doesn't sound like the right application for one. 

PD is not an option for mTDI.  You could use a 2.0L PD bottom end with the ALH head and run it as a 2.0L ALH.   
Use, abuse or ignorance of any information is at your own risk, confirmation or refutation is your own responsibility, no further 'proof' will be given, take it or leave it, YMMV,terms subject to change without notice, avoid contact with eyes or skin, contents known to cause cancer in California

Reply #7August 18, 2016, 11:01:56 am

LabradorSteak

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Re: MTDI in a boat
« Reply #7 on: August 18, 2016, 11:01:56 am »
I read about changing the head a little. Would the head just bolt on or would I have to machine the Pistons?  I'm not that excited about starting from a bare block but just changing a head would be simple.

Matt

Reply #8August 18, 2016, 12:56:40 pm

libbydiesel

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Re: MTDI in a boat
« Reply #8 on: August 18, 2016, 12:56:40 pm »
I haven't done an ALH head on the 2.0L bottom end myself.  I read a thread on TDI club where someone else did, but that was a while back and I don't recall the details.
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Reply #9August 18, 2016, 03:56:58 pm

LabradorSteak

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Re: MTDI in a boat
« Reply #9 on: August 18, 2016, 03:56:58 pm »
I copied this from tdiclub so a brm block would work but my first choice would still be a decent Alh.

"the BEW pistons are a nogo unless you machine them for valve reliefs... the brm "could" work but the cps is pulled from the rear seal assembly and not from a crank mounted reluctor wheel as in previous PD's ... and it's signal may not be compatible at all with the edc15 hardware ... talk to your tuner on that one... now if you're going all mechanical then the BRM block would work fine, just slap an ALH head on it with the correct gasket and go"

Matt

Reply #10August 18, 2016, 08:44:25 pm

LabradorSteak

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Re: MTDI in a boat
« Reply #10 on: August 18, 2016, 08:44:25 pm »
After many more hours of reading I think just going with a straight Alh or Ahu is the best way to go. They have fewer places for me to make mistakes...I want to keep this as simple and enjoyable as possible.

Matt

Reply #11August 19, 2016, 12:08:47 am

libbydiesel

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Re: MTDI in a boat
« Reply #11 on: August 19, 2016, 12:08:47 am »
The ALH is a stronger/better block design and has stronger stock rods.  The AHU is a good choice for earlier year inline-4 VW's because it shares the block mounting points and mounts right up, but considering the custom installation in a boat, I'd choose an ALH. 
Use, abuse or ignorance of any information is at your own risk, confirmation or refutation is your own responsibility, no further 'proof' will be given, take it or leave it, YMMV,terms subject to change without notice, avoid contact with eyes or skin, contents known to cause cancer in California

Reply #12August 19, 2016, 11:54:31 pm

LabradorSteak

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Re: MTDI in a boat
« Reply #12 on: August 19, 2016, 11:54:31 pm »
How important is mileage?  One engine I'm looking at has 73k and one has 280k. Both run and have what I need for parts. The 73k is more money by about $1000.  But I keep hearing how long these things run and 280 isn't too bad.

How much is involved in rebuilding the short block. If it's just crank shaft bearings and rings I can do that easily. But I would rather not...

Thanks, Matt.

Reply #13August 24, 2016, 01:13:55 am

LabradorSteak

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Re: MTDI in a boat
« Reply #13 on: August 24, 2016, 01:13:55 am »
Hope this isn't too simple of a question but Are nozzles and injectors the same thing?

Thanks, Matt

Reply #14August 24, 2016, 01:46:36 pm

libbydiesel

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Re: MTDI in a boat
« Reply #14 on: August 24, 2016, 01:46:36 pm »
The nozzle is the tip of the injector and normally the only wear item that is part of the injector.  There are other component parts to the injector e.g body, springs, etc...  Some people use the terms nozzle/injector interchangeably, but it is not correct and leads to confusion. 
Use, abuse or ignorance of any information is at your own risk, confirmation or refutation is your own responsibility, no further 'proof' will be given, take it or leave it, YMMV,terms subject to change without notice, avoid contact with eyes or skin, contents known to cause cancer in California

 

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