more power 1.6td (UPPING THE BOOST) - page 1 - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• more power 1.6td (UPPING THE BOOST) by n_tensetuning on 27 May, 2004 10:04
• hey guys,
  I finally had a shop dial in my pump timing on my 81 caddy 1.6td. They set it at 1.03mm... and i'm seeing around 10psi. Doesn't seem to have much torque. But that can be the fact that i'm running 2.5"downpipe+complete exhaust.
  
  I also noticed that the motor now is not overheating! The shop told me that the pump timing was at .92 before, and that it was probably running too hot because it was running too lean!
  
  the question i have now is, Can i turn up the boost by just removing the valve on the intake manifold? I see it has a flat screw in the middle of it for adjustment?  while i'm right there, i also wanted to remove the hose that comes from the valve cover to the intake, and run a catch can/breather.  I can eliminate 2 birds with one stone.
  
  anyone else do this?  i know that a good way to up the boost is to just play with the wastegate lever to allow more boost to form, right?
  
  anyone think that the motor can safely handle 12-15psi with the stock pump settings at 1.03mm
  
  
  thanks
  david
• #1 by VWRacer on 27 May, 2004 10:20
• Good to see you making progress, David!
  
  The shop guy who told you the engine is running hot because it is "lean" is an idiot! The leaner a diesel is (i.e., the less fuel injected per cycle), the COOLER it runs. The guy was thinking of how a gas engine works, where leaner is hotter, to a point.
  
  Yes, the big downpipe and exhaust will let your engine run cooler because it is generating less back pressure on the turbine section.
  
  Your engine will have no problem accepting a bit more boost. On my '85 Quantum TD I removed and plugged the line from the compressor section to the wastegate, so now I have no wastegate at all. That raised the boost from 9 psi max to 12.5 psi max, and gave me a noticable increase in acceleration.
  
  Have fun!
  
  Stan
• #2 by DieselsRcool on 27 May, 2004 12:02
• Less torque? More heat? I doubt it's even close to 1.03mm. Can't trust what the mech is telling you because of his "lean" explanation.
  
  Get someone else to check it or learn how to do it yourself.
• #3 by fspGTD on 27 May, 2004 13:03
• I think lean/rich applies to diesels.  But of course it's not uniform throughout the combustion chamber like it is with gasoline motors.  On a diesel some areas in the combustion chamber (right near the injector spray) are getting much more fuel than others (dead space in the main chamber).  The areas with more fuel are rich (sometimes too rich, if it's smoke) and the areas with less fuel are likely lean.  Increasing the fueling beyond the smoke level will make some of the areas overly-rich, but will also make some of the areas that used to be too lean richer.  That's why turning up the fuel even when there is smoke will continue to give more power.  Because mixing isn't as good in a diesel (where the fuel gets milliseconds right before TDC to mix) as in a gas engine (where fuel is mixed close to perfectly before it enters the combustion chamber), the diesel will make less power for a given air quantity than a gas motor.
• #4 by DieselsRcool on 27 May, 2004 14:06
• I'm guessing that TDIMeister is qualified to weigh in here. I wish he would. I'm not infering that fspGTD is unqualified, on the contrary. I can see both sides and would like to know TDImeister's views if he is willing to give them.
  
  TDImeister wrote: (Peter Hofbauer is Senior Technical Advisor at FEV Engine Technology in Auburn Hills, MI, where I worked between October 2000 until January, 2003. I didn't have a chance to work directly with him on any projects, but I was well aware of a number of his activities. Most of my time was spent on a project designing a new family of locomotive Diesel engines (4500 HP V12 and 6750 HP V16  ), although I did spend some time at Ford in Dearborn and also working on some EPA/DOE engine design projects.)
• #5 by n_tensetuning on 27 May, 2004 16:58
• hey vw racer,
  
  i was just looking at my turbo, there is a small metal line that goes from the turbo's intake/compressor side to the wastegate on the back....  is this what you plug up to increase the boost to 12psi or so???  this line looks like a small metal brake line.
  
  what about the pressure relief valve on the intake manifold?? can i get rid of that as well?   i'm still at the stock pump settings....   maybe i should just eliminate the other line on the turbo compressor to wastegate to be safe?
  
  also, judging from the pics on Etka, the intake elbow on top of the intake manifold looks like it can be rotated 90degrees??   i'm just trying to get a feel for making some intercooler pipes to run an audi 1.8t intercooler i have lying around.
  
  lastly, anyone running a catch can/oil breather, and elminated both the pressure relief valve on the intake manifold, and the hose from the valve cover, and just ran it to a catch can?
  
  
  david
• #6 by VWRacer on 27 May, 2004 17:51
• Yes, David, I simply disconnected that hard line and screwed an appropriate metric bolt into the compressor scroll. Instant 3 psi boost!
  
  I also disconnected the oil vapor line from the compressor intake. I didn't like running all those oily fumes into the turbo. I only put a few miles on this setup per week, driving the Quantum only for tests, but if it was my daily driver, I'd make a catch can.
• #7 by Dr. Diesel on 27 May, 2004 18:26
• Quote from: "VWRacer"

  On my '85 Quantum TD I removed and plugged the line from the compressor section to the wastegate, so now I have no wastegate at all. That raised the boost from 9 psi max to 12.5 psi max, and gave me a noticable increase in acceleration.
  

  
  
  Stan, I bet if you plugged the outlet hose on your safety valve, you'd find the boost would be over 25. If your wastegate is disabled, likely the poor little turbo is just screaming, but the safety valve limits boost as it should to around 12 psi. At that level, the turbo will be making way too much heat too. I bet you'd go faster if you did plug the safety valve outlet, and make a simple, gated boost controller to make the wastegate limit pressure to 12 (or whatever you want) thereby reducing the heat being generated by the compressor.
  If you want, I can show you how to make a simple, reliable gated boost controller.
• #8 by TDIMeister on 27 May, 2004 19:04
• To DieselsRcool: Aww, shucks  :oops:
  
  

  Quote from: "fspGTD"

  I think lean/rich applies to diesels.  But of course it's not uniform throughout the combustion chamber like it is with gasoline motors.  On a diesel some areas in the combustion chamber (right near the injector spray) are getting much more fuel than others (dead space in the main chamber).  The areas with more fuel are rich (sometimes too rich, if it's smoke) and the areas with less fuel are likely lean.  Increasing the fueling beyond the smoke level will make some of the areas overly-rich, but will also make some of the areas that used to be too lean richer.  That's why turning up the fuel even when there is smoke will continue to give more power.  Because mixing isn't as good in a diesel (where the fuel gets milliseconds right before TDC to mix) as in a gas engine (where fuel is mixed close to perfectly before it enters the combustion chamber), the diesel will make less power for a given air quantity than a gas motor.

  
  
  I make no claims to be an expert specifically to the IDI, so here goes...  :shock:   What I do know is that the x.xx mm setting is a timing setting, not a mixture one (i.e. higher number, more advanced -- correct?)
  
  On that basis, yeah the mechanic who did the work on the original poster's engine was either honestly mistaken or just didn't know what he was talking about...
  
  Jake hit the nail right on the head with regards to the varying heterogeneity of the fuel-air ratios within the combustion chamber of a Diesel.  I'd only add that the only reason why the temperature/mixture logic in a gasser doesn't seem to work in the Diesel world is because the operational range of overall fuel-air mixtures in Diesels are off the scale to the lean side of what a typical gasser engine would normally be able to operate.  Even at the smoke limit, a good Diesel engine is still operating at fuel-air ratios over 18:1, which is basically the misfire limit of of homogeneous gasser engines.  How "rich" a Diesel can run before reaching the smoke limit is what's called the "air utilization" ratio or rate or efficiency); at 18:1 this would be about 83% if stoichiometric is assumed to be 15:1.  (The term "air utilization" used here is the inverse of another term, "excess air.")  What this means is that no matter what you do, you cannot utilize more than 83% of the available oxygen in the air to burn the given amount of fuel.  Or stated in terms of "excess air" there is 20% more air than is required to completely burn a given amount of fuel.
  
  Combustion temperatures have a bell-shaped pattern in relation to the fuel-air ratio, with its peak just lean of stoichiometric (which not coincidentally is the point of optimum thermal efficiency in any engine, the reason of which can be attributed to thermodynamics).  At either side of the peak, combustion temperatures fall off pretty quickly, and when you get to the fuel-air ratio regime that a Diesel operates in (> 18:1), the bell shaped curve has pretty much flattened such that there's not a heck of a lot of difference when you change the F/A ratio.  Note that the bell-shaped pattern is surprisingly pretty INVARIATE REGARDLESS OF THE FUEL USED (comparing within hydrocarbon fuels; hydrogen and alcohols are slightly different).
  
  So in conclusion, Jake, you're right  
• #9 by DieselsRcool on 27 May, 2004 19:49
• Hmmm, as I suspected!
  
  Jake is correct in the absolute technical sense adding knowledge for all our sake.
  
  And of course TDIMeister with a great answer that needs to be slowly re-read a number of times to be fully comprehended.
  
  
  Man! I love you guys!!!
• #10 by VWRacer on 27 May, 2004 20:39
• Quote from: "Dr. Diesel"

  Stan, I bet if you plugged the outlet hose on your safety valve, you'd find the boost would be over 25. If your wastegate is disabled, likely the poor little turbo is just screaming, but the safety valve limits boost as it should to around 12 psi. At that level, the turbo will be making way too much heat too. I bet you'd go faster if you did plug the safety valve outlet, and make a simple, gated boost controller to make the wastegate limit pressure to 12 (or whatever you want) thereby reducing the heat being generated by the compressor.
  If you want, I can show you how to make a simple, reliable gated boost controller.

  
  I'm drawing a blank here about the safety valve, Doc. I just stepped down to the shop and took a look at the TD and for the life of me can only see one line feeding air to the wastegate (the one I have plugged). Am I missing something?
  
  FWIW, I recently purchased a gated boost controller ($9 off eBay), but have no reason to use it with a max pressure of 12 psi. Thanks for the offer, though!
• #11 by fspGTD on 27 May, 2004 20:47
• Quote from: "TDIMeister"

  Combustion temperatures have a bell-shaped pattern in relation to the fuel-air ratio, with its peak just lean of stoichiometric (which not coincidentally is the point of optimum thermal efficiency in any engine, the reason of which can be attributed to thermodynamics).  At either side of the peak, combustion temperatures fall off pretty quickly, and when you get to the fuel-air ratio regime that a Diesel operates in (> 18:1), the bell shaped curve has pretty much flattened such that there's not a heck of a lot of difference when you change the F/A ratio.  Note that the bell-shaped pattern is surprisingly pretty INVARIATE REGARDLESS OF THE FUEL USED (comparing within hydrocarbon fuels; hydrogen and alcohols are slightly different).

  
  
  Oh my!   :shock:   OK I admit that went a little over my head.  (I feel thankful we've got such knowledgeable folks up here on the board!   )
  
  Now, back to our 1.03mm timing question... :lol:
• #12 by cheng on 27 May, 2004 23:30
• Quote from: "Dr. Diesel"

  If you want, I can show you how to make a simple, reliable gated boost controller.

  
  
  hey Doc, I would like to see that.
  
  right now I'm running with the waste gate disconnected, and I just pull my foot out when I see the pop off valve dump all my boost. (at about 8 psi)
  
  ken
• #13 by DVST8R on 28 May, 2004 00:17
• Vw racer, it isn't connected to the wategate. The saftey valve is the black round thing on the intake manifold, if you plug that tube you will now see the true boost the turbo is trying to make  :wink:
• #14 by VWRacer on 28 May, 2004 09:27
• D'oh! I completely missed the blow-off valve (as my Bentley calls the "safety valve"). :oops:
  
  I reread chapter 21, which calls for the BOV to open at 11.5 +/- .7 PSI, and since I am reading max boost of a bit over 12 PSI, it appears to be working as designed. Now what Dr Diesel wrote makes complete sense.
  
  This is the controller I purchased. They are on ebay for $14, shipping included.