adding a charge-air cooler

[bevans6]

As I get closer to finalizing the plumbing for my 8v-71T install in my MC-5C, I realize that I could very easily add a charge-air cooler to the turbo.  It would  involve adding the intercooler, and the tubing from the turbo and back to the intake on top of the engine.  I would use 3.5" diameter tubing, since that is the size of the turbo outlet and the manifold inlet.  What else is involved?  Is it as simple as just adding the cooler?  is there a better way to pick a unit than just finding one that fits the space and has the in/out in the right locations?  It adds horsepower, from what I understand, but is there a way to estimate the effect?  does it make the engine run noticeably hotter or cooler?

[JohnEd]

Rule #1...If you cool the air going into the engine that alone will have the effect of cooling the engine so, to some small degree, you reduce the load on the rad.  That is a MUST HAVE, way way good idea and worth ?  But only if you are cooling the air because of some other reason.  Water injection only serves to "cool" the combustion temp to allow running a more advanced timing without "ping" and that system works well.  I have used it on two engines and I am a strong proponent for power and $ reasons.

Rule #2... Intercoolers don't increase the potential engine horsepower a single one or even a fraction.  If you make 300HP with a Intercooler you will only make 300 with one.  NO GAIN.  Not one.  Nada. Zip.  The intercooler will only prevent you from loosing HP due to induction air temp.  That adds up to 300 HP at the bottom of the hill and 300HP at the top of the hill.  Without the IC you will start off with 300 at the bottom but as you pull harder your turbo will work harder and get hotter, as it should, and your intake air temp will start to climb.  By the time you reach the top of the hill you may find that your "adjusted" HP has fallen to 200.  Just a swag but you get the point.

Rule#3...By adding "volume"the intake air passage you will delay the intake air coming up to the air pressure that you should have with the turbo spooling at a given speed.  Call this "turbo lag".  Very annoying in a car but in keeping with the neck snapping throttle response you have come to know and love in a D pushing a bus.  In short, things haven't changed much, but you can certainly tell the difference at the top of the hill.  All those added pipes and the volume of the IC will combine to delay throttle response.  The lower the temp of the charge air the better so a bigger IC is better in every regard but in a car it becomes maddening waiting for the power to "happen".  Bigger is better.  It's like .....well it's like lots a stuff.  So fit in the biggest unit you can in that space and that you can afford.  Call a IC manufacturer and learn the "ideal" size from a cost trade-off point.  Then start looking hard for a used item that will give you some return on your labor investment.  Maybe Clifford has the exact item you need in his back yard.......he has most everything else.

The benifit of an IC is huge and I think, personally, that you should make a serious effort, time and money, to include it in your design. 

[luvrbus]

Brian, they really need a deflector under the blower for a air to air tough to find but you can build one with you skills and it will run cooler with more power and better fuel economy,not disputing John Ed but on a 8v92 air to air increases the hp around 8 % so says the DD bible cool air makes hp

good luck

[babell2]

Brian
  An intercooler will decrease air charge temp. In a gas engine that means denser air and more oxygen to burn so you can add more fuel and get more output. With an old diesel (non DDEC) it will as JohnEd stated help it keep cooler and improve combustion due to more O2 but do not see much of an HP gain. Either reason in its own is a good reason to go with the air charge cooler both for your engine and the environment.

Brice

[bevans6]

What is the deflector under the blower, and what does it do?

Brian

[luvrbus]

Brian, keep in mind the air to air on a 2 stroke requires a 2.59 or better A/R on the turbo for full benefit check section 14 of the DD bible it will show the changes in hp and torque with air to air with lower rpms and different injectors.
On TA engines the cooler is the deflector they distribute the air more even almost a must for bypass blowers with a turbo.
I always use one when I remove the after coolers some don't your call 

good luck

[Iceni John]

Rule#3...By adding "volume"the intake air passage you will delay the intake air coming up to the air pressure that you should have with the turbo spooling at a given speed.  Call this "turbo lag".  Very annoying in a car but in keeping with the neck snapping throttle response you have come to know and love in a D pushing a bus.  In short, things haven't changed much, but you can certainly tell the difference at the top of the hill.  All those added pipes and the volume of the IC will combine to delay throttle response.

Maybe I'm not reading this right, but how can a diesel's turbo lag be blamed on the length of its intake manifold and pipework?   Diesels don't have throttles, so they are essentially working at WOT all the time  -  it's the quantity of fuel injected that determines their power output.   In this sense, I suppose a diesel is rarely ever stoichiometric (sp?), unlike a gasoline engine.   Is there any appreciable intake manifold vacuum with a diesel, and if so is there any difference between a non-turbo and a turbo diesel?   Also, just to complicate matters, when we have a scavenge blower after the turbo in our 2-strokes, wouldn't that influence any turbo lag issues caused by intercoolers or aftercoolers?

Ow, my brain hurts.

Thanks, John

[bevans6]

I think what happens is we ask for more fuel, more fuel is injected at that time, there isn't enough air to combust  all the fuel, we get a little smoke, the added fuel that is burnt spools up the turbo, air catches up with fuel, no more smoke, lots of power.  The lag is more in getting the turbo spooled up than the length of the intake.  How important is instant throttle response anyway?  My engine has one of the rack delay dohickeys on it to reduce smoke.  But what do I know (not much!)

Brian

[JohnEd]

Rule#3...By adding "volume"the intake air passage you will delay the intake air coming up to the air pressure that you should have with the turbo spooling at a given speed.  Call this "turbo lag".  Very annoying in a car but in keeping with the neck snapping throttle response you have come to know and love in a D pushing a bus.  In short, things haven't changed much, but you can certainly tell the difference at the top of the hill.  All those added pipes and the volume of the IC will combine to delay throttle response.

Maybe I'm not reading this right, but how can a diesel's turbo lag be blamed on the length of its intake manifold and pipework?   Diesels don't have throttles, so they are essentially working at WOT all the time  -  it's the quantity of fuel injected that determines their power output.   In this sense, I suppose a diesel is rarely ever stoichiometric (sp?), unlike a gasoline engine.   Is there any appreciable intake manifold vacuum with a diesel, and if so is there any difference between a non-turbo and a turbo diesel?   Also, just to complicate matters, when we have a scavenge blower after the turbo in our 2-strokes, wouldn't that influence any turbo lag issues caused by intercoolers or aftercoolers?

Ow, my brain hurts.

Thanks, John

John,


You have it all pretty much correct as Brian pointed out.  Regardless of whether you have the air being metered, the manifold pressure DOES fluctuate and there is a lag between the fuel delivery and the fuel/air delivery.  The turbo "spools" up with the throttle demand.  That spooling is one source of "lag".  The other is that as the spooling takes place there is a lag in manifold pressure associated with the volume of the "tank" that is being brought to pressure.  The "tank" in this example is the total volume of all the plumbing and the intercooler itself.  My point here is that if you use a HUGE intercooler you will certainly get better cooling of the charge air but you will also be adding to the "lag" but in a D that isn't any concern.  The cost goes up breathtakingly as you reach for those big intercoolers.  No matter, you will get more performance regardless of the size so my rule is to go as large as you can fit/afford.

According to the DD rep I spoke with years ago..."the cooler the better.  400 degrees is the max charge air temp that a D will ruin on.  Power drops quickly with any increase in charge air temp".  Soooo get all the "chill" you can afford and lag be darned.

I have heard it said before that the "aftercooler", the water to air  heat-exchanger that sits under the blower, can be eliminated without consequence.  That isn't true.  No more so than an intercooler contributes nothing.  If you have one then keep it.  If you have a "A" (for aftercooler) block then install one if you can find one and it is affordable.  Here's the logic:  The intercooler dumps the heat caused by the turbocharger compressing the charge air.  That "cooled" air then feeds the blower/compressor that sits on top of the engine (V).  That blower then further compresses the charge air and in so doing the compressor adds heat to the charge air.  The "AFTER-COOLER" is intended to dump that heat into the coolant with the result being that the charge air temp increase attributable to the blower is reduced.  Result is greater HP and efficiency.

As to the 8%.....that was negligible in that that power wasn't the justification for installing the IC.  Rather, the IC prevents a much larger % of loss in HP due to charge air heat build-up and HP loss due to altitude.  That figure does serve to prove the value of the IC if it also adds a smidge ta boot...LOL

I am pretty sure that the A functions as the Deflector also.  It seems to me logical that in that small space above the intake manifold there would be a lot of turbulence at the outlet from the compressor.  I don't know if you need to install a deflector if you remove the A or if you no longer need the deflector if you up-grade to a A.  Either way.

I understand that "Don The Fairchild" has a 8V92 TA with IC that gets 9 mpg at 70 MPH in an aerodynamic( humor)Eagle or Prevost.  I never heard Don say any such a thing and I have wondered how he did that....if the report was true.  Eliminated the A?  Big IC?  Port and relieve?  Headers?  Injectors made from unobtainium?  No muffler? Water injection?  WHAT?  There has to be an explanation.  Wish I knew....folks....wish I knew.

John

[Ralph7]

    Ok, is your 8V-71 T or TA??  Mine is a TA, another person that did an upgrade to a turboed engine, he started with a 8-71T and made it a 8-71TA.  When I started looking I wanted a TA..
    How much does the cooler under the blower do compared non cooler there?

[luvrbus]

Ralph, air from the turbo through the blower is over 300 degrees after the cooler in the block drops to 200 degrees to the air box lot of difference in the after cooler temps and the air to air charger temps about 1/2 for the air to air,the latter brings a 2 stroke to life just like it does on a Cat or Cummins that was equipped with a after cooler

good luck

[Iceni John]

JohnEd,
Thanks for that explanation.   Now I know!   This forum is amazing - there's not much that someone here doesn't know about.

John

[rv_safetyman]

Brian, as I recall, you are not going for big manifold pressure, but never-the-less, I would roll beads on all the tubing.  The hoses are silicone and do not hold well.  I used exhaust tubing and formed bends on mine (4 inch) and it went well.

The big item you will have to deal with is moving air across the cooler.  That turbo puts a lot of heat into the air and you need to move a lot of air across the exchanger. If you put it in front of the radiator and use the bus fan, you will move air, but you will also add heat to the cooling system (less delta T).

I mounted mine on the opposite side of the radiator and tried electric fans.  Never did work well.  Finally made a deflector box so that I was not fighting the radiator fan and now have a hydraulic fan.  That works OK, but I have to use misters to keep the intake temperature below 160* on the big hills.

Most "experts" say that the air temperature entering the engine should not be more than 50* above ambient in a system with a charge air cooler.  I take a bit of liberty with that and say that I could hit 110* ambient, so I keep my max air temp at 160*

Jim

[bevans6]

I think my project will be an iterative process, gradual upgrades.  I'm sure that my first install will be simple - the turbo I have, which isn't the ideal one, and a straight shot into the manifold on top of the blower.  Steps in future would be the right turbo and the intercooler, since I do believe that the gains are there to be had.  My engine does not have an aftercooler or a bypass blower, so there is only so much I can get to.

But I have to say thanks for the support from the forum and the members on this.  Clifford's sometimes cryptic comments take a little thinking about, but what help!  Don Fairchild in particular has helped me understand the point of what I am trying to do. 

Last weekend I finished fabricating the manifold for the top of the blower - I modified a cast DD manifold so that it suited the turbo being hung just off and below the drivers side valve cover instead of directly behind the engine where my air compressor lives.  Welding that dirty cast aluminium was not my finest hour, but it's done.  I have the exhaust manifold about half done, tomorrow's job is mitering in the cross pipe from the passenger side into the pipe on the drivers side towards the turbo flange.  I am adding in several vee band clamps so that the whole thing can actually come off the engine once it's all done and finish-welded...  My pressure side is going to be all beaded tubing, you bet!  I'll post pictures in a week or so, my camera got left in Nova Scotia last time I visited down there.

Hot here, around 115 today heat index...  I last about 6 minutes in the shop before my eyes are filled and stinging!

Brian

[Ralph7]

 When you install that air to air cooler like stated roll those connectors for those silacone tube connectors and get the spring loaded screw hose clamps and wire that goes around the tubes. If you get a hole 1/4in in the system air loss you loose hugh HP.
 Thanks Luvrbus, I did not the actual ##'s.