Charge air cooler impact?

[bevans6]

Now that I have the confidence back in my bus, I am wondering about a couple of upgrades that I always had in mind.  I designed the turbo mount so that it would be easy to add a charge air cooler.  I wonder what the actual impact to the engine performance would be from doing that.  Any ideas?  I am figuring that it will add some power, but I also wonder if the engine itself might run cooler?  Which brings me to my second idea.  My cooling system is the stock MC-5C installation, and it seems to be working right up to spec.  Radiators look almost new from outside.  But I figure it was initially designed for a 240 hp 6V-71, and then it got the 270 hp bus spec 8V-71, and now I have the 350 hp 8V-71T.  It worked well on my trip, but it was definitely in balance with the engine - day got hotter, temp went up.  Draft behind a transport truck, temp went down.  Up a long hill, temp went up.  Roll down the other side, temp went down.  Temps ranged from 175 (which is where it ran with the 8V-71 natural set at 318 hp specs) up to 190, and never went over 190.  I plan to look at adding a truck spec radiator set on an angle over the frame where the stock AC compressor used to be, ducted to exhaust out the floor, and plumbed into the coolant line coming down from the passenger side radiator and into the coolant return from the front heater core and into the bottom of the water pump.  This will put it in series with the passenger side rad.  Any opinions on this idea? 

Brian

[Jon]

If you get some intake air temperature measurements you will opt to go for a CAC.

Mine downstream from the turbo can approach 500 degrees. If that is not cooled it has a great impact on the engine.

[wg4t50]

The Cummins with the CAC was my first experience with the correct setup, all the DDC units had the after cooler below the turbo/blower, except for my last expermenting with a CAC, but never able to get a meqningful temp reading.

With the Cummins ISM500 and using the VMSpc computer readout, I have been amazed with the indicated temps.  The intake manifold temp with the CAC normally reads about 10f above the outside temp, so a 75f day, the intake is about 85f, such a maor change from the old water cooled style after coolers.

Of course the ISM500 is only running about 33-34 psi boost, unlike the big numbers from the 8V-92 big horsepower, non standard by far, enough air box psi to break off the alunimum air box covers.
Just saying, Love what I am seeing with the CAC setup.
Dave M

[lostagain]

Rad cooling: with a system in good condition, it is not a problem. Until you run in hot weather, like in the 30s C, 100s F. Then I find having to manage the temp with keeping revs up, not lugging, etc. On my 5C, I have the MC9 bigger rads, the bigger squirrel cages, and the smaller pulley at the gear box. I can't remember the sizes, but can measure if needed.

JC


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[luvrbus]

If you have a TA block a after cooler helps a lot in dropping the temp the old 2 strokes don't produce as much heat down stream temp as a series 60,they are around 300 degrees the after cooler drops that to 200+ or - but not as much as a CAC. You will differently need a different turbo and a bypass blower for a CAC on a 2 stroke 

[chessie4905]

   Add a set of radiator misters for added insurance on those extreme climbs or outside temps. Also make sure you run Nalcool or equivalent in the cooling system.

[RJ]

Brian -

Sent you a PM. . .

[TomC]

I turbo'd and installed an air to air intercooler on my 8V-71. I kept the high compression pistons, so we used a 12.7 liter Series 60 turbocharger with waste gate set at 15psi. I also have the by pass blower valve, fuel modulator, and use 7G75 injectors. On a non aftercooled 8V-71, the N75 injectors will get 350hp and 950lb/ft torque. With the air to air intercooler, the power increases to 375hp and 1125lb/ft torque (I had it dynoe'd). So you can see the efficiency difference between using an air to air intercooler and none. I'm not sure what a TA aftercooler would do-but probably closer to the air to air intercooler. Good Luck, TomC

[bevans6]

Thanks for the note, RJ, I appreciate it.  Thanks to all for the thoughts.

I think I will take a two pronged approach, CAC then adding an additional radiator if required.  My reasoning is that while the additional power would logically add heat that must be rejected by the cooling system lowering the intake air temperature so drastically must also reduce exhaust temperatures, combustion chamber temperature and lower the over-all temperature of the engine, reducing the cooling load.  It would reduce the load all the time, while the added power would only be raising the temp when in play, and the majority of the time the engine would be producing the same power it does now, balancing power against cruising speed at part throttle.  So now I will start to think about how to spec out and size a CAC.  Technically it would be called an intercooler because it cools the charge in between the turbo and the blower/supercharger, apparently that is an intercooler.  I am shying away from a DD aftercooler, even though my block appears to be suitable, because I think that it can at most cool the intake charge to something higher than the coolant temp, and the CAC literature seems to suggest it will cool to around 130 - 150 degrees before the blower.  I am also going to stick with my current old style turbo and non-bypass blower for now as well.  It's my understanding that the bypass blower is more of an efficiency modification than a performance mod, letting the blower kind of free-wheel by equalizing pressures before and after.  The turbo is pretty slow to spool up, but that's OK - it seems to work fine after the engine gets up to speed.

Now to do some more research...  Maybe I will get lucky and find that a used CAC out of some pickup truck will be ideal...

Brian

[chessie4905]

   One out of a pickup won't be large/ flow enough. Check out a heavy duty truck salvage yard.

[luvrbus]

Brian,you are going need 1100 to 1500 sq inches of CAC surface for a 2 stroke according to DD,the bypass blower has more advantages that just efficiency with CAC I prefer the mini bypass blower It's in the DD book the after cooler drop the temps from 300 to 200 degrees  

You are not going to get the numbers you are thinking about, before the blower sure but the blower is going to heat the air back to 200+ degrees CAC are not new to the 2 strokes they been around since the 80's they were never used on buses because of space the last 8v92 was 550hp with a inter cooler All the engines manufactures Cat,Cummins etc used the after cooler I never was a huge fan but it worked for years

Fwiw finding the air defusing unit for under the blower is a impossible feat but if you go that way I have one I will ship you for the shipping,I have a CAC but no way can you install it on a MCI it's huge so is the 2.94 A/R turbo that is uses

[TomC]

Any size air to air intercooler will be helpful. What you need to do is have one made that has the correctly sized hose fittings and thick enough to flow the proper amount of air. I believe 1400CFM will be sufficient. (I'm sure Clifford will correct me if I'm wrong.) Then you have to find room to mount it. I lucked out in that my Vdrive was designed for a 96" wide bus. With mine being 102", there was enough room and mountings in front of the radiator since one of the options on the bus was for radiator mounted air conditioning condenser. Good Luck, TomC

[HB of CJ]

We were taught a good inter cooler system is required for an inter grated (speeell chck not working worth a damn today....intergrated not even in the spelling menu!!!) turbo system to even work properly.  Piston and valve life and mileage comes to mind.

Boats worked the best with very cold sea water.  Air to water cooling.  In a Bus Conversion, about the only thing you can do is run a large, well designed air to air inter cooler with all the required high pressure fittings and gentle large diameter sweeps done right.

Make sure your blower has the turbo by pass thingie.  We will assume the mill is set up inside with the proper pistons, cams, timing, etc..  The extra power the Detroit will produce with a good inter cooler will be considerable.  You will feel it.

The good news is that the extra heat expected punishing a marginal cooling radiator system may not occur.    Inter cooling markedly reduces the inlet charged air TEMP through into the air box.  Any power increase MAY come without impacting the radiator.

If you must, be sure to mount the actual air to air radiator outboard of any other radiators, like water, A/C, oil, gen sets, etc..  The inter cooler radiator must be big enough and have first priority in getting the required high air flow through the thing.

Hope this helps kinda.  HB of CJ (old coot) now starting a DD353TI Half Ton GMC pickup short wheel base step side truck project.  Wish me luck.  I am going to $need$ it.

[robertglines1]

RV Safety Man: I think it was that used a CAC not as part of his RAD. Maybe Jim will see this and comment.  My Cac is 5  inch in and out.  Blue boots on connections. Different colors = tolerance to temperature.  Does it smoke the back tires yet?  Bob

[bevans6]

I am looking at basically replacing the driver's side door of the engine bay with the intercooler, so dimensions are dictated to some extent by that space.  I think that cooling the intake charge will help a lot with over all cooling requirements so I may not need to also add a radiator.  I've found a lot of web sites that have a lot if info, I am hoping for a stock replacement unit but I could just buy a core and make the ends to suit my needs.  I haven't found anything that helps me figure a size, airflow or other way of figuring the actual specification of the unit yet.  Bigger seems better up to the point where bigger isn't better, which doesn't actually help a lot...

Good project, I am really looking forward to working this out and putting a solution in place.

Brian