Smoke Turbo

[TomC]

Just got back last week from a 17 day jaunt to Arizona.  The bus ran without a missed beat.  The only complaint was the high altitude performance.  I have the 8V-71N with brown tag N65 injectors going through a V730 in a transit.  I cruised at 58mph most of the time (1900rpm) and got 5.5-6.0 mpg at or near sea level.  Also, it only smokes a bit on the last inch of pedal at sea level (the bus has a left side up exhaust).  When I was around Sedona, Flagstaff, Grand Canyon-all above 5,000ft (Flagstaff at 7,000ft), I tried to keep out of it as much as I could since the black smoke at full throttle was enough to eliminate mosquitos (also mileage dropped to 4.6, but alot of climbing to).  The engine has two piece pistons, although at the higher 18.7 to one compression ratio.  My question is this-has anyone installed a "smoke turbo" to maintain horsepower and to cut smoking at elevations?  I was thinking that if I used a turbo with a waste gate set at only 5psi, and possibly change the blower so the lobes have more clearance for the extra heat-this would work and leave the injectors the same.  Opinions?  Good Luck, TomC

[Kristinsgrandpa]

Tom, in case he doesn't read your post, Boogiethecat did exactly that. He is listed on the members list and can probably be contacted thru info on the BNO. IIRC he set his boost at 5 PSI, just for altitude, and it worked fine.     He was quite pleased with the outcome.

Ed.

[NewbeeMC9]

I saved this info from someone who had done the same thing  I've had these thoughts too:


"8V71 "A" Timed
N 70 injectors
Turbo
TV8101, P/N 5101508, 1.39 Ratio

I requested the turbo with the least amount of boost because I kept the
higher compression pistons.

I do not have any pictures but in the DD 71 service manual in section
3.3
page 1 figure 2 you can see the standard mount, there is nothing
abnormal
about this, the turbo is mounted just like it would be mounted in any
turboed bus or truck engine. I just kept the boost lower than the
normal
30 in. merc, mine maxes out at like 12 in. merc."

[Don Fairchild]

The turbo mount showned in section 3.3 page 1 is a industrial mount as opposed to an otm mount.
Tom how much room do you have between the top of the engine and the botom of the floor. Call me
@661-391-4520, i have some T18 and T18a40 turbos with  side mount manifolds and waste gates you might be intrested in.

You need to keep your boost at 7lbs or less. The turbo gary stadler used is a waste gated unit set at 5lbs. It is also on a 220 cummings. He did a nice job of installing it and he realy likes the way it runs. It is the same turbo I run on my 8V71TA that I have set at 28lbs of boost.

Jerry leblier and I had this conversation about three years ago and he runs i belive 9lbs boost with 18.7:1 pistons which I think has the potential to burn up the engine from to much heat.

Don

[boogiethecat]

Hi Tom,
Yup, I did stick a "smoke turbo" on my Crown, and it's probably the best thing I ever did to the bus.  It was a fairly simple job too, given what would be needed if you added more boost than 5-6psi...

I originally called Diesel Services  Colorado, talked to a really nice guy, Steve Rash 800-331-8934.  He took my engine info and had Garret size a turbo properly for the application. It cost me close to 2 grand.  I'm sure you could do it cheaper if you knew how to figure the correct waste-gated turbo...

Now a couple of comments about Steve... he was originally very helpful and I did buy the thing from him.  But there were a few glitches.
First, when my nice new $2000 turbo got here, it was loosely packed in a small box with only a handfull of peanuts as packing material.  Needless to say, the brackets holding the wastegate actuator, and the actuator itself, were totally bent up.  Very unhappily, Steve replaced the turbo with a second one, and he got fairly unfriendly to me over the issue.  I'm sure because he lost money on having to buy a second turbo, but it wasn't me who improperly packed it....

Second, I specifically told him I wanted only 5psi boost.  He'd assured me prior to the sale that the adjustable actuator would work at 5PSi. Well, it didn't. Prior to installing it, I set it up on my bench with a presure gauge and a compressed air supply... the actuator wouldn't even move until boost reached 15-20 psi.  I called Steve and he wouldn't replace it with a proper one.  I got a bit unhappy with him but he was absolutely not going to help.  So I ended up cutting the actuator open, chopping the spring down until it worked at 5psi, and then machined a couple screw rings to put it back together with.  That shouldn't have been necessary as Garret does make 5psi actuators.
  Anyway, besides that, one more thing to be aware of- Garret has ZERO customer service. You cannot contact them if you are an end user and if you have problems, your salesman is the only person they will let you talk to.  Being that Steve got pissy over the deal, I was stuck and on my own when I had a few questions.


Beyond all that, once installed, it worked immediately and it worked perfectly to plan.  The engine now thinks it's at sea level even when I'm up at 10,000 feet.  It took almost an hour off my trip to Burning Man.  I NEVER see smoke anywhere now, and if I was asked if I'd do it again, even with the supplier hassles, I'd say, ABSOLUTELY.

The plusses:
(1) you can install it without having to change pistons, compression ratios, etc.  This is great as it leaves you with a higer compression engine that will start easier in the cold than if you'd had to put in lower compression pistons.
(2) No more smoke, no more being passed by loaded concrete trucks when you're going up grades in altitude
(3) better mileage at altitude since you're now turning your precious $3+ per gallon goo into into horsepower instead of  black smoke
(4) you get that cool sound that turbos make (A bonus if you like it as I do)
Minuses:
It's a task to install but not bad if you can find the manifolds, etc at a junkyard
other than that, no minuses that I can see


A couple of  further comments regarding the 5PSI.  Why 5 and not 9, 15, etc? If you're interested, here's why:
When adding a "smoke turbo" to a formerly naturally aspirated engine, you have to compromise between how much extra grief you give your pistons vs how much performance you want at altitude.  5PSI is a good number because that much boost generally won't add enough grief to an engine to cause it to fail.  But why is 5 a magic number?

Because they are working against a spring with the diaphragm's backside open to atmosphere, wastegate actuators operate in the "gage" mode rather than "absolute", meaning that whatever boost they operate at is going to be referenced to atmospheric pressure. 5 PSi to a wastegate actuator really means, "5 psi more than whatever atmospheric pressure currently is".
If you do the math, you'll find that the difference in atmospheric pressure at 10,000 feet is roughly 5 pounds less than it is at sea level.  So when you're driving up at 10,000 feet and your boost is set to limit at 5psi, what's actually happening is that the engine is seeing sea-level pressure, NOT 5psi above that.

Put another way, when you set boost limit to 5psi, at sea level your engine will see an additional 5psi, and that [actual] pressure will slide down to zero boost (engine thinks it's at sea level) as you reach 10,000 feet in altitude.

If you pick a boost pressure higher than 5psi, you start getting into engine issues because now you're cramming more air into a naturally aspirated engine that it was designed to handle.  Compression pressure goes up and you can damage things. 

So that's where 5 came from- it's the best compromise between engine grief and decent performance at 10,000 feet and below.

[Jerry Liebler]

Since Don brought up my name, I'll jump in.  I do not have a turbo on my engine but may add one at some time.  I had my engine rebuilt at Hillsboro Diesel in Hillsboro Oregon.  The folks at Hillsboro Diesel have been rebuilding two cycle Detroits for over 30 years.  They insist they never use low compression pistons on turbo rebuilds, they once did and the customers complained of poor starting.  They have rebuilt many  hundred  turbo engines with high compression pistons and had no issues with any of them.  I also made the only change needed to make my engine like a factory turbo set up, that change is to use a 'large bearing' blower.  All factory turbo'd engines use 'standard' timing which is how my engine is and was.  As an engineer it's obvious to me that, how much power and heat is produced is controlled by the injectors (fuel flow).  If one starts with N65 injectors and standard timing and adds a turbo, even with 28 lbs of boost the only additional heat will come from the fuel that was unburned before adding the turbo. BTW, the horspower gain is also quite small. Diesels are not like Otto cycle (gas) engines and have no detonation issues so compression ratio need not be lowered when adding a turbo to a Diesel.
Regards
Jerry 4107 1120

[boogiethecat]

Jerry, I did a LOT of research and question asking prior to putting my smoke turbo on.  I would offer that while you may get away with 28 pounds boost and high compression pistons, you also may not.  Hillsborough may be doing that and they may be lucky, may be close, may be ok.  But because they do doesn't mean anyone should.

Burning fuel is not the only heat source. There is also the simple compression of air.  At 28 pounds you've almost doubled the amount of air molecules in a cylinder charge, and that takes much more force to compress given the same pistons.  That compression is going to result in a hotter air charge.  Granted if you don't increase the fuel you will not get more horsepower, but the combustion pressure will definitely raise a lot, and that is what can blow head gaskets and mess up engines.

My guess is that if Cummins, DD and most other diesel engine manufacturers install lower compression pistons in turbo'd engines, there's probably a good reason to do so.

So I'm not saying you're right or wrong... but I am saying that if any readers decide to add a smoke turbo and set it at higher than 8psi or so, they may be compromising their engine.

One last question: what's the point of running a smoke turbo above 5psi ?  If you're not adding extra fuel, I can't imagine why you'd do that if all you need is 5psi.  It certainly has no advantages that I can see, and it does push things.  Unless you just like good bragging rights (which is a decent reason I guess) , it simply pushes on reliability and there's no point in doing it, is there?

[TomC]

Thank you all for your responses.  After talking to many, including Don Fairchild (he does much in the way of mods to the 2 strokers), I'm going the route of 5-7 pound boost with probably 7G70 injectors since they have more tip holes than the N70, have a custome air to air intercooler made (have plenty of room in front of the radiator), and possibly change the blower, but with low boost, probably not.  And since I'm using low boost, a bypass blower probably wouldn't activate anyway.  I figure my output should increase from 318hp and 800lb/ft of torque to 345hp and close to 900lb/ft of torque.  But this isn't the point, the main thing is to maintain horsepower at altitude-which if your engine is not smoking, then you're using all the fuel for propulsion-which keeps your fuel mileage the same as sea level.  Good Luck, TomC

[Len Silva]

This may be a ridiculous idea but....  is it possible to use a high pressure electric blower on the intake to accomplish the same thing?

If it would work, it would be simple and inexpensive, turned on only when needed at altitude.

Len

[boogiethecat]

THEORETICALLY If you could find a blower that would create 5PSI at the cubic foot per minute that your engine ate, sure it would work.  The hitch is that you won't find a fan or electrical blower that is capable of this because it takes too much energy to do this job.

A turbo easily does this by consuming a massive amount of energy from the exhaust heat, and spins around at many,many  thousands of RPM to get it's little compressor wheel to do this much work.  I don't know what the equivalent horsepower is that a turbo rotor can create, but I'd be willing to bet that it'd be a 2dogs kinda thing (ie totally impractical with an electric motor).  Also the turbo pretty much grabs it's energy as "free" in that it doesn't particurlarly cause the engine to work harder to create it.  It's taken from the thermal energy in the exhaust that is otherwise dumped out the tailpipe.

So that's why a turbo is the best shot for this kind of application.  Not much else that is anywhere near "practical" will do the job at this time in history.  Maybe when we find a good stash of dilithium crystals, things 'll change... 

[tucsontattoo]

  You already have a fan blowing air into the engine. that is what the blower does. even as big as it is it can't provided enough air for the fuel we're trying to push through it. That is why the next step is to stack a turbo on top of that
               Tucson

[gcarter]

Two points.  In Minneapolis the DD dealer/distributor always rebuilds two strokes with high compression pistions.

Second I was told or read that all 92TAs use advance timing.

Gary Carter

[gus]

Early turbocharged light aircraft used manual wastegates, don't see any reason this wouldn't work on a bus. You could do your own boost controlling.

Some M35 "Reo" Army trucks used smoke turbos. These were for smoke control only on the Continental "Multi-Fuel" engines. One of these turbos might work. The engine is a 465ci.four stroke.

[TomC]

For purposes of comparing the 2 strokers to 4 strokers for air flow,  just take the bore and stroke, subtract 1 inch from the stroke then multiply that number by two.  So the 71 series would be the equivilent of 113 cu in per cylinder or 678 for the 6-71N and 904 cu in for the 8V-71N.  The 92 Series can also be done but subtract 1.1 inch from the stroke for 144 cu in per cylinder.  So the 6V-92 would be 864cu in and the 8V-92 would be 1152 cu in.  This is just an estimate.  Good Luck, TomC

[JackConrad]

That must be about right, I was once told my 8-V71 needed 900 CFM through the air filter at full RPM.  Jack