Turbo boost on 6V92

[lostagain]

The most boost I have seen is 18 psi, in 3rd gear climbing a hill at full power at about 2000 rpm near the governor. (9G90s w/ TV7512). Should I get more? What kind of boost are you guys with 6V92s getting? I am asking because I have a small exhaust leak at the pipe flange between the left manifold and the turbo. I am going to fix that soon. Just wondering how much of a difference it will make.

JC

[luvrbus]

Depends on the A/R on the TV 7512 turbo the 1.23 should be around 21 to 23 lbs the 1.03 will get over 25 lbs

[Iceni John]

My 6V92TAC (the Californicated 277HP version) has 26 PSI boost maximum.   That's at WOT at just under 2,000 RPM, measured on my VDO boost gauge that reads from the driver's side of the blower housing under the turbo.

John

[lostagain]

Thanks Clifford, I am pretty sure the A/R is 1.23. So after fixing the exhaust leak, I should see a little over 20 lbs. Great! More power! Although it goes pretty good already for an old 2 stroke. Top of 3rd gear at 55 mph climbing out of Butte, MT northbound on I 15. An NA 8V71 would be in 2nd gear at 30-40 mph.

JC

[lostagain]

John, do you remember what injectors and turbo do you have?

JC

[luvrbus]

John's CA engine should have 9G75 or 9S75 injectors with the TV7511 turbo with a A/R of 0.96 that was the standard for the CA engine the boost gets up there on those engines up to about 28 lbs problem with it they have no high torque like yours 

[TomC]

The big question is-are you getting any black smoke when climbing a hill? If not, you're OK. Good Luck, TomC

[skihor]

I don't know what turbo I have. The injectors are 9G95. I was told that the turbo "matched" the injectors to produce 350 HP. Normally the boost is 15 to 17, the most I've seen is 18. The exhaust system is tight and right.
Don & Sheila

[luvrbus]

Don the 9G95 is a big injector for a 350 hp it would interesting to know the setting and the turbo # on the engine the 9G95 was used in the 6V92- 400 hp fire truck engines 

Blowers play a big in turbo boost the full by-pass blowers are always lower than a mini bypass or a non bypass blower 

[bevans6]

To carry forward Clifford's thought, the turbo develops pressure based on two things - it's capacity spinning at the speed the exhaust happens to spin it at, and the restriction it is blowing into.  The blower is the big gatekeeper into the engine, so if it is non-bypass it will have the most restriction and the turbo will develop the highest pressure.  If it is a bypass blower the pressure will be equalized on both sides of the blower, it will present less of an restriction and the pressure will be lower.  I haven't fully decided what my thinking on this is, but it's my current thought that aside from the amount of air that actually goes through the bypass orifice, and the additional load it takes to spin the blower under higher boost, the actual amount of air that gets into the engine is going to be close between bypass and non bypass.  The bypass blowers will always win on efficiency and power, but a non-bypass blower (which is what I have) is going to do fine as well.  I've already been told my turbo is a fairly low boost, high volume turbo and that matches with the non-bypass blower.  Plus it's a tank engine, and making copious smoke under full throttle amused the troops...   

Brian

[HB of CJ]

Good thread and thank you.  HB of CJ (old coot)

[skihor]

Don the 9G95 is a big injector for a 350 hp it would interesting to know the setting and the turbo # on the engine the 9G95 was used in the 6V92- 400 hp fire truck engines 

Blowers play a big in turbo boost the full by-pass blowers are always lower than a mini bypass or a non bypass blower 

I got the set up from Jim Sheppard. He said that it was for a 350 hp set up. I have often wondered because first of all it is impossible to cool, even after I added 2 more rads. Sealed, new cores, etc... It has the MC9 blowers too.
I do know when I can use all of the throttle this bus really hauls @$#. @ sea level and 50* F ambient I can use it all. @ 6000' only if it's below freezing. In the summer, 75*F, @ altitude I can't exceed 10 lbs boost for long or over heat.

[lostagain]

Tom C, it will smoke with my foot to the floor. But I can manage it quite well by looking at the exhaust in my mirror. About 3/4 pedal travel is usually all I need for power without rolling too much coal.

I have a mini bypass blower.

Ideal conditions is this time of year, or winter when heat is not a concern. In summer heat, like in the 30s C or over 100F, I have to back off the accelerator pedal or even drop down a gear to keep it cool up a hill. I do have MC9 rads and the 12" blower fans with smaller pulley.

It is indeed a balancing act between making more power, and keeping those 2 strokes with rear mounted rads in a bus cool.

I like tweaking it a little more every year. That is some of the fun about the hobby. Once I can complete my honey-do list  , I am going to fix my exhaust leak and remove the muffler and replace it with a resonator like has been discussed on the board lately. Trying to squeeze a little more out of it...

JC

[akroyaleagle]

J.C.

The quickest way to "squeeze" more out of it may be to ensure you have a filter that allows enough air through it.

My 92 has 9A98 injectors. It runs great and doesn't make smoke.

I ended up going to Donaldson and the Phoenix manager sat me down and explained how to size a air filter by CFM.

I don't know all the particulars but you may need 1600 CFM air capacity to get the most out of your engine.

I am a simple guy, not a Detroit mechanic. But I understand power is a function of fuel and air in the proper mixture.
Black smoke means there is not enough air available to properly combust the fuel. that could be because the turbo is not working right, the filter is restricted, you are above 4000' with a NA engine or just altitude with any of the motors.
The throttle delay prevents black smoke by delaying throttle input until the turbo spools up. I left the throttle delay off mine. I just don't drive with the pedal flat on the floor. If you allow the RPM to drop too much in a climb, the turbo speed doesn't allow enough air so you make black smoke. A properly matched setup doesn't smoke anytime. If the injectors are clogged, burnt or not set correctly, That causes black smoke also.

Any outfit making black smoke is simply not right for one or more of the above reasons.

If it's making blue smoke, it's burning oil.

If it's making white smoke, coolant is getting someplace it shouldn't.

If all the cars passing you have their wipers on when there isn't any rain, they are not waving, they are mad. You are leaking fuel, oil, sewage or something!

[luvrbus]

Don't leave out the exhaust system causing black smoke either, everything can be perfect on top and not enough CFM flow on a muffler they smoke and that is what I like about a resonator on a turbo engine or dual mufflers on a 8v71 N/A engine