| Author | Message | ||
| Joe (Homermandy)
Registered Member Username: Homermandy Post Number: 16 Registered: 11-2006 Posted From: 69.133.104.177 Rating: N/A |
Ok, my next challenge. 6v92TA 350HP DDEC2. Previous owner stated that he could peg the boost guage near 30lbs. I never get over 21. I have removed muffler and gone straight 5", checked all intake hoses, etc. Even went to far as to spray light starting fluid near intake hoses to see if there was a leak. So I am stumped. I have had the turbo out and it spins freely and all fins are intact. Why would I not be getting more boost? | ||
| Sammy (Sammy)
Registered Member Username: Sammy Post Number: 69 Registered: 8-2005 Posted From: 68.237.201.131 Rating: N/A |
"Boost" is directly related to the amount of "load" you are putting on the engine at any given time. Here's an example - driving at 60 mph on a flat smooth road - not really much of a load on the engine - boost will be low.Now driving up a steep incline, trying to maintain 60 mph, this situation puts a larger load on the engine,requiring more turbo boost to make power. Where was he driving when he claims to have 30lbs of boost? How's your fuel filters and fuel pressure? Hope this may help. | ||
| Joe (Homermandy)
Registered Member Username: Homermandy Post Number: 17 Registered: 11-2006 Posted From: 69.133.104.177 Rating: N/A |
Fuel filters are new. Haven't checked fuel pressure though. I am waiting for more info from the previous owner, but my understanding is that was common boost. | ||
| larry currier (Larryc)
Registered Member Username: Larryc Post Number: 115 Registered: 2-2007 Posted From: 205.188.116.13 Rating: N/A |
Joe, a leak on the intake side would help your boost. A leak where the turbo bolts to the engine would hurt it as would a leak in the exhaust manifold gaskets and piping from them to the turbo. If you pull the part number off the turbo you can call DD and ask what its rated at. If its has the 25 lb rating (most common), then its not getting enough fuel from the DDEC. Max boost will be wide open RPM and throttle on a hard pull. If you can find a veriable in fuel pressure settings using the return restriction, I want to know about it. Seems like a small ammount of additional restriction could make a DDEC go. | ||
| Joe (Homermandy)
Registered Member Username: Homermandy Post Number: 18 Registered: 11-2006 Posted From: 69.133.104.177 Rating: N/A |
Larry, I'm sure I am getting enough fuel as if I get on it on a hill at max boost (21lbs in my case), I still get some black smoke. I have the TV8712 with A/R of 1.07 I believe. | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 39 Registered: 8-2006 Posted From: 74.33.61.139 Rating: N/A |
joe,i have a friend that has 2 6v92 625hp in his boat twin turbos at 2300 rpm under a load gets 21# another friend has a 12v92 twin turbos and gets 20# at 2400 rpm | ||
| Sammy (Sammy)
Registered Member Username: Sammy Post Number: 70 Registered: 8-2005 Posted From: 68.237.201.131 Rating: N/A |
DDEC 2 with the fuel plate under the ECM uses an R70 restrictor fitting.The fuel plate is used to cool the ECM. Non-DDEC uses an R80 restrictor fitting. | ||
| Joe (Homermandy)
Registered Member Username: Homermandy Post Number: 19 Registered: 11-2006 Posted From: 69.133.104.177 Rating: N/A |
Interesting. Could it be my max rpm is not high enough? I'm not sure how to find that out as I do not have a tach guage. Maybe when my engine was rebuilt the max RPM was dropped? | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 40 Registered: 8-2006 Posted From: 74.33.61.139 Rating: N/A |
joe,marine engines are set with a higher rpm than bus engines yours should be 2150 no load so i am not telling you that you need 2500 rpm ok | ||
| larry currier (Larryc)
Registered Member Username: Larryc Post Number: 118 Registered: 2-2007 Posted From: 205.188.116.13 Rating: N/A |
So can we buy a DDEC 2 ECM for a boat and get 2300 RPM? Has anyone tried a R60 restrictor on the 6V92? Joe, alot of these were 1950 RPM @ 300 HP or less. Hook a reader up to find out what you really have. Anyone know if there is a high altitude mapwidth turbo available for the 6V92? I see no advantage to twin turbos if they don't push any more air than the TV8712, whats with that? | ||
| Craig (Ceieio)
Registered Member Username: Ceieio Post Number: 289 Registered: 12-2004 Posted From: 206.212.230.165 Rating: N/A |
Joe - another possibility is that by adding a larger pipe and removing the muffler, you will not build the higher boost. I have more experience with gasoline racing engines than diesel, but I think to a degree the effects described below hold with a diesel. When you increase the flow rate through the engine (porting heads, removing back pressure in the exhaust like you have, and so on) you may need to go to a bigger turbo or increase the drive rate (and or size) of your supercharger (gas engine) to regain boost pressure. On your Detroit, the right way to go is the turbo size. Think of it like blowing through a straw. If you blow hard through a coffee swizzle stick, pressure builds fast and peaks quickly too. Change to a straw from a quadruple big-gulp and blow the same and more air will go through the straw, but at a much lower pressure. So the good news is, more air is going through your air pump (engine), but your power adder (turbo in your case) may not be able to max the system out with fewer restrictions in it (result of the exhaust changes). If all this is the case you may have to step up to a bigger turbo to reach those pressures again. The good news, on a gas engine at least, is that when you remove airflow restrictions you are indeed moving more air through the engine with less work and therefore are most likely making more power (if you tune the fuel delivery to match). Might be something to ask your favorite diesel mechanic about. Craig - MC7 Oregon | ||
| Joe (Homermandy)
Registered Member Username: Homermandy Post Number: 20 Registered: 11-2006 Posted From: 66.195.237.160 Rating: N/A |
Craig, I had this issue before removing the muffler. Actually I gained a few pounds of boost and my throttle response increased greatly by removing the muffler. It is actually not much louder without the muffler and the jakes sound pretty neat too. | ||
| Craig (Ceieio)
Registered Member Username: Ceieio Post Number: 290 Registered: 12-2004 Posted From: 206.212.230.165 Rating: N/A |
Joe - That's a head scratcher for me; I would have bet my two cents the other way on that one. Please post follow ups as you work out the problem as I (and perhaps others) have much to learn in this area. Unlike when I was in Mrs. Luce's fourth grade English class, I actually like learning new things now! :-) | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1245 Registered: 12-2000 Posted From: 67.181.189.94 Rating: N/A |
Here's an interesting bit of turbocharger trivia: On the Corvair Sypder/Corsa turbo models, the exhaust system was tuned so that the back pressure in the muffler would build to the point that boost would be restricted when the engine hit about 5800 rpm under full load. Was a way to build-in longevity and keep the engine from self-destructing. In the meantime, Joe, it's entirely possible that the P.O. was using 30psi as a sales gimmick, since 20 - 25 psi seems to be about normal for these. FWIW & HTH. . .  | ||
| Joe (Homermandy)
Registered Member Username: Homermandy Post Number: 21 Registered: 11-2006 Posted From: 66.195.237.160 Rating: N/A |
RJ, I talked with the previous owner a year after I got the bus. They were leasing it I believe. The guy I need to talk with was the driver and I haven't gotten him to contact me yet. One of the band members recalled the 30psi, but I wanted to verify. | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 180 Registered: 8-2006 Posted From: 207.231.80.150 Rating: N/A |
Here's my nickel, Turbo output is a direct result of exhaust flow into it. We'll all agree on that. Now where is the maximum exhaust output? At the nearest point to maximum governed speed, at full throttle, just before the governor (either mechanical or DDEC) begins to reduce the fuel 'rack' to avoid exceeding max set rpm. Pressure will be higher on a cool day. Exhaust output is just a function of fuel input, and engine rpm. If you have any amount of smoke after 2 or 3 seconds of full throttle, either the engine is over-fueled, (too big injectors, or too high horesepower setting) worn injectors, dirty air cleaner, too small air cleaner, restrictive piping, wrong turbo. Who worked on it first? Maybe I should have said last? (Before you) We do need to know max governed rpm, or, how fast will it go on the flat, and what's your axle ratio? George | ||
| Donn Reeves (Donnreeves)
Registered Member Username: Donnreeves Post Number: 3 Registered: 3-2007 Posted From: 69.115.76.219 Rating: N/A |
I have a 350HP MUI 6V-92 and my max boost is 20#. You would need a huge turbo and really big injectors to see 30#, but it sure would make horsepower. | ||
| larry currier (Larryc)
Registered Member Username: Larryc Post Number: 120 Registered: 2-2007 Posted From: 64.12.116.203 Rating: N/A |
Actually the smaller turbo housings make more boost than large housings. |