Increase in power at high rpms recently

[m16ty]

The last couple of times I've been in my deuce, the truck has a noticeable increase in power at high rpms. I mostly notice it going up a slight grade under moderate load. What happens is when the rpms get up around 2400 or so, the turbo will change to a higher pitch (C turbo), the boost will jump way up, and there is a noticeable increase in power. It doesn't do it all the time, just when the conditions are like described above.

I've got a pyro and boost gauge. Normally I run about 9-10 lbs of boost and 1,000 egt max. When the turbo pitch changes the boost jumps way up. I've seen it hit 14lbs and still climbing when I let out of it for fear it's fixing to self destruct. It comes on all of a sudden like you flipped a switch. Not unlike nitrous in a race car. I know I'm trying to compare a deuce to a race car but you get the point, it comes on that fast and while it won't pin you to the seat, it is very noticeable.

I fear this is the truck running really good right before it takes a dump. Has anybody ever experienced anything like this? The turbo is screaming so loud during this that it sounds like it's overspeeding and fixing to fly apart.

 

[jake1086]

I've always heard engines run great before they blow up haha but I think that usually has to do with the engine leaning out... I dont even know if diesels do that??

 

[m16ty]

No, diesels won't run lean like a gas engine will. You either have fuel or you don't and fuel equals power and heat in a diesel.

 

[FASTNOVA]

I would have that turbo checked out. You don't want it to let go then you'll have a big mess on your hands.

 

[welldigger]

I dont believe its the turbo. I would pull your injector pump and have it looked at. Sounds to me the IP is dumping more fuel than it should. More fuel pumped in then the more exhaust gas. More exhaust gas means your turbo will spin faster. Spin your turbo faster and you get more boost. See the chain reaction here?

 

[skav]

The last couple of times I've been in my deuce, the truck has a noticeable increase in power at high rpms. I mostly notice it going up a slight grade under moderate load. What happens is when the rpms get up around 2400 or so, the turbo will change to a higher pitch (C turbo), the boost will jump way up, and there is a noticeable increase in power. It doesn't do it all the time, just when the conditions are like described above.

I've got a pyro and boost gauge. Normally I run about 9-10 lbs of boost and 1,000 egt max. When the turbo pitch changes the boost jumps way up. I've seen it hit 14lbs and still climbing when I let out of it for fear it's fixing to self destruct. It comes on all of a sudden like you flipped a switch. Not unlike nitrous in a race car. I know I'm trying to compare a deuce to a race car but you get the point, it comes on that fast and while it won't pin you to the seat, it is very noticeable.

I fear this is the truck running really good right before it takes a dump. Has anybody ever experienced anything like this? The turbo is screaming so loud during this that it sounds like it's overspeeding and fixing to fly apart.

How high are your EGTs at 14psi? Your ok up to 1250, and you won't hurt the motor up to 20psi. It could be the waste gate sticking too.

 

[Stretch44875]

I've noticed a increase in power right before the filters plug... Not sure why, but 100 miles before the filters need changed, it will blow black smoke, egt's north of 1300, and have a lot of power. Then it falls on it's face, LOL.... I think some how the filters are causing the fuel to have high pressure. It sounds backwards, but has happened many times now. Not so much since I started using a centrifuge to clean the fuel,(UMO) filters last longer now.

 

[gimpyrobb]

Pull your air intake and wiggle the turbo shaft. Make sure its not loose.

 

[moriboy]

Have you noticed any engine oil loss? If so you could be losing it thru the turbo as mentioned earlier. The added oil would act just like adding more fuel. Be very careful, a diesel burning it's own oil can be very scary.

 

[rchalmers3]

Ty, have you experienced the symptoms with a full tank of fuel?

I have a Ford 7.3L with an aftermarket turbo that surges as you describe. It happens when the fuel tank level is low. I assume the problem is that the pick up allows for shots of air bubbles to enter the fuel system, causing a variance in available fuel shots per stroke. Refueling the tank makes the symptoms go away.

Rick

 

[Wildchild467]

Mine seems to run a little better at 2250 compared to my usual cruise speed of 2100-2200. I can’t say much about the boost, but it definitely likes it. I never let it get above 2300... EVER. The whole throwing a rod thing scares me. I think some of it could be the centrifugal timing advance in the pump, or just more efficient combustion at the higher speed? My problem could be also the engine is getting loaded up and needs more highway speed to clean it out. Last weekend I had to go about 45 miles somewhere and opted to take a route that was fairly flat the whole way even though it was 5 miles longer. The reason was so I could run the engine at a higher RPM for a sustained period of time to help clean it out if that is the problem. I checked my fuel pressure and that seemed good, so I don’t think that was the problem. It definitely helped taking it on a longer trip like that to help clean it out. I burn WMO and I think that can cause the engine to load up if not allowed to fully warm up to 180 degrees and be taken on long trips. It never hurts to put clean filters on either just to make sure. I would like to put a fuel pressure gauge in my cab also so I can keep an eye on the fuel pressure when I am driving. I think it would be interesting to study them at road speeds and observe what happens when fuel pressure drops as filters clog and boost and EGT. I know Doghead told me as filters clog, the EGT’s can get higher than usual.

I can relate somewhat to what you are saying M16TY a little because my truck seems a little the same. I have a D turbo by the way. Try checking fuel pressure at 1800 rpm to make sure you are within the specs of 55-65psi or put new filters on. Then take it for a good long drive at constant engine speed. It helped my truck last weekend. Once in a great while, I can hit 10psi of boost, but no more. If I drive it around town for a while and to and from work, I can’t get much over 7 psi sometimes. After I take it on a long trip, I can get 9 with no problem. I would think a lot of the time it’s the filter, but after last weekend checking the fuel pressure, all it needed was to get out and stretch its legs…. And it was fun doing it!

All respect to what other people say on here as suggestions, i totally agree. Its always good to check the basics, adjust the valves, check timing, etc. You never know until you check.

 

[Kohburn]

could be increase of oil pressure at higher RPM is causing oil to get past the rings or past the seal in the turbo. if that is the case then continuing to get worse could lead to a runaway.

pull the intake - inspect for oil slick, inspect turbo shaft for slop

 

[welldigger]

I've noticed a increase in power right before the filters plug... Not sure why, but 100 miles before the filters need changed, it will blow black smoke, egt's north of 1300, and have a lot of power. Then it falls on it's face, LOL.... I think some how the filters are causing the fuel to have high pressure. It sounds backwards, but has happened many times now. Not so much since I started using a centrifuge to clean the fuel,(UMO) filters last longer now.

Actually Stretch may be on to something. I had an old Quincy air compressor with an I-4 Hercules diesel. It didn't have a fuel guage so I would sometimes forget to fill the diesel tank. Whenever the tank would run dry the engine would almost run away and then die. First I suggest changing the all 3 fuel filters. Then check for leaks in your fuel line. A buddy of mine has an old fire truck with one of those old Detroit 2-stroke diesels. One of the dangers of those engines was if you sprung a leak in the fuel line and introduced air into the fuel the engine would run away and the only way to control it was to close a flapper valve on the supercharger and choke the air off.

 

[m16ty]

I checked the turbo a couple of hundred miles ago but I'll check it again. It just started this the last couple of times I took it out.

I don't know what the EGT will go to when this happens because I let out of it for fear something is fixing to fly apart.

The comments about air in the fuel system may carry some weight. The other day I started it and it ran for a few seconds and then died. Tried to restart but it wouldn't. I opened the filter bleeder with the tank pump on and I got a little air before a full fuel stream so I know I'm getting a little air somewhere.

 

[PsycoBob]

Isn't it great when a line that handles 60-70psi at full throttle won't leak fuel, but it'll leak air when its not pressurized?

Foaming engine degreaser & a hose works wonders for cleaning off any oil/fuel that might make locating a small leak hard. Took quite a few applications & a lot of water to track down a couple of minor oil leaks I had. Reminds me, I need to go spray my filter housings down- I think one's got a slow leak, causing my hard starting.

 

[rlsnide]

Maybe you could check your throttle linkage maybe when in gets that 14 psi of boost maybe that is actually full throttle and other times its not. Mine runs 15-16 psi of boost and 1250 egt all the time while under a load. That is on a C turbo also. I just recently (yesterday) put a D turbo on mine to lower the EGT's at high RPM's. Nothing may be wrong with it but just not going to WOT all the time.

 

[RedbeardTheZombieHunter]

How high are your EGTs at 14psi? Your ok up to 1250, and you won't hurt the motor up to 20psi. It could be the waste gate sticking too.

A2s don't have a waste gate, and an EGT reading of 1250 at the exhaust inlet at the turbo means you're WAAAAYYYY exceding the 1270 damage limit in the combustion chamber and melting the tops out of the pistons as well as softening the corners of the veigns on the impeller in the turbo. If you're reading EGT in the usual spot in the exhaust manifold right in front of the turbo inlet, never, EVER let it go over 1000 degrees as the temperatures in the combustion chamber will be around 150 to 200 degrees higher than in the manifold.

 

[67 evil eleanor]

Can worn injectors cause this by allowing too much fuel and not O2 for a healthy burn (I'm trying to learn). on edit, I looked at the Banks info site and seen a couple of things that makes sense. If the air is restricted due to a dirty filter or physical restriction in the intake, it will cause it to run fat and increast the EGT. Also, if there is a restriction in the exhaust, the EGT will go up. It even said that if the cooling system is not up to snuff, that can cause higher EGts.

 

[m16ty]

If you're reading EGT in the usual spot in the exhaust manifold right in front of the turbo inlet, never, EVER let it go over 1000 degrees

That figure is a little low. Most authorities on the subject say 1200-1300 deg on the pyro pre-trubo as the max temp. From my experience, you can run 1100-1200 all day long and 1300 in short periods without harm.

 

[Flyingvan911]

My deuce with LDS maxs out at about 1200 degrees with my foot on the floor going up a steep hill (pre-turbo). Boost is at 12 psi with an occasional peak to 13. The fuel is still set where the SDNG had it.