Aaaahh, now I am starting to understand. Do you think that components can be beefed up enough to function properly at such a high pressure the same way that I have beefed up the rest of the engine?

Or should I contact PacBrake and see what they say?

 

D.Wiggs. F1 springs will help big time. My guides and seals were completely shot with tons of carbon build up on the back side. My F1 springs were a late addition and I had already trashed my valvetrain in a year of exhaust braking with only stock boost levels and moderate power towing heavy. In my mind you could never bomb proof the valvetrain to stand up to longterm exhaust brake use in high psi - high power engines. ks

 

If you used the F1 springs from the beginning, would you need to replace your valve train once a year, or once every two?

About how much does that cost?

Thanks for all of your help!

 

With F1 springs you may never have any valvetrain issues. F1 springs are about $650 or so if I remember. To replace the valves, seats, guides, and seals with a shop doing all the work is about $3000 as the head has to come off....new head gasket and with twins about 30 hours of labor. Springs should last for the lifetime of the head. Don't get me wrong I loved my pacbrake but now that I know what it does to the engine with high power and heavy towing...I'd never have it on a motor over 350hp without great valve springs and never on a motor over 450hp. ks

 

I guess I'm missing the logic here. Why would boost pressures have anything to do with an exhaust brake. They should only engage when your foot is off the throttle. That leads me to think it doesn't matter what is in front of the brake. One turbo or six, it's all the same to the brake. Also, don't they limit the back pressure that the valve will open and close at?

 

That's a good point. I am curious about that.

 

I'd love to pontificate for ever on this point but....You'll see....if you think your twins stop spitting out huge volumes of air the second you let off the pedal instantaneously well your in the land of easter bunny, santa, and the tooth fairy. Most e-brakes have about a 1 to 2 second delay that lets the stock fuel finish burning and evacuating before they come into full force. If you run a compressor(vacuum pump) or a pedal switch they come in almost instantaneously. Where does that exhaust go that you've retarded and what is providing the braking force that you are utilizing... that is provided by the trapped energy between the butterfly valve and the valvetrain. When the exhaust brake comes on some of the valves are open and suddenly a nice rush of pressure that builds in the cylinder keeps the valve from gently settling back into its seat an it flutters down to the seat like a metal ball bouncing on granite. Do this millions of times and the seat becomes loose and the valves become flattened out on the contact zone. You reminded me that when I picked up the head I forgot to get the broken parts. Yes the exhaust brakes are designed to limit backpressue by not fully closing....With my power that I had.....sometime the valve would stick completely for a second or sometimes longer once I finished braking and wanted to go because the engagement pressure was higher than what it was designed for. A PXRB on a 5" application for a dodge is designed for maybe 22psi operating, 40 psi max. You will be hopefully way above this.

My final point on this matter is this... the brochures, the want to be exhaust scientists, and the companies tell you what they need to, think, or whatever it takes to sell you a product that is valid for Grampa or Camper Clint. I know from personal experience and lots of discussion with the diesel mechanic of 40 years that is also a race engine builder that an exhaust brake is not a good idea on a over fueled, high power diesel engine. 400hp engines have engine brakes which take the strain off the valvetrain. I can only advise, what you do from here is your decision, Good luck can't wait to see the results of your effort, best regards ks

 

Shhhh. Better hope Begle doesn't read this, because I dont' think he could take the shock of finding out the land of the easter bunny and santa isn't real... He doesn't care about the tooth fairy...

Sorry, couldn't help myself.

Buy a better braking system (new pads, rotors, and calipers. MAYBE a master cylinder) and ditch the PAC brake. ALLWAYS listen to those who can say "I sure won't make that mistake again"

 

This exhaust backpressure vs remaining boost vs volume of exhaust charge is interesting and something that I'm not going to offer an opinion on as I simply don't know!

What I do know is that I've personally seen a high number of valve guide and valve seal failures on 2nd and 3rd Gen. 24 valve heads. None of the ones I'll mention had an exhaust brake installed but all had been modified for horsepower. A low mileage '06 with only an aftermarket air filter and CLDL charred and melted the exhaust valve seals and blew some of the intakes off. (The piston may be oil cooled but think how hot the exhaust valve stem gets while overfueled) Several streets driven, sled pullers, with aftermarket singles had worn out valve guides at ~20,000 miles. Most pulled their heads due to a blown head gasket, wanting to oring the head or broken injector tip damage. I thought it was common knowledge that with high boost twin turbos you didn't bother to install/run valve seals simply because they failed?? Valve float is very common on 24V engines at boost pressures over 40lbs or with high rpm/drive pressures. It's enlightening to measure drive pressures; I've seen 75 lbs on a stock turbo with nothing more then a TST CR. I've seen valve/piston imprints on stock turbo trucks. Fortunately the valves don’t seem to mind! Some twin turbo will run more then 1 - 1 backpressure at higher boost levels and the valves will bounce on the seat even with aftermarket springs which exposes the valve guides/seals to way more pressure and heat then they are designed.

My first exhaust brake was a 2nd Gen Cummins/Jake/Dodge turbo mounted unit that worked fine but restricted the exhaust horribly. I then went to a 4" inline BD which was adjustable and ran as high as 60lbs braking pressure (OEM brake maxed ~35lbs.) The BD is best working brake that I've tried. I hooked it up with the OEM peddle switch but, on it, and following brakes only used a manual switch on the gear shift. IMO you don't need instant on exhaust braking and manual control takes care of the delay and high flow/boost issues. Third Gen trucks have great disc brakes and stop my trailer just fine without an exhaust brake but ebrakes are nice for fast winter warm up and long down grades. Thinking more HP, I then wanted a 5" ebrake and had Pacbrake to make an inline "slammer" similar to their medium duty truck brakes. I haven't pulled the head on my third Gen but I wouldn't expect my valve guides to be good for 100,000 miles, even if the engine were stock, with or without a brake. The 24V valve guides are tiny and the rocker arm/cross over/valve geometry is so poor, compared with most modern engines, (or a 12V CTD) that I think we'll just have to live with some wear issues.....?

 

Roger, I agree completely with your comments. The exhaust brake IMHO just doesn't make a bad situation better. I had no valve marks on any of my pistons except for the ding in #5 where the valve was bent and seat out of place. Exhaust valve seals are easy to change now that I know what to look for and will not doubt be a regular maintenance item. Good springs I think will make all the difference. 60# regular springs are better than stock for sure. The higher the boost the harder the valves will hit the seats for sure. Great info for everyone in this post. ks

 

abc4yew,
I appreciate all your work, mod's and sharing it with others. These third gen. trucks are not yet a known quantity but you are pushing the envelope and we all gain from you experiece and....pain. I sure hope that some of your "pain" goes away and you get back on the road quickly.

 

I had someone check with Don at F1 today about my setup and Don said that if I do the F1 Springs, I will have no problems at all using the PacBrake.

I thought that was interesting info considering who it came from and thought it would be a good idea to share it with you guys.

 

Yep, If I had F1 springs in when I put the PacBrake on....I wouldn't be replacing seats and valves ...maybe guides and seals but not seats and guides......guides and seals are just a maintenance item like brake pads or rotors....just alot cheaper. ks

 

Very good info. Thanks!

 

The Springs and injectors will be in on Monday and the CP3 should be in on Tuesday! Wednesday is the date we are shooting to finally have her finished!!!!!!!!!!!!!!!!!!!!!!!!!!!