buddy
Active Member
Having smoke doesnt necessarily mean you need more boost. Could be poor fuel atomization, too much advance, too much drive pressure on the turbo, too high of IATs. Ect....
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Tahoe Motor Is Blown Up
- Thread starter 6.2 turbo
- Start date
uniquediesel
1/4 mi. Fan
- Messages
- 245
- Reaction score
- 38
buddy,
Next time I crank it up I've got a some tasks... Two are on your list.
Drive pressure, going to answer that one, installing yet another gauge
Timing, I need to re-verify where I'm at, doesn't seem like too much advance though, got the meter might as well use it.
I also went from 18.0:1 to 17.1:1 and I regret it dearly. 18:1 is the perfect performance C/R IMHO.
Next time I crank it up I've got a some tasks... Two are on your list.
Drive pressure, going to answer that one, installing yet another gauge
Timing, I need to re-verify where I'm at, doesn't seem like too much advance though, got the meter might as well use it.
I also went from 18.0:1 to 17.1:1 and I regret it dearly. 18:1 is the perfect performance C/R IMHO.
6.2 ---- I really believe that a lot of your trouble started when you cemented your block and didn't bore it. If you only filled to the bottom of the water inlet you would not have a large heat build up at the bottom of the cly. The bottom of the inlet is around 3" down the deck, that is where all the heat is. As I said before, I cement a lot of blocks, BUT you must let them cure for weeks then do the machine work, heating the block in a oven will speed up things, but my coating oven isn't big enough to get it in there, so I always wait 4 weeks to do machine work..
Chevydiesel... you said something about checking your timing, what year motor..... DB2 or DB4 ??? what kind of gauge are talking about???
buddy
Active Member
How did you get down to 17:1 CR? Piston shave or dish, or gasket? Even at 17:1 CR if you run 35psi of boost the stock injector pop pressures aren't adequate. You should have them set to 2500psi to ensure they are popping at higher pressure then the air pressure in the cylinder. Otherwise you wont get good atomization and can foul up the tips. Do you have a working fuel heater? Because that greatly improves atomization and will combust the fuel better.
You cant check full load timing,except on a pump stand. I have a meter,any smoke,and it will stop reading. Idle and light load works fine. Chevydiesel I'm surprised that a DB pump can fuel 100cc at 5600 rpms. There is not enough plunger fill time.
turbonator
Member
Hope I am not stepping out of line here, but the pump that chevydiesel is using is a .330'' plunger pump. Similar to the pump you have now Chris....glad to see you posting with us chevydiesel......
uniquediesel
1/4 mi. Fan
- Messages
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- 38
Couple of timing meters. I have the lumy probe version Snap On, I also have the injector line clamp-on style that you use a timing light with. I usually use the lumy probe one because I'm not 100% the timing tab on the front of the engine is accurate.
Yes, .330" plunger pump. Trying to get everything I can from this one before throwing on my DB4 (preliminary results it's making almost twice at certain speeds), not quite ready for the truck right now
Injectors, nope not 2500 psi, they don't make power that high pop pressure. 311 nozzles set at 2100 right now. The book calls for 2200 on 311 nozzles.
Considering removing these injectors and having them tested. These came from my tow-rig suburban, I stole the ones in the race truck while it was sitting to troubleshoot a knock issue on the suburban. Thinking the ones from the suburban (were setup the same way, but more miles) might not be as hot as the ones that were in it. So, may just build a new set. The knock issue is that 311 nozzles on DS4 pumps cause the engine to be knocky when cold, and certain cylinder temps. So i swapped the stuff out and no change, just fyi.
No Fuel heater, not necessary in the summer. Fuel cell in the back of the truck gets plenty warm in the sunlight.
When I had the engine out to replace head gaskets (thought I holed a piston) but gasket failed in a weird way allowing compression into crankcase I used the .010 thicker Felpro gaskets. It was spot on 18.0:1 before I thought I needed to drop the C/R. It takes .011" for one C/R. So it's ~17.1:1. I didn't need to drop the C/R, all I needed was to get heads that were good and straight, thought they were before, nope. They are now.
I think I'm too big turbo wise, on the drive side. We'll see what kind of drive presssure I got then move from there. Then I'll either build a custom turbo, or make some twins out of turbos I have laying around.
The truck is mainly a rolling dyno/test rig right now.
Yes, .330" plunger pump. Trying to get everything I can from this one before throwing on my DB4 (preliminary results it's making almost twice at certain speeds), not quite ready for the truck right now
Injectors, nope not 2500 psi, they don't make power that high pop pressure. 311 nozzles set at 2100 right now. The book calls for 2200 on 311 nozzles.
Considering removing these injectors and having them tested. These came from my tow-rig suburban, I stole the ones in the race truck while it was sitting to troubleshoot a knock issue on the suburban. Thinking the ones from the suburban (were setup the same way, but more miles) might not be as hot as the ones that were in it. So, may just build a new set. The knock issue is that 311 nozzles on DS4 pumps cause the engine to be knocky when cold, and certain cylinder temps. So i swapped the stuff out and no change, just fyi.
No Fuel heater, not necessary in the summer. Fuel cell in the back of the truck gets plenty warm in the sunlight.
When I had the engine out to replace head gaskets (thought I holed a piston) but gasket failed in a weird way allowing compression into crankcase I used the .010 thicker Felpro gaskets. It was spot on 18.0:1 before I thought I needed to drop the C/R. It takes .011" for one C/R. So it's ~17.1:1. I didn't need to drop the C/R, all I needed was to get heads that were good and straight, thought they were before, nope. They are now.
I think I'm too big turbo wise, on the drive side. We'll see what kind of drive presssure I got then move from there. Then I'll either build a custom turbo, or make some twins out of turbos I have laying around.
The truck is mainly a rolling dyno/test rig right now.
uniquediesel
1/4 mi. Fan
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- 38
It's around 100cc at 5500, at 5600 it's on the gov at 15cc
uniquediesel
1/4 mi. Fan
- Messages
- 245
- Reaction score
- 38
One thing caught my attention, that's out of order here. The air pressure in the cylinder when it starts to spray is only 325psi. An 18:1 engine makes 350psi of static compression. Should be good to go at 2100.
buddy
Active Member
Not really, thats the dynamic crompression at cranking speeds where it has loads of time to bleed past rings. If you were to put a 24V starter system you would even get more like 450psi while cranking just because youd get another 50-100rpm cranking speed. The static compression if you had no blowby, at 17:1 CR is more like 760psi, and it would approach that as RPMs increase and there is less time for it to bleed down.
Now throw in all that extra pressure of boost and compress it too and you are over 2200psi by the time you reach TDC. This is how you blow head gaskets with boost and bend rods, ect.... At 35psi you have increased the starting pressure by a factor of 3.4, since it normally starts compressing at atomospheric of 14.7psi, add 35psi of boost and youre starting to compress at about 50psi, then do the math of compressing air to a 17:1 ratio and its about 2600psi at TDC. Since there is blowby, it bleeds off some.
311 nozzles by the book are 2200psi, but boost by the book is only like 12psi. By increasing boost youve considerably changed cylinder pressures. Besides that, higher pressure atomizes fuel better, and also the warmer it is. And if you have too much fuel mass to begin with, warming it up will decrease the mass slightly as well so it doesnt waste fuel. Since the molecular weight and viscosity of diesel fuel is so much greater than that of gasoline its typically warmed up even in summer to reach better injecting temperatures. And by that I mean somewhere around 130-150F.
Same pump I am going to use, never heard of a timing meter before, I might need some more info before long,,,,,,
I must remember this........
Had a long talk with Bill today. I'm trying to figure out what he does to get such high hp,and never bends rods or blows head gaskets. He thought it would be impossible to bend rods with cyl pressure,even with too much timing. The only thing I might try, is get the powerband up higher. I also suspect we are not on the same page as far as horsepower estimations. What he thinks is fast might seem slow to me,who knows ?
uniquediesel
1/4 mi. Fan
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I've said it before, and I'll say it again until people start to believe me. Bills 500HP claim is complete B.S. Period. I'm working on a way to prove it. He ain't got the backup. Ever see any dyno results, exactly...
I think your rod issue is clearance related. Galling in the cylinder is both pulling the rods apart and bending them trying to push a piston into a hole that it's become too big for (or the hole is now to small for).
I think you're onto something with your fuel pump though, from what I've seen. I'd be happy to test the pump, both on a stand and in action on the truck.
I think your rod issue is clearance related. Galling in the cylinder is both pulling the rods apart and bending them trying to push a piston into a hole that it's become too big for (or the hole is now to small for).
I think you're onto something with your fuel pump though, from what I've seen. I'd be happy to test the pump, both on a stand and in action on the truck.
uniquediesel
1/4 mi. Fan
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Buddy,
I'll get back to this C/R and injector pop pressure thing. My machinist and I gotta bump heads on this one, not sure If I follow your math there.
Basically the 17.1 engine at my altitude (3800 ft) at full boost (35 psi) is around 58:1. To get PSI for that amount of compression you multiply the C/R by atmosphere at sea level, 14.7. So my dynamic compresion ratio (not accounting for valve train and swept compression due to bore size 4.055 in.) is 852.6 PSI.
Maybe I'm missing something there, not getting a complete charge every cycle?
852.6 PSI is a lot less than 2100 PSI in my book.
Now, after fuel is in the hole and it goes boom, dunno on that number... I Just hold the wheel straight and compensate for the back end wanting to go a different direction than straight for a little bit.
I'll get back to this C/R and injector pop pressure thing. My machinist and I gotta bump heads on this one, not sure If I follow your math there.
Basically the 17.1 engine at my altitude (3800 ft) at full boost (35 psi) is around 58:1. To get PSI for that amount of compression you multiply the C/R by atmosphere at sea level, 14.7. So my dynamic compresion ratio (not accounting for valve train and swept compression due to bore size 4.055 in.) is 852.6 PSI.
Maybe I'm missing something there, not getting a complete charge every cycle?
852.6 PSI is a lot less than 2100 PSI in my book.
Now, after fuel is in the hole and it goes boom, dunno on that number... I Just hold the wheel straight and compensate for the back end wanting to go a different direction than straight for a little bit.
I called them today and asked about the towing cam kit..... told them I was all manual pump motor, the price was the same even tho they say you need the program to make it work, and they don't have dyno test to back up what they say.... if you don't have a computer to adjust, how do you charge the same price for the kit....if you don't need the computer program ?? the kid on the phone didn't know what to say... I think I will stay with a stock cam.... it works...
sshewins
Jesus Freak
I get the whole charging the same thing, but needing the program on a mechanical engine? Sorry, but I just had to chuckle on that one.
buddy
Active Member
You have to use some chemistry equations to determine the pressure of air when compressed to a small size. Its not just a multiplication like you did, you have to take heat into account, by using the specific heat ratio of air as an exponent to the CR. So.....
Ptdc=Pbdc x CR^1.4 where 1.4 is the specific heat ratio of air -> Ptdc = (35psi+14.7psi) x 17^1.4 = 2624psi
With blowby and some absorbing of heat to the block the pressure is slightly lower, but at 3500rpm its going to be pretty close to that.
Other useful stuff, like to determine CR and the temperature at specific volumes and pressures.
Ideal Gas Law of PV=nRT
TDC volume=DISPLACEMENTcyl/(CR-1)
CR = (displacement + combustion chamber) / combustion chamber is the value CR:1 where combustion chamber volume is the entire volume above the piston at TDC, the "squish space"
plus the precup.
A lot of people get CR calculations wrong, as they think that the combustion chamber volume multiplied by the CR = displacement, or conversely displacement divided by CR = combustion chamber volume. But thats not the case, because its a ratio of volume left to the volume of everything, not just displacement.
Ptdc=Pbdc x CR^1.4 where 1.4 is the specific heat ratio of air -> Ptdc = (35psi+14.7psi) x 17^1.4 = 2624psi
With blowby and some absorbing of heat to the block the pressure is slightly lower, but at 3500rpm its going to be pretty close to that.
Other useful stuff, like to determine CR and the temperature at specific volumes and pressures.
Ideal Gas Law of PV=nRT
TDC volume=DISPLACEMENTcyl/(CR-1)
CR = (displacement + combustion chamber) / combustion chamber is the value CR:1 where combustion chamber volume is the entire volume above the piston at TDC, the "squish space"
plus the precup.
A lot of people get CR calculations wrong, as they think that the combustion chamber volume multiplied by the CR = displacement, or conversely displacement divided by CR = combustion chamber volume. But thats not the case, because its a ratio of volume left to the volume of everything, not just displacement.
I'm trying to come up with ideas for a higher powerband,like 3000-5000 rpms. Could I retard the cam ? Like it was there was still good power at 3800,but at 4200,it just stopped. I never checked turbo drive psi,this could hold it back some at high rpms. I always assumed it's the injector pump,even with no governor.