Failure analysis leads to rebuild along with a cleanup.
02-26-2012, 11:40 AM
#43
Shoot for 11.5 11.8 is a good number
When I had all the timing in my car afr started out at 11.4 a creeped up to 11.9
Again alot of meth.
Ther are so many combos for some one to tell you exact timing numbers.
been tuning for awhile with no engine failers besides my own. (killed the thrust bearing)
We had a guys 11.1 compression 370 running 13psi of boost and got the timing all the way up to 21degs, did end up lifting the heads on 21 degs but there was no sign of det. when the heads where pulled off to regasket.
that car screamed on the 21deg, This 370 and all my cars are on 94 pump.
you need to get the car back together and dyno/track the car to find what the new combo will like far as timing, to many things play a role to set a number
When I had all the timing in my car afr started out at 11.4 a creeped up to 11.9
Again alot of meth.
Ther are so many combos for some one to tell you exact timing numbers.
been tuning for awhile with no engine failers besides my own. (killed the thrust bearing)
We had a guys 11.1 compression 370 running 13psi of boost and got the timing all the way up to 21degs, did end up lifting the heads on 21 degs but there was no sign of det. when the heads where pulled off to regasket.
that car screamed on the 21deg, This 370 and all my cars are on 94 pump.
you need to get the car back together and dyno/track the car to find what the new combo will like far as timing, to many things play a role to set a number
02-26-2012, 03:44 PM
#44
I like 11.8ish no richer than 11.5
I wasn't saying you in particular had too much timing. Running them too rich can still be bad tho.
The shape of the timing curve has a lot to do with it as well, not just any one number. I base it on the cam specs, head / intake efficiency, how fast it spools, shape of the HP curve etc.
Something that almost no one does but should be done is timing should be based around peak tq and cylinder pressure. Instead most people just highlight everything from say 3000 RPM and up and "lock it down" to a fixed number.
I wasn't saying you in particular had too much timing. Running them too rich can still be bad tho.
The shape of the timing curve has a lot to do with it as well, not just any one number. I base it on the cam specs, head / intake efficiency, how fast it spools, shape of the HP curve etc.
Something that almost no one does but should be done is timing should be based around peak tq and cylinder pressure. Instead most people just highlight everything from say 3000 RPM and up and "lock it down" to a fixed number.
02-26-2012, 04:29 PM
#45
The rest of the rods are still in the motor as I ran out of time, but they look fine. I'll pull them today.
I don't have enough tuning experience or FI experience to say one way or another. I was slowly leaning it out. Every time I drove the car I would data log, then make some fueling changes at 1-2% each time. I was commanding 11.2-11.4 but was running richer than that so I had some work to do in the VE table. I was trying to be cautious and error on the side of being too rich. So what afr do you beleive is safe? Again, I'm not disagreeing, I'm trying to learn.
You say cold weather low timing is your friend, how low? I was at 13 degrees of timing, I guess that was too much.
I don't have enough tuning experience or FI experience to say one way or another. I was slowly leaning it out. Every time I drove the car I would data log, then make some fueling changes at 1-2% each time. I was commanding 11.2-11.4 but was running richer than that so I had some work to do in the VE table. I was trying to be cautious and error on the side of being too rich. So what afr do you beleive is safe? Again, I'm not disagreeing, I'm trying to learn.
You say cold weather low timing is your friend, how low? I was at 13 degrees of timing, I guess that was too much.
I wasn't talking about you Alchemist, sorry for the bumble there.
I don't think you had too much timing in the motor. I'd consider 13 degrees ok, but a lot of other things play a part in how much and how little.
AFR and safe are hard to say by giving a blanket statement.
Let's say your car is back together. Forged pistons/rods/lower compression etc.
@14psi, I would try to get the AFR as close to 11.7-11.9 as I could. If it was on pump gas and no methanol I would try the timing around 10-12*. With Methanol I would keep the timing the same, but add boost, and then try and get the fueling back into that same 11.7-11.9 zone.
02-26-2012, 04:35 PM
#46
I think a review of how the combustion process works is in order.
Fuel is what creates heat in the cylinder. Timing just ingnites that fuel. CR and boost dictate cylinder pressure.
If your car leans out, lets say the fuel pump goes out and it goes to 17:1 afr there is hardly any fuel in the combustion chamber which means way less heat!!! Tell me how will that melt a piston down if there is no fuel for the combustion process to happen!!!
Adding fuel and making a motor overly rich melts pistons!!! The only other place on the AFR chart that get's comparably hot is right before and slightly after stoich.
If you put too much fuel(overly rich) in a motor, the initial spark of timing will not completely light off the fuel and what ends up happening is you get 2-3 different combustions where there should only be one because all that unburnt fuel is still exploding. After the initial spark if there is unburnt fuel the heat from the initial combustion will light that unburnt fuel off as it is going out of the exhaust valve or inside the combustion chamber.
Also Alchemist with that tune-up example I gave you I wouldn't run anything hotter than a -7 and maybe even a -8. Especially if you are planning on over 14psi. Where you were at before it blew I'd say a -8 especially with the CR you had.
Fuel is what creates heat in the cylinder. Timing just ingnites that fuel. CR and boost dictate cylinder pressure.
If your car leans out, lets say the fuel pump goes out and it goes to 17:1 afr there is hardly any fuel in the combustion chamber which means way less heat!!! Tell me how will that melt a piston down if there is no fuel for the combustion process to happen!!!
Adding fuel and making a motor overly rich melts pistons!!! The only other place on the AFR chart that get's comparably hot is right before and slightly after stoich.
If you put too much fuel(overly rich) in a motor, the initial spark of timing will not completely light off the fuel and what ends up happening is you get 2-3 different combustions where there should only be one because all that unburnt fuel is still exploding. After the initial spark if there is unburnt fuel the heat from the initial combustion will light that unburnt fuel off as it is going out of the exhaust valve or inside the combustion chamber.
Also Alchemist with that tune-up example I gave you I wouldn't run anything hotter than a -7 and maybe even a -8. Especially if you are planning on over 14psi. Where you were at before it blew I'd say a -8 especially with the CR you had.
02-26-2012, 05:00 PM
#47
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I wasn't talking about you Alchemist, sorry for the bumble there.
I don't think you had too much timing in the motor. I'd consider 13 degrees ok, but a lot of other things play a part in how much and how little.
AFR and safe are hard to say by giving a blanket statement.
Let's say your car is back together. Forged pistons/rods/lower compression etc.
@14psi, I would try to get the AFR as close to 11.7-11.9 as I could. If it was on pump gas and no methanol I would try the timing around 10-12*. With Methanol I would keep the timing the same, but add boost, and then try and get the fueling back into that same 11.7-11.9 zone.
I don't think you had too much timing in the motor. I'd consider 13 degrees ok, but a lot of other things play a part in how much and how little.
AFR and safe are hard to say by giving a blanket statement.
Let's say your car is back together. Forged pistons/rods/lower compression etc.
@14psi, I would try to get the AFR as close to 11.7-11.9 as I could. If it was on pump gas and no methanol I would try the timing around 10-12*. With Methanol I would keep the timing the same, but add boost, and then try and get the fueling back into that same 11.7-11.9 zone.
I thought most shoot for low 11s on meth..
02-26-2012, 07:40 PM
#48
Well, the first thing I'm going to do is pull out some fuel to get the tune back into the mid to high 11s when the motor goes back in. The next thing is to get it on a dyno to get a reference for the accuracy of my wideband.
I will also be running water/meoh to help keep the cylinder temps under control and to add some octane as well.
I think to summerize, I think I pushed too much power on a stock piston, got too much heat in the chamber from running too rich, possibly had some detonation, but honestly never had detected any in the past.
The combustion chamber on the heads is ~64cc which with a 0.050 head gasket it had put me at around 10.5:1 compression. It's not exactly 'ideal' for boost, but hell, look at how many of the ls2's and ls3's are that high and running plenty of boost trouble free.
I went with a diamond piston that has valve releifs that gives me a -3cc, which drops my compression to roughly 10.1:1, which is better. I don't plan on changing the pulley size, so I'm still going to see a max of 14psi at 6500rpm, but I will be running meoh/water to help add octane like I said.
So can a motor last with 10.1:1 compression, 14psi at max rpm, with a forged piston/rod combo?
I will also be running water/meoh to help keep the cylinder temps under control and to add some octane as well.
I think to summerize, I think I pushed too much power on a stock piston, got too much heat in the chamber from running too rich, possibly had some detonation, but honestly never had detected any in the past.
The combustion chamber on the heads is ~64cc which with a 0.050 head gasket it had put me at around 10.5:1 compression. It's not exactly 'ideal' for boost, but hell, look at how many of the ls2's and ls3's are that high and running plenty of boost trouble free.
I went with a diamond piston that has valve releifs that gives me a -3cc, which drops my compression to roughly 10.1:1, which is better. I don't plan on changing the pulley size, so I'm still going to see a max of 14psi at 6500rpm, but I will be running meoh/water to help add octane like I said.
So can a motor last with 10.1:1 compression, 14psi at max rpm, with a forged piston/rod combo?
02-26-2012, 08:39 PM
#50
FWIW, i know a local car is running a 14lbs on a stock shortblock with E85. the car put down over 600 on a jet. I think he has 317 heads though.. im sure you're right in a sense that you were making too much power for the bottom end but i think it was the combination of your CR, richer AFR, and pump gas only that did it in (which is what youve already decided)
There is no reason your forged bottom shouldnt handle you current setup and then some.
There is no reason your forged bottom shouldnt handle you current setup and then some.
02-26-2012, 09:23 PM
#51
Thats pretty vague, depends on the efficiency of the blower. One blower can move way more air (and create way more cylinder pressure) than another at the same PSI...
The cam and induction package also has a lot to do with cylinder pressure and the engine lasting as well.
That being said, controlling ANY chance of detonation is what you must do... Do that and it should last all day long at 14psi
02-27-2012, 06:11 PM
#52
Thats pretty vague, depends on the efficiency of the blower. One blower can move way more air (and create way more cylinder pressure) than another at the same PSI...
The cam and induction package also has a lot to do with cylinder pressure and the engine lasting as well.
That being said, controlling ANY chance of detonation is what you must do... Do that and it should last all day long at 14psi
The cam and induction package also has a lot to do with cylinder pressure and the engine lasting as well.
That being said, controlling ANY chance of detonation is what you must do... Do that and it should last all day long at 14psi
I'd honestly run a thicker head gasket than that and try and get it down in the 9.5-9.7 range and IMO that is still too high, I'd shoot for 9.1-9.3 and if it wasn't enough power go up on a pulley size.
To answer the guy that asked me if I would still shoot for 11.7-11.9 on meth, yes I would.
When I had my turbo car with methanol injection and pump gas only in the tank I would set the AFR as close to 11.5 as I could get it and had the timing around the 13-14* mark at WOT. This is on 15psi, although I didn't get on it hardly at all on the street.
At the track when I added race gas(either 110 or 116) I would lean it out to 11.7-11.9 to get a handle on things and see where the track was. I left the timing and boost alone and just leaned it out to what I stated.
When I wanted it on kill I'd lean it out to 11.9-12.1 and took the timing to 14* from 4200rpm up(two hundred rpm below what my converter flashed too so I still had timing to get on the brake, but had it pulled out once it got under load).
I wouldn't do what I did leaning it out wise without a couple sets of plugs and reading them at the track.
I honestly didn't read my plugs at all till I fouled them one day. I did some reading and bought an extra set along with a new set to replace the fouled ones and went to the track. After two passes I had my timing where I wanted it and my fuel ring was a faint faint tannish color at the bottom of the porcelein.
Last edited by Fbodyjunkie06; 02-27-2012 at 06:16 PM.
02-27-2012, 07:53 PM
#53
learning to read your plugs is idel. that tells you everything you need to know on whats going on in the combustion chamber.
if you dont tune your own car I would tell your tuner to keep the afr around 11.5 11.7 to give a lil window for any air density or fuel flow change
if you dont tune your own car I would tell your tuner to keep the afr around 11.5 11.7 to give a lil window for any air density or fuel flow change
03-13-2012, 12:47 PM
#54
UPDATE: Everything is at the machine shop getting assembled. I went with Diamond pistons with a -3cc valve releifs so the compression will stay around 10.1:1. Rods are scat rods with ARP 2000 rod bolts. I'm going with studs on the mains since it's now or never and only $130 more than new main bolts. It's one less thing to worry about down the road. I ended up finding a low mileage ls6 block that came out of a 2002 WS6 that never even had the heads off and still had the factory cam in it. Some people say it's better to use a seasoned block and true up the mains and deck than a fresh block, who knows.
I plan to run water/meoh to keep detonation away, as well as I plan to run Evans coolant.
I have no plans to change pulleys, so boost will stay right where it was before, but now I won't have to worry about popping a piston.
As for tuning, I was running rich to begin with, and plan to lean it out to low to mid 11s on the meoh/water.
I plan to run water/meoh to keep detonation away, as well as I plan to run Evans coolant.
I have no plans to change pulleys, so boost will stay right where it was before, but now I won't have to worry about popping a piston.
As for tuning, I was running rich to begin with, and plan to lean it out to low to mid 11s on the meoh/water.
Last edited by The Alchemist; 03-13-2012 at 12:53 PM.
03-13-2012, 05:35 PM
#56
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UPDATE: Everything is at the machine shop getting assembled. I went with Diamond pistons with a -3cc valve releifs so the compression will stay around 10.1:1. Rods are scat rods with ARP 2000 rod bolts. I'm going with studs on the mains since it's now or never and only $130 more than new main bolts. It's one less thing to worry about down the road. I ended up finding a low mileage ls6 block that came out of a 2002 WS6 that never even had the heads off and still had the factory cam in it. Some people say it's better to use a seasoned block and true up the mains and deck than a fresh block, who knows.
I plan to run water/meoh to keep detonation away, as well as I plan to run Evans coolant.
I have no plans to change pulleys, so boost will stay right where it was before, but now I won't have to worry about popping a piston.
As for tuning, I was running rich to begin with, and plan to lean it out to low to mid 11s on the meoh/water.
I plan to run water/meoh to keep detonation away, as well as I plan to run Evans coolant.
I have no plans to change pulleys, so boost will stay right where it was before, but now I won't have to worry about popping a piston.
As for tuning, I was running rich to begin with, and plan to lean it out to low to mid 11s on the meoh/water.
Everything sounds good except the Evans coolant. I gave her a try and it didn't work for me at all. In fact I overheated. If you want to use it you really need a higher volume water pump. If you still want to try it pm me I have enough
UnOpened Evans I can give you a deal on it.
Last edited by 35thsscamaro02; 03-13-2012 at 06:16 PM.
03-13-2012, 08:53 PM
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