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Performance Tuning for the Tahoe

With 140cc at like 2500rpm, 110cc over 3000rpm, and 40psi of boost with 21:1 CR, its not hard to realize the 5-bolt pattern on the head isnt going to hold up. A design limit.

With 40psi of boost at 21:1 CR the pressure at TDC would be about 3800psi before combustion.

The engine probably runs better limiting it to 30psi. The more boost you run, the more power the engine loses in having to compress that air before combustion and also having to create the backpressure. There is a 700psi compression difference between 40 and 30psi of boost. Plus you lift the heads off and bend the connecting rods. If you could push 140cc all the way to 4000rpm, then 30psi boost intercooled to 200F IAT would give you an 18:1 AFR, which is where you probably want to be. With 40psi of boost and 300F IAT with no intercooler you do get more air mass, but about 25:1 AFR at 110cc, and a good 19:1 AFR with 140cc. So 40psi is the right boost without an intercooler for the fueling you have in the mid range RPMs. But as it cuts out fuel flow you dont need as much boost and it is overly lean.

If you want to make the power at high RPMs then I dont think its bad to be less lean in the mid range RPM to get the right AFR up high. So essentially running 30psi without an intercooler gives you just lean of stoichiometry with about 15.5:1 AFR in the mid 2000rpm where you have 140cc. And 19-20:1 AFR above 3000rpm when you have 110cc. Basically was a good decission to wastegate it at 30psi. If able to keep the fueling above 110cc then an intercooler would be the best addition to increase the air mass flow.
 
WTF??? on another thread you said boost equals more airflow. Now you say limit the boost????????:???: I don't believe you know much about any engine once they get past stock hp. Or are you just confused?
 
littleboy said:
WTF??? on another thread you said boost equals more airflow. Now you say limit the boost????????:???: I don't believe you know much about any engine once they get past stock hp. Or are you just confused?
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I dont think you know how to read, so just stop commenting about my posts until you know what you are talking about. You guys never learn, its not volume you care about, its air mass, and how does that correlate to your fuel mass. Where the heck did I just mention caring about needing more air flow? I tried to explain how much air mass flow you need for the fueling you have. There is no sense in having more than that, its detrimental. Go read a book or something, just stop posting your nonsense crap.
 
I laughed....;) The turbo 6.2turbo runs is efficient up to around 50 psi. The only time boost hurts power is if you have excessive back pressure!!! I'm just gonna go back to working on some engines here instead of posting conflicting and misleading info! I can learn more by doing than i can by reading! ;) Experience.... :thumbsup:
 
Cumminsfever said:
Do the math. He got his pump cc'd, has marine injectors, and a 66/68/16 turbo, and can pull 4500rpm easily.
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The math doesn't add up, and now that I've seen claims of 140cc's, 110+cc's over 3k, I'm more skeptical. I'd just like a little paper and or video evidence. That's not unreasonable.
 
littleboy said:
Or you could come in here an go for a ride.
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If I was within a reasonable distance, sure.... However I'm not, and I find serious inconsistencies, and some of these claims to be completely outlandish.... So I'm raising the flag.

So either:

A) I need to learn something from him about the DB4's.

B) He's full of crap.

Not to mention the boost numbers are wild... almost twice as much as mine.
 
littleboy said:
I laughed....;) The turbo 6.2turbo runs is efficient up to around 50 psi. The only time boost hurts power is if you have excessive back pressure!!! I'm just gonna go back to working on some engines here instead of posting conflicting and misleading info! I can learn more by doing than i can by reading! ;) Experience.... :thumbsup:
Click to expand...

You'll never learn, have you ever tried to compress air to 4000psi? Do you think your engine likes it any better? Engine A compresses to 3000psi, Engine B compresses to 4000psi, which is happier and will use more energy? Now what did compressing the air 1000 more psi gain me? Thats the million dollar question. NOTHING!!!! But it cost you the energy and heat to do it. And why did it gain me nothing? Because I already had enough air for the fuel I injected. If you have more fuel, you might be able to use the extra air mass, but this is how you tune something, not just throw as much boost at it as you can. And even if you thought only backpressure was an issue, I dont care how efficient the turbo is youll have more backpressure at 40psi than at 30psi, so that is additional parasitic loss. And the backpressure values should be taken at a steady state boost, like under load, climbing a hill and pushing 20psi of boost constant, what is the steady state backpressure. There are about 10 different concepts here and you boil it down to more boost is more air and thats good.

Because you cant read and comprehend you have no idea what is conflicting, its just over your head. Which is fine, just stop posting about how confusing it is.
 
Chill ....
I think his pump maxed out at 160cc but I'm not exactly sure. We have a 29 plunger pump that spools an hx-55 that easily pegs a 30 psi gauge an it runs right with his truck.
 
And I bet he's bent more connecting rods than you too. Go back several pages and look up some of the stuff he's done. I really don't think he's pullin one over on you. Just sayin.
 
buddy said:
You'll never learn, have you ever tried to compress air to 4000psi? Do you think your engine likes it any better? Engine A compresses to 3000psi, Engine B compresses to 4000psi, which is happier and will use more energy? Now what did compressing the air 1000 more psi gain me? Thats the million dollar question. NOTHING!!!! But it cost you the energy and heat to do it. And why did it gain me nothing? Because I already had enough air for the fuel I injected. If you have more fuel, you might be able to use the extra air mass, but this is how you tune something, not just throw as much boost at it as you can. And even if you thought only backpressure was an issue, I dont care how efficient the turbo is youll have more backpressure at 40psi than at 30psi, so that is additional parasitic loss. And the backpressure values should be taken at a steady state boost, like under load, climbing a hill and pushing 20psi of boost constant, what is the steady state backpressure. There are about 10 different concepts here and you boil it down to more boost is more air and thats good.

Because you cant read and comprehend you have no idea what is conflicting, its just over your head. Which is fine, just stop posting about how confusing it is.
Click to expand...

Finally Buddy and I agree on something. He is completely correct. I read through this whole thread trying to validate 6.2's claims and the only thing I can think of, is that he is spinning that charger purely off of the air flow/back pressure of the engine at higher RPM. He doesn't have nearly enough fuel to support that amount of boost, and the amount of power that boost can support... therefore its pennies on the dollar difference in power gain, or possibly a power loss for the reasons buddy explained.

Boost does nothing without fuel. He does not have the fuel... and I am very well versed in what the DB4 is capable of, and as far as I can tell, he has not modified his nearly as much as I modified mine.
 
nmb2 said:
The math doesn't add up, and now that I've seen claims of 140cc's, 110+cc's over 3k, I'm more skeptical. I'd just like a little paper and or video evidence. That's not unreasonable.
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You could give him a little credit for bending a few sets of rods, O-ring his engine, ect... not sure why someone would lie about lifting their heads and bending their rods? Thats not exactly what I call bragging, having to rebuild your engine 3 times a year.
 
littleboy said:
Chill ....
I think his pump maxed out at 160cc but I'm not exactly sure. We have a 29 plunger pump that spools an hx-55 that easily pegs a 30 psi gauge an it runs right with his truck.
Click to expand...

If anything you just proved buddies claim. A .29 plunger DB2, running 30psi... runs right with a 160cc DB4 pushing 50-60psi. You realize what you just said right?

Stop posting empty claims. Post some kind of proof. ET and weight slips, dynojet, video of said boost gauge spooling from 0 to max, a flow bench data spec on a pump.....

sshewins said:
And I bet he's bent more connecting rods than you too. Go back several pages and look up some of the stuff he's done. I really don't think he's pullin one over on you. Just sayin.
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I'm sure he has bent more connecting rods than me. I have a much stronger engine than him... I don't worry about bending rods. I've been reading about the stuff he has done for months... including the angle iron main girdles.
 
Yeah, 6.2turbo is just randomly logging in, posting fictitious numbers, about a fictitious vehicle, that only exists in his sleep.
somehow, this fictitious vehicle randomly bends rods, and pukes it's guts on the road.
and... somehow, I rode in this fictitious vehicle. Musta been sleeping...
 
nmb2 said:
If anything you just proved buddies claim. A .29 plunger DB2, running 30psi... runs right with a 160cc DB4 pushing 50-60psi. You realize what you just said right?

Stop posting empty claims. Post some kind of proof. ET and weight slips, dynojet, video of said boost gauge spooling from 0 to max, a flow bench data spec on a pump.....
Click to expand...

Confused. Who has a db4 that you are comparing this to??
 
Cumminsfever said:
Yeah, 6.2turbo is just randomly logging in, posting fictitious numbers, about a fictitious vehicle, that only exists in his sleep.
somehow, this fictitious vehicle randomly bends rods, and pukes it's guts on the road.
and... somehow, I rode in this fictitious vehicle. Musta been sleeping...
Click to expand...

Really? I never said the vehicle was fictitious. I said his claims were outlandish. You seem stuck on the fact that he has bent rods.... its a 6.2, not a 6.9, 7.3 or 5.9.... its not a hard feat to accomplish I'm sure.

I'm more focused on the fact that his magical DB4 can do 160cc's at full tilt, with no mention of EDM work. I have a lot of work into the DB4's, and a lot of bench time, and everything I know, goes against what he claims. Differences are that I have dyno sheets, running videos, pump bench data logs, and about 1,000 pictures.
 
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