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What Is The Most Boost These Engines Can Handle??

DZZ71

DZZ71

"Living The 6.5 Dream"
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Alberta,Canada
Whats the max amount of boost i can push into my truck? I have the ARP head studs is that helps at all.
 
bending rods, floating valves, breaking push rods and lifters. over boost on a 65 is never good. i ran 18psi of boost when i had mine it was stock head bolts. i held up fine. 20 psi is when you start breakin stuff
 
From a lot of reading and some heat testing on diesels (then some arm chair quarterbacking for consideration).

Loaded question above 15-16 psi is usually fatal after some time depending on the mix of circumstances.

I think one of the keys to running higher boost in the 15-20 psi range is to understand the interaction of high cylinder/combustion area heat and quicker ignition of fuel. Too advanced timing and ignition increased peak cylinder pressure and stresses the bottom end with a lot of force at near TDC. So you have to keep all other temp indicators in good check. Make sure the coolant doesn't get too warm (above 210F better at 195F). And watch EGT and IAT too. Then it probably is a perfection of tuning and what RPM's you are running. And make sure its a complete system build and understanding off all interactions of changes/mods. Many reduce compression ratio to decrease combustion temps to reduce this peak cylinder pressure at near TDC. But Heath runs stock compression (from later years). So he is doing something else to insure its not getting too quick of pop at near TDC not sure if its higher RPM, water mist intercooling, or tuning.

Then its still not recommended for sustained events and engine longevity.

Sounds like you have pretty good list of mods already but make sure interactions are not developing. Just one example .... Is intake free flowing such that its not taking more turbo work to make boost before CAC to make measured boost high ( there is usually appreciable piping loss and pressure drop due to temp drop across CAC especially with typical 6.5 hanging CAC's).
 
Yep, the Flatland Fireball... literally. :D

There's a fine balance - adding boost lowers EGR and lets you run more HP - but if the EGR or Boost or block temp gets too high, you start losing integrity... if you're lucky, head gaskets are the first indicator that you are pushing too much, but the bottoms on these engines are really the weak spot, not the tops.

A balance issue in the rotating mass, a hairline crack in a web, any problem at all with your balancer and that extra boost/power/torque will haunt you, just like it did Chris.
 
Someone on here was running an HX35 to 24psi or so commonly for a long period of time.

I think the timing advance that GM forgot to add at high RPM and high fuel rates limits the power and causes high EGTs on stock programs and aftermarket programs that dont modify the timing curve.

I can run WOT for a while and EGTs run about 900F preturbo and ECTs stay below 195F. Thats with 15-20psi boost

Although I think I need a new balancer before mine ends up like Chris'
 
chrisk1500 said:
Did you already forget what the original one looked like when you pulled it? LOL!

That was with 18 psi.....
Click to expand...

Well yeah i remeber how mangled your 929 was, but there could have been several other contributing factors that aided in the complete destruction of your engine. Apon tear down i noticed a few of your bearings were completly gone. That right there could have cauesed a crack or weak point. Maybe the previous owner overheated the engine and it already had premature cracks. Who knows if the overboosting cauesed it to blow up. I was just wondering what a healthy 6.5 could handle...... im gonna pull the engine in a few weeks and do head gaskets and bearing so i wanna know my limit after that.
 
drive pressure also has a lot to do with engine destruction. the mosre boost you make the more drive pressure there is. good ratio of boost to drive pressure is 1:1. but with some turbos when they start producing more boost the drive pressure goes up more than boost. that is when damage starts happening. im sure the gm x series of trubos when making big boost have higher boost numbers than say a hx35 or another turbo with a bigger turbine
 
Woody35 said:
drive pressure also has a lot to do with engine destruction. the mosre boost you make the more drive pressure there is. good ratio of boost to drive pressure is 1:1. but with some turbos when they start producing more boost the drive pressure goes up more than boost. that is when damage starts happening. im sure the gm x series of trubos when making big boost have higher boost numbers than say a hx35 or another turbo with a bigger turbine
Click to expand...

What about load? 15psi pulling 10k vs 15psi empty?
 
The only reason it would be more deteremental when towing is because of ECTs. You may not be going as fast to unload more heat and you may be sustaining it longer to cause EGTs and IATs to affect ECTs. Keep ECT low and should be OK.
 
bogging puts high stresses on the crankshaft. thats why they say never to bog a 6.2 because you will snap the crank in half. high rpm i think would put more stress on the maincaps and the block just because the pistons when coming down are trying to push the crankshaft the opposite way leaving the maincaps holding it in place. thats why people get girdles and splayed mains to add more strength for holding it in
 
What do you consider bogging? I like staying at low RPM in OD going uphill at 2000rpm with 10lbs-15psi of boost. RPMs stay down, maybe creep up but boost goes up. It runs real smooth that way compared to in 3rd gear at 2700rpm or something like that.
 
1500 or so In OD climbing a hill I feel like its bogging. I'd rather downshift and run around 2k. 2k always feels perfect to me. From 2k-2500 I think I hear what people refer to as Drone? It quiets out above 2500, runs really smooth and quiet around 2700, but then I shift into OD and it lands a little above 2k... perfect.

I'm wondering once I toss the fluidampr if the engine drone sound will change at all. Sometimes it worries me thinking its harmonics making the drone noise.
 
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