BOOST- you ain't so big, you just tall, tha's all

[gmctd]

Boost is fairly simple to understand - it is related to pumped flow rate measured in CFM - volume - not very accurate, and Mass - weight, as related to air density, which is highly accurate.

If air was sold at a world-standard rate of $15.00 per cubic foot - $1.00 per pound of atmospheric pressure - the guy buying air in the Sahara would really be getting ripped off compared to the guy buying air in Antartica.
The Antartican's air-can would have a lot more air in it for his 15 bucks.

1cuft of summer air weighs less than 1cuft of winter air.
Hot air expands, becomes thinner, less dense - lighter.
Cold air contracts, becomes thicker, more dense - heavier.
Air pressurized greater than atmospheric pressure becomes more dense.

Flow rate measured in Cubic Feet per Minute CFM can be very inaccurate because of that physical law(s).

Don't believe it?
You can prove this with a simple, but dangerous, experiment -

First - tell the significant other there's a 50%off sale down at (fill in the local emporium, here).
This will remove most of the danger.

Take a clean, empty one-gallon metal can - paint thinner, gasoline, etc. - with a good sealable cap, outside and fill it with atmosphere.

Be very careful, here, to immediately cap the can off when filled, so as not to cause any ecological spills.
We don't want any of this stuff on the ground, or the carpet\flooring in your house, right?

Now, while 'the other' is gone shopping, place the filled can into the freezer for a period of time commensurate with accomplishing the experiment, and allowing for observation, summation, and removal of all evidence before the 'return'.

When you hear the audible 'carump!' from inside the freezer, the experiment is mature, and removal and observation of the can will reveal the somewhat mis-shapen, distorted can walls, caused by the cold-contracted air within.

Had you placed the can on a super-accurate digital scale at the start of the experiment, placing the can on the scale at this time would have shown the reduction in volume did not reduce the weight by volume.

Here's a pop quiz -
Which weighs more - a pound of lead or a pound of feathers?

Ok, looking over you guys shoulders, I see a number of you immediately circled 'pound of lead'.

So, since this is an 'all pass - none fail' curriculum, I'll restate the question -
Which has more volume?
And no, I'm not talking how much noise it makes when it hits the floor.

How much space or area - volume - does it occupy on your bench?

One (1.0) pound of lead is about the size of a golf ball.

I'm passing out boxes of four distinct sizes. Don't open them - just observe the relative dimensions, and the weight of each.
You can pass them around for weight-to-volume comparison.

I filled the boxes on an electronic digital scale, so the tare is accurate, to within a gnat's a(nkle)ss.

You guys with the two cubic foot boxes have exactly one pound of feathers inside.

You guys with the one cubic foot boxes have exactly one pound of feathers inside.

You guys with the six cubic inch boxes also have exactly one pound of feathers inside.

And whoever has the two cubic inch golf ball sized 1lb box - whatever you do, DO NOT UNTIE THE KNOT in that 60lb fishing line!

The 1lb of feathers was poured into 2cuft box till it was full.

Took a little pressure to get 1lb of feathers in the 1cuft box.

Required more pressure for the 1/2cuft box, much, much more for the 2cuin box.

Boost is taking that large original volume of air and putting it into smaller boxes, which can then be multiply stacked into that original volume.
We get the same volume, but much more weight.

And oxygen, folks, has definite weight per unit volume of air.

Which is why racers, aircraft, ships, locomotives, etc, use weight to calculate fuel consumption and air flow required to make power.

You won't hear an airline pilot pull up to the pump and ask for "a hunnerd gallons in that back tank, and check the pressure on that middle tire - it feels mushy".
Nope - he signs for a 15,000lb load of fuel, which he factors in with x-number of pounds of air, needed to make such-and-such thousands of pounds of thrust, all required to get his plane to Cleveland.

What's the relevence, you say?

Your ~400cuin 6.5L Diesel V8 engine is design-limited to 3500rpm - it pumps air at ~400 cubic feet per minute at 3000rpm, all day long.
(As an aside - a Buick 3.8L granny motor pumps nearly identical flow rate, at ~400cfm.)

That's 3000rpm, and that's ~400cfm, and that is ALL it will ever pump at 3000rpm.
You can add Slick-Stuff, STP, Water-Wetter, teflon oil, cetane-booster, owl snot, whatever, but it can only displace - pump - 400cfm at that rpm - written in stone.

Smokey, Grumpy, Cale, Richard - cain't help ya, folks.
Snake, Big Daddy, Connie - guys that get all dressed up to drive 1320 feet - no help, here.

Put a turbocharger on it - still only pumps ~400cfm.

You could install the turbocharger off the TITANIC - with a skajillion cfm capability - on this motor, and that huge turbocharger will only output 400cfm into this motor.

Fortunately for us, if we could power the turbine on that monster with the low-volume exhaust output of the 6.5L, that large cfm capability could be used to make power.

How?

If the flow rate output of the compressor - turbocharger - exceeds the flow rate thru-put of the target device - the 6.5L turbomotor - that excess flowrate input will stack up in the engine intake tract as pressure.

And pressure makes little boxes outta big boxes.
If one big box of air can burn one tablespoon of fuel, then that same box full of 10 little boxes of air can burn 10 tablespoons of Diesel fuel.

See - it's the weight we're concerned with, not the size.

400cfm at 1psi vs 400cfm at 10psi - more flowed weight at same flowed volume.

That's my story and I'm stickin' to it...............


Oh, yeah - the Buick granny motor? It's cranking 6000rpm to make ~400cfm.

Only three ways to make more power, folks -

Increase engine displacement at same rpm - bore and\or stroke

Increase rpm - 6.5L makes ~400cfm at 3000rpm, Buick 3.8L makes same at 6000rpm
6.5L would make ~800cfm at 6000rpm

Increase input pressure - Baro flows x-lbs\minute, 3x-baro flows 3x-lbs\min
Simplest. Easiest.

What's more - we already got it!

More safe Power to ya, folks.......

[ 01-16-2005, 02:17 PM: Message edited by: gmctd ]

[DA BIG ONE]

As in pressure ratio;
http://www.stealth316.com/2-turboguide.htm#c
In depth tech for gas turbos....

[markrinker]

So what is the effect of turning up the boost on a stock 6.5 past, say 12psi nominal? 15? 20+?

i.e. In mechanical terms, what happens at the 'point of no return'?

[Govt issue]

If you put the buick 3.8 and the 6.5 on the same platform.weight I would bet on the buick because it gains rpm quicker. But if that platform weighed over 3000lb I would bet on 6.5. Engine Acc. is all based on cam profile. engines that rev quick won't pull weight. engines that pull weight won't rev quick. usually. all in fun don't slauter me.

[grape]

you guys need to read turbomustangs turbo bible. All the math you'd ever want to know about how engines make power with air. Gasoline engines use 10lb per minute for every 100hp you plan to make diesels use 10lb per minute for every 80hp you plan to make. Figure out how much fuel you have hp for, then figure how much air you need and find a compressor map where the boost is what you want and the lb/min of flow is acceptable for your power output.

[gmctd]

Well, as a matter of personal opinion, Mark -

A high probability exists that there are not a whole lot of 6.5L trucks out there that have not been pre-stressed like ronniejoe's truck, BG (Before Gages).

Rolling the load till engine overheats, pulling over for a cool-down, then rolling the load till it overheats, pulling over again, etc, ad infinitum.

Those trucks that were purchased 'previously owned' are even more suspect, because the previous owner more than likely never discovered theDieselPage.com, before he 'dumped' the problem-child.

"Ayuh - sure, and it looks like a new one, because it don't never get far enough to get dirty!"

70kmi at high Boost levels does not equate to hi-Boost short demo runs with 18:1cr for a number of reasons.

JK's truck had a newly-built 18:1 engine
(JK TOTALLY 'stressed' his first 18:1 engine)
rj's truck had a medium-mileage pre-stressed 21.1:1 engine

JK's truck was a demo\showcase
rj's truck was worked hard for long periods\distances (rode hard, put up wet equivalent?) ;)

21:1cr pistons are flat-top, jam up against the cyinder head at TDC, do not allow for proper flame-front\pressure expansion across the piston at hi-Boost hi-combustion pressure hi-power levels.
Similar to exhaust flow restriction, but much more severe.
All that increased pressure is taken by that small Comet-groove under the idi pre-cup.


Don't forget - this design was originally for ~135 horsepower, and has been 'patched' up to 190, or so, with resultant problems.

18:1cr pistons, where crown is relieved to reduce compression ratio, have similar characteristics to pistons in direct-injection Diesels - rapid pressure expansion distributes forces over entire crown of piston.

rj indicated lowered EGT at all high Boost levels, and I'm still thinking on that, vis-a-vis the damage.
I don't think it is any coincidence hi-boost damage usually occurs in the bank adjacent the turbo - remove both valve covers, and the turbo-side nylon rocker-arm keepers are always much darker than those on the opposite side.
Heat is the enemy.

More oxygen in the cylnder results in total fuel combustion, where no remainder of the Diesel fuel, a light oil, is left to carry combustion heat out the exhaust path.
Diesels run best in a 'lean' condition - blowing any black smoke indicates incomplete combustion, with resultant climbing EGT's.

I personally consider high Boost levels - over 18psi - to be iffy, because of the un-equal staggering of head-bolt position around the cylinder, even with 18:1 pistons.

Should be some block\head shots over in the Member's Area - surf over and check out the stagger, particularly the spread across the idi cc\glow plug\injector area.
A rather unsettling picture of enhanced mechanical stress, imo, considering the pressures we're working with.

I've indicated my limits - I had occasion to fully check my 'pre-owned' engine last summer, while looking for a mysterious loud ticking\tapping noise.
Turned out to be a cracked TC plate, but the block is crack-free, the pistons are not 'browned' underside, got new rocker-arm keepers, hb and accessory pulley are pristine, DSG gearset is cool, new 5521 Inj Pump is set to -1.5deg TDC Offset, the Chausson charge-air cooler is working out, well.

In short (Ha!), I think I'm ahead of the game, for now, but I do make occasional brief 18-20psi excursions, when the engine is at cooler (180-190deg) op temps, and the weather is cool, and keeping close watch on the Tech-II.

I would always suggest a dropped-pan inspection on this engine, particularly if considering a Boost-enhancer, Chip\Re-Flash, and\or charge-air cooler.

Particularly-squared if purchasing a pre-owned truck.

That's my opinion(s), and I'm stickin' by it.......

[dieseldummy]

Mark, I think it is a general consensous that with a stock 6.5 the point of diminishing return is 10lbs non i/c or 12lbs i/c.
I've read through all the B.S. books, articles, and crap of that sort I can stand. In my book all it comes down to is what works in reality not theory. Boost increases displacement, fuel makes boost, displacement makes power, and it's as simple as that. Why do the cummins guys use twin turbos pushing upwards of 60lbs of boost? Simple answer is to keep egt in control. As a result of that all the available fuel is being burned which in turn makes the engine more efficient, therefore MORE POWER!! JD has it right when he makes the comparison of stuffing various boxes full of feathers. Our engines are a box, air is the feathers. The more feathers per cubic inch the bigger the bang there is when fuel is introduced... The key here is that the feathers are cool and dense after they have been through a charge cooling system. In an engine there will be flow restrictions therefore the more air trying to be flowed, the more pressure will build. The only practical way to flow 35lbs air/min at 10psi vs. 35lbs air/min at 20psi is more displacement to eat that air faster.

[gmctd]

You are correct, govtissue - the comparo was to demo an engine of half the displacement making the same flow-rate as it's larger counterpart, for the 'three ways to increase power' concept.

We have some racers-builders-tuners here, but a larger share of the members are owner-drivers, not very savvy in the infernal combustion engine dept.

Hopefully, I play to them. smile.gif

[rjschoolcraft]

dieseldummy,

If you ever run at higher boost levels, you won't go back...I guarantee it. I know you think I'm an idiot (you basically said so once), and that's all right. I've been called worse.

This thing ran good! The lesson to be learned here is this... If these engines have ever been hot or experienced high EGT, they're gonna break some time. Also, the blocks from 97 through late 2001 cannot handle higher power output for very long (acutally, some crack at stock power levels). Mine went nearly 70,000 miles at higher output being worked very hard. It went 159,000 miles total, worked hard every step of the way. That 90,000 miles in stock form is what hurt the pistons.

There is no doubt that the higher boost increases the stress on the pistons... Cylinder pressures are up and that's where the power comes from. There is also no doubt that aluminum dramatically loses mechanical properties (i.e. strength) above a certain temperature threshold. I had hoped that the oil spray jets in this engine had done enough to keep the actual metal temperature of the pistons cooler than the EGT readings (probably did, but not enough) so that I wouldn't get into trouble.

Furthermore, there is no doubt that higher boost pressures (especially with a charge air cooler) reduce EGT. The more boost I ran, the cooler the EGT. Even within the safe working temperature range for aluminum, strength decreases as temperature increases.

Now that I'm faced with a failed engine, I will do what is necessary to make it stronger. The 18:1 pistons will allow even more boost and I plan to do it. Initially, I will run the same turbo and boost levels (at JK's advice) just to avoid adding too many variables. Later, I will switch to a different turbo.

I've come to realize that boost increases the overall volumetric efficiency of these engines significantly. That's why you can make significantly more power by increasing boost without a corresponding increase in fuel rate. You're re-claiming some lost power and putting it to use.

As for the head bolt pattern... Yes, it's a little scary to observe. Why did they do such a thing?... But, I must say, there were no indications of any head gasket problems on my engine when it came apart. Head studs will probably help (that's what JK did with his).

In the end, as I reported in the other thread, three pistons were cracked... #4, #6 and #8. These three run the hottest and would have suffered the most from the high EGT excursions that this engine experienced. My EGT probe was located in the crossover pipe about three inches below the flange. It will now be moved to the passenger side exhaust manifold. I'll bet there is a fair difference in temperature between the two locations. That could have been a contributor to my problems as well.

When it's all said and done, draw your own conclusions and think what you want to think. As for me, I make my living looking at broken hardware to determine what went wrong. I take that information and design a better machine from it. Here we go...

[gmctd]

No argument, here, rj.

Are you considering tuff-triding the crank for the build-up?

GM did so on their forged steel cranks for HD hi-output (can't say 'racing' in corporate offices) service.

Increased piston-to-bore clearances on the turbo side?
Might not need it, tho, with the 18:1 pistons.

[rjschoolcraft]

I am considering nitriding. Nitirding increases the surface hardness by altering the chemistry of the material as nitride diffuses into the surface of the part while in an oven (there are other processes, but this is the most common). The only problem with nitriding is that it leaves a "white layer" at the surface that must be removed for maximum fatigue life of steel parts. This comes from my aircraft experience and was disputed by Caterpillar when I worked for them. However, after an extensive literature search and detailed report written by me, I was able to convince them to remove it from their seal journals.

The white layer is extremely brittle and provides initiations sites for cracks to form that can then propagate through fatigue into the base material. I havn't studied the automotive processes well enough yet to see if they remove the white layer. This can be done mechanically (machining) or chemically (electrochemical mahcining, ECM), but must be carefully controlled. ECM has been known to cause hydrogen embrittlement and stress corrosion problems if not controlled properly.

With that said, the increased surface hardness, or case hardness, from nitriding can increase the fatigue strength of the material by providing residual compressive stresses at the surface. This happens because of the chemistry change which increases the volume of the affected material at the surface through a change in the crystalline structure. It's much harder for a crack to form or propagate in a compressive residual stress field than in a zero stress or residual tension field. Residual tension is a bad thing!

I must research this further before deciding.

[dieseldummy]

RJ, I don't think your an idiot, quite the opposite infact. I am personally a fan of high boost numbers under most situations. When my engine quite me I went with 18:1 pistons and a better turbo. It ran pretty good, right up until a valve came loose and put a hamper on the fun. Currently I am back at 21:1 compression and am running my DB4911 pump maxed out producing 24+ lbs of boost on a holset turbo effeciently. It runs as good and as cool as the 18:1 motor did with a stock turbo. Egt's never go over 1250, I wish I had more fueling capabilities so I could do more, but at the moment it just insn't feasable... My previous reply was directed to those who think that everything that is said on paper is true, I personally have found that some of it is, but a lot of it isn't... I never have been good at using the smilies and such on these forums, maybe that would make things I say seem less harsh. ;)
Justin

[rjschoolcraft]

Cool.

Why did you go back to stock compression?

[arrowheadracing]

Not being a turbo guy till now. I can only say what I ve experienced over many years of racing and general use.

1. Everything has a breaking point. You ll find it when you ve gone too far.

2. Everything runs the best, just before it blows up.

3. Your 1995, my 1995 and his 1995 all being made in plant A from 8:00am to 8:15 am on the same day, by the same guy using the same parts does not mean they are the same.

4. You live here, I live there and he lives across the pond. Same as # 4 idea. Things are not the same temperature, elevation levels and what not. I am suprised no one has thought, or mentioned elevation as a factor. Any takers on that one ?

5. I ve run 9.90s on a stock pontiac short block, an aquataince has run 6.90s with a stock block and crank, close to 200 mph. With twin turbos and nitrous solenoids just to spool the turbos. I ve run a 12 second street car and with a stock short block and broke 4 rods, the crank in 3 places and lunched a piston so hard into the head it cracked a hole in it. Its all in process on how it was built and used.

6. Heat = power. If you are making power , you are making energy. There is a limit to what materials can handle and I dont care how much money you spend, it doesnt change the laws of physics. See point 1 again.

I admire those willing to spend the extra money to modify thier vehicles. But dollar for dollar , lb for lb, your vehicle will last longer the first time, then any rebuild or performance modification you can do. I ll be hit with a bunch of people that will disagree, but the ujoints in my 1 ton truck lasted 330,000 miles , I replaced them with the best aftermarket ujoint I could find, it last another 60,000 miles. The reason being everything is brand new. In these cases the block ( engine ) has seen 10 years of heat cycles and service. It has been conditioned and abused. You can bore and install new componets, but you still have a seasoned block, where as the new block has not seen those heat cycles. Sometimes thats good, sometimes thats bad. And I ll also add a small note that if your going to spend the money the first time, do it right. Even though you may have bought a new cap or crank or rods, have them checked for cracks. You will be suprised ( hopefully not ) at how many new items will have cracks.

Last, I see alot of apples to oranges comparisons. Lower compression vs high compression, low boost vs high boost. All I can say is what works for you, works for you and might work for someone else also. Great. But it might not either. Thats the beauty of a forum, we can all share our experience and learn from each other.

Good luck with your engine rebuild Ronniejoe. I ll be curious to see how you like your new setup.

Todd

[dieseldummy]

I went back to stock because I was on a pretty tight time table and the last parts I ordered from the boys in Georgia took way to long to get here...

[rjschoolcraft]

I've run down the drag strip a time or two myself. I've also worked around enough manufacturing facilities to understand variability in every day production. I also know that as a design engineer, you try to account for that in the tolerances that you specify. I also know that no matter what tolerances you specify, some guy on the manufacturing floor is gonna blow it and expect you to accept it to meet production for the month.

Elevation is a factor. 24 psi at 8000 feet MSL is not the same as 24 psi at mean sea level. If you search on this forum, you'll see that I've discussed this many times.

With that said, one truck running great for 150,000 miles does not prove anything statistically...and one truck blowing up at 10,000 miles doesn't prove anything statistically either. What doesn't change is theory and the physics behind why these things do what they do.

As for your argument about rebuilds... The statistics in the matter argue both ways. The results depend on the level of effort put into whatever rebuild is done. Looking specifically at rolling element bearings for aircraft engine use, a bearing that has been used for X number of hours, removed, inspected and re-installed has a much better reliability statistically than a brand new one that has never been used. This is because no matter how good the manufacturer is, some issues in production will arise that cause infant failures (short life span). These are factored into the reliability data for new bearings. With the used bearing, the infant mortality issues are non-existant...it already lived beyond those failure modes...so it's reliability is much better.

Your U-joint issue was probably due to a disturbance in the balance of the drive shaft or some unseen assembly problem...or even a quality problem at the U-joint manufacturer.

There are many variables, but science is still science and statistics are still statistics. Properly understood and applied, these disciplines can greatly enhance our ability to push machines.

[gmctd]

Yep - and it must be remembered: this is not a high-performance engine, it was not designed to be a hp engine, it will never be a hp engine, and any sensibly coordinated modifications will only improve, not guarantee, it's chances of surviveability at slightly increased power levels.

Keep that in mind, and you won't be disappointed.

If you're wanting Real Power, surf over to the Banks Diesel website, and read about a little 360cuin six cylinder.
Or, here, there, and everywhere about the Isuzu 400cuin V8.

Choice depends on the audio experience you're after.

Me, I like the sound of purring 6-cylinder Diesel, and that siren song of it's turbo as that 70,000lb loaded 18-wheeler accelerates past, in the fast lane..........

[rjschoolcraft]

Neither was the small block Chevy... :cool:

[gmctd]

How about 2.02" valves, d-port exhausts, forged 11:1 pistons, balanced rods (blue?), angled plugs, tuff-trided steel cranks, premium CLevite bearings, solid lifter camshafts, hi-output oil pumps, double roller timing sets, HD 8" harmonic balancers, steel flywheels, HP aluminum single-plane intakes from Weiand, open air filter housings, 600-780cfm Holley's, cowl-induction - all placed on the show-room floor by those good-ole boys in the back room, as standard optional equipment in Camaro, Malibu, Impala, Corvette, even placed in some Monza\Vega offerings by a friendly dealer in Long Island, and dealers elsewhere.

May have been before your time, rj - late 50's, 60's, early 70's - but available off the show-room floor, factory built, factory tuned.

And, then - there were all the optional goodies in the Factory Chevy Performance Manual and Catalog, if you were really serious (or rich).

Oh, yeah - brings tears to my eyes, thinking back.........

[arrowheadracing]

I think the bearing example falls hand in hand with the blown up 12 seond motor and 9.90 and 6.90 setups. My 9 second motor had over 200,000 miles on it before it saw active combat duty. The stress related in that setup is far past the stress in these diesel engines in terms of raw power and shock frequency. My point being that its exactly what you mean with pulling the used bearing. That block and crank setup where a good match. A very suprising match to handle that much power for a long time. I will say though that a top fuel motor gets rebuilt every pass it makes. In less then 4 seconds that motor produces what is probably equivalant to what our diesel engine would produce in its life time of stress. They use new everything, I know I am pretty much going to apples and oranges with that comparison. And airplanes are in a league of thier own ( just like corvette people ).

One point is that everything has to start out new at one time, be it the roller bearing in the plane or a piston is a diesel motor. That roller bearing in the plane will fail someday. Hopefully not while your up in the air. But let me ask this, if its in any way shape or form questionable , does it not get replaced with something new not used ? I would think it does.

For a quick note on the drive shaft, it was balanced and rebalanced and checked for any odd runout our out of round end surfaces. Its just my point that the new ujoint while being the best I could get, was not up to the manufacturing spec of a gm ujoint in my opinion. I ve replaced many ujoints and never get the same mileage as I do the originals. Most parts on cars now are designed to be thrown away when broken, not rebuilt, but replaced with a new part.

GMCTD I 100% agree with you. These engines are not high performance and any attempt to make them that way results in disaster. Whether you get it to tow mountain or take it to the track to drag race it. It will blow up one day, hopefully later then sooner. But longevity wise any modification you make to increase life and decrease the engines flaws from the factory are beneficial. What I think we need to understand is that one persons idea of improving via more boost or less compression or bigger cam or whatever, is not necessarily someone elses. My self I fall into the Ronniejoe category. I want to improve things to the point where I had a small hand in producing some brand new head castings for old pontiac motors. A 50-60 year old design, improved it and manufactured a new casting version. Which is doing quite well from what I see.

I anxiously await ronniejoes rebuild so I see how he does. I ll watch him spend his money , so I know how I might like to spend mine.

As for the comment on the SBC, your right it was never designed to be a performance motor. And isnt a performance motor. They are designed cheap to produce. Now a Hemi ( vintage ) on the other hand was produced to perform , hence the reason it didnt come with a warranty from Chrysler.

As I can see from our long winded notes we are all in it for the same reason. We love our 6.5 TD.

Todd

[Govt issue]

I had some good luck. My 429 bigblock fox body turned 7200rpm on the rev limiter in park, on NOS.
All stock parts except cam. Autozone rebuild kit. Get the picture. Turned off the key. Turned off the bottle. and finished the pass. we run 1/8 mile. 7.90 on motor that pass no problems. Oh yea we spray 175 hp. Sometimes things live sometimes they break.

[dieseldummy]

These engines may not have been designed for high performane, but we keep trying to find a way anyways... That in its self should be a testament of the determination of Americans... :cool:

[arrowheadracing]

As a note Americans are always big block power fanatics. Motorcycles in Europe seldom are bigger then 400cc's. While in America its all to common to see 1000-1300 cc bikes and others riding around with big block chevys transformed into two wheel tire spinners. Yes I believe Americans are never satisfied and always want to be better or faster. I would never survive if Europe.

Todd

[rjschoolcraft]

Originally posted by arrowheadracing:
I would never survive in Europe.

Todd Been there, done that (UK, France, Belgium, Germany, Netherlands). Couldn't stand it, glad to be home.

[More Power]

I think some of what Peninsular Diesel told me back in the late 90's about CR is worth repeating here. Kevin Emery, former Pen co-owner, told me that a stock CR 6.5 would run at max power on their engine dyno for about 2-1/2 hours before the pistons began grabbing the cylinder walls - leading to engine destruction. An 18:1 engine could run at more power for many tens of hours with no end in sight. Durability was the primary reason stated for lowering the compression ratio. A lower CR lowers combustion flame temperature - less heat driven into the piston crowns and cyl head.

I'd like to see the actual boost pressure / exhaust backpressure curves for the GM-x series of turbos. I know what the numbers are generally, but have not seen a chart. The gist - boost pressure generally tracks backpressure till somewhere in the 12-psi range, then backpressure climbs at a much faster rate. This tells me the efficiency range of this turbo series lies below 12 psi. I also know that owners like Ron and others see lower EGT's and generally see more power with higher pressures. I think there's more power to be had with more boost pressures, but I'd prefer a turbo with lower backpressures. Those owners I've talked to who are running a Peninsular high-flow non-wastegated turbo all like them for pulling - less so for local driving (turbo lag).

MP

[ 01-19-2005, 11:31 AM: Message edited by: More Power ]

[DA BIG ONE]

Originally posted by More Power:
I think some of what Peninsualr Diesel told me back in the late 90's about CR is worth repeating here. Kevin Emery, former Pen co-owner, told me that a stock CR 6.5 would run at max power on their engine dyno for about 2-1/2 hours before the pistons began grabbing the cylinder walls - leading to engine destruction. An 18:1 engine could run at more power for many tens of hours with no end in sight. Durability was the primary reason stated for lowering the compression ratio. A lower CR lowers combustion flame temperature - less heat driven into the piston crowns and cyl head.

I'd like to see the actual boost pressure / exhaust backpressure curves for the GM-x series of turbos. I know what the numbers are generally, but have not seen a chart. The gist - boost pressure generally tracks backpressure till somewhere in the 12-psi range, then backpressure climbs at a much faster rate. This tells me the efficiency range of this turbo series lies below 12 psi. I also know that owners like Ron and others see lower EGT's and generally see more power with higher pressures. I think there's more power to be had with more boost pressures, but I'd prefer a turbo with lower backpressures. Those owners I've talked to who are running a Peninsular high-flow non-wastegated turbo all like them for pulling - less so for local driving (turbo lag).

MP After spending some time on the phone this morning w/ Bill Heath, and reading your input I better understand "why not" too much boost, or a turbo that pumps more cfm at lower pressures on these motors.

[rjschoolcraft]

Originally posted by DA BIG ONE:
After spending some time on the phone this morning w/ Bill Heath, and reading your input I better understand "why not" too much boost, or a turbo that pumps more cfm at lower pressures on these motors. Read MP's post again...

The stock configuration could run at max power (190-200 hp at the flywheel) for only 2.5 hours... This makes perfect sense, because the EGT will get so high, the piston will swell. At 5-7 psi (stock boost levels), the EGT can get out of control. The 18:1 engine could run at more power (read higher boost pressures and fuel to get more power) for the foreseeable future.

At the boost pressures I was running, I was seeing the lowest EGT readings I've ever seen with this truck. That is goodness.

On edit:

In fact, I found this to be true first hand. The first engine in this truck failed at 65,000 miles from a galled cylinder wall on #8 which lead to a burned hole down the side of the piston through the rings. This followed about three hours of flat-out towing across North Dakota trying to maintain 60 mph. Truck was completely stock down to the air filter and I had no gages. Can't tell me that too much boost caused that problem!

[Spindrift]

RJ,

Did you say once that you believe the 6.5 is able to sustain EGTs at levels above the 1200* mark?

[dieseldummy]

I'm not RJ, but I beleive that 6.5's can run at 1250 degrees pre turbo all day long. I have done it for hours on end...

[rjschoolcraft]

Originally posted by Spindrift:
RJ,

Did you say once that you believe the 6.5 is able to sustain EGTs at levels above the 1200* mark? Yes, I did...and may have been wrong. What I know is this: I drove thousands of miles at between 1300 and 1350F steady state before making any modifications. It is my belief that with oil spray cooled pistons, this is probably OK. What I'm sure is not OK are the times that I saw the EGT gage peg above 1500F...

If you search back, you will see that I nearly always stated that the consensus on the board was to stay below 1200F, but that I had run successfully at up to 1350F steady state. It survived for 159,000 miles in 4 1/2 years. That's over 35,000 miles per year on average.

[Spindrift]

2 questions, then:

Will your recent experience cause you to revise your driving habits in any way? Secondly, would you consider opening up the two rear water jackets that are blocked off in my/our head(s) as an enhancement to the new engine's cooling system?

[rjschoolcraft]

I won't be changing my driving habits, because I finally got the truck into a configuration that will do what I want to under 1200F most of the time. With what I'm planning now, it will be even better.

I've thought about the mod you mentioned at the back of the heads. I've heard positives and negatives, so I will need to research more before I try that. I think with the cooling system improvements, it might not be necessary. However, if it looks like it will improve cooling in the back of the engine, then probably will.

[ 01-22-2005, 09:30 AM: Message edited by: ronniejoe ]

[DA BIG ONE]

Location of probe pre, and post turbo is critical, because a few inches one way or the other can give egt readings that vary as much as 200deg/f +or-.

A little off subject, but, did someone say they retro fitted a direct injected cummins into their GM? This does seem like a better choice for reliable mods....

[moondoggie]

Good Day!

Spindrift asked ronniejoe: [i]

[rjschoolcraft]

:D

[Billman]

JD - I'm surprised. I've been told you're a GM Guru/Encyclopedia.

Chevrolet LT1 - Blue rods? How about Pink.

Friendly dealer on Long Island - Baldwin/Motion. The Good Ol' Days... So they tell me. I was born a little too late.

The building is still there. Now they sell 20" wheels and Garbage Can Mufflers I think...

[norm]

One thing that brings question to my mind in all this business is the fact that these motors (6.5) are/have been used in military applications in great numbers. Some guys I know who have used them in service (who are not really "car guys" or 6.5 heads) talk about how "powerful" those humvees are, without much complaining. Maybe they've just seen the pretty side of things, not dealing with the mechanics much???
What stories about the 6.5 come out of the mil-spec world (relating to this thread of course)??

[gmctd]

Pink is for girls - I jus' didn't wanna say it.... ;)
Those Baldwin Chevys with the three white stripes down the middle were as easy to spot as Shelby's blue on white Fords.

Then there were the Yenko's.

The Chev small-blocks were the first mass-produced hi perf engines, where as the Chry Hemi's came in 287", ~347", and ~387" sizes in Dodge, DeSoto, and Chrysler sedans, before the 426" hemi's showed up in the Plymouth and Dodge two door sedans.
The 413\426 wedge opened to compete with the Chev 409 and 427 W dump-truck motors, Pontiac's 421 wedge, Ford's 406\427 wedge.
Chev responded with the 396\427 semi-hemi, Ford with the 427ohc hemi.

Oem dominance competition can be a stirring thing to be a part of, particularly as an end-user participant.

Btw - Royal Oak, Michigan ring any Pontiac bells?

How about Dickinson, Texas?

[patrick m.]

Originally posted by Billman:
JD - I'm surprised. I've been told you're a GM Guru/Encyclopedia.

Chevrolet LT1 - Blue rods? How about Pink.

Friendly dealer on Long Island - Baldwin/Motion. The Good Ol' Days... So they tell me. I was born a little too late.

The building is still there. Now they sell 20" wheels and Garbage Can Mufflers I think... those garbage can mufflers down here a called, "fart pipes". :D