DZZ71
"Living The 6.5 Dream"
How much boost do you plan on running 6.2turbo? I pushed out my head gasket after running the hx for a summer.
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lowering compression: shaving pistons or shortening stroke, or thicker gaskets...
- Thread starter turbonator
- Start date
buddy
Active Member
This spreadsheet can make a pretty good argument for lowering compression ratio. If you open/download it you can modify the input parameters to anything you want and it will calculate the temperature and pressure at TDC just from compression alone before combustion. I'm not saying I would go down below 18:1, and me personally would like to maintain 20:1. Caveat, I made this spreadsheet and equations, so if you wanted to check the work just calculate it once yourself and compare the results.
View attachment TDC Air Temp.xls
View attachment TDC Air Temp.xls
Last edited:
turbonator
Member
it is running 6.20 ratio, on the highway it does 60mph at 2400-2800 rpm, and it pulls strong without really pushing it hard... the best we have seen is a 6 percent grade, 14000lbs on the trailer and the weight of the truck(17000lbs) i started the hill at a standstill and at the top i was doing 30-35mph, in second-third, and boosting 18-20 psi with 900F egt temp, our home-made water meth system starts spraying at 8 psi boost, the hill is about 2 km long.... the only problem with it is the sm-465 has large gaps between the gears, so it is always between 2-3-4 in those situations... we are talking this summer to try a 4l80e in there, and if it blows a allison at-545....
Matt Bachand
Depends on the 6.5
You may be the PERFECT candidate for an ATT. The 6.5 Really likes to pull around 2700-3000.
turbonator
Member
we use the holset vgt, turbo master, it is great in all rpm ranges, 5-7 psi when cruising a 45-50 mph, just punch it and she spikes pretty quick to 18-20 psi and low egts...
turbonator
Member
doesnt heath run high compression and high boost with that twin turbo truck?
buddy
Active Member
Heath may run high compression, how much boost I do not know, but you must realize its built for short bursts of power and speed where some cooling and air temperatures can be easier on the engine. That truck will never likely see a tow hitch or drag race.
turbonator
Member
we believe that it would, the ideal would be to take all the glows out and put in 8 pyro gauges... a lot of money, but a cool experiment....
also we would like to thank buddy for the excellent spread sheet, this guy is a walking file of great tech...
DZZ71
"Living The 6.5 Dream"
8 EGT guages would be pretty damn neat just to see the temp differences through RPM ranges. Would half to get somone to drive it i would crash looken at that many guages haha
turbonator
Member
mount all the gauges on the pass side, and grab a co-pilot to watch.... i would have cross-eyes for sure from that...LOL
buddy
Active Member
No problem, youre welcome. I originally just meant for it to show hot IATs affect EGTs, but it seemed more useful than that and how CR and boost affect EGTs, and what combination might be killing head gaskets.
Matt Bachand
Depends on the 6.5
Matt Bachand
Depends on the 6.5
Sure would be cool. Data Logging gauges would be ideal for this!
buddy
Active Member
You would need gauges and senders good to 3000F, which is the real difficult part, and most people dont realize combustion is that hot. There is not a lot of information out there like this because its difficult. I have read some studies performed about combustion temperatures and mainly backed by some university.
buddy
Active Member
I know there have been disastrous setbacks on the turbonator front.
I was thinking about making a sheet to try to calculate how to dish the piston, but it was starting to make my head hurt. I settled on this attached file for calculating CR after adding thicker gaskets or shaving pistons or both. You can insert your starting CR whether stock or using thicker head gasket and want to know how much shaving the piston would decrease it. Spent some time incorporating the swirl bowls and flame guide into the shaved piston equations, since you would not be removing volume from that area when shaving. That complexity doesnt apply to thicker gaskets, and why shaving doesnt drop CR as quickly. I dont recommend straight piston shaving, because it reduces ring height and reduces the swirl bowls, so I believe dishing the center or extending each swirl bowl out would be better.
I was thinking about making a sheet to try to calculate how to dish the piston, but it was starting to make my head hurt. I settled on this attached file for calculating CR after adding thicker gaskets or shaving pistons or both. You can insert your starting CR whether stock or using thicker head gasket and want to know how much shaving the piston would decrease it. Spent some time incorporating the swirl bowls and flame guide into the shaved piston equations, since you would not be removing volume from that area when shaving. That complexity doesnt apply to thicker gaskets, and why shaving doesnt drop CR as quickly. I dont recommend straight piston shaving, because it reduces ring height and reduces the swirl bowls, so I believe dishing the center or extending each swirl bowl out would be better.
Turbine Doc
Just Another Diesel Guy
20+ psi for boost & CR was going to be 22:1 at a minimum possibly higher, and 3 miles at 100+ mph seems like pretty big work out for a truck a LONG drag race IMO.
According to Bill drop off the Bonneville speed rated tires and truck will be street legal and able to tow if need be will be like any other 6.5 one of his goals was to keep the LSR at stock weight and other than the Bonneville required safety mods make it a near as stock 6.5 as you can buy, major mod departing from this aside from the twin turbos, truck has been upgraded to a OBD-II PCM as OBD-I PCM wasn't up to requirements for what he needed for Bonneville, something about way things were monitored faster and more tweaking possible with the OBD-II over the OBD-I.
FWIW Mile 2 @ Bonneville is one that gets captured for speed mile 1 & 3 are for run up to top & coming down from top and Bonneville can be hot or cold depending on weather or which run of the year you make the run.
Turbine Doc
Just Another Diesel Guy
As Buddy says, no low cost sensor option out there for reading actual combustion temps. So we have to read "cooler exhaust gasses" with a thermocouple setup similar to the pyro we use for turbo EGTs here, combustion temps for most part done with math models by guys with some very sharp pencils and some number crunching puters, I've seen a lot of systems in the field over the years and systems/sensor are getting better but ain't there yet.
To read temps that high in turbine world we read the color of the flame and process that into a puter this says temp is X, or calculate the temp from comparison to a known value for fuel/air mix of a given fuel, gas chromatograph or calorimeters also part of that system depending on how stable fuel properties are determines which one needs faster/smarter gizmos like this http://www.cosa-instrument.com/Products/PDF_Files/COSA9610.pdf accurate combustion temps an absolute must when we are "mapping" turbines using DLN Dry Low Nox technology to control emissions
buddy
Active Member
Anyone can run 100+ mph over 3 miles, so that isnt a work out 
Even for an old tired engine. The problem would be consuming the same fuel, generating the same heat, but only going 35mph up a long hill for 30 minutes, where now you dont have beneift of air cooling, engine bay air exchange, and ram air effects.
Heath has EGTs over 1400F, uses water to fuel at nearly 2:1 ratio, and has no cooling fan and the low flow water pump. Those are some things that can be remedied, but for a towing truck I personally would not increase compression ratio. The higher compression ratio will make more heat, which isnt necessarily needed, which can make EGTs go up and engine temps. While also putting a lot more force up on the head.
IMO, with the stock valve timing, a 20:1 static compression ratio is probably a good place to be, which with diamond precups and a +.01" gasket should be about that. Now, my camshaft regrind yet to be used, has the intake valve closing a bit later, so the dynamic CR will lower a bit with it, and would be good for me to maintain a higher static CR. According to diesel power magazine Heath uses a modified camshaft in his racer, which could have extended air intake valve closure and exhaust valve opening earlier. So if he is using a modified cam his Dynamic CR could be lower.
I need to rethink some of the compression calculations for what the dynamic CR would be, based on valve timing, and some loss around the rings or valves and rpms. At 2000rpm the dynamic CR could be a few points lower than the static ratio.
Even for an old tired engine. The problem would be consuming the same fuel, generating the same heat, but only going 35mph up a long hill for 30 minutes, where now you dont have beneift of air cooling, engine bay air exchange, and ram air effects.Heath has EGTs over 1400F, uses water to fuel at nearly 2:1 ratio, and has no cooling fan and the low flow water pump. Those are some things that can be remedied, but for a towing truck I personally would not increase compression ratio. The higher compression ratio will make more heat, which isnt necessarily needed, which can make EGTs go up and engine temps. While also putting a lot more force up on the head.
IMO, with the stock valve timing, a 20:1 static compression ratio is probably a good place to be, which with diamond precups and a +.01" gasket should be about that. Now, my camshaft regrind yet to be used, has the intake valve closing a bit later, so the dynamic CR will lower a bit with it, and would be good for me to maintain a higher static CR. According to diesel power magazine Heath uses a modified camshaft in his racer, which could have extended air intake valve closure and exhaust valve opening earlier. So if he is using a modified cam his Dynamic CR could be lower.
I need to rethink some of the compression calculations for what the dynamic CR would be, based on valve timing, and some loss around the rings or valves and rpms. At 2000rpm the dynamic CR could be a few points lower than the static ratio.