Compression Ratio on built motors

99Binder

99Binder

New member
Well basically I want to talk compression Ratios on hot diesel trucks, right now BWD and i are putting a motor togeather with RR rods, crower valve springs and push rods, WOP main girdle and fire rings, and a TN GTK76. Im just wondering what kind of compression ratios everyone is running on a hot daily drivable truck. a PSD is 17.5 IIRC and im thinking of dropping it to 16.5 thinking that this will be decent starting truck yet. After talking with a neighbor and a another member of this site i was told to keep as close to stock if im going to drive this truck quite abit. Another possibility the going to a heathy set of twins someday should that be taken into account as well? Thanks wyatt
 
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I would consider my truck to be hot. Mine at 14:1. stock is 17.1:1 I believe. The problem with a hot motor is that you use a can of starter fluid a week.
 
12 or 13 :1 is what we use in pulling tractors that make 2500+ hp with cyl pressures in the scary range. Its way over kill to drop it that low on a psd or a cummins for that matter.....
 
ive got a97 dodge and i dropped comp just a lil not quite sure what it is now but with the fuel i have and timeing im running it doesnt want to start at all if its cold out like holy smoke said a can a week and if its cold enuff more like a can a day the other week it was like 70 degrees here and it still didnt start had to shoot it once to get it to fire and then crank and crank till it fired so u might think about that if its really cold where you live good luck
 
How do you figure a compression ratio? I cut 100 thousandths off of a 17.5 to 1 Mahle Piston with the larger bowls and i am using the regular head gasket.
 
I wouldn't run less than 15.5-16 range if you are going to DD it. It really depends on your setup, and your view on what is streetable.
 
Jetpilot said:
12:1 to 13:1 is a great begining point but starting can be fun.
Click to expand...

Do you guys use something like this ?

its copy/paste from Fleetguard homepage:

Heavy-duty Starting Fluid Systems
We offer both electrically and manually actuated starting fluid systems. All kits provide a measured shot of starting fluid into the diesel engine manifold on demand, which aids ignition at low ambient temperatures. Most kits include the most popular atomizers, which are color-coded for easy installation.
 
i run 15.5:1. i used to have a prob starting when it was cold. turned out to be a mis adjusted gov spring. took the pump to a highly qualified pump shop and they tuned it, now the truck starts without a hiccup.
 
sweet, i have been in the ballpark of 16-16.5. im going to call BWD and talk it over some more, thanks agian for the input guys
 
13.32 has been driveable through the winter with the truck plugged in if it sets for more than 5 hours. I also unplugged the IAT sensor so that the Wait to Start function runs the grid heater for 30-45 seconds at a time.

brandon.
 
13.32 CR would explain why you can run massive amounts of nitrous and timing without hurting anything but the starting...I wouldn't have thought it would be that low!

Chris
 
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