COMP461
Comp Diesel Sponsor
- Joined
- Apr 23, 2006
- Messages
- 4,009
I see no reason to go above 17:1. You will be money ahead working out a secondary that will boost early, rather than try to gain a bit off boost.
What seems like a small change in compression ratio, can make a huge difference in pressure ratio......
I agree on small changes, the stock ratio is 17.2, and if you check it its closer to 17.35 to one, so an increase to 18 5 to 19 to one is not out of the question. NA diesels are in the range of 22 to 1.
This compression is for a 600 hp street truck, where someone wants a truck with instant throttle response, little to no smoke, and fuel economy. You must address airflow in this equation. And improved Intercool is critical, a camshaft designed for this application, and cylinder head work. Not everyone wants all the hp they can make, its fun to have a truck that runs good and exhibits zero to little lag. I talk to many people every week, when helping them pick out a cam for their truck. I ask the same question “what is you honest and realistic intended use of this truck” , “ do you have to drive this truck every day , and do you have to depend on it “ . I then give them a realistic guidelines for achieving those goals .
If they are not asking for a all out build, and this vehicle is one they will have to depend on. Then the 1000 hp parts are not necessary. Out are big twin pumps, big injectors, and loose AR turbo’s.
So where does raised compression become applicable on racing programs.
First on limited turbo engines such as 2.6 . You can only get so much air in to the engine, the more compression you use, the looser AR you can use, and this allows gain in power by reduced turbine inlet pressure ( drive pressure ) .
Next this allows you to keep the intake valve open much longer, moving dramatically more air, this ability to move more air on these restricted turbo engines, drops boost down. If at the same turbine speed you have a reduction in boost, you move more CFM of air at a lower temp. This lower temp means denser air charge.
It all goes hand in hand , with compression.