Turned up 4BT

[driverswanted]

Question for 4BT owners:

How has turning up the power ( +170 hp) of your 4BT affected your accelleration and towing/loaded highway performance in the 1700-1900 rpm range? What adjustment had the most influence on the turbo spool-up at those RPM's? It seems pretty easy to get my HY35W to come alive at 2000 rpm but I've not advanced my pump yet. Looking at my ratios (nv4500 + 3. 55) and tire size I want (32. 6"), I need to build some good loaded handling and accelleration in this RPM range. Any suggestions on the pump adjustment would be appreciated.

 

[fox]

I will assume you have a rotary pump.

You need more fuel. Turn the fuel screw in 1-11/2 turns and try it.

More info will be in the first gen forums.

I have limited experience but did fuel up on in a bread truck. It REALLY helped it.

Got PYRO?

 

[driverswanted]

Yes I have the VE pump on a CPL 767. The 767 timing starts at 1. 66mm unlike many other Cummins engines that start at 1. 50 or so. I was advised to set my pump to 1. 50-1. 52. This was by someone who did not know my CPL number and the proper starting point. I looked at my pump manual and saw the significant difference between where I was told to set it vs. where I was supposed to start the advancement changes. At that time I did set it to his recommended setting and of course now have a retarded pump timing instead of advanced. I will be correcting that this weekend. The power screw is in one turn, but again I am not seeing much from this, I assume because of the retarded pump timing which may be dumping the fuel from the Bosch 190's into a portion of the piston's down stroke.

Yes I have a home-built digital pyro and I have the TC in number one exhaust port of the manifold.

So, I guess your response is yes I will see a significant improvement in response in the 1700-1900 RPM range with the power adjustment.

 

[JLEONARD]

Yes it will be improved. A smaller exhaust housing on the turbo will help. When I went from a 18. 5 cm to a 16 cm I was able to start spooling about 400 rpm lower.

 

[driverswanted]

Yes it will be improved. A smaller exhaust housing on the turbo will help. When I went from a 18. 5 cm to a 16 cm I was able to start spooling about 400 rpm lower.

Do you mean something smaller than my 9 sq. cm. HY35W?