BSFC Chart for VE 5.9?

[VMacKenzie]

Anyone ever seen a BSFC chart (brake specific fuel consumption) for a VE Cummins? I am curious to compare it to the P-pump version. BSFC charts are a good indicator of engine efficiency and torque at different RPM.

I have compared P-pump 12V and VP-pump 24V charts and while the 12V is more efficient at lower RPM (1600-1800) the rate of fuel consumption for a 12-valve rises very rapidly once you get much above 2000 RPM (it consumes much more fuel than a 24V by 2500).

I thought it would be interesting to see how a VE compares to a P-pump since it has dynamic timing and the P-pump is fixed.

Vaughn

[dpuckett]

The charts in the TDR magazine a few years ago showed the best BSFC for a VE at around 1800rpm; P-pump around 1500, IIRC. Seems that the VE pump chart didnt raise as sharply as the P-pump either til about 2200, then it rose sharply. Keep in mind, this was the Cummins publication for a STOCK engine.

If I get time, I'll dig through the old magazines and have a look-see.

A lot of your BSFC curve depends on timing, injectors, what you have done in terms of air/ exhaust improvements, cam, head work, etc. Any little thing you do will change the curve.

Daniel

[VMacKenzie]

Thanks Daniel. I do realize mods affect BSFC but stock charts give you an idea what you have to work with fundamentally. Basically I am trying to learn a couple things. One thing I notice with the P-pump 12-valve like on my '98 is the MPG drops dramatically when I sustain ~2300 RPM or more, more so than a 24-valve. Towing with the automatic I'm frequently running the RPM up in Direct, the gearing on the auto has you lugging it or winding it up. I find myself running 22-2300 RPM a lot. I thought maybe since I understand the VE varies timing with RPM it wouldn't be as much of a fuel hog at higher RPM.

I've read all around this forum but don't fully understand VE pump timing, I guess it varies by up to 6 degrees, but what is typically the base timing point? Maybe around 12 BTDC like a P-pump, giving you ~18 degrees at full advance? At what RPM does advance begin, and when is it fully advanced? And can that be changed. . . could it be spread over a wider RPM range so max advance comes at say 3000? How does the pump advance the timing mechanically? Is there a way to get more dynamic advance to the tune of 8-10 or more degrees?

I saw a timing chart for the 24-valve, the VP44 advances timing to as much as 24 deg BTDC as I recall, giving it roughly 15 degree range.

Vaughn