7 June 1996

Engine clean-up gives extra power boost to 7200-series

CLEANING-up engine emissions has given a power boost to the 7200-series Magnum tractors from Case, writes Peter Hill.

Each tractor in the five-model range is powered by an 8.3-litre six-cylinder turbo engine assembled at the Case-Cummins joint venture, Consolidated Diesel Corporation, in the US.

Changes to engine specification on the top four models to meet North American emissions regulations include fitting different injection nozzles with higher operating pressures, new fuel pumps and a fuel cooler to maintain fuel density. All of which is designed to pump more diesel into the cylinders while also improving combustion efficiency.

A wastegate type-turbocharger, currently used only on the top horsepower 7250, is also now used on all but the lowest-powered of the engines. It allows higher boost pressures at low to mid-engine speed by releasing excessive boost at the top end.

The combined result is a modest but useful increase in power output to add to the engines "power bulge" characteristics. This sees horsepower rising initially as engine revs fall from rated speed, so that peak power output (at 2000rpm) coincides with the key 1000rpm pto speed.

The top three models gain an extra 3hp at peak output, while the 7220s maximum power goes up by 12hp from 188hp to 200hp. Peak torque output rises by 4.2% on this model, while the 7240s torque curve rises by 5.6%.

Introduction of the new-spec engines has prompted larger radiators with an air inlet in the top of the bonnet rather than at each side. The power take-off control is now electric instead of manual and there is a larger seat. Adopting US-spec front weights increases the standard ballast complement by 300kg (661lb).

The electric pump that on current Magnums provides emergency steering in the event of power failure has been eliminated by a change of valves in the hydraulic steering circuit. &#42


Case 7200-series Magnum range

ModelOld hpNew hp

@ rated@ maximum@ rated@ maximumspeedoutputspeedoutput

2200rpm2000rpm2200rpm2000rpm

7210155hp155hp155hp155hp

7220187hp188hp190hp200hp

7230206hp213hp207hp216hp

7240233hp246hp234hp249hp

7250247hp264hp249hp267hp