T35 - T25 - The differences.
The difference between the T25 small turbo model and the T35 big turbo
homologation model is mainly in the engine department. The most noticeable change
being a much smaller turbocharger to increase the driveability of the car. The first
models up to july of 1994 was fitted with a Garett T35 turbocharger which had
one purpose and that was that it needed to be big enough for rally use as homologation
rules specified that the turbocharger needed to be the same in the rallycar as in the
homologation model.
The engine changes from the T35 model to the T25 model are as follows:
- Garrett T25 low inertia turbocharger
- Ford EEC-IV engine management system
- New throttle body - To improve torque lower down the rev-range
- New exhaust manifold plenum chamber - As the new throttle body to improve low-rev torque
- New engine coolant / air temperature sensors
- New crankshaft pulley and new engine speed sensor
- New sequential fuel injection timing sensor - To go with the new Ford engine management system
- Mass air flow sensor , the T35 did not have this at all
- New long-life spark plugs. Well, well...
- New breakerless direct ignition system with high tension spark plug mounted coils
- Improved long-life oil filter (extended 10,000 mile oil/filter change intervals)
- Redesigned high speed oil control system w/ new baffles and separator
- New oil pump and piston oil spray jets - New piston oil spray jets to improve
the cooling of the pistons. The new jets are machined into the main oil gallery
as opposed to the old oil spray system which used a pipe out of the oil pump.
The new jets are individually
pressure controlled, they don't spray the pistons unless the oil pressure has built up in
the main gallery and they have a better spray pattern and
direction.
- Redesigned cylinder head incorporating new long-life valve guides
- New long-life engine oil seals
Other changes are as follows:
- Smaller more aerodynamic side mirrors
- A different fuel tank cover with with a colored flap
- Some minor changes to the suspension which leads to the
small turbo model having less clearance for big wheels. The
front spring platform is closer to the weel.
As a result of the change to a smaller turbo and other minor changes the
engine characteristics changed considerably.
The new power curve peaks at 5.750 rpm instead of the 6.250 rpm of the T35 model.
The torque curve holds 90% of max torque over a 20% wider rev range.
In addition the overboost time increased from 2-3 seconds up to 8 seconds.
Back to Sigmund's
Ford Escort RS Cosworth page.