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Escorting Power

After more than 120 dyno runs, we've found some of the changes you can get from playing with the intake and exhaust!

by Julian Edgar

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This article was first published in April 1999.

Mike Dale loves Escorts. For years he rallied one, he had a hand in the build of a BDA-powered Escort, and his own street/drag machine has undergone extensive development. Not the sort of development where a couple of things are changed, the results measured and then that's it; no, we're talking here about day after day of dyno testing, the little 2 litre Pinto shrieking at 8200 rpm....

The Engine

Ford's Pinto 2 litre engine went on later in life to grow into the Cosworth turbo mill, so there's lots of good stuff around for it. Mike's built an engine that uses a cost-effective array of parts. The SOHC head is from a 1600, which gives it smaller combustion chambers - all the better to get a high comp ratio. It's been treated to new stainless valves, 44mm on the inlet side and 38mm on the exhausts. The head was also treated to some porting, giving a flow of 229cfm (at 28 inches of water) on the inlet side and 176 cfm on the exhausts (both at 500 thou lift). You want the full flow chart? Okay, here it is:

Valve Lift





















Comp ratio is way up thanks to that aforementioned head and a set of heavily modified TRW pistons. How high? Try 12.5:1. As you'd expect, the engine runs on BP100. The rods have been pinched from a Sierra Cossie and are 40 thou longer than stock Pinto items. Down below there's a standard Escort 2 litre crank - apparently untroubled by the rpm being thrown at it. The crank's been balanced and the flywheel's dowelled to one end. Kissing the flywheel is a ceramic button clutch, and on the other side of that is a 'Rocket' gearbox.

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Flow into the head comes through two Weber-style quad throttle Injection Perfection throttle bodies, each running a 45mm butterfly. The injectors screwed into these are Holden VN Commodore V6 items, modified for better flow in a way not revealed by Mike. Even with the mods, they still run flat-out at high revs... Engine management comes in the shape of a Haltech E6A, running both the injectors and also quad Mitsubishi Galant VR4 coils. The crank trigger replaces the original dizzy, using a Mitsubishi TR Magna Hall Effect sensor grafted into the original Ford base and shaft.

In the head is (currently) a Camtech 737 cam that provides 520 thou actual valve lift at the inlets and 515 actual lift at the exhausts. The modified rocker gear comes from Camtech, while the double valve springs are provided by Crane. Fluid flows come from a VL Commodore fuel pump and the standard oil pump, with ULX the brand of slippery stuff being circulated.

OK - nuff on the build. How about the tuning and development?


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Mike started off with 4-2-1 extractors of an unknown make - but English, anyway. These originally connected to a full 2½ inch exhaust, comprising a straight-thru resonator and a reverse flow muffler. The power line in this form is shown by the red line - a peak of 93kW but a bit saggy in the mid-range. (All power curves go from 3000 - 8200 rpm.) The exhaust was dropped and a side dump pipe used.

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With a 31 inch dump (as measured from the collector) power (shown by the blue line) was much stronger in the mid-range, even if it only peaked at 90kW. Still , the car would have been faster on the road - it's average power was higher. Mike then tried different exhaust lengths. We've showed one of the worse here - with a 43 inch exhaust (green line), the power had one helluva dip in the midrange - understandably, the dyno run was aborted. The other lengths tried around 31 inches gave only minor gains or losses in power, so 31 inches was it.


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Mike had two cams to play with - a Kent RC31 and a Camtech 737. On paper both have pretty well identical specs, but the Camtech has a bit more overlap. The blue line shows the Kent, which peaked at 94kW and had a bit of a dip at high rpm, while the red line shows the stronger Camtech design. The Camtech peaked at 98kW.

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With an adjustable sprocket fitted to the front of the cam, timing changes were pretty easy to make. But unfortunately they didn't make a helluva lot of difference - this graph shows the difference that retarding the cam timing by 1 degree made. A couple of kilowatts here, a couple lost there. No big deal, on this combo at least.


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After playing around with the cams, Mike decided to swap extractors (headers). The originals were 4>2>1, using 1¾ inch primaries and 2 inch secondaries. The combined length of the primaries and secondaries was 30 inches. The power made with these fitted to a 30 inch long, 2½ inch tailpipe is shown by the black line. He then fabricated a set of 4>1 pipes, using 31 inch, 2 inch diameter primaries flowing into a 31 inch tail pipe. This boosted top end power (green line), with the grunt hanging on right to the rev cut. However, the 4>1's lost a bit lower in the rev range.


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So you reckon that changing the cam from a Kent to a Camtech made a fair bit of difference? Well, check this out. Here's the cam changes (red and blue) shown against the gains made by changing the intake tuning (green line)! Pretty good results, aren't there? Well, you ain't seen nothing yet.


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But before we get to the intakes, at this stage Mike decided to change diffs. In went a 4.4 and out came the 3.9. And what a difference that made to the power curves! We're not sure if it's an artefact of the dyno (maybe it didn't like the change of roller speed) or what, but the blue line shows the 3.9 and the red line the power with the 4.4 new diff fitted. If the dyno's reading accurately, changing diff ratios cost as much as 14kW at the wheels!

More on Intakes

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The Injection Perfection throttle bodies take bolt-on intake trumpets, and Mike had a whole variety of lengths and designs to play with. We won't show all of the tests - just three. The blue line shows the power with a 14.5 inch intake runner length (from the end of the Weber trumpet through to the intake valve). As you can see, power peaked at 88kW. Pulling these off and swapping to 12 inch intakes took that up to 98kW, while 13.5 inches was the optimal length giving an even 100kW. These changes were made one straight after the other, so it can be said with certainty that swapping intake trumpets gave a change of 12kW!

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Yup, fine - getting good results from 13.5 inch trumpets. But were they going to remain bare and open - or were filters going over the top? Mike believes that sock-type filters wrecks the flow into the belllmouths, so he intended using an airbox over them. But what would this do to the intake tuning? He made a cardboard airbox and placed it over the intakes.

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The red line shows the starting point - using long runners and with a bit of a wobbly power curve, peaking at 98kW. The blue line shows what the airbox did - lifting power at one point but causing a 5kW dip in the curve at higher revs. So yup, an airbox sure does change the tuning characteristics! So what about putting a feed tube to the airbox? A short 3-inch intake duct was fitted, with the power then made shown by the green line. The power curve was smoothed out, still peaking at 98kW but being a few kilowatts down at lower rpm.

Ignition Timing

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Running the engine on Haltech E6A management meant that Mike could easily dial up whatever ignition timing he wanted at a stroke of a key. With 32 degress total advance the power curve is shown by the pink line - a smooth sweep to 90kW with the rest of the tuning elements set up like this. But with the timing advanced to 36 degrees, power dropped by 6kW at the top end, with the wiggly curve showing that the engine sure as hell wasn't happy with this much advance. Interestingly, power also fell at the bottom end as well.


Some of these tuning changes made a radical difference to power, while others didn't do much at all. Unless you do lotsa dyno runs - or carefully time the acceleration on the road - you could be working totally in the dark. One thing's for sure, there's a lot more to setting up an engine than just building it!

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