Project 5.0 Mustang: Improving the Breathing With Ford Racing and Cooling with CSF

by Mike Kojima

In previous installments of our Project Mustang we had installed most of the common bolt ons for our 5 liter Coyote engine.  We had gotten a pretty decent boost in power but we had noted that our power would really fall off at higher RPM, more that what we thought a free breathing 4 valve motor should.

What we did notice is that Ford produces a few different OEM intake manifold designs for the Coyote. The two options that interested us were the Boss 302 and the Cobra Jet.  The Boss 302 intake manifold is what came on the Boss 302 model obviously. It has much shorter runners than the stock intake manifold and a larger plenum using the stock throttle body.  When checking out dynocharts online the Boss 302 seemed to definitely give a top end boost at the expense of a little loss on the bottom end.

We also checked out the Cobra Jet intake manifold from Ford Racing.  This was the intake manifold that Ford created for the naturally aspirated Cobra Jet drag car.  The Cobra jet manifold needs a really big Ford Racing oval throttle body and a specially designed Ford Racing cold air intake to mate with the throttle body.

When looking at other peoples results online, this seemed like the manifold to get for a stock Coyote with long tube headers. The Cobra Jet intake manifold seemed to have the same slight bottom end loss as the Boss 302 intake manifold but a definite gain over the Boss 302 on top end.  So the Cobra Jet it was.

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The Cobra Jet manifold has inlet runners considerably shorter than stock.  This contributes to top end power. The runners are about the same length as the ones on the Boss 302 intake.  The Cobra Jet intake is molded from thermoplastic, the plastic does not conduct heat too well which helps keep the intake charge cool.  The smooth interior of the runners should contribute to good for flow as well. O-rings around the runners ensure a positive seal to the cylinder heads.
The Cobra Jet intake has a huge opening for a really large oval throttle body.  The oval shape means you have to stick to Ford Racing's offerings but the size is large enough to accommodate just about any power level that the engine is capable of.  The manifold features a nice O-ring seal for the throttle body.  You can see how large the plenum of the manifold is as well.
The Ford Racing throttle body is one of the largest we have ever seen.  Its oval shape probably makes it less sensitive to idle control issues which is critical for drive by wire applications. The throttle is a complete drop in unit with all the drive by wire stuff pre installed. 
The highly polished throttle body comes with a throttle position sensor.  The part is high quality, much better than your typical aftermarket fare. Everything is set to drop in with nothing to mess up.
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Tuesday, September 29, 2015 12:27 AM
Impressive with no low end loss.
Always been envious of Fords and their Ford Racing parts :)
Tuesday, September 29, 2015 7:43 AM
Impressive! It's amazing the number of parts available from the factory for Mustangs. I considered the Cobra Jet stuff but figured the improvement over the stock Boss intake wouldn't be big enough to justify the investment.

How is it suddenly safe to run it 1000 rpm higher? I always thought RPM caps were to protect the engine internals, but with just an intake change you went up 1000rpm.
Tuesday, September 29, 2015 7:46 AM
BTW that extra RPM will be very useful. There were two places at MRLS where I'd have to shift up, just to bang it back down again a second later if it weren't for the extra 500rpm of the Boss 302 motor.
Mike Kojima
Mike Kojimalink
Tuesday, September 29, 2015 9:03 AM
Awesome screen name!
Tuesday, September 29, 2015 10:28 AM
Red coolant was drained but green stuff was put back in. Hope it was the universal kind?
Tuesday, September 29, 2015 10:34 AM
@Nikko - No, I'm sure they have no idea what they're doing.
Tuesday, September 29, 2015 10:36 AM
A pulsed brake on the Dynojet, I knew they existed, but they aren't common. I think it's been a long time since they've even been sold.
Shane Laake
Shane Laakelink
Tuesday, September 29, 2015 12:29 PM
I'm guessing the extra 1000 rpm is there now or rather wasn't there before due to some or all of the following:

Performance wasn't there anyway (this is what the intake/throttle fixed)
Wear/warranty (I assume that's been voided for any number of reasons)
CARB/EPA (no VW tricks here, but Ford has certain considerations)
Aggressive custom tune (while streetable, we're not looking at something tested for all climates/conditions/etc)
Tuesday, September 29, 2015 1:19 PM
did you guys do anything to the engine to keep it reliable at the higher rpms? one of the things that came up when I was researching this manifold for my mustang was the factory oil pump gears being weak...
Mike Kojima
Mike Kojimalink
Tuesday, September 29, 2015 2:16 PM
We have Ford Motorsports oil pump going in. As far as the extra 1000 rpm. It's obvious from the dyno chart, the old manifold made no power up there so no use reving there.
Tuesday, September 29, 2015 8:41 PM
Was the stock intake already on a custom tune?

Wondering if we are comparing apples to apples.
Mike Kojima
Mike Kojimalink
Tuesday, September 29, 2015 11:08 PM
No it was not. The new intake will not even run without a tune.
Wednesday, September 30, 2015 9:11 PM
Man I wish you'd posted a video, nothing like a V8 screaming that high.
Friday, October 02, 2015 2:18 PM
Why the choice to go with the CJ cams?
Mike Kojima
Mike Kojimalink
Friday, October 02, 2015 2:46 PM
The cam that a lot of people use, the Comp Cams NSR has more duration but less lift than the CJ cams. I think the CJ cams might have a wider powerband because of this. The NSR cams need to have the variable cam timing limited as well.
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