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Discussion Starter #1


Posting this relatively late, but here's a dynosheet of my low compression Marcy Motorsport-built Zetec. Dyno used was a Dynojet, at McNews Automotive. It was a 3rd gear pull.

Specs include:

Short block
-8.2:1 FC/Probe pistons
-Eagle Rods
-New Ford block, crank assembly; balanced and all that good stuff
-ARP hardware

Head
-Marcy Motorsports ported and polished Zetec head
-Stainless Steel 1mm oversized intake and exhaust valves
-Comp cams Stage 1
-ARP hardware
-Focus Central cam gears

On top of this, the motor has an AF/X udp, an FC off-road pipe, SVT intake extension duct, and an SCT chip. At the time of my ordering from FS, it was just about the only SCT mail-order tune ever ordered/made for a low compression, NA Zetec. So it isn't exactly the most optimal tune, even though there really isn't much to expect from a NA, low compression motor such as this, regardless of tune.

That's all I can think of off the top of my head right now. But those are the meat of the parts. The plan was to run this motor for a few thousand miles before having the turbo slapped on, just to break it in. But we all know how plans go...


I've racked up just under 12,000 miles so far. Thankfully though, it is running strong. I have an oil leak, but as far as I know at this point, it's a minor leak between the windage tray and actual block. It seems to be a bad gasket job. I'm filling up oil every now and then, which can be really annoying (
) depending on how the rest of the day is going. But for the most part, it seems pretty healthy, not to mention slow as hell.

I will be doing a proper tune-up soon. Compression and leakdown test included. And of course, my plans for an FI setup will be realized eventually.


Have any of you guys with similar-spec motors ever dynoed?
 

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the low compression pistons are KILLING your power. But yah... hit Randy up for a newer version on the SCT Tunes and you should see a couple HP improvement.
 

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8.2:1! Wow!
That thing is *begging* for some serious boost.
 

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wow. those numbers are pretty solid for having that super low compression.
 

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Yeah definetly hurry up with the boost on that compression. I dynoed higher with a stock zetec with 40k on it.
 

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Yeah definetly hurry up with the boost on that compression. I dynoed higher with a stock zetec with 40k on it.
I thought our cars (zetec) dynoed around 105 stock??? He is getting around 130 hp to the wheels with a point and a half less compression. Sounds good to me. Feed it what it needs (more air) and she should scream!!!
 

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Discussion Starter #7
Actually, the motor's only making 117 peak whp, and 112 peak tq.

What I'm most interested in is not the peak numbers but my curve. I was happy to see the hp curve continuing on up top, as well as the tq curve staying relatively flat. But, is this the outcome only because of how the motor is setup as it is right now, being a low compression, naturally aspirated motor?

What can I expect when I install a turbo setup? I'd imagine the stock intake manifold will start becoming a hindrance in power real quick.
 

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There are 3 main things that effect the power curve of a NA engine: the intake runner length, the cam timing, and the exhaust style/size/runner length. Change any of these and generally speaking you change where the power is the best at, optimally you choose all 3 to match the RPM's you want power in. This is the reason aggressive cams, high RPM intake, or "race" header by themselves do not usually make more useable power on a stock car (they might make more power within a small RPM range, but they kill power outside of that). Add all 3 tuned for the same RPM though and you can gain incredible amounts in that RPM range.

When you add boost into the equation, if the above 3 are kept the same, the curve will be the same except it will obviously be higher where there are higher amounts of efficient boost. If you simply could pressurize the intake at all RPM's with the same pressure your curve would follow the same general path it would just be higher numbers.

Since your going turbo the curve might change some due to the exhaust manifold used for the turbo because it may have some tuning change to the curve. But overall I would expect a similar curve except obviously the power will swell once the turbo spools up. Once the turbo is spooled it should follow the same general curve pattern (as long as your not having to pull a lot out of the tune at the upper RPM's.)
 
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