Unique Motorsports

In Part two of the series we do a little more advanced modifications.

Race Cat: Having a CAT right after the exhaust manifold is great to help your car warm up and fight cold start emissions. It’s not so great for good exhaust flow. Here are some pictures and results of replacing the Cat with a straight pipe.  I also did some light porting of the exhaust manifold, most of which was on the outside to remove casting marks.

Anyone can purchase a bunch of bolt on MODS and make their car faster. What if you don’t have that much money to spend on the car or the car is like a Daewoo Lanos and doesn’t have much aftermarket support? Also, how do you know what MODS will give you the most bang for the buck? This article will focus on the MODS most people can do, without spending lots of hard earned cash and still get some great results.

Since the motor is basically a big air pump, the first thing I will work on is the breathing. Increasing the volumetric efficiency on a newer car does not have the results it would on say an 80’s car, but it’s still the best place to start. The goal is by allowing the engine to breath more easily, it will breath more and hence, more power.

Notes regarding performance testing: For a baseline run, all I have is the 0-60 times I took soon after buying the car. For a more accurate 0-60, I should have a space of road that I can go both directions and take the average, but that’s not available. All the 0-60 times are taken from a specific stop sign where I’m not breaking the speed limit. Also, since the car is an automatic and doesn’t have enough power for wheelspin, the times are very consistent. Future MODS should have the other information as well.

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Total Fuel Flow (lb/hr) = Injector Size (lb/hr) X number of injectors

To convert lb/hr to gallons-per-hour divide by 6.25.

To convert from pounds-per-hour to liters-per-hour divide by 1.64.

To convert from gallons-per-hour to liters-per-hour, multiply by 3.8.

OK, now that this is out of the way lets figure out what I need for my 200 hp 1.8L.

The injector size we figured on is 29.4 pounds/hr

Total Fuel Flow (lb/hr) = 29.4 X 4

Total Fuel Flow (lb/hr) = 117.6

Now we have to convert it to Liters-per-hour since that’s what most pumps are measured by.

117.6 * 1.64 = 192.86

So the fuel pump needed will only need to flow about 193 LPH.

Wondering how much power it will take to get your car up to 200 MPH? Here’s an equation to help you find out. (this information is from August 2001 Sport Compact Car)

Aero Horsepower: Drag x Speed or HP at the wheels

Frontal Area: Amount of Frontal Area (large hood scoops, mirrors and bumper openings add to this and decrease your top speed.

Cd: Coefficient Drag.

Speed: In MPH

Aero Horsepower (wheel horsepower) = 0.000007 x Frontal Area x Cd x Speed³

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Higher static compression creates more power throughout the rpm band, but it’ll lower your maximum allowed boost before the onset of detonation. Boost is worth way more power than compression, because boost raises your compression and your total air flow at the same time. With the down side of, when you’re not on the boost, you have slightly less power.

Effective Compression Ratio = static compression ratio x (1 + boost/14.7)^1/2

For a car running 8.5:1 pistons and 18psi(~max on pump gas)

8.5 x (1 + 18/14.7)^1/2 = 12.67 ECR

If you run 9.0:1 pistons and want to maintain the same 12.67 ECR (~max on pump gas), you’ll have to lower your boost to: 14.4psi

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