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1988 Honda CRX HF - Inbox

Mar 1, 2009
Sccp_0903_01_z+1988_honda_crx_hf+car_exhaust Photo 1/1   |   1988 Honda CRX HF - Inbox

OK, wiseass, so you need some space to vent. Here it is. Direct letters to the editor to sccnews@sourceinterlink.com and we'll do our best to come up with a snide response. Or completely ignore you. But hey, at least you've got a voice.

Letter Of The Month
You guys keep asking for ideas on different project cars, so how about a monthly "virtual" project car? Give a writer a price point, say $12,000, have him do some research, and write an article about what he could buy with that [money].

He could either get the best used car he could for $12,000 or less (which would make for a pretty boring article) or he could drop $5,000 on a car, put $7,000 into it, and then tell us what he would get and where he would get it. Installation fees for advanced installs would also need to be accounted for in the price. Each month, different writer, different price point. This would be more applicable to most of your readers than a twin turbo setup for a 350Z that costs more than my car. You guys wouldn't have to buy anything, just do the research. The only thing we wouldn't know is how everything performed when it was done, but the writers could go to different forums and find out from enthusiasts what works for those cars and what doesn't work, as well as what the cheapest options are.
Jerome Adams
Biloxi, Miss.

Of Like Mind
First off, I have to compliment the editor on the wit used in each article. It's not often I find humorous articles in the local newspapers and this mag is chock full of the good stuff. In reading comments to your articles, it would seem that most are more concerned with the specifics of anything they didn't care for in one article of the past or another. My comments are simply to the editor. I think you have done a wonderful job filling in spots between pictures and I can tell you I am personally pleased with the overall reviews. Keep up the good work and keep the humor coming. Regardless of whether you read this (or even publish it [wink, wink]), I am a true fan of your efforts in educating the general population of sport compact enthusiasts. Your innuendo humor in every aspect of this mag is very well put together. I was thoroughly impressed by the amount of thought put into each one for your readers' viewing pleasure. Just wanted to say keep up the good work and love the insight.
Daniel Walters
SoCal sport compact car owner and enthusiast

Oh the irony. You should have sent this letter to our publisher a little earlier. -JC

The DTM SRT-4
I'm a big fan of DTM racing because most of their cars sport side-exit exhausts. They're not very common on the street but many classic cars sport them, like the Corvette and Viper, some trucks, and the '93 240SX featured on your site.

There are many statements on various forums from people saying that kind of exhaust will melt the rear tire rubber very quickly, dirty the wheels, and make the finish peel. As a DTM lover, I want it badly. What are the myths and facts regarding side-exit exhausts?
Philip Christian
Lansdale, Pa.

Project SRT-4 has a side exhaust and it's been the bain of Editor Leh. It always turns out that whoever is driving decides to fire up the car just as the rear driver side passenger is about to get in. There's nothing like oil, gas, and water all over you new white pant legs. That said, unless you redesign the exhaust hanger system so that the exhaust isn't cantilevered on the side, you will run into problems like we did. The constant bouncing and weight of an exhaust with an unsupported torque arm will eventually break the piping metal as ours did. As for melting bumpers, our rear exhausts do that already, so it's a wash. Your tires should be fine depending on where you make the exhaust exit. -JC

Stupid Speed
I have a question regarding stupid speed. For starters, I love small, light cars. There's purity in driving them. I've driven a few second-gen CRXs. WOW! Put them in a corner and hold on tight! I'd love a '88 CRX HF with a motor swap but I'd want more power. The K20A puts out strong numbers without even being warmed over. Intake, exhaust, cams, a valvetrain to match, and a good tune would be sweet. But what about the bottom end? How can you make it rev more? Lightweight everything and upgraded rod bearings? Could you bore it out? What about sleeves? I'm thinking about a sleeved and bored K20A at about 2.2 liters, titanium rods, and lighter pistons (maybe a little more compression). Does that sound good or should I leave the bottom end alone?
Nathan S. Kalaskie
Springfield, Ill.

Honda makes a damn good engine out of the box. Those guys have done their homework and are smarter than we are. That basically means that the K20 is the best balance of power, emissions, economy, and driveability. High revs and bored sleeves are all the makings of a race motor that won't be worth a crap on the street since you'd be spending 90 percent of your time trying to get to a rpm where the engine actually makes power. The swap itself will liven up the car more than what most people know to do with. Keep it simple and make sure the car runs before thinking about tearing into an engine. -JC

Hydrogen Fuel-Water Gas, Brown's Gas, my A$$
The fact that a 2.0L motor would burn 78.5 liters of hydrogen gas per minute can't be right. There are 3.7854118 liters per gallon, so you're saying that a 2.0L motor would be burning 20.738 GALLONS OF HYDROGEN PER MINUTE?! No way.

I found specs for a '95 Ford Taurus 3.0L V-6 rated to burn 7 liters per hour idling and roughly 21 liters per hour when traveling at 60 mph. That would mean that it burns 0.117 liters per minute idling. Now if we use that air/fuel value of 33.43:1 for hydrogen, and for the sake of simple math we just divide those liters by two, we would use 0.0583 liters per minute of hydrogen idling. WHERE ON EARTH did you get the 78.5 liters or 20 gallons per minute for a 2.0L motor?

I've had a subscription to SCC for years and I went back to read your article because some guys at work were talking about water gas. Please let me know if your 78.5 liters or 20.738 gallons per minute was a typo.
J. R. Crosby
via the Internet

Didn't I say, "Don't ask me how I calculated this"? I thought SCC readers were supposed to be smarter. Did you not notice the number of times I mentioned MASS RATIO? And you just had to email me when people finally stopped responding to this article and I threw away my paper calculations. The reason that you're wrong is called MASS RATIO. Just to be sure we're all on the same page, let's hold hands like little boys and girls and go through this again from the top.

Here's how it goes: Let's assume that the engine has four cylinders and is exactly 2,000cc in displacement. That means that at WOT, and assuming 100 percent volumetric efficiency, 500cc of air will be sucked in for every two engine revolutions (since it's a four-stroke engine.) At a high idle speed of 1,000 rpm, each cylinder is ingesting 250,000cc per minute or 250 liters of air per minute. You get this by multiplying the air sucked in per cylinder times how many times it's sucking in a minute, which is half the engine speed (500cc times 1,000rpm divided by 2 revolutions per cycle). Multiply this by the number of cylinders in the engine and you have 1,000 liters of air per minute. But this is as if the throttle was wide open and the engine held at 1,000 rpm.

At idle, the throttle plate is closed and the engine pumps just to get enough air to survive. This pumping generates a vacuum inside the manifold. Typically we measure vacuum in inches of mercury or in Hg. Most cars idle near 20 Hg. For engineers, we like to deal in kilopascals (kpa) since it's metric and actually makes sense. One atmosphere, or 14.7 psi, is 101.4 kpa on the absolute scale. You can find the conversion here: www.engineeringtoolbox.com/vacuum-converter-d_460.html. So 20 in Hg gauge vacuum is about 28.5 kpa.

Last time, I ball parked my calculation strictly based on the approximate percentage of pressure the vacuum accounted for and just multiplied the WOT flow rate by the percentage of the vacuum. Since pressure and overall vacuum isn't a linear relationship, I assumed a generous 33 percent of the WOT flow rate to get the idle flow rate, which brings us to about 259.3 liters per minute of air at idle.

In reality we also have to account for the volumetric efficiency (VE) at idle, now that you want to nit pick. While valvetrain and flow characteristics do little to affect the minimal flow at idle, frictional drag inherent to each engine design does. A typical VE at idle is ball parked at 56 percent, although different designs might vary by up to 20 percent. So taking our WOT flow of 1,000 liters per minute and multiplying by the VE and percentage vacuum (28.5 divided by 101.4) will get us 157 liters of air ingested per minute. Almost half of what my original paper napkin approximation was since I ignored VE. Still it's a huge amount and few people realize just how much air an engine will eat up.

So now we know how much air this engine consumes per minute at idle. This is a volumetric flow rate, not to be confused with a MASS FLOW RATE! We can't just multiply the air/fuel ratio by the volume of air consumed and figure out how much gas you consume, like you did. Before figuring out how much fuel you burn, the volumetric flow rate has to be changed into a mass flow rate since a gram of gas takes a lot more space than a gram of liquid fuel.

This requires some knowledge of chemistry and the ideal gas law, which I'm going to assume you know nothing about based on your email. You're just going to have to trust me when I say that every liter of air at standard temperature and pressure (STP) weighs 1.29 grams. For the volumetric flow rate of 259 liters per minute (68 gallons per minute) of air, the ideal gas relationship works out to be about 335 grams per minute (0.74 pound per minute) of air. With the more accurate flow rate of 157 liters per minute (41 gallons per minute), the mass flow rate works out to be 203 grams per minute (0.45 pound per minute) of air.

Now we can finally use our air/fuel MASS RATIO of 33.43:1. Take our new more accurate mass flow rate of 203 grams per minute of air and divide it by the air/fuel MASS RATIO of 33.43 units mass of air to 1 unit mass of hydrogen gas, and you have your fuel MASS flow rate of 6.07 grams per minute of hydrogen gas. Now think about this. How much volume does 6.07 grams of hydrogen take up? That's a pretty big f*cking balloon right? Again, we know through the ideal gas law that every gram of hydrogen gas at STP takes up 11.2 liters of space. That means at idle, this little 2,000cc engine will eat up 68 liters of hydrogen gas every minute, the volume 6.07 grams of hydrogen gas takes up. It's called a MASS (not volumetric) RATIO and that's how I get the volumetric flow rate of hydrogen gas per minute. That's a lot of soda bottles per minute!

To get how much water it takes to make all this hydrogen gas, we have to go back to chemistry and the Molar balance. For every gram of hydrogen gas to be produced through electrolysis of water (no matter how fast,) 9 grams of water has to break down just to generate the hydrogen gas, and since water has the density of 1cc per gram, feeding an appetite of 6.07 grams of hydrogen gas per minute will require 54.6cc of water to be electrolyzed per minute. (This is slightly less than the 63cc of water per minute I previously calculated.) If your car drank this much gasoline at idle, you'd have a different hobby.

I'd show you the calculations, but there aren't enough pages here in this section, so you're going to have to trust me, just like I said last time. -JC

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