Home Automotive Reference Engineering and Motorsports Maximum Boost

www.nellump.net September, 2002

Book Review: Maximum Boost by David Lane dlane@peabody.jhu.edu Corky Bell has been in the aftermarket turbo business since 1977 when he opened CarTech in Dallas, Texas (currently in San Antonio). Ten years later, a 42 year-old guy with a newish "85 GSL-SE and a bad case of mid-life crisis (yours truly) gave him a call inquiring about a turbo kit for the car. He sent me a set of instructions so I could get a feel for the difficulty of the job. After looking them over, I called back and said that the instructions seemed straight-forward and complete. Corky replied that I probably wouldn’t feel that way once I got into the project. He was right. The instructions were written for people with a little more mechanical experience than I possessed at the time, and I needed help with some basic concepts like how to reference left and right, and how to identify NPT fittings. By the time it was over, and I had generated $100.00 in phone bills to Texas, I learned that Corky and his associates were people of near-infinite patience. In fact, the interactions with Corky were one of the high points of the project.

Corky is like that. He is a hero of mine. But unlike other heroes like Pamela Anderson and Johnny Carson (people whose outstanding attributes are out of reach), Corky is accessible when I am trying to trouble-shoot a problem, or simply want to know what is hot in the aftermarket turbo business.

The instructions for the kit came with a document called "The Same Old 20 Questions" in which Corky gave straight forward answers to the things he was asked most. It may be a sign of the times, but the more recent versions of that document contain well over seventy questions and answers. "Maximum Boost" is a logical expansion of the same approach. The subtitle is "Designing, Testing and Installing Turbocharger Systems."

I first heard that Corky was working on a book several years ago, and knowing Corky’s technical background -- Bachelors degree in Mechanical Engineering, and 12 years with Bell Helicopter (no relation) -- I wondered if the book would be of any value to someone like me who went to a music conservatory and worked for 12 years as a high school band director. I sure didn’t want to wade through a thermodynamics text, and any math beyond the most basic algebra makes me twitch. It is a dilemma for any writer. The question is: Who is your target audience? Is it the person looking to upgrade a stock turbo system? Is it the guy who wants to create a VW dragster from scratch? Maybe it’s the lady who is confused by a bunch of conflicting claims for turbo and supercharger Miata kits?

Fortunately, Corky takes a multi-level approach to almost every subject. Going through the book, you will find general, plain English discussions. Just about the time you wonder if you really understand, a drawing or illustration clarifies what he is trying to say. He does not shy away from math, but it is not hard to follow the formulas. Besides, if you start to twitch, you are usually near a chart which will get you in the ball park for the answer. So, for instance, if you want to calculate the airflow rate of an engine (something you need to do to determine the size of the compressor) Corky takes you through the formula: Airflow Rate = [(cubic inch displacement x revolutions per minute x .5 x volumetric efficiency) / 1728]. Too complex? Okay, that means that a 302 Ford V-8 at 5500 rpm flows 408 cubic feet of air per minute. Hmm. So, what does that do for me if I have a Honda? Well, there is a graph from which I can pick my displacement and rpm, and get close to the flow rate for any four stroke engine.

The bad news for us rotary types is that there is hardly anything in the book specifically aimed at rotaries. However, all the principles are the same, and while the discussions are aimed at the piston crowd, the tips and suggestions are general in nature and thus valid for any engine. Another slight mis-match is that Corky does not emphasize twin turbo systems in the book. This makes sense because of the complexity of such installations, combined with the very small group of people who would actually try to fabricate such a system.

The multi-level approach extends to all aspects of the book. Each chapter starts with a general discussion which will be enlightening for those who have a curiosity about the subject at hand. This is followed by a simplified version of the engineering elements for those who need to make calculations and are seriously involved in a project. The end of each chapter contains the relevant questions and answers without any technical talk. Interspersed in all this are "Rules" which are usually in-your-face statements to sum things up. The chapter on intercoolers, for instance, starts with a general discussion of what they do and how they function, followed by very detailed information on how they are designed and built. This section is 23 pages of text and illustrations, including technical information on heat transfer area, internal flow area, internal volume, calculating power losses and flow losses, calculating efficiency, choosing types (air/air or air/water) and design/construction considerations for each. He even goes into tube sizes, bends, connecting hoses, water injection, and of course, placement. The chapter summary (in question and answer format) gets back to the non-technical basics with about 3 pages of: "What is an intercooler, and why is it of merit?"; "What configurations do intercoolers come in?"; "What is water injection, and when it needed?"

Interspersed in the chapter are the "Rules," including:

  • RULE: It is absolutely incorrect to think that "any intercooler is better than no intercooler."
  • RULE: The single most important aspect of intercooler design is low internal pressure loss.
  • RULE: When viewing intercooler designs, regard thick core layouts as less than well thought out.
  • RULE: A water injector on a turbo car is a poor-excuse band-aid for not doing the job correctly the first time.

    Needless to say, there are chapters on everything from Intake manifolds to exhaust systems, including a chapter on trouble shooting, and another with a look at the cutting edge of turbo design -- Corky’s take on the most likely future developments. Variable Area Turbine Nozzles (VATN) turbos may be the hot ticket before long. Air bearings for the turbo are unlikely, but ball bearings may come into play.

    In an effort to put all this information into a practical setting, Corky takes you -- step by step -- through the design, installation and testing of a turbo system on an Acura NSX. This is where the theory meets the manifold, so to speak, and provides a template for those who want to start from scratch. While racing applications are sometimes used as examples, this book is clearly aimed at those interested in streetable machinery. As such, the NSX gains 122 bhp (to 390), drops a second from its average 0-60 time (to 4.7 sec), and gets through the quarter mile one second faster (13.0) and 10 mph faster (111 mph). This is with pump gas, and all emissions equipment (including cats) in place. The system operates at about 5 psi, with the stock engine internals and fuel injection, aided by a boost dependent fuel pressure regulator.

    The last chapter is on installing a turbo kit--which, though it is not mentioned by name, looks like an illustrated version of the instructions for the CarTech Aerocharger Miata kit. If this is the case, Corky has come a long way in clarifying his instructions. It made me want to buy a Miata just for the fun of installing another kit. While I was tempted to gloss over this chapter, it served as a reminder of how much work goes into designing a good kit, leaving the shade tree mechanic with only some hopefully pleasant mechanical work to do in order to create a relatively unique vehicle.

    Maximum Boost hits its mark squarely. There is valuable information here for anyone who looks at a turbo system and wants to know more. It has been observed that the search for answers will most likely result in more questions, and Maximum Boost will take you wherever you want to go in that process -- even if you don’t know what questions to ask. The discussion goes from the very basics (don’t reuse lock washers) to the intricacies of A/R ratios.

    Finally, the book stays relevant to the real world of cars in the ’90s -- dealing with smog control, approval by state agencies, and even marketing concerns. One of my favorite sections deals with the design objectives of Porsche and Nissan, comparing the 1988 911 Turbo and the 300ZX Turbo -- two engines of similar size, weight and displacement. Corky notes that Porsche, with an air cooled engine (not very heat tolerant) went with a large turbo, accepting some "turbo lag" in favor of creating a powerful automobile. Nissan, with a much more heat tolerant (water cooled) engine, went with a small turbo for quick off-idle response. Nissan didn’t even include an intercooler in the system. Corky concludes that the companies had different buyers in mind, and that Nissan intentionally engineered a "0-30 mph performance car" to satisfy their intended market. Corky continues: Although the Porsche has been proclaimed by all its road testers the prime example of a high turbo-lag design, it had to be that way because of the low heat allowables. A small turbo could not have been used on the 911 because of the thermal restrictions of the air-cooled engine, and certainly not when serious power is an objective. Porsche, therefore, should be credited with doing a fine job. Nissan should be credited with selling a large number of cars to a large number of people.

  • RULE: Never send a child to do an adult’s job.

    Those of us with rotary turbos (stock, modified, or aftermarket) sometimes make costly mistakes by taking an unbalanced approach to modifying our cars ("I’ll open up the exhaust and intake this year, and then deal with increasing the available fuel next year"). Corky’s book, besides being generally fun and informative, provides all the answers you need to avoid disaster. But more than answers, it clearly outlines the questions you should be asking.