CHAPTER TWELVE

TUNING THE ENGINE

TUNING THE ENGINE Falconer, Weiss, Stimola, et al. Any edge that you do
I n the chronological order of writing this book, this is the achieve-and you very well may achieve one-will be due to
last chapter to be done-because it is going to be the more meticulous assembly than a commercial shop can af-
easiest-and the shortest. There are two reasons. First, I ford, not to demon tweaks. As a case in point, a couple of
firmly believe that building the engine is the engine builder's years ago I did a Formula Atlantic season with Bobby
job and that, with the exception of adjusting mixture Brown. We had three Cosworth BDAs, one Brian Hart, one
strength and playing with the throttle response, track tuning Swindon and one assembled from a standard Cosworth kit.
of the engine is a waste of time. Second is the simple fact that The assembly and all of our rebuilds were done by Tony
there are already in print some really good books on engine Cicale in his garage at home (the garage is only slightly
building. They are: Racing Engine Preparation by Waddell cleaner than the average hospital operating room). All
Wilson and Steve Smith, published by Steve Smith machine work was farmed out. Once we caught on to a cou-
Autosports, P.O. Box 11631, Santa Ana, California 92711. ple of things that we were doing wrong (that March was the
Also published by Steve Smith is Racing the Small Block only race car in history with excessive cooling capacity and
Chevy by John Thawley. Mr. Thawley has written two other the BDA wants to run at 90°C to 100°C-and the Lucas
Chevy books, Hotrodding the Small Block Chevy and Opus ignition is NFG and tricky besides) we had no engine
Hotrodding the Big Block Chevy for the ubiquitous H. P. trouble and we had no power disadvantage-to anyone. We
Books. The best of the bunch is The Chevrolet Racing wound our engines as tight as anyone in their right mind and
Engine by Bill (Grumpy) Jenkins, published by S-A Design had absolute 900 to 1000 mile reliability-which was a lot
Company, 11801 E. Slausen, Santa Fe Springs, California more than many people could say. This was a case of a truly
90670. Every racer should own at least the first and the last meticulous craftsman building engines strictly by the book
of the above. Even if you do not and never will race stock and getting results as good as anyone's.
block Y-8s, the general information is applicable to any in- Racing engine preparation consists of buying the best
ternal combustion engine and it is priceless. components and assembling them meticulously. Let
So far as the building of the racing engine goes, there are somebody else play with hydraulic/pneumatic valve actua-
two basic choices-a top end engine which will produce a tion, short stroke or long rod engines, trick oils and the like.
whole bunch of horsepower at high rpm at the expense of the There are lots of people out there who prefer tinkering to
width of the torque band and mid-range power, or a torquey winning-it gives them a good excuse.
engine which sacrifices some of the top end to gain mid- With your Cosworth DFY Formula One engine you get
range power and a broad usable rpm range. Admittedly the three fuel metering unit cams-standard, Kyalami and Mex-·
horsepower and torque curve characteristics required will ico. You also get a seven-page instruction sheet, a twenty-
vary somewhat with the nature of the race track, but the page parts list and ten pages of engineering drawings that
basic rule remains, "Horsepower sells motorcars and torque cover everything from the basic engine shape and dimensions
wins motor races." to the recommended oil, water and fuel systems, and the ex-
Our basic job with the racing engine is to make sure that haust system layout (they supply the intake system). They go
we don't lose any of the power that the builder put into it so far as to tell you, in detail, how to start and warm up the
when we bolt the thing into the chassis. All that this requires engine. They also supply a maintenance and running log
is making sure that the engine is supplied with enough of the which stays with the engine and is filled in in the field by the
coolest available inlet air and the requisite amount of fuel, race team and in the workshop by Cosworth. You are in-
that we are running the exhaust and inlet systems that the formed, again in detail, how to time the engine, install a new
engine builder had in mind, that we are not either abusing metering unit and distributor and they tell you to do none of
the engine or robbing ourselves of power with an inefficient the above except in cases of extreme emergency. Would that
cooling or lubrication system and that the ignition system other engine suppliers would do the same.
works. I covered most of those areas rather thoroughly in There are, however, areas where we can gain real perfor-
Prepare to Win. mance by tuning. These areas include the inlet system, the
If you believe that you, personally, are going to tune on cooling system, the lubrication system, the ignition system
your engine and blow off the opposition, you are wrong! This and the exhaust system. We will not discuss the lubrication
does not mean that you cannot build and/or maintain your system because I said all that I have to say in that area in
own engine and be fully competitive-you can. But it is Prepare to Win. For now, I will say only that we can lose a
highly unlikely that you are going to get an edge by out- lot of power by running the water and/or oil too cold-we
engineering or out-tuning Cosworth, Hart, McLaren, typically want about 90°C on each. We covered the

140
mechanics of cooling in Chapter Nine. We also covered the lot of cornering power. The recommended float level setting
air end of the inlet system in Chapter Nine. are invariably too high. When you drop the float levels i}
you drop them much, you are going to have to increase the
CARBURETION (OR INJECTION)
volume of fU~1 that pass~s throu~h the float valves when they
There is an old saying in racing that, "you've got to be are open-either by gomg to bigger float jets or to higher
lean to be mean." It is true. Most racers run their engines far fuel pressure-or both. With Holleys and the like you also
too rich-to the obvious detriment of power and fuel con- get t? play with the. progression on the secondary butterfly
sumption and, more important, to the less obvious detriment opemng. Holleys Will not run on a race car without slosh
of the all-important throttle response. tubes-on both ends. I dislike stock carburetors. In fact I
There is a simple and very valid reason for this practice- dislike carburetors, period. Injection is so simple and so ~f­
if you run a little too rich you lose some power and use a lit- ficient ...
tle more fuel. If you run a little too lean, you burn a piston,
IGNITION
are out of the race and get to do an expensive rebuild. Spark
plugs and exhaust tubes have two purposes-one to ignite Next comes ignition. If there is a good racing ignition I
the mixture and to conduct the exhaust gases, and one to tell haven't found it-but I'm still looking. My favorite-the
you how your mixture is. The trouble is, you've got to be Vertex Magneto, reworked by Cirello or Cotton offers two
able to read the damned things and no books or series of notable advantages-only one wire is required and it is easy
photos can tell you-you've got to learn from someone who to trouble shoot-either it works or it doesn't. Like all the
knows. The tail pipe, however, requires very little experience rest it is prone to sudden and inexplicable failure. Some
to read- it just takes a lot of faith to believe. I firmly believe wondrous failure modes have been experienced-doesn't
that if the tail pipe is black (assuming a plug cut, or even a work on the track and checks out fine in the shop, for in-
normal pit entrance) you are too rich. If it is snowy white, stance. A lot of trouble can be avoided by making sure that
you are too lean. It should be somewhere between light grey the stupid thing doesn't overheat-which means yet another
and white. Unlike plugs, the tail pipe doesn't tell all-but cooling duct.
only a part of the story-and you wouldn't want to use it If the rpm limit will permit it (7500 max), you probably
exclusively-but if it's black you are wasting power. Once can't do better than a standard Mallory racing or Delco coil
you learn how to read plugs, there is little sense in making a and contact breaker system.
ritual of it. Do plug cuts until you get the mixture right and All Cosworth and Cosworth-derived engines come with
then stop playing with it. the Lucas electronic Opus ignition system and its justifiably
The power end is only part of the mixture question. The dreaded black box. The black box is supplied with a quick
other part is throttle response. I'm not going to attempt to release mount which is telling us something immediately.
write a carburetion or injection manual but I cannot Again, if the box is cooled sufficiently-and shock
overemphasize the importance of throttle response-and it mounted-reliability is increased to the just barely accept-
comes from the idle and progression circuits plus float level able level. Actually a good part of the trouble with the Opus
on carburetors and the idle end of the fuel control cam with comes from the cheap nasty distributor, not the electronics
injectors and NOBODY worries about any of the above- as such. There is a super trick Formula Two distributor, but
except the guys who do all the winning. How many times it is not available to the likes of you and me. About a century
have you heard, "No, I don't bother getting the butterflies ago, when I was running the Coventry Climax Fire Pump
synched or the intakes balanced at idle, because full throttle Engine in "G Modified," I got tired of having the distributor
is all that matters."? The driver who waits for the engine to fall apart-so I made one-hogged the case from a billet,
clean itself out when he gets on the power is the driver who made a shaft, from some standard thing or other, used the
loses. He is also the driver who isn't going to have a lot of Climax gear, a US cap, rotor and cam, locked the ad-
success at steering the car with the throttle. The amount of vance and used real bearings. It took forever and solved the
fuel that an engine needs at idle is just enough to keep the fire problem-also forever. If I were running a Cosworth, I
from going out and NO MORE. Probably the major cause think that I would take the time to make up my own dis-
of bad throttle response on corner exit is too rich an idle mix- tributor and would run it off the exhaust cam rather than the
ture, which loads up the whole system during the overrun. jackshaft-at least that way I'd be able to see the damned
When the time comes to apply the power, the engine has to thing-even take the cap off if I were so inclined.
cough out the raw fuel that has accumulated before things Speaking of distributor advance, I haven't yet figured out
can get going again. This is the familiar cough stutter syn- why we run any in most of our engines. The advance is all in
drome, which can also be caused by too high a float level. by 3500 or 4000 rpm so it doesn't affect the operating range
How lean you can go at idle is demonstrated by listening to and it's one more thing to go wrong. The usual reason given
the Formula One brigade on the overrun. All you hear is is that we have to retard the engine for starting but I have
crack, snap and pop due to leanness. There is next to no run everything from Turbo Fords, 510 Chevys, small block
load, so you can get away with it. With injection, you merely Chevys and Cosworth BDAs locked out and they all started
lean down the idle-although you may find that you need a fine.
different fuel control cam. With carburetors it is a question Racers don't pay as much attention to high tension wires
of the leanest idle jets that will run and playing with fuel as they should. Again, I made most of my recommendations
pump jets and cams, emulsion tubes, progression holes and in Prepare to Win and nothing has changed-except that
float levels. Don't forget that all carburetors, including people have started to run all of the plug leads in a bundle.
Webers, were designed in the days when 0.8 g was a hell of a You can't get away with that-no matter how good the HT

141
 on a given race track. There are two theories-gear for the
600 corners and gear for efficient acceleration. Neither is totally
0 correct.
0 0
,....
0> 0 In order to gear the car intelligently and quickly we need a
550 C')
CD
few simple things. First of all we need a driver who can and
will read the tachometer and remember what he saw long
500 enough to tell the Man in Charge. Next we need some sort of
reasonable course map to ensure that the driver and the Man
in Charge are talking about the same part of the race track.
450 We will also require a set of engine torque and BHP curves
like the ones in Figure (89) and a gear ratio vs rpm and mph
chart like Figure (90). Usually you will have to make your
400 own gear chart because the commercially available ones are
for the wrong tire diameters. We do not need a computer.
Looking at the engine power curves with a view toward
gearing, a couple of things become immediately evident.
First is the fact that, on any given race track, we want our
maximum rpm in top gear to coincide with the maximum
300 LL....J_....J._~"':'""""":~~~-'::::J::::--=:::::--~;;-";;-;:'
4000 4500 BHP of the engine-as installed. If we don't reach that rpm
because we are geared too short, we will give horsepower
away and will lose both top speed and lap time. If we exceed
Figure (89a):Typical5 litre BHP and torque curves. the rpm by much, we will sacrifice horsepower again with the
same result. In road racing I don't much worry about the ef-
fect of a possible "tow" in top gear as the engines are always
wire that you are using may be. To avoid the danger of in- safe for several hundred rpm above max power, tows are a
duction tiring between cylinders which are next to each other sometime thing, and if you are getting a tow, you don't need
in firing order, the HT leads must be separated-even if it the horsepower and so can afford to over-rev a bit.
means running one lead down the intake valley. We do not, however, wish to shift at the maximum power
One of the race track activities that confuses me a lot is rpm. Again looking at the BHP curve of Figure (89a), sup-
the constant checking of the ignition timing. I've had the pose that we will drop 1500 rpm when we shift. Ifwe shift at
timing slip on me exactly once and, as you would suspect, the
clamp bolt was loose. Timing should be set on the dyno,
checked when the engine is installed (like with a buzzer)-so
the power peak, or 7900 rpm, then the engine will drop back
to 6400. Draw a vertical line down the chart at those two
rpm points. The area enclosed under the BHP curve between
I
that you know where it is in case the distributor has to be
\

,
replaced-and then left alone. If you don't trust your engine
builder to time your engine, you need another engine builder. 225 I
THE EXHAUST SYSTEM
Developing an efficient exhaust system is a teal pain-it is 200
I ~
V
II
also a job for an engine builder with access to a dyno. Both

I V
Jenkins and Wilson get into exhaust systems in depth. Un-
fortunately there is real power lurking in the exhaust system
of the racing engine and a bad one can choke your engine to
175
~ I
an amazing extent. So consult your engine builder-or copy /
the hot dogs-and build what you need. Although Prepare
to Win outlined the easy way, it will still be no fun at all. 150
/ I
GEARING
I do not understand the agonies that racers go through
over gearing their cars to the race track-it just isn't that 125
~-... -- TORQUE
-.....
difficult.
The only good explanation of optimum gear ratio theory I
r'\
have seen in print is in Chapter Nine of Paul Van Valken-
burgh's Race Car Engineering and Mechanics. If you don't 100
have the book, you should, so I am not going to duplicate
Paul's efforts.
The whole purpose of multi-speed gearboxes is to provide
variations in torque multiplication so that the engine can be
a
6000 6500 7000 7500 8000 8500 9000 9500
kept within its range of efficient rpm as road speed
increases-the idea is to select the ratios that will provide Figure (89b): Typical 1.6 litre BHP and torque
the most acceleration over the speed range of a given vehicle curves.
142
 50 60 70 80 90 100 110 120 130 140 .__ .__ .. v .__ .vv _v

9000 1 I I I I r 7 II 7 } I J L j 7 _] 7 :a > i > > I I :> I Ii D > i >

85001 I I II I I I 11 / / I/. / /I / /1 / / I / A /" Y / 1/ -----,.L+-----,.£ 1/

MAX rpm

8000 I I I I II /I / / l / § II / / V / fi ; IY /' V , IV / I / % / I '8000

MAX POWER

7500 I I II I rI I rI rI Y jI rI l- / AI J, rI I7 I ~
- Ir I " I7 ' "§ V /' II § /1 / I I 17500

70001 I I 1/ / II I I ' 'II / /1/; V / I§ / I / I I I 17000

~
w 65001 1I I I I / / 1/ / I V / / 1/ / V / A/,' V / V / V 1 I 1 I 6500

60001 I 1/ / A/ / /1/ / Y / / IJ / k /' 'Y / § / 7f I 1 I 1 I 16000

Figure (90): Gear chart Hew/and DG 300: 9131 ring & pinion
27.0" tire diam.
mph = (.01136) (rpm) (tire circum. in feet)
(gear ratio) (ring & pinion ratio)

.
60 70 80 90 100 110 120 130 140 200

mph
 the two lines is porportional to the total power that we will
have available to accelerate us from 6400 rpm to 7900 rpm in
the gear that we have just shifted into. If, on the other hand,
we do not shift until 8300 rpm (assuming that the engine is
safe to 8300), the rpm will drop to 6800. Although the
horsepower has dropped off on the top end from 7900 to III
8300, there is more area under the portion of the curve from
6800 to 8300 than there is under the portion from 6400 to
7900 and we have gained acceleration. So we have to select
our shift rpm for maximum area under the BHP curve. The Figure (91): Riverside-2.54 mile short course.
actual shift point will vary with the nature of the curve, the
step between the adjacent gears and the safe limit of engine going to shift at 8200. We look at the gearchart for
operation. It can be found with a .:alculator or by eyeballing reasonable steps and, on a decreasing step basis, select a
the curves and gearchart. It is of some importance to make 24/33 third gear and a 25/30 fourth. Shifting from second to
sure that your tach is accurate-most are not. third will drop the rpm to 6400 at 109 mph, third to fourth
The next thing that we have to worry about is the selection will drop to 7100 at 138 mph and fourth to fifth will drop to
of the optimum ratio for the shortest (slowest or numerically 7300 at 159 mph. On the course map these look reasonable.
highest) gear that we are going to use on the race track in For a perfect progression we might have chosen a 26/30
question. If we are going to be traction limited (i.e., if the fourth gear, but that looks as though it might be a bit tall to
corner is slow enough that wheelspin will be a problem) then get a good shot out of Turn Nine, so we opt for the 25/30 for
we select the longest gear that will (a) keep us just at the openers.
wheels pin limit, and (b) keep the rpm at the slowest point in This selection can be labelled "guess one." While they will
the corner high enough that the engine will pick up the throt- give us pretty close to ideal acceleration, we may have to
tle cleanly and accelerate smoothly. Don't worry about rpm modify the gears to suit the race track rather than the drag
in relation to the peak of the torque curve at the slow point in strip. For instance, we have selected our low gear (second in
the corner-we want the torque peak to coincide with the this case, since first is a "never-to-be-used gear" in Formula
rpm at which the driver can bury his foot-not the point at 5000) on the basis of the slowest corner on the track.
which he picks up the throttle. It makes no sense at all to in- However, there may be several other second gear corners
stall so short a gear that the driver will be faced with an em- which are faster than the slowest one. In this case, we may
barrassment of riches in the torque department. We want the have to use a taller second for the greater good. Or we may
car to be traction limited when he nails it-but only just. find that third is too short for one of the lesser straights_
Remember, the taller that we can make bottom gear without necessitating a momentary shift into fourth just before we
sacrificing acceleration, the closer we are going to be able to get on the brakes for a second or third gear corner. In this
space the remaining intermediate gears and the greater will case we install a taller third. And so on-unless you are run-
be our overall acceleration potential. At the same time ning something like the old 510 C.LD. Can Am Cars with so
remember that he is also going to have to pull out of that much torque that, except for low and top it didn't much mat-
same corner with a full load of fuel. If we are not traction ter what gear you were in, the selection of optimum ratios is
limited, select a low gear that will allow the driver to apply going to take a bit of fiddling. The peakier your engine is, the
full power at or very close to the engine's torque peak rpm. more critical the gearing will be. Do not, however, expect
Now we have to select the intermediate gears. Many great gobs of lap time to result from changing gear ratios-.·
racers choose intermediate gears in even steps from bottom it will not. What will happen is that the car will become more
through top. They are wrong. For maximum acceleration we pleasant to drive.
want the steps between gears to get smaller as road speed in- The two most common mistakes that racers make with
creases. The reason is simply the big wall of air that we are respect to gearing is running too short a low gear and
pushing at high speed. A quick return to Figure (45) will il- twisting the engine too tight. In both cases the driver is
lustrate what we are talking about. We can stand a big jump probably confusing noise with power and wheelspin with
from first to second because the total resistance to accelera- forward bite. Another common failing on the driver's part is
tion at that road speed is low. By the time we are ready to not gearing the car so that it is well within the peak torque
shift from fourth to fifth, we need all of the area under the range coming out of critical corners in the intermediate
curve we can get and so the step from fourth to fifth has to be gears. A dead giveaway to this one is the answer, "Oh, it's
small so that we will have maximum power available after pulling OK," when asked about his rpm coming off from
the shift. Again the selection can be made with a turn whatever. It will pay dividends to sit down with the
calculator-or you can draw a bunch of graphs similar to driver and the charts and have a ten minute chat about gear
those in Figure (45). You will come just about as close by ratios.
eyeball. Supposing, for instance that we are gearing a For-
mula 5000 car for the short course at Riverside (Figure 91). MATERIALS
We know from previous experience that we can pull a 27/29
top gear and that a 20/35 second is just about right for turns At the moment the racer has very little, if any, choice with
six and seven. If we did not know, we would have to guess respect to the materials from which the components of his
from experience at other tracks and a course map. Our peak engine will be made. About the biggest decision that we get
torque is at 5500 rpm, peak horsepower is at 7900 and we are to make is whether to use aluminum or magnesium for the

144
water pump housing-and that only on stock blocks. Very general chicanery during which a lot of substandard parts
soon this situation will change. The technology of composite which mayor may not be made from the right composites
materials is about to catch up with motor racing. The com- will appear on the market. Until the manufacturers and the
posites of which I speak are man grown thin filaments of racers figure out the technology involved, there are going to
either pure carbon or pure boron. The filaments are then be som~ broken parts. I haven't exactly figured out what I
combined or woven into various forms, saturated with very am gomg to do when composites become available-
tricky epoxy resins and formed into sheets or shapes under ~robably buy some pa~ts, have them analyzed and destruc-
both temperature and pressure. The resuling parts boast tIOn tested-so I am m no position to offer advice. I will
strength to weight and stiffness to weight ratios well beyond suggest, however, that the initial advertising claims be
anything that we know about. They are temperature stable treated with the usual grain of salt.
and can be made machinable. The costs of both materials Believe it or not, that's all that I have to say on the subject
and tooling are very high but are declining slowly as com- of tuning on the engine.
posites come into more general use. If all this sounds like I don't believe in tuning the engine at
While composites are eminently suited for such applica- the track-it should. The poor little devil has to be constant-
tions as brake discs, hub carriers and wheels, it seems ly checked and the mixture may have to be adjusted for the
probable that their first use in racing will be in engine day and the altitude, but that's it. Oh, yes, one other thing:
components-connecting rods, rocker arms, valve spring Bounding around on the trailer is very liable to upset the
retainers, push rods and pistons come to mind. Except for the float level, so that has to be checked as well. You are not go-
cost aspect there is no reason why blocks and cylinder heads ing to find another 20% power by dickering with the engine
cannot be made from composites. I foresee a golden age of at the race track-in fact you won't find any and you are
very strong, rigid and light race car parts-which will be a very liable to lose some. So concentrate your time and
comparative advantage to those brave enough to use them energy on the chassis and aerodynamic balance. As Jim
first. Travers used to say, "Tune your chassis and gain 100
I also foresee a short period of ignorance, hype and horsepower. "

145