Intelligent Engine Modifications
Transcript of Intelligent Engine Modifications
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Intelligent Engine Modifcations
With so much misinformation and BS out there in the performance aftermarket
world, we have decided to oer the reader some real tips based on 20 years of
performance engine building and turbocharging experience
Street or Race?
!his is probably the biggest "uestion related to successful mods and the most often
ignored #any people $ust don%t understand why you can%t drive a race spec engine
on the street &et%s examine the dierences in the 2 dierent worlds'
Street
( good street engine should have a smooth idle, have lots of low end tor"ue, a wide
powerband, long life and good fuel economy !o get these characteristics, most
street engines have relatively moderate camshaft timing, small turbos, small
diameter intake ports with long runners and usually cast pistons !hey are designedto run on gasoline with an octane rating of )* to +2 -. in most cases and usually
produce less than /00 hpliter in naturally aspirated form and /20 hpliter in
turbocharged form
Race
1deally, a good race engine should have all of the same characteristics that the
street engine has above but since high power output is one of the primary concerns,
many compromises in those other desirable traits must be made to achieve this
power level !o achieve higher power, ports are opened up for increased ow at high
rpm and camshaft timing and lifts are increased, both of which kill o low rpmtor"ue, power, fuel economy and that smooth idle
!he rpm capabilities are upped to permit higher airow rates !his is usually done
by changing to stronger parts such as connecting rods, pistons, crankshafts and
valve springs 1f the engine is turbocharged, a larger turbo and intercooler along
with forged pistons and stronger rods are 3tted to handle the loads aising the
redline will not make any more power in most cases unless the engine components
are modi3ed to e4ciently pass that increased airow
-n naturally aspirated engines, the compression ratio is often raised substantially to
boost tor"ue and power !his is possible when using high octane race fuel -n turboengines, the compression ratio may either be raised or lowered depending upon fuel
octane allowed, maximum boost pressure and possible fuel limits for the race
(s you can see, the two engines vary considerably in re"uirements and execution
!he problem comes in when someone wishes to increase the power output of a
street driven engine beyond reasonable limits while expecting no ma$or degradation
in 5streetable5 "ualities
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Naturally Aspirated Engines or the Street
-n atmo engines for street use, there are only a few ways to substantially increase
airow and thus power
6orting the head will improve airow if done correctly 1f the ports and runners are
enlarged greatly, low speed tor"ue will suer considerably
7igher duration and lift cams are the main modi3cation for increasing power !he
more duration and valve overlap a cam has generally, the worse the low end tor"ue,
fuel economy and idle will be -f course, top end power should be better -n most 8
cylinder engines, going with more than 2)9 degrees of duration at 0 lift will result in
truly gutless bottom end power With too much cam, the eective powerband
becomes so narrow that the car is $ust plain miserable to drive in tra4c #ost street
engines spend the ma$ority of their time in the 2000:8900 rpm range ;ngines
which are heavily cammed may not begin to produce substantial gains until above
8900 rpm and you are paying for this +9< of the time while being able to en$oy that
top end only 9< of the time We see more problems and complaints with people
3tting race type cams in street type engines 1t makes the ;=1 hard to tune and the
car annoying to drive in many cases Don't overcam
1ncreasing the compression ratio is another way to increase power 1t also increases
fuel mileage >nfortunately, the pump fuel available in most areas limits the
compression ratio useable on the street to under /09 to / on most engines !he
dierence in power is minimal going from say + to /09 to / and it is a lot of work to
shave the head or install new pistons (gain, if you get stupid and try to run an /2
to / ? on +2 octane fuel, you will suer with lots of pinging and eventual failure
#any high compression street engines must have their timing severely retarded toavoid detonation which reduces the power right back to stock levels Don't raise
the compression ratio too high
aising the redline to achieve higher airow through the engine is another way of
increasing power !o do this eectively, you will likely need to install a hotter cam
with stier valve springs, port the head and possibly install stronger bottom end
parts like connecting rods !he factory redline is there for a reason 1f you exceed it
repeatedly by a large margin, you may eventually have a catastrophic failure
1nstalling a header and free owing exhaust along with a cold air induction system
may free up a few more hp on certain engines @on%t expect gains of over /0< withthese mods on most engines
.itrous oxide in$ection is used "uite extensively in drag racing for a substantial
power gain When adding large amounts of nitrous, engine components may have
to be upgraded to withstand the higher pressures involved !his is not usually a
great mod for street use as everything must be $ust right as far as fuel and nitrous
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ow goes and of course the ma$or disadvantage is that the tank runs dry after only
a few minutes of use and must be re3lled
!onclusion
-n street driven atmo engines, there are minimal gains to be had on most small
engines without sacri3cing a lot of driveability 1f you need more power, you need a
larger engine usually ;xpecting your /) second car to do /A seconds while
retaining good idle and fuel economy when modi3ed is unrealistic most of the time
"ur#ocharged Engines or the Street
!urbos are a dierent ball of wax but many of the same mistakes are made when
modifying them #ost of the same power increasing methods from above can also
be applied to turbo engines Because turbo engines usually have lower compression
ratios than atmo engines, they do not take kindly to hot cams on the street !he
gain in top end will almost always be oset by a huge loss in the lower powerband
and more turbo lag Stock cams are the way to go on most turbo street engines
@on%t waste your money on so called 5turbo cams5 for 8 and cylinder engines
!hese may boost economy slightly but they almost always lose power #ost of these
were designed by guesswork rather than by actual turbo experience 8 Calve
engines in general when turbocharged do not need hotter cams for the street
6orting a turbo head will make the same type of gains as on an atmo head despite
what some people say Dou can make the same power with less boost or more power
with the same boost
!o obtain higher than stock outputs, the compression ratio should be $%&ERED on
a street turbo !his will permit higher boost with optimiEed timing on low octane
fuel =orged pistons are an excellent idea on turbos as they have 2:A times the
strength and heat dissipation of cast pistons =orged connecting rods, colder spark
plugs and stronger head gaskets are also recommended
Stock turbos are usually siEed for mid range tor"ue and are undersiEed even for
stock top end power ?ompressor and turbine siEe upgrades are needed to realiEe
substantial power gains Foing too large on turbos will lead to poor low end
response !urbos need to be properly matched for the application and primary
intended usage ( couple of rules of thumb can be used if you have access to a
compressor map 76 G /2 H airow in ?=#, 76 divided by )0* H airow in
lbsmin (void matching for e4ciencies of under 9< at full power and operation
near the surge line also
1ntercooling is extremely important Stock intercoolers with a few exceptions are
total crap when used for performance applications!hey oer low e4ciencies and
high pressure drop 1nstall a properly matched core from Spearco !he closer that
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your charge temperature is to the ambient temperature, the higher the 76 potential
will be
=inally, boost pressures can be raised to increase engine airow and power !his can
only be done within the limitations of the fuel octane rating and ignition timing
ead the other tech articles relating to combustion and fuel for a betterunderstanding 1n any case, running 20 psi on the street is relatively meaningless
7igh boost pressure does not necessarily mean high 76 1f you are running this kind
of boost on the street, you probably have a host of mismatched or restrictive parts
on your engine With properly matched components and an e4cient intercooler, one
rarely needs to exceed /9 psi on the street With these in place, you will be at the
safe mechanical limits of most stock based engines and 76 will be doubled or tripled
over stock ?heck out some of the cars on our pro$ect page prepared at acetech if
you don%t believe this Since engine life will plummet once you exceed this type of
output, it is not a viable option for most people to be rebuilding an engine every
/0,000 miles Dou don%t have a streetable engine in my opinion at this point
!onclusion
6ower may be increased substantially through turbocharging on the street but
reliability will suer unless it is applied correctly
"ur#o Race Engines
1 will use a !oyota 2!? engine which 1 prepared for road racing use a few years ago
as an example of what can be done with properly applied engine modi3cations and
turbocharging !he stock engine starts out as a /9))cc, 2 valve per cylinder,
pushrod, crossow hemi !he stock hp is rated at *0 at 000 rpm
!he block was bored out from )9mm to ))mm to 3t #ahle CW forged pistons !his
mod brings the displacement out to /*02cc and drops the compression ratio from
) to *2 to / !he rest of the block is totally stock as is the crankshaft
!he connecting rods were polished and shotpeened !hey were converted to a full
oating pin arrangement to suit the new pistons and =ord S6S big block bolts were
3tted to withstand the higher anticipated rpms
!he camshaft selected was the same cam we used on our race atmo 2! engines
with 8A0 valve lift 2)8222 degrees duration at 0 and 090 lift respectively on /0)
degree lobe centers Calves were enlarged from 8/ to 889mm on the intake via=ord cylinder ones and from A to A)mm via .issan 200SG ones !he head was
extensively ported on the ow bench taking intake ow from )2 to /22 cfm and the
exhaust from to ) cfm Calve guides were shortened and bronEe bushed for
increased ow and heat dissipation ;xhaust seats were widened to 0)0 for better
heat transfer .orris triple valve springs and aluminum retainers were also used
( stock oil pump was used and an 7IS /mm metal head gasket was 3tted
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-n the externalsJ ( custom, e"ual length header was made using /29 inch 1@
thick walled tubing , a custom intake manifold was made 3tted with a *0mm
#ercedes throttle body and eight Bosch 8+0cc in$ectors !he turbo was a Farrett
!-8 with 7:A compressor and a 9) turbine !his blew through a massive Spearco
intercooler measuring /* G 2/ G A inches and 29 inch mandrel bent tubing !he
exhaust was A inch mandrel bent tubing open =uel was #:)9
!his engine produced A9)hp at **00 rpm at only /9 psi boost !he stock hp was
"uintupledK ;ngine life was approximately hours at this power level and about /9
hours at /2 psi and A/0hp ;ventually, the main bearing caps cracked from the
power output but this was caught before ma$or damage occurred !he eective
powerband was 9000 up edline was limited to **00 rpm mainly for valvetrain
longevity although hp was still increasing at this point !his engine was used for
road racing so the life expectancy had to be about a full season or /9 hours
!onclusion
!urbocharged race engines can produce staggering hp numbers given strong
enough parts however engine life goes down as power is increased ( narrow
powerband may be acceptable on a race engine because close ratio gearboxes are
usually 3tted to minimiEe rpm drop between shifts
!here seems to be two types of people preparing turbo race engines for import drag
racing -ne school uses small, stock based turbos for "uick spool up !hese engines
run super high boost but don%t make any power School two 3ts turbos which are
way too large !hese have poor turbo response and a super narrow powerband
!hey produce very high hp across only /000 rpm on the top end and as a result are
not very "uick Bigger turbos don%t necessarily mean "uicker times !urbos must beproperly matched on the compressor as well as the turbine end
Some people really know what they are doing and some don%t 890 hp out of a /
valve /+00cc (cura drag motor at 29 psi is $ust not impressive when years ago Lack
oush was producing in excess of *00 hp out of ) valve 2A and 29 liter =ord 6into
engines for road racing events running from 2 to 28 hours
Engine Displacement
=or street use, you want as many cubic inches as you can get !or"ue on the street
is king (lways go for as many cubes as you can if you have a choice of engines
erormance E(I !onsiderations
When increasing airow through your engine for more power, you must also
increase fuel ow to match (t some point, the stock in$ectors and possibly fuel
pump will not supply enough fuel &arger in$ectors will have to be 3tted (s soon as
you do this with the stock ;?>, the engine will no longer run properly Dou will have
to either rechip or install a dierent ;=1 system
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1f your engine uses a vane type airow meter, you are losing a substantial amount
of power potential through its restriction 1t is foolish to spend a lot of time and
money improving engine airow, then strangling it with a door type meter on the
front ;ngines 3tted with this type of meter will usually gain at least /0< when
changed to a large hot wire or speeddensity type system 1t is important to note
that when the airow ap bottoms out at high airow rates, it is no longer capableof sending a proper signal to the ;?> !he fuel mixture will no longer be correct
Some companies oer rising rate fuel pressure regulators with their turbo kits to
allow increased in$ector ow rate over stock pressure 1nstead of adding / psi of fuel
pressure per psi of boost as in a conventional =6, they will ramp up at 2:9 psi per
psi of boost Some of these work -I at low boost but the fuel delivery curve is now
in the hands of a mechanical device, not the ;?> !his is crude at best 1t takes 8
times the fuel pressure to double the fuel ow 1f your stock fuel pressure is 89 psi,
you will need /)0 psi to double your fuel ow
!wo things happen here =irst, many in$ectors become non:linear in fuel deliveryabove 0:*0 psi dierential or may not even open, leading to a possible lean out
condition under boost Secondly, the fuel pump is not designed to do this 1t either
can%t produce the pressure or volume needed or will burn out "uickly due to the
massive increase in current draw !hese are a bad idea at high boost pressures
!onclusion
>se the right tool for the $ob Dou don%t normally use pliers to turn a screw in 1t
works, but not well !he same thing goes for performance ;=1 applications Sure,
you can trick an old &:Letronic system with a resistor on the water temp input and
get some more fuel out of the system but the method has serious limitations past apoint and will not really supply the correct mixture across the operating range
7opefully 1 have touched on some of the ma$or points here and saved you some
money and time on your pro$ect