Intelligent Engine Modifications

8/18/2019 Intelligent Engine Modifications

1/6

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


2/6

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


3/6

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


4/6

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


5/6

-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


6/6

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

Documents

Intelligent Engine Modifications