NA power increases

[Terminator]

As a TT owner I know little of the costs of increasing power on an NA. What are the usual mods approx cost and power gain.

 

How far can you go with power without a major rebuid or going single?

[Whitesupraboy2]

A list i composed as i like my car so will prob be different and go NA mod route:

Exhaust

De-Cat

Cams

TOMS ECU (exspensive i think)

Pulleys

Custom cold air intake (with dry ice cooling)

ported & Polished Head

iriduim plugs

Uprated Plug leads

Extra earthing grounding kit

electric fans isntead of Viscous

Weight saving (rear seats out, spare wheel out, tools out)

Lightened Flywheel

NOS

 

Prob more i have forgotten

[Chris Wilson]

I post this article "wot I wrote" every now and again. Not Supra specific, it was actually penned for someone with a 2 litre 4 cylinder 16 valve engined car, but it's totally relevant to any modern 4 valve per cylinder engine.

 

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Post the early eighties,more and more manufacturers went to electronic

management of ignition and fuel,via fuel injection,and mapped ignition

systems. Most fuel injection systems had one immediate impact. They no

longer need a restrictive venturi (narrow throat) in the carburettor

(s) to pull fuel out of the fuel bowl of the carb. Fuel injection

*injected* the fuel under high or very high pressure. No restriction as

such,and hence less of a power loss. Management of the ignition and

fuel suddenly meant engines could get away with running camshafts with

greater overlap,and higher lift,too. The old advance weight disi,and

velocity sensitive carb limited what cam profile could remain

driveable, without hesitations,poor low end performance and flat

spots. To a large extent electronic management allowed much more

freedom in valve sizes,port shapes,and cam timing,as well as running

the engine at the best amount of ignition advance at all loads and

RPM's without detonation,on differing fuel qualities,via knock sensor

technology.

 

What I am slowly getting at is that it is *much* harder to get

anything like a useful power gain from a modern,well designed,16 valve

production engine on electronic management. The exhausts are free

flowing,as are the intake systems. One needs to look at further

performance optimisation of the cam profiles,and maybe bigger

valves,stronger valve springs,moves away from hydraulic valve lifters

and mechanical improvements to make higher revs safe,from a

mechanical stress related point of view. Almost any change that has the

potential for a marked improvement in power and torque,will require

different fuel curves (the amount of fuel injected at any one set of

parameters of air flow,temperature,engine RPM etcetera,etcetera),and

different timing curves. One can fudge the fuel,*across the whole

curve*,by increasing fuel pressure via an "up rated" fuel pressure

regulator,but the the weeks of dyno testing to get the fuelling

correct at every point,has then gone to pot ... :-(

 

As for the ignition,there is very little indeed you can do to change

the curve incrementally. Unfortunately,the *correct* answer is an

aftermarket injection system,or at least an aftermarket ECU and

wiring,that allows one to map the curves afresh,to suit your new power

modifications. This is expensive,both in terms of hardware,(maybe over

£1000 for the ECU and wiring loom),plus a lot of professional engine

dyno time to get it all mapped correctly.

 

Sometimes one can buy a complete package,say new cams,different

throttle bodies and manifold,etcetera,that can come complete either

with a modified EPROM for the existing ECU,or an aftermarket mappable

ECU complete. If one limits mods to exactly those which the kit

manufacturer intended,this should work well. If you change any

parameter from the tuners package,the early comments about incorrect

curves again apply..

 

Changing the exhaust *system* or the air filter,on 90% of modern

engines will do sod all.The mags claim this and that,but in reality a

gain of 5 HP on a 120 HP engine is neither here nor there,for a road

car. Humidity variations can see that much change. A rolling road is

hard pressed to accurately repeat to 5 BHP on a figure of 120 HP

total. To get greater gains,say 20 HP,you need to look at fairly

dramatic alterations,both to the mechanical components,and their

related fuelling and ignition curves.

 

Turbo engines are a slightly different kettle of fish,as it is trivial

to raise the boost,and usually to fudge some additional fuelling.

 

Naturally aspirated remain tricky!

 

The easiest/cheapest way to see increased performance is to reduce

weight. Especially rotating weight,for improved acceleration. Do most

people ask the most important question when buying new wheels,after

ensuring the offset and sizing is correct? Do they *uggery :-) They

should take a fishermans scales with them,and weigh the damned

things. The first question a race car manufacturer asks his potential

wheel suppliers is what do they weigh,and what is their rotational

inertia. Simple questions,and the weight,if not rotational inertia,is

easily self assessed performance differences can be

surprising,and worthwhile. Given 3 different makes of tyre,with similar

grip and handling characteristics,go for the lightest..Just weigh some

of the cheap imported tyres against a decent performance make,like a

Hoosier competition tyre that is road legal. The difference is

amazing. As for remolds,they are incredibly heavy.

 

If you are serious,and can live without goodies,buy a car with the

minimum spec. Sun roofs,air con,PAS,electric windows and mirrors,power

seats all can add hundreds of pounds. Lightweight front seats can add

as much performance,in real terms,as a new exhaust and manifold. 40

pounds of fancy stereo gear does nothing for performance ;-)

 

As cars become better,and more highly developed,the art of tuning

their engines becomes more complex and expensive,unless one looks at

the situation with a bit of lateral thinking. Instead of adding

things,think in terms of removing them. Instead of buying a new set of

wheels just for their looks,weigh them,and see if a gain can be had

for free there.

 

Just ideas,some may be practical for your situation,some not,but be

aware it is all too easy to buy so called performance bits,and get the

thing to go *slower* At least the engine in your car starts off as

one of the best basis for tuning available.

[Terminator]

Interesting reading, thanks guys

[Tom]

Good link here;

 

http://www.mkivsupra.net/vbb/showthread.php?t=19563&highlight=tuning+n%2Fa