$peed cost$, how FA$T do you want to go?
Given, it is a Suzuki Sidekick or Tracker.
Macro list (by costs)
- Make
engine breath better. (but at what RPM and load?) Most street cars run
better with low RPM huge torque, not race car at 120 MPH on a circle
track.
- A higher compression ratio (increases engine
efficiency & power, at the cost of premium racing fuels (high Octane) and the need for a knock sensor...
- More displacement ! (larger bores, or large engine swaps)
- A more powerful fuel ( that includes NOS, NOS adds more Oxygen and can burn, the more added fuel (NOS INJECTION SYSTEM)
- Forced Induction
(turbo, supercharger) The best of all ways, on street cars. as car will
still have great economy if driven sanely. but is very expensive (done
right).
- all the above.
A word of advice on force induction, is to have PCM strategies, to discover live PING (sensors) and then retards spark to end ping fast and to go richer, at ping or you will buy a new engine soon.
Stay below 5 PSI boost or 10 on already turbo ready engines, like Mazda 1.8L or Nissan's 3.0L I6 TB48DE
(join a turbo forum for your engine is best)
References used:
8% increase in torque per pound of boost. So 5 PSI is 5 x 8 or 40% boost in torque,
The MPI stock engine is 98 foot lbs of torque at 4000 RPM , (then falls off) and will have about 137 foot/lbs of torque at 5 PSI. (estimates)
HP equation is below.
HP = T x RPM / 5252
Myths and facts of Exhaust back pressure and velocity debunked.
The myth is that bigger, is always better ?
Did you know that you can tune an exhaust pipe, for max scavenging action ,at a specific RPM and you can actually get better that 100% VE (volumetric efficiency) it's acts like a mini -turbo, at valve overlap, but you must give up low end power. Common on loop track engines.
VE means Volumetric Efficiency or more simply, the ability for suck in all the air, that the Displacement says you have, ( a 400 cc displacement can suck in 400ccs of air. times 4) and compress all of it.
The VE is low at idle (the throttle valve is closed, and at full throttle , with no CAT installed , VE can be very high , near 95% under load.) CAT = Catalytic converter device.
For street machines, most folks want low end grunt (power) not wide open power. W.O.T max power is great on a circle track, at max RPM all day. W.O.T = wide open throttle.
One way to have low end grunt is long intake tubes. And long air clean pipes. (most C.I.A kits make this worse, and suck in dirt big time)
Using the best size exhaust tubing diameter is important. Too big is bad in almost all cases off a loop track.
The Exhaust modifications, may fail , for many a reason , and a loss of low end torque, because you tuned the exhaust for W.O.T
Most excessively large tube exhausts systems, cause that the power band to shift higher. ( worse for street usage)
WOT power and low end power, are a compromise, only you can work that out.
The reason is, because low RPM likes a high velocity exhaust for maximum power. (a contradiction of usage, street and circle tracks)
Low end power might be important to you , on the street machine. I'd bet !
This happens, poor low end power, with larger exhaust pipes and velocity is too low ( notice I avoided the killer words, back pressure, not me !
) Got 3.0" Pipes?, from an exhaust header back? It won't work right, at the low RPM end, for power (due to ultra low velocity exhaust gas flow !) Use the DYNO test, to prove this, many 1000s have.
If the velocity is lowered too far, the natural scavenging action of the motor, during valve overlap will be reduced or nullified , causing a power loss. Do not destroy Scavenging or you will loose power.
The Same issues of Velocity( too low), may cause that killer reversion, the exhaust backing up to the combustion chamber during valve overlap . Avoid Reversion like the plague.
Never allow power killing Reversion, to happen.( can cause killer ping detonation too.)
Unless building an engine from scratch with custom ECU etc, then you should use a low flow CAT , keeping the stock 02 sensors working and use reasonable size, tubing (no muffler ) to the exit point. 2" is just about right. (G16)
The 2" no muffler car will make all the noise you need and the younger friends happy.
A full study on exhaust pressure wave theory, better explains all the above better, and I leave you to research that, on your own.
Honda tech on Exhaust. (very good)
More Exhaust theory.
Comments: (USA cars)
Warning, the TBI engine ECU (-56Bxx) will not like physical engine VE changes, it has fuel tables just for VE (directlly or indirectly) and will inject fuel wrongly, if you change the VE , at full or near full throttle. (and when accelerating)
The MPI engine has a MAF sensor and this measures the air correctly no matter WHAT ! (it's a far better system for any VE changes at the upper limit of you MAF)
rev. 7
