In the automotive world, an intake manifold or inlet manifold is part of an engine that supplies the air/ fuel mixture to the cylinders. The primary function of the intake manifold is to evenly distribute the air/ fuel mixture to each intake port in the cylinder head.
Now days most cars run on a so called “tune length intake manifold”. In the early days engineer think that shorter intake manifold will create much more power, but later on found out that a long intake manifold could actually improve output, due to a so-called “supercharging” effect
When fresh air is drawn into the combustion chamber, it gathers speed and momentum in the intake manifold. As soon as the inlet valve is closed, the fast-moving air hits the valve and compresses, generating high pressure. With no where to go, this high pressure bounces back, travels along the intake manifold, hits the plenum at the other side and bounces back again. In this way, the high pressure bounces back and forth along the intake manifold until the inlet valve opens again, creating pressure waves.
Now for the interesting part: if the inlet valve opens again exactly when the pressure wave comes back, the pressure wave will help charging the combustion chamber due to its high pressure. This is not unlike charging the combustion chamber with a light supercharger, thus its call a supercharging effect.
In order to match the timing of valve opening, the frequency of pressure wave shall synchronize with engine rev, obviously. This frequency is dependent on the length of the intake manifold (L in the figure). The longer the length, the longer the time pressure wave takes to bounce back thus the lower frequency of pressure wave is attained. As a result, a longer intake manifold leads to supercharging effect at lower engine rev. A shorter manifold leads to supercharging effect at higher rev. By selecting a suitable manifold length, we can obtain the desired power characteristic.
A sports car engine may employ a shorter tuned intake manifold to optimize its output at high rev (in the expense of low to medium rev output). On the contrary, a heavy sedan or commercial van engine may choose a longer manifold to favour low-rpm output at the price of high-rev output. As you can see, the selection of manifold length is always a compromise. That’s why many modern engines turn to variable intake manifold.
Alright lets start of by understanding the basic of how a 4-stroke engine works. Most engine that are found in vehicles nowadays are mostly 4-stroke.
The 4-stroke cycle is also know as Otto cycle name after its inventor Nicolaus Otto.
Alright enough with the history as I wish to keep this as short and as brief as possible. The reason why its called a 4-Stroke Engine is because it needs the piston to do 4 different things before 1 combustion cycle is complete.
So now lets take a look at what are the 4-Stroke that are needed for 1 complete cycle.
1. Intake – During this stroke the piston actually move downwards while the intake/ inlet valves are open. The vacuum effect cause by the piston moving downwards helps draw in the air/ fuel mixture.
2. Compression – During the compression stroke the piston is moving up and causes the air/ fuel mixture to be compressed in the cylinder. During this stroke both intake and exhaust valves are closed.
3. Combustion/ Power – During this stroke the combustion has already occur and the pressure of the combusted air/ fuel mixture will then force the piston to move downwards.
4. Exhaust – During the stroke the piston is moving upwards again and forcing the burnt gases out through the open exhaust valve.
For the piston to complete its 4-Stroke cycle the crankshaft need to rotate a full two turns which is 720 degrees, but this would be explained further in another post.
I personally hope this short and brief post can help you guys to understand the basic of a 4-Stroke Engine. I would also do my best from now on to get at least one new technical related post up once a week. So do STAY TUNED for more upcoming technical post.
Back in the 1980s, F1 teams fed hot exhaust gas discharge into the diffuser to energize the flow through it and thus increase down force. Car aerodynamics altered with charging technical regulations, and it became more beneficial to vent the exhaust through the rear deck, assisting the operation of the rear wing rather than that of the diffuser, which over time shrank in size.
The so-called double diffuser came along in 2009, and at the start of 2010 Red Bull surprised everyone by blowing exhaust gas through it. This year that double-deck diffuser is no longer permitted, and there is no hole allowed in the under body through which to feed exhaust gas to the diffuser area, aside from a small one for the starter motor. Nevertheless, it is beneficial to discharge gas each side of the diffuser upsweep so that it forms a virtual skirt, stopping the ingress of high-pressure air caused by rear tyre rotation.
Renault took a different approach for this year’s car. Where air rushes into the underfloor region at the leading edge of each side pod, there is a pronounced local pressure drop. Renault opted to feed its exhaust forward to the front of each side pod so that it discharges into those low-pressure zones, significantly enchanting their effect and thus adding to downforce generated at the centre of the car, rather than at the rear.
Whatever the approach taken, the upshot this year was a lengthening of the twin exhaust tailpipes, and in most instances the addition of bends, none of which was in the interest of engine performance. The current “frozen” engine specifications leave the engine manufacturers unable to do anything to try to counteract the loss implicit in tailpipes compromised with respect to aerodynamic gain. On the other hand, they have been able to assist the teams by developing strategies to create discharge on the overrun.
The flaw in the blown-diffuser concept is that it works only while the throttle is open. The driver needs downforce under braking and upon corner entry as much as on corner exit, so the trick is to maintain a flow of gas under those conditions. The technique of keeping the throttle fully open while cutting fuel and spark so that the engine simply pumps charge air through to the exhaust outlets has been termed “cold blowing”. Adding fuel but retarding the ignition so that most of it burns only in the exhaust – or using the heat of the exhaust rather than any spark to ignite it – has been termed “hot blowing”.
- Article from Race Engine Teachnology
Finally the Honda CR-Z has hit Malaysian soils, the price for this hybrid sport car from Honda is due to be sale at the price of RM115,000 OTR + Insurance. In the states the CR-Z is classified as one of the less polluting vehicles available and is rated as an Advanced Technology Partial Zero Emissions Vehicle (AT-PZEV).
The Honda CR-Z runs on Honda’s 1.5L i-VTEC SOHC inline 4 with Honda’s Integrated Motor Assist (IMA) hybrid-electric system. A 6-speed manual transmission is standard but it also offers a CVT gearbox (for the less sporty users).
The system delivers a combine peak output of 122bhp @ 6000rpm and 174Nm @ 1000 – 1500 rpm.
Alright this would be our very first technical know how post, so if you guys feel the need to improve in any sort of way just drop a comment, it is much appreciated.
Alright let me start with different type of Rotary ports. Rotary engine is never a common engine among drivers, but for enthusiast the Rotary engine has definitely reached a cult status. For those who know bout Rotary engine would know there are actually a few porting types/ styles that can be used, so now let us see the different type of ports and its effect.
A street port or also know as “mild port” for some actually cleans up the port but only slightly alters its shape. This porting job also adds a lip at the top of the port for enhanced flow. This method bumps top end power without changing the engine’s operating characteristics.