Tuesday, May 12, 2009

Mivec 4G92 DOHC

GENERAL ENGINE DATA

Engine
1.6L 4 cyclinder DOHC 16-valve MIVEC

Model
4G92 (Gen. 1)

Capacity
1597cc

Bore
81mm

Stroke
77.5 mm

Compression Ratio
11:1

Valve Timing
Intake :
Open (BTDC) 17' (primary cam) / 47.5' (secondary cam)
Close (ABDC) 31' (primary cam) / 72.5' (secondary cam)

Exhaust :
Open (BBDC) 41' (primary cam) / 70' (secondary cam)
Close (ATDC) 11' (primary cam) / 35' (secondary cam)

Cam Spec
Intake :
duration : 228' / lift : 7.58mm (primary cam) 285' / 10.41mm (secondary cam)
Exhaust :
duration : 232' / 8.24mm (primary cam) 300' / 9.83mm (secondary cam)

Maximum Power
175ps @ 7500rpm

Maximum Torque
17.0kg/m @ 7000rpm

Fuel System
Multi-point Fuel Injection

Spark Plug Type
NGK BKR7EX-11 (BKR6EX-11 mostly for city driving)

Spark Plug Gap
1.1 mm

TRANSMISSION

Manual 5-speed

Gear Ratio:

1..........3.083
2..........1.947
3..........1.285
4..........0.939
5..........0.756
R..........3.083

FDR......4.592
======================================================

MIVEC not working??
(source from mivec.co.nz)

Low oil pressure
This is usually due to low oil level so first thing to check is your oil. Its a good idea for cars 'dependent' on oil pressure to be fitted with an Oil Pressure gauge. If the Oil pressure drops a lot whem the mivec engages its probably due to mechanical failure in the head. Check for lose/broken camshaft caps or worn camshaft tray. Low oil pressure is usually simply due to engine wear. Running a heavier grade oil (like 20W-50) may give some improvement but most of the time you will need to have your engine rebuilt.


Engine not upto temperature
It is normal for the MIVEC not to engage when the engine is cold. This can also mean that if you have a faulty thermostat your engine never gets warm enough for the MIVEC to operate. Make sure your temperature guage reads about midscale during normal operating conditions. The temperature sensor the ECU uses is not the same as the one for the gauge, so a faulty sensor can also lead to MIVEC not operating.


Stuck or blown solenoid valve
Apply 12V to the terminals and ensure the valve operates (audible click) You can remove the MIVEC Solenoid (MD models have two) valve quite easily and give it a clean in suitable parts washer. Run parts washer thru the valve with it open and closed to ensure its working properly and that its gets well cleaned.




ECU faults
This could either be due to poor power supply (worn out capacitors) or blown driver ICs. Either case requires the ECU to be serviced by a professional. Its recommended to have the capacitors replaced BEFORE you notice a problem or as part of normal servicing at the 10 year old birthday. (1G models are particularly susceptible). By the time a problem presents, there may already be permanent damage to the ECU.


Sensor Faults
Dirty connectors, frayed/broken wires, or failed sensors can prevent the ecu engaging mivec but generally this will also cause other drivability problems.. Its always good practice to get a diagnostic done to help rule out sensor failure.


Mivec Engine Modification - Staying Normally Aspirated
(sourced from mivec.co.nz)

These are in order that will typically give you best 'bang for the buck' as you go and get progressively more expensive. Generally you shouldn't start mods in the next stage until you'd done everything in the stage before.


STAGE ONE

Free Flowing Rear Muffler box
The brand is not important but a good design is not overly 'loud' while still providing good flow. I good trick is to use a 2 1/2 in/out muffler box

Pod Filter with Improved Cold Air Intake
Brand is not that important as any pod filter will outflow the factory panel filter. Popular choices are K&N and Simota. Cold air intakes can made from a large diameter pipe ducted to the front or by fitting a bonnet scoop.

Exhaust System 2 1/4" or (2 1/2 for 2L V6)
Mandrel Bent system is best but is a more expensive option than press bent. If going press bent, increasing pipe size to 2 1/2 is an option, but a mandrel bent 2 1/4" system is optimal for road driven cars.

Headers 4-2-1 or 4-1 Style
Generally both of type will give improvements accross the rev range.

Rechiped factory ECU
Available for 1G owners only.


STAGE TWO

63mm Throttle Body
The stock 60mm throttle can be bored to 63 very easily and gives very good gains

Fuel Pressure Regulator (optional)
To compensate for larger amount of air available, you will need to at least increase fuel pressure slightly.

ECU
A programmable aftermarket ECU will get the most out of the modifications done so far, and will be required if you want to go further still.

Injector Upgrade
By now your injectors will probably be operating well beyond the 80% duty cycle so its time to upgrade them something larger. GSR-T 390cc injectors re a good choice and can be had 2nd for cheap. Best done at the same time as the ECU upgrade.


STAGE THREE

Exhaust system 2.5"
To get the most out of the next stage you will need to free up the exhaust even more. This may result in a reduction in low rpm performance, but by now your probably going racing and gains up top will be worth it.

Increase Compression Ratio 12:1
Required to get the most out of the camshafts.

Camshafts
JUN or RPW offer racing camshafts. Two types are available to suit race or rally. Regrinds are also an option if on a tight budget.

Pistons and Rods
Lightweight pistons and rods will potentially allow higher RPM. Not much off the shelf, so they will have to be custom made.

Crankshaft
Knife edging, and fine balancing all the moving components will reduce parasitic losses and increase reliability at sustained high RPM

Basic Guide parts of doing a 1.8 Hybrid.
(sourced from mivec.co.nz)

Block
4g93 DOHC turbo block has oil squirter's for the pistons, all other 4g93 DOHC/SOHC don't but all will fit the 4g92 mivec head.

Crankshaft
4G93

Rods
4G93

Pistons
4G92 MIVEC, 4G92 SOHC/DOHC, 4G93 SOCH/DOCH or custom to suit desired compression ratio

Headgasket
Head gasket is 4G9x from .5mm (standard gen2 mivec) to 1.5mm(fibre/carbon fron gen1 and GSR)
A 2mm copper/custom gasket is needed to bring CR down to 11.0:1 in a 4G93 with 4G92 mivec pistons.

4G93 crank + 4G93 rods + stock piston - 4G93 block height = 0mm
4G93 crank + 4G93 rods + MIVEC piston - 4G93 block height = +1mm
There are high compression 4G93 pistons in a GDI that may work but they maybe 12:1 already.

Cambelt
4G94 159 tooth is perfect

Gearbox
Factory 4G92 Mivec Gearbox
Clutch & Flywheel: Factory 4G92 Mivec

ECU
Minimum is a piggyback but a full aftermarket recommended for optimum performance.

Injectors
390cc (from GSR Turbo)

*Notes
Nothing from 4G6X fits other than the spring shims in the head and injectors. Gaskets and fuel rail etc have different bore spacing and sizes.

A hybrid turbo will be a GSR bottom end with mivec head and longer belt, so much simplier than building a NA.

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