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[Datsun 1200 encyclopedia]

EGR

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This prevents EGR from working until the engine warms up. This switch is your friend. This prevents EGR from working until the engine warms up. This switch is your friend.
-=== Thermal Vacuum Switch ===+=== 2-Port Thermal Vacuum Valve ===
From 1975, a simple, reliable engine-coolant Vacuum switching valve is used by most implementations. It threads into the cylinder head and is warmed by the engine coolant. Nissan started calling this a TVV (Thermal Vacuum Valve) in the 1980s. From 1975, a simple, reliable engine-coolant Vacuum switching valve is used by most implementations. It threads into the cylinder head and is warmed by the engine coolant. Nissan started calling this a TVV (Thermal Vacuum Valve) in the 1980s.
Line 93: Line 93:
The switch came on at an early temperature of 88-106F (31-41C). The switch came on at an early temperature of 88-106F (31-41C).
-=== 3-port Thermal Switch ===+=== 3-port Thermal Vacuum Valve ===
This switch looks similar to the 2-port TVV, but the third port goes to the air cleaner. It bleeds off the carburetor vacuum signal, thus de-activating EGR. It is used in conjuction with a vacuum-delay valve in the hose that goes to EGR valve, which smooths out the reponse on quick throttle changes. This switch looks similar to the 2-port TVV, but the third port goes to the air cleaner. It bleeds off the carburetor vacuum signal, thus de-activating EGR. It is used in conjuction with a vacuum-delay valve in the hose that goes to EGR valve, which smooths out the reponse on quick throttle changes.
-This 3-port switch allowed Nissan to combine the EGR switch with the [[TCS]] switch, since both systems bleed to air.+This switch is located on the rear of the cylinder head (firewall end), whereas the 2-port valve in on the front end.
 + 
 +This 3-port switch allowed Nissan to combine the EGR switch with the Spark Control (vacuum advance) switch, since both systems bleed to air.
* One port for EGR signal * One port for EGR signal
* One port for Vacuum Advance (spark) signal * One port for Vacuum Advance (spark) signal
* One port for air bleed * One port for air bleed
-TCS (Transmission Controlled Spark) was used on some Manual Transmission models, and cuts the spark advance when in certain gears. By using a 3-port switch, it can bleed off both spark advance and EGR signals. 
-=== Transmission Switch ===+By using a 3-port switch, it can bleed off both spark advance and EGR signals:
-Some models de-activated EGR when in nuetral or in top gear. This made use of the transmission Nuetral switch and transmission Top switch.+* When when the engine is cold, bleeds the EGR port, thus deactivating EGR
 +* When engine is in-between hot and cold, bleeds the distributor port
 + 
 + IMPORTANT
 + The three ports act differently
 + So connect the hoses correctly
 +* Top port: to air cleaner
 +* Middle port: To BPT
 +* Lowest port (closest to head): to distributor
 + 
 +== Vacuum Switching Valve ==
 +Some MT (manual transmission) models de-activated EGR when in nuetral or in top gear. This made use of the transmission Nuetral switch and transmission Top switch to electrically operate a bleed switch.
 + 
* 1975 Manual Transmission FED & CAN * 1975 Manual Transmission FED & CAN
 +* 1978 Manual Transmission USA except FU Engine models
 +
 +
 +This is similar to TCS (Transmission Controlled Spark) was used on some Manual Transmission models, and cuts the spark advance when in certain gears.
== Transducers == == Transducers ==

Revision as of 09:35, 9 November 2011

Exhaust Gas Recirculation (EGR) was first used starting with 1974 B-210 (North American B210) models. Australia 1200 utes got EGR in 1982. Japan 1200 trucks got it in 1989. It recirculates a small portion of the exhaust back into the combustion chamber. Although this dilutes the the air/fuel mixture (reducing performance), it reduces burning temperatures resulting in drastic reductions of Oxides of Nitrogen (NOx).

Contents

Overview

EGR is a key emission control technology. Even the new 2012 models use EGR, although now it can be effected by variable camshaft overlap and engine computer control. Datsuns use an early version of EGR which is heavy-handed regarding performance, but really does clean up the air.

The EGR valve simply mixes a little exhaust into the intake manifold.
23878.jpg
Varying amounts of exhaust gas are let in by the pintle valve, which travel to the inlet manifold via the large square opening.

How much exhaust is recircutated depends on the vacuum signal, which comes from a port high on the carburetor. This is not the distributor vacuum advance signal, but rather it requires a signal that does the opposite: gets stronger as the throttle is opened.

EGR does not work at full throttle, due to the vacuum throttle. So it won't hurt peak HP. It only affect part-throttle performance. It also does not activate at idle. It only takes effect in-between idle and full throttle.

For a detailed explanation of EGR, see the AutoZine Technical School article.

Basic EGR System

Datsun EGR consists of:

  • Exhaust manifold with an EGR port tube
  • Intake manifold machined to take an EGR body adapter
  • EGR passage body, which bolts to the intake manifold
  • EGR valve, which bolts to the body
  • One or more switches
  • Vacuum hoses
  • Carburetor modifed with addition vacuum port for EGR signal

EGR parts in red:
23872.jpg

Most basic EGR system
23879.jpg

Generally speaking, the more complex the EGR system, the better. The complexity was to use less recirculation which is good for performance and fuel economy. This simplest implementations affected performance worse. There is little downside to this complexity because generally if anything fails, EGR fails to work and so doesn't hurt performance.


Models using the simplest basic system include:

  • 1975 B210 AT North America (FED+CAL+CAN)
  • 1975 B210 MT.CAL (MT.FED and MT.CAN add more switches)
  • 1982 CAN all engines (A12A, A14, A15)

Exhaust Manifold

The only modification to the Exhaust Manifold to enable EGR is the casting is changed to add a threaded port to which a tube is fastened. The tube goes up to the EGR Valve.

First EGR (1974) -- tube goes behind manifold
22072.jpg


Late A14 style
21832.jpg

Early A14 FU style
19797.jpg

Vanette Style
23876.jpg

Variations consist of:

  • Size of the EGR port (diameter of hole and thread size)
  • Location. Early engine had it come straight out of the manifold outlet, while newer ones have it pointing almost up


Intake Manifold

Intake Manifold has a specially machined flat area where the EGR Body bolts. Nissan calls this adapter body the "EGR passage". In turn, the EGR Control Valve bolts to the body.

1981-1982 H95 EGR (valve not installed)
23877.jpg

EGI

A14E and A15E EGI fuel injection engine manifolds use an EGR system.

23874.jpg

23875.jpg

23873.jpg


Switches

These switches are to limit when the EGR works. Don't delete or bypass them otherwise your EGR will work full-time (not good).

Thermal Switch

This prevents EGR from working until the engine warms up. This switch is your friend.

2-Port Thermal Vacuum Valve

From 1975, a simple, reliable engine-coolant Vacuum switching valve is used by most implementations. It threads into the cylinder head and is warmed by the engine coolant. Nissan started calling this a TVV (Thermal Vacuum Valve) in the 1980s.

The switch has two ports. One hose comes from the carburetor signal, the other goes to the EGR valve.

The switch only opens when the coolant exceeds 134F (57C).

Thermal Electric Switch

For the first year 1974, instead of the simple thermal vacuum switch, an engine-coolant electric switch was used along with a relay and an electrically-operated vacuum switch. This was replaced in 1975 by the simpler thermo-vacuum switch.

The switch came on at an early temperature of 88-106F (31-41C).

3-port Thermal Vacuum Valve

This switch looks similar to the 2-port TVV, but the third port goes to the air cleaner. It bleeds off the carburetor vacuum signal, thus de-activating EGR. It is used in conjuction with a vacuum-delay valve in the hose that goes to EGR valve, which smooths out the reponse on quick throttle changes.

This switch is located on the rear of the cylinder head (firewall end), whereas the 2-port valve in on the front end.

This 3-port switch allowed Nissan to combine the EGR switch with the Spark Control (vacuum advance) switch, since both systems bleed to air.

  • One port for EGR signal
  • One port for Vacuum Advance (spark) signal
  • One port for air bleed


By using a 3-port switch, it can bleed off both spark advance and EGR signals:

  • When when the engine is cold, bleeds the EGR port, thus deactivating EGR
  • When engine is in-between hot and cold, bleeds the distributor port
IMPORTANT
The three ports act differently
So connect the hoses correctly
  • Top port: to air cleaner
  • Middle port: To BPT
  • Lowest port (closest to head): to distributor

Vacuum Switching Valve

Some MT (manual transmission) models de-activated EGR when in nuetral or in top gear. This made use of the transmission Nuetral switch and transmission Top switch to electrically operate a bleed switch.


  • 1975 Manual Transmission FED & CAN
  • 1978 Manual Transmission USA except FU Engine models


This is similar to TCS (Transmission Controlled Spark) was used on some Manual Transmission models, and cuts the spark advance when in certain gears.

Transducers

Transducer Valve gets a backpressure signal. One metal tube connects to the exhaust, and a vacuum line Tees into the EGR line. This allows the Transducer Valve to fine-tune the EGR signal.

BPT

Starting in 1977, a BackPressure Transducer (B.P.T.) Valve was added to USA models. The metal tube connects to a port on the EGR body, near where the main EGR metal tube came in.


Tube variations

  • 1977: BPT tube threaded on both ends on two-piece tube. Joined by rubber hose in the middle.
  • 1978 up: threaded on the manifold end, used a rubber hose on the Valve end

BPT was used with 2-port OR 3-port Thermal Switches
23880.jpg

VVT

Venturi Vacuum Transducer replaced the BPT valve on 1981 models to fine tune how much Recirculation is used. Instead of the crude early systems without VVT, the 1980s implementations use the VVT valve as an amplifier for input signals from backpressure and carburetor signal.

If you run EGR, then VVT is your friend.

History

1974: EGR fitted to North American B210.

Australia

Late-model utes were fitted with EGR.

Japan

1980-1981 EGI engines used EGR

1989-up 1200 Sunny Truck used EGR


North America

Keep in mind that intake & exhaust manifolds changed almost every year, for reasons not usually related to EGR. Also the EGR valve specification changed every few years, and differed by Transmission. Bolt pattern remained the same.


1974: EGR first fitted to North American B210. This was the A13 engine.

  • It used a basic system, except the switch was a complicated electric system.


1975: EGR continued on the new A14.

  • Simpler 2-port Thermal Vacuum Switch replaced 1974's electric switch, relay, solenoid and wiring.
  • On-temperature activation point was raised.
  • (FED + CAN) Manual transmission cars added Vacuum Switching Valve which enable nuetral and top gear EGR de-activation. CAL cars did not use this, nor did AT cars.
  • FED cars used a separate EGR warning system that did not interact with the EGR system. It simply notified the driver via dash light at 50,000 miles.


1976: 1975 system carried

  • B210 adopts same Thermal Vacuum Switch as Datsun 610 and Datsun 710 (minor change)
  • EGR tube shape changed


1977: For USA, EGR flow increased to reduce NOx

  • EGR warning system discontinued
  • Canada unchanged. CAL + FED is changed

FED + CAL NOx emissions tightened

NOx emissions
1976 all: 3.1 
1977 CAN: 3.1
1977 FED: 2.0 
1977 CAL: 1.5
  • Exhaust Manifold has larger EGR port, otherwise is same as 1976.
  • Larger EGR Tube to manifold
  • BPT valve added
USA Exhaust Manifold EGR 
Tube inner diameter 11.8mm (8mm 1976)
Manifold boss dia.: 32mm (25mm 1976)
Thread size: M22 (M16 1976)


1978:

  • CAN adopts large EGR tube (and Exhaust manifold), even though NOx requirements did not change
  • CAN retains basic EGR
  • BPT Tube (USA models) simplifed one-piece design
  • FU models retain 2-port thermal valve
  • USA non-FU changed to 3-port thermal valve


1979: no changes from 1978

  • CAN models: Basic EGR
  • FU Engine models: Basic EGR + BPT Valve
  • USA except FT: BTP Valve + 3-port TVV


1980

  • Switched back to 2-port thermal valve


1981

  • USA NOx emissions further restricted
NOx emissions - Passenger Car
1977-1980 FED: 2.0
1981 FED: 1.0 
---
1980 CAL: 1.0
1981 CAL: 0.7 
  • USA replaced BPT with VVT
  • FED EGR secondary air passage increased from 11mm to 18m
  • FED EGR Tube mounting screw increased from M20 to M22
  • USA uses VVT and 3-port TVV
  • CAN MPG (A14 FU engine) adds VVT and 3-port TVV, all other CAN models remain basic


1982: No changes