gpz turbo training manual - part1

TURBO MOTORCYCLE INTERNATIONAL OWNERS ASSOCIATION • FALL 1996 15

Kawasaki GPz750 TurboTechnical Training

ManualThe following is Part 1 of the Kawasaki GPz 750 Turbo Technical Training Manual.

It deals with turbocharger system theory and operation. Kawasaki used this manual to helptrain their personnel to understand and troubleshoot the turbo monster. Though some of ithas the unmistakable sound of corporate chest-beating (but hey, why not?) there’s a lot ofgood science contained in these pages for owners and tinkerers of any turbo persuasion.

Part II with feature a turbocharger troubleshooting guide. Look for it in our winter edi-tion. Thanks to Jill A. Dunning of Kawasaki’s Consumer Services Dept. for supplying theTMIOA with this manual.

INTRODUCTION

What makes Kawasaki’s 750 Turbo the world’s fastest? Learn just how easy it is tounderstand, troubleshoot, and tune this high technology system.

This is a comprehensive, technically-oriented program that focuses on systems andcomponents unique to the 750 Turbo.

Major emphasis is placed on theory and maintenance of the turbocharger system,while other topics covered include suspension, chassis, internal engine and DigitalFuel Injection components.

Upon review of the 750 Turbo Course, the student will:

• Thoroughly understand the turbocharger and all related systems (such as wastegate valve and actuator, boost pressure sensor and LCD boost indicator).

• Have awareness of the other differences between the GPz750 and the 750 Turbo.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval sys-tem, or transmitted in any form or by any means, electronic mechanical photocopying,recording or otherwise, without the prior written permission of Technical Services,Kawasaki Motors Corp., U.S.A. No liability can be accepted for any inaccuracies or omis-sions in this publication, although every possible care has been taken to make it as completeand accurate as possible. All procedures and specifications subject to change without priornotice or obligation. Illustrations in this publication are intended for reference use only andmay not depict actual model component parts.

©1984 Kawasaki Motors Corp., U.S.A.

16 TURBO MOTORCYCLE INTERNATIONAL OWNERS ASSOCIATION • FALL 1996

TURBOCHARGER FEATURES ...............................................................................................17TURBOCHARGER COMPONENTS .........................................................................................17DFI SYSTEM COMPONENTS AND OPERATION ...............................................................19LUBRICATION SYSTEM...........................................................................................................24CHANGES IN THE 750 TURBO FROM THE GPz 750 .........................................................25

Turbocharger System

Theory and Operation


NOTE:

This information provides the theory ofoperation and a structural description ofthe Turbocharger System. See the accom-panying “Troubleshooting Information”(next Turbo News - ed.) or the ServiceManual for service information.

TURBOCHARGER FEATURES

Unlike the other turbocharged motorcy-cles on the market, the 750 Turbo has itsturbocharger mounted low and in front ofthe engine. The combination of thisunique placement of the turbochargerand Kawasaki’s DFI (Digital FuelInjection) system makes the 750 Turboextremely powerful, yet very efficient andresponsive.

A turbocharger is a device which usesthe high temperature and pressure of theexhaust gases coming out of the engine topush more air into the engine. A turbineis driven by the exhaust gases, and it inturn drives a compressor which pushesair into the cylinders at greater thanatmospheric pressure. More air meansmore horsepower and torque.

The advantages of the turbocharger sys-tem are:

• Higher horsepower and torque can be achieved without increasing operating speeds or engine displacement.

• A lower specific fuel consumption can be achieved by turning the engine slower and by using “low speed” camshafts (less duration and overlap).

The result is that a turbocharged enginecan get better fuel economy than a “nor-mally aspirated” engine with the samepower output.

• Intake and exhaust noise is reduced since the turbocharger and related plumbing act as a silencer.

The intake and especially the exhaustpaths of the Kawasaki TurbochargerSystem are made as short as possible byplacing the turbocharger low and in frontof the engine and the air cleaner near theengine sprocket. As a result, Kawasaki’sTurbocharger System offers these extraadvantages:

• Better throttle response due to minimal “turbo lag.” “Turbo lag” is an expression that refers to the response time for the turbo to build pressure after the throttle is opened abruptly. The closer the turbine wheel is to the exhaust port, the less this performance lag will be.

• Minimal loss of exhaust gas heat energy and increased overall efficiency resulting from the very short distance between the exhaust valves and the turbocharger.

• A relatively low center of gravity which improves stability.

• The hottest parts of the system are placed well away from the rider for comfort.

TURBOCHARGER COMPONENTS

The turbocharger basically has fourparts: the turbine, which extracts the heatenergy of the exhaust gases; the compres-sor, which compresses the incoming air;the center housing, which carries theshaft between the turbine and compres-sor; and finally the boost control.


TURBINE

The turbine extracts the heat energy ofthe exhaust gases, changing it to rotation-al energy to drive the compressor.

It is made up of the turbine wheel andits surrounding snail-shell-shaped hous-ing. The housing directs the flow ofexhaust gas at the turbine wheel, allow-ing it to expand and cool. The expansionof the exhaust gases turns the turbinewheel through its blades. The shape ofthe blades forces the gas flow to spin theturbine wheel. The turbine wheel and itshousing are made of highly heat resistantalloys.

COMPRESSOR

The compressor is a centrifugal-typecompressor which pumps air into theengine at pressures greater than atmos-pheric.

It is made up of a compressor wheel anda surrounding snail-shell-shaped housing.The compressor wheel has twelve special-ly shaped blades on it, which push the air

as the wheel turns. The housing shapeallows the speed of the air to drop as itcomes off the compressor wheel blades.The drop in speed increases the air pres-sure as the air flows toward the engine. Aspecial casting method has been used toshape the compressor wheel blades.

CENTER HOUSING

The center housing supports the shaftconnecting the turbine and compressorwheels as it turns at speeds as high as200,000 RPM. A floating bearing, whichalso turns, is mounted in the center hous-ing, and it carries the shaft on two filmsof oil, absorbing the minute vibrationcaused by the tiny imbalance present ineven the most precisely manufacturedparts. The shaft rides on an oil film insidethe bearing shell; and the bearing shellrides on another oil film inside the centerhousing. The bearing turns at about 30%the speed of the shaft. Thus, the bearingspeeds between the shaft and the floatingbearing and between the bearing and thecenter housing are much less than that ofa fixed bearing. Lower bearing speedsreduce the likelihood of encountering anycooling or lubrication problems.


BOOST CONTROL

If the boost pressure were left uncon-trolled, it would rise as long as the throt-tle was held open until the engineexploded. It is very important to keep theboost pressure under control.

Two components working together con-trol the boost pressure. The wastegateallows some of the exhaust gas to bypassthe turbine when the pressure approach-es the design limit. The actuator is a pres-sure sensing diaphragm connected to thepressurized part of the intake tract. Itopens the wastegate when the maximumboost pressure is reached.

The boost pressure at which the actuatoroperates is determined by the preload onthe actuator’s internal return spring. Thespring is preloaded when the actuator rodis pulled out slightly in order to attach itto the wastegate valve.

DFI SYSTEM COMPONENTS

AND OPERATION

Kawasaki’s DFI (Digital Fuel Injection)system used on the 750 Turbo is basedupon that of the GPz1100.

The DFI system computes the optimumfuel injection quantity according to theprogram stored in the memory of the con-trol unit and information collected byvarious sensors which detect engine oper-ating conditions. The sensors constantlymonitor boost pressure, throttle position,engine RPM, engine temperature, andintake air temperature.

The following are the differences fromthe GPz1100 DFI system.


1. Turbocharger2. Compressor3. Turbine4. Centerhousing5. Boost Control6. Fuel Pressure Regulator

7. Fuel Filter8. Fuel Pump9. Injector10. Air Cleaner11. Surge Tank12. Throttle VaIve

13. Throttle Sensor14. Boost Pressure Sensor15. Air Temperature Sensor16. Engine Temperature Sensor17. D.F.I. Control Unit18. Boost Meter


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INJECTOR TIMING

Injection timing is changedfrom a 360 degree injectioncycle (1 injection/1 crankshaftrotation ) to a 720 degree injec-tion cycle (1 injection/2 crank-shaft rotations). Because therange of injection fuel quantitya turbocharged engine needs iswider than that of the conven-tional engine, it was necessaryto increase the injection timefor high engine RPM and reduceinjection frequency to improvethe accuracy of the injection

360° InjectionCycle

(1 injection/1 rotation)

720° InjectionCycle

(1 injection/2 rotations)

3° C 10° C

37° F 50° FEngine Temperature

Injection Timing

fuel quantity at idle. During cold starting only, the 360 degree injec-

tion cycle is used. Injection timing is changed inaccordance with cylinder head temperature asshown below.

ONE-SHOT ACCELERATION

ENRICHMENT

One-shot acceleration enrichment is an

added feature. It injects a specified fuelquantity at the instant the throttle issnapped open.

This eliminates any “time lag” if thethrottle is snapped open in the intervalbetween injections. In the GPz1100 DFI sys-


tem, the fuel quantity is not enriched untilthe next closest normal injection point.

NOTE :

“Acceleration enrichment” which is used onboth the 750 Turbo DFI and the GPz1100DFI, enriches the mixture only when theengine is cold. However, one-shot accelera-tion enrichment, used only on the 750 TurboDFI, works not only before, but also after theengine is warmed up whenever the throttleopening speed becomes greater than a prede-termined level.

BOOST AND ATMOSPHERE

PRESSURE SENSOR

The boost sensor is mounted on the backof the surge tank, and senses boost pres-sure through a small rubber hose con-nected to a fitting on the surge tank.Since it monitors whatever pressureexists inside the surge tank, the boostsensor also measures atmospheric pres-sure at low RPM’s and light loads. Theatmospheric pressure sensor mounted inthe GPz1100 control unit is therefore notneeded.

The boost sensor sends signals not onlyto the DFI control unit, but also to theboost meter which gives the rider anopportunity to visually monitor the boostpressure. (See wiring diagram in“Troubleshooting” handout.)

Boost pressure is controlled at the tur-bocharger with the wastegate and itsactuator. As a further safety measure, theDFI system cuts off fuel supply to theengine by interrupting the injector signalif the boost pressure exceeds the presetmaximum.

AIR TEMPERATURE SENSOR

The air temperature sensor in the aircleaner case has been replaced with anew air temperature sensor mounted ontop of the surge tank. In the surge tank, itcan react to changes in air temperaturecaused by boost pressure so that the opti-mum fuel injection quantity can alwaysbe determined accurately.

FUEL INJECTORS, FUEL PUMP,

PRESSURE REGULATOR VALVE

The GPz1100 system injects fuel into anintake tract which is always less thanatmospheric pressure. The ZX750 Turbosystem, however, must inject fuel into anintake tract which ranges from less thanatmospheric pressure (similar to theGPz1100) to well above atmospheric pres-sure on boost. In order to deliver fuelproperly under these more varied condi-tions, the pump, regulator valve, andinjectors have been changed.

The fuel flow rate of the injectors hasbeen increased by almost 30%.

Fuel delivery capabilities of the pumphave been increased as shown below.


This graph shows that for any given fuelflow rate (combined injector flow), a fargreater pressure is possible. This is nec-essary because of the greater injectorsflow rate and the need to maintain a con-stant pressure differential between thefuel system and intake manifold even athigh boost pressures.

A different pressure regulator valve isalso needed in order to maintain a con-stant pressure differential at high boostas well as during “off boost” operations.

LUBRICATION

The lubrication system of the 750 Turbois based on that of the GPz750. The differ-ence between the two is that new oil flowpassages are added, which route some oilfrom the oil cooler through the tur-bocharger, the sub-oil pan, the scavengingoil pump, and back to the oil pan.

The oil automatically flows down intothe sub-oil pan after lubricating the tur-bocharger floating bearings. From there,the oil is pumped up to the oil pan by thescavenging pump, which is mounted onthe left end of the secondary shaft infront of the engine sprocket.

This system eliminates oil consumptionproblems within the turbo unit which

have plagued other turbocharger systems.The turbo shaft bearings are lubricated byoil directly from the oil cooler. That oil isthen “pulled” away from the turbo by thescavenging oil pump and returned to thepan preventing any oil pressure build-upin the turbocharger center housing.

NOTE :

The small oil screen located In the tur-bocharger oil feed line banjo bolt must be


installed as shown in the illustration below.Incorrect installation can result in severelyreduced oil flow to the turbocharger.

CHANGES IN THE 750 TURBO

FROM THE GPz750

In order to make use of the powerpotential of a turbocharged 750cc engineand still maintain a high degree of relia-bility, acceptable off-boost performanceand good high-speed handling, Kawasakimade several changes to the base modelGPz750 engine, drive train and chassis.The following to a list of the most signifi-cant changes.

ENGINE

Flat-top pistons are used to lower thecompression ratio enough to allow signifi-cant boost pressures without requiringthe use of exotic fuels to prevent detona-tion. In conjunction with the flat-top pis-tons, a different cylinder head with asmaller combustion chamber is used. Thissmaller combustion chamber helps con-trol combustion and prevent detonation.The compression ratio of the 750 Turbo is7.8:1 compared to 9.5:1 in the Gpz750.

Very mild (short duration, low lift) cams

have been used in the 750 Turbo to helpcompensate for the low compression andimprove low RPM, off-boost performance.Since the intake tract is under high pres-sure at high RPM, there is no need forhigh RPM cams. As a result the 750 Turbohas a very flat horsepower and torquecurve with an impressive 73.1 ft.-lb. oftorque (10.1 kg-m) at a very low 6,500 RPM.

To handle the more than 30% increasein horsepower and almost 50% increase inmaximum torque, stronger connectingrods and bolts are used.

The power is transmitted to the jackshaft through a stronger hy-vo primarychain.

IGNITION

Even with the latest in combustionchamber design, detonation can be aproblem with the tremendous pressurescreated under full boost. For this reason,the 750 Turbo ignition advance curve has


been changed as shown to provide lessmaximum spark advance and thus furtherreduce the possibility of detonation.

TRANSMISSION

Different primary gear ratios (largerpinion gear, smaller clutch gear) are usedto reduce the load on the clutch andtransmission. The clutch housing isstrengthened and an additional clutchfriction plate is used.

The output shaft and bearings are madelarger for increased strength. Also theinternal gear ratios and final drivesprockets were changed in order to attainthe overall drive ratios most favorable forall-around performance.

SUSPENSION

All of the changes found in the 750Turbo suspension have been done toimprove high-speed stability.

Front Suspension

The front damping is slightly heavierthan the GPz750 and the anti-dive is mademore effective by making the valve spring(A) weaker, thereby allowing more move-ment of the valve (B) during braking. Fork

travel has been reduced from 6.2 to 5.1inches.

Rear Suspension

The shock absorber has heavier damp-ing, a stronger constant rate spring, andshock travel is reduced.

The rocker arm and connecting linksare aluminum for reduced weight, andthe geometry is changed to produce aslightly more progressive suspensioncurve. The combined effect of thestronger spring and the more progressiveratio is shown in this graph. Rear wheeltravel has been reduced from 5.1 incheson the GPz750 to 4.1 inches.


The aluminum swing arm wall thicknesshas been increased by 0.5 mm to addrigidity.

FRAME

The steering head pipe has been length-ened by 20 mm over the GPz750. Also,frame tube sizes and locations have beenchanged as shown in this illustration.

For better high speed stability, theframe geometry has been changed asshown below.

750 Turbo GPz750Rake Angle 28 deg 26.5 degTrail 117 mm 103 mm

BRAKES AND WHEELS

The front wheel is cast using anadvanced high pressure process whichallows it to be made about two poundslighter than the GPz front wheel.

The front and rear brake discs are 10mm larger than the GPz 750 discs(increasing the brake swept area) and thefront hydraulic hoses are made of anextremely strong braided synthetic fiberand teflon. These new brake lines arenearly as strong as braided steel linesand resist expansion when high pressureto applied.

Corrections...The photo at right that appeared in Turbo News #23 (page

26) was only half right in its caption. Yes, that is Ron Graf onthe left, but on the right is none other than Terry Cree ofBoulder Creek, CA, NOT Ted Engle of Boring, OR. Thanks to RonGraf who took great joy in pointed this out to Turbo News.

e-mail corrections...

Turbo News #23 also goofed on the e-mail addresses (page 29) of the following:

Anton Sop’s correct e-mail address is: [email protected] Driscoll’s correct e-mail address is: [email protected]

We apologize for the mix-ups

gpz turbo training manual - part1

Documents

shot acceleration

constant pressure

oil film inside

fuel flow

digital fuel

scavenging

compressor

turbocharger