Sil­ver­ado to get GM’S new 2.7-litre, turbo en­gine

South Shore Breaker - - Homes - JIM KERR edi­tor@southshore­breaker.ca

Hy­brid and elec­tric tech­nol­ogy are im­prov­ing but so is the tech­nol­ogy in gaso­line in­ter­nal com­bus­tion en­gines.

Gen­eral Mo­tors’ new 2.7-litre turbo en­gine is a great ex­am­ple of the im­prove­ments pos­si­ble with a gaso­line en­gine and it will be of­fered this fall in the 2019 Chevro­let Sil­ver­ado 1500 pickup.

With 310 horse­power and 348 ft.-lbs. torque, 22 per cent more than the 4.3-litre V6 it re­places, the 2.7-litre turbo en­gine was de­signed specif­i­cally for trucks and de­liv­ers its peak torque from 1,500 rpm to 4,000 rpm.

Ac­cord­ing to Tom Sut­ter, chief engi­neer for the 2.7-litre turbo, “the new 2.7-litre turbo is a tech­no­log­i­cal marvel, with our most ad­vanced val­ve­train.”

There are three sep­a­rate tech­nolo­gies used in the valve train that work to­gether to max­i­mize per­for­mance. The en­gine is GM’S first turbo en­gine to use ac­tive fuel man­age­ment, which de­ac­ti­vates two cylin­ders un­der light loads by keep­ing valves closed and turn­ing off fuel in­jec­tors.

This max­i­mizes fuel econ­omy un­der light loads. The valves are re­ac­ti­vated again within two rev­o­lu­tions of the crank­shaft when power is needed, which at a cruise rpm of 2,000 rpm takes only .06 of a sec­ond.

Con­tin­u­ously vari­able valve tim­ing tech­nol­ogy helps the 2.7-litre de­liver strong en­gine torque at low rpm while pro­vid­ing more en­gine ef­fi­ciency at higher rpm.

The third tech­nol­ogy uses an elec­tro-me­chan­i­cal vari­able valve lift sys­tem that pro­vides al­ter­nate camshaft lift pro­files.

The elec­tro­mag­netic ac­tu­a­tors shift a mov­able shaft that con­tains dif­fer­ent cam lobes so both the in­take and ex­haust valves can change the amount of lift.

A low lift pro­file on the shaft give op­ti­mum fuel ef­fi­ciency at low and mid rpm speeds, while the high lift pro­file al­lows more air­flow past the valves at high rpm to max­i­mize power.

It’s like hav­ing two en­gine de­signs in one pack­age — one for fuel econ­omy and one for per­for­mance.

Low rpm torque is im­proved by the use of a long-stroke pis­ton de­sign. A long stroke (the dis­tance the pis­ton moves up and down in the cylin­der) in­creases the torque by us­ing more of the com­bus­tion pres­sure on the top of the pis­ton and the added lever­age ap­plied to the crank­shaft.

A down­side of a long-stroke de­sign is that it places more load on the pis­ton skirts and more in­ter­nal fric­tion.

To help al­le­vi­ate that, the forged steel crank­shaft (rather than cast steel) is po­si­tioned slightly off cen­tre in the alu­minum en­gine block so the pis­ton and con­nect­ing rod push more di­rectly down when there is max­i­mum pres­sure on top of the pis­ton.

The en­gine also in­cor­po­rates oil jets that spray the bot­tom of the pis­tons, which help cool the pis­tons and pro­vide ad­di­tional lu­bri­ca­tion for cylin­der walls.

The tur­bocharger used on this 2.7-litre en­gine is a dual-vo­lute de­sign that uses two sep­a­rate cham­bers and noz­zles to di­rect ex­haust gases from the en­gine to the tur­bine wheel.

This de­sign pro­vides quicker tur­bocharger re­sponse and en­hanced low rpm en­gine torque.

The en­gine’s ex­haust man­i­fold is in­te­grated with the alu­minum cylin­der head and splits the ex­haust chan­nels so the gases are di­rected to the two tur­bocharger pas­sages.

This split chan­nel de­sign also helps scav­enge the ex­haust gases out of the en­gine for im­proved per­for­mance.

A charge-air cooler (in­ter­cooler) is con­nected be­tween the tur­bocharger com­pres­sor out­let and the en­gine in­take to cool the in­take air that was heated as it was com­pressed.

The charge-air cooler low­ers the air tem­per­a­ture by about 74 C. Lower air tem­per­a­ture makes the air denser, so more can be pumped into the en­gine for more torque.

Other tech­nolo­gies built into this en­gine in­clude a vari­able dis­place­ment vane-type oil pump that changes oil flow to re­duce par­a­sitic power losses.

An elec­tric wa­ter pump is also used for the same rea­son plus it can also pro­vide heat to the pas­sen­ger com­part­ment when the en­gine is op­er­at­ing in start/stop mode.

Ac­tive ther­mal man­age­ment is unique in that it uses a ro­tary valve sys­tem to change the coolant flow through the en­gine so that hot coolant is sent to heat spe­cific lo­ca­tions for a quicker en­gine warm-up and cool parts when needed for per­for­mance.

This 2.7-litre turbo en­gine is a clean-sheet de­sign, started from scratch to uti­lize the lat­est tech­nolo­gies and pro­duce the type of power needed for truck use with the fuel econ­omy to­day’s driv­ers seek.

Con­trib­uted

This new 2.7-litre turbo en­gine avail­able in the Chevro­let Sil­ver­ado is a clean-sheet de­sign, started from scratch to uti­lize the lat­est tech­nolo­gies and pro­duce the type of power needed for truck use with the fuel econ­omy to­day’s driv­ers seek.

GM

Gen­eral Mo­tors’ new 2.7-litre turbo en­gine will be avail­able in the 2019 Chevro­let Sil­ver­ado 1500 pickup.

Newspapers in English

Newspapers from Canada

© PressReader. All rights reserved.