VARI­ABLE GE­OM­E­TRY

Vari­able vanes for vari­able gains

Ultimate Diesel Builder's Guide - - Contents -

The in­tro­duc­tion of the Vari­able Vane Tur­bocharger (VVT) on the LLY GM Duramax in 2004 may have been mostly emis­sions con­trol re­lated, but in the years since, it has proven to be a solid per­former with great power po­ten­tial with a few tweaks from the af­ter­mar­ket. The Gar­rett VVT used on the 2004.5-2016 Duramax has gone through a few re­vi­sions with each en­gine plat­form, but re­mains a pretty solid tur­bocharger for daily driv­ing, tow­ing and power out­put up to around 530 horse­power.

But as with any­thing else, the af­ter­mar­ket al­ways finds ways to im­prove per­for­mance and the VVT turbo is no dif­fer­ent. High Tech Turbo of Salt Lake City has spe­cial­ized in ev­ery­thing turbo since 1985 and has been mod­i­fy­ing the OEM Duramax tur­bocharg­ers for quite a few years with great suc­cess. The Promax 64 will sup­port up to 600 rear-wheel horse­power and can re­duce

ex­haust back­pres­sure and EGTS for daily driv­ing and tow­ing ap­pli­ca­tions. It also bolts di­rectly in place of the stock unit, with no other changes nec­es­sary.

When GM started look­ing for ways to re­duce emis­sions in the 6.6L Duramax en­gine, the vari­able ge­om­e­try tur­bocharger helped im­mensely. By al­low­ing quick low-rpm re­sponse, the VVT can bet­ter con­trol smoke out­put at low boost, all while cre­at­ing higher back­pres­sure in the ex­haust stream to force ex­haust gases through the Ex­haust Gas Re­cir­cu­la­tion (EGR) sys­tem. Keep­ing the ex­haust vanes closed makes it feel like a small tur­bocharger with good re­sponse. But open­ing those vanes up so the ex­haust can flow freely gives it the feel of a larger tur­bocharger for bet­ter power and tem­per­a­ture con­trol, to a cer­tain point at least. Run­ning low 500hp tunes, most own­ers will see ex­treme EGTS and ex­ces­sive drive pres­sure num­bers at wide open throt­tle. The com­pres­sor wheel just won’t move enough air and the re­stric­tive tur­bine side be­comes a choke point and lim­i­ta­tion to safely mak­ing more power. To over­come this, HT Turbo up­grades both the com­pres­sor and tur­bine wheel with larger, high-flow­ing wheels that are bet­ter suited for the 400600hp crowd.

First off, on the com­pres­sor side of the LLY and LBZ tur­bocharg­ers, the stock 11-blade wheel is re­placed with a 63mm bil­let 6-blade wheel that will in­crease vol­ume at sim­i­lar boost pres­sures. This wheel de­sign of­fers bet­ter flow and en­gine ef­fi­ciency in the mid-range for bet­ter power and EGT con­trol. Of course, the com­pres­sor cov­ers are ma­chined to ac­cept the larger com­pres­sor wheel. On the ex­haust side, the fac­tory 12-blade tur­bine wheels are re­placed with a 10-blade pro­file wheel, which will bet­ter han­dle the ex­haust flow be­ing cre­ated within the en­gine at the higher horse­power lev­els. The change to a larger-di­am­e­ter 10-blade wheel will re­duce drive pres­sure with­out af­fect­ing spool-up. In most cases, a mi­nor tun­ing ad­just­ment within the vane con­trol ta­bles can make this tur­bocharger drive al­most like stock, un­til you ham­mer on it and re­ally feel that broader torque curve from the ma­jor jump in air­flow.

Along with their cus­tom ma­chin­ing and wheel up­grades, HT Turbo also up­grades some of the in­ter­nal pieces, like chang­ing to a 360-de­gree thrust bear­ing to bet­ter han­dle the stress and added load the turbo may see at higher boost lev­els. Each charger is cleaned, in­spected and closely mea-

sured to en­sure the new bear­ings and seals will be within OEM spec­i­fi­ca­tions. The ro­tat­ing as­sem­blies are also fully bal­anced on high speed bal­ancers so that pre­ma­ture bear­ing fail­ure can be avoided.

If there is one com­mon flaw within the Gar­rett VVT de­sign, stick­ing vanes or a failed uni­son ring, which con­trols the ex­haust vanes, is the most likely cul­prit if you ex­pe­ri­ence in­ter­mit­tent re­sponse and driv­ing is­sues from the OEM VVT unit. On high-mileage trucks that have seen a lot of soot and ex­haust build-up over time, any small mov­ing part, like those vanes, could ex­pect to see some wear. Un­for­tu­nately, these is­sues are just the na­ture of the beast within any vari­able ge­om­e­try turbo. Of course, all these pieces are fully cleaned and in­spected be­fore as­sem­bly of a new Promax 64 to be sure ev­ery­thing will work as it should once in­stalled on a cus­tomer’s truck.

Speak­ing with Bray­don Price of Merid­ian, Idaho, who re­cently in­stalled the Promax 64 on his mildly built LBZ truck, we were able to get first­hand feed­back on his mod­i­fied VVT. He had been look­ing to im­prove peak horse­power in his Max Ef­fort tunes, while re­duc­ing EGT tow­ing in his lower horse­power tunes. Price works as a sales rep at Adrenaline Truck Per­for­mance (ATP Trucks), which spe­cial­izes in cus­tom EFI Live tun­ing and the Duramax af­ter­mar­ket in gen­eral, so he knows a bit about these trucks and what it takes to re­ally dial one in. With a cold-air in­take, 4-inch ex­haust, lift pump and a built Al­li­son trans­mis­sion, the truck made 512 hp in his Max Ef­fort tune with the stock tur­bocharger. Swap­ping over to the High Tech Turbo Promax 64, the peak out­put jumped to 574 hp, an in­crease of 62 horses with no other changes to the truck. Best of all, the py­rom­e­ter gauge has shown drops of nearly 150 de­grees at wide open throt­tle and he’s also re­ported it be­ing much eas­ier to con­trol EGTS while tow­ing heavy in tunes that make 400 hp.

The crew at High Tech have seen trucks run­ning mild in­jec­tor up­grades and healthy CP3S make more than 600hp with this turbo with near stock driv­ing char­ac­ter­is­tics. The Promax 64 is cur­rently avail­able for the LLY and LBZ plat­forms, but a direct bolt-in up­grade is near­ing re­lease for the LMM and LML trucks as well. For those of you look­ing to main­tain all the fac­tory emis­sions equip­ment (DPF, Urea, EGR), the af­ter­mar­ket is catch­ing up, and these should be a great up­grade for im­prov­ing air­flow to that big Duramax en­gine, re­gard­less of the model year. UDBG

High Tech Turbo spe­cial­izes in the diesel tur­bocharger mar­ket with op­tions avail­able to fit just about any ap­pli­ca­tion. Stock re­place­ment, tow­ing per­for­mance, hot street per­for­mance, mod­i­fied VGTS, Borg­warner S300 and S400 SX-E, com­pound tur­bos and even triple turbo sys­tems can be en­gi­neered, de­vel­oped and shipped out their doors.

Ready for as­sem­bly, this LBZ Duramax Vari­able Vane Turbo has al­ready been in­spected, cleaned, ma­chined and bal­anced. Mod­i­fy­ing the stock unit to the Promax 64 spec­i­fi­ca­tions in­cludes a larger bil­let com­pres­sor wheel and high-flow tur­bine wheel to in­crease flow, re­duce back­pres­sure and lower EGT.

Con­vert­ing to the 10-blade tur­bine wheel will move more ex­haust more ef­fi­ciently, thereby re­duc­ing drive pres­sure. While slightly larger than stock, this tur­bine wheel of­fers great spool-up and will sup­port up over 600 hp.

On the tur­bine side of the Gar­rett VVT, the fac­tory 12-blade ex­haust wheel (left) of­fered a good bal­ance be­tween spoolup and power, again best suited for up to 500hp ap­pli­ca­tions. For those look­ing to re­duce EGTS and back­pres­sure at higher power lev­els, the Promax tur­bocharger uses a larger ex­haust wheel with 10 blades (right).

The HT Turbo Promax uses a unique 63mm 6-blade bil­let com­pres­sor wheel with stag­gered fin heights to im­prove over­all air­flow through the en­tire rpm range. The change in wheel de­sign in­creases vol­ume, mean­ing bet­ter en­gine ef­fi­ciency with bet­ter peak power and EGT con­trol.

For the fol­low­ing mod­els, start­ing with the LBZ, GM went to a smaller com­pres­sor wheel size. The 60mm wheel is still more than enough to sup­port a 500hp truck.

The fac­tory LLY com­pres­sor wheel was the largest for the 2004.5-2016 trucks, at just un­der 63mm. The 12-blade de­sign of­fers good low-rpm re­sponse, but lacks high-rpm flow.

The back plate re­ceives a new com­pres­sor side thrust col­lar and pis­ton ring to en­sure oil doesn’t weep past the col­lar.

The oil plunger is one of the first pieces in­stalled into the bear­ing hous­ing. This plunger will move back and forth within the bore which moves an in­ter­nal gear that will con­trol vane po­si­tion.

The thrust col­lar is in­stalled into the bear­ing hous­ing, fol­lowed by the new 360-thrust bear­ing. There will then be a square O-ring in­stalled to seal the bear­ing hous­ing to the alu­minum back plate, which is next to go on.

The notched plunger must be lined up with the teeth of the vane gear to en­sure the vanes uni­son ring will ro­tate prop­erly to con­trol vane po­si­tion while driv­ing.

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