olegreen94

Just wondering if anyone has tried this turbo. I have a 7875 now on a 6.0 and was wondering if the 77/83 would be a good up grade and provide less back pressure since the 7875 starts to fall off around 6000 rpms on my 6.0

drecpt83

I just got one a few weeks ago for my 5.3 But I'm still in the building stages so I don't have any performance data yet. I would think it would work great on a 6.0 as Well but maybe someone with more experience will chime in.

35spline

iTrader: (1)

It might be a little better but it only comes with a .96ar so I would guess you are going to be somewhat limited on the top end. I was talking to vsracing today about the 77/83 today and was being steered towards a 475 T6 to avoid back pressure issues.

olegreen94

Oh yea I'm sure the T6 flange 475 would be worlds better... But I'm limited with a t4 flange and also limited on space as I built my hotside around the 7875 and didn't leave much room for growth. So really just looking for a better or best flowing t4 flange charger.
Thanks for the reply's

Forcefed86

iTrader: (4)

Will def be an upgrade, can't say how much. I run my T4 (1.25ar) S476 up to 6800 without choking on a 370 with a 224/224 @113 .600 lift cam. Running the 87/96 exh wheel in it thou. Back pressure is around 2.2:1 up to 20lbs.

olegreen94

My only real thought here is that I could make a little more power at the same boost level going from the 7875 to the 77/83 and it could be a little easier on the motor because of the decrease in back pressure.
The car made 673hp and 737tq on 14lbs on the 7875 and that is on gen 3 rods soooooo I know I am pushing the envelope already just tossing the idea around since it's not really that expensive or a upgrade.
Thanks for the info

St. Mary

Which 7875 (VSracing or Turbonetics?)

olegreen94

Its a On3 7875. Car has 1000 miles on the setup and no hiccup on the turbo. And I have beat the sh*t out of it. The car trapped 131mph leaving the line off idle and short shifting 1st gear. So the setup definitely works just thinking I could maximize what i already have with the 83 turbine wheel and a 4inch down pipe.

blackedout drop ls1

iTrader: (91)

I'm having back pressure issues as well i got 6.0 7868 car made 740tq 670hp falls on its face around 5600

Forcefed86

iTrader: (4)

Did you get an actual back pressure reading? Or are you just assuming? I've seen as 68psi back pressure wise at 25lbs (2.7:1+)and still pull strong to red line.

coltboostin

Agree'd. Just because the power may be falling off does not mean the turbo is "done". Cam, IC, IM, tune.....ect all could play a factor.

olegreen94

I had the car tuned by a very good tuner so I wouldn't think that would be cause, the cam is a stage 1 tick turbo cam which is supposed to be in operating range till 6500 rpms.
The intercooler is a eBay 31x12x4 so I guess that's a possibility. The power doesn't really die off hard but the dyno graph definitely falls off around 6200. With stock rods I really should spin it past there anyway but...
Really just wondering how much of a upgrade the 77/83 would be over the 7875 and if it would reduce back pressure enough to justify the swap and retune. Also it's probably the biggest physical sized charger I could fit in my car the way I built the hotside so that's the reason for going with the 77/83 versus say a s475.
Thanks for all the input

35spline

iTrader: (1)

I really wish someone would post up their experience with a 6.0 and the 77/83.
I am on the fence between it and a s475/83 1.25 ar T4 for my 80 Malibu project. The downside to the 77/83 is only one AR option at .96. The cost saving is significant,around $400 when you figure in free shipping from Vsracing.

olegreen94

that is definitely a down side is the .96 ar... I guess that was my original question is how much would the 83 wheel help vs the 75 wheel with it being the same AR as the 7875.

I actually have the two turbos setting at my house the 7875 on my car and my roommate has the vs 77/83 for his current project and the physical size is a pretty big difference and the 4inch exhaust outlet would have to help some too.

I would just throw it on my car but it wouldn't be as simple as just bolting it on and getting results because of the physical size difference and the down pipe outlet size being different I would have to do some more fab work to make it fit.

RoidedSS

Why not the 88/83?

Forcefed86

iTrader: (4)

I wouldn’t take that .96 AR rating as factual. I don’t think they have a clue what the actual AR is. It looks much larger than other .96AR t4 housings I’ve seen. Ports look larger etc…

Companies making this crap aren't performance oriented and most likely copy and pasted another turbo description not knowing how to measure AR or what the "AR" even is.

olegreen94

I would have to agree with that forcefed because like I said I have the 78/75 and the 77/83 basically side by side both of which are supposed to be t4 .96ar and there is no way they are the same on the exhaust side. The 77/83 is much large in every aspect.

olegreen94

Has anyone got any results from one of these turbos yet?

tim wellington

x2 agree had mp 76 with .96ar now have precision 76 with .96 .they look total different. i dont know how to measure either ,but i know they looked different