2005vetteTT

iTrader: (1)

Hey all - currently i'm running a stock LS2 with 317s/tick turbo stage 2 cam and a custom kit with twin 6766s. I am looking to switch it up and go single for faster spool/better weight management for mountain driving.

Has anyone tested a single 6766 on a 6.0 and had any success? I have a feeling it would fall off quick but spool extremely fast. Does anyone think it would hurt the motor with all this back pressure if boost is kept fairly low? If so, would a 7875 have better spool characteristics while maintaining decent back pressure?

I was thinking of building the kit with the 6766 and swapping over to a 7875 if it isn't working well. My twin 6766 setup spools extremely slow.

stevieturbo

What sort of speeds/operating rpm range are you talking ? Surely once up in the rpm's any race car would be, they should be pretty responsive ?

And what sort of power are you after ? To even be considering a single 6766 vs twins, you must be willing to accept a huge reduction in power ?

And rather than remake everything, by far your easiest option for better spool would be a pair of smaller turbochargers..
It would be a simple bolt on swap without having to re-fabricate everything.

2005vetteTT

iTrader: (1)

they spool terribly - if i brake boost they are fine, but just getting into it, they won't full spool until 5k. i would like to be around 3500-4000 for spool to come in.

another reason i would like to go single is less weight, and better turbo placement. currently they are sitting behind the front tires (c6 vette, UPP style kit) and under high Gs the turbos have draining issues due to being so low. i'm running a turbowerx oil pump so there is no issue there. straight line and normal driving the oil drains fine.

power wise I don't mind losing power - just wanted to see if anyones attempted a single 6766 on a 6.0 and how it panned out.

stevieturbo

I'd hardly imagine brake boosting isnt practical or sensible when racing on a road course....would sort of defeat the purpose by hitting the brakes just for sake of building boost rather that accelerating.

Also seems a little odd they are so laggy, although for a stock LS2 ? seems a rather odd turbo choice given realistic power limitations the base motor would have. Just wayy too big..

Stick something like a pair of 5862's on it, or perhaps even smaller.

Are you T3 or T4 flanges ?

Closest you might find to anyone using a single 6766, is maybe someone with a single BW S366 or something but you're almost going from one extreme to the other there.

chuntington101

Agree with Steve, turbos are to big for your intended power goals. Do you still have the 5182 (I think) turbos that came with the UPP kit? They would probably be ideal.

Turbo'ing a corvette is difficult as there is no room and intercooling is hard. Single turbos setups are equally as hard as you single unit will have to be larger. have you thought about going for a supercharger?

You could also look at the TTI (although this robs your brake ducts - again not a good idea on a corvette) or a second hand APS setup (low mounted turbos).

IronBlocked

The cheap k04 turbos from ebay will light up like a switch, but they're a t3

DavidBoren

I don't think the trade off would be worth it, to go to just one of the turbos you have now. A single 6766 is going to choke that six liter with back pressure.

The extra back pressure isn't worth the faster spool, it's not.

Stick a pair of 5862's on it, like previously mentioned. At least try using the kit you have, just with smaller turbos. Especially before redoing everything.

2005vetteTT

iTrader: (1)

it's actually a custom kit similar to the UPP kit. I built it myself - the car was originally built for straight line (plan was a 408) and I've decided to go away from that. that is why the turbos are so large

The issue with putting a smaller turbo in its place is the draining aspect doesn't work under high lateral G's. even with the best external oil pump in the business it can't seem to keep up. i'm running restrictors and -10AN drain lines as well. i may be able to build a reservoir under the turbos to hold some of the oil in the times that it cannot pump but i would rather go single for the less moving parts.

sounds like I need to sell off the 6766s and grab a 7875 if i decide to go single. I just was curious if anyone had ever tried such a small turbo on the 6.0. I know the TC76 has a similar turbine so I wasn't sure if they would have similar backpressure or not.

FourG63 97GST

iTrader: (1)

I run a T4 PT6775 .96, drives like an n/a car + 200hp
TQ is over 500 from 3200-6000 and flat as a table top, and hp keeps climbing.

smallest single I've seen on an LS, it was for science, I think nailed it personally when it comes to all around powerband. lag is non existent, the downside is it probably won't make it into the 700, I expect it to tap out mid 600s

2005vetteTT

iTrader: (1)

that's awesome FourG63 97GST - exactly what I was looking for! I may look into getting something similar to that then.

stevieturbo

It sounds like most of the problems are self inflicted through poor design or choices, which means you just want rid of the kit and start afresh. I see Precision offer a new 6870 CEA unit. Still small as a single, but it should be a good step up from a basic 6766 in every respect and spool very fast.

Any oil scavenge issues certainly arent a fault of the pump if it's the Exa, but will be the design of your setup.

I guess another option is a built 427 lol

2005vetteTT

iTrader: (1)

yeah - could be. the setup is identical to the UPP kit so the turbo drains down and T's to the pump. then is pumped to the valve cover - not entirely sure what's going on but it doesn't like 1.1+ G's lol

stevieturbo

My own DIY kit has no problems so far pulling over 1G and I've no oil restrictors. I feed my turbos a lot of oil as that's what the manufacturer recommended. I use a single Exa.

From a cost point of view, seeing as you already have the 6766's may as well build a single kit around one of those, leaving room to go bigger of course. If it works for you all good and well, if not buy bigger.

Other than a new build perhaps removing any design problems with the current setup, moving to a single vs a well chosen pair of twins just seems like completely the wrong way to go though.
Of course you could end up creating new problems too.

If you're really happy about accepting a huge power reduction over what 6766's had to offer then you'd probably be better off with a centrifugal blower

DavidBoren

I would figure out that scavenger pump routing, first and foremost.

But if you want to change your set up, regardless, then a centrifugal blower is definitely something to look into.

chuntington101

Is that using the Hinson (spell?) kit? Modes versions of these kits have managed to fit upto a 88mm on c5s but don't think they do a C6 kit.

I still think a low mount kit with small turbos is you best way forward. I think you can still get If to can get a set of APS manifolds you can still get housings from precision I think.

2005vetteTT

iTrader: (1)

How high do your turbos sit? Mine only has about 2-3 inches of downward travel until the drains flatten out and then the pump pulls the oil up. i'm sure i could get it working with revamping how my drains are but there still is the lag.

i'll probably take your suggestion and build a single kit and see how it does. honestly the single kit would only cost me $200-300 in materials tops so not too big a deal.. i can just sell either kit i decide to not use after the fact. C6 guys will pay too much money for a turbo kit

stevieturbo

Bottom of compressor is only a fraction higher than the base of the oil pan. So pretty much as low as they could be on my vehicle

I have no downward travel on the drains at all, I had to make a small chamber from 3/4"x1.5" aluminium box section create a drain of sorts. There is no gravity drop whatsoever because there is no ground clearance.
The 3/4" is on the vertical plane. I wouldnt have had room for a AN style fitting or elbow on the turbo

chuntington101

Steve can you post some pics of your setup? I'm pretty sure similar thing has been done on a corvette so might give the OP some ideas.

Wnts2Go10O

iTrader: (12)

2 smaller, well matched, turbos. sounds like you need to figure out your drain issues.

stevieturbo

You can just see the drains. Small alloy box below turbo, linked to 5/8" rubber hose into a 5/8" OD alloy tube which links both turbos.

I tee another 5/8" alloy pipe out of this just directly beside the oil pan on the right side of the vehicle, and the scavenge pulls from this low location.

Doesnt look pretty, space is absolutely non existent but it works perfectly.



But aside from right side turbo compressor, almost nothing sits lower than the base of the oil pan itself.