Here's the quick down and dirty. I have a 408 with 317's and forged everything. Currently running twin 70mm turbonetics with journal bearings and cast wheels. The car makes 800+ whp with pump and meth @16lbs, through a 9inch and 6 speed. Does anyone think 6466's would be too small for that motor. I rev to about 6200 and currently the car has to much lag for the street. I was told by a precision guy that those turbos should be fine to about 1200 whp and that for my power goals (around 900-1000 whp) i wouldnt gain anything going to the 6766. Any input is greatly appreciated guys.

 

No, the 6466's will make more power everywhere than the twin 70's you are running now. You will be adding fuel everywhere to your tune up.

What A/R EH are do you have on there. If .96AR or bigger you are good to go.

You could make 1000 on pump with these guys. They are incredible.

 

Currently the turbonetics are a t4 undivided .96 I believe and when I get the 6466's they will be a t4 undivided .96 also

 

They will be significantly faster then the turbonetics. Is your fuel system up to snuff?

 

Magnafuel protuner 750 series 4303 and my injector duty cycle is currently at about 50-60% duty cycle.

 

I've come to notice that on this site you get more Feed back from people by talking **** about a product then you do by just asking for input. So on that note, precision turbos are garbage and that company should be put out of business!!! Who's with me?!?!

 

I've made 900whp on a 4 banger @ 50 psi with these.

******* LOVE big boost on a small motor, so I assume they will flow well you us int he low 20's. They will make more power everywhere, but cost 4x as much as your current turbos.

 

Does any one think 18-20 lbs would be to low, that's kind of my limit with the 317 heads, I know boost is a relative number just looking for some different perspectives

 

.96ar exhaust housings are the reason why you have too much lag. you need to step down to .68ar's. What size is your turbine wheel? I would go with either Turbonetics 6665BB or 6466BB with HPC billet compressor wheel. Precision turbo is just way overpriced IMHO, but if you have the means for their ball-bearing units with billet compressor wheel, then go with Precision if that's what you want. GL!

 

Having tried 6266 and 6466 with 0.58, 0.68 and 0.81 housings on 4 cyl engiens, I can safely say there is negligible difference in spool between them, and a nice difference in power

As long as you arent looking to make 25-30psi boost with the 408 then I dont see you having any problems at all and you will have no problems making well over 1000hp

On a slightly better budget you could go for the BW S364FMW's like I have, almost same dimensions compressor albeit with BW's 68mm turbine wheel.
Perhaps a little loss in spool and transient response between the Precision and the BW, big difference in price and no worries at all about reliability.

You could even step down to a 6266 or the BW S362FMW's for a little better spool but on a 408 I really dont think you'd have a problem.

Under exactly what conditions are you suffering poor spool, and what sort of rpm etc are you making boost at, or making full boost at ?
Mine's only a 382 and I'm quite happy with mine under 98% of circumstances.

 

Somethings wrong if a .68 doesnt outspool a .96 lol

6466 are fine. If your only looking for 18-20 psi 1000 hp or so, i would run .68-.81 a/r for faster spool on street. Should be nicer with the 6 spd

Your current turbonetics should be better off with a .68 to .81. I would do that first if you dont wanna spend money on new turbos

My 72 mm turbonetics with 68mm turbines spool faster on .81 ar than my 7065's that had a .96 ar

My old 6065's with .68 were instant boost. 7065 with .68 was only tad slower spool than the 60's. Ar has alot to do with spool

 

Yes, off boost it is also completely choking the engine making it very lethargic. A/R IMO plays a much smaller role in spool than people think, perhaps even less so on larger motors although the ones I tried were all on a 2.35

The larger housings on the same engine were noticeably better everywhere, even during normal driving.

Smaller isnt always better in terms of spool, if there isnt enough energy to actually drive the compressor to make boost which presumably is what was happening at lower loads. I'd say with a much smaller compressor it would be a very different story though

 

ull make right around 1k wheel with those

 

Something sounds wrong with the motor if its getting choked at part throttle. Perhaps an overly sensitive design to exhaust restriction. Most v8's dont seem to respond that way. Everything i see from srt4's to lsx v8's and 2jz's all show differences in power under curve and spool time when looking at a/r when turbine wheel itself is adequate for the application and compressor. The physics of it make sense

 

On pump. On E85 set on kill with a motor to support he would make 1500whp easily.

 

even on pump fuel, 1k+ would be a doddle.

With right build/CR etc, I dont see why it wouldnt do 13-1400 on pump.

However, as much as it's a great unit on smaller engines and I've used it to near 40psi boost, I'd be concerned about pushing them very hard on the much larger motor simply because of Precisions reputation and the turbo is operating under very different conditions trying to feed the larger motor.

For the price of them and if spending that sort of money wanting BB units, I'd be inclined to go for a pair of EFR's

if not, just a pair of Airwerks or the SXE's at less than half the price.

 

I would like to see the backpressure readings on that. 66mm turbine might be getting alittle small at that amount of exhaust flow. It would be a pretty impressive comp wheel to pass that air flow.

 

I'm 1:1 with the 68mm turbine up to both 25psi and 6000rpm.

Even above either of those, it's only a little over 1:1 manifold pressure vs boost.

The Precision 66mm wheel is thinner and freer than the BW 68mm on mine so I'd have no concerns at all about backpressure even with the 408.

Some of the big singles would be running far far higher.

There's a guy over on YB who's made near 1800hp on a pair of 6266's, although he's on methanol.

 

u guys are saying these stupid *** numbers.... my dads 6266's ball bearing water/oil cooled make around 850 on 22psi and he's pump with meth.. also a 416 ls3... of course a smaller motor will result in more boost and more power because theyll flow more, but goddamn 1500 and 1800hp........ please show me where thats happened with that size turbo. all you guys are high as hell.. twin 76's? yeah i see 1500 onna 416 to 427 inch motor on like 30-35 psi.... thats what it takes for that much power... and yeah those 64's run 40psi.... but they will not push that mch on any decent size ls motor.. theres just not enough turbine..

 

Lol i was thinking same thing. They will do 1000 but more than that i would have thought was running them hard