valsperformance

iTrader: (2)

I have 2 garrett 67mm journal bearing turbo's or one dual ball bearing 80mm at the shop. I would like to run around 15psi. Any input? They are going to be rear mount.

99Z28LS1

iTrader: (4)

there are some people running a bigger turbo without that big of a motor so i would day run an 88 or something........ but you dont have that so i would "think" that the twin 67's would work better

valsperformance

iTrader: (2)

Yea, I believe that the twins put me smack in the middle of the compressor map. That is if you are supposed to 1/2 the air flow for twins? It's just the extra cost involved and the single is already set up on the truck.

smokinHawk

iTrader: (48)

what 80mm is it
T6 flange?
what AR
if the AR is small or a T4 flange go with the twins

DrTurbo

iTrader: (3)

I would go S85 or S88, but that is me. They are compact in size compared to the thumpers and GT47/55 units and will easily support a 408.

RealQuick

iTrader: (14)

Go with the T80 T4 since its rearmount setup. Even with the cubes, you will have the normal lag of rearmounts, but the cubes will help. If the T80 is a restriction, then you can upgrade to a T88 T4 turbo.

valsperformance

iTrader: (2)

Because it is a rear mount and I mean way back there, I was thinking that the 80 would spool better also. It is an ITS 80mm dual ballbearing with a .96 A/R housing. I think the twin 67's will definately work better through the whole range. Does anyone know if you 1/2 the airflow when reading the compressor maps when setting up twins?

RealQuick

iTrader: (14)

Yes you do. Think about it this way, only 4 cylinders are feeding the each turbo. So halve your airflow consumption to spec each turbo.

valsperformance

iTrader: (2)

I figured but wasn't positive. Thanks....

Zombie

iTrader: (2)

I can offer you a little insite on it since I have a 370 and run an ITS DBB T76. Does your setup have the R,X, or Q trim turbine, hopefully the R.

I've found that for my setup the .81 a/r works the best for spool and drivability. I have a .84 housing for an R trim I can sell cheap if you would like to try that as well in your application. My setup doesn't spool quite as fast as I would like but it gets the job done. Honestly if it spooled faster I'd never get any traction on the street, it still comes loose on me from a highway roll (70 mph) pretty often, even on nitto drag radials.

I'd say the single 80mm is going to be your best option. The twin 67's would probably spool considerably slower. Their major downside would be if you ran dual exhaust. Dual exhaust = a lot more surface area to lose heat from vs a single pipe. Dual 2.5" pipes vs a single 3" pipe would have over 1.5x the surface area to lose heat from.

valsperformance

iTrader: (2)

Excellent point on heat loss. I didn't even think of that. The 80mm is actually a 72 now and would be sent to them for an upgrade. Justin at ITS recommended there new wheel which I think he called an XR trim or something like that. I just keep looking at the maps and the 80 is a little smal for airflow. The twin 67's are in the sweet spot. Do you think the 80 can make 900hp at the crank?

Navy David SS

iTrader: (13)

You need to front mount them. Twin-67's are great on a well built 408, with the right heads and cam.

Here's a picture of my twins on my 408 iron block. On 14lbs blew the tires off at 890rwhp . Figure with 18lb will be easy 1k rwhp. There's a lot more pictures on my car's site in signature.



David

valsperformance

iTrader: (2)

Very nice, did you vent the crankcase with that one breather? That is another issue that I was working through with this set up.

Zombie

iTrader: (2)

X trim is a R trim that has been back cut to reduce the exducer is what Jose told me, less flow.

Another option you should consider is selling your current turbo and getting something custom from forcedinductions.com. I know when I talked to Jose last he said there were some new things they were doing with the new extended tip wheels and newer turbine wheel designs.

I'd say 67s in the back, bad idea. 67's in the front, good idea if you can make the sacrifices required to fit them. Turbo's will always work better when they are closer to their energy source.

valsperformance

iTrader: (2)

I could move everything up front but this year I am commited money wise to keeping it in the rear. The 80 will work great but I know it will run a little short on the top end. I guess I'll just keep my original plan with the 80 this year and consider the two 67's up front next year.

STP

i have a 408 with twin 67 dbb front mount made 870 at 12 lbs drives nice on the street 18 lbs made 1060

HitmanLSX

What octane on the 12lbs? and is that Water I/C or air air?

Pro Stock John

iTrader: (34)

val what kind of car?

Navy David SS

iTrader: (13)

The pictures doesn't show 100% as the car sits today. Had to add another vent tank for the driver's side also. So 2 tanks one for each valve cover.

David

valsperformance

iTrader: (2)

The set up is in an 03 Escalade EXT. 6200lbs with me in it. 408 stroker, 4l80E conversion w/ SS silverado t-case, stage III Ls6 heads, custom Vals turbo cam, lowered for better weight distribution, and alot more. The truck ran 3.3 0-60 times on the street tires. We couldn't get her up to the track yet to get a 1/4 mile. All on the 72MM turbo that was on it before we decided to go all out in this thing. Very cool truck, should be finished with paint and all in a few months. At least for this season.