Need More Boost
 

Hi guys, yes this is my first post, but ive been lurking around for a while. Anyways like the title says im in search of making more boost. My current car/setup is a 550hp 383 stroked 1996 Chevy Impalass with a D1sc procharger seen only 11-12ish psi.

Most of my wifey approved money went to this set up but after running like this for a few years im getting bored with it. So ive been thinking of selling the supercharger along with accessories since i wont need most of it and going twin turbo instead. Im thinking of twin rear mounts so what turbos will be best fit for this goal. Im looking into making upper 800hp, my budget is 1,500$ to max 2,000$ since i have most of the supporting mods already done to the car.

Thanks guys.

thats a very large hp goal which should be easy but expensive. i would recommend twin gt35 turbos but there 1500.00 each. 800hp goal i can only assume the engine lower is already built for it so your next issue will be fuel supply. you will need to invest in a larger pump, injectors and a custom tune. i dont think a 2000.00 budget is going to work.

Well yes the motor has been built with some good quality parts as in

Callies Steatlh forged crank, 3.74" stroke
Oliver Parabolic 5.7" rods
JE 31cc dish forged pistons
Walbro 340 pump
Msd voltage booster
50lb injectors
Currently hitting 12psi with the supercharger so im just looking to make atleast 18 psi im assuming i would need 80lb injectors to get this to happen but the only good news i got is that the tune will be cheap for me since im a returning customer. But i found twin turbonetics BT3-T04B H-trim ST63 turbos basically new for a good deal on cl. All input and advice is greatly appreciated.

I would definitely go bigger on injectors. What type of fuel you running? There are a lot of guys making lots of power on E85 nowadays. Just have to be tuned for it. But also have to have correct sized injectors and flex fuel pump. Assuming you have E85 in your area...

sounds cool
a few questions
what engine do you have? I realize its modded but what did it start out life as?
what cam is in it right now?
are you willing to go front mount turbo?

now I wont fault you in going rearmount however, its easier to get to your goal with front mounts with larger turbos that will retain heat better. I have a rear mount turbo setup currently but for the power you want, front mount twins would be a better a better choice simply for simplicity's sake. If you really want rearmounted twins, its doable, your st ognna have to size the turbos ailttle differently and also have to fabricate alittle more in the project. I will admit, rearmounted turbos just sound awesome, something lost in front mounts.

Anyway,
Twins, either fron or rear would be the best route. for 800hp, your gonna need at least 80s if not 85LBS injectors. im not sure about the 340 pump but you might have to run twin 255 walbro pumps if not triples in staged form to come on at specific boost levels. Generaly when you setup of a boost setup, you want to be able to over fuel up top in case you run into a lean condition. better to go rich then detonate. WIth us V8s, you have plenty of torgue. don't go too crazy though on the dished pistons.
Honestly, since you built the engine to handle boost, I would have kept the pistons flat and have the heads control the CR and actually the more initial CR you have, the better initial torque ou have, hence I kept my stock LS1's 10.1:1 CR and its running with 10psi boost.
WIth that said WATERMETH!! do it and with it, largest intercooler you can fit behind that bumper. The dence cool intake charge will keep you motor happy with either front or rear mounted. Contrary to belief, you can still blow your motor even if its forged. all it takes is one hot IAT, poor fueling and timing and watch the metal fly...

Reason I bring up block and cam is to get a better idea of what you have al together so I can see which direction you can go. if you have a LT1 (old school lt1) or lower grade motor, your gonna have to do more prep work to handle 800hp.
If you have an LS style motor, you have a much better stepping stone that also like to be revved more then the old school chevys.

with that said, tuning will be our next hurdle, and if you go rearmount, this will be the hardest thing to get right since spool is gonna be directly related to heat and if you have rich tune, the exhaust will be cooler then if it was leaner. its a delicate balance.

Also, what is your altitude and average temperatures like? this also has a HUGE impact on rearmount turbos. the higher the elevation the harder it is for a larger turbo to boostl with the thinner air. Rear mounts are very sensitive to this since the charge is already cooing on the way tot he turbo in the exhaust.

good luck on your build and cant wait to see how it goes. Im not trying to scare you away from rear mount turboing, I just want you to know that if you do, its gonna be alittle more work to get it right

Thanks Joshua for the information....

Im not looking to dropping allot more money for the rear mounts i honestly thought it could be a little price friendly doing those since i wouldnt have to move allot crap around and these turbos fit in so perfectaly underneath my big boat.

Well im in the Dallas Texas temperatures are an average 90-100+ in the summer and for the fall through winter ranges from 80-60 we might see temperatures go down to about 30degrees for a few weeks in Jan-Feb. Our elevation here is at 430'
To answer a few of your questions bout my motor i have a built 96 LT1 with the following:

Engine:
383 LT1 block
Callies Steath forged crank, 3.74" stroke
Oliver Parabolic 5.7" rods
JE 31cc dish forged pistons
King Allecular bearings
Speed Pro plasma moly rings
LT1 iron heads, ported, 2.00/1.6 valves
Comp Pro stainless roller rockers, 1.6 ratio
Comp one piece hardened steel pushrods
Titanium springs (do not remember pressure)
Comp screw in rocker studs W/plates
Comp 224/230 114cl cam
Stock LT1 intake port matched to heads
ARP head studs FelPro .040 head gaskets
Delphi 50lb injectors
Aeromotive adjustable fuel pressure regulator
Walbro 340 fuel pump
MSD 6a ignition
MSD fuel pump voltage booster
Holley 58mm throttle body
LT4 double roller timing set
Procharger D1SC blower head W/15psi pulleys (most boost I have seen is 12psi)
Custom intake tubing with twin core cast intercooler
NGK TR55 plugs
I have always run Valvoline 10w-40 oil, 10W-30 in a pinch

Trans:
Bernard Tripp built Stage 3 vacuum modulated trans, built to support 700hp
Edge 9" 3200 stall converter with a 2.5 str

Driveline/Suspension
Inland Empire 3" aluminum driveshaft
Clear Image safety loop
Clear Image tubular transmission crossmember
Hotchkiss billet rear lower control arms
H/A rear sway bar
2nd gen F-Body front bar
9C1 body bushings
Eaton 400lb rear differential with Yukon 3.73 gears
Performance friction front and rear linings
Air Lift rear bags (individual valving, valves on either side of the fuel filler)
Custom bent/welded roll bar.


I have to do some heavy reading on what a few other guys ar running with twins as far as fuel support goes. But ive seen a few guys run a similar setup and push out about 700+ but ill do a little more research on it

Good setup already! sorry if I made you sound like you didn't know what your doing. Your pretty much already there dude!
Alittle more fuel and you pretty much already there. Afew things to consider for you.

Im not sure how far your 340 can go, but id have a secondary 255 walbro boost pressure activated to kick in to help keep your upper RPM happy. Also, 80lbs at a minimum if not 85s, just in case.
Also, not sure how far the MSD 6A can handle, but id look into an LS1 coil on plug conversion kit. LS1 coils have been known to handle 1000hp.
Also, not sure of your Compression Ratio, but id look into some aluminum heads that will have your CR between 9.1 to 9.5. That way your low end doesn't completely go south. when you go turbo, you are completely dependent on that exhaust and that nice near insta-boost wont be there like it was when you were supercharged. the smaller twins wil help, but if you go rearmount, its gonna dog bad at low RPM.

invest in Water/methanol injection and a big ass intercooler. As big as you can fit between the fenders. even if you go rear mount. Snow performance at least. Alky-control if you got the money.

Glad you have a 3200 stall. that helps with spool
whats your final drive ratio? that's gonna influence spool greatly too, especially in rear mount form.

Everything else is damn near ready for turbo.

A few rearmount turbo related info if you do plan on going that route.
LT headers are a NO-NO, Shorty headers if not stock manifolds (heat retention is key)
smaller exhaust. 2.5" tubing is where its at.
WRAP EVERYTHING, from the turbos all the way up to the headers.
Keep the AR's in the .81 to .96 on the turbine side to get spool online faster, from what it sounds like the turbos your getting seem like they are right up in that ally. NOt sure if they are on the small side since you have a 383 but its a good start.
IM running a T76 .96 AR on my stock 346ci LS1, no flow issues there lol
just to put it into perspective, a guy on LS1tech had a T88 on his rearmount ls1 style Camaro and was running 10's with 2.75 rear end gears and complete car interior. he also did a spool valve mod to the turbo to spool it like a little 60mm until a set amount of boost. but that's out of your budget right now. its possible to get a rear mount to scoot. just takes a little more prep work.

Im starting to lean closer to doing front mounts now the trouble is finding some decent turboheaders for my car. if you know of where i can find some let me know.

Im also helping my brother with 73 camaro hes got a twin turbo front mount kit from ebay i believe the seller was CXRACING and its going on a forged 383. The problems hese come accross was with the header the bolt holes not lining up right so hes got to do some welding on it.

Where do most of you guys pull the oil from to feed the turbo. I originally thought going of the side of where the filter mounts up was good but ive read allot of bad things going that route.

I'd use a T on the port beside the distributor to feed the turbochargers with oil. Be sure to use inline restrictors to slow the flow of oil. Where are you planning to return the oil?

ok thanks, where planning on tapping oil pan 1/4 from the top. As for my motor its a newer sbc wheres the safest place i can pull oil from ? IVe read somewhere that its not a good idea to use the ports off the side of the oil filter.