ltonenewbie

i have a fully forged 396 LT1 with ~10.4:1 compression (originally built for nitrous)

i'm pretty much dead-set on doing a Rear mount. i'm just undecided on which turbo (something i can make 800-1000whp with later on, after i drop compression)

i don't mind a late spool(i prefer MPH over ET) but i also don't want extreme lag. so.... PT88? TV or GT? GT91? stay T4? i just don't want to have the same spool issues that Zombie had, figured i'd post before bugging Longrange4u.

ltonenewbie

some details:

396 ci LT1(4)
10.4 CR
yank 4000 SS
shifting just before 7000
makes around 425whp NA through stalled 4L60E with a low lift, 24X/25X custom HR.

willing to change whatever needed to go the turbo route, was hoping i could do 10-12psi for now & not hurt anything.

warriorcustoms

iTrader: (10)

There is a Forced Induction Section LoL I think a rear mount with a turbo that big Isnt gonna cut it DO a front mount So itll spool up & with a compression in the 9.4 range Ive been researching Twin Turbos myself!!!! But Ive decided to finish my 396 Nitrous build instead Since it will take another 3 to 5k

F0x Slaughter

There is a formula to figure out what turbo will work for your engine.

It basically goes:

CI x RPM x .5 x VE / 1768 = CFM

Boost Psi + 14.7 / 14.7 = PR Ratio

PR * CFM = CFM under boost

CFM * .0691 = Lbs/min

Then look at a compressor map.

So 396ci x 7000rpm x .5 x .9 / 1768 = 705cfm

12 + 14.7 / 14.7 = 1.81 PR

1.81 * 705 = 1280cfm

1280 * .0691 = 88lbs/min

So now you can look at a compressor map and see where 1.81 falls for the PR and where 88lbs is.

So looking at a compressor map, a T88 would work great on your engine.

I8ASaleen

iTrader: (9)

You'll need to change quite a bit to go from nitrous to turbo. Cam, pistons/heads for lower comp, tranny if you want 800hp, and of course all of the turbo components.

Puck

iTrader: (17)

Keep in mind that formula is just based on theoretical flow and doesn't compensate for variables like turbo distance from head, which will have a big effect on spool time.

From what I understand, on a rear mount setup you usually want to size the turbo slightly smaller to reduce lag. On the positive side though, you usually don't need an intercooler since the extra long cold side acts like one.

For a stock/bolt-on car a rear mount may make sense for its ease of installation and simplicity, but when talking a 396 with your goals I would strongly consider a proper front mount setup.

F0x Slaughter

Thank you Puck for the reminding me about the distance from the head ect.

Heat helps spool a turbo, by having a turbo remounted its not getting as much heat as a front mount would. So I would have to agree a smaller turbo would produce a quicker boost threshold.

ltonenewbie

thanks guys, like i said i'd obviously be dropping compression before upping the wick later on. and the 4L60E is built.. if it went i have a 1200hp TH400 available.

i'm sure a different cam would be optimal. but that's where i'm at... choosing the biggest rear that i can still spool by a reasonable RPM.

lttransam

iTrader: (12)

oh wow, that a lot going on... i think you should do my motor too lol

F0x Slaughter

Kyle I put it on a post on MiF all you have to do is go under the Power Adder section and look for choosing a turbo using compressor maps.

Stop being lazy =P