[itschristorres8]

Alrite next summer im building my engine. boring it .4 over 4.2L, and forged SCAT connecting rods, Forged pistons and new steel crank.

only thing i cant figure out is what i want my Compression ratio
i plan on running about 15psi on the street and 20-25psi at the track.
i dont know which CR i wana choose

8.2:1
or
8.5:1
or
8.7:1

im looking for 10s and with that much boost i know i'll reach it. i just dont know which Compression ratio which would be better i thought 8.7:1 would push me more power and they're forged so im wondering if that'll hold well enough
or if i should drop down to 8.5:1

and if i do a lil 50 or 75 shot im guesing 8.2:1 is the best way to go.

[itschristorres8]

bump?

[TurboLX]

if you plan running nitrous, a good 8:5.1 or 9:1 would e fine

[Darrell]

9:1. There are plenty of engines with compression ratios in the 9:1 area that run boost in that range. Your best bet is to talk this over with the engine builder.

[SWEET2KSTANG]

also depends on head unit size too.

[TurboLX]

Originally Posted by SWEET2KSTANG also depends on head unit size too.

[itschristorres8]

i'll be building the motor

for the rotating assembly i just cant decide...most likely i'll run some nitrous...my MAIN goal is to do 10s with a pt67 instead of what i have now. like mid 10s.. 10.4-10.6 area then if i get bored of that spray

i think im going to settle with 8.5:1 though most engine builder for v6 that do big boost motors are saying they're doing

but im looking fora safe daily driver

[TurboLX]

then you wont be able to run a big shot of nitrous

[itschristorres8]

i dont wana run a big shot
with 20-25psi im not tryin to run 150shot

most like 50 75 or 100 shot at 20psi
depends..if i hit low 10s with 20psi i may just try to do 9s with 25-30psi if not get some giggle gas...i just wana run 9s once say i have a DD v6 that hit 9s =)

i see more mid high 10s though at 20-25psi
i'll see...

[Onemanzu]

compression ratios don't affect nitrous as much as it does boost...

i say go with 8.5

[SWEET2KSTANG]

Originally Posted by TurboLX Originally Posted by SWEET2KSTANG also depends on head unit size too.

volume, running 20+ psi with a bigger head unit is a lot of volume. just a part of planning the build. i seen v6's with stock bottom ends go 10's. easier and safer on a built v6. you can run nitrous on a lot of compression, will just have to have the proper set up for a big shot. big boost with especially with big head unit, low compressions.

[Goblin]

By "big head unit," i assume you really mean compressor size? If thats what you mean, then your right.

[itschristorres8]

the heads will be CNC heads not sure if i'll go bigger or not. theres only one set of heads that are better which have bigger valves and i believe just as much volume in each port.

i think i'll stick with 8.7:1 or 8.5:1 lol probably 8.5:1 incase i go for 30psi...idk if i'll do nitrous if i do it'll just be off the line or just to spray after 120mph...or 130...i believe most 10 second traps are about 130-140 if im correct...my car as of now with this T-5 is HORRID in 5th gear. 3.55 gears in the future might not be a good idea since i plan i just getting a g-force dog tooth rebuild kit and rebuilding my tranny to g-force t-5


i still have a while i wont see 10s till end of next year

[SWEET2KSTANG]

Originally Posted by Goblin By "big head unit," i assume you really mean compressor size? If thats what you mean, then your right.

yeah. head unit, compressor, etc. but that is what i meant.

[itschristorres8]

Originally Posted by SWEET2KSTANG yeah. head unit, compressor, etc. but that is what i meant.

in that case
the next turbo will be a pt67 with a a/r of .84
for my car its a pretty big sized turbo but decent for the 550whp im looking for
15psi has made 503rwhp. im looking for at least 20psi at the track maybe 25
so 600 at the wheels maybe be seen. i wont know til it happens

[SWEET2KSTANG]

with that big of a head unit at 15+ psi, the compression needs to be low. that is a large quanity of volume, and will equal a lot of lag. i suggest ceramic coating and wrap. the 3.8 will take a lot of boost stock as long as it is intercooled. there are guys running t4's and t56's at 17psi on a stock bottom end running in the 10's. personally i would suggest twin t3/4, or t4's to help with lag and will make same amount of power.

[itschristorres8]

Originally Posted by SWEET2KSTANG with that big of a head unit at 15+ psi, the compression needs to be low. that is a large quanity of volume, and will equal a lot of lag. i suggest ceramic coating and wrap. the 3.8 will take a lot of boost stock as long as it is intercooled. there are guys running t4's and t56's at 17psi on a stock bottom end running in the 10's. personally i would suggest twin t3/4, or t4's to help with lag and will make same amount of power.

theres 1 guy onthe stock block and top end running that. he's run the car twice and thats it just to make 10s
im using a t4 flange. GT40R turbo for another guy made 503rwhp all peak though.
the engine will be set up to redline around 6k...so once in boost i really wont stay out. all but one v6 guys making 10 second passes are using big single turbo set ups. my pt67 may seem big but the guy running 9s is upgrading to like a t80 or something

i should start boosting around 2500rpms-2600rpms, full boost around 3100rpms...=/ not the best but when it hits im flying. im considerin .7X a/r just to boost a lil faster but i doubt it. might just spray off the line a lil 50shot

so im guessing i should stick with the 8.5:1 compression ratio

[SWEET2KSTANG]

i have seen more than 1 guy go 10's on a turbos and stock block. i was in a discussion with a few guy quiet a while back about their mustangs and their set up. most of them were 11's and 12's, daily driven cars. 8.5:1 compression is in the range for your boost wants.

[itschristorres8]

well the newer stangs are more impressive

[Avaric3]

Originally Posted by itschristorres8 i dont wana run a big shot with 20-25psi im not tryin to run 150shot most like 50 75 or 100 shot at 20psi depends..if i hit low 10s with 20psi i may just try to do 9s with 25-30psi if not get some giggle gas...i just wana run 9s once say i have a DD v6 that hit 9s =) i see more mid high 10s though at 20-25psi i'll see...

a 50 or 75 shot of nitrous when your deep into the 10s will barely take off a tenth or 2 if that, anything smaller than 125 is a waste at that point imo