adam1803

iTrader: (65)

Just like the title says. I've been researching what CR i should shoot for on my new motor (forged 370) and i know it would be fine at 8.5:1 but i just feel that it would be too sluggish when not in boost. So i was thinking 9:1 should be a bit better but still handle a decent amount of boost. What are your thoughts? Thanks

2004SSS

iTrader: (25)

ive almost got my 370 finished im going to run around 9.5-1 cr , i havent ordered head gaskets yet though so i have little play. like you said i dont want it to be sluggish when not in boost. and since i dont plan to run it with 15 psi daily i can use race gas for the track. i will run close to 12-13 psi on the street. im also planning on using a good shot of nitrous(150) with the higher boost though.

TURBO8

iTrader: (9)

I think 9 to 1 is perfect. IF you are going for 15 psi.

quicksilverado

iTrader: (8)

My old 370 setup had a cr of around 7.8-1 and it had more bottom end when out of boost than the the stock 5.3

8ALTNG

iTrader: (1)

I would suggest going 8.5:1 with that kinda boost. It would take it better and last longer.

parish8

iTrader: (6)

i dont think it matters too much. you will probably need meth or race fuel to get to 15psi with either ratio.

Spoolin

iTrader: (8)

Just out of curiousity why would you say that? I realize there are a crap load of factors involved but why couldn't he hit 15psi? Just curious because I'm building a forged 370 as well and was planning on the same if not a bit higher boost. I am gonna be running meth but was just wondering why he couldn't run that high without meth or race fuel. Too high of intake temps, pre-det, engine can't spool turbo enough?

parish8

iTrader: (6)

i think it has something to do with cylinder presures but there are a ton of factors and i dont really know how it all works. i do know that 15psi is a lot.

on a stock lq4 you can typicly goto 6-7psi without an intercooler on pump gas

not 100% sure on this but i think a stock lq4 with an intercooler would add about 3psi to that so about 9psi is a safe limit on pump gas.

now drop the cr .5 to 1 point and that would probably add about 1-2psi more on pump gas. that gets you to 10-11psi.

spray some meth and get another 4-5psi on the same pump gas. that gets you up to around 15psi.

these are real word examples i have seen on the street with diferent set ups. there have been a lot of other factors like a cam swap or more cubes but i think it is prety acurate overall. there is just a limit to what you can do on pump gas.

TurboBerserker

iTrader: (1)

I don't know about 3 psi from the intercooler -- guess it depends on the intercooler efficiency and flow, but I've seen applications that add 5-6psi from the FMIC on LQ9s -- for a total of 11-12psi.

Swap in the right cam, though, and you can get higher boost.

I'd be running meth at 15psi, personally -- hard to argue with the benefits for high boost.

03sierraslt

iTrader: (22)

I ran my old setup at 8-10lbs with no intercooler and pump gas for about 1.5yrs, wasnt getting much timing 12-13deg. So far I am running less boost with the intercooler just because of the fact that I like the way it runs. Lower boost level but still more power the when I was at 8-10lbs. This is on a LQ4