Dragframe

iTrader: (14)

I have bee talking to Phillip Bridges for awhile now (so of you may know him or know who he is).

Now he has a turbo LT1 Trans Am that he was running the lt1 forever and now to a dart little m.

His theory is opposite of what you most drive for when putting together a F/I setup. The title states it. What do you guys think?

Im not giving exact specs but .... running something like 10.2ish/1 with something around 16psi (on pump) and timing like 12* on a smallblock. Thats not very much timing for a SBC

He has ran something in the area of 8.82ish the other weekend ( i think) on his race gas tune... trapped i think a best of 176 or something mph...

Oh... and still on the same plugs as last year... looking good

so whats your guy's opinion...

Got Me SOM

iTrader: (2)

8.82 @ 176? Is his car not hooking?

hellbents10

iTrader: (10)

There is many variables to account for. When it comes down to it, cylinder pressure is key. Where, when, and how much you have at any givin time (rpm). If he is running a cam that lowers dynamic compression a lot he can run more boost on pump with high static compression. This is just one of a million variables on a setup though. I have made some big power with boost on pump and high octane. On stock L31 vortecs I have made big power on boost while running 12-14 degrees of timing (under boost)on pump and having them live for a long time.

mulot30th

All I can say is its possible...

I have a Yamaha apex sled which I turbo'ed last winter and ran up to 18psi on ... stock pistons/rods...

Compression ratio is 11.8-1 and I am running stock timing on that thing.

Only thing is I have to run strait C16 to avoid knock.

287hp out of a 1 liter engine

Zombie

iTrader: (2)

I believe RPM plays a factor in this as well due to dynamic compression. High revving slow spooling small displacement engines like bikes can run turbos with 11.5:1 compression because they spool late and have less peak cyl pressure vs a large displacement fast spooling setup.

Someone correct me if I'm wrong.

mulot30th

In this case a 11K rpm redline engine... but even a 5-6K rpm... it had 17-18psi of boost on the dyno

Torque is about 180% of stock torque all the way from 5000 rpm to 10500rpm.

But peak cyl pressure increase by about 20% only (assuming no knock) but that should be the same thing with our LS1/LT1 engines.

kp

iTrader: (34)

Higher elevation can use much higher compression, even with pump gas.

I'm not going to get into the compression debate again, there is no clear winner IMO. personeally I'll take the higher compression/less timing approach but some choose otherwise with great success..

mulot30th

Need good gaz too!

And... need to keep heads tight on the block too. but definitely high compression works with boost.

MIGHTYMOUSE

iTrader: (59)

whats low about the timing? not much off from what i run with 8:1 compression

when my timing was totally wrong (like -10* at full boost) i was able to crank the boost up, but it never made **** for power compared to less boost more timing.

ATVracr

iTrader: (5)

He is talking about a traditional SBC not an LSx based SB.

They usually run a good bit more timing then we do on the motor.

2kredss

iTrader: (1)

i've been thinking about this whole thing for a while, and everyone talk to thinks its a horrible idea, i think it would spool faster, the car would be more responsive. but i might be wrong

mahhddgtp

I would prefer to keep my boost low; however, if I had a nitrous setup, I would spray a lot and run low timing...

TRMN8R is my influence on that one.

Dragframe

iTrader: (14)

he said it does spool fast and runs good.

MY99TAWS6

iTrader: (3)

Usually boost makes more power than timing. And leaning out the afr. So running higher boost with reasonable afr and low timing can work. Lowering timing really seems to take away torque. Which can be a good thing maybe to save the drivetrain,rear end. It is debatable wether high boost and low timing or higher timing and lower boost are really that much different. The higher timing can make the car feel faster since as said the torque really can come up. I guess we need someone to come on with dyno graphs that has tried this. Mostly this is a pump gas or high compression issue. Run high enough octane and you should still get high boost and high timing and leaner afr.

Got Me SOM

iTrader: (2)

fwiw my car felt a lot stronger at 10:1 compression than it does now at 9:1. If I decide to keep the car I'm gonna heads milled to bring the compression back up.

definitely had a lot more torque especially down low and the car felt snappier.

VTC_WS6

iTrader: (9)

Gotta love Static compression.

Lythropus

iTrader: (13)

I'd like to know more about this also, seems kinda strange how 1 liter bikes can run 10 lbs of boost on 11.5:1 compression on pump gas...and make ~250-300hp

Dragframe

iTrader: (14)

*bump* figured i would keep this discussion going.... pretty interesting and haven't had anyone come in yet who is using this high compression/boost and low timing combo

frcefed98

iTrader: (16)

LOL wish I would have known that a few years ago when I built this "9.1-1" block up here at a mile high...thing is more like 8.1 when you take the altitude into consideration

Pro Stock John

iTrader: (34)

My only suggestion is ot not assume that the LSx is the same as a SBC or a LT1. I always hear how the LSx likes a lot less timing than the SBC.