Fireball

iTrader: (21)

Stock stroke + 4.010 bore. Target boost is 3bar (29-30 psi).

Here is the compressor map:
http://www.turbobygarrett.com/turbob...pmap_large.gif

Consumption for a 364 @ a PR of 3.0 (3 bar) @ 7500 rpm is ~130-135 lb/min, putting it right on the ragged edge of that compressor map

Backpressure will probably be pretty brutal up there due to the smallish turbine...which I think will allow the slightly later IVC.

Darren P

iTrader: (1)

once I get my twin setup running I will test some cams on it

I am starting with a 234/234 598/598 116+4
the engine is a 403 CID with AFR 225 heads
turbos will either be the APS kit or twin 66mm

peter@aps

iTrader: (2)

The GT7 cam would be a far more friendly cam for a turocharged engine.

Peter

CHRISPY

Yup I think you're right, that makes sense to me...It'll be cool to see how it does once it's running

You are right on the bleeding edge of the compressor map hehe

That combo is going to be nuts man you must be excited

Fireball

iTrader: (21)

Have you ever known me to do something NOT on the bleeding edge

30 psi + 9:1 compression should be pretty nuts....can you say goodbye headgaskets

Pro Stock John

iTrader: (34)

Interesting logic stream but sadly I don't know all the terms you are using. Could you break the the acronyms down and dumb down your post for me? I am running a 234/234/113 cam, not sure if it's straight up or advanced. I think that converter and gearing are more important than the cam, assuming that some thought was initially and that the car is not extremely over or under cammed. I think it's a given that you would run more cam than a stock one for a stroker. I think the rationale behind not undercamming a stroker is that the smaller cam would decrease the efficiency of the bigger engine. If an engine can make 425rwhp with a bigger cam, then you can make all the right downstream choices like the turbo size(s).

Websy21

iTrader: (34)

Good points, I agree on the converter and gears being the most important as in any combot. As for the cam in bigger cubes or a cam in n/a, I never thought of it that way before. Thats a great point. If It makes alot more n/a its obviously will make more with a turbo/supercharger within reason. I wish someone would chime in on my thread, but good luck with the choice.

Pro Stock John

iTrader: (34)

Yeah, I was just thinking about it, and was like, if you build a 402ci 9:1 engine and then under cam it, so instead of a big 236/236 you put 206/218, what are you trying to accomplish. You keep a nice idle, but your engine horsepower is now the same as a smaller engine. So you might still need to boost up that bigger small-cammed engine as much as you would a smaller engine that makes as much power (though less torque).

Kurt Urban made this point to me a few years ago, that 15psi will double the engine horsepower. So if I make 450rwhp NA like say LastLS1, at 15 psi I am making like 900 hp. Shows the value of cubes and running enough turbo. But say you make 375rwhp like me on motor (just a guess, could be lower). At 15psi I am a 750rwhp car.

Seems to me that going up or down a little on cam won't make much of a difference, it's when folks run way too much or way too little cam that you start to reduce the effectiveness of the engine itself.

I'm sure someone better versed in turbos can make the point that its not that simple, and that you want to not go too crazy with turbo cam choices, but I have also heard 2-3 reputable tuners say that is not true, that you run race car cams in race cars regardless of whether they are turbo or not.

Websy21

iTrader: (34)

Ya I get your point, makes sense. As long as you don't over due it either way I guess. I guess I should pick the bigger of the 2 cams I have posted in my thread. Heck its only gonna cost me a little more on mileage, with the bigger cubes it will still idle good. Might have a lil lope, but I like that. I just really think that blower cams make up for having to run the blower and/or engine harger. Being more efficient, etc. Getting the same amount of hp at a lower boost setting with a blower cam than a smaller cam and a higher setting. More room for upgrading later too. Guys will always say that you don't need a big cam with blowers bc you make so much power, but the fact is that the right cam will make alot more power. If it makes 25-40 more n/a, guess what it will make probably twice or more than that blown, depending boost etc. Jsut my theory, thats the reason why I was going to run a blower cam on my stock bottom end. So I could run only 7-8 psi and make the power of running 10 without having the negatives of higher boost on stock pistons, etc. I know that it really boils down to the max hp that a stock engine will handle, but this would have helped out though. Just my .002 cents thown in if its worth f*** all or not?

RealQuick

iTrader: (14)

IVC - Inatke valve closed
ABDC - After bottom dead center
ATDC - After top dead center
EVO - Exhaust Valve open
BTDC - Before top dead center

Pro Stock John

iTrader: (34)

Thanks Real, and why do folks mess with the numbers, to get more cylinder pressure?

Web, a bigger cam with a blower setup will be worth 20-40hp over a stock cam for sure. Turbo folks however look at the duration and try to curtail the amount of duration if they think they will run out of turbo. Turbo folks are much more focused on efficiency of the system.

Fireball

iTrader: (21)

The actual valve events are whats important. If you choose exactly where you want your four valve events (IVO, IVC, EVO, EVC) then you actually calculate what they translate into in terms of durations, LSA and intake centerline...not the other way around.

These 4 numbers dictate alot, overlap, where the motor will make peak power, etc...

Pro Stock John

iTrader: (34)

Cool, so Brian, what values would you need assuming an engine had a peak rpm of 7500 rpm? How about 6500 rpm?

Fireball

iTrader: (21)

thats what I'm trying to figure out...

My first post in this thread gave my initial thoughts on the matter...

THe only valve event I really have any direct testing of was the IVC. THe overlap events (IVO and EVC) were based on what I ascertained from this thread as a starting guess.

EVO was based on typical larger cam numbers (though I don't think its a very sensitive number)

CHRISPY

haha that's true LOL!

Can't wait to see it up and running!

Jammer

iTrader: (1)

bump.. great thoughts