For an LT1 motor, built 383 with cam, in general, if I increase the boost by
one lb., how much extra rwhp will that give me?

 

depends on the size of the turbo,

 

Somewhere between 0 and 40 hp depending on a brazillian things.

 

yup yup...

 

the general rule i have aways followed is to divide the motors n/a horsepower by 14.7. that will give you an approximate estimation for what each lb of boost willl give you

 

expect ~20rwhp... thats a good average #... assuming the blower or turbo isnt maxxed out already.

 

Thanks for the input. The motor has a s/c so I figure that'll be less than with a turbo. I figured 15-20HP so my estimate might be a little low. I'm only making 10 lbs right now so I was wondering where 14-15 lbs would put me but I've got another issue to sort out first before the pulley swap.

 

60-100rwhp is a reasonable quess for 4-5psi gain.

 

60-100 is possible. Unless your maxing out your 1bar map (stock computer). which tuning @ 600+rwhp can get tricky/unsafe. Maybe look into meth/water injection..........joe

 

Any amount of boost will max out the 1Bar MAP sensor. You're thinking of the MAF sensor, I think.

 

Exactly.

 

Actually dividing by 18 instead of 14.7 is more accurate because the compressor consumes energy itself to compress the incoming air. Therefore 1 lb of boost equal a gain of 5.5%. However, there are a lot of other variables that factor in.

 

Realquick & evilundisguised, Give Speed Inc. in Sch. IL. a call & they will be happy to explain it to you. But, the way it was explained to me Because i have A 1bar map (old style computer) that i would need to go fast/bs3. they never said that the mass air flow sensor was maxed out. something about distorted fuel tables??? Or something like that. But either way unless you two are making 580+++ without meth inj. or Nos. on a stock 95 pcm you would not know what I'm talking about. So to answer the question truthfully the thread starter on this forum is in for a surprise if & when he cranks up the boost and their will be tuning issues that can be resolved with high octane 108+++, meth injection or stand alone computer. do it & find out. like other people i know.......................Joe

 

I understand how both sensors work in conjunction with the PCM. The stock (not "old-style") MAP sensor has an upper limit of 1Bar, or 1 atmosphere, meaning it will be out of its operating range ("maxed out") at any pressure above that, or any amount of boost. This is the difficulty of running any amount of boost with a speed-density tune - tuning so that the PCM keeps adding fuel when it cannot adjust for boost in its calculations.

The MAF sensor is not sensitive to pressure, only mass air flow. It does max out at some amount of airflow, which I think correlates with ~600hp, or somewhere around there. That's why I figured you had your sensors mixed up.

But you are correct, I'm not making "580+++ without meth inj. or Nos. on a stock 95 pcm", so I must be misinformed

 

You seem to be trying to recall what Speed Inc said and its obvious you dont have an understanding of how things work yourself. Your stock MAP sensor on a stock LT1 ECU reads vacuum to 0psi gauge presure. that means that if you even make only 1psi of boost, the MAP sensor is already maxxed out.

Tha quote right there tells me you dont understand how things work. You say "unless" he is maxxing out his stock MAP sensor... well even if he makes 1psi of boost only he is maxing out the sensor. Then you say tuning @ 600rwhp+ can be tricky... well that is most likely because the MAF sensor is maxxed out and cant accurately calculate the amount of airflow. This is a problem with fueling.

Now, the timing tables are controlled by MAP readings, so you are limited in how detailed your timing tables can be with the stock MAP sensor... but that doesnt make tuning hard... you just cant be as aggressive. Thats a whole other post...