hey im tryin to figure out exactly how much HP an engine will have that i'm planning to build.. is there any way i could figure that out if I know exactly what parts I'm gonna put in it?

 

There are programs, such as Desktop Dyno, that allow you to specify parts and it will estimate the engines HP.

There is no exact way to tell you since there are too many variables. Once it is built, put it on a dyno and tweak from there.

Hope this helps.

 

Desktop dyno can give a theoretical best performance however due to things it can't calculate such as timing, jetting etc, you'll rarely ever be close to it's projected power level. DD is good for "what if" testing. What if I tried this cam, headers, intake etc to see what kind of changes it would do. Timing could be off a couple of degrees from the best timing and the engine could be down 20-30 hp just from that.

Another way to predict a theoretical best performance is to use head flow numbers. Heads can only flow so much air and the amount of air they flow will limit the amount of HP an engine can produce.

Estimated Horsepower Based on CFM -
HP = .2575 x CFM (@ 28" of water) x number of cylinders

Lets say you have some L98 aluminum heads. The maximum they flow is 199 CFM from .500 to .600 lift. The formula says they'll only produce 410HP. Untouched, they're rated for 409HP so the formula is pretty close.

Changing the camshaft, intake, headers, carb etc doesn't change how much HP the heads can produce. All it does is move the HP curve up and down in the rpm range or changes how flat a curve is or not. If the heads have a peak HP range with .600 lift and you only have a .500 lift cam then you're not getting all the heads can produce. If you use a head that maxes out performance at .500 lift and you try to use a cam with .600 lift, it won't increase the amount of HP if a similar cam was used with .500 lift.

The heads on my car have potential to make 726 HP at .700 lift and 730 HP at .800 lift. My camshaft has .740 lift and the best uncorrected HP I've been able to produce based on 1/4 mile performance in relation to race weight is 721.

Tell me what heads you want to use and I'll tell you how much HP potential they have. Of course bigger valves and port and polishing changes the flow numbers so lessor heads can make more power but even then, they still have limits. Those L98 heads can be massaged to produce 499 hp.

 

ahhh but i plan to use forced induction, which completely changes the heads theory correct? at least for the intake part anyways

 

Desktop dyno was 4 hp off on my engine if i remember right..... it still depends more on theory though. The most accurate you can do is a dyno, but you can always see if you can find a dyno chart for a similiar engine online. I have even gotten a lot of ideas that way.

 

well, this thread was great.. alot of good info.. but, as it stands now, everything that I've posted on this forum about my car is now irrelevant.

about 2 hours ago, someguy came up to my drivers side window with a .38 special and took off across town in my car.

with me in the passengers seat.. if they ever bust him, hes lookin at 70 yrs to life.. carjacking (10 yrs) kidnapping (25-life) using a handgun to commit a felony (sentence x2).

at least im still alive =].

i hope i find it.. It was a very, very clean 1988 Trans Am GTA.. beautiful car..

sorry to be so grim loll.. have a good one guys.. i probably wont be back on the boards for a while

 

glad to hear you made it okay, the car can be replaced

i hope they catch him and give him the what for he deserves

 

they found him 6 hrs later! with my car undamaged! YEA! damn i got my car backk woot woot! lol. I got beat by a toyota celica last night though.. my car needs some building.. its bonee stock.. damn thing.. lol

 

I guess that's very lucky. I am glad that you got your car back undamaged instead of it being wrapped around a tree.

 

yeah no kiddin.. after the other night though i'm going to sell the car. It's too much of a liability, especially since I don't have a garage to keep it in. How much do you think I could ask for an '88 gta w/ a 305? it's in pretty good condition..

 

Glad you're ok and you got your car back, but I wouldn't let one incident convince you to sell it.

 

well i'm also moving across the continent in a month, and I don't have the money to drive it there, so I got no choice but to sell it lol

 

now you need to have a intake that will flow as much as the heads.

I need to know how much a performer air gap flows.