Hi some may know we run an FED with a supercharged (4/71) Flathead ford engine in it. the last time we weighed it it was around 1700lbs it has run 9.64 @138mph with 13lbs of boost so we estamated its making around 350 moroso hp.we are looking to go a little faster low 9's or even 9.0 on the moroso it says we need another 100hp what we are wondering is there some sort of calculation of hp in relation to boost?. so we have an idea of how much boost we are looking at.

any help would be great.

Cheers Hayden
Australia

 

Provided the air doesn't get super hot, another 100hp would mean you need more like 30psi. In general you can loosely estimate hp by (pressure ratio) x (n/a hp) which looks like: ((boost+14.5)/14.5) x (n/a hp) = boosted hp.

 

How accurate these are I can't say but it may offer some help.

http://www.wallaceracing.com/Calculators.htm

edit .. when punching your numbers it comes back at 337.56 rear wheel HP and 375.06 flywheel HP so I don't imagine it's that far off....
If so , another 100 hp would put you @ 9.07 seconds and MPH of 147.68 MPH... so you would need around 5-7 lbs more boost if I read it right..

 

Thanks,

im hoping the air wont get to hot as we are injecting the fuel (alcohol) above the blower.

if im doing the calculations right boost seem close to each other.

as if we run 23lbs on the gauge so another 10lbs more than we are.

23+14.5/14.5x170= 440hp

i have just got the moroso hp and halfed it to get 170hp i gather that is close enough?.

and it comes out at 436 on the other calculator.

is there anything we might need to know to be putting 10lbs onto the current boost. maybe that is common ie: timing (we run twin plugs ), putting more fuel in?,we have had problems with heads,gaskets before but we now have solid heads orings copper gaskets so that area should be fine.anything to look out for in general?. we have a set of pipes on it we used all burns stainless stuff with megas reverse megas an stuff they told us they really wont make much of a diffrence untill we get ova 20lbs of boost.

Thanks Hayden
Australia

 

yes, more fuel is better idea.
the bsfc will get higher as power goes up
( more fuel per hp shown)
make sure you look at plugs, as more boost = more air flow ( untill the max air flow is reached)...as the air flow increases, soo does the air distrubution, and the effects of it in the manifold
if 1 cylinder gets hotter or colder, read the plugs and change nozzels to suit..
let the motor parts tell you what it wants.
if you get stuck with plug readings, let me know, and i'll mail some down to you.

 

thanks mate so we should keep an eye on the data logger on it as that should give us some good info.

sweet have u had much experience with surface gap plugs.as both our plugs are that type.


Cheers Hayden

 

yer, you can say that..
no data logger on my junk..
tune with plugs only..

 

arh ok. we are using the dlogger to help us make a more informed descision on tuning. hehe

 

I usually back calculate n/a hp with the same formula: hp@13psi / 13psi pressure ratio = n/a hp which looks like 350 / [(13+14.5) / 14.5] = 184 n/a hp, although assuming 170 n/a hp will be more conservative and probably a little more realistic. Could also say you want a 100/350 = 29% power increase which should take about a 29% increase in pressure ratio 14.5 * ({1.29 * [(13+14.5) / 14.5]} - 1) = 21psi for 450hp.

 

I'll shut up now because someone that has forgotten more about this than I will ever know stepped in ... might want to think about this before you post ..

 

no,no
always more than 1 way to skin a cat
all good