LOL stupid phone and auto correct. PINTLE wear,
and honestly its been a while with this stuff for me so im going from memory.

 

also this is a great calculator.
http://www.rceng.com/technical.aspx#...ctor_Worksheet_

 

I wish I could know how much HP i could expect this supercharger to add to a STROKER. It's 100 for a 4.0. It might add another 30-80 just because it's a stroker. Then the hesco aluminum head might add another 50-100 because of the stroker/supercharger variable.

I have too many variables here. My 450 assumption is based off of the fact that I'm only getting 100 HP from the Avenger. It's assuming that I also make 90 from the head from Hesco, so I should be safe there. But for it to make 50 just on a stock 4.2 has me thinking that with a 4.7 stroker/supercharger I'm thinking it's going to be more like 110+.

All this speculation is great, but it's nothing more than that. I need a professional speculator.

 

I calculated the percentage increase of HP in comparison to the stock 4.0 (100 is added to 190, a 53% increase) and used 53% as the increase for my current 280 (added 20 just because I'm sure I have at least that from modifications I have done) and came up with 428 HP.

The Hesco Head's 30 HP for a stock 4.0 is a 16% increase. 16% of 428 = 68. That puts me at 496 ponies, assuming percentages are the most accurate way to pinpoint the possible horsepower.

The 4.2 gets a 50 HP boost from the HH, but I'm not familiar with those engines. I know it's basically the same thing just with a different crank, but they still only made 110-115 HP at the various later stages of their development. The '71 model year had 150 for some reason. I guess horsepower wasn't fashionable after 71.

So, assuming I made 500 HP on this engine, I'm looking at needing 50lb injectors to maintain 80% IDC.

A question for the boost-literate people, how much is that going to affect the fuel curve when I'm just cruising around with light throttle (considering these numbers anything more than a light throttle would be extreme). ??

 

haha, hmmmmm, professional speculator, I think id be good at that.
The unfortunate truth is that you are exactly correct. you dont know how much its going to add. To be honest, I can tell you right up front that witht he 5.5psi pulley, it is not going to make anywhere near 5.5psi. not only is the engine moving a much larger volume of air, with the aftermarket head, there is much less restriction to get it in.
Remember that boost is only the restriction into the head.
So my thought is, with the stock (or smaller pulley) is the supercharger going to move the volume of air required to make that much of an increase of power on an engine that moves such a greater volume of air.
I dont think that the supercharger will make as much with the same pulley on the stroker as it would on a stock engine.
Ill tell you my now professional speculation.
If the stock engine moves 4.0liters of air a minute (*just throwing out numbers) and the supercharger provides 5.0 liters of air to make 5psi of boost, and now your engine is using 4.7 liters of air, the supercharger is still only moving 5. so the difference in volume was just lost.
I think that you will end up having to run a bigger pulley, to get the cfm required to make the power your looking for.
On the bright side, you will make more power per psi, because you will have much less restriction, but you need to move a greater volume of air.
In my professional speculating opinion, I would subtract 15% of the power that the supercharger is supposed to add on this combo at the rated boost level. but add 15% to what the head is supposed to add to a stock engine, because it will add more to an engine requiring a greater amount of air to begin with.
That is what I would base my calculations off of.
Also, I would figure injector size at 80%dc at 49 psi of fuel pressure, at 55bsfc. Now at the worst case, if you end up running over 80% while tuning, you can go to an adjustable fuel pressure regulator, or a boost referencing regulator. With a good in tank fuel pump (walbro 255 etc.) you can run up to 100 psi. so with the right boost reference, you should have a plenty large window to keep your injector dc in check and provide the fuel required to do so.
on a side note, I always use a boost reference regulator because quite frankly, the smaller the injector the better and cleaner the idle. a massive injector has such a low duty cycle at idle, it ends up doing funky stuff. Also higher fuel psi=better atomization

 

And with that you have just explained to me why I always wondered why everyone upgrades the fuel pump vice the fuel injectors. I never thought of that.

So... would it be possible for me to use say a 24 lb injector with the Walboro 255? With the fuel pressure being constant, wouldn't that basically be the same thing as running a larger injector? The fuel is still going to flow at however many cc's, just now the fuel pump is producing higher pressure as opposed to larger FI's opening longer... so I don't see how that affects the idle...

I'm relieved that the increased displacement reduces the efficiency of the boost. I thought in the back of my mind as I started this thread that having more displacement would reduce the boost. I wasn't sure, and it never occurred to me to ask. I suffer from too much ADD and having 14 tabs open trying to find information on the iWeb doesn't help.

So instead of adding 16% of the increased HP from the head I should add the % from the SC to the head unit instead?

I calculated that .7 of 4.0 is 17.5%, and that reducing 5.5PSI by 17.5% put me at exactly 4.5. I was still thinking that regardless of PSI, the SC still moves the same amount of air. Only instead of it being a higher pressure forced into 4.0 liters of space, it's a smaller PSI BECAUSE it's going into 4.7 liters of space. The amount of air that is moved is still the same, so shouldn't the amount of fuel, and therefore horsepower, still be 100? More air mean more fuel.

 

I'd be concerned of overrunning the fpr with a 255.

 

Just in case anyone is actually paying attention to my numbers I miscalculated the expected horsepower when I arrived at 496~. I had already added head horsepower to the supercharger horsepower, then calculated the proposed added horsepower from the head unit AGAIN.

It's my bed time.

Ok, so assuming that even though I only make 4.5 PSI with the 4.7 liter, I'm still pushing the same amount of air into it and therefore making 100 HP. That puts me at 380. Now, 16% of 380 is 440 HP.

So you're saying add 15% to the 16% (31%), and multiply THAT times the supercharged HP (380) ? That seems astronomical. 31% of 380 is 117. So 497 would be the end result with that math. That would be robbing Peter to pay Paul so to speak.

Seems like taking % from the SC and adding it to the HH (not to be confused with the button on the vending machine as Mitch Hedberg would have you believe) was basically deflating one number to inflate another. I just say that the HH makes a static 16% increase on a stock 4.0, and the percentage is slightly offset maybe with a stroker (simple because of the aftermarket cam I have) since we're calculating the percent based off of displacement already. That's the constant, everything else is a variable.

So which one seems more viable? Me thinking I'm making 440, or you saying I add the extra 15% to the HH math and still make the 496 I was already making from before. I refuse to believe that having more displacement reduces the amount of HP I can make from the supercharger. Having more space to push in air doesn't mean the supercharger produces less air. Less boost yes because there's more space for it to fit into. But it's still the same amount of air, and the air still gets the appropriate fuel (assuming I don't Ray Charles the soldering like I used to) to offset it. Which equates to... the same amount of horsepower.

Tell me if that sounds wrong to be, because it sounds really correct in my mind. And I don't want to go around believing I'm right when I'm wrong. Just because I figured out Santa didn't exist on my own before I was 5 doesn't mean I can figure out everything in life.

 

correct that the sc will move the same volume of air, but since the engine requires more to run naturally aspirated at the increased displacement anyway, you wont see the same power increase. You will now require a larger volume of air and fuel to fill the increased capacity of the cylinder. This is why stroking it adds the power, that extra volume of air and fuel. BUT now the sc is still moving the same volume of air as it would on a 4.0, so the stroker is essentially using a portion of that volume to run on its own. like I said, if your using 4.0l of air and the supercharger is moving 5.0l. you have an excess of 1.0l or air (and fuel). this is where you get the restriction, and boost. now, your engine is requiring 4.7l of air to run on its own, and the sc is still moving 5.0l of air. you are only in excess of .3l of air. (and required fuel)
so to get the same results on the stroker you need to move 5.7l of air.
I hope that makes sense.
Large injectors at idle have such a short duty cycle, they end up basically dripping, causing smoke, rough idle, etc. also driveability and mileage goes down because of the decrease in atomization.
so yes essentially, you want to run the highest fuel pressure possible with the smallest injector.
As long as like said above, the rest of the system can handle it. I have never met a fuel system that could not though. Even my brothers stock 91 toyota pickup 22re I turboed has one in it and its fine. i wouldnt worry about that.

 

oh and adding and subtracting the power is because each component adds a different amount of power. taking 15% away from 100, is a much greater difference than adding `15% of 50. so thats why that happens.

 

...who said I have an FPR...

 

are you implying these came without one? I didn't think they were that poorly constructed

 

The liters vs. boost makes sense, and the injectors make sense.

So what I want is, 1200 PSI in the fuel system, which will have to be forged titanium, and 2lb injectors. It's practically going to be straight fumes spewing out of the injectors.

 

Unless it's part of the fuel pump on the 97 and later models. 96 and before had them I know. It's also a 49 PSI pump vice 43.5.

 

YEP that's how diesels do it