Adding fuel injection and HP numbers I found on this site

[vintagemotors60]

hi, i am new to this site and maybe asking some dumb questions from time to time.
I have a 74 bronco and I want to add fuel injection. I just built a 200 with a 250 head and added big valves.its has a ford six cam 268/274 advanced 6 deg. stock pistons with a CR if about 8.9 to one. i kept it low so i wouldnt over heat in the woods. I now have a header and webber carb.
I ran the engine dyno program I have when I built the engine and it gave me HP of 204@5500 and TQ 218@4000/4500. The cam i have gave the best HP with only 2 lb of TQ loss. i compared 9 cams before i chose.
My question is. I have seen the dyno runs and they are no where close to my computer numbers. why? is there 100 HP loss threw the drive train?
Why i am asking is? i am trying to match a throttle body and if i plug in 200 hp i cant find a one barrel that will give me enough fuel flow. I need to know should I figure Net or Gross HP to calculate LB for the injecter? I have a 1 Barrel from a 2.5L GM that will work great but the injector is too small for 200 HP. If I am really only making 100 HP then i can bump up the pressure and use the one I have.
I have found a 2 barrel off a old ford 302 from the 80's that will work with 200hp but i think it has too much area for part throttle. What I mean is on the side of a hill it will not be progressive enough. form what I read if you get a throttle body too large you will have problems holding a steady throttle at speed also.

My engine sure feels like more than 100 HP!

 

[wallaka]

Very unlikely that you have even 160 flywheel hp. The program probably has very optimistic VE and flow numbers, the log head really messes with that. I'd go with around 70% VE...pretty low.

Also, probably won't be turning 5500 in the woods...the head runs out of flow at about 4400 or before anyhow. There is a 15-20% drivetrain loss. The engines were rated at 125 gross, like 100 net (which should be used for calculations). Most hit about 75-80 at the wheels stock.

There is a thread about using a Tempo TBI unit in the Fuel Injection forum, it seems to work very well, and should be about the same as your TB. So I'd look there.

 

[fordconvert]

Throttle bore is not as big a problem with FI. A non linear linkage can work. If you can also do timing control I have found you can mellow out the response if needed without hurting the high end of things.

A single injector maxes out at around 150 hp, the bigger the injectors are the more trouble you have getting them to idle. TBI injectors dont tend to do well with higher pressures. I read that most get in trouble when you get near 20 psi so dont count on just boosting the pressure to get more out of em.

Holley made (or maybe still makes) a 1bbl with a 90lbhr injector.

 

[MustangSix]

The reality is that the log head has extremely poor flow numbers. It works well up to the 100-120 hp number where it was designed to operate, but to make much power beyond that requires significant modifications such as extensive porting, big valves, removal of the log, etc.

Adding EFI of any flavor would make the engine more efficient in its range, but does little to improve the inherent flow issues.

 

[vintagemotors60]

Ok, I want to make sure I understand what you are telling me. My engine is not able to make the numbers the program says because of the head?
so what is my real gross hp?
Do I figure the gross hp about 120? If so it looks like the single injector will work.
I make these assumptions based on the net numbers on the listed dyno runs on this web site. does everyone agree with me on this?
With my combo is 120 hp about right? it sure feels like more than that.

 

[fordconvert]

It may feel like more because the peaks are actually closer (or actually in) a usable rpm range UNLIKE your typical modern 250HP I4 that peaks at 6-7K where you cant use it.

 

[MustangSix]

You are probably making something close to 120 - 125 hp. I would be willing to bet that on a chassis dyno you'll see about 90-100 RWHP. That's been pretty typical for builds like yours.

What you feel in the 'ol butt-dyno is torque. Your torque peak is probably lower than your simulation indicates, maybe peaking at 2600-2800, and probably nice and flat. That gives you a good off-the-line pull and feels strong.

 

[XFlow_Fairlane]

I would go look for a throttle body off a 3.8L V6. similar to the 302 model but smaller injectors and a smaller bore.