Alfred Lord Tenniscourt
Active member
I built my engine with 19lb/hr injectors thinking that since I used the stock ford FI system they would be big enough. After all, they are about 1/3rd bigger than the stock 14lb/hr units.
Well, unless I have some other problem that I am not seeing, they aren't. I guess with the EGR and the smog pump out of the picture, and with a little porting and slightly oversized valves, and with maybe just a little bit of a cam and Chevy rockers, the damn thing is flowing too much for the injectors.
My original plan was to build the engine so that if I wanted to I could upgrade it without tearing it down all the way. I thought that with a single exhaust and the stock intake, it would limit horsepower and make a nice, efficient workhorse of a pickup truck engine. Then, I could throw a manifold and 4bbl on it, or maybe upgrade the FI somehow to make it fast if I ever wanted t do that.
Now, at about 2500 rpm the injectors can't keep up at WOT. So, I guess I need to figure out what injectors I should get. The problem is, that I don't know the horsepower, and I couldn't know the horsepower without being able to run it flat out even if I did have a dynamometer, and I can't get injectors that let me run it flat out until I know the horsepower.
So now I either start changing out injectors at $200/guess, or start asking you guys what you think.
So what do you think? Has anyone had to sort this out before? Here are some calcs I did that I would really appreciate it if someone would look over. I have certainly slipped a decimal or two in my day...
I calc my max HP that 19lb/hr injectors can support as 182.4
to support 250hp, I calc that 26.04lb/hr injectors would be needed.
Go up to 300hp, and it is 31.25lb/hr.
I thought I had plenty of room with these because of these two things, one of which was dumb, the other still seems strange to me. The dumb thing was that I looked at a chart somewhere and it said that 19lb/hr injnectors would support up to ~240hp. I didn't think about it at the time, but that was obviously for an eight cylinder engine with two more injectors to share the work. The thing that still seems strange to me is that Ford used 14lb/hr injectors. That means that my 19lb/hr units are some 35.7% larger. With no modifications to the plenum or to the exhaust, I really didn't think I would need to increase my injector size more than that!
Thanks in advance if you bothered to read this.
A.L.T.
Well, unless I have some other problem that I am not seeing, they aren't. I guess with the EGR and the smog pump out of the picture, and with a little porting and slightly oversized valves, and with maybe just a little bit of a cam and Chevy rockers, the damn thing is flowing too much for the injectors.
My original plan was to build the engine so that if I wanted to I could upgrade it without tearing it down all the way. I thought that with a single exhaust and the stock intake, it would limit horsepower and make a nice, efficient workhorse of a pickup truck engine. Then, I could throw a manifold and 4bbl on it, or maybe upgrade the FI somehow to make it fast if I ever wanted t do that.
Now, at about 2500 rpm the injectors can't keep up at WOT. So, I guess I need to figure out what injectors I should get. The problem is, that I don't know the horsepower, and I couldn't know the horsepower without being able to run it flat out even if I did have a dynamometer, and I can't get injectors that let me run it flat out until I know the horsepower.
So now I either start changing out injectors at $200/guess, or start asking you guys what you think.
So what do you think? Has anyone had to sort this out before? Here are some calcs I did that I would really appreciate it if someone would look over. I have certainly slipped a decimal or two in my day...
I calc my max HP that 19lb/hr injectors can support as 182.4
to support 250hp, I calc that 26.04lb/hr injectors would be needed.
Go up to 300hp, and it is 31.25lb/hr.
I thought I had plenty of room with these because of these two things, one of which was dumb, the other still seems strange to me. The dumb thing was that I looked at a chart somewhere and it said that 19lb/hr injnectors would support up to ~240hp. I didn't think about it at the time, but that was obviously for an eight cylinder engine with two more injectors to share the work. The thing that still seems strange to me is that Ford used 14lb/hr injectors. That means that my 19lb/hr units are some 35.7% larger. With no modifications to the plenum or to the exhaust, I really didn't think I would need to increase my injector size more than that!
Thanks in advance if you bothered to read this.
A.L.T.