just the system itself not the engines that came with it

anyone?

 

holley 900 TBI 500 HP?
gm 454 TB limited by injectors? http://www.users.bigpond.net.au/ben_...ctorsizing.xls
check this and assume 90 lbs at 20 lbs and what do you get?

i will have mine on dyno this spring.

 

i meant like a stock system with a holley 670 TB

sorry i wasnt specific.

 

This is a great link and should be made a stickie

BTW, why stop at 20

 

That is a pretty cool calculator. It uses the generally accepted formla's, but I have a bad feeling that the generally accepted formula's are wrong. I'm not really sure if it's the DC these injectors can handle at high FP or if it's something else. I plan on doing a little testing with my WB next week.

To answer your question. 300-325 with 90 lb injectors isn't that hard to do. Much past that and your treading the edge. My personal opinion is 400 hp is pretty much it depending on what rpm you make that at.

 

why stop at 20 lbs FP?. dont know. what i do know is that i had my vafpr installed a couple years ago and i blew the diaphragm on first crank. i did not have a FPG installed. so i will guess the pre shimmed spring was 12 and after shimming (1/8 in.) was 16 and vac boosted was 26? i assumed the first failure was an old (20 years) dia. i replaced with a new and same result blew right away. so dropped back to 12-13 base FP (i measured the preload/caliper) and it did not fail. now in looking at the vafpr it comes with a "heavy spring" that i did not use so my dia failures may be another issue. call it gun shy. dont know why i had failures.

 

Yeah, it is a cool calculator. I made it
I also believe that the HP results these "generally accepted formla's" produce is underestimated.

 

Well now that you have the Aeromotive reg, raising pressure shouldn't be an issue

 

Thats funny that you were blowing diaphrams at higher pressure, the the diaphram is on the return side of things, so there is no pressure on it, only on the metal piece in the middle. I would be worried about the gasketed surface that holds the injector pod together.

 

Never thought of that, really, but............

When I started to jack up the fuel pressure, I trued all the gasket surfaces of the injector pod with a flat file.

 

Good idea, I might try to get my injector pod on the mill at school before I graduate, I'm sure it'll nice and flat then.

 

think maybe the preload on the spring being to high caused the failure? i used very thin washers. this was 2 years ago. i measured the stock distance on the threads from stock unit. seeing the vafpr was not adjustable(without taking a torch to it) so i added about 1/8 inch preload. without FPG i had no idea what i was at. this was a feeble attempt in getting car to run better with 65 lb injectos and stock (unhacked) puter. when set at prior preload it did not blow. i still to this day cannot fiqure out how i could blow a brand new gasket. had a tear right next to the plug(?) about 3/16 inch in both cases(old/new).

 

I would use caution doing this. You may remove too much material and decrease the size of the return passage on top of the pod.

 

A friend of mine just blew his, he was running a 190 60psi pump but running 13 psi. This is what I think, the return hole is pretty small and is building up alot of psi in the regulator.

 

i cant use that calculator i need excel.

 

The stock TBI daphram, well, at least the one I had, was subject to full pressure. Its the pressure that pushes teh diaphram and spring back and allows the fuel to return.

 

I need to get some pics of what I'm talking about. The rubber part of the diaphram isn't actually getting pushed by the fuel. It's the metal valve in the middle of the diaphram that actually has the force of the fuel pusing against it. Once the fuel is past that metal tab, it is under no pressure because it is free to leave the TB through the return line.

The theory of the return passage being too small could be true, but I would think you would see problems with the FP refusing to go any lower.

I think alot of people get pressure confused with flow. Your stock TBI pump will make 90 psi of fuel pressure. Just pinch off the return line and it will pump up. Even though it now has 90 psi of pressure it doesn't have any more flow capacity now than it did at 13 psi, actually it has less because the pump is less efficient at higher pressure. So the added pressure isn't going to make the restrictive return port any more of a problem than with the lower pressure.

I think there is a problem with high spring pressure on the diaphram causing it to kink or flop over in the housing putting a tearing force on the rubber part of the diaphram. Rbob posted a datalog wher his regulator was draging the pintle on the seat cause eratic pressure when he would blip the throttle, I think we may have the same problem at higher spring pressures, it could even be so bad that it tears diaphrams.

 

I could see that, this is what I'm talking about there retrun passage in the regulator this one is less than 3/16

 

I guess my arguement is that the return passage is fine unless you run into an issue that you can't turn the fuel pressure down far enough. This would be most likely at idle since most of the fuel is bypassed at idle. Some guys have ran into this problem with the 255 lph walbro pump on fairly mild combo's. I ported mine out a bit just for good measure.

 

write some thing up, How not to burn your TBI F-body down to the ground By BMmonteSS

 

What did you use?

Hmmm. Extrudehone comes to mind

 

Just drilling the hold deeper will open it up alot same for the inlet side.