TBIThrottle Body Injection discussion and questions. L03/CFI tech and other performance enhancements.
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ur welcome. if you look at some of their other cables, you'll see some w/ various connectors on each end. I have to say I've never used any of their products, but I hate what some people charge for a simple cable as much as anyone. Hope one of them works out for you.
firstly I'm pretty sure gm tells you never to take that part off the TB. I did it once on a l03 truck, and couldnt get it to seal again...leaked a little, forever. Secondly, I dont understand how you can check the true pressure of the INTERNAL REGULATOR passageway of the TB setup. Look at it, fuel goes in at X presssure, is stepped down to X pressure (according to your extensive and very thorough testing)and sent to the injectors which consume X amount of that working regulated pressure, and the remaining pressure "R", haha, is sent back to the tank, its not available to the injectors this time around. I've never thought about how you can check the fuel pressure AFTER the regulator on these TB setups. Anyone, please slap me for being dumb, I just dont see it---Kindly explain how it's possible, if so. So, what are you guys checking in terms of pressure?? Where? Inlet to TB?? outlet from TB?? cause it's all one peice after the fittings, except for the regulator. You would have to take inlet and subract outlet to determine working pressure. Minimum working pressure has to be able to feed the PWM length of the injectors during their most neediest of duty cycles.
The only true way to be able to adjust true working pressure is to have a setup like this guy--I dont know how changing a spring will definitively give you any concrete, objective, quantifiable information, other than a change in pressure, but not specifics of working pressure (and consumption). someone clear this up for me, please.
this is what I am planning on doing... concrete, objective, quantifiable. a feed line, a regulated working pressure line, and a return to tank line. with an electronic sender for in cabin fp monitoring. you're talking $2.50 for springs, by the half-dozen. Cough up some loot and do it a little better than swinging a sledge hammer in the dark. I just dont see how you can check working pressure... help. wtf do i know anyway. other than dont buy a walbro
If someone wants to go thru the expense of an external regulator, that's fine and it will work great . . . but the factory reglator also works great.
I am most familiar with the Crossfire's 4 banger TBs, and I've done a fair amount with the dual injector Bib block TB's as well. All of the TBI I have seen regulate the outlet of the TB. Unless the return line is plugged up, a fully open regulator would net a very small pressure . . from there it is a matter of adjusing up to the max your spring can produce . . . WITHOUT binding the spring.
The spring and diaphram react effectively instantaneously to the pressure drop when the injectors open. The gage in the above photo is my pressure tap tecnique for the crossfire TB. That tap is directly into the chamber under the diaphram so it sees exactly what the injector sees. The steady reading on a non-oil filled gage proves the regulator is capable of smoothing out the injector pulses.
As I mentioned months ago in this thread, I have springs that go from 14.5 to 30psi. Hats off to you guys who are getting deep into the design of TBI springs, but really they are adjustable so one well selected spring will handle the entire reasonable range. Much over 30psi and, in my opinion, you are risking a ruptured diaphram.
GM has no qualms about anyone taking the regulators apart. A new diaphram is a normal part of the rebuild kits. What GM does not want is some yahoo running the adjuster up to spring bind which will make the presure shoot up to the full fuel pump pressure and you can get a 'degreasing shower' if you do that.
that's exactly what I was wondering. that picture explained it all. if you dont tap a fitting in, or have an external FPR with appropriate fittings, then there really isnt much to tell on what pressure is actually seen at the injectors??? I cant imagine everyone wallering out that screw cap, and turning their screws without being able to see where theyre going.
thanks for being so thorough. not yer' first rodeo, huh?
i wonder in the v8's, there likely isnt enough room to get a fitting in, under there with two injectors???
Something tells me GM knew the lenght of compressed spring required to approximate 12 lbs FP. There is a tang that can be measured and referenced. As long as 12-13 lbs all was well.
Did you guys test anymore springs lately? I have the number calculated at home, don't recall it now, but I think it wa 25-30 psi range for my application. Anticipate 375 HP and using the Holley 670 tbi unit.
Will these springs work wth the holley TBI? Will they produce the same pressure?
Aurum_Duck - The regulator controls pressure in the entire fuel supply line - not just at the injectors. For the most part, the pressure is the same from the pump all the way to the injectors. It's true, in order to have flow there MUST be a pressure drop. Although I haven't actually measured it, my guess is it would be very low. 1-2 psi at the very most (unless the fuel filter is clogged).
For my purposes, a relative measurement at a given point is enough to determine the effect of adjusting the regulator and/or changing the spring on fuel pressure and in turn the potential flow of the injectors. The stock regulator spring and adjustment on my TBI was providing 11 psi or less. After upgrading the spring, the pressure at the same point is at 15-16 psi. The engine idles better and definitely responds better to quick openings of the throttle.
As fas as I know the stock Fbody spring is good for 13 lbs plus plus. Top Down solutions I recall is 15 lbs plus.
My Aeromotive low pressure spring is 10-20 lbs. The other spring(2 of 2) but high pressure is 20-50(???). Not sure on the 50 side. Aeromotivve spring appears to be similar int-ext diameter as GM but a tad taller. I no longer have a GM spring to compare to. If someone can measure the adjustability to GM FPR pod I can measure my Aeromotive spring. I suspect they will sell it to you. Nothing special there. Just a spring.
if you have the aeromotive 13301 the springs are rated at 3-20 and 20-65 psi iirc.
i asked aeromotive a while back and they were telling me i could get these springs for 10$ each..
__________________ '84 T/A HO 5speed, freshly rebuilt L69
'89 Formula, somewhat modded L03 and soon T56+3.73
do not confuse a lack of traction with an excess of torque
One of the previous threads that i have posted in has TONS of data regarding springs.
the O.D., spring height and wire thickness are just the beginning. You must look at spring rate, load, number of coils per inch, spring material, et etc etc. All have a factor in creating a certain psi and a certain psi range.
I have tested MANY MANY springs and have a ton of data.
hahaha that's pretty funny yeah anyways, i'm not interested in farting around with springs, i'll be getting the mentioned aeromotive unit. just thought i'll post its springs' specs as a reply to Ronny's post.
__________________ '84 T/A HO 5speed, freshly rebuilt L69
'89 Formula, somewhat modded L03 and soon T56+3.73
do not confuse a lack of traction with an excess of torque
anyways, i'm not interested in farting around with springs, i'll be getting the mentioned aeromotive unit. just thought i'll post its springs' specs as a reply to Ronny's post. 
