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Increasing fuel pressure has the same effect as raising the both near idle / off idle VE tables by a fixed percentage. The maximum allowable VE value is 100.Quote:
Originally Posted by rsicard
Lowering the injector flow, for example from 61 lb / hr down to 58 lb / hr has the same effect as increasing fuel pressure.
A correctly installed SBC / BBC Throttle Body will work great on 4 barrel carburetor intake manifolds.
dave w
As always, I REALLY appreciate your thoughts and comments. Thanks much for the explanation as to the correlation of VE to injector pulse width. Need to hog out the 4 barrel opening to accomodate both the 350 and the 454 throttle body. All the parts are near ready to go for the engine/trans swap. Need to fab an AC compressor bracket for the Vortec Intake Manifold much like what is on the older 350 engine. Also need to fab a MAP sensor bracket also due to the difference between the old 350 mount bracket and the Vortec Intake Manifold mount bolts. Really have fun fabricating.Quote:
Originally Posted by dave w
Regards,
Rolly
For your AC bracket, now might be a good time to upgrade to a serpentine setup, you can get away without anything bolting to the intake and you never have to adjust belt tension again. The truck serpentine stuff is plentiful in the junkyards.
I've been mounting my MAP sensors on the firewall to clean up the intake area, so no bracket needed at all.
Thanks much for the comments. Mounting the MAP sensor on the firewall is a very good idea to help de-clutter the real-estate on top of the engine. The 1995 Chev C1500 pickup already has the serpentine belt system. At present, the old system has a bracket from the AC compressor to the intake manifold. The cast aluminum bracket for the AC compressor likely was considered a bit on the weak side with fore/aft movement. GM added the steel bracket from the back of the AC compressor to the intake manifold to make the mounting more robust. I will do the same type bracket (fabricated) with the Vortec aftermarket 4 barrel manifold and AC compressor. I have been lucky enough to find serpentine accessory brackets and pulleys on Ebay for other SBC projects.Quote:
Originally Posted by fastacton
Ok, didn't realize you already had serpentine. Even though they come from the factory with the bracket going to the intake, I've been running for many years on multiple vehicles without the brackets and haven't had any issues.
Dave: Can you steer me to the proper spring, height etc., to be used in the fuel pressure regulator on the fuel portion of the throttle body. Have spring from 94-95 454 TBI. It is TOO STRONG and Long spring and not proper to use. Also have one from 305 cu in TBI maybe closer to what is needed. The TBI assembled is a 454 lower portion and 65 Lb/Hr cop car fuel injectors with cheap adjustable fuel pressure regulator bowl. Have the 350 Vortec mocked up on a engine run-in stand and about to connect Howell built harness assy and run with TPS, MAP, CLT sensors and throttle body. Have fuel pressure gauge 0 - 15 PSI on the inlet fuel hose and lower pressure Mallory fuel pump after the fuel tank. Trying to simulate the setup, and check for appropriate TBI fuel pressure, in the 1995 Chev C1500 2WD pickup before installing the Vortec. Another fuel pressure gauge installed in the pre-mod pickup, and it reads 7.5 - 10 PSI. A little low. Also ordered adjustable JET fuel pressure regulator bowl from SummitRacing. Should be here tommorow?Quote:
Originally Posted by dave w
Your thoughts on the regulator spring spec would be greatly appreciated.
Regards,
Rolly
Dave: Just thinking some more. Perhaps the in-tank fuel pump is getting worn out and not providing the energy to pressure the regulator up to approx 12 psi. In that case it is time to remove the fuel tank and replace the fuel pump. If that is the case, then perhaps replace the pump with a high pressure capable pump. The fuel pressure regulator in the Throttle body should still regulate the pressure down to about 12 psi. Then if later going to alternating bank batch port injection, a different fuel pressure regulator which sets pressure to approx 45 psi should be used. Just want to keep the mods under cover so that emissions testing personnel don't become suspicious. It is what comes out of the tailpipe that really matters as far as emissions is concerned. I want the engine to be running clean. In fact, it would be desirable to have it go on the lean side of peak when decelerating or at lower manifold absolute pressure i.e. higher vacuum more toward closed throttle. In 1996 vehicles and on, they merely read the OBDII computer for emissions not what is coming out the tailpipe. They trust that the OBDII reports emissions conditions.
I have other info to follow:
http://www.gearhead-efi.com/Fuel-Inj...ht=tbi+springs
http://www.gearhead-efi.com/Fuel-Inj...rings-Measured
dave w
Dave: Thanks for the reply. Looked into the two links. The end of the second (Lower) link states: "I updated the excel spreadsheet with the free length measurements for the stock springs pictured in the first post". Can't find the updated spreadsheet. Can you attach it to a response please? Can't find the other two springs that correlate with Excel spreadsheet data links. Please advise. Thanks.Quote:
Originally Posted by dave w
Rolly
That is odd, I don't know what happened to the Excel spreadsheet. The original post was over 2 years ago, not sure what happened. I doubt I'll be able to find the original spreadsheet, I have over 8 different computers and numerous thump drives it could be on, it could be anywhere.:yikes:Quote:
Originally Posted by rsicard
dave w
Oh well, I will have to use the formulas to compute what the spring should to use. Then try to validate the calculations. Sure would be nice to have the specs on the two springs. Right now the Mallory lower pressure fuel pump with what I believe is the lowest compression spring is at 15+ psi on the 0-15 psi gauge. Too much pressure. Beginning to look toward the higher pressure system for better atomization.Quote:
Originally Posted by dave w
This waiting for TBI parts is really bugging me. Now waiting for TBI fuel pressure springs. Apparently, the ones that I have on hand are too stiff and will not allow the FPR to regulate down to approx 12 psi. The pressure gauge in line to the inlet of the throttle body pegs out above 15 psi. Tried to reduce spring pressure by binding together 3 of the coils of the spring with aircraft safety wire. Still to much spring pressure and maxing out the pressure gauge. The regulator when properly configured, should bypass fuel and regulate to approx 12 psi with injectors being active or non-active. The regulator should set the pressure. Right now it is TOO HIGH. Ordered and received the replacement in-tank fuel pump. Need a new sock for the pump which is on order but has not yet shown up. Same for three regulator springs. Waiting, waiting etc. All is mocked up and awaiting the new springs.
Just went to Oreilly Auto Parts store. Purchased sock for bottom of fuel pump that goes into the fuel tank. Also purchased a 1993 TBI repair kit that came with a regulator spring. The spring has a relaxed length of 1.7". The wire diameter is .070", which is smaller that two other springs, one being 1.8" free length .091 wire diameter, another being 1.8" free length .087 wire diameter. Do not know yet what there equate to in terms of fuel pressure inside the regulator.
Why are you so hung up on 12 psi, with Vortec heads on a 350 you are going to need more like 18-20 psi on those 65# injectors. You need the fuel volume to support WOT without going over 85% duty cycle, then trim back the part-throttle and idle with the chip.Quote:
Originally Posted by rsicard
Fast355:Quote:
Originally Posted by Fast355
Cannot thank you enough for your insight on this situation. I will swap out the pressure gauge on the test stand for one with wider scale and set the fuel pressure to 18-20 psi. Does TunerPro RT read out the pulse width sent to the injectors? Do not know what the scaling of the pulse width from say 10% to 85%. Do I need to wire in pigtails and hook up an Oscope to measure the injector sent pulse widths? As a matter of being curious, do both injectors fire in Async mode? Do they alternately fire in Sync mode? What is the min and max pulse width for these injectors? Sure would be nice to know. Still awaiting shipment of pigtail for ignition coil to supply +12 volts and Tach output. Other than that, have a Howell harness and spare 16187427 ECUs and Prom adapters. Want a gauge pod on the "A" pillar of the pickup with vacuum, fuel pressure and 2 channel (left and right engine bank) WideBand AFR gauge. Innovate Motorsports is in final development of dual channel digital readout wide band AFR gauge system. Limited to three gauge pillar pod.