Low RPM smoothness
07-21-2006, 11:21 AM
#1
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Car: 92Z28, 99SS, 83Z28 & 86GTA
Engine: 421, LS1, 327Turbo & 383
Transmission: T-56, 4L60E, T5 & 4L60
Axle/Gears: 4:10, 3:42, 2:73 & 3:27
Low RPM smoothness
OK, car run's and drives around town kinda decent when rich, but when I get the BLM's to 128 the car's jerky as hell to drive and is guttless. What am I missing here? I'm not reading any knock and I backed up the timing and there didnt seem to be a difference.
07-21-2006, 04:05 PM
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Car: 91 GTA, 91 Formula, 89 TTA
Engine: all 225+ RWHP
Transmission: all OD
Axle/Gears: Always the good ones
Try working timing and then working fuel.
Most of the time the best results are made by playing with both tables.
Might like a little more timing with less fuel or vice versa.
Its all about having to experiement.
If u have a wideband try doing it in open loop to see if it still exists.
I have found surging/flares to be too much timing or lean spots generally
later
Jeremy
Most of the time the best results are made by playing with both tables.
Might like a little more timing with less fuel or vice versa.
Its all about having to experiement.
If u have a wideband try doing it in open loop to see if it still exists.
I have found surging/flares to be too much timing or lean spots generally
later
Jeremy
07-21-2006, 06:52 PM
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Car: 92Z28, 99SS, 83Z28 & 86GTA
Engine: 421, LS1, 327Turbo & 383
Transmission: T-56, 4L60E, T5 & 4L60
Axle/Gears: 4:10, 3:42, 2:73 & 3:27
No wide band 
but it does seem smoother in open loop. Why is that?
Timmnig wise, I lowered my low RPM timming less the stock with no effect, I am only 9:1 compression and have no knocks so I "think" I can rule out the timming.
OK, I did find one mistake with the injector's, durring my searches I found this...
The formula is: ???? It cuts it off right like that
I have SVO #30 injectors and am about 44psi. I have it set to 30 right now.
but it does seem smoother in open loop. Why is that?Timmnig wise, I lowered my low RPM timming less the stock with no effect, I am only 9:1 compression and have no knocks so I "think" I can rule out the timming.
OK, I did find one mistake with the injector's, durring my searches I found this...
Injector Flow Rate
22.08 Lbs./Hr.
The stock GM TPI system injector rating is based on 43.5 psi fuel pressure. To check fuel pressure, the pump should be running without vacuum. This can be done by jumping the pump to cause it to run without the engine running, or with the engine running and disconnecting the vacuum line and plugging the vacuum port on the manifold. If you change injectors and/or pressure, you should change this value accordingly. For instance, if you install Ford 24# SVO injectors, which are rated 24# at 40 psi, you should change this value to 24.00 if the pressure is 40 psi. But if the rated pressure for a given injector is changed, you must calculate the revised rating of the injector for that given pressure. For example, say you simply increased the pressure of a stock 22# injector (rated at 43.5 psi), to say 50 psi...
22.08 Lbs./Hr.
The stock GM TPI system injector rating is based on 43.5 psi fuel pressure. To check fuel pressure, the pump should be running without vacuum. This can be done by jumping the pump to cause it to run without the engine running, or with the engine running and disconnecting the vacuum line and plugging the vacuum port on the manifold. If you change injectors and/or pressure, you should change this value accordingly. For instance, if you install Ford 24# SVO injectors, which are rated 24# at 40 psi, you should change this value to 24.00 if the pressure is 40 psi. But if the rated pressure for a given injector is changed, you must calculate the revised rating of the injector for that given pressure. For example, say you simply increased the pressure of a stock 22# injector (rated at 43.5 psi), to say 50 psi...
The formula is: ???? It cuts it off right like that
I have SVO #30 injectors and am about 44psi. I have it set to 30 right now.
Last edited by Hawk92z-TDZ; 07-21-2006 at 08:28 PM.
07-21-2006, 10:11 PM
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Car: 86 Monte SS (730,$8D,G3,AP,4K,S_V4)
Engine: 406 Hyd Roller 236/242
Transmission: 700R4 HomeBrew, 2.4K stall
Axle/Gears: 3:73 Posi, 7.5 Soon to break
Originally Posted by Hawk92z-TDZ
I have SVO #30 injectors and am about 44psi. I have it set to 30 right now.
VernW had the same reading IIRC.
Should be good where you have it.
07-22-2006, 11:00 AM
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Car: 88 irocz
Engine: b2l 350
Transmission: corvette 4+3
I recently had the same symptoms on my car. Check and make sure your inj. are firing. I had a big ole piece of something in one of mine. As soon as i removed it everything was soomth again. Might check your plugs for one of them looking different than the rest before you go tearing into the fuel system.
07-22-2006, 01:51 PM
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Car: 91 Formula WS6 (Black, T-Tops)
Engine: 383 MiniRam (529 HP, 519 TQ - DD2K)
Transmission: Built '97 T56, Pro 5.0, CF-DF
Axle/Gears: 4.11 posi Ford 9"
Yep - my SVO 30's flowed out to be 30.5 avg. at 43.5PSI
07-22-2006, 02:11 PM
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Car: 92Z28, 99SS, 83Z28 & 86GTA
Engine: 421, LS1, 327Turbo & 383
Transmission: T-56, 4L60E, T5 & 4L60
Axle/Gears: 4:10, 3:42, 2:73 & 3:27
TY, one less problem solved.
CHK'd the injectors, there all fireing, thanx for the suggestion.
When I richen it up the car smooths out, so I think its in the VE table's somewere, but I cant find any lean readings when driving around.
Also to make matters worse I took out 5th gear this morning in my trany, I guess the last year rebuilt W/C T-5 just didnt have what it takes to live upto the 412, lol
I'll try to convert the bin I have sofar to post here.
Let me know if it dont work.
CHK'd the injectors, there all fireing, thanx for the suggestion.
When I richen it up the car smooths out, so I think its in the VE table's somewere, but I cant find any lean readings when driving around.
Also to make matters worse I took out 5th gear this morning in my trany, I guess the last year rebuilt W/C T-5 just didnt have what it takes to live upto the 412, lol
I'll try to convert the bin I have sofar to post here.
Let me know if it dont work.
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07-26-2006, 07:02 AM
#9
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Car: 92Z28, 99SS, 83Z28 & 86GTA
Engine: 421, LS1, 327Turbo & 383
Transmission: T-56, 4L60E, T5 & 4L60
Axle/Gears: 4:10, 3:42, 2:73 & 3:27
This one Started out as an AXCN, but alot has been changed
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