About to take a BFH to my car!
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From: Valdosta GA
About to take a BFH to my car! I'm actually not new here but I lost my password and I haven't had the original email account in 8 years 
Here's my problem: I built a race car! I stripped out my excellent running daily driver because I thought I could build a fast car.
Here's what I have: 408ci solid roller LT4, Big damn cam, Bid Damn AFR 227 heads by GTP, Big Damn TH 400, Big bad 9 inch -- car makes very little H.P. and stops running at 4900 rpm (I mean flat out misses) every single time no matter what I do (loaded and unloaded). Fuel system fabbed by me which consist of an aeromotive A 1000 - duel feeding the fuel rails. Fuel pressure is constant 43 psi.
Possible contributing factors: LTCC ignition (although it ran like a scalded ape in my 383), accelleronics 95lb low impedance injectors with resistor box (I was supposed to be spraying the holy crap out of this thing). Stock computer with my 383 tune which I bastardized. It's been over 3 months since I've had the car together and i'm about at my wits end - it's about to be BFG time
Forgot to add - yes the plugs have been gapped all the way down to 20 thou. I shouldn't have to with LS2 coils though!
Michael
Here's my problem: I built a race car! I stripped out my excellent running daily driver because I thought I could build a fast car.
Here's what I have: 408ci solid roller LT4, Big damn cam, Bid Damn AFR 227 heads by GTP, Big Damn TH 400, Big bad 9 inch -- car makes very little H.P. and stops running at 4900 rpm (I mean flat out misses) every single time no matter what I do (loaded and unloaded). Fuel system fabbed by me which consist of an aeromotive A 1000 - duel feeding the fuel rails. Fuel pressure is constant 43 psi.
Possible contributing factors: LTCC ignition (although it ran like a scalded ape in my 383), accelleronics 95lb low impedance injectors with resistor box (I was supposed to be spraying the holy crap out of this thing). Stock computer with my 383 tune which I bastardized. It's been over 3 months since I've had the car together and i'm about at my wits end - it's about to be BFG time
Forgot to add - yes the plugs have been gapped all the way down to 20 thou. I shouldn't have to with LS2 coils though!
Michael
Last edited by HOGDRVR; Oct 8, 2012 at 06:32 AM. Reason: Forgot to add crucial info
Shutting down at 4900 load or not sounds to me like ignition. or maybe a HUGE tuning glitch.
Far as the injectors were you figuring dry shot, how do you do a big dry shot with a stock pcm(small I know can be done before the MAF? Your injectors are more than twice as big as they need to be for the engine. This needless complication is another likely source of troubles.
I would throw an opti and 30-42lbs injectors on it, once running you could try and make the LTCC work again.
I know that "conventional wisdom" is you bought the best of everything, but there is a HUGE gap between actual wisdom and conventional wisdom, you need to simplify things a whole lot and then if you want to try and put the LTCC back on and then whatever you were trying to do to spray dry do those one at a time after the car is running right..
If you were planning a wet kit then the huge injectors and converter box should never go back on the car. Really the only way I would consider injectors that size is if you were running an aftermarket pcm that could control them with a dry shot. Which I think could be a good way to go long term.
Far as the injectors were you figuring dry shot, how do you do a big dry shot with a stock pcm(small I know can be done before the MAF? Your injectors are more than twice as big as they need to be for the engine. This needless complication is another likely source of troubles.
I would throw an opti and 30-42lbs injectors on it, once running you could try and make the LTCC work again.
I know that "conventional wisdom" is you bought the best of everything, but there is a HUGE gap between actual wisdom and conventional wisdom, you need to simplify things a whole lot and then if you want to try and put the LTCC back on and then whatever you were trying to do to spray dry do those one at a time after the car is running right..
If you were planning a wet kit then the huge injectors and converter box should never go back on the car. Really the only way I would consider injectors that size is if you were running an aftermarket pcm that could control them with a dry shot. Which I think could be a good way to go long term.
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From: Valdosta GA
All good words! My thought was a dry shot with a plate system (250-300). Stock PCM because I have a wife although she's been very understanding - I've dumped so much money into this thing already, I'm not doing another 2500 at this point. The LTCC ran so damn good on my 383 and I changed absolutely nothing (except the whole frickin motor 
). Good God I can't imagine going back to an opti - I hated changing them.
I had 42lbers on the 383 which put down 415 to the rear wheels, this thing was supposed to be around 550 with another small V-8 shoved on top of it. I know - you are of course correct. I should go with a smaller injector and probably should have stayed with the high impedance ones -- I might just go back. The whole low pulse width and offset voltage is killing me.
The tune - I shouldn't have even started messing with. I had an old LT5 engineer try to tune it a few months back but we couldn't get around the 4900 miss issue on the dyno.
I hate the thought of taking it back apart but I think that's what I may be doing - the thought of shooting it with a 50 cal does seem to lighten my mood though.
BTW - the nitrous system isn't on the car and won't be until she runs correctly so that's not one of the possible issues.
Michael
). Good God I can't imagine going back to an opti - I hated changing them.I had 42lbers on the 383 which put down 415 to the rear wheels, this thing was supposed to be around 550 with another small V-8 shoved on top of it. I know - you are of course correct. I should go with a smaller injector and probably should have stayed with the high impedance ones -- I might just go back. The whole low pulse width and offset voltage is killing me.
The tune - I shouldn't have even started messing with. I had an old LT5 engineer try to tune it a few months back but we couldn't get around the 4900 miss issue on the dyno.
I hate the thought of taking it back apart but I think that's what I may be doing - the thought of shooting it with a 50 cal does seem to lighten my mood though.
BTW - the nitrous system isn't on the car and won't be until she runs correctly so that's not one of the possible issues.
Michael
Last edited by HOGDRVR; Oct 7, 2012 at 04:17 PM.
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From: Apopka FL
it sounds like a ignition issue or you have a possible poor grounding issue with. i would not worry about the injectors right now. if it can run at idle with them it will run fine as long as the injector size is set to match the program.
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From: Valdosta GA
It does in fact idle pretty darn good - I had some issues with the big ASM throttle body but got that worked out. Considering the cam, it idles well at 1050 rpm. I'll go back through the LTCC wiring and make sure the grounds are good - I've 2 gauge from block to frame so I'll make sure the harness is good.
Thanks for the info.
Michael
Thanks for the info.
Michael
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The opti is NOT a bad piece, plenty of us use them long term without ever having an issue. If you had a lot of opti issues maybe there was a problem you just never found and that problem is still hiding somewhere.
IMO when something is grossly overcomplicated like in the case of using an LTCC and impedance converter it is just basic troubleshooting to return to a more basic setup get it running keeping things simple, then add the complicated stuff one thing at a time.
First thing I did to my car12+ years ago was "ignition upgrades" and after a month or two the car would break up so badly before the shift that I had to lift to get it to shift I replaced a lot of other parts before I finally took off the "ignition upgrades" which were the whole problem. Then a couple years later I was having a WOT stumble and just knew it had to be the opti because everyone knows how bad it is, an opti swap later and no improvement, well when I had the injectors cleaned the 7 working ones varied 8% in flow and one just dripped.
IMO when something is grossly overcomplicated like in the case of using an LTCC and impedance converter it is just basic troubleshooting to return to a more basic setup get it running keeping things simple, then add the complicated stuff one thing at a time.
First thing I did to my car12+ years ago was "ignition upgrades" and after a month or two the car would break up so badly before the shift that I had to lift to get it to shift I replaced a lot of other parts before I finally took off the "ignition upgrades" which were the whole problem. Then a couple years later I was having a WOT stumble and just knew it had to be the opti because everyone knows how bad it is, an opti swap later and no improvement, well when I had the injectors cleaned the 7 working ones varied 8% in flow and one just dripped.
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From: Valdosta GA
The opti isn't a horrible piece - it's just horribly placed. I ordered my 94 Z and was there when they backed it off the trailer. I replaced 3 opti's over it's lifetime (200K + miles). I upgraded to a 95 vented system to try and get some of the Ozone out of the cap but they still have issues over time. There is not much better out there for a timing reference though which is why the LTCC system uses it - I took the rotor off of mine so I wouldn't have any issues with the thing coming apart at high rpm ( that's not an issue right now
)
I ran the LTCC for over 1.5 years with nothing but joy in my heart - better idle, no issues running past 5K rpm with 8 coils - no more ICM's to go bad due to heat. It ran really well. I was making sure it would be good for the upcoming race car - that hasn't really panned out so far.
The injector thing I totally get. My nature causes me to go over the top at times and that is a totally complicated system. I have had the injectors checked so at least I know that are all matched and functioning mechanically - is there anything else you can think of that would cause the computer to stop their function at 4900rpm like MAP pressure or anything like that.
Trouble shooting on a holiday - I love it. It's only money and my piece of mind.
Michael
)I ran the LTCC for over 1.5 years with nothing but joy in my heart - better idle, no issues running past 5K rpm with 8 coils - no more ICM's to go bad due to heat. It ran really well. I was making sure it would be good for the upcoming race car - that hasn't really panned out so far.
The injector thing I totally get. My nature causes me to go over the top at times and that is a totally complicated system. I have had the injectors checked so at least I know that are all matched and functioning mechanically - is there anything else you can think of that would cause the computer to stop their function at 4900rpm like MAP pressure or anything like that.
Trouble shooting on a holiday - I love it. It's only money and my piece of mind.
Michael
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From: Valdosta GA
Still about to take a hammer to it. I talked with the acceleronics guy and changed the injector offset numbers to the correct ones - no luck.
Does anyone have any experience with reversion in large cam/stock intake LTX cars?
Does anyone have any experience with reversion in large cam/stock intake LTX cars?
Did this setup ever work well? Here's a silly question: Do you have the rev limiter in the LTCC box set?
Why do you have such a small plug gap? How's the arc in a test plug?
Why do you have such a small plug gap? How's the arc in a test plug?
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From: Lansing, MI via Bowling Green, KY, Dalton GA, Nashville, TN & Atlanta, GA
If the LTCC still uses the optical sensor portion of the opti, maybe the MSD unit is bad. Or is that just an MSD cap? I think it's just the cap. In that case, nevermind. Is the non cap part from a Delco opti?
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From: Valdosta GA
Paul,
The LTCC ran very well on my old 383 and yes I checked the rev limiter(not a silly question BTW)- the entire engine is new as well as the accelronics injector set up on the car. The plugs were gapped down as I was trying to rule out weak spark (13.5:1 CR).
BTC,
The opti could still be a problem and I don't know why I haven't taken it off and looked at it. The screws that hold the rotor in place really hold everything together although it happens so consistently I have my doubts. I'm going to check though.
Michael
The LTCC ran very well on my old 383 and yes I checked the rev limiter(not a silly question BTW)- the entire engine is new as well as the accelronics injector set up on the car. The plugs were gapped down as I was trying to rule out weak spark (13.5:1 CR).
BTC,
The opti could still be a problem and I don't know why I haven't taken it off and looked at it. The screws that hold the rotor in place really hold everything together although it happens so consistently I have my doubts. I'm going to check though.
Michael
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From: Valdosta GA
nitrous2fast,
Not retarded at all - in fact I have tried speed density and it does the exact same thing, although it runs worse since it isn't tuned SD.
I'm going back to shoot the grounds - I may hook the whole thing into the battery ground just to see if that's the issue.
Michael
Not retarded at all - in fact I have tried speed density and it does the exact same thing, although it runs worse since it isn't tuned SD.
I'm going back to shoot the grounds - I may hook the whole thing into the battery ground just to see if that's the issue.
Michael
