Ok Guys, Popping out Exhaust at odd conditions.
10-19-2010, 07:08 PM
#1
Ok Guys, Popping out Exhaust at odd conditions. Car is a 383 w/TFS heads (LE set them up), BRE cam at 234/244 .610/.610 110*, Lt1 Boost Hot parts, my own cold side, T76, FAST XFI with 85lb Racetronix injectors, pressure is 42 PSI base and about 38 PSI idle, BPW is set at 1.0 ms. *wondering if issue is that I'm not able to get them shortened enough and should pull the BPW back to .8 or something to add less fuel in*
Car is still being tuned, but is running decent and driving around. Problem I'm having is that under light throttle and light load ONLY I'm getting a popping out the exhaust that freaking sounds like gunfire. I can get it to randomly do it at idle by richening it up or by playing with the throttle, but it's very random.
If I put it under light throttle (about 9% TPS or less) and light load (MAP idle is around 68-72 KPA, light load conditions being 50-65 MAP at the 9% or less TPS setting) it just freaking SNAPS out the exhaust. I've manually actuated the throttle at the blades with my head under the hood and couldn't hear anything, and when it happens the engine isn't showing any signs of being affected by it and I can't feel it in the car at all. To boot, I don't think it's happening in front of the turbo because that should quiet it down quiet a bit and these are just seriously LOUD.
Car isn't too lean because I've got it averaging about 13.5, fluctuating from 12.5 to 14.5 depending on where I am. Making it richer makes it worse, that's about it. No narrow band O2's, just the wide band O2 in the XFI. Timing is a 30-34* for the affected area. I'm wondering given the amount of overlap on the cam if I need to go higher on the timing as a fix?
Thoughts? I'd think ignition, but why woudn't the issue be present at heavier loads?? I'd think valves, but that would really present itself everywhere. Plug wires I'm positive are on correct because they were labeled at each end and I put them on under the car with the service manual schematic for the opti in front of me.
Car is still being tuned, but is running decent and driving around. Problem I'm having is that under light throttle and light load ONLY I'm getting a popping out the exhaust that freaking sounds like gunfire. I can get it to randomly do it at idle by richening it up or by playing with the throttle, but it's very random.
If I put it under light throttle (about 9% TPS or less) and light load (MAP idle is around 68-72 KPA, light load conditions being 50-65 MAP at the 9% or less TPS setting) it just freaking SNAPS out the exhaust. I've manually actuated the throttle at the blades with my head under the hood and couldn't hear anything, and when it happens the engine isn't showing any signs of being affected by it and I can't feel it in the car at all. To boot, I don't think it's happening in front of the turbo because that should quiet it down quiet a bit and these are just seriously LOUD.
Car isn't too lean because I've got it averaging about 13.5, fluctuating from 12.5 to 14.5 depending on where I am. Making it richer makes it worse, that's about it. No narrow band O2's, just the wide band O2 in the XFI. Timing is a 30-34* for the affected area. I'm wondering given the amount of overlap on the cam if I need to go higher on the timing as a fix?
Thoughts? I'd think ignition, but why woudn't the issue be present at heavier loads?? I'd think valves, but that would really present itself everywhere. Plug wires I'm positive are on correct because they were labeled at each end and I put them on under the car with the service manual schematic for the opti in front of me.
10-19-2010, 08:37 PM
#2
Car is a 383 w/TFS heads (LE set them up), BRE cam at 234/244 .610/.610 110*, Lt1 Boost Hot parts, my own cold side, T76, FAST XFI with 85lb Racetronix injectors, pressure is 42 PSI base and about 38 PSI idle, BPW is set at 1.0 ms. *wondering if issue is that I'm not able to get them shortened enough and should pull the BPW back to .8 or something to add less fuel in*
Car is still being tuned, but is running decent and driving around. Problem I'm having is that under light throttle and light load ONLY I'm getting a popping out the exhaust that freaking sounds like gunfire. I can get it to randomly do it at idle by richening it up or by playing with the throttle, but it's very random.
If I put it under light throttle (about 9% TPS or less) and light load (MAP idle is around 68-72 KPA, light load conditions being 50-65 MAP at the 9% or less TPS setting) it just freaking SNAPS out the exhaust. I've manually actuated the throttle at the blades with my head under the hood and couldn't hear anything, and when it happens the engine isn't showing any signs of being affected by it and I can't feel it in the car at all. To boot, I don't think it's happening in front of the turbo because that should quiet it down quiet a bit and these are just seriously LOUD.
Car isn't too lean because I've got it averaging about 13.5, fluctuating from 12.5 to 14.5 depending on where I am. Making it richer makes it worse, that's about it. No narrow band O2's, just the wide band O2 in the XFI. Timing is a 30-34* for the affected area. I'm wondering given the amount of overlap on the cam if I need to go higher on the timing as a fix?
Thoughts? I'd think ignition, but why woudn't the issue be present at heavier loads?? I'd think valves, but that would really present itself everywhere. Plug wires I'm positive are on correct because they were labeled at each end and I put them on under the car with the service manual schematic for the opti in front of me.
Car is still being tuned, but is running decent and driving around. Problem I'm having is that under light throttle and light load ONLY I'm getting a popping out the exhaust that freaking sounds like gunfire. I can get it to randomly do it at idle by richening it up or by playing with the throttle, but it's very random.
If I put it under light throttle (about 9% TPS or less) and light load (MAP idle is around 68-72 KPA, light load conditions being 50-65 MAP at the 9% or less TPS setting) it just freaking SNAPS out the exhaust. I've manually actuated the throttle at the blades with my head under the hood and couldn't hear anything, and when it happens the engine isn't showing any signs of being affected by it and I can't feel it in the car at all. To boot, I don't think it's happening in front of the turbo because that should quiet it down quiet a bit and these are just seriously LOUD.
Car isn't too lean because I've got it averaging about 13.5, fluctuating from 12.5 to 14.5 depending on where I am. Making it richer makes it worse, that's about it. No narrow band O2's, just the wide band O2 in the XFI. Timing is a 30-34* for the affected area. I'm wondering given the amount of overlap on the cam if I need to go higher on the timing as a fix?
Thoughts? I'd think ignition, but why woudn't the issue be present at heavier loads?? I'd think valves, but that would really present itself everywhere. Plug wires I'm positive are on correct because they were labeled at each end and I put them on under the car with the service manual schematic for the opti in front of me.
I am going to watch this. I am having a very similar issue in the exact same areas as well as idle. My prob is that in those areas it is rich (12s AFR)and fouling the plugs real easy. Check your plugs. I getting popping from fouling the plugs in those areas that you are having a prob with. Good luck.
10-19-2010, 08:43 PM
#3
I'm going to pull them again tomorrow. Had them out a few days ago and they looked fine, a little dark, but not fouled out by any means. I've got autolite 104's in there right now gapped at .030 but once I start boosting it I'm moving to BR7EF's because of the short reach and .028 gap out of the box.
Tony mentioned the Acceleration Enrichment tables to me, and I'm going to try zeroing those out and see what that gets me tomorrow.....will probably kill throttle response, but we'll see.
Tony mentioned the Acceleration Enrichment tables to me, and I'm going to try zeroing those out and see what that gets me tomorrow.....will probably kill throttle response, but we'll see.
10-28-2010, 03:15 PM
#4
I'm going to pull them again tomorrow. Had them out a few days ago and they looked fine, a little dark, but not fouled out by any means. I've got autolite 104's in there right now gapped at .030 but once I start boosting it I'm moving to BR7EF's because of the short reach and .028 gap out of the box.
Tony mentioned the Acceleration Enrichment tables to me, and I'm going to try zeroing those out and see what that gets me tomorrow.....will probably kill throttle response, but we'll see.
Tony mentioned the Acceleration Enrichment tables to me, and I'm going to try zeroing those out and see what that gets me tomorrow.....will probably kill throttle response, but we'll see.
10-28-2010, 06:55 PM
#6
Haven't tried it yet Tony. Haven't felt like laying under the car imitating a contortionist to change all teh plugs. Brian Macy pointed out some stuff in the tune for me that NEEDS addressing, wihch I'm going to do, and he said the AE tables didn't look bad at all IIRC (I'll have to reread the email).
Planning on tomorrow and Saturday spending some time on it.
Planning on tomorrow and Saturday spending some time on it.
10-28-2010, 08:37 PM
#7
Haven't tried it yet Tony. Haven't felt like laying under the car imitating a contortionist to change all teh plugs. Brian Macy pointed out some stuff in the tune for me that NEEDS addressing, wihch I'm going to do, and he said the AE tables didn't look bad at all IIRC (I'll have to reread the email).
Planning on tomorrow and Saturday spending some time on it.
Planning on tomorrow and Saturday spending some time on it.
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10-29-2010, 08:23 AM
#9
Hmmm....found this on another site:
LT1 w/ Trick Flow & Edelbrock Heads
Thread – 14mm
Reach – 3/4”
Socket – 5/8 hex
Seat – Gasket
Stock – MFG Recommendations: approx under 9:1 compression
Heat Range: 4
Gap: Consult ignition mfg.
Plug: NGK FR4 (stock number 5155); NGK BKR5EIX (stock number 6341); Autolite 3926; Champion RC12YC (stock number 71); Denso IK16 (stock number 5303)
MFG Recommendations: approx 10.5:1 compression
Heat Range: 5
Gap: Consult ignition mfg.
Plug: NGK FR5 (stock number 7373); Autolite AR3924 (Racing Plug); Autolite 3924; Champion RC9YC (stock number 2075); Denso K20PR-U (stock number 3145); Denso IK20 (stock number 5304)
MFG Recommendations: approx 11:1 compression
Heat Range: 8
Gap: Consult ignition mfg.
Plug: NGK R5672A-8 (stock number 7173); Autolite AR3911; Champion C63YC (stock number 796); Denso IQ24 (stock number 5314)
MFG Recommendations: approx 12:1 compression
Heat Range: 9
Gap: Consult ignition mfg.
Plug: NGK R5672A-9 (stock number 7405); Autolite AR3910; Champion C61YC (stock number 785); Denso IQ27 (stock number 5315)
MFG Recommendations: approx 13:1 compression
Heat Range: 9 - 10
Gap: Consult ignition mfg.
Plug: NGK R5671A-9 (stock number 5238); Autolite AR3933; Champion C59CX (stock number 296); Denso IK27 (stock number 5312)
MFG Recommendations: approx 14:1 compression
Heat Range: 10
Gap: Consult ignition mfg.
Plug: NGK R5671A-10 (stock number 5820); Autolite AR3932; Champion C57CX (stock number 295); Denso IK-31 (stock number 5321)
**NOTE: Use chart for static compression and adjust heat range for nitrous use accordingly.
Thread – 14mm
Reach – 3/4”
Socket – 5/8 hex
Seat – Gasket
Stock – MFG Recommendations: approx under 9:1 compression
Heat Range: 4
Gap: Consult ignition mfg.
Plug: NGK FR4 (stock number 5155); NGK BKR5EIX (stock number 6341); Autolite 3926; Champion RC12YC (stock number 71); Denso IK16 (stock number 5303)
MFG Recommendations: approx 10.5:1 compression
Heat Range: 5
Gap: Consult ignition mfg.
Plug: NGK FR5 (stock number 7373); Autolite AR3924 (Racing Plug); Autolite 3924; Champion RC9YC (stock number 2075); Denso K20PR-U (stock number 3145); Denso IK20 (stock number 5304)
MFG Recommendations: approx 11:1 compression
Heat Range: 8
Gap: Consult ignition mfg.
Plug: NGK R5672A-8 (stock number 7173); Autolite AR3911; Champion C63YC (stock number 796); Denso IQ24 (stock number 5314)
MFG Recommendations: approx 12:1 compression
Heat Range: 9
Gap: Consult ignition mfg.
Plug: NGK R5672A-9 (stock number 7405); Autolite AR3910; Champion C61YC (stock number 785); Denso IQ27 (stock number 5315)
MFG Recommendations: approx 13:1 compression
Heat Range: 9 - 10
Gap: Consult ignition mfg.
Plug: NGK R5671A-9 (stock number 5238); Autolite AR3933; Champion C59CX (stock number 296); Denso IK27 (stock number 5312)
MFG Recommendations: approx 14:1 compression
Heat Range: 10
Gap: Consult ignition mfg.
Plug: NGK R5671A-10 (stock number 5820); Autolite AR3932; Champion C57CX (stock number 295); Denso IK-31 (stock number 5321)
**NOTE: Use chart for static compression and adjust heat range for nitrous use accordingly.
Last edited by Fastbird93; 10-29-2010 at 08:29 AM.
10-29-2010, 09:37 AM
#10
Car is a 383 w/TFS heads (LE set them up), BRE cam at 234/244 .610/.610 110*, Lt1 Boost Hot parts, my own cold side, T76, FAST XFI with 85lb Racetronix injectors, pressure is 42 PSI base and about 38 PSI idle, BPW is set at 1.0 ms. *wondering if issue is that I'm not able to get them shortened enough and should pull the BPW back to .8 or something to add less fuel in*
Car is still being tuned, but is running decent and driving around. Problem I'm having is that under light throttle and light load ONLY I'm getting a popping out the exhaust that freaking sounds like gunfire. I can get it to randomly do it at idle by richening it up or by playing with the throttle, but it's very random.
If I put it under light throttle (about 9% TPS or less) and light load (MAP idle is around 68-72 KPA, light load conditions being 50-65 MAP at the 9% or less TPS setting) it just freaking SNAPS out the exhaust. I've manually actuated the throttle at the blades with my head under the hood and couldn't hear anything, and when it happens the engine isn't showing any signs of being affected by it and I can't feel it in the car at all. To boot, I don't think it's happening in front of the turbo because that should quiet it down quiet a bit and these are just seriously LOUD.
Car isn't too lean because I've got it averaging about 13.5, fluctuating from 12.5 to 14.5 depending on where I am. Making it richer makes it worse, that's about it. No narrow band O2's, just the wide band O2 in the XFI. Timing is a 30-34* for the affected area. I'm wondering given the amount of overlap on the cam if I need to go higher on the timing as a fix?
Thoughts? I'd think ignition, but why woudn't the issue be present at heavier loads?? I'd think valves, but that would really present itself everywhere. Plug wires I'm positive are on correct because they were labeled at each end and I put them on under the car with the service manual schematic for the opti in front of me.
Car is still being tuned, but is running decent and driving around. Problem I'm having is that under light throttle and light load ONLY I'm getting a popping out the exhaust that freaking sounds like gunfire. I can get it to randomly do it at idle by richening it up or by playing with the throttle, but it's very random.
If I put it under light throttle (about 9% TPS or less) and light load (MAP idle is around 68-72 KPA, light load conditions being 50-65 MAP at the 9% or less TPS setting) it just freaking SNAPS out the exhaust. I've manually actuated the throttle at the blades with my head under the hood and couldn't hear anything, and when it happens the engine isn't showing any signs of being affected by it and I can't feel it in the car at all. To boot, I don't think it's happening in front of the turbo because that should quiet it down quiet a bit and these are just seriously LOUD.
Car isn't too lean because I've got it averaging about 13.5, fluctuating from 12.5 to 14.5 depending on where I am. Making it richer makes it worse, that's about it. No narrow band O2's, just the wide band O2 in the XFI. Timing is a 30-34* for the affected area. I'm wondering given the amount of overlap on the cam if I need to go higher on the timing as a fix?
Thoughts? I'd think ignition, but why woudn't the issue be present at heavier loads?? I'd think valves, but that would really present itself everywhere. Plug wires I'm positive are on correct because they were labeled at each end and I put them on under the car with the service manual schematic for the opti in front of me.
Sorry I could never open your files, I'm sure you were asked about that good ole Opti? even if its new, I had one from the chevy dealer that would not even start the car, Took it apart and the parts were in 180 out..
10-29-2010, 11:42 AM
#12
TECH Fanatic
I know that when my opti went bad, my car would idle fine, and rev pretty well, but under any kind of load I thought it was going to explode.
I'm sure your situation is quite different, as my car had been in storage for a long time, the water pump had been leaking on the opti prior to going into storage, and when I got the car out the opti was in pretty bad shape. Still, it didn't really show any noticeable symptoms until it was under load.
I'm sure your situation is quite different, as my car had been in storage for a long time, the water pump had been leaking on the opti prior to going into storage, and when I got the car out the opti was in pretty bad shape. Still, it didn't really show any noticeable symptoms until it was under load.
10-29-2010, 11:49 AM
#13
I know that when my opti went bad, my car would idle fine, and rev pretty well, but under any kind of load I thought it was going to explode.
I'm sure your situation is quite different, as my car had been in storage for a long time, the water pump had been leaking on the opti prior to going into storage, and when I got the car out the opti was in pretty bad shape. Still, it didn't really show any noticeable symptoms until it was under load.
I'm sure your situation is quite different, as my car had been in storage for a long time, the water pump had been leaking on the opti prior to going into storage, and when I got the car out the opti was in pretty bad shape. Still, it didn't really show any noticeable symptoms until it was under load.
10-29-2010, 07:17 PM
#15
I now think it is extra fuel leaking into the intake or the bypass valve too close to the TB or the bybpass outlet tube too close to the MAF or I don't know what.
It is in the garage for the winter and will work on it in the spring. It beat me down.
