Dip in nitrous dyno caused by what?
Thread Starter
Joined: Nov 2001
Posts: 8,246
Likes: 34
From: Victoria, TX
Dip in nitrous dyno caused by what? Check out this dyno run:
I thought the dip was caused by a slipping clutch. V-6 Bird thinks it's ignition related or dyno pickup related.
Here are some details about my car. NX MAF kit with 100 hp jets. 900 psi bottle pressure. The dyno pickup was done to the coil primary wire and not the plug wire. We got much more reliable readings that way so I don't think it's that. As far as igintion goes, I have stock 2000 F-body coil packs and stock wires. I'm running NGK TR6ix iridium plugs gapped .038". These plugs had 0 miles on them on this run. V-6 Bird doesn't like iridium plugs and says they can cause problems. Lots of the Viper guys spraying big nitrous swear by the iridium plugs so if it's the plugs, it would be a surprise. Could it be fuel pump related? I'm still running stock fuel pump and approaching 500 rwhp. Please help. Thanks.
I thought the dip was caused by a slipping clutch. V-6 Bird thinks it's ignition related or dyno pickup related.
Here are some details about my car. NX MAF kit with 100 hp jets. 900 psi bottle pressure. The dyno pickup was done to the coil primary wire and not the plug wire. We got much more reliable readings that way so I don't think it's that. As far as igintion goes, I have stock 2000 F-body coil packs and stock wires. I'm running NGK TR6ix iridium plugs gapped .038". These plugs had 0 miles on them on this run. V-6 Bird doesn't like iridium plugs and says they can cause problems. Lots of the Viper guys spraying big nitrous swear by the iridium plugs so if it's the plugs, it would be a surprise. Could it be fuel pump related? I'm still running stock fuel pump and approaching 500 rwhp. Please help. Thanks.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
very odd. Well...start with what you think it may be. First...on the dyno pickup possibility....go to the dyno computer and pull up the run. Click on the bottom so that instead of reading rpm across the bottom...it reads "speed" in MPH. If its a pickup glitch it would be smooth on the "speed" graph. Also...when you lose your RPM signal...the TQ generall spikes UP in huge amounts. I seriously doubt this is the cause of the dip.
I would like to see your AF graph as well to see if the AF has any dips or spikes at that point to indicate a momentary noid closing.
But my guess is the plugs or plug gaps. .038 isnt huge...but a lil more than I would have it for that power level...and who knows how the irridiums will react. If you notice that dip comes at peak Tq (around 500 ft/lbs) where cylinder pressure is highest. This is the most likely area to have a spark issue. For ***** and grins...I would put NGK TR6 in gapped at .032 (paying very close to get them exactly at .032) and redyno.
I would like to see the FA graph too though.
I would like to see your AF graph as well to see if the AF has any dips or spikes at that point to indicate a momentary noid closing.
But my guess is the plugs or plug gaps. .038 isnt huge...but a lil more than I would have it for that power level...and who knows how the irridiums will react. If you notice that dip comes at peak Tq (around 500 ft/lbs) where cylinder pressure is highest. This is the most likely area to have a spark issue. For ***** and grins...I would put NGK TR6 in gapped at .032 (paying very close to get them exactly at .032) and redyno.
I would like to see the FA graph too though.
A slipping clutch will usually be a big dip as soon as it hits. You have a steady graph for about 500 rpms after the hit so i would think that it couldn't be the clutch. Especially the radical dip and return to almost the same power. Double check your plugs and make sure you are at .038". Maybe a plug was dropped or gapped a little higher and the spark is blowing out? Something has to be going wrong here.
Nate
Nate
I was running the Bosch iridiums and would get a sharp quick spike in my a/f logs from wb. This is indicative of a spark miss. I change to NGK TR6's and it went away, so I say I don't like the iridiums for spraying either. An a/f on this run may show problem?
Thread Starter
Joined: Nov 2001
Posts: 8,246
Likes: 34
From: Victoria, TX
The wideband wasn't working on this run, but we did monitor the narrow band sensors with the Tech II. No lean points at all during the run, so I think the A/F ratio is OK. Would running TR6s at a narrower gap compromise my power N/A? This is important since I do 95% of my running on motor.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
I'm not sure you can see a ignition miss with the NB sensor and/or tables. It shows as a micro width lean spike (quite high), unlike a regular lean signal that runs out a ways.
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Thread Starter
Joined: Nov 2001
Posts: 8,246
Likes: 34
From: Victoria, TX
If it was fuel pump or fuel pressure related, wouldn't I be going lean and not rich? The A/F ratio on the 75 shot run was much richer than the 100 shot run. The 100 shot was like 12.5 to 1 and the 75 shot was closer to 11.0 to 1. Probably didn't help that I had only 900 psi. BTW, the 75 shot dyno was before the 100 shot dyno FWIW.
Thread Starter
Joined: Nov 2001
Posts: 8,246
Likes: 34
From: Victoria, TX
Originally Posted by Robert56
We really need an a/f ratio print.
Another vote for the FR mounted regulator. With the stock one located in the tank in the fuel pump bucket it will allow the pressure in the lines to shoot up and over compensate, causing a few rich dips and never really being able to fully recover. Do a Racetronix pump and a new regulator. Just remember to remove the stock one when you do LOL. We usually see this limitation of the stock fuel system around 475 - 500 RWHP.
Last edited by 383LQ4SS; Jun 14, 2005 at 07:04 PM.
Originally Posted by Patrick G
It's even worse on a 75 shot. Check it out. WTF?
Mike
Originally Posted by 383LQ4SS
very odd. Well...start with what you think it may be. First...on the dyno pickup possibility....go to the dyno computer and pull up the run. Click on the bottom so that instead of reading rpm across the bottom...it reads "speed" in MPH. If its a pickup glitch it would be smooth on the "speed" graph. Also...when you lose your RPM signal...the TQ generall spikes UP in huge amounts. I seriously doubt this is the cause of the dip.
I would like to see your AF graph as well to see if the AF has any dips or spikes at that point to indicate a momentary noid closing.
But my guess is the plugs or plug gaps. .038 isnt huge...but a lil more than I would have it for that power level...and who knows how the irridiums will react. If you notice that dip comes at peak Tq (around 500 ft/lbs) where cylinder pressure is highest. This is the most likely area to have a spark issue. For ***** and grins...I would put NGK TR6 in gapped at .032 (paying very close to get them exactly at .032) and redyno.
I would like to see the FA graph too though.
I would like to see your AF graph as well to see if the AF has any dips or spikes at that point to indicate a momentary noid closing.
But my guess is the plugs or plug gaps. .038 isnt huge...but a lil more than I would have it for that power level...and who knows how the irridiums will react. If you notice that dip comes at peak Tq (around 500 ft/lbs) where cylinder pressure is highest. This is the most likely area to have a spark issue. For ***** and grins...I would put NGK TR6 in gapped at .032 (paying very close to get them exactly at .032) and redyno.
I would like to see the FA graph too though.
Mike
Thread Starter
Joined: Nov 2001
Posts: 8,246
Likes: 34
From: Victoria, TX
No purge, but we did a high rpm nitrous run on the dyno (about 1 second between 5000-5500 rpm) to purge the system before the 75 shot dyno run (the one with the 2 dips). After the 75 shot run, we did the 100 shot run. If the 1 second dyno blast was not enough to purge the line, it could be possible that the line may not have been completely filled with N2O. But if that were true, wouldn't the line be good by the time of my 100 shot run? Still looking for answers. Thank you for your responses.
Thread Starter
Joined: Nov 2001
Posts: 8,246
Likes: 34
From: Victoria, TX
Originally Posted by gollum
Why were there no dips in the torgue curve? I would use a different dyno next session.