Need help figuring out problem with car
Need help figuring out problem with car hey guys,
I wanted to post this here becuase there is a number of things that could be to cause.
Last night when I was dynoing my car we ran 2 pulls on a 300 shot. On both pulls arounf 5400 rpm the car had a sudden drop of 40-50 HP and TQ. We checked the logs and there was nothing we found that could result in a sudden drop like this. AF was 11.5 slowing getting ritcher down to 10.5 (something else we have to work on). But the AF was a gradual drop, nothing as dramatic as the dyno showed. Also, the drop occurs exactly at the same RPM on both runs. The motor does not hesitate or sound like it is having problems, the only way we could tell is on the graph.
The only things we can think of is that it could either be convertor blow through or possibly blowing out the spark plugs. I am using TR7s with a gap of .030 and I would imagine we would hear it if we were blowing out the plugs.
Any ideas? Here is the graph with both pulls:
Any input would be appreciated. Thanks
Timmay!!!
I wanted to post this here becuase there is a number of things that could be to cause.
Last night when I was dynoing my car we ran 2 pulls on a 300 shot. On both pulls arounf 5400 rpm the car had a sudden drop of 40-50 HP and TQ. We checked the logs and there was nothing we found that could result in a sudden drop like this. AF was 11.5 slowing getting ritcher down to 10.5 (something else we have to work on). But the AF was a gradual drop, nothing as dramatic as the dyno showed. Also, the drop occurs exactly at the same RPM on both runs. The motor does not hesitate or sound like it is having problems, the only way we could tell is on the graph.
The only things we can think of is that it could either be convertor blow through or possibly blowing out the spark plugs. I am using TR7s with a gap of .030 and I would imagine we would hear it if we were blowing out the plugs.
Any ideas? Here is the graph with both pulls:
Any input would be appreciated. Thanks
Timmay!!!
TECH Enthusiast
Joined: Jul 2006
Posts: 638
Likes: 0
From: San Diego
Originally Posted by ibanezrg770
TTT, wow anyone? Timmay!!!
Originally Posted by GOaT Cheese
That is an immediate drop ain't it. At the same exact RPM each time? Possible false, or real for that matter, knock causing 'puter to yank timing real hard? At such a specific RPM I would look for some sort of sytem "noise" that the PCM is zoning in on. Something stupid like an MSD window switch activating, or an exhaust harmonic that comes in at that exact RPM. Or computer going into a "fail safe", "limp in" "open/closed loop" type of thing. I would love to see a snapshop of the PCM data stream a few frames before and after this occurs.
We were not picking up any knock on the log. But I can add to that that I have a 402 with relocated knock sensors and no new calibration (haven't figured that out yet). We still have them turned on but we did not pick up any knock.
I am not using MSD, I have an EFILive custom OS in the car and I am pulling timing with their nitrous option. We set all the tables to pull enough timing to equal 19* as we wanted to start out safe. I believe he had it locked in closed loop during the run.
The car is using the same tune that it uses NA and there is no drop like that. I am using a stand alone fuel system for fine tuning the AF and so the only thing that should be changing is the timing.
Is there anything else I can provide that may help? Do you guys think this could be my convertor? Thanks for your imput. Timmay!!!
its not blowing the plugs out. if your still running the same gas you were thats a ton of timing in the car, be careful
Thats a data point where it logged multiple samples, does the rpm flare then settle down in the logs? does it seem lazy/down on power (should be about 250 more then when you dynoed here)
Thats a data point where it logged multiple samples, does the rpm flare then settle down in the logs? does it seem lazy/down on power (should be about 250 more then when you dynoed here)
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Thanks Shiz,
You think 19* is too much running 116 in the standalone?
I am going to try and get the logs from Bret when he has the chance.
You know I switched my setup right? It definately picked up a lot more than when I had the old setup but I am just trying to figure out this dropoff. I gained 280 HP from the 300 even with the dropoff and when that is cleared and we get the AF set, I think I will gain a lil over 300. It didn't seem lazy by ear, you could not hear any drastic changes in the RPM but that whole run was only a little over a second long. Bret and I looked over the all the logs for about 1/2 hour and could not find anything in the logs that would cause such a dropoff. Thats kind of why we were thinking it was in the converter. Timmay!!!
You think 19* is too much running 116 in the standalone?
I am going to try and get the logs from Bret when he has the chance.
You know I switched my setup right? It definately picked up a lot more than when I had the old setup but I am just trying to figure out this dropoff. I gained 280 HP from the 300 even with the dropoff and when that is cleared and we get the AF set, I think I will gain a lil over 300. It didn't seem lazy by ear, you could not hear any drastic changes in the RPM but that whole run was only a little over a second long. Bret and I looked over the all the logs for about 1/2 hour and could not find anything in the logs that would cause such a dropoff. Thats kind of why we were thinking it was in the converter. Timmay!!!
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If the whole run was only a second long, your not loading the car nearly enough to be of any benefit tuning it. need a good load on her for something like that
that was me by the way on Shiz name.
that was me by the way on Shiz name.
