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Pathetic 427 numbers...help!

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Old Sep 17, 2007 | 11:26 AM
  #21  
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I hope it's something simple like happened to me. I had a cracked plug after the Dynatech headers were installed while still SI. I was down 40-50 horsepower on the dyno. I thought, "Oh crap, these headers are too big for SI and have killed my power." While idling the bad plug would fire. Just under a load did it break down and only run on 7 cylinders. It still felt and sounded OK while driving around. It was just way weaker than I thought it should have been. It WAS weaker than it should have been. Found the cracked plug, changed it, the power obviously came back and it was a whole different animal. I hope your problem is something so simple as that. Good luck.
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Old Sep 17, 2007 | 12:04 PM
  #22  
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Interested to see how this one turns out....
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Old Sep 17, 2007 | 12:10 PM
  #23  
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That TQ curve start far earlier then a factory LS7 intake really should. The power curve is also very short. That engine should not start falling off till at least 6400 or higher. Cam timming. Somethings wrong here. I am thinking its in very early.


Originally Posted by Patrick G
Your curves suggest proper cam timing. Either the dyno had a screwed up weather correction or you're down 1 cylinder. With your tuning software, start turning off cylinders to see if you have a dead hole. My guess is you're not getting spark to one cylinder. 482/7 = 68.9 rwhp/cylinder (if you're down 1). A full 8 cylinders would give you 551 rwhp which is about where you should be.
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Old Sep 17, 2007 | 03:42 PM
  #24  
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keep us posted, bro.
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Old Sep 17, 2007 | 03:57 PM
  #25  
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im not saying this is your problem but every ls1 in rx7's ive seen so far have dynoed low, idk if its anything in the drivetrain dynamics that is causing a problem but the ones i dynoed were down over 10 percent in power for each application
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Old Sep 17, 2007 | 03:57 PM
  #26  
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Originally Posted by LS1curious
That TQ curve start far earlier then a factory LS7 intake really should. The power curve is also very short. That engine should not start falling off till at least 6400 or higher. Cam timming. Somethings wrong here. I am thinking its in very early.
Power peak is at 6600 rpm and torque peak is at 5200 rpm which indicates sound valve events. The curves have the shapes as they should, they're just down altogether, like you're not firing one cylinder.
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Old Sep 17, 2007 | 04:12 PM
  #27  
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actually they don't look like anything I am familair with as far as that intake goes. Usually power goes very flat at around peak TQ and stays that way till around 6500 or so. Thats a stock engine to.


Originally Posted by Patrick G
Power peak is at 6600 rpm and torque peak is at 5200 rpm which indicates sound valve events. The curves have the shapes as they should, they're just down altogether, like you're not firing one cylinder.
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Old Sep 17, 2007 | 04:15 PM
  #28  
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Originally Posted by Patrick G
Power peak is at 6600 rpm and torque peak is at 5200 rpm which indicates sound valve events. The curves have the shapes as they should, they're just down altogether, like you're not firing one cylinder.
I agree. I'd expect this combo to be making upwards of 550whp when everything is figured out.
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Old Sep 17, 2007 | 05:42 PM
  #29  
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Hey Ryan, don't leave us hanging on this one bro. let us know how this turns out. I'm sure I'm not the only want on the results of this!
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Old Sep 18, 2007 | 01:54 AM
  #30  
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Erik and Greg did the work on my motor. Very pleased! As for the break in time. I did the same as you and no issues at all. I made good power with my set-up! Before the beck intake I was 518rwhp 495TRQ! with my 408! Heads flowed there *** off!
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Old Sep 18, 2007 | 02:01 PM
  #31  
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Try leaning it out a little as mentioned, most guys shoot for 13:1 NA at peak BHP maybe 12.8 peak torque.
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Old Sep 18, 2007 | 05:06 PM
  #32  
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Sorry been too busy to post lately. Unfortunately, I may have to leave everyone hanging on this one. I'm leaving for Japan next Monday and have limited time to work on the car until then. When I leave, the car will be going into indoor government storage for three years (covered). It will be fired up once a month, driven to a new spot in the warehouse and any maintainance performed. I don't really have much of a choice here as the government of Japan wants $3-$5K to bring it into "compliance" and another $3-$5K when it would be due to come back to the states. I was also warned that I could have been hassled by the EPA on my return as well. *sigh*

Had I got an engine back in a reasonable time, I may have been able to do something about this. Not to knock Erik too bad, he's a nice guy and all, but the 14 month wait on the engine was a little ridiculous. What can ya do? :shrug:

I'll be sure to set a 2500RPM rev limit or something in the software before I leave the storage facility

As far as the ideas being tossed around:

Plugs & wires: I suppose I could go back to my old MSD's and another set of plugs. I inspected all of them for cracks once already. I don't think that's it but it's worth a shot.

LSx powered RX-7's dynoing low: Nothing in the drivetrain is Mazda except the hubs. T56 tranny, 03' Mustang 8.8 IRS out back (3.55 gearing), DSS Level 5 axles & CV's.

Leaning it out: Unless our wideband is WAY off, I can't see 1/2 a point equating to too much.

Dyno sucks: I don't think so. We run a number of cars on our dyno and most are "about right".

Temp gun: Great idea....not sure if I'll have time to find one though

Weather conditions: We're at sea level (50 ft, technically). According to weather.com for Sunday: 63°F, 58% humidity, 30.29 baro, uncorrected power was 502 RWHP. I'll have to double check the uncorrected torque reading.

I appreciate all the feedback though. I just wish I had more time to mess with it.

Ryan
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Old Sep 18, 2007 | 05:53 PM
  #33  
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Try to have fun bro! Make the best of it................Okinawa?
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Old Sep 18, 2007 | 06:18 PM
  #34  
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Originally Posted by 1999vetteroo
Try to have fun bro! Make the best of it................Okinawa?
Yokosuka, Navy
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Old Sep 19, 2007 | 10:50 AM
  #35  
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I was down 70hp on my 408 because my TB wasn't opening all of the way. I had the cable in the wrong hole on my Fast TB and it was only opening 2/3 of the way. We reconnected it to the bottom hole, adjusted the cable length and it picked up 72hp and 60tq.
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Old Sep 19, 2007 | 03:31 PM
  #36  
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damnit man, i am curious about this.
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Old Sep 19, 2007 | 04:29 PM
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Easiest way to tell that is via tuning software. If your throttle isn't reading 100% with the pedal to the metal... ding ding! And you can check that right now before you leave (even without software, just have someone watch the TB as you mash the pedal and see if they can open it any further)! Don't leave us hanging on that one!
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Old Sep 19, 2007 | 06:56 PM
  #38  
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TB was one of the first things I checked. Software reads 100% TPS and visually, the buttefly is horizontal @ WOT.

Ryan
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Old Sep 19, 2007 | 09:36 PM
  #39  
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Please do yourself a favor and temperature check the exhaust primaries with a temp gun. But I know you're low on time. To me it would be worth the cost to have the only badass ls1 in japan, but im hardcore like that. good luck and thanks for serving the country. we really appreciate you and what you do.
Wes
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Old Sep 19, 2007 | 09:38 PM
  #40  
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get rid of the stock coils and get a real spark/ignition system.
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