G35 Sedan at Cobb with blown motor need advise
11-18-2009, 06:21 PM
#61
Since all of us are just speculating, let me add my .02 of speculation.
First, Cobb has some pretty smart guys and tuners working for them. They know how to tune a car, as I've spoken to many of the key tuners/calilbrators over there. You would have to do something incredibly stupid to break a Vortech SC engine with a few pulls on the dyno. And I just don't see Cobb's tuners doing this.
To literally snap a rod, something else was likely a contributing factor. Perhaps a spun bearing, low oil pressure, weak factory rod? I have pulled apart motors that "seemed" fine only to find a few wavy rods. And it would take some monemental audible pounding to damage a bearing with a few pulls on the dyno.
First, Cobb has some pretty smart guys and tuners working for them. They know how to tune a car, as I've spoken to many of the key tuners/calilbrators over there. You would have to do something incredibly stupid to break a Vortech SC engine with a few pulls on the dyno. And I just don't see Cobb's tuners doing this.
To literally snap a rod, something else was likely a contributing factor. Perhaps a spun bearing, low oil pressure, weak factory rod? I have pulled apart motors that "seemed" fine only to find a few wavy rods. And it would take some monemental audible pounding to damage a bearing with a few pulls on the dyno.
11-18-2009, 08:56 PM
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Since all of us are just speculating, let me add my .02 of speculation.
First, Cobb has some pretty smart guys and tuners working for them. They know how to tune a car, as I've spoken to many of the key tuners/calilbrators over there. You would have to do something incredibly stupid to break a Vortech SC engine with a few pulls on the dyno. And I just don't see Cobb's tuners doing this.
To literally snap a rod, something else was likely a contributing factor. Perhaps a spun bearing, low oil pressure, weak factory rod? I have pulled apart motors that "seemed" fine only to find a few wavy rods. And it would take some monemental audible pounding to damage a bearing with a few pulls on the dyno.
First, Cobb has some pretty smart guys and tuners working for them. They know how to tune a car, as I've spoken to many of the key tuners/calilbrators over there. You would have to do something incredibly stupid to break a Vortech SC engine with a few pulls on the dyno. And I just don't see Cobb's tuners doing this.
To literally snap a rod, something else was likely a contributing factor. Perhaps a spun bearing, low oil pressure, weak factory rod? I have pulled apart motors that "seemed" fine only to find a few wavy rods. And it would take some monemental audible pounding to damage a bearing with a few pulls on the dyno.
Thank You for your input and for chiming in. It's sad to think I just got a week motor but it's a crap shoot a very expensive crap shoot.
11-19-2009, 06:45 AM
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11-19-2009, 10:28 AM
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If you have concerns or issues about your tune, please don't hesitate to give us a call at (214) 291-3020 or visit our website at www.cobbtuningplano.com for further contact information.
There are many reasons why an engine may fail, especially when you are adding forced induction to a normally aspirated engine. We are fully confident in the AccessPORT and AccessTUNER tools when it comes to tuning forced induction on the VQ engine.
Have you considered oil analysis? This might give you some clues into why the engine failed. Generally, engine failure in the bottom end is due to oiling issues or a bearing failure. We are happy to help you diagnose this failure and solve these issues. If forced induction is a long-term plan, you might consider upgraded internals.
Travis
COBB Tuning
There are many reasons why an engine may fail, especially when you are adding forced induction to a normally aspirated engine. We are fully confident in the AccessPORT and AccessTUNER tools when it comes to tuning forced induction on the VQ engine.
Have you considered oil analysis? This might give you some clues into why the engine failed. Generally, engine failure in the bottom end is due to oiling issues or a bearing failure. We are happy to help you diagnose this failure and solve these issues. If forced induction is a long-term plan, you might consider upgraded internals.
Travis
COBB Tuning
11-19-2009, 10:48 AM
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Timing control and the AccessPORT
This is Tim Bailey - I am a calibrator working for Cobb Tuning. My main focus is the GTR but i also know the NA nissan ECU very well.
I don't know the details of this specific tune so i can't speculate exactly what went wrong. But, i can tell you about how the AccessPORT full controls ignition timing. The AccessPORT and Cobb Tuning tools are used to write new tables inside the ECU. We do not tune off or blunt the excellent factory ignition timing knock control. In fact, we generally expand the RPM and load range of the factory knock control system to be more conservative. Generally speaking, when we tune for forced induction, as a starting point we lower higher load timing tables by as much as 30%. So, the timing would have been conservative as a starting point.
What many of you may not know is that nissan uses a highly sophisticated and active process to dynamically calculate timing. To be more specific, ignition timing is constantly calculated based information from a wide array of sensors. This calculation uses the timing tables as a reference but has the ability to adjust timing toward ideal throughout every combustion cycle.
All of this information taken together suggests that its unlikely the tune killed the motor. However, i'd need to see logs to make a more accurate assessment. In my opinion, 13 pounds of boost is too much for a stock NA nissan motor. I would not recommend going more than 8 on a stock block.... but, i am by nature VERY conservative in my own tuning practices.
If anyone has a question related to nissan tuning with AccessPORT you can feel free to contact me directly as i do not regularly check PMs...
Best regards
Tim Bailey
http://surgeline.cobbtuning.com/
I don't know the details of this specific tune so i can't speculate exactly what went wrong. But, i can tell you about how the AccessPORT full controls ignition timing. The AccessPORT and Cobb Tuning tools are used to write new tables inside the ECU. We do not tune off or blunt the excellent factory ignition timing knock control. In fact, we generally expand the RPM and load range of the factory knock control system to be more conservative. Generally speaking, when we tune for forced induction, as a starting point we lower higher load timing tables by as much as 30%. So, the timing would have been conservative as a starting point.
What many of you may not know is that nissan uses a highly sophisticated and active process to dynamically calculate timing. To be more specific, ignition timing is constantly calculated based information from a wide array of sensors. This calculation uses the timing tables as a reference but has the ability to adjust timing toward ideal throughout every combustion cycle.
All of this information taken together suggests that its unlikely the tune killed the motor. However, i'd need to see logs to make a more accurate assessment. In my opinion, 13 pounds of boost is too much for a stock NA nissan motor. I would not recommend going more than 8 on a stock block.... but, i am by nature VERY conservative in my own tuning practices.
If anyone has a question related to nissan tuning with AccessPORT you can feel free to contact me directly as i do not regularly check PMs...
Best regards
Tim Bailey
http://surgeline.cobbtuning.com/
11-19-2009, 01:48 PM
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Thank you very much both of you for chiming in and help answer some questions I and others have. Depending on who you talk to the VQ's block are fairly strong and some hold up just fine to 13psi, I guess mine obviously couldn't so I will be going back with a built bottom end. Kirk
11-19-2009, 03:00 PM
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13psi...lol When the SC starts go by psi like turbo cars? with vortech/2.87, you may not even hit 13psi all the time.
Edit: after read 350z400whp, i forgot about airflow/psi too. lol
Edit: after read 350z400whp, i forgot about airflow/psi too. lol
Last edited by Chef-J; 11-19-2009 at 03:40 PM.
11-21-2009, 02:34 PM
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Advise Needed
So I am still very unclear on what to do next. So should I try to find a used motor or short block and run the stock pulley with it for more reliability. Also what do yall think about built blocks long term issues or reliability challenges? I am looking into 3 shops if I go the built route. They are fail safe performance, Jonny Tran, or Uprev. I am sure it's going to take a while at any shop but around the holidays it will certainly take longer. Should I just do it myself and then send it to Jared at Uprev to get it tuned with the stock pulley? Please help I am even more confused then I was. As always thanks for everyone's help and advise. Kirk
Last edited by Kirks06; 11-21-2009 at 02:39 PM.
11-21-2009, 04:19 PM
#74
id just get another stock longblock, take yours out bolt it in with the vortech kit on it and 3.12 pulley which is gonna get u about 9-10 psi and run it with a good solid tune, dont mess around with the stock pulley its too weak ..ive ran mine for over 10k miles knock on wood issue free at 9.5-10psi stock block...very reliable and rips pretty good for what it is i guess..
Last edited by tylerxfire; 11-21-2009 at 04:20 PM.
11-21-2009, 06:09 PM
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Imo...
3.33 and stock block = around 350whp. (which means, you don't need all that support mods that you have.)
2.87 and stock block = 400whp and cheaper way to go
Build = now...SC gets an expensive. Not just short block, needs head jobs to make money worhty. And top of that its better upgrade blower for better power.
End of day, its up to owner's budget and goal. DIY isn't easy, it may takes longer than shop does. Also it may gives you more stress than when you did SC.
3.33 and stock block = around 350whp. (which means, you don't need all that support mods that you have.)
2.87 and stock block = 400whp and cheaper way to go
Build = now...SC gets an expensive. Not just short block, needs head jobs to make money worhty. And top of that its better upgrade blower for better power.
End of day, its up to owner's budget and goal. DIY isn't easy, it may takes longer than shop does. Also it may gives you more stress than when you did SC.
11-25-2009, 08:53 AM
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Well I have decided to send my car to Uprev to get everything done there. They will be installing a built small block from importparts pro. I am going to stick with my current setup, so 2.87 with the gtm pulley mod, with meth/water injection. Hopefully they can have it done by middle of Jan. Thanks again everyone for all your support and advise. My goal is to have a powerful but balanced road racing car. 
12-04-2009, 08:21 AM
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Update
Well things are moving forward now, the motor is being built by Import Parts Pro and the car is going to be shipped down to UPREV in Austin next week, so they car start pulling the motor out and check everything to make sure there is no other engine damage.
12-11-2009, 07:08 PM
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congrats on getting the new motor! i have a SC i plan on putting on, almost makes me think twice... i have the bigger pully and getting an osiris tune.
if you dont mind my asking, how much is the new engine gonna cost you?
if you dont mind my asking, how much is the new engine gonna cost you?
12-12-2009, 08:47 AM
#79
u have a g35x and u have a supercharger kit for it? which kit im very curious to know as ive never seen a kit for the car? and a bigger pulley would make less boost...smaller pulleys make more boost...also there are a ton of different factors which are gonna play in to the cost of a new motor like if its a built shortblock or longblock and what parts are used..
12-14-2009, 05:31 AM
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The new engine is going to run about 6K and I am getting just the short block so they are going to reuse my heads. I am sure there will be over runs there always are. I just want to drive my car again. I miss her so. 