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Rb25 neo issues


lucask
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I’m having some trouble getting to the bottom of an issue I have with an rb25 neo. It’s in a GU patrol. It idles fine, free revs fine but as soon as I put any load on it it goes for a few seconds then dies, coughs splutters etc. if I then put the clutch in, it takes a bit of time to recover. It’s pretty much undrivable. It did have the boost sensor hooked up wrong and the the afm has been replaced and now neither throw codes. Only codes at auto trans code, but it’s manual anyway. I assume just a auto ecu. Any ideas would be appreciated.

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Did it come from a GT-T? Had traction control and ABS originally? Is the ECU Nistuned?

If you answered yes to either of the 1st 2 questions and no to the latter, then you're f**ked. The stock ECU will pack a sulk if you don't have the traction control CU and the ABS CU all happily talking to it.

If you have Nistune, you can cancel that shit out and make it work.

 

Has it been working before and is this a new problem, or has it never worked?

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Yes from a GTT, no idea if it had tcs, but it does have the 2nd throttle body. No idea if it’s nistuned, I should crack the ecu open and have a look. It has gone in the past I believe but whether the ecu was changed or something I wouldn’t know. I bought it as is. 
Would it create the issue I described if it wasn’t nistuned?

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3 minutes ago, lucask said:

Would it create the issue I described if it wasn’t nistuned?

Probably. They really pack the sulks in hard if not given everything they want.

Of course, there could be heaps of other problems. Dose's suggestion above is really sensible, because it cuts through a whole pile of shit you have to wade through if trying to get a stock ECU'd transplant working in a foreign car. There are so many things that can trip you up.

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3 hours ago, GTSBoy said:

Probably. They really pack the sulks in hard if not given everything they want.

Of course, there could be heaps of other problems. Dose's suggestion above is really sensible, because it cuts through a whole pile of shit you have to wade through if trying to get a stock ECU'd transplant working in a foreign car. There are so many things that can trip you up.

So it looks like it has a nistune type 4 board in it. Can the traction control definitely be turned off with the nistune software? I guess logging in and seeing What the nistune  shows would be a good start to diagnosing what’s wrong. Will need to get the software

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Once you get the Nistune software, make sure you carefully read the GT-t guide.

It's a  c  u  n  t  to get right, make sure you also read the latest version of the guide as the older one just advises you to set the boost cut to 255, map sensor voltage to max and to unplug it (this actually causes more issues than it solves, as you always hit the very last load row as boost comes on).

As much as I love Nistune (also I can supply), I hate it in R34 GT-ts, it's just is a pain in the anus to tune and actually work.

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7 minutes ago, Dose Pipe Sutututu said:

Once you get the Nistune software, make sure you carefully read the GT-t guide.

It's a  c  u  n  t  to get right, make sure you also read the latest version of the guide as the older one just advises you to set the boost cut to 255, map sensor voltage to max and to unplug it (this actually causes more issues than it solves, as you always hit the very last load row as boost comes on).

As much as I love Nistune (also I can supply), I hate it in R34 GT-ts, it's just is a pain in the anus to tune and actually work.

Does this guide come with the software? 

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14 minutes ago, lucask said:

Does this guide come with the software? 

It's available online here with some notes too:

https://forum.nistune.com/viewtopic.php?f=12&p=25972

Just note the Nistune cable and software does add up, so weigh out the pros/cons before starting.

As much as I love Nistune with its flex capabilities, 3Dx boost tables, super rudimentary engine protection, the R34 NEO ECU is just so hard to work with, especially when you're running big boost and it just always kisses the last TP Load row.

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15 minutes ago, GTSBoy said:

But for mild engines it's not as much trouble. So it depends how hard you want to lean on it too.

Actually just did another check and get code 44 and 46 and then constant check engine light which is the traction control as you said. Is it likely the issue is it’s in limp mode? Is that what limp mode does? It will be a mild engine, it’s just in a patrol. I have another car with a 25/30 which Has a haltech which I will go crazy on, this is just for the bush lol. 

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It's not really limp mode. It's just the ECU chucking the sads. they don't cope. You have to go into the DTC stuff and switch off the offending codes. The doco should tell you how.

I have a Neo in an R32. No TCS, no ABS. I had to fix all that stuff. It also pays to get the Nistune board programmed as a Stagea in the first place, because they don't have TCS.

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If you have the boost sensor connected to the plenum and reading vacuum it will cause the issues you've described. It needs to be plumbed to the charge pipe pre-throttle so that is something to double check.

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