R32 Cold Running Update

[Slim Mat]

Hi all,

been a while since I have posted here. It's good to see the community is still strong. New GT-R looks good too.

This is an update for the topic of R32 GT-R's running badly when they are cold. Most posts involved complaints of the car surging and a coughing sound coming from the engine bay, with decreased performance, then at a certain point everything would go normal like a switch had been thrown.

After a bit of testing using my Power FC, I think I have come up with an answer.

I noticed that when I installed the power fc that the problem went away. It makes me think that the problem lies in the standard ECU, sorry guys, bad news for some because there is probably nothing you can do about it. It has the very similar aspects that bad IGNITION TIMING has, as in, the ignition timing when it is cold is retard up to shit.

This explains the lack of power and the coughing(sort of acting like antilag on rally cars, where the turbos is spooling really low in the rev range). What is happening is the ECU is retarding the timing when it is cold, then when it hits a pre-programmed temperature it changes it to normal. Power FC's are programmed differently and that's why it goes away, although if you played around with the warm up setting you could get it to do the same thing. I think it is coolant temperature correction....

If anyone thinks they can expand on this, feel free to add to this topic.

[Syphon]

Interesting topic to come up. I have an r33 with an rb20 remap in mine and am having a very similiar issue. Cold start the exhaust note "sounds" different and as you take off the turbo spools very loud, no power and all of suddden like a light switch it takes off. I have seen the issue with consult plugged into the laptop and the timing sits dead flat on 7 degrees btdc, then like a light switch at about 2200rpm, hits 30-40 degrees btdc and off it goes. If I shut the car down and restart it, 85% of the time the car will then drive normally.

I know for a fact with my car that the knock sensors are faulty and am yet to bypass them in the next week to see if the problem goes away. Keep in mind mind the Power FC will not adjust the map accordingly if it senses knock, all it does it display the level of knock, unlike the standard ecu which will pull timing and add fuel as far as I gather. It's possible that the motor is a little noisy on startup and dropping the ecu into the knock map. Rather weird issue and I am clutching at straws but bypassing the knock sensors will definately tell me if that is causing the issue.

I have seen my ecu produce 2 faults, one was knock sensors, the other was ignition signal. CAS possibly playing up....maybe, although i tend to think not. I need to look into the ignition signal fault and see what variables the ecu looks for to see why this would be produced. My alternator is also a little suspect.

Maybe grab consult, a laptop and cable and whack it on your car before a cold start and see what fault codes come up?

[bradsm87]

I had that EXACT same problem in my S14. Mine also went away with a Power FC.

[infamous_t]

Probably due to Power FC being properly tuned for the car, therefore when its running rich while warming up(cold start), its better suited to the modifications of the car.

Might find guys running remaps/NIStune etc. don't have these issues (if tuned properly).

I don't think this is a inherent flaw with the stock ecu, but more a symptom of Nissan's 'safe' factory tune.

[SLIPPERY]

untuned PowerFCs fix the problem too. Much better cold running than stock ecu out of the box! Terrific stuff

[Slim Mat]

  SLIPPERY said:

untuned PowerFCs fix the problem too. Much better cold running than stock ecu out of the box! Terrific stuff

Yeah, you are right. My Power FC is untuned and the car is not modified.

[Bumblebee]

My gtr doesnt do any funny stuff at all when its cold... ever

its never done anything funny at any stage... ever

its gotta be something else, not ecu related

possible its a sensor malfunction that the fc doesnt rely on heavily.. like the knock. factory ecus run the cars off the knock whether the fc doesnt. atleast from what ive read. theyre like a switch.. either its knocking or its not knockin enough for it show up *shrugs*

Edited April 7, 2008 by Bumblebee

[bubba]

It's just cold start, I don't see what the big deal is. I've seen it mentioned many many times before, you shouldn't be driving your car hard until it's warm anyway so just deal.

My car has always done it, stock RB20/ecu and now with RB30/remapped ecu, until coolant is up to temp it's in "cold start" and drives like a pig with more than say 5% throttle, so I just don't rev it over 2000rpm or use much throttle until it comes out of cold start.