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Jon

Tips for a noob with a new G4+

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Hey guys

I've recently pulled an ancient G1 out of my car and have put in a G4+. Since the G1 was pre-pc tuning days (2001-ish) it wasn't possible to export the tune off the old one. I've got it started and running with the rb25 base map provided, but the problem is the engine tries to stall when it gets any kind of throttle, i.e starting and running at full vacuum is fine but once it gets near atmospheric pressure it just stalls. What should i be looking at here? Do the default settings have it trying to run off the original AFM even though it already has a MAP sensor?

The main problem for me is the car is stored some way out of town so I need to get it somewhat drive-able so i can get it into town to a tuner.

The engine is basically an rb25det minus the vct, running some oddball 390cc injectors, apart from that you could say it's pretty much stock, as far as the ecu will be concerned. I'm assuming there may be some part of the base map that doesn't agree with my setup. Apologies for the noob questions and thanks in advance :)

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Calibrate the TPS

Check the base timing

Then check the mixture at idle and adjust the master fuel to get it ok.

Allow the engine to warm up and then see if it will take throttle.

 

 

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Thanks for the response Simon

TPS is calibrated, base timing is good and advance looks to be working fine as the rpms are lifted.

Default master fuel value was on 7 which is horribly rich for my setup, took it down to 5 i think before the idle smoothed out and black smoke disappeared.

I haven't touched the existing MAP sensor, which is likely to be as old as the G1 link that was in it. Is there likely to be any compatibility issues there? i don't know what scope that one has, should i need to set that somewhere i.e do i need to tell the link whether it's a 1bar or 3bar sensor etc?

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Jon, what ECU do you have - is it a PNP or wire in?  Can you check if the MAP sensor has any numbers on it or maybe post a photo?

A quick n dirty check you can do on the map sensor calibration is to view the "MAP" runtime value on the main tuning screen, like below:

Capture.png

With ignition on and engine not running it should read about 100KPa (+/-~10).

Then if you suck on map sensor hose with your mouth you should be able to pull it down to roughly 70KPa, and if you blow, about 115KPa at a guess.

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Hey Adam, it's a pnp gts-link.

I'm pretty sure I was getting a static MAP reading with the key on of 99kpa.

That's a neat trick with the vacuum hose, I'll test further when i can get out there next, probably on the weekend.

Also I was getting a fault code for the stock o2 sensor at 0.00 volts - she's a dud. I've got a spare so will replace that but I didn't think that could be causing this issue, correct me if i'm wrong.

Thanks very much :)

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Jon,

Assuming your GTR/GTS plugin is reasonably new, it should have a map sensor built in the ECU (I think from memory some old revisions might not have had the built in MAP).  Can you check if yours is as pictured below, the red circle is the MAP sensor, this is where your vacuum hose should attach, it sounds like you might be assuming some other sensor in the engine bay is the MAP sensor?

BTW, The fault code for the O2 sensor is not part of your problem so you can ignore that.

ngtrplusboardheader.jpg

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Yep the ecu is brand new. I didn't realize it had an on-board MAP, I was assuming it ran off the external map sensor like the old G1. The manual seems pretty light on details around this, all mention of map sensors seem to refer to externals.

I don't suppose you know what size ID/OD vacuum hose it takes?

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It is mentioned in the Help file for the GTR plugin but I agree it is not particularly obvious, I havent seen the paper manual for a long time so I'm not sure how clear or unclear that makes things.  

4mm ID hose is what you want.

Once you connect this MAP sensor you may have to put your master fuel number back to where it was originally but it will hopefully now run pretty reasonable. 

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Have sorted this. The engine runs reasonably well on the base map after connecting the onboard map sensor instead of the external. Had to adjust the master fuel up considerably as the default setting was getting nowhere near enough fuel and would stall moments after starting. Not much left to do now before I can get a tune!

Cheers for the help

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hey guys

i'm having further issues with this. turns out we fixed one problem but now i've tried to get the car back into town the other night and discovered that it only runs ok while cold. it seems that once above about 40~50 degrees the fuel leans off enough to stall it, and dies instantly with throttle. i'm able to start the engine again but if its warm then it will die a moment later. this tells me crank enrichment is probably the only thing that's getting me going in the first place. i'm running pretty much just the included base tune on the G4+ on what is essentially a pretty stock rb25det. i haven't played with any major settings other than calibrating the tps & map. i found that if i wound up the master fuel to 40 (normal ~14) it would idle rough but i could at least drive it around the property at idle and it wouldn't stall. will still stall if i give it more than about 2% throttle.

everything worked fine until i put in the G4+ so i'm confident this is just a tuning issue. i'm guessing the fuel tables on the base tune don't work all that well with my setup. anyone able to offer some suggestions on what i should be looking at or maybe some resources i could learn basic tuning from? i just need to get it to the point where it can be driven into town for more work and a tune (about an hours drive). 

thanks!

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Can you do a PC Log of it idleing for a couple of minutes.  Post that and a copy of your .pclr (map) here and one of us will take a look.

How to do the PC log: https://www.youtube.com/watch?v=_P1LRANeO4A

Hey Adam

Here's the tune and the logs of this happening. Today it's happening when the engine is pretty much still cold. Not sure what other info is relevant but it's really an rb25de+t and is running 390cc injectors currently. Let me know if there's anything else you need.

Thanks!

r32tune.pclr

Log 2017-05-14 2;50;53 pm.llg

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Hi Jon,

I dont see much wrong with your map or log.  Pulsewidths etc look kind of realistic and dont change significantly when the engine starts to die.  Have you got someway to check fuel pressure remains when it starts to die?

The only thought I have is maybe the post start enrichment table is not well suited to your engine, I can see in the log that post start enrichment is starting to pull a little fuel out when it dies.  One thing to try is a bigger master fuel number (say 25% bigger) and see if that helps get it through the transition from post start enrich, warm up enrich to normal operating temp It will run rich when cold but it might need that so you can get it warm and start tuning.

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thanks adam

my thoughts also on the post start enrichment. i have already tried winding up the master fuel way beyond 25%, to the point where the idle got very lumpy, and it would at least stay running but the moment you give it any accelerator it dies again. it also seems the warmer the engine gets the worse the problem becomes. once warm it will only start, then die instantly. if i can't sort it, i may even resort to putting the g1 back in it so i can at least drive it back into town and get to a tuner.

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Hey guys

Bit of an update. About a month after the last post, the car was stolen. Since the car didn't actually run properly they didn't get far with it but that didn't stop them from taking my ECU and everything else they could carry. While I was lucky enough to get the car itself back, I'm now back to where I was a year ago in regards to tuning. Same problem exists except now i don't have the option of putting the old G1 back in it since the old map sensor was among the parts they took.

One thought I have is that whoever did the original G1 install had the old external MAP sensor wired directly into the factory r32 AFM plug, does anyone know if that's normal and would they have had to modify the loom for that to work with a G1 plugin gtslink?

I think the key thing to note here is that it did run fine on the old G1 with the external MAP sensor so i'm sure there is some difference with how something is connected now vs then. The only way i can get it running is to up the master fuel value to 35-40ish and almost gas myself to death in the garage.

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I have another G4+, just as before. The old map i'm referring to is the external MAP sensor I was running with the old G1. It hasn't worked right since i first changed to a g4+ (and removed the external MAP from the g1)

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to clarify, yes i am using the internal map sensor on the g4+. the external sensor has not been used since the g1 was in it.

my question is: was the external map sensor typically wired in separately or was it normal to wire it in to the factory AFM plug? i didn't own the vehicle when this was done so i don't know if they might have made other wiring changes to accommodate their use of the AFM plug, and could that be causing my issues now.

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Yes with the G1 it was common to wire the MAP via the old AFM plug.  That AFM plug is still connected to an AN Volt input in the G4+ ecu but it wont be doing anything unless that AN Volt input was turned on and set up.  So this is not your problem.

Have you checked base timing etc?  Do all sensor values look realistic and normal when its running?  Can you do a log and attach that and your map.

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Ok cool thanks. Good tip on the timing, i've just read more into that and yeah the process i'd used for setting the timing might not be right.. i'll give it another go tonight and see what happens

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