How To Get Rid Of Sluggish Coldstart/warmup And Bad Fuel Economy On Your Nistuned Rb20Det/z32/gtr Ecu.

[Rolls]

Myself along with pretty much every single rb20det ECU has had disgusting cold start and warm start performance, a quick check on nistune/ecutalk shows that timing is being pulled massively to warm the cat up. As our cats are mostly stuffed or people don't care I have a very simple solution that I have tested on my car.

There are two maps that cause this, one is called warmup timing, as you can see it dips down to 7 degrees timing, this means you get boost at cruise and then jumping performance when it jumps from this map to the normal timing map as you go from 7 degrees to 30 degrees once the load/rpm gets past a certain point, in the wet I found it down right dangerous as you are trying to pull out into oncoming traffic and it is gutless as f**k, then suddenly it kicks out of this map and you get on boost an spin the wheels. Now you can play with this map but I simply just "deleted" it by changing the constants which say when it is in use. The variables to change are "Warmup timing temp max" and "warmup timing temp min", the standard setting is 30c so you will often find the car drives great on a stone cold morning for about a minute, then this map kicks in. To disable the map just set the min and max temperature to 0 degrees, this way it will never be used. You may need to enable "Expert" mode in nistune as I'm not sure if all of these maps are accessible in the standard mode.

The next map to delete is the "BCADV after start timing" table:

This is a weird table where it is only accessed on warm start, eg if the car is between 60 and 85 degrees when you start it, so if you find you get odd performance after starting the car after it has sat for only 4-5 hours this is the result of this map. The way it works is actual timing = main timing table + (TADVC - BCADV), an example is at 40 degrees and 3000 rpm the timing = 35 (base timing at load load + (3 - 15) = 23 degrees timing, kind of confusing why they used 3 maps between 60 and 85 c but either way if you zero out the BCADV after start timing advance removes the warm start timing retard.

The code explaining this equation is as follows:

ldaa   X145D
ldx   #TIMING_ADVANCE
jsr   L809F
psha
ldaa   X1544
ldx   #$AFTER_START_TIMING_ADVANCE   
jsr   L809F
tab
pula
sba

In english that translates to:

LDX = Load TADVC timing value and store it in register A

PSHA = Store A on the stack

LDX = Load BCADV timing value and store it in register A

TAB = transfers A to register B

PULA = Get the variable on the stack and put it in register A

SBA = A - B and store it in working register

aka timing = (A-B), then we have to guess the rest but as there is obviously timing retard going on here, taking a few examples shows that it must be main timing + (A-B) to retard, any other combination results in an advance. As TADVC is 0 from 60c onwards it means this map is effectively all 0s as well as it only gets accessed if the car is already warm so the result is timing = main timing + (0-0)

Once you have burnt these changes to your ECU you can enjoy the car driving like it is hot on cold start and warm start! I gotta say it makes driving the car so much better, no sluggishness or jerkyness on startup. If you do a lot of short trips this will improve your fuel economy massively.

If you are running a Z32 or GTR ecu I recommend making these changes as well however the maps on these ECUs are far less aggressive on the retard ignition so the change will not be as dramatic. I'm not sure the reasoning behind why nissan did this but as you can see the Z32 has much nicer cold start timing maps, GTR is different again.

Z32 VG30DETT R32GTR

I have talked to pete/matt at nistune regarding this and their opinion is these maps were used to warm your cat up and don't serve much more purpose than this. Thread here:

http://forum.nistune.com/viewtopic.php?f=8&t=2715

Anyway hope this makes some peoples cars nicer to drive!

Edited December 14, 2013 by Rolls

[GTSBoy]

That's a good find. Strangely, I never had as much problem with is you seem to.

[Rolls]

I had two HR31 skylines with rb20dets, they were bad, but running my rb25det off a rb20 ecu it was even worse, two of my mates have the same issue however some cars it just doesn't seem to retard the igntion as much as mine did, there is some retardation but not all the way down to 5 degrees like the stock map shows.

Could also be your climate where you are and the car warms up very fast, it only stays on this warmup mode for maybe 5-10 minutes at max, I think because my radiator keeps the car super cool I have the car never getting to 85 degrees in winter which is why I had the most issues.

[GTSBoy]

I'm in Adelaide too Rolls.

[Rolls]

Who knows then!

[Ben C34]

Very interesting.

I would assume all Nissan ecus would behave similar, will be checking it out on my stagea ASAP.

Just to clarify, when you say delete you mean set all values to zero?

Ben

[Ben C34]

Wait, I spazzed out. We should set the constants so the map isnt accessed at all.

[GTSBoy]

Rolls had a mix of setting a constant to avoid using one map, and zeroing another map to remove its effect.

Edited December 14, 2013 by GTSBoy

[R_34]

I didn't felt my RB20 being sluggish during warm-up. But i always drive very softly with cold engines so maybe I couldn't feel this sluggishness.

That's surprinsing Nissan decided to use the first map only beyond 30°C, on a stone cold start, in regard to emissions I would have warmed the cat as fast as possible and killed ingnition from the start wathever the temperature.

The last two maps are more logical, but 85°C seems a little high to maintain cat warming.

What's the normal running temperature of an RB ?

I know the thermostat open at 76.5°C but i don't avec any probe that's tells me the temperature of the engine. Only the one on the dashboard which tells very inacurattely if the engine is cold or hot. No temperature numbers. And I don't have Nistune yet.

I've already felt that in cold climate the air coming from the ventilation is colder when the engine is just cruising, meaning the thermostat struggle to maintain working temperature. Still I didn't felt the engine becoming sluggish.

Does the map only kicks after a start, or each time the temperature drops below the temperature threshold of 85°C ?

[GTSBoy]

I didn't felt my RB20 being sluggish during warm-up. But i always drive very softly with cold engines so maybe I couldn't feel this sluggishness.

That's surprinsing Nissan decided to use the first map only beyond 30°C, on a stone cold start, in regard to emissions I would have warmed the cat as fast as possible and killed ingnition from the start wathever the temperature.

The last two maps are more logical, but 85°C seems a little high to maintain cat warming.

What's the normal running temperature of an RB ?

I know the thermostat open at 76.5°C but i don't avec any probe that's tells me the temperature of the engine. Only the one on the dashboard which tells very inacurattely if the engine is cold or hot. No temperature numbers. And I don't have Nistune yet.

I've already felt that in cold climate the air coming from the ventilation is colder when the engine is just cruising, meaning the thermostat struggle to maintain working temperature. Still I didn't felt the engine becoming sluggish.

Does the map only kicks after a start, or each time the temperature drops below the temperature threshold of 85°C ?

If you retard the ignition on a dead cold start, the engine isn't too hapy to run, especially with cold air. You need some advance to get it up and going. hen, once it's just warm enough to keep running, THEN you can switch over to cat warm up mode.

Normal RBs run at about 80°C. Neos run at about 90°C. They have a thermostat that's about 10°C higher opening temp - it's all about the fuel efficiency.

Oh, if your heater can't blow nice hot air in winter, then suspect your thermostat needs replacing. It's probably stuck open a bit.

Edited December 14, 2013 by GTSBoy

[R_34]

Good point about the engine stabilty running in cold temps. I should have thought in that before posting.

So RB runs in between 80 and 85°C or so. Thanks for the info.

The thermostat is brand new and it's a nissan one.

Only have 2000 km or so on it, the engine warm pretty quick and the water temperature seems stable no matter what I throw at the engine.

When decelerating the temperature doesn't seem to drop as it should when the thermostat is stuck open.

I have a 32mm copper core radiator and the clutch fan in the S13. It could explain things a little.

I had some problems with thermostats with my old CA, 2 stuck open and one which had difficulty to open leading to some overheating under sudden and long acceleration. And all of them showed signs of the problem. Actually the only sign I see is the air blowing from the ventilation being not as warm as i think it should. So to me it doesn"t quite look like an open thermostat.

I will try to measure water temp in running conditon to be sure. I just need a place to install a probe.

[GTSBoy]

Do you have climate control? The hot water valve is opened and closed by a little motor that doesn't have enough grunt to make the valve move fully once they get old and sticky. My R32 climate control is not too eager to open or close the valve all the way unless I excercise it a bit (ie drive it open-closed-open-closed manually a number of times until it frees up a bit). Otherwise in cold weather my heater seems a bit limp and in summer the air-con* isn't as cool as it could be (due to the valve still being open).

*Not that I've gotten around to getting my air con working for the last 2 or 3 years anyway! Should just pull it out.

[R_34]

Nope, I removed all the piping and radiator of the aircon, and there was no digital climate control in France, only the manual one where you switch the AC compressor on or off. Only the holes in the firewall are left, I use them to passe the cable for the gauges and the vacuum hose for the EBC.

The opening of the heater valve is manual and seems to works flawlessly, I don't have to force it to set it on hot or cold.

Your AC circuit might miss some refrigerant to make enough cold in hot weather. What wasn't working in your AC ?

In an LHD S13 the AC pipes goes over the turbo. It's not a problem as long as the car have the standard exhaust heat shield, the standard exhaust manifold and you don't have tu change the turbo.

I changed the turbo once with the AC, when the second T25 let go I pulled all the AC stuff. I twas a pain in the ass to work on the hot side of the engine with it.

Restropectively I should have kept it, I miss it sometimes.

[KiwiRS4T]

Another reason not to fit those "low temp" thermostats.

[Manuel Kasko]

Rolls I have been suffering from this exact issue! I think last time we spoke about it you described it as similar to towing a trailer and then the car just releases it.

It's been shitting me so much because sometimes driving on the highway in the morning I can feel it swapping between the two and my car just goes gutless then back up and gutless again.

Makes it really annoying driving in the mornings in ACT

Also it's exactly as you described with the 1min before it swaps to the map. I'll be cruising out of my street and then boom the car goes sluggish.

Does it have any relation to RPM because I find it feels a little less like a slug when I slowly bring it to 2500-3000rpm it frees up again

[Manuel Kasko]

Using an R32 ECU with nistune and window switch

[R_34]

Look at the first map on the first post. The ECU bring back some spark advance beyond 2500 rpm.

+1 with these low temps thermostat. I've never understood why they want such a low temperature regulation. It worsen the efectiveness of the radiator just to bring back some water flow ?

You loose the control of the temperature quicker that's all.

It's like going down on injectors size to get them static sooner just to be sure to get the most of it.

A total nonsense in performance point of vue. Getting a bigger radiator, sticking with the clutch fan, improving airflow over the radiator and under the hood. That's what makes the differences and really improves the cooling.

Edited December 14, 2013 by R_34

[GTSBoy]

Your AC circuit might miss some refrigerant to make enough cold in hot weather. What wasn't working in your AC ?

No. There's a 100% charge of refrigerant in my system right now. Known, tested and proved not to leak. The result of a Neo transplant and having to remake the air-con hoses several times to stop them leaking. But I never got around to finishing the last bit, which is the last few wires to make it work.

[Missileman]

Thanks Rolls, been wondering for a while WTF is going on, thought it was just me. Will have to fix my thermostat too, it's either been changed to low temp one or is stuck slightly open, probably the later. I do mainly small trips so I have a hard time getting over 400ks a tank.

[Rolls]

Rolls I have been suffering from this exact issue! I think last time we spoke about it you described it as similar to towing a trailer and then the car just releases it.

It's been shitting me so much because sometimes driving on the highway in the morning I can feel it swapping between the two and my car just goes gutless then back up and gutless again.

Makes it really annoying driving in the mornings in ACT

Also it's exactly as you described with the 1min before it swaps to the map. I'll be cruising out of my street and then boom the car goes sluggish.

Does it have any relation to RPM because I find it feels a little less like a slug when I slowly bring it to 2500-3000rpm it frees up again

Yep the max rpm is 2850 rpm, and it also gradualyl gives advance back before that, but you'll stick get a kick when going from about 2800 to 3000, also if you get the load above the TP MAX limit it will also kick out of the map, so if you are getting boost or > 2800 rpm it will kick out of the map.

I also suspect my thermostat is leaking when cold because I feel my car takes longer to warmup than it should, probably making the problem worse than it should be.

Edited December 15, 2013 by Rolls