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sounds like the first one works similar to a standard narrowband in that it slowly trims fuel to get the desired afr and then constantly adjusts to keep it there

second one sounds like it reads the afr, calculates the difference from the target afr and then calaculates how much to trim from that and applies it.

personally i run about 13-13.5:1 at idle to stop misifirng (weak ignitor) and aim for around 15:1 under light load cruising

Ok cool. Well at the moment mine is set to that first one. I have mine at around 14:1 at idle and it seems to like it. So 15:1 is allright for light load cruising? I started setting it up for around 15 for better economy but wasn't sure if that was a bit much.

Basically finishing off the tuning on my car and want it running nicely. Have learnt a lot about using the Vipec and loving it more that I use it. The datalogging is a lot of help when doing it by yourself. At the moment going through all my logs to see how the tune is.

Also in terms of ignition timing at light loads, 20-25 degrees is about what you guys run?

I wish we had like a tuning section on the forums to learn as much as you can. There is bits here and there through Forced Induction but would be good to have it all in one place.

ERD is correct about the Sards. The 800cc side feeds are even worse.

A very easy way to test it let the engine become stable at idle, at operating temp.

Start to lean the mixtures out. Just about any RB engine should be able to idle at 16.5:1 with no dramas. Even with Cams 15.5 should be a walk in the park.

What you will probably find is as you drop your injection time you will start to get cylinders that start to fall over. This is your latency. Some injectors do it worse than others.

I have seen as much as 5.5 MS of injection time under crank conditions and the injectors didn't open. As tested with a PICO scope and current clamp.

Lean mixtures are something that should be done on a dyno too. Ill quickly show you why.

Lets say you are at 3000 rpm. and 20% throttle generating around 15 rwkw

AFR is 12:1 injection time is 3.00 MS

Now if you lean your mixtures out, to say

12.7:1 and your injection time is 2.70 MS still making 15 rwkw, then you save 10% fuel.

Now you go further lean it out to 14.5:1 at 2.00 MS. Thats 26% decrease in fuel, say you now make 13rwkw. Thats a 13% loss in power. We are still sweet.

If you then go to 15.5:1 at 1.90 Ms and your power drops to 10RWKW, Well now we have a 5% loss in fuel, but a 23% loss in power.

When your fuel decrease by percentage is greater than you power decrease by percentage then you are on the right track.

yer 20-25 would be very doughy off boost. i run as high as 50 degrees under light load. more timing makes a bit difference to response and economy.

light load ignition tuning the same as WOT tuning, but usually with much higher timing and more often than not you reach MBT before it pings. i dont have a dyno for measuring MBT so usually just stick to a basic rule of around 40 degrees at 1200rpm slowly working up to a max (sometimes less) of 50 degrees at ~4000rpm. maybe just stick to <45 if your not too sure.

Lean mixtures are something that should be done on a dyno too. Ill quickly show you why.

Lets say you are at 3000 rpm. and 20% throttle generating around 15 rwkw

AFR is 12:1 injection time is 3.00 MS

Now if you lean your mixtures out, to say

12.7:1 and your injection time is 2.70 MS still making 15 rwkw, then you save 10% fuel.

Now you go further lean it out to 14.5:1 at 2.00 MS. Thats 26% decrease in fuel, say you now make 13rwkw. Thats a 13% loss in power. We are still sweet.

If you then go to 15.5:1 at 1.90 Ms and your power drops to 10RWKW, Well now we have a 5% loss in fuel, but a 23% loss in power.

When your fuel decrease by percentage is greater than you power decrease by percentage then you are on the right track.

That's very interesting, never thought about it like that!

yer 20-25 would be very doughy off boost. i run as high as 50 degrees under light load. more timing makes a bit difference to response and economy.

light load ignition tuning the same as WOT tuning, but usually with much higher timing and more often than not you reach MBT before it pings. i dont have a dyno for measuring MBT so usually just stick to a basic rule of around 40 degrees at 1200rpm slowly working up to a max (sometimes less) of 50 degrees at ~4000rpm. maybe just stick to <45 if your not too sure.

Yeah I set the ignition timing values fairly lowish to make sure it didn't ping. Definetely is doughy compared to back in the day on the Microtech tune haha. Will have to borrow a mates Kmon to do the timing properly.

Atleast now I have a better idea of what kind of values to use. Wasn't really sure on what people use and I couldn't find a timing map that some one had tuned searching through the forums to get a better idea.

Another quick question regarding timing on idle.

On your map you have like 42-45 degrees at idle. Does the car actually run that much timing on idle, or does it not adjust timing from the map when it is in idle?

If so, what does running advanced timing on idle actually do?

Just trying to get my head around this at the moment because I think I have confused myself.

n2 p2 is idle for rb25s, which is 15 degrees. regardless, the pfc goes into closed loop at idle and ignores the map. it'll adjust timing a little to keep idle at the target you set (usually ~850rpm).

having said that myne usually idles a touch higher at around 1000-1100 and timing still sits dead on 15 until you touch the throttle, pfc idle control can be a little shitty sometimes.

Ok well that clears that up a lot.

I'm just doing 3D mapping of my fuel map and ignition map to smooth it out a bit more and was wondering about the ignition timing at idle. I thought timing wasn't adjusted on idle due to it going into closed loop, but then thought you might be running 42-45 degrees on idle and wasn't so sure if I was right or wrong! Didn't realise on the FC the idle was so low to the edge of the table.

  • 4 months later...

Greetings from Canada, eh?

We've got a few VIPEC dealers up here but tuning seems to be an issue; particularly, R32 GT-R's (RB26DETT) with mild->medium mods (400-600whp).

Asked around and gotten a few (very general) opinions re: AFR, & 4D tables but nothing real to compare our values with (except each others). Common problems are running rich; we are using 2 or 4-wheel dynos w/wideband and trying to get the fuel trim right but I think we need to start from scratch with new AFR table, rework the 4D and move on from there.

Anyone got some sample VIPEC config files we could check out? Tuners have been taking a stab at this for a few years now but not making much headway. Don't get me wrong...cars run but not nearly as well as they could. Tireds of washing soot off of my bumper and watering-down my oil.

I hear this is the place to get VIPEC info....the place where they're made! Let's hear what you got...

Much appreciated

On some GTRS (very rare) the map signal is weak (map trace runs through same spot in cruise as on accel) so i run a separate 4d or 5d map which corrects on TPS vs rpm this is scaled to give great resolution in the areas i could not get perfect in the main map, this can sort fuel consumption issues and liveability issues around 0 atmo on the map

make sure your tps level is set to exit the 4 or 5d map under 2/3s (approx as varies car to car) of full load.

This keeps your fuel trims on closed loop to under 3% yet has no effect on accel maps.

here 1 of my maps, cant remember exactly what stage it was at at the time but it gives you an idea.

ignmap2.jpg

Hey reduce your lead up timing, it will make the car heaps more responsive.... its upto 20degrees too advanced in some spots.

Keep the info and tuning tips coming guys! Some mighty interesting info here!

STATUS, hey Trent, how does one determine if timing is overly advanced? Is there a way to do it without dyno?

Hey reduce your lead up timing, it will make the car heaps more responsive.... its upto 20degrees too advanced in some spots.

i ended up trimming it back a little, that maps nearly a year old now. it originally had around 20-25 degrees less around that whole area and i find it 100 times better to drive like this, throttle response is a heap better and makes noticeably more torque. although i did overdo it a little, hence why i trimmed it back.

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