Thread: Timing opinions for rebuild

Hey everyone, I should have my engine ready to reassemble in just a couple of weeks. I'm trying to work on my tune now and I have a couple questions regarding timing since I am changing compression.

I'm throwing in some DET pistons, I just need some opinions or ideas as far as the timing maps go. I have a U13 DET ECU currently with a Calum Basic, GTi-R T28, GTi-R intake manifold and 444cc injectors, and am currently only running 7lbs, but plan on running 12lbs as soon as I can get a boost controller.

I figure I have two options. I can either:

1) Use a stock U13 timing map since it was 8.5:1 to my knowledge, and then turn it down just a bit in the top-end since I plan on raising the boost a little later. Or
2) I could use a GTi-R timing map (which is much more advanced) since I'm using so many GTi-R parts. I know it has 8.3:1 CR which is why it's probably advanced more, so I was thinking of taking off 3-5* across the map?

Which of these seems like a better idea? I've never had to retune for anything other than the fuel map, so I am a little lost on this one.

I also was looking at this timing map posted here by Vadim, it looks pretty decent as well.

All help is appreciated,
Nate

Hey Nate,

What kind of compression ratio are you actually going to be running with DET pistons?

Also can you post up your current timing map that you plan on running and the GTi-R one?

Also are you burning the chips yourself?

Yeah, I can post up the maps in a few. Let me know if you'd rather have the actual files.

And I imagine that I'll be running 8.5:1 with the DET pistons. Maybe a hair under with the Cometic? They are DET pistons going into a B13 DE. I don't believe I'm going to have my head or block decked at all, but I'll wait for the machine shop to say if it needs that or not.

And yes, I have a Moate's burner so I can burn my own chips!

U13 Timing Map


GTi-R Timing Map

Option 1 sounds way better to me.

Any specific reason why Ben? I'm sure its safer and would have less chance of detonation, just curious if there are other factors you considered before coming to that conclusion. I would like to tune the map a bit to get the most out of the build and stay within a sort of safe window.

Say I go with option 1 and wish to get the most out of it - would using that map, and using the off-boost portion of the map in Vadim's post I linked to be a safe combination? I'd probably start a bit lower and work my way up, rather than jump right to those values in his map of course. I also understand the TP values are different and I would need to compensate for that.

Static compression rules all for timing. The T28 turbo and intake manifold from the GTi-R are factors to consider but they are minor compared to the compression ratio and they are going to cause you to remove even more timing, not the other way around.

You could certainly use the off-boost portion of Vadim's map and that's probably a good idea for fuel economy however you'll want to do your own testing.

Right on, thanks for the help Ben! I knew the GTi-R had the lower CR, and I noticed that it had much more aggressive timing, but I thought if that was safe for the GTi-R, than by retarding the timing a bit it would have the potential to be a pretty safe and powerful tune for a 8.5CR. I will look into mapping over portions of the off-boost area from Vadim's post and start applying it to my original U13 timing map.

When I do get my boost controller down the road, for the top end of the map, if I'm going to go from 7lbs of boost to 12-14lbs, how much should I consider retarding the timing? I see Vadim's post is for 10lbs and the timing in the very last block is 22*. For the boost I'm hoping to run, would something around 19-20* in the last block be safe for 12-14lbs? And then smooth it out down from there? Or should it be a bit lower, say around 16-18*?

One last questions, base timing for 8.5:1CR, if I map over the lower portion of the tune from Vadim, should my base timing be about 20* since that is where it starts on that specific map? Sorry for all of the questions, this will be my first time really playing with a timing map, and I just want to start with fairly solid foundation of knowledge and a tune.

You're right there, but you'd have to remove so much timing you'd basically be where the U13 map is right now (although the GTi-R map does look like Nissan spent more time tuning all areas where on the U13 it's like they don't bother to tune the top middle section). If you want to remove 12 degrees from the entire GTi-R map you might be in good shape. Maybe. You'd have to compare.

On 8.5:1 compression Enthalpy recommends removing 0.75 degrees for each 1 psi and while that sounds great there are so many more variables to take into account. If I were you I would remove at least 1.5 degrees for each 1 psi as you have a much higher flowing system (turbo, intake manifold, head) than what Enthalpy was imagining when he gave that advice.

This is to start with, and be safe. Timing might be able to be added back but you'll want to do that on a dyno and with detonation detection equipment.

19-20 sounds good and is probably where things will end up when you tune them. 16-18 is where you will be safe, and maybe where you should start.

When you change timing in the idle areas of the map and then you go to time the engine with a timing light if you get the ECU in timing mode the ECU (I believe) removes all idle timing control and uses the pue values from the table. If you have 20 degrees in the idle areas of the table then you'll want to make sure the timing light shows 20 degrees. If you have 15 degrees in the timing map in the idle area then you'll want to make sure the timing light shows 15 degrees. Got it?

Got it. Appreciate the help Ben. I think I've got it covered enough now to get started on this. Another thing has me interested now, which is TP values. I just searched for (I think it was Vadim's again) TP Tuning thread, but could not find it. I thought it was stickied?