Mysterious power flatline from 5k rpm - tuner is stumped

[CowsWithGuns]

16 minutes ago, Kinkstaah said:

If one of the results from b) looks really strange, or the VCT switch over point is strange (like 6000+ rpm? or at 1000 rpm?) then that would be where you start looking as to how your cams have been physically set up.

I saw this curve in person on the dyno screen. My VTC on graph was making substantially more power the WHOLE way and touched at 6500. This is now relying on my eternally questionable memory but I saw that, and hence was really keen on my degree wheel plan.

 

16 minutes ago, Kinkstaah said:

a) More timing. Like 5 degrees+++ everywhere more timing. The old adage was "20 degrees at 20psi". You're nowhere near it. This is NOT a licence to just throw 5 degrees in and send it lol.

Tyvm for adding confirmation, and no hahahaha I'm not touching that shit. I still think there's a cam issue, just I'm time poor atm and cannot check imminently (I also need to figure out how the hell I'm going to mount my degree wheel without gutting my radiator and crank pulley if at all possible lol)

Edited February 8 by CowsWithGuns

[Lithium]

18 minutes ago, CowsWithGuns said:

but my VE still seems to fall off HARD, and my VCT disengagement point is very high. Are these things related or separate in your eyes?

Sorry finishing lunch, can't spend much time - though for food for thought, the tanking VE I'm not 100% is thaaat bad.   I threw your 220kpa VE line into excel, then calculated "Unitless flow rate"... basically VE x RPM and divided by a made up number to bring the final values into something that looks meaningful.  Where VE is proportional to torque, this value would be proportional to power.    Obviously mechanical losses etc come into it too, so power will roll over more than this shows but this is not close to showing power flat lining at 5000rpm.

Now, short answer is timing doesn't affect VE - it's basically just saying how much air is moved by each cylinder in each complete engine cycle.   But timing DOES affect how well the air moved (as a result of VE and boost) is used.   You can increase torque without increasing VE if you aren't at optimal timing.

Edited February 8 by Lithium

[Kinkstaah]

6000rpm is weird. Usually the cutover point is half that. 3500. Could it be soft timing? I do not know.

The way forward is gonna be check how those cams are degreed. Then get a second opinion/second tuner. The second opinion/second tuner could also be somebody who has installed RB cams before. They are stock cams, right?

Of course, time poor and money poor does skew things.

[CowsWithGuns]

17 minutes ago, Kinkstaah said:

6000rpm is weird. Usually the cutover point is half that. 3500. Could it be soft timing? I do not know.

The way forward is gonna be check how those cams are degreed. Then get a second opinion/second tuner. The second opinion/second tuner could also be somebody who has installed RB cams before. They are stock cams, right?

Of course, time poor and money poor does skew things.

Yeah, I've been hung up on that.

Ok, latest and greatest action plan is

1. Verify my cam timing, attend to it as required. If I need to take timing belt off for any reason, adjustable gears (and the boost doc VCT adjustment thingo) are going on - only wish I knew their value in the past. And yes, stock cams. I forsee nothing to gain by upgrading to some mild kelfords or poncams, but happy to be told otherwise.

2. Get it on a dyno again with explicit request to optimise ignition advance (not that this is something that should need to be said but anyway...). Things are looking a little grim for the recent tune, but honestly just the constant comms and the tuner chatting to me for a full hour after I arrived really did put them in my good books so I'll *probably* take it back - and he had a folder full of powerful R34 dyno logs I glanced at so I'm erring on 'theres a reason for this' rather than incompetence or otherwise. Regardless, I will contact and ask - and the answer will guide my decision on return, or f**k it and gamble with tuner #4.

I'm time and money poor but thankfully only acutely. I did just spend 3 fulltime weeks and like 10 grand on this build over xmas + tune/diag fees. Will probably not have more to share until I do the above... and I could do with a rest - this whole procedure has taken a toll. Huge thanks to everyone for your support! Maybe there will come a time I will be the one with a happy car and a brain full of experience to share here

Edited February 8 by CowsWithGuns

[Kinkstaah]

I mean with all the above taken into account, there's definitely some wisdom in just driving the fking thing, and a 250KW RB will not be in any danger with its low timing, low boost, and not making peak power at 7500rpm as you slam into the limiter.

Conservative just means you're burning the candle more slowly after all, that has its own happy merits too.

[Lithium]

15 minutes ago, CowsWithGuns said:

I arrived really did put them in my good books so I'll *probably* take it back - and he had a folder full of powerful R34 dyno logs I glanced at so I'm erring on 'theres a reason for this' rather than incompetence or otherwise

I haven't scrutinised the hell out of the tune yet, but my initial impressions are that I don't exactly have red flags about what he's done and said to you.  Sure, there are things I can pick in there buuuuuuuuut nothing alarming so far and again, it seems like it was left safe and ok to drive while things get resolved so you don't burn money.  Integrity and transparency are hard to find in a tuner, dude looks like he has both and left the car behaving a heap better than it was when it arrived.   From the POV of someone who likes to think I'm not stupid and do an ok job, I've 100% taken a car off the dyno and later gone "ahh shxt I should have just done x to confirm y".  We're all human, there are a lot of balls in play, and when something isn't going the way you expect it can throw you and you can't take all the time in the world to cover all bases when someone stressed about money has to pay for you to do it.

It could age that made 100% the right call as well, and I'm a cowboy  But yeah.   I'm not just being diplomatic, if I raise questions suggesting mayyybe a couple of differences with the tuning approach may have left you a lot happier is not saying he's incompetent and I *could* be wrong as well. 

All I was saying is there a chance that even 3-4deg of timing through a lot of the map on the exact mechanical setup you have MAY have got it to a point that you'd have not raised an eyebrow at the result, and I'm not sure why that wasn't tried but not saying there was no good reason.

Edited February 8 by Lithium

[Dose Pipe Sutututu]

3 hours ago, Kinkstaah said:

6000rpm is weird. Usually the cutover point is half that. 3500. Could it be soft timing? I do not know.

Nah mine is at 6700, best switch over when I over laid 2x runs with VCT on and off.

[GTSBoy]

And I reckon stock switch-off is about 4700-4800, depending on Neo/vanilla. I get the impression that if an adjustable exhaust gear is used or bigger cams are installed, that there is usually good reason to increase that to ~5500. Results will vary, consult you doctor, etc etc.

[Lithium]

10 minutes ago, GTSBoy said:

And I reckon stock switch-off is about 4700-4800, depending on Neo/vanilla. I get the impression that if an adjustable exhaust gear is used or bigger cams are installed, that there is usually good reason to increase that to ~5500. Results will vary, consult you doctor, etc etc.

Yeah.  In my general experience the more the engine is allowed to breathe the higher you can set it and  hold torque.  Upgraded intake manifold, aftermarket exhaust manifold/turbo that drops EMAP etc seem to let it carry.   I've definitely had results which back up what @Dose Pipe Sutututu has found... late 6000rpm has been perfectly rational on some RB25 setups I've done.

This particular car though, if I were tuning it from scratch I'd have "started" my VCT change over hunt in the mid 5000rpm range based off previous experience.

[jdniss]

Is there supposed to be a "hole" in the E-Throttle target table from 6000~7000rpm below 100% TP?

Theoretically you wouldn't hit it under 100% WOT, but seems odd

[Butters]

2 minutes ago, jdniss said:

Is there supposed to be a "hole" in the E-Throttle target table from 6000~7000rpm below 100% TP?

Theoretically you wouldn't hit it under 100% WOT, but seems odd

That seems hell weird !  But I've never played with drive by wire.  Love to know a reason ?

[Lithium]

10 minutes ago, jdniss said:

Is there supposed to be a "hole" in the E-Throttle target table from 6000~7000rpm below 100% TP?

Theoretically you wouldn't hit it under 100% WOT, but seems odd

Nice spotting.  Damn I wish I had more time to look over this tune now, that looks like a fk up.   It's not unusualy for people to not be "not at WOT", or even for the APS to not be at a full 100%.   With this throttle map if the driving was at like 95% (I've seen that plenty of times) then this would command 50% *actual* throttle.   Not necessarily a thing that would have shown itself on the dyno (tuner was 99.8% APS so probably about 98% TPS which should be good enough) but very strange and would definitely affect things in the real world if it's not part of some other strategy.

 

[jdniss]

30 minutes ago, Butters said:

That seems hell weird !  But I've never played with drive by wire.  Love to know a reason ?

Andre from HPA suggested in a webinar targeting a slightly lower than 100% TP target as not to smash the E-Throttle blade into the stop and run the risk of snapping it ~ something like a 98-99% target instead;

Though the max e-throttle clamp in this tune is 99% DC - so maybe that achieves the same thing?
-Same here, I don't have an E-Throttle to compare against, just guessing 😄
 

21 minutes ago, Lithium said:

Nice spotting.  Damn I wish I had more time to look over this tune now, that looks like a fk up.   It's not unusualy for people to not be "not at WOT", or even for the APS to not be at a full 100%.   With this throttle map if the driving was at like 95% (I've seen that plenty of times) then this would command 50% *actual* throttle.   Not necessarily a thing that would have shown itself on the dyno (tuner was 99.8% APS so probably about 98% TPS which should be good enough) but very strange and would definitely affect things in the real world if it's not part of some other strategy.

 

Yeah it'd be really nice to see a full WOT log past 6000rpm with a heap more parameters enabled,
or the laptop plugged in doing all the logging @CowsWithGuns.

Might rule out whether VTC switch on/off point or E-Throttle target or RPM/MAP limiter is playing a factor in the low power.
 

Edited February 9 by jdniss

[robbo_rb180]

29 minutes ago, jdniss said:

Is there supposed to be a "hole" in the E-Throttle target table from 6000~7000rpm below 100% TP?

Theoretically you wouldn't hit it under 100% WOT, but seems odd

May be part of the problem. I bet someone fat fingered a short cut button.
Fill in the spots by copying across. Re calibrate Ap and DBW.
Your APS calibration is off as well so see how it goes after all that


We did find keeping the DBW throttle body not fully open increased torque in parts of the map on my rb25.

[Murray_Calavera]

2 hours ago, robbo_rb180 said:

We did find keeping the DBW throttle body not fully open increased torque in parts of the map on my rb25.

I'd be keen to get more details around that.

[CowsWithGuns]

Hahahahah, well spotted gang. Here's the story there:

I put in e-throttle and tuned it to driveable state so I could drive to the tuners. That's my work there (noob me didn't fill right but interpolated vertically, and didn't realise theres more to the table).

Tuner never noticed it, never ran into issues. On the drive home I experienced what felt like a boost cut protection at 6000 rpm and found that after slewthing the next day. I decided not to bring it up here as on the dyno TPS was still 99% so it wouldn't be relevant - and I didn't want to highlight my ineptitude on the laptop

I ended up emailing the tuner just to verify there wasn't some strategy there but realised that this was definitely my work lmao.

[CowsWithGuns]

6 hours ago, jdniss said:

Yeah it'd be really nice to see a full WOT log past 6000rpm with a heap more parameters enabled,
or the laptop plugged in doing all the logging @CowsWithGuns.

Here is a WOT run in 2nd gear after I fixed the throttle target table. Unfortunately I don't have anywhere nearby where I can full send in 3rd or 4th.

6 hours ago, robbo_rb180 said:

Your APS calibration is off as well so see how it goes after all that

What indicates this to you? I haven't done it yet but can do - just curious what gives that away to you?

I also turned on closed loop just for stage 1 clamp. I feel like my spool improved a decent bit afterwards, but that could just be placebo.

 

6 hours ago, robbo_rb180 said:

We did find keeping the DBW throttle body not fully open increased torque in parts of the map on my rb25.

Interesting you say this. I noticed on my previous build (stock throttle) that in first gear the car definitely felt more powerful at something like 80-90% throttle rather than all the way, but only some of the time. I thought I was going crazy.

 

PC Datalog - 2024-02-8 2;32;37 pm.llgx

Edited February 9 by CowsWithGuns

[CowsWithGuns]

On 2/8/2024 at 10:56 AM, Kinkstaah said:

a) More timing. Like 5 degrees+++ everywhere more timing. The old adage was "20 degrees at 20psi". You're nowhere near it. This is NOT a licence to just throw 5 degrees in and send it lol.

On 2/8/2024 at 12:00 PM, Lithium said:

All I was saying is there a chance that even 3-4deg of timing

The tuner on whether I am knock limited and the possibility of more timing advance:

"Regarding the ignition tables, the values we have in there are on par with the other 25neos we have tuned and are confident in where they are set. I’m not sure what values you’re comparing as the table axis was originally set to MAP but have now been changed to display that axis as MGP. That can make it a bit confusing to compare to different tunes if they have their tables set up differently. But as far as the it being knock limited, yes that is the case in the low end/mid range as it comes onto boost but that is typical on this sort of setup and yours didnt seem any worse than usual. "

I don't know what to make of all this. Ye wise SAU veterans say the advance is less than normal - my tuner says it's normal. I went on a hunt to find tuned, well performing neo files online to see for myself but only found one (admittedly with ~2 deg more advance on the top end) but that's a sample size of 1 lol. No doubt they are out there so I just need to search harder. Does anyone have a comparable R34 tune file that performs mint for me to look at?

I also received this as my final result.

[CowsWithGuns]

Made a degree wheel and took some measurements. I could not find details on stock camshaft duration and position at 1mm, so I am using the smallest tomei 'drop in' camshaft as a sensible reference for duration.

 

My dial gauge was really really touchy and would move around 0.2mm give or take, due to the scuffed clearance to the lifter (sometimes rubbing on the camshaft)to take to access the valve, so give a generous tolerance to my measurements.

I don't understand camshafts enough to have confident conclusions, but my observations and thoughts are:

• Intake cam seem dead on perfect, HOWEVER, my lift measured is 8.5mm (caliper), ~8.6mm (dial gauge) and the factory spec is 8.4 according to Tomei. Strange but does not worry me too much.
• Exhaust cam seems totally rooted! Cam lift spec is 8.7mm and I measure 7.2mm with calipers and 7.0 with dial gauge. Accordingly, my duration is 20 degrees lesser than my intake cam! The lobe centre is also advanced by 5 degrees (+/- say... 3 degrees), but the significance of that is lost on me pending further study. Edit: measured two other random lobes, both ~7.0 to 7.2 on calipers. The nicest, shiniest unworn looking lobe was 7.0 ??

Is it reasonable or at all normal for a camshaft wear out that much? The engine ran on very loose clearances (up to 23 thou) on the exhaust side for some time, I reshimmed in Oct down to 18/19 thou and the valve train noise settled a lot. Would this wear be a symptom of those loose clearances or the cause - or is it both in a vicious cycle? In case the clearances tell a story, here's my notes from Oct:

Here's two pictures of lobe 1. To me it looks fine?

My amateur eye is looking at lobe 3 and thinking that looks crap, but I would have not thought much beyond that (until now).

 

So I assume the path forward is to get a spare factory exhaust cam or a pair of mild kelfords, and then adjustable cam gears on both sides and reshim them tight. Zip it up, back to the tuners, and miraculously find another 60+ horsepower and achieve The Goal. But what could have caused this problem to begin with?

 

Edited February 10 by CowsWithGuns

[Dose Pipe Sutututu]

How are your valve clearances?