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...but you are controlling the turbo with your EBC...not the engine. And what is happening to the turbo is only relevant pre throttle, when throttle is closed or partially closed . Pre is better if you have a fast spooling turbo, ... It's all about throttle control ...try it someday and see if it improves your throttle modulation.
Originally Posted by Brettus
...Where you would notice it most is halfway around a corner (especially an uphill corner) ............ when trying to modulate between full and partial throttle.
I've actually talked to Greddy turbo guys that have gone off the road in this situation because of the violent on/off nature of the throttle. ...
Captured this anomaly today that I believe is a similar scenario as described above....as a result of the EBC signal line currently being plumbed post instead of pre-TB.
- The first profile is a spirited 3rd, 4th & partial 5th gear clean pull onto the hwy today. Solid boost control...13 +/- 0.2 psi, each gear.
- The second profile was 5-10 mins later...where I went WOT, ...then partial throttle ~0.2 second (can't recall why), then back WOT again. BOOST SPIKE FROM ~ 8 TO ~15 psi.
Yeah, an 8 - 15 psi spike exiting a turn might cause some issues.
Edit: I recall why I went WOT, partial, and WOT again. I accelerated up the hwy entrance ramp with two cars ahead of me. When we were on the hwy I planned to bounce to the fast lane, go WOT, and pass. So, I bounced to the fast lane, went WOT when at that moment the first of the two cars ahead of me started coming into the fast lane as well. So, I slowed. The driver realized that I was in the fast lane accelerating and receded back into the slow lane. Then I went WOT again. That was the scenario that resulted in the boost spike shown in the second profile below.
Could be that ...or could be an EBC issue . The issue I talked about is more prevalent at partial throttle.
If EBC related I'd expect intermittent irregular behavior. But I'm not seeing that. I'm seeing solid boost control..., except in this case, i.e. throttle on...into boost, off / partial throttle, back on full.
Captured this anomaly ..where I went WOT, ...partial throttle ~2/10 a second (can't recall why), then back on throttle again. BOOST SPIKE FROM ~ 8 TO ~15 psi...
...and the v-dyno. 350 HP, 296 lbft. Torque spike from ~240 to 296 ...lack of control NOT cool. Have to get that EBC control line moved...
Reviewing a number of my v-dynos I identified a fairly repeatable HP rate / slope increase at ~7k rpm (see post 705). Seemed an odd thing...given back pressure is increasing at that time...working to inhibit HP production. So considering potential contributors...turned to what seemed the likely suspect: the Renesis SDAIS (Sequential Dynamic Intake System): the dynamically actuated intake valves designed to optimize torque and HP across the the rpm range.
Considering valve timing, and that my VDI is disabled; the APV was the clear suspect. But my APV opens at ~6k rpm, and I'm not seeing the effect until ~7k rpm. After some discussion w/ Brett came to understand that the APV actuates very s-l-o-w-l-y. Aaah, ok...and that...combined w/ the time the system takes to resolve the inevitable turbulence that will result ... all could explain the ~1k rpm delay between actuation and measured response.
So, how do I optimize APV tuning for my system? By what metric should APV timing be based? Seems logical to base timing on the same metric as the point of the SDAIS system: air velocity and flow. If true, then the APV timing designed to optimize intake air flow and velocity for a NA wouldn't likely be optimal for my system. The APV is tuned to open on a NA at 6k rpm where it is generating ~170g/s. My system generates 170 g/s at ~3.5k rpm, and ~ 300 g/s at 6k WOT. Great...so optimal APV timing is somewhere between 3600 and 6000 rpm.
Couple points I gleaned:
This discussion took place ~ a decade ago when the Greddy was the common turbo generating up to ~ 47 lbs/ min @ 65% efficiency. The relatively smaller output of the Greddy wasn't suited to take advantage of the expanded intake volume (APVs open) of the Renesis, which is why at some point the Greddy kit began shipping w/ an APV block-off plate...essentially limiting intake volume expansion by converting the 6-port into a 4-port. Testing done indicated that though blocking the APVs resulted in reducing g/s per psi., i.e.
- APVs closed: 31 g/s per psi
- APVs open: 41 g/s per psi
...it did have the advantage of increasing air velocity..., and forcing the turbo into a higher efficiency zone..., reducing heat, and allowing boost pressure to be sustained higher into the rpm range.
However, fast forward a decade...my 6266 turbo, ~60 lbs/ min @ 70% efficiency, generates more than enough output to capitalize on the expanded intake volume w/ APVs open, and hold boost (as much as I intend to run ;-) to my 7500 rpm redline. My recent boost profiles confirm my system capable of holding 13.5 +/- 0.2 psi to redline w/ APVs open. So, where the Greddy turbo was the limiting factor of the system in the Rene - Greddy system..., the Rene appears to be the limiting factor in the Rene - 6266 system. And Brett's work in "The 450whp Renesis Engine..." appears to support that the Rene does indeed have a flow capacity limit to be respected.
OD did a few slow 50% throttle pulls up to 6.5k rpm w/ his APVs fixed open (truly worst case scenario) ...and saw pre UIM IAT spike 200+F ! This confirmed something else Brett mentioned: below a *certain rpm* w/ the APVs fixed open... there w/b a reversion of combustion chamber gases back into the intake during the compression cycle. That'll set the lower APV opening rpm.
So, the challenge w/b to converge on the APV timing "sweet spot":
- lowest prudent rpm to optimize increased flow for top end HP performance for my system.
- yet above the minimum rpm where reversion occurs.
I came to the same conclusion as I later found Kane did in 2010: Target an "open timing just before the closed APVs become a restriction to flow."
Test w/b by doing a series of pulls starting at OEM timing..., then incrementally reducing timing by 100 RPM...from say 6k to 5.5k to identify optimal timing. The following should give indication to optimal timing:
- g/sec
- IATs
- boost profiles (mid & highs)
- v-dynos (mid & highs)
Don't know how much, if anything, there is to gain here. We'll see.
You make a good point regarding fixed opening rate...relative to the varying acceleration rates of the engine in differing gears. My above post was already long and complex enough...that I chose to omit this nuance, as well as the associated lean spike associated w/the opening of the APVs.
There is certainly no "right" or "wrong" here...just a matter of preference. However, I'm satisfied w/my system performance...just after potential low hanging fruit which may have some high end gains.
I have done a fair bit of testing to find the optimal point to open the APVs . I think I set yours to the same as what I'd set a Greddy to ...so with the more rapid engine acceleration you now have .... there def will be a small benefit from opening a little earlier.
To test I would do a log with apv closed and then another with it opening way too early . Overlay the g/s logs and the ideal opening point is pretty evident.
I have done a fair bit of testing to find the optimal point to open the APVs . I think I set yours to the same as what I'd set a Greddy to ...so with the more rapid engine acceleration you now have .... there def will be a small benefit from opening a little earlier.
To test I would do a log with apv closed and then another with it opening way too early . Overlay the g/s logs and the ideal opening point is pretty evident.
I do see value in doing a log w/ the APVs closed, but w/b concerned about the "opening way too early" log d/t the combustion charge reversion. That's why I planned to start from the OEM setting, and incrementally back down to optimal timing by watching... among other things... IAT to guard against allowing reversion.
I get that..., but prefer to approach it in this way...
Currently traveling and Team's comment got me thinking about calculating an estimate for reduced turbo APV timing.
Originally Posted by TeamRX8
Well the deal is they open at a fixed rate. ..."
Of course, I'll still do the testing..., but from this estimated "ballpark". Clearly, I've made a few assumptions...so it'll be interesting to see how it pans out.
My estimate is based on the following data and assumptions:
NA 8:
- 0 - 60s time: 6.1 s
- Assumed rpm range: 1k - 8k
My turbo 8:
- 0 - 60s time = ~4.2 s:
- Assumed rpm range: 1k - 8k
Then estimated acceleration (rpm/s) for each is:
- NA = 7000/ 6.1 = 1148 rpm/s
- Turbo 8 = 7000/ 4.2 = 1667 rpm/s
Note: This calculation presumes linear acceleration. The turbo acceleration is most certainly greater in the rpm range in question d/t the non-linear "increasing acceleration" associated w/ onset of turbo boost.
APV actuation time on my current setup ...start to finish appears to take ~1000 rpm.
Therefore, APV actuation duration in time = 1000 rpm (FI) / 1667 rpm/s = 0.6 s
Presuming APV actuation duration is constant, i.e. the same NA or FI. Then, on an NA 8... w/APV actuation beginning at 6k rpm, it should complete ~:
6000 rpm +(0.6s x 1148 rpm/s) = 6689 rpm
Presuming my assumptions and estimates are fairly accurate and that Mazda tuned APV opening to that rpm as the "sweet spot" between generating top end HP and avoiding reversion; then tuning to the same rpm should get me close. And I can fine tune from there.
My estimate above is that it takes ~ 1k rpm for the APV to open...start to finish, which applied here means that ideal APV tuning for my turbo 8 w/b ~:
Open rpm = 6689 rpm - 1000 rpm
Open rpm = 5689 rpm
Finally, I think Mazda would h/b conservative with their timing... and I m/b able to be a bit more aggressive. So, I think I'll find the sweet spot somewhere ~5500 - 5600 rpm.
Additionally, M/E has two APV Open rpm fields currently set 200 rpm apart: 6000, & 5800 rpm IIRC. The working assumption is that they likely correlate to gears 1-3, & 4-6, respectively. I'll keep the same split.
Just a bit of a diversion...while traveling at the moment. We'll see when I return.
Interesting way to approach it ..... make sure you don't end up losing power in 3rd and 4th etc !
True. I'm primarily concerned with and will likely focus on 3rd & 4th gears, where I'm most likely to be at WOT; while attempting to ensure I don't loose...elsewhere.
Two issues are a bit perplexing...that I agree... don't make sense............yet.
1. the torque decline from ~5k to 6.2k, and
2. the accelerated HP increase above ~6.5k.
#1 The HP slope / torque decline between 5k and 6.2k doesn't make sense....unless it's not a "decline" per se at all, but rather the system returning to equilibrium after overshooting between 4.5k to 5k. That's easy enough to explore: I'll experiment w/ reduced "SET GAIN" relative to SET.
#2. The accelerated HP increase above ~6.5k. The SSV opens at 3750 and the APV at 6050, both of which I'd expect to maintain or accelerate HP ...given the expanding intake flow w/ a turbo capable of keeping up, which I believe my 6266 is. There c/b some vd anomaly..., but I'm doubtful b/c this phenomenon is too repeatable. I'm beginning to think that the wildcard here m/b my EBC control line currently being plumbed post TB... when my WG solenoid reference line is plumbed pre-TB. We saw earlier how a partial throttle condition, i.e. lower boost post vs pre TB, caused a boost spike. Capturing that on my boost profile m/h been providential. I'm wondering if a similar response is occurring when the SSV and APV open. It's reasonable to expect that there w/b a boost drop post TB when each opens (lesser in magnitude than the partial TB condition), ...then the system c/b similarly compensating w/ a boost spike (lesser in magnitude than the partial TB spike). If this were occurring w/ the SSV...it w/b masked by already expecting high HP acceleration at that rpm range.
If true, this would explain the high end HP rise, and ...when the SSV opens would also be contributing to condition #1 discussed above.
Plausible.........theory (we saw how the last one turned out, ). I'll need to get that EBC control plumbed pre-TB to know.
I'll need to get that EBC control plumbed pre-TB to know.
Super easy if your Jet Air line is connected to the bottom of the charge pipe that's connected to the TB (pipe C8 in the greddy instructions i believe?). Just tee into that line real close to the charge pipe nipple, it's how I had my EBC set up for years.
Super easy if your Jet Air line is connected to the bottom of the charge pipe that's connected to the TB (pipe C8 in the greddy instructions i believe?). Just tee into that line real close to the charge pipe nipple, it's how I had my EBC set up for years.
Thanks, Jesse, but my Jet Air is plumbed pre-compressor via a check valve. I plan to tee into my WG solenoid reference line, which is in my last charge section ...just prior to the TB.
I would have already done it, but am planning to establish my AFR failsafe ...and RPM boost cuts at the same time, which w/b a bit more involved, e.g. pulling another vac hose thru the firewall, opening the dash panels, and add'l wiring in my mini-fuse box. And of course, I want her down as short a time as possible; so waiting till I have time to start and complete the work.
Reduced "SET GAIN" relative to SET..., and put a few turns on my compressor outlet elbow coupler clamps (both ends).
Did this first pull today, which mirrors quite nicely a pull from Wed. ...
413 HP / 288 lbft (2/28/20)
411 HP / 286 lbft (2/26/20) (shown in v-dyno comparison)
Whats your injector duty cycle look like? I can't imagine that you aren't nearing 100% Amirite? Either way good job squeezing out the power.
Stroker - Thanks! Good question. I know my ST & LT trims are solid at zero, and fuel pulse width peaked at 16.2 ms on the above pull. But I'll have to investigate in M/E... or get w/ Brett to determine my injector duty cycle.
Also TBH my intention wasn't to increase boost...actually to reduce it ...while generating as wide a torque band as possible. I targeted eliminating recurring leaks. First, eliminating the leak at the last charge section into the TB... ultimately by modifying the charge section. Then recently eliminating a leak at the compressor outlet. I'd tightened the elbow clamps previously... eliminating the leak...only to have it return. So, I finally dbl-nutted the clamp T-bolts, i.e. ran two nuts down onto them, which eliminated the leak and is holding.........so far.
Afterwards I reduced my EBC boost settings, but the impact of eliminating the leak(s) exceeded reducing my EBC boost settings. My boost profile on the 413 HP pull showed airtight boost throughout the pull imparting a huge impact on performance across..., but especially in the high rpm range.
Once the system is stable, i.e. no boost leaks, EBC dialed in, etc.; max boost I'll run is ~ 375 HP / 275 lbft.
But hearkening back to Brett's 450 Renesis theory... namely that the MAF curve (g/s) reaching a plateau in upper rpms is an indication of the engine nearing its max. flow capacity. It's good to see that the MAF curve g/s of my latest pull continued increasing right up till going off throttle, i.e. no duplicate or diminishing g/s on the top end.
.
02-09-2020, 05:52 PM
Have to get that EBC control line moved...
Still getting the characteristic HP rise on the high end w/ APV open set at 6050.
My boost profile on the 413 HP pull showed airtight boost throughout the pull imparting a huge impact on performance across..., but especially in the high rpm range. 
