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Discussion Starter · #1 ·
so ive had my wrx for a couple weeks now, put nearly 600 miles on it so far. its been great but now that i have some first hand experience with the car i have some new questions.

first of witch is the issue of low engine speed pre-ignition. dont lug the engine, dont ask the engine to do a lot of work while at a gearing disadvantage etc etc... but where exactly are the lines here? say in 6th gear, at what rpm level is it safe to ask the engine for peak power? would 2500 be high enough, that is peak torque after all... but it just dosent feel right, i feel like it needs to be higher, but how high?

is the boost gauge a good tool to decide where to draw lines? say im in 5th gear at 40mph, the car is below 2000rpm. using my intuition the car seems fine to cruise on flat terrain in this state. is it ever ok to make any sort of boost in this scenario, even 1-2lbs? is the engine ever in danger while pulling a vacuum?
 

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Stanley Yahtzee said:
say in 6th gear, at what rpm level is it safe to ask the engine for peak power?
When you don't have the RPMs to be WOT in 5th gear. Basically, only if you're on a high speed track...

Stanley Yahtzee said:
is the boost gauge a good tool to decide where to draw lines? say im in 5th gear at 40mph, the car is below 2000rpm. using my intuition the car seems fine to cruise on flat terrain in this state. is it ever ok to make any sort of boost in this scenario, even 1-2lbs? is the engine ever in danger while pulling a vacuum?
The car seeing boost in high gears isn't necessarily a problem. You just need to figure out how quickly you need to accelerate, and use that to determine what gear you should be in.

For example, if you need to pass someone on a 2-lane road where you have a long passing window, rolling into the throttle a bit to pass in 5th gear and building some boost is fine. If you have a tighter window and need to make a quicker pass, you'd be better off downshifting. Personally, I always downshift, because I want to be done with my pass as quick as possible (within reason, not necessarily WOT / EWG wailing), and therefore, require a lower gear.
 

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I try not to get heavy in the skinny pedal under 2500. If I'm in a flat out situation I try to be above 3k before tromping it.

Sent from my SM-G955U using Tapatalk
 

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XJman said:
I try not to get heavy in the skinny pedal under 2500. If I'm in a flat out situation I try to be above 3k before tromping it.
This is generally a pretty good rule of thumb. I do my tuning datalogs from 2K-redline to get as broad of a window as possible, but that's about it; I don't floor the accelerator in the 2#00 RPMs during normal operation of the vehicle.
 

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Discussion Starter · #6 ·
U r overthinking this.
yes i am, im fairly confident that common sense is enough to answer these questions but one can never be too sure...

The car seeing boost in high gears isn't necessarily a problem. You just need to figure out how quickly you need to accelerate, and use that to determine what gear you should be in.
i am glad to see this being agreed with as it does feel harmless but ive read many people claim to never make boost in high gears and low rpm. i think the problem is their lead feet and not the car.
 

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Stanley Yahtzee said:
yes i am, im fairly confident that common sense is enough to answer these questions
Yes.

Stanley Yahtzee said:
i am glad to see this being agreed with as it does feel harmless but ive read many people claim to never make boost in high gears and low rpm. i think the problem is their lead feet and not the car.
The big problem is putting the vehicle into untuned load sites when you WOT in higher gears.

If your vehicle has per-gear boost compensations built into the ECU (I haven't tuned a 2015+ WRX), that helps, but it's still not a license to be an idiot.

On a basic level:
As you approach peak torque (and higher engine load), ignition timing is decreasing. If you are overboosting due to improper throttle in higher gears, you may put yourself into load sites that have not been calibrated. When you get beyond the load columns on the ignition table, the advance remains the same. So while you should be reducing timing as load increases, it doesn't, and can cause detonation.
 

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Discussion Starter · #8 ·
If your vehicle has per-gear boost compensations built into the ECU (I haven't tuned a 2015+ WRX), that helps, but it's still not a license to be an idiot.
i dont think it does, i get the feeling that a lot of these FA20 engine failures are 100% user error. it feels like it wouldn't be all that hard to mess these engines up if you get lazy or just dont know what your doing. its part of why i started this thread. yea its overthinking, probably, but this car wasn't cheap, and im very unsure of my actual manual driving skills and knowledge. my old civic was very easy to drive and understand compared to this.
 

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EJ257 said:
On a basic level:
As you approach peak torque (and higher engine load), ignition timing is decreasing. If you are overboosting due to improper throttle in higher gears, you may put yourself into load sites that have not been calibrated. When you get beyond the load columns on the ignition table, the advance remains the same. So while you should be reducing timing as load increases, it doesn't, and can cause detonation.
To further elaborate on this (so hopefully you'll understand what I'm referring to), I'll quote a post I made about a ClubWRX car I tuned a few years back:
EJ257 said:
Calvinball...

Will approached me suffering from a boost oscillation. After a revision or two to cleanup that map, the issue was resolved, but I told him I would feel more comfortable if I just redid his map from scratch. He agreed, and we started the tuning process.

I set boost target to 17 PSI:


You'll notice a slight "spike" in the boost graph, in which the car was overshooting target by .25 PSI. Datalogs in both 3rd/4th gear show that it isn't really an issue, and the "overboost" doesn't go much higher in 4th than 3rd (<.5 PSI in 4th). For reference, Cobb has a 1 PSI variance in their map notes.

Ignition timing is set to 13°-21°:


Other than boost and ignition timing, the other three major table sets that were modified were AVCS, Open Loop Fueling, and Drive-By-Wire.

OL Fueling target was set to 10.8. With WBO2 data, I'll typically target 11-11.2 AFRs, but without having that information, I target a bit richer.

With AVCS, there isn't as much reversion during cruise, and the midrange is a bit more aggressive.

Lastly, the DBW settings. My DBW mapping is a bit more aggressive on the ramp rate, and a bit more linear.

From one of the last logs I received from Will:


Didn't touch smoothing, driver weight 175.
As you can see, as it approaches peak torque, ignition advance decreases, "bottoms out", then starts rising again.
 

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Glad I know that now. I didn't realize the tables worked that way

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XJman said:
Glad I know that now. I didn't realize the tables worked that way
There are ways around that. For example:


I use the advance table to pull timing in the event I overshoot my redline or engine load targets. I lose a very small amount of resolution by doing so, but I feel the "safety net" I build in is worth it. The second-to-last column is slightly above the max engine load I expect to see. I use the final column to pull advance in the event of an overboost / over-load. RPM is similar, in that if I happen to over-rev, I'm pulling timing there as well.

NOTE: I blurred out most of the table, including the column headers, but I left the parts that I'm addressing above; it should hopefully be enough for you to understand. I don't want anyone to blindly copy/paste my table thinking they're making their vehicle safe.
 
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