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Old 03-11-2008, 10:30 AM   #1
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Default EBC tuning for T25

I have the SR20det T25, journal bearing .80/.64.

Now that my EBC is operating perfectly, I really want to tune it good.
So far, I have pretty much left the RPM values alone and simply messed with the values of each cel:

900: 100
3400: 100
5000: 55
5500: 55
6000: 55
7000: 55

My problem with the above settings is that I'm getting a huge overshoot around 3700-3800rpm... bouncing off the overboost protection at 16psi... and then dropping down to near 11psi by redline. The problem is that changing any of the values by 1pt, ie making the 3400rpm value 54 vice 55, I only get an overshoot to 12psi and then a drop to 11psi. If I bump the 5500rpm to 56 to try and hold the boost, it hits the overboost hard.

I'm feeling kinds stuck as the control is super sensitive at 55... one point higher or lower makes a big difference, and I only have so many RPM values to enter.

I'd like some suggestions on changing the RPM values to help smooth out the boost curve. It want to hit my goal of 14psi by around 3500rpm and then hold strong to redline... no overshoot.

I really want this thing done before the dyno day so I can make maximum use of the loaded dyno. If I can't get it working, I may have to do some of my pulls with my MBC so it will hold steady.
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Old 03-11-2008, 10:35 AM   #2
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sam,

if you look at the 3d map of those tables you'll see why you get overshoot. (your only slowly opening the valve between 3400rpm and 5000rpm)

what i'd do it try this table:

900: 100
3000: 100
3200: 55
5500: 55
6000: 55
7000: 55
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Old 03-11-2008, 02:18 PM   #3
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Maybe I don't understand what the values mean.
The number attached to the RPM, ie:55, means that up TO that RPM, the valve will be closed to only 55% of the air it would see if there was no boost controller at all? So as soon as I reach 3001rpm, I'm using the value in the next range, right?

Why do I need so many values... wouldn't I just need:
3000:100
7000:55

Does that mean I'm going to dump boost at 7000? That might not be a bad idea anywasy.

I know based on the spool characteristics that I hit about 14psi in the 3500rpm range... so it would make sense to go with 100% until right at 3500rpm, then stabilize it over the next thousand, and then solid to redline:

So:
3500:100
3800:55
4000:56
4200:57
4400:58
7000:59

I've read through the EBC threads... it would be a helluva lot easier if you could just dial in the boost setting you want and let the computer manipulate the solenoid to give it to you.
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Old 03-11-2008, 02:22 PM   #4
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you could mess with the closed loop boost control....

what i try to do is find where i spool. so you make 14psi at 3500. so i might hold the solenoid to 100% (fully closed) till about 3200rpm.

then give it a target of 55% (half open, 14psi) at 3500RPM. this gives you 300rpm in which the valve is fully shut to being modulated...

that shoudl get rid of your overshoot, the rest you can find spots if the boost drops a bit, for example say you slowly lose boost from 4500rpm to 5900rpm, maybe a point at 5200rpm of 59% might stabilize it.

whatever the last number on the scale is, the MS will keep that value....
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Old 03-11-2008, 02:53 PM   #5
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But its a curve right, its not how Samnavy said it holds the last value it crossed.
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Old 03-11-2008, 04:10 PM   #6
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Quote:
Originally Posted by samnavy View Post
So as soon as I reach 3001rpm, I'm using the value in the next range, right?


nope...it will take a linear drop to the next RPM point. that's why i try to make a 200-300rpm window.



here was my old map in 3d...should help you see it.



now look at what your's is doing....
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Old 03-11-2008, 04:56 PM   #7
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Brain, thanks so much for that explanation... now I know what you meant by (you're only slowly opening the valve between 3400rpm and 5000rpm)... it makes perfect sense why I had overshoot... at 3500 I was still at like 96%, [email protected]% [email protected]%, [email protected]% etc... down to 55%@5000.

Now that I know how exactly it works, it should be easy to get what I want.
I need to figure out exactly what RPM I hit 14psi at... and 200rpm before that, dial in a slightly lower % to get the ramp starting down... and then input a good value about 200rpm after that steady it out... so, if I expect to hit [email protected]:

900: 100
3300:100
3700:55
6600:56
6800:55
7000:54

I think for the sake of this engine, I might sacrifice a psi or two at the very upper RPM's. It really is very sensitive around 55%... one point either way makes a big difference in psi. I try and shift at aroun 6500anyways, so just in case I keep my foot in it a little long, I'm trying to help the engine last.
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Old 03-11-2008, 05:08 PM   #8
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i like to tune a little bit of a boost increase at redline, keeps the torque up, feels awesome.
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Old 03-12-2008, 09:55 PM   #9
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OK, now that I know what I'm doing, things are coming together.
Some issues still include my boost gauge not reading accurately (go figure). I've got the overboost protection set to 15psi... and I'm hitting it with the boost gauge only reading about 13psi. I thought it only read about 1psi low, but towards the extreme upper end, it looks like it's farther off than I thought, because I've gotta assume that the MAP sensor in the MS is more accurate than my $40 gauge.

So, I've been using the 15psi overboost as my target. I'm trying to give myself the quickest spool and steadiest gauge (12.5psi gauge=14.5psi actual) without hitting the overboost... I'll call that 14.5psi and it'll be close enough.

These number are solid in 3rd/4th... but I'm still touching the overboost of [email protected] in 5th. It's not running into the cut like a damn brick wall as before, but it's kinda lightly tapping it... stumbling. Then I'm losing a about 1-1.25psi to redline. Tomorrow I make changes in red and that should do it!

Current settings:
900: 100
3200: 100 3150:100
3600: 54 3550:54
3800: 55
6500: 56 6500:57
7000: 54
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Old 03-12-2008, 10:06 PM   #10
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Quick off-topic, but Scott/Sam, do you guys have issues when using WOT at around 2500rpm in 4th or 5th with serious boost overshoot? My overboost seems to not work (it's been set at 152kpa since day one, my boost is like 190+) so I have seen 20psi+ at like 3000rpm. My map is something like:

0rpm: 100
3600rpm:100
3800: 70
4500: 78
7000: 78

The reasoning is obvious (100% DC at 3000rpm = no wastegate) but do you guys find it to be a problem?
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Old 03-12-2008, 11:50 PM   #11
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If you are attaining maximum spool there then I guess, that could cause the overshoot.
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Old 03-12-2008, 11:59 PM   #12
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Once I learned how the thing worked, I set a 4000rpm value of 100 and made repeated pulls in 3rd/4th/5th observing when exactly I would hit 14psi. I've narrowed it down to about 3350-3400rpm. So, I start ramping down 200rpm before that so I don't get any overshoot. The trick is to get it to stabilize 14psi exactly at 3400rpm and hold it perfectly to redline. The problem I'm running into is that the car seems to load a lot more in 5th so I'm hitting the overshoot, but in 3rd I'm only getting like 12.5-13psi. If I tune it just perfectly and then take one of my 200lb buddies for a drive, it's gonna load the engine more and I'll hit the overboost.

Sav, @WOT, I'm only making about 6-7psi at 2500rpm. My overshoot was happening at around 3500rpm, but I've pretty well fixed it. The overboost protection works perfectly for me wherever I set it.
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