legacycentral bbs

Posted: **Mon May 30, 2005 4:33 pm**

Firstly, I'd like to apologize if any of the information contained herein has been previously discovered. If I missed the post, then that is my fault. I'm not seeking credit for this, but I want to shed some light on problems when turning up the boost and modding, and to open some eyes as far as tuning solutions for our vehicles.

These logs were taken from my '91 Legacy Turbo Sport Sedan, Saab TMIC, 3" turboback and Blitz SBC-iD boost controller. They were taken with the Zeitronix ZT-2 Wideband O2 and the GReddy eManage.

They are mostly self explanatory, but I'll give my comments for each one.

This log was taken from a 4th gear pull on the highway. I officially pronounce the MAF sensor dead at 4700 rpm. It flatlined at 5.0V THIS early. I remember reading Phil (BAC5.2) saying that the MAF will max out at about 11-12 psi on a 16G. Well, this is about 11.5-12 psi on my stock turbo. As you can see, the Normal Injector Duty Cycle is 80%. This is the last value on the ECU's table of MAF values and therefore after the MAF maxes out, the injectors are "snapped open" at 80%. My adjusted duty cycle at this RPM is 85%, which tapers up to 90% towards redline.

My laptop crashed before I could save the stock tuning logs, but you get the idea.

This is the log from the Zeitronix. User 1 is the MAF sensor voltage.

You can easily see at the top of the graph that the MAF maxes out early, and (obviously) stays that way. I'm not sure what the g/sec of air at 5.0V is, but at the very beginning of that my injectors are at 85% duty cycle. At ONLY 4700 RPM! CFM of air increases with RPM, so you can now realize that the car gets steadily leaner from this point onward. Even with an entire night of tuning, at 10.8 psi at 5647 RPM my highest AFR is 11.5. Fuel was added after this pull, and while not significantly lean, my injectors are at about 90% duty cycle. Imagine your AFR at 80%...

Oh, another funny thing, the TPS sensor is backwards compared to most cars. 4.XX volts is 0% throttle, 1.0X is WOT. Not a problem for the eManage, and just a little confusing on the Zeitronix. The curve is the same, just backwards.

Code: Select all

Time,                  AFR,      RPM,   Boost(PSI/inHg),   TPS,    User1
7:31:17 AM,     10.90,      4518,          11.40,         0,      4.94
7:31:17 AM,     10.90,      4608,          10.20,         0,      5.00
7:31:17 AM,     10.90,      4608,          11.90,         0,      5.00
7:31:17 AM,     10.90,      4645,          11.40,         0,      4.96
7:31:17 AM,     10.90,      4608,          10.30,         0,      5.00
7:31:17 AM,     10.90,      4608,          11.80,         0,      5.00
7:31:17 AM,     10.90,      4683,          11.40,         0,      4.98
7:31:17 AM,     10.90,      4627,          10.30,         0,      5.00
7:31:17 AM,     10.90,      4627,          11.80,         0,      5.00
7:31:17 AM,     10.90,      4683,          11.20,         0,      5.00
7:31:17 AM,     10.90,      4645,          10.20,         0,      5.00

This is the raw data from around when the MAF maxes out. Fluctuations in boost are due to the boost controller and the small turbo fighting to maintain my designated boost level of 12psi.

In conclusion, please, PLEASE do not put the boost over 11psi on stock management and stock injectors. You'll be significantly lean past this point and will readily knock. This is a serious risk to your engine.

The eManage and the Zeitronix proved to be very worthwhile, an amazing combination. It will take me very far in modding the car.

All comments and questions are encouraged and appreciated.

- the other Phil

Posted: **Mon May 30, 2005 5:07 pm**

very good information.

Posted: **Mon May 30, 2005 6:05 pm**

I can tell you that stock AFR goes to about 10.5 at full boost.

When I get another wbO2 sensor so I can hook up my wb to brothers/friends cars, I'll try to get it on my old SS and see what the AFR's are.

Posted: **Mon May 30, 2005 6:15 pm**

-K- wrote:I can tell you that stock AFR goes to about 10.5 at full boost.

When I get another wbO2 sensor so I can hook up my wb to brothers/friends cars, I'll try to get it on my old SS and see what the AFR's are.

"Full boost" = ?

Stock 6 or 7 psi, maybe about that. But that wont max out the MAF.

Posted: **Tue May 31, 2005 4:09 pm**

I'm pretty concerned about this. It looks like my modding is going to be a lot slower and more expensive than I thought. I mean, I get 9-10 psi stock. You're telling me that I'm already running the ragged edge of my injectors and stock ECU? I thought we could crank boost 4-5 psi before needing to work on fuel and engine management.

I keep hoping that some other experienced people will chime in and expose the flaw in the logic here, but maybe I've just been disillusioned.

Posted: **Tue May 31, 2005 4:37 pm**

I consistently ran 15-17psi on my 91ss for about a year and a half. The tranny gave out a couple of times, but the guy I sold the motor to said the internals were perfect, this was also at 210K. Maybe I had a ringer but I doubt it....

Posted: **Tue May 31, 2005 4:42 pm**

It seems like there's a misunderstanding between what is safe, and what is going to cause major damage. When you look at the numbers of everything it's not safe, but when you go to the real world, it may last much longer than you'd expect.

Posted: **Tue May 31, 2005 6:20 pm**

Maybe... but here's some food for thought. If the injectors are basically wide open at 10-11psi, then upping boost above that point doesn't add any more fuel, and won't add any more power.

Thoughts?

Posted: **Tue May 31, 2005 6:22 pm**

Well, it should create more power, but the issue is, how much more power will it create? Enough to offset the afr?

Posted: **Tue May 31, 2005 7:10 pm**

rallysam wrote:I'm pretty concerned about this. It looks like my modding is going to be a lot slower and more expensive than I thought. I mean, I get 9-10 psi stock. You're telling me that I'm already running the ragged edge of my injectors and stock ECU? I thought we could crank boost 4-5 psi before needing to work on fuel and engine management.

I keep hoping that some other experienced people will chime in and expose the flaw in the logic here, but maybe I've just been disillusioned.

There's no flaw in the logic...this is actual data.

Now, this may definitely be different with stock exhaust. But with an exhaust, you're making comparable power at stock boost to turning the boost up 4-5 psi.

With my 3" exhaust, at 9 psi my injectors were "wide open" (quotes because its wide open as far as the ECU can take it, engine management can get a lot more out of it). Now, that wasn't dangerously lean, but its scary to watch the MAF flatline and your AFR curve upwards a few thousand RPM beore redline.

Now, our ECU may be magical and pull enough timing to not knock. But I really doubt the technology of '91 was better than the knock control of 2002+.

Posted: **Tue May 31, 2005 9:13 pm**

DeusExMachina wrote:
with an exhaust, you're making comparable power at stock boost to turning the boost up 4-5 psi.

Is that really true? 3" from the turbo back will do that?

Posted: **Tue May 31, 2005 9:17 pm**

rallysam wrote:
DeusExMachina wrote:
with an exhaust, you're making comparable power at stock boost to turning the boost up 4-5 psi.
Is that really true? 3" from the turbo back will do that?

Well, look at the numbers. Power is directly related to airflow from the MAF sensor. If I can max out the MAF sensor on 9psi (stock boost), and (assuming) a car with a stock exhaust and stock boost will not max out the MAF sensor (what a poorly designed car it would be if it did!), then I'm making a lot more power over stock.

We started tuning at 6psi..I was getting close to maxing the MAF sensor. I think I flatlined it at redline on 7-8psi.

Posted: **Tue May 31, 2005 10:22 pm**

hmm... I do get a bit scared of the 16-17psi I see in 5th if I let it start getting up there in the revs. That may also be related to the speeds at which one can reach trying to wind 5th out

But it's only then that the EGTs start to approach 1600*F. I've only ever seen it pass that once, and that was on one occasion where I let off the throttle and backfired. Never on boost. Never seen a check engine light or heard any detonation. The EJ22T takes it like a champ, but yeah I want to get on fuel management sometime soon...

Posted: **Tue May 31, 2005 10:25 pm**

Yeah I don't have my EGT sensor or knock logging set up yet. So going that lean might be okay..which would be crazy. heh.

So um, how fast is getting towards the top of 5th?

15psi on a Tbird turbo..yikes.

Posted: **Tue May 31, 2005 10:29 pm**

On stock ECU and stock Injectors at 16psi on the dyno, I was reading 13:1 AFR. Still rich, but not rich enough.

Posted: **Tue May 31, 2005 10:31 pm**

BAC5.2 wrote:On stock ECU and stock Injectors at 16psi on the dyno, I was reading 13:1 AFR. Still rich, but not rich enough.

I wouldn't call that rich, but its not too bad.

Posted: **Tue May 31, 2005 10:33 pm**

Like I said, still rich, but not rich enough.

Lean enough for me to back boost down to 9psi until I get things handled.

Posted: **Tue May 31, 2005 10:36 pm**

DeusExMachina wrote:Yeah I don't have my EGT sensor or knock logging set up yet. So going that lean might be okay..which would be crazy. heh.

So um, how fast is getting towards the top of 5th?

15psi on a Tbird turbo..yikes.

Well, I was cruising on the highway, looked around and saw I was alone, floored it for a few seconds, noticed I was going 110 (my gauges were shaking something fierce... I think I may need an alignment) and decided I'd better slow down. The last thing I need is another ticket.... but anyway no I was nowhere NEAR the top of 5th.

Posted: **Tue May 31, 2005 10:38 pm**

Ohh..okay. I've hit 120 in 4th..thats about where it tops out.

Posted: **Tue May 31, 2005 10:39 pm**

110 is just the middle of 4th...

Posted: **Tue May 31, 2005 10:42 pm**

3000 rpm? or even 4500 rpm isn't 110 in 4th. 120 is about 4500 rpm in 5th, maybe.

Posted: **Tue May 31, 2005 10:51 pm**

From the shift at the top of third between that point and the top of 4th. I guess the slightly past 3/4 point of 4th gear is 110mph on WRX sized tires.

Posted: **Tue May 31, 2005 11:20 pm**

Hmm, I'm a little confused by the numbers your throwing out here "other Phil"

because what we were seeing is that the MAF didn't max out until around 12 psi, and that's on the TD05H-16G! Seems strange that yours is maxing out so quickly and on the VF11.

Any chance you could have a bad MAF or something?

Posted: **Wed Jun 01, 2005 12:53 am**

legacy92ej22t wrote:Hmm, I'm a little confused by the numbers your throwing out here "other Phil" because what we were seeing is that the MAF didn't max out until around 12 psi, and that's on the TD05H-16G! Seems strange that yours is maxing out so quickly and on the VF11.

Any chance you could have a bad MAF or something?

Nobody decided to clue anyone else in?

What did you use to monitor the MAF?

Do you have any numbers?

If I had a bad MAF, why would it give me a reading at all?

Posted: **Wed Jun 01, 2005 1:09 am**

Did you use a non stock maf housing?

legacycentral bbs

Here's some real tuning data...answers and epiphanies inside

Here's some real tuning data...answers and epiphanies inside