Questions for guys running 12-15 psi. - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 10-27-2008, 11:21 AM   #21
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That's why people speak of pressure loss across an intercooler. That and I guess maybe some loss due to friction through the IC. The pressure before and after the IC are not the same. Pressure after IC is lower.
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Old 10-27-2008, 11:29 AM   #22
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Ok I don't get this one. Why would you have more boost when it's colder? Is this because you have an internal gate that references boost at the compressor not the intake manifold?
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Old 10-27-2008, 11:31 AM   #23
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You'll still have the same cold weather problems with an mbc. The car will make more boost when it's colder. Even without any boost controller you can have the problem. If i wanted no more than 12psi on my car I would be over shooting that with just the wastegate pressure when it gets cold. In 40F ambient wastegate pressure is 15psi for me. Tell me how to fix that with an MBC.

My thought was if a MBC is used, you could set it to wastegate levels. (In our cases that is 11-12psi.)

So if the solenoid is causing overboost one cold morning, you flip the switch and fail to a MBC at wastegate levels. Wouldn't hurt your performance as much as failing completely to wastegate.
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Old 10-27-2008, 12:09 PM   #24
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Ok I don't get this one. Why would you have more boost when it's colder? Is this because you have an internal gate that references boost at the compressor not the intake manifold?

Someone a lot smarter than me can probably explain the physics behind it but I like to look at things logically so lets think about this scenario.


You wire your internal wastegate flapper door open. You car can still make some boost, maybe 1-3 lbs typically. My daily for reference was making 5 to 6 when I lost the end of the adjustable arm Friday night. It was around 60F. Now we've completely taken the wastegate actuator and any boost controller out of the equation along with where it references boost. Now what happens when the ambient temp drops to 40F? Boost goes up. Ambient temp rises, boost goes down.

So we can see there is always gonna be variation in how much boost the car makes depending on the ambient temps. Therefor the only thing we should expect to control is how high it can go over and above that amount. The way the open loop control in MS works is it controls the solenoid at a certain duty cycle based on current RPM and Throttle position regardless of how much boost is actually currently being made. So if ambient temps change a lot this method of control is not very consistent. A feedback control system would work better. If the solenoid was controlled based on RPM, TPS and what the actual boost level is we could avoid this varying ambient temp issue, as long as the boost level desired is over what the turbo will produce with no boost control.
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Old 10-27-2008, 12:29 PM   #25
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I prefer the set overboost to 18 psi, tune for 13 psi at like 70* ambient and then let it do w/e the hell it wants with weather changes
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Old 10-27-2008, 12:51 PM   #26
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I think Paul's method of haveing a couple different maps for different temps is the best we can do with MS. I agree it is annoying as hell. I've got a question. Right now I'm running 14psi and letting it shoot to 15ish. My top KPA row is 212. If I set my EBC to 15psi it'll probably shoot higher than my top kpa row. I guess this a problem? MLV can't really tune that high without a cell up there? So should I be adding something like a 230 KPA row if I want to increase the boost to 15 psi?

edit: Now that I think of it, Paul, how the hell are you not completely maxing out the injectors when you overshoot to 18psi?
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Old 10-27-2008, 03:31 PM   #27
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My top rows are at 230kpa.

I am maxing out my 460s. I have a Vortech sitting here waiting to be installed because
1. it was much cheaper than buying and cleaning 550s.
2. i think there is something to be said for higher fuel pressure with smaller injectors. better atomization, more instant fuel.
3. the 460s should idle better than 550s although I don't have idle issues with 550s on the other car.
4. they are already in the car.
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Old 10-27-2008, 03:40 PM   #28
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So since this has turned into an EBC thread; what needs to be done for somebody to fix the closed loop control? Is it just getting the right settings, or a new version of firmware, or can MS1 just not handle it?
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Old 10-27-2008, 03:44 PM   #29
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I've hit 90% DC at ~7k RPMs at 15psi and an AFR of 11.5 on my 550s. I think I've I wanted to go any higher in boost I'd have to lean out things to 11.8
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Old 10-27-2008, 03:47 PM   #30
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Quote:
Originally Posted by paul View Post
My top rows are at 230kpa.

I am maxing out my 460s. I have a Vortech sitting here waiting to be installed because
1. it was much cheaper than buying and cleaning 550s.
2. i think there is something to be said for higher fuel pressure with smaller injectors. better atomization, more instant fuel.
3. the 460s should idle better than 550s although I don't have idle issues with 550s on the other car.
4. they are already in the car.
I like this thought process.
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Old 10-27-2008, 04:23 PM   #31
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I like this thought process.
+1. I'm doing something similar with 550's. Got a 30-100 PSI 1:1 Mallory FPR that's going in when I put the 255HP in and block off the stock in tank regulator. Probably set it to ~70PSI at atmospheric pressure. That will keep a 70 PSI delta at all times. My setup will be different, but in the end it will accomplish the same thing on my 99'. Higher pressure, more fuel, better atomization, more headroom, etc.
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Old 10-27-2008, 04:25 PM   #32
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So since this has turned into an EBC thread; what needs to be done for somebody to fix the closed loop control? Is it just getting the right settings, or a new version of firmware, or can MS1 just not handle it?
MSI doesn't support it. I have no idea if someone smart could write the code to make it suppport it. I would be it's completely possible. I got a feeling MS2 would support it more easily. Gotta talk to Abe about it one day, he knows more about MS2 than I.
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Old 10-27-2008, 04:39 PM   #33
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there is a thread on msextra.com discussing how to fix it. it involves a code rewrite and some people have offered to tackle it. every couple of days there is another post but so far no fix. Boost Control change request
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Old 10-27-2008, 04:52 PM   #34
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hell, I'd be happy with dual DC% table switching. I bet it's as simple as making some changes in your .ini file
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Old 10-27-2008, 11:44 PM   #35
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what I don't understand is why the Hydra or other controllers can't automatically adjust the boost levels due to outside temperature. Maybe this is the closed loop solution being discussed above. It is very annoying when I get overboost in the morning driving to work and crappy performance heading home... And this is LA with some of the most stable temps in the nation! What is this car going to do when I get back to the midwest and there is +- 20F changes every couple of days. ARGH!
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Old 10-29-2008, 05:19 PM   #36
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what I don't understand is why the Hydra or other controllers can't automatically adjust the boost levels due to outside temperature. Maybe this is the closed loop solution being discussed above. It is very annoying when I get overboost in the morning driving to work and crappy performance heading home... And this is LA with some of the most stable temps in the nation! What is this car going to do when I get back to the midwest and there is +- 20F changes every couple of days. ARGH!
It doesent seem like it would be hard to have MS use a KPA table for the boost control. I mean it has the feature, but it doesent hold a steady boost/work well. Can the processor not handle it or is the code just not well written?

The tempture compisation is a neat idea too, add or subtract boost DC% depending on air intake temps.


And finally, yeah I would be veryyyyy happy if they could just code it so that you have like 2 or 3 switchable DC% maps. I would think that would be easyer than both ideas above, and still work pretty good.
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Old 10-29-2008, 08:57 PM   #37
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This morning my car boost went to 12psi. Oh -yea. I have a weak clutch and it spun through first and fish-tailed in 2nd. It will be hard not to turn it to 14psi.

Cardriverx, did you build your motor? Or is the stock 1.6L holding 14psi on a T3?
I bet that is wild in boost.
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Old 10-29-2008, 09:43 PM   #38
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I haven't had any crazy variations in boost level running closed loop on the LINK. It looks the same at 50F that it did this summer at 90F. It's not a super level curve- about a 1 psi variation from 4-7k.
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Old 10-29-2008, 10:08 PM   #39
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I started experimenting with my closed loop boost control again today. Hopefully I'll come up with something positive.
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Old 10-30-2008, 01:04 AM   #40
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This morning my car boost went to 12psi. Oh -yea. I have a weak clutch and it spun through first and fish-tailed in 2nd. It will be hard not to turn it to 14psi.

Cardriverx, did you build your motor? Or is the stock 1.6L holding 14psi on a T3?
I bet that is wild in boost.
I have been running 12-16psi for a long time now, I have a simple mechanical wastegate control, and I think I last set the spring tension in 1999...

Believe it or not, you can control boost with the accelerator pedal. When I was having misfire problems at high boost, I just (tried) to keep my foot out of it to avoid experiencing the misfires.

As far as reliability, I'm around 90Kmi now and no engine problems so far. I drive as you describe, heavy foot, but shift before 6500 most of the time. Used to race a little, but I still shifted relatively early - my racing was harder on the brakes than anything else.

Most important thing for your engine safety is to get your fueling right. When in doubt, go for the rich side of ideal. Ignition timing retard hasn't done much for me in terms of eliminating knock problems, except in the 1000-2000 RPM range near WOT. Any other map area where I've had a knock, it has been a lack of fuel problem. I can still run a bit rich at 16psi / 7KRPM with 310 injectors, it seems that most kits are coming with larger ones these days, but in a stock 1.6 motor I haven't found a need for more than 310.

If I had socked away $100 a month toward a replacement motor, starting when I installed my turbo, I could afford a pretty sweet replacement engine by now:

Flyin' Miata : Engine/Drivetrain : Built engines : FM built stroker engine
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