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Removed my mbc with unexpected results...

 
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Old 05 Mar 2004, 11:29 pm
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Default Removed my mbc with unexpected results...

The other day I decided to remove my mbc. I had it hooked up to Solenoid #2 (the old way). It usually will feel good for 3-4 days but then will start to feel anemic like the computer is up to it's tricks trying to normalize performance.

I also decided to remove the intake turbo up and see about fabricating a new home made intake. I have an old Neon R/T AEM kit that I can cut apart and fit together to get the right bends and lengths.

Anyways, when I put the intake back on and reset the computer the car felt awesome. It's been pulling strong and I've been getting the best stock boost I've seen yet. I've reset the computer in the past after making changes and have never seen this type of reaction.

It's very strange because it's boosting like the mbc is still there but yet it feels like it's making great power at the elevated boost levels. Not like when I have the mbc on and often times see higher boost but feel poorer performance. BTW with stock pcm I get about 9psi max then drop to 4-5psi usually. With mbc I set it to get about 11psi then it drops to around 8psi. Right now it's boosting to 11psi and sometimes it's even holding it up there.

I wonder what happened. It's felt great for a few days now, I'm afraid to touch or adjust anything. I hope it keeps it up. Boost is well within acceptable tolerances. When I had the intake off I checked all the hoses (wastegate etc...) to make sure everything was snug.

I also had the tsb pcm replacement done about 6 weeks ago. That made a great difference. It used to stutter bad after around 5100 RPM's but now pulls strong and smooth right until it shifts. Well worth it.

Well I'm not complaining or anything. Maybe the GT is getting excited that spring is around the corner...
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Old 06 Mar 2004, 09:23 am
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Sounds odd.

Maybe one of the lines you moved around has a crack in it? This might explain that you checked them all and they're snug, but may still be bleeding air.

I dunno, just sounds wierd.

Enjoy it for now, lol!
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Old 06 Mar 2004, 09:46 am
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This same thing happened to me some time back with my Hallman controller.

Enjoy it for a wile. the computer will adjust itsef within a few days. Once I reset the pcm I would see boost of 16 PSI but after a few accelerations the boost would stay at 14 PSI instead of the 12 PSI originally set.

Ian
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Old 06 Mar 2004, 05:44 pm
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I noticed the same thing when I got my GT back from the body shop. It sat with the battery disconnected for a long time while waiting to be fixed. I am going to put a battery disconnect switch (high isolation weatherproof sw from summit racing) in the negative battery line. I also will run a separate ground from the neg terminal to the head unit ground. I have tons of settings in the head unit that must be reset( crossover frequencies, DSP settings, Base levels and phase etc) This way I will keep those settings when resetting the CPU.......
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Old 09 Mar 2004, 10:44 pm
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Seems like if we got another PCM we could hold a lot more boost!!
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Old 11 Mar 2004, 12:26 am
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Sure enough the performance has returned to normal. High boost is 10psi or just under, low boost is 5-6 psi.

I wish that I could convince myself that putting my mbc on gives me more power. My boost gauge will read 2 psi more but it just doesn't feel like I'm getting any more power. Anyone else experience this?

Also, anyone with the TurboXS standard boost controller... how many turns do you set it at? I usually do 2 full turns of the screw at most. Maybe I need to crank it up more...
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Old 11 Mar 2004, 02:18 am
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I don't have stage 1.. just an 03 auto stick with cone filter, EBC, and exhaust. There is most definately a difference I was doing around 40 mph on the freeway stuck in traffic today, and the lane next to me was going faster and opened up briefly. I moved over and stepped on it - squeeling tires until i was well past the car that had been in front of me. I'm not talking just a chirp - I'm talking a long drawn out squeeling! My car never did that stock I'm going to see if I can get some dyno time this saturday to tune my EBC some, I'll post the results if do...
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Old 11 Mar 2004, 02:20 am
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also, check out the srt forums for some ideas, etc.. they post plenty of dyno results - these engines are definately tunable []
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Old 11 Mar 2004, 07:50 pm
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I put the MBC back on today.

It seems the culprit isn't the computer trying to normalize boost, it's the traction control system trying to limit wheel spin.

When I'm in autostick and know I will need to accelerate quickly I will tend to ride the gear I'm in a little higher in rpm's to be ready for when I need that extra go. Usually this will result in less tire spin than when the auto downshifts. I've noticed boost holds higher and longer in autostick because of this simple fact.

I tested WOT with traction control off and on and the difference is night and day. When my tires would brake loose with it on it would drop me to 4-5psi and then seem to hold around there. With the tc off I would get up to 11psi and hold in that neighbourhood.

This info has probably been posted before a number of times. It's just my slow way of putting 1 + 1 together.

The MBC is staying on now. Traction control is coming off when the need for speed is there. Now to hit the local dyno.
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Old 16 Mar 2004, 11:35 am
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Have you took your Pt out to a drag strip yet??? Can you launch yout Pt with out the T/C on and not spin your tires???

Don
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