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Thread: 89 CSX 10 rides again!

  1. #1
    Garrett booster
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    89 CSX 10 rides again!

    New life in this car! Like to give a huge thank you to @Milkcarton for his expertise in helping with getting this car back on the road, I am very grateful. I also had new exhaust (thank you to Cindy at FWD Performance) for all the pieces I needed. A trans swap, new clutch, cleaned/flowed injectors lots of misc. maintenance, and a little fiberglass work necessary for a maiden voyage after an 8 year nap.

    I have some questions. After installing the new exhaust (2.5”), it will now go into huge overboost and shut the car off completely. It’s only done this twice and I recognized it, so I drove home with a pretty light foot. Will probably install the diode to trick the MAP until the new computer gets here from FWD. Question 1. Since it’s never done that before, what could cause that after a long nap? Nothing else had been touched. Anything I should look for?

    Question 2. There was a member here years ago that was a upholstery specialist. Is he still on here? I have the original Shelby floor mats that I’d like to have redone. They are in pretty rough shape and wondered if they could be saved. Thanks for any help!

    Ill keep working on how to post pics.

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  2. #2
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: 89 CSX 10 rides again!

    If the car is still VNT, the free flowing exhaust will most likely overboost no matter what you do. They corked the exhaust to control the boost, as the 2.2 is too large for the tiny VNT turbo. Do you still have the stock air box on there with a regular filter? That will help some. I have CSX VNT #497 with a S60 VNT turbo on it and the car can fairly well control the boost with larger exhaust, but I've tried to choke it off as much as possible, and to be honest, I never wind it out because I know that it will just overboost. When I need to do some exhaust work, I'll put a more restrictive exhaust on the car.

    I wouldn't think of doing a zener diode on the car. With the guys on the site offering flash modules for SBECs, and the tuning capabilities that come along with that and tools like the MPSciLink, I wouldn't dream of going back to the dark ages. Aside from that, I also wouldn't do it because you'll overspin a VNT in short order at higher boost levels. If you've ever had one apart, you can see that the wheels are tiny and the RPM necessary to generate more than stock boost levels is insane.

    If you want to mess with the VNT a little, there is some good information from 5digits on TDG from back when. Testing for minimum attainable boost is included in there if I'm not mistaken.
    http://www.thedodgegarage.com/turbo_vnt.html
    thedodgegarage.com/5digits_turbos.html


  3. #3
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    Re: 89 CSX 10 rides again!

    If you trick the map you'll probably get melted pistons the vnt will just put in tons of boost and lean it out

  4. #4
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    Re: 89 CSX 10 rides again!

    It still has the original VNT. Couldn’t you just use a boost controller with the diode?

  5. #5
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: 89 CSX 10 rides again!

    Quote Originally Posted by 89csx10 View Post
    It still has the original VNT. Couldn’t you just use a boost controller with the diode?
    You're overboosting because the VNT can't control the boost. As you make more boost and more power, it will just runaway more and more. You're essentially trying to trick the map to allow the turbo to make all the boost it possibly can. That will probably cause detonation due to the insane heat the VNT will be putting out. It will also spin the VNT to death in short order. I attempted to find a compressor map for it, and the one crude map seemed to indicate that at "all of it" boost levels, you'll be further off the map than Columbus was.

    What are your goals for the car? If you want a fun driver with instant boost and the street cred of it still being VNT, you'll need to cork the exhaust. If you want something significantly faster than stock, you'll need a different turbo. To hopefully put it in perspective, 5digits used to say that if you want to work on the exhaust of the VNT, just use a TBI muffler because they are higher flowing, but you won't overboost.

  6. #6
    Supporting Member Turbo Mopar Contributor
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    Re: 89 CSX 10 rides again!

    Quote Originally Posted by cordes View Post
    TBI muffler because they are higher flowing, but you won't overboost.
    Did you mean higher backpressure?
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  7. #7
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    Re: 89 CSX 10 rides again!

    Well, it’s a learning experience for sure. Just a fairly stock driver was all I was going for, with mods being the exhaust and a stage 2 tune from Cindy. Maybe should have done some better research. I’m not driving the car as a daily or anything. It’s completely stock and I’ve owned it for about 12 years now. Just wanted to liven it up a tad. I won’t be redoing the exhaust, with putting the money into having it done and ordering it from FWD. I imagine the new computer will adjust for this to a certain extent and I certainly don’t want to kill a good car. Thanks for your replies guys.

  8. #8
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: 89 CSX 10 rides again!

    Quote Originally Posted by chromguy View Post
    Did you mean higher backpressure?
    If I recall correctly, the TBI muffler was higher flowing than the stock unit, but would still allow for the computer to control the boost.

  9. #9
    Supporting Member Turbo Mopar Contributor
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    Re: 89 CSX 10 rides again!

    Quote Originally Posted by cordes View Post
    If I recall correctly, the TBI muffler was higher flowing than the stock unit, but would still allow for the computer to control the boost.
    Ah OK thanks
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

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