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Thread: 91 spirit rt family car

  1. #21
    Slugmobile & MeanMini Caretaker Turbo Mopar Contributor wheming's Avatar
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    Re: 91 spirit rt 12 second family fun car

    That's a fortunate turn of events that brought it to a good home, rather that suffer the fate of a part out from loosing interest.
    Good on you!
    Wayne H.

    '91 Dodge Spirit ES 2.5L turbo 5spd
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  2. #22
    turbo addict
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    Re: 91 spirit rt 12 second family fun car

    Quote Originally Posted by BeeZnutZ1979 View Post
    Yeah I'm pretty happy with how it performs now, I had the exact setup that I'm running now but the stock Garret turbo and it ran a 13.5@104 mph. Switched to the holset and stayed at 18 psi and pulled the 12.6@111 mph, I can definitely tell that the motor is breathing easier through the holset than the little Garret. And yes I run 93 octane pump gas, the intercooler is just a cheapo cx racing cooler I bought off of eBay. It's a dual pass intercooler thats 29 x 10 x 3.5 inches thick,had alot of people tell me there junk but it's working great for me and installed really simply in my car. I was going to turn the boost up more and try to go a little faster but was starting to run a bit lean towards the end of the track, never had the fuel pump out but I believe it's just a stock pump.
    Quote Originally Posted by tryingbe View Post
    This person has a dual pass, boost drops was 13psi.

    http://www.turbo-mopar.com/forums/sh...l=1#post995200

    His intercooler was bigger than yours.
    Quote Originally Posted by wheming View Post
    With no changes other than some good slicks (like my favorite M&H Racemasters ) you should be able to get 60' times down to 1.80, which would make your 12.65 more like 12.2!

    And as tryingbe mentioned, the bad part about the 2-pass intercoolers is they are restrictive (however that can make for good temperature drop -heat transfer) but that means there is significant pressure drop across them. You should try to measure how much boost pressure you have before and after your intercooler.
    (Simply try to get a boost gauge reading turbo outlet, and you probably have boost reading at your intake manifold already.)
    Quote Originally Posted by BeeZnutZ1979 View Post
    I can see how they would be more restrictive than a single pass but what would be the disadvantage of pressure loss? Obviously my turbo is capable of pushing way more than 20 psi. So even if pressure is above that pre intercooler there's no way I'm overspinning it trying to reach my desired boost level. Plus I'm about as far with this car as I plan on taking it, no need to sqeeze every last drop of power out if it, a 12 second family car is cool enough for me. I have a Daytona drag project car for pushing the limits with which has a single pass intercooler.
    Quote Originally Posted by wheming View Post
    Downside is just the turbo is working harder, and if you kept trying to increase boost in the intake, then you could be outside the design limits of the turbo.
    It is work the turbo is doing, with not much gain due to restriction in the intercooler.
    But i think it is great you are turning those numbers with that setup! Like i said, the temperature drop across it is probably good.

    An air/air is only going to pull so much heat out of the system. If you took your i/c and make it a single pass the air would move 1/2 as fast through it so it would cool the same with 1/2 the pressure loss. On top of that it has to make a 180 degree turn to go the other way. So now you've slowed down the air, and dropped the pressure loss. And lets use a 13psi pressure loss and a 18psi intake pressure. So your turbo has to spin to make 31psi. This means the compressor is pumping more heat into the air which taxes the i/c more. On the exhaust side you've noticed how going to a bigger turbo has helped the car breathe. Now imagine if instead of opening the WG at 31psi you could open it at 18!!! And how much farther it would open to keep the boost lower. Lower compressor speeds means cooler air so the i/c doesn't work as hard which will lower your intake temps. Lower turbine speeds means more flow sooner. which all equals more hp. A slightly larger single pass unit with a 1-2psi pressure drop or less and you could probably hit 11's@18-20psi with good traction. Our points is that you're leaving a HUGE amount of hp on the table with that i/c. T3's like lots of flow and you saw this with the turbo upgrade. Now you need to upgrade your intake side. You've upgraded everything else for flow then stuck a cork in the system.

  3. #23
    Mitsu booster Turbo Mopar Contributor
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    Re: 91 spirit rt family car

    Ok, I have thought about cutting the end tanks off and making a single pass out of it. I'll weld a fitting in the intercooler tube pre cooler and get some readings to see how much pressure loss I'm actually dealing with, if it's to much I'll modify my cooler or buy a better one, thanks for the advice!

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