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Premium Member
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Discussion Starter #1
I've been doing a lot of searching and reading about turbos and all-motor setups, and studying the various cars here that have these setups. I've seen the following statements and never found a solid answer for them on the various posts.


1. Underdrive pulleys are bad for turbo setups.
2. You shouldn't get your flywheel lightened in a turbo set up.
3. Automatic Transmissions are actually better for turbos than mannuals
4. A valve body upgrade and a torque converter can make an Auto shift faster than a manual.

Could some of you experts like Shawn, Goku, Black Hornet and CThunder help clear the confusion? Could you also explain each answer for this noob? Thanks!
 

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Incognito
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to answer your questions...

the unorthodox pully (as are a lot of other pullys) is bad for turbos is that it is not harmonically balanced. because it's not harmonically balanced, it has the ability to spin faster in a certain position, and more or less spin apart because of centrifugal force. to tell you the truth, I took off my a/c and havent looked back since. but because I live in a moderate climate, I can afford to sweat a little during the summer.

the flywheel follows the same suit as the the pully, it's not harmonically balanced at all, but you can use a shaved stock flywheel for better performance. also, if a flywheel is too light, it will cause undue stress on your transmission causing your tranny to besically detonate itself.

Auto trannys have the benefit of constant boost. because the auto tranny has the clutch plate constantly open so boost does not need to be built back up after a shift. but because of this they generate a lot of undue heat and need to be completely built up. our manual tranny can have a heavy duty clutch and a flywheel, and call it a day, but with an auto, you need a Vb, TC, rebuilt clutches, and probably cryo treated case.

your auto tranny already shifts faster than any human could shift (quit B.S.'ing guys, it takes the auto .2 seconds to recognize it needs to shift and then shift... it takse the fastest human .4 seconds to recognize that you need to shift and then another .2 seconds to tell your hands and feet to shift.) what the Vb and Tc do is shorten the length of time that you tranny shifts, enabling it to shift faste and better than any manual could ever dream of.
 

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Import Tech.
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cthunder said:

your auto tranny already shifts faster than any human could shift (quit B.S.'ing guys, it takes the auto .2 seconds to recognize it needs to shift and then shift... it takse the fastest human .4 seconds to recognize that you need to shift and then another .2 seconds to tell your hands and feet to shift.) what the Vb and Tc do is shorten the length of time that you tranny shifts, enabling it to shift faste and better than any manual could ever dream of.

True , but when it takes the trans a full second to slip from 1st to 2nd , that doesnt help !!! So a Valve body upgrade is a must !!! Short Firm shifts !!! Personaly , its all 5spd. for me , but then agian , I have no Boost ....
 

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Die Trying
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^^i've got a form of boost and i wouldn't trade my 5 spd for anything.

Some say that manuals suck for racing, but they just don't know how to drive em (not you SHAWN).
Now when it comes to single digit 1/4 mile times with top fuel and top alcohol dragsters, then yeah an automatic is better.
 

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Turbo Motorhead
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cthunder said:
the unorthodox pully (as are a lot of other pullys) is bad for turbos is that it is not harmonically balanced. because it's not harmonically balanced, it has the ability to spin faster in a certain position, and more or less spin apart because of centrifugal force.

the flywheel follows the same suit as the the pully, it's not harmonically balanced at all, but you can use a shaved stock flywheel for better performance. also, if a flywheel is too light, it will cause undue stress on your transmission causing your tranny to besically detonate itself.

 

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what would the truth be in getting rid of the a/c to put a underdrive pulley?
 

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Turbo Motorhead
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altimanut152 said:
what would the truth be in getting rid of the a/c to put a underdrive pulley?
^I believe he's just saying his existing pulley is no longer driving his compressor.
 

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oh...ic
 

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makes perfect sense....
 

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My Alti got da last laugh
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nobody put force induction on an auto, it's bad and cost $2000 for just a racing tranny. plus i want to be the fastest force induction auto soon. j/k well at least the tranny cost some money. like cthunder said you'll will need a lot more components. i have yet to find reasonable priced trannies built for at lest 300-400hp. 2500 is the cheapest a good race bullet proof with tq converter. but auto is a good way to go in my opinion. just costs more.

and as for lighening the fly wheel and pulley. i have talkedd to a couple tuners about our car but carl would be a better person to explain if i am correct. you could put a lighter pulley in conjuction with a lightened flywheel if you were to build your bottom end when re-balancing your engine to comply with the lightened flywheel and pulley. would you then be balanced when re-balancing the crank for the lightened parts. just want to know. i'm not sure if this is correct but just would like to know how it could work
 

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Incognito
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once your bottom end is balanced, you would be able to run a pulley, but as I've heard many a turbo gurus say, turbos and pulleys do not mix... Alex M has his turbo and pulley in conjunction, but because he's generally running at such a low boost, the harm is minimal. once he gains the ability to boost more, the less likely his engine will survive with the pulley.
 

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Turbo Motorhead
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I use the stock size and weight pulley and a lightened flywheel (also balanced) to maintain harmonic balancing throughout the rotating assembly. Costs a bit more, but when balanced correctly, you can frequently, no, check that, always challenge the higher realms of the rpm ranges!
 

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ive talk to numerous 240sx KA24DETs and most of them stay away from underdrive crank pulley , the UR pulley doesnt come with a harmonic balancer , hey Black ..swap out that lightened and go with a JUN (chromoly) flywheel ,
 

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Turbo Motorhead
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GOKU said:
hey Black ..swap out that lightened and go with a JUN (chromoly) flywheel ,
I have a custom made Mueller, billet flywheel. It's not as heavy as stock, and not as light (lbs) as JUN.
 

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Premium Member
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Discussion Starter #16
Hey guys another quick question...

Say I was to build up a high performance racing motor (ala SHAWN) with new everything (pistons, cams, rods, etc.), then eventually planned to put a Turbo after the engine was built. I heard that low compression pistons are better for a turbo set up. Is this true? I noticed that Black Hornet has higher compression pistons (8.5:1 right?) Thanks!
 

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Incognito
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low comp is considered 9.0:1 and below. High comp is good for N/A or juiced cars, boost requires low comp pistons.
 

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Premium Member
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Discussion Starter #20
Hey sorry I won't let this thread die but I have more questions!

Well, the reason I've been asking this stuff is because I have been thinking about my performance options with my altima...NA, Turbo, or No2. I've came to the decision that I would like to do an engine rebuild and then eventually put on a turbo. Now here's my next question: Can I do all three?

I know NA means all motor, no forced induction, so it's not technically all three...what I meant was rebuild the engine with all new racing parts (pistons, rods, etc.) to handle a turbo, similar to what I've seen from CThunder and Black Hornet, then add the turbo. Now, can I do that and eventually run Juice? Is it safe to put a nitrous kit on a turbo'd car that's got a rebuilt engine?

Thanks again!
 
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