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Discussion Starter · #1 ·
Hello all. Currently running 15psi on a vortech Si with a 3.0 pulley, pretty much maxxed out as I'm already overspinning it some. Looking to upgrade to a Ti, but was unsure of pulley sizing to go with. I'd like to be in the 17-18psi range, and I know the Ti flows quite a bit more. I have a 3.15 pulley, was thinking of just trying that first but I don't really want to pay for a dyno tune session and still only be running 15psi again. Was wondering if someone else had some experience upgrading to a Ti from an Si and what your experience was with pulley and boost levels. Thanks
 

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That sounds like the right move. There really isn't a HUGE difference between those two blowers. Slap the 3.15 on and find a 3.33 just in case.
 
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Discussion Starter · #3 ·
That sounds like the right move. There really isn't a HUGE difference between those two blowers. Slap the 3.15 on and find a 3.33 just in case.
Thanks for the reply. So you think I might be more than 18 with a 3.15 pulley? I know it's purely guessing and speculation, but I don't have any experience with a Ti so I don't really know what to expect. I've actually had 4 turbo cars before and this is my first supercharged one. I know I'm different than most people but I honestly and actually like the charger better. I'm switching to E85 at the same time as this upgrade so honestly even if it does end up more than 18 I'll probably be OK. I have a 20psi boost gauge, would be kinda cool to peg it LOL.
 

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Figuring out specific boost levels is hard to do as every engine is different. The other thing you could do is look on vortech’s site compressor maps. There you could see your current output vs a ti rpm wise.
 

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what diameter is your crank pulley, and what is your shift point? an si is done around 750ish @ the wheels. a ti has seen north of 1000. id say a sizeable difference.
 

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Discussion Starter · #6 ·
what diameter is your crank pulley, and what is your shift point? an si is done around 750ish @ the wheels. a ti has seen north of 1000. id say a sizeable difference.
7'' crank and shift about 6700. I have a self contained V3 so it's supposed to be limited to 52k, but I'm turning it 56k just to get to 15lb. I'm not even over 600whp, let alone anywhere near 750. Now, I am on pump gas with 10.25:1 compression, so the timing is backed way off in the tune. I know there's going to be big gains just going to E85, but I would like to run a couple more pounds too and I'm already overspinning so I really can't go to a smaller pulley on the Si. There's a company that upgrades your Si to a billet wheel Ti with a full rebuild for a reasonable price, about $1200. If I can get back to a 3.15 pulley, that'll get me down to 53.5k impeller speed and hopefully still be running more boost too. That's what I'm looking for anyway.
 

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right, i was thinking v1. in that case you will be moving more air at lower discharges with the ti. because of this you will see increased back pressure. how much is hard to say, and really it isnt a valuable metric to reflect power although there is a relationship. if youre @ 15 now and use same pulley config its reasonable to assume youll be 18-20. but again really a meaningless value. maybe look into alcohol/h2o injection to buy some advance, but e85 will offer similiar results. good luck sounds like itll rip.
 

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Interesting. I swapped from a s trim to a t trim same pulley size lost power. 7" crank 2.75 blower size. Maybe I got to much belt slip. Going with 35mm cogs on the t trim. Compression ratio little below 9. Always over spin the blowers. Wish u luck let us know how u make out.
Heard the ti trim loves to rev hi.
 

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Discussion Starter · #9 ·
Interesting. I swapped from a s trim to a t trim same pulley size lost power. 7" crank 2.75 blower size. Maybe I got to much belt slip. Going with 35mm cogs on the t trim. Compression ratio little below 9. Always over spin the blowers. Wish u luck let us know how u make out.
Heard the ti trim loves to rev hi.
Are you still 6 rib? I did an 8 rib conversion.
 

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Discussion Starter · #12 ·
Who is this company? Thx.
Technically it's $1295, but they said they'd credit me $100 for my good cast Si wheel.

 

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2.95 and an 8"

ti takes off in 52000+
7'' crank and shift about 6700. I have a self contained V3 so it's supposed to be limited to 52k, but I'm turning it 56k just to get to 15lb. I'm not even over 600whp, let alone anywhere near 750. Now, I am on pump gas with 10.25:1 compression, so the timing is backed way off in the tune. I know there's going to be big gains just going to E85, but I would like to run a couple more pounds too and I'm already overspinning so I really can't go to a smaller pulley on the Si. There's a company that upgrades your Si to a billet wheel Ti with a full rebuild for a reasonable price, about $1200. If I can get back to a 3.15 pulley, that'll get me down to 53.5k impeller speed and hopefully still be running more boost too. That's what I'm looking for anyway.
what company? i would be interested in something like that.
 

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Discussion Starter · #15 ·
2.95 and an 8"

ti takes off in 52000+

what company? i would be interested in something like that.
2.95 and 8'' crank pulley would put me over 65k impeller speed, pretty sure it would just blew up lol.

Here's the link for the Ti upgrade-

 

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There are a few companies that make billet impellers. I've thought about switching my Si to one but I just haven't seen enough data that is compelling me to do so. A simple before/after data log would be awesome to see Intake temps and boost differences.
 

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Discussion Starter · #19 ·
Nah... I spin mine 65k plus everytime it's out.
All it does is gap GT500s, TT lambos, demons, and ZR1s.

I do have the good HD bearings though.
I have the V3 self contained unit. And actually the whole reason I'm looking to do this upgrade is because the seal blew out in it after turning 56k a few to many times I guess.

There are a few companies that make billet impellers. I've thought about switching my Si to one but I just haven't seen enough data that is compelling me to do so. A simple before/after data log would be awesome to see Intake temps and boost differences.
I was looking at the JB performance Si wheel that supposedly flows 1300cfm over the stock 1150, but I'm sure billet wheel from supercharger rebuilds flows more than stock too so going to a Ti and billet should still be 1500+. I'm not going to risk spending $900ish to rebuild with a billet Si wheel and it not get me enough flow to get the boost I want while spinning the unit slower, so I'm going all out lol.


im running 14psi on my 408 with a V3SI. 8" and 3.33". 6000rpm
There's a HUGE difference in spinning 6000rpm vs 6700rpm. With an 8'' crank and 3.33 pulley, at 6k your impeller speed is 52k but at 6700rpm your impeller speed would be 58k. I already blew my shaft seal at 56k on the V3. My problem is I'm spinning to fast, I don't need an 8'' crank pulley I need a charger that flows more so I don't have to spin it as fast to make the same or more boost.
 

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I have the V3 self contained unit. And actually the whole reason I'm looking to do this upgrade is because the seal blew out in it after turning 56k a few to many times I guess.



I was looking at the JB performance Si wheel that supposedly flows 1300cfm over the stock 1150, but I'm sure billet wheel from supercharger rebuilds flows more than stock too so going to a Ti and billet should still be 1500+. I'm not going to risk spending $900ish to rebuild with a billet Si wheel and it not get me enough flow to get the boost I want while spinning the unit slower, so I'm going all out lol.




There's a HUGE difference in spinning 6000rpm vs 6700rpm. With an 8'' crank and 3.33 pulley, at 6k your impeller speed is 52k but at 6700rpm your impeller speed would be 58k. I already blew my shaft seal at 56k on the V3. My problem is I'm spinning to fast, I don't need an 8'' crank pulley I need a charger that flows more so I don't have to spin it as fast to make the same or more boost.
unfortunately I think you're going to need a different head unit. si is still an si.
ysi or procharger.

or get bigger pulleys and use nos.
 
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