Precision gen2 68/70 ?

D-MANN

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I purchased a hellion single kit without the turbo and soon will be buying a turbo. Still on the stock block for this year but have a built mmr 4.75 that's 10:1 that was built locally that will be going in next winter. I can't find anyone running this turbo and all info seems the precision 76/75 is the popular choice. For a mostly street car and occasional Friday night track event what turbo should I be going with gen2 68/70 or gen2 76/75 ?


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MG0h3

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Id say the 76mm. Never really seen anyone go smaller than that and they seem to outgrow it somewhat quickly.

Hell I used a 70mm on my pushrod 302 at 10psi and it wasnt too big; spooled up super fast in my opinion.
 

D-MANN

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Id say the 76mm. Never really seen anyone go smaller than that and they seem to outgrow it somewhat quickly.

Hell I used a 70mm on my pushrod 302 at 10psi and it wasnt too big; spooled up super fast in my opinion.

Thanks for the input. I could not find anyone running the smaller turbo in my search.


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MG0h3

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Ya maybe even look at a little bigger; not sure if youre on T3 or 4 flanges.

Dude in this section just went with an 80mm and it sounds like it rips.

Seems like 76 is kindof the starting point on the factory longblock and youll be exceeding that right away. Smaller will spool like a mofo just gotta make sure it doesnt choke it.
 

D-MANN

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Ya maybe even look at a little bigger; not sure if youre on T3 or 4 flanges.

Dude in this section just went with an 80mm and it sounds like it rips.

Seems like 76 is kindof the starting point on the factory longblock and youll be exceeding that right away. Smaller will spool like a mofo just gotta make sure it doesnt choke it.

I have one tuner saying the 76 will be good for the power I want to make(750-800) and another tuner saying that the 68 is all I need and saying I should listen to the tuner and if I do a 76 he doesn't want anything to do with it. Two tuners giving different advice. The first tuner called hellion and precision and they said to run the 76.


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MG0h3

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Lol. Ive never understood why some tuners say "if you dont do this I wont touch it". I mean on some things ya I get it but saying you wont touch what is essentially the industry standard (76mm) seems weird.

I wouldnt go any smaller than 76 and I think you may want bigger especially on that built block. Maybe let some more experienced guys chime in.
 

D-MANN

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Lol. Ive never understood why some tuners say "if you dont do this I wont touch it". I mean on some things ya I get it but saying you wont touch what is essentially the industry standard (76mm) seems weird.

I wouldnt go any smaller than 76 and I think you may want bigger especially on that built block. Maybe let some more experienced guys chime in.

He said I was insulting him among other things by not doing what he said. So here is the post to find out what I should be doing. Either way he won't be tuning this car with that attitude. I just want to pick the right turbo for what I'm doing. Car is a magnum trans but may be auto next year. Every video I found and discussion on the 68 is on smaller displacement engines. Nothing on a 4.6 terminator motor.


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MG0h3

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Ya Im starting to really look at turbos and I wont go smaller than a 76 to start with. Just not sure if I want to go down the rabbit hole.
 

Nightmare302

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The 76/75 is a generic turbo because the average guy prefers to get his answer in a sentence on a forum and just use what everyone else does rather than learn how to read a compressor map. (Plus precision doesn't release their maps.) the 68/70 will out perform the 76/75 if you only want 700-750rwhp. However most guys want bigger so the 76 is popular because it doesn't give up a ton down low but allows for someone to hit 1krwhp (on gen 2s). My personal preference is custom borgs from Forced Inductions. If you honestly think you'll never pass 700-800 and want to keep the stick go with the smallest turbo that will support your goal. The auto will remove a lot of lag complaints if bits correctly stalled.
 

GNBRETT

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I don't believe the 68/70 gen II precision will out perform the 76/75 or 87 on a stock block as it spools up instantly. That 68/70 will be out of its efficiently island on these cars even in stock form and the TQ it will make down low will too much imo.

but as Nitemare stated the BW stuff from Forced Inductions is what I wud be looking at.

have to look at how the power comes in and how linear it is. being more linear helps from blowing the tires off and considering these motors make a LOT of TQ down low it behooves ones to run a bigger Turbo imo.

I went thru this with my street bike last year. the bigger Turbo made the power more linear and therefore I wasn't blowing the tire off. sorta like a built in boost controller.

can't go by HP ratings. My Turbo is rated to 1200 hp so what? I was driving around at about 700 hp and there is ZERO lag. that 68/70 will absolutely BLOW the tires off ur car with a stick or an auto but wud come on really freakn fast and probably be fun as hell lol.
 

D-MANN

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Thanks for the input guys. I will have my tuner make a call to forced inductions and have something set up. That description of the 6870 sure sounds like a blast on the street haha.
Another question I have is jets to restrict the amount of oil. How does one calculate this? Ive read the 4.5ounce in 30 second method hellion recommends. Is that for any turbo?


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Nightmare302

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Thanks for the input guys. I will have my tuner make a call to forced inductions and have something set up. That description of the 6870 sure sounds like a blast on the street haha.
Another question I have is jets to restrict the amount of oil. How does one calculate this? Ive read the 4.5ounce in 30 second method hellion recommends. Is that for any turbo?


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Each manufacturer will have a recommended amount. You just remove the feed line and measure over time.

Most of the Jose's stuff will be journal rather than ball bearing, as such it will be more forgiving when it comes to oiling.
 

D-MANN

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What about turbos from Borg warner? Anything I should be looking at thru them?


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badcobra

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Another question I have is jets to restrict the amount of oil. How does one calculate this? Ive read the 4.5ounce in 30 second method hellion recommends. Is that for any turbo
Instead of a restrictor, run an oil pressure regulator.
http://www.turbosmartdirect.com/Product-Categories/Oil-Pressure-Regulator-OPR-T40/

I've read on Yellowbullet of people having trouble getting through to Forced Inductions lately. I'd call Bullseye or Midwest Turbo personally.

I like the Borg's too. The issue on my car is packaging and trying to squeeze two turbos in there. I like keeping things simple since mine is still just a street car. When I finally ditch these old Garrett's, it's gonna be 6766 or 6870 Precision's without a doubt. Probably 6766's because I'm not rich lol.
 

sutyak

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What about turbos from Borg warner? Anything I should be looking at thru them?

I went from a Precision 76/75 to a BW S369SX-E with zero regrets. Faster spool, and just a monster of a turbo. My motor is also 8.5:1 CR, so yours would spool even faster.

Here is are the maps I came up with to make the decision. I purpose-built a 10.0 car, so I'm just not going to use the rest of the 76/75 that is available. I used a Garrett GTX4202R map as a close approximation to the 76/75, since Precision does not have maps made. As you can see at 667whp, and a potential for 1,000whp it's just barely being used. With the BW S369SX-E, it's much happier and can still hit 800whp or so. I just wouldn't try it on pump gas.
I run around at 10psi most of the time, and 18psi will be for the track. I doubt I'll ever go to 22psi, but I do have the wastegate spring options handy and methanol. :D

If you want that extra headroom then go 76/75. If not, then there are more appropriately sized options.

GTX4202R_PTE7675.png


BWS369SX.png


Physically, the BW is basically the same size as the Precision. It is certainly not a direct drop-in depending on your kit.

20170217_170338.jpg
 

D-MANN

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The BW S369 is what my tuner was recommending and should work with the hellion piping. Hopefully not needing to change much if at all. Price wise the Borg Warner is half the price. Chances are I will run this turbo for the season and go from there.
I'm surprised there isn't much talk on other options after all these years. It's all 76/75 on these cars. I can understand for a race car but most of us have street cars. The faster spool would be crazy fun on the street.


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D-MANN

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Instead of a restrictor, run an oil pressure regulator.
http://www.turbosmartdirect.com/Product-Categories/Oil-Pressure-Regulator-OPR-T40/

I've read on Yellowbullet of people having trouble getting through to Forced Inductions lately. I'd call Bullseye or Midwest Turbo personally.

I like the Borg's too. The issue on my car is packaging and trying to squeeze two turbos in there. I like keeping things simple since mine is still just a street car. When I finally ditch these old Garrett's, it's gonna be 6766 or 6870 Precision's without a doubt. Probably 6766's because I'm not rich lol.

Thanks for that link. Never realized that this even existed till now. Journal bearing I shouldn't need it but if it's a BB turbo later I will get one. Thanks again.


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sutyak

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For the Hellion kit, I had to slightly modify all the piping to fit the BW, and trim the fan shroud. I also went with a Volvo fan for more clearance. There is also the issue of the non-standard conical turbine flange. I had my machinist buddy machine it flat to accept a standard 3.5" V-band:

Marmon_to_Vband.jpg
 

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