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Old 04-20-2017, 10:43 PM
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Turbo upgrade

Hey guys I'm contemplating upgrading my turbo on my 72 nova. It's a sbc 355 with roller cam afr heads and fast xfi fuel injection. Currently I'm running a gt45 (68mm) turbo on it. I was thinking about upgrading to a s488 (88mm) turbo. Anyone have any idea what kind of power increase I can expect or any advice. Is it worth the money and time? Thanks in advance.

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Old 04-20-2017, 10:54 PM
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Also open to other turbos
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Old 04-21-2017, 03:38 AM
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You're turbo, if it's not a genuine GT45 (Chinese knockoff), is holding you to a range of 600-750HP, where as the 88mm S488 will run well past 1000hp with no effort. The S488 will take longer to spool and may not be able to run the amount of boost you want if you have somewhat of a NA grind rather than a turbo grind cam.

This choice comes down to your goals and your motor. Your 350 is going to have to run alot of rpm's to get the maximum output from the S488. If your long block can handle that, then fine. My opinion can be described by a present build I'm working on - using an 80mm S480 on 400+ ci SBC that will run to 7K - I expect that we will be able to make 1000+ at or below 14psi. I wish I had it done to give you some more accurate info , but soon hopefully.

Have you looked at an S475? They can be had somewhat cheaper and will quite easily support 800-1000.

What are your goals (HP) and application? And what are your cam specs?
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Old 04-21-2017, 10:24 AM
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Wow great info guys actually I was thinking about how well my turbo would spool the 88mm. My redline is 7000-7150 so I cap out there and my goal is around 1000hp my charge temps do get very hot. Even with an intercooler and 3 inch charge pipe my pipes get hot to the touch so they are very warm. I would say they aren't to far off from what my coolant temp is to take a guess. My cam is a edelbrock rolling thunder hydraulic roller .540 lift and Int dur 234 exh dur 238 with a 112 lsa. So I feel with the gt45 I may be capped on power. I don't think that turbo will take be above 650-700 unless I drive the boost levels up really high which then heats my intake temps even more.
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Old 04-21-2017, 10:27 AM
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Also forgot to mention that the turbo I plan to upgrade to will require little modifications to make fit. An adapter will fit it to my exhaust manifold then I'll have to well a vband onto the beginning of the charge pipe no big deal and then just fab a new larger down pipe and reuse the same feed and drain lines. Very simple.
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Old 04-21-2017, 11:09 AM
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That's alot of cam for a turbo. If it has the 107 ICL, then it's probably not helping. You could put ina smaller cam and make more power - I'm confident. The real test would be to detemine your back pressure ratio. I'll bet with all of the overlap and the exhaust duration that you're at or approaching 2:1 if your GT45 is a journal bearing turbo (what is it?). With that in mind a ball bearing turbo does a much better job controling back pressure as it takes much less pressure to spin them.

What are your intake temps? Over 130? Doesn't your Fast XFI have an intake temp sensor?
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Old 04-21-2017, 11:17 AM
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It is a journal bearing turbo and I forgot to mention it is an eBay special. Please don't judge lol. The fast system has everything yes it has an intake air temp but I have not gotten around to tuning it and driving it since I literally just finished installing it. Actually that's the reason for this post. I was planning on upgrading my turbo for this season and I would rather not waste anytime building and tuning a map for the smaller turbo if it going to replace it right now. I'm a little concerned that my little 355 will have a hard time spooling the 88, am I being dramatic or will it be fine? The up pipes are 2.5
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Old 04-21-2017, 11:18 AM
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I would be willling to put money that the charge temps are 130 or more
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Old 04-21-2017, 02:29 PM
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Quote:
Originally Posted by Pupsvette76 View Post
I would be willling to put money that the charge temps are 130 or more
Don't guess - find out.

What are your goals? What are the block, rods and pistons capable of withstanding? These questions need to be answered prior to putting on a 600 HP power adder. At least IMO.
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Old 04-21-2017, 10:24 PM
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The hot sized is wrapped I do run a water meth injections from Snow and I currently have 3 inch intercooler piping. I'm not sure that the engine makes power wise right now but my goal is 1000hp and I really want to upgrade to the 88mm. After that will come all the accompanying upgrades like larger intercooler and piping. I think the larger turbo is the key to power levels in looking for.
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Old 04-22-2017, 06:39 AM
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So you're running meth injection, for racing/dyno applications, meth is all that is needed to keep the intake temps under control. It would be great if you had an intake temp sensor in the manifold (behind the meth) rather than in the intake piping so that you can see the effects of the meth.

Do you have a link to the 88mm turbo you're referencing?

http://www.mandmturbochargers.com/bw...l_783_1018.pdf

I'd recommend the 75mm 171702 on page 62, or the largest I'd go is the 80mm 177287 on page 63 (or equivalent journal bearing knockoffs). I'm assuming the 88mm you're thinking of is something along this line : VS Racing.

The 1.32 exhaust housing is going to be dilemma for you if you expect this thing to spool during street driving. 1.32 is large and will take a good amount heat (engine load) or alot of rpms from a 350 (4000+).

With all this in mind, you haven't mentioned if this is a track purposed build. If it is and you are willing to run this over 6000-7500 rpms, then the 88mm with the 1.32 exhaust AR will work fine IMO. The best of both worlds is a T4 flanged S400 or ball bearing T4. Something from Precision, Bullet, Comp, etc., but they are not cheap. Easily can spend $1500+ on one which I think is somewhat unnecessary.

Another member here, ForceFed, is much more turbo knowledgeable than I, hopefully he will happen along.
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Old 04-22-2017, 11:27 AM
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I don't remember what jet I'm using but it's the snow stage 3 boost kit and I'm using their proprietary boost juice. And yes I was looking at exactly that turbo from vs racing
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Old 04-22-2017, 11:33 AM
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The car is mostly a race/drag car that may be registered to be driven on the street occaisionally. You think 1.32 is too big what should I shoot for. I'm not as knowledgeable on turbos as I would like to be enlighten me lol
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Old 04-22-2017, 02:29 PM
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Quote:
Originally Posted by Pupsvette76 View Post
The car is mostly a race/drag car that may be registered to be driven on the street occaisionally. You think 1.32 is too big what should I shoot for. I'm not as knowledgeable on turbos as I would like to be enlighten me lol
If it is occasional street use, then lag is not a concern because lag is controlled with your stall. I.e, if it doesn't build boost by 60ft, then you need more stall.

Here's the idea that I'm working with on my son's current build - leave on engine and let the boost do the work at 60 ft. This will allow us to use a reasonably priced drag radial, rather need a true drag tire that can't be driven on the street. We are hoping for 475-525 crank HP NA and 800-1000 with boost - time will tell. Your build sounds similar - VERY.

My concern with your build is your cam and your motor ability to withstand 1000 HP.

In terms of turbo sizing, here's what we are doing (and this by no means implies that what we are doing is optimum ) - we're using a VS 80mm S480, but our motor is a 414 whereas yours is a 350. You have much more of a track use build than us. But I would still think that the 88mm T6 frame is going to be too large, but what do I know .
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Old 04-22-2017, 03:43 PM
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Currently the converter I have stalls at 3500-3700. So do you think I should go with a smaller turbo? I think the gt45 is a little small which is the reason for the post I think a size upgrade is necessary to get to the goal in looking for. I want to make sure to get the right turbo to accomplish that goal that will play nice with my engine. I'm not concerned about the block holding it. Just want to get a properly sized, larger than current turbo.
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