compound boost with hoset turbo

[superdadsc]

I am so happy I found this site and I hope that I do not offend anyone as I drive a Thunderbird SC and my user name on the sccoa forum is superdadsc as well.

The SC is a 3.8L supercharged V6. I have just rebuilt my motor and I am looking to compound boost my car with a Holset turbo mounted in the rear. I will set the car up with a blow thru maf so the turbo will be blowing into the SC. Just like the Hellion Mustang.

I have searched a lot and came across the Hoset turbo's and it seems like everyone is playing catch up with you guy's in respect to there performance and use as a DIY project turbo.

My engine with 8 lbs of boost (back to stock pullies and underdrives with ported blower, heads etc ) equates to a 350ci motor. I am looking to add 5lbs to 7lbs from the turbo. That should bring the car to around 19lbs of boost. I will let the power fall where it may. The roots blower pulls hard but falls on its face at 4800. By keeping the blower I should have instant low end TQ and I need the turbo for the topend. The engine requires about 730cfm for 19lbs of boost.

My question is I am lost on what Hoset turbo would be good for my project. I would like to see 400 to 450 rwhp.

What do you recommend as far as who to buy the turbo from? Don't want a ebay chinese turbo or will that work?

Should I add a aftermarket wheel that I have read about? (bullseye? )

What flange setup? This turbo stuff is greek to me.

Any help would be appreciated as I have no clue about turbo's and the guy's at the SCCOA forum probably don't even know what a holset is. ( In general )

Thanks

Stephen

 

[blasterracer817]

If you only want to push 8-10 on the turbo. Id recommend a smaller turbo with better spool characteristics. Perhaps a 14b or 16g etc on a v6 they would spool crazy fast. As far as where to find them check the classifieds and if your set on a holset try the cummins forum. With a v6 I don't think you would need the bep housing because a v6 will spool it pretty fast already.

 

[LandSpeed-DSM]

If you only want to push 8-10 on the turbo. Id recommend a smaller turbo with better spool characteristics. Perhaps a 14b or 16g etc on a v6 they would spool crazy fast. As far as where to find them check the classifieds and if your set on a holset try the cummins forum. With a v6 I don't think you would need the bep housing because a v6 will spool it pretty fast already.

Please ignore this guy^

Just how in the hell do you propose a 14B is going to make 450whp? Where on the map will a 3.8l be vs a 2.0 at the mass flow required to make 450whp on a 16G? Which by the way you can count on one hand the number of people who have even done that.

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OP If you want a HOLSET, you are looking at an HX35. You may also want to research this plan further. I'll explain why..

If you have 3.8L displacement, and are only aiming for 450rwhp.. Gut the blower, use it as a plenum and run just the turbo. When you account for charge density by the way, 8psi on that blower (assuming of course you are near sea-level) does not make for a 5.7L equivalent displacement.

The turbo will be considerably more efficient and make that power at the same or less boost.

You should use the larger twinscroll 16cm housing and your displacement will require a large wastegate as that motor will be able to take in the 45+ lbs/min you need at very low boost compared to our 2.0s

Now I expect you to disagree with this and tell me that this isn't what you were looking for etc... but one thing I see that you have neglected is plotting the engine demand of your SC'd 3.8 on to a turbo's compressor map to make your flow when running such a low PR as opposed to a single running the combined PR you had in mind of ~2.3-2.4 (about 19psi at sea level)

Here's what I'm talking about using a 3582R, which was the smallest compressor I could find that would have your 8psi demand even close to the map, on the HX35 you would be even farther off into the choke.. done quick and dirty in MS Paint:

You must be logged in to view this image or video.

This should illustrate just how large a turbo you would need to do what you are proposing efficiently at such low turbo PR. You would be looking at 70+mm turbos to even approach some sort of acceptable compressor efficiency. Which would come with a considerable lag penalty.

Your 3.8s actual demand flow will fall somewhere between those two dots, more than likely almost dead center depending on actual VE.. indicating less boost is required. This will further decrease spool and provide that early torque AND top-end you are looking for.

I have a compound project in progress, so don't take this as me hating on the idea. It's just not a good fit for what you are looking to do based on what you have told us. The HX35 will light plenty fast, especially with an AMS-500 /1000 or Boost Leash type electronic boost controller.

 

[superdadsc]

Thanks for the reply. I am working so I have to sneek on and check stuff when I can. I will reread your post in depth when I have time. You are correct on your CI statement. I had it wrong. My 3.8L is like a 350 with 10lbs of boost.
0.9*1.68.232=350.32 I think with my setup and underdrives I could be at 8lbs.

At 5500 and seeing 17lbs of boost and assuming 89% volumetric effiecency it should make around 485 crank HP needing 703.25 CFM. I believe the pressure ratio target should be 1.49. Not sure though. Where would that fall on your graph?

I understand a turbo would be better. It would make more power hands down. Ultimate power isn't my goal though. It will be fast enough for me when I am complete. I am 52 and I don't need 500 plus anymore. Plus it hard to get the power to the road. I am actually thinking that w/ a turbo added I will be under 400rwhp and that is fine. I am setup with Moetes QH bienary editor so tuning should be OK> Also have 57lbs injectors and a 225 walbro FP.

I want to stay true to the cars design and keep the blower. I love the sound of the blower whine from the ported SC. Now with a turbo added I would have more sounds to listen too, the turbo whistle and the BOV. When I pass someone at WOT it should bring about some interesting looks.

I am just looking at the Holset as they seem to spool quickly and are cheap. If the project works I will upgrade the system to a Comp oiless turbo but before I shell out that kind of money the Holset seems to be looking good. A comp turbo will allow me to ditch the oil system which to me is the biggest concern for remote setups. The system goes the turbo goes.

Thanks

Stephen