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Thread: Non- TM turbo sizing LS1

  1. #1
    turbo addict
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    Non- TM turbo sizing LS1

    Engine 5.7L LS1
    trans - auto 4L60E? 3500 stall
    car- 88 monte carlo 4K lbs

    ok im helping a buddy do an LS1 swap in his monte SS and we're going to be turboing it but im not sure on what turbo to use. id like to stick with a holset because they can be had fairly cheap. I was on a sizing web site and it said that the HX-35 would be good for a 5.7 but that doesnt seem right to be being that we are using them on 2.2's. so ca anyone recommend a good turbo size for a STREET CAR that sees some track time. looking for a modest 5-600 at the rear wheels which has been done at 10psi with a single turbo. but everything ive read noone likes to share what turbo they are using.

    CLIFF NOTES
    What single turbo for 4klb car that is street driven.

  2. #2
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    Re: Non- TM turbo sizing LS1

    hx is a good size turbo because of the size of the turbine housing, its an external wastegate setup so you can run a big gate to get rid of excess flow (or dual gates like my friend), and should be at the right power levels for your goals. someone is selling one in the for sale section right now for a good price.

  3. #3
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    Re: Non- TM turbo sizing LS1

    Link to "sizing website" please? How high will this engine rev?

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    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: Non- TM turbo sizing LS1

    I am insanely jealous. I really miss my Monte SS.
    Mike Marra
    1986 Plymouth Horizon GLMF "The Contraption" < entertaining sponsorship offers
    Project Log:
    http://www.turbo-mopar.com/forums/showthread.php?69708-The-Contraption-2013-14&highlight=

  5. #5
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    Re: Non- TM turbo sizing LS1

    my friend doesnt rev his z06 over 6700 rpm, its a 5.7 ls6

  6. #6
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    Re: Non- TM turbo sizing LS1

    we'd like to stay at or below 7K. and not looking to push more than 10-12 psi on the stock long block. heres a crappy pic of the car.


    any help is appreciated

    -jeff

  7. #7
    turbo addict Turbo Mopar Contributor
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    Re: Non- TM turbo sizing LS1

    Assuming non rear mount...

    I can say that gt4202's were originally a hot turbo for LS1 crowd but then eventually they all found that they make too much HP at too little boost (unless your turbo setup is just terrible). So a bunch of these were for sale on the LS1 boards the last few years. I think this is one of the reasons people don't share information these days.

    I would pick something that can move more air then a gt4202 @ 10psi (1.66 bar). I can look that up right quick.
    Last edited by Ondonti; 10-29-2009 at 02:27 AM.

  8. #8
    turbo addict Turbo Mopar Contributor
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    Re: Non- TM turbo sizing LS1

    From a quick look at turbos that Frank has mapped,
    Gt4508 - Expensive but great choice
    T80 - right in the middle of the map but its not a very high efficiency turbo. low 70%'s. For cost might be your best choice.
    T88 - I know LS1 guys are using this, higher efficiency, but probably a bit laggier

    Possibly a Borg Warner 400 ish series.

    Holset....Not sure, don't have info on the HX 52 etc sizes.

    I think 70-75mm compressor impeller sizes are just going to be too small. The "extended tip" crap is really not useful for you because you don't want to run 40psi.

    Two turbos might be cheaper and easir to fit because they you would just need to find 1 turbo that fits 2.85L, and there are a bunch of affordable ones that do.

    In my opinion I prefer a street car that doesnt go into boost super easy while driving, so i like a laggier turbo, which is what the single turbo LS1 route would be.

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  10. #10
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    Re: Non- TM turbo sizing LS1

    I'll see what I can find, I think a few WFO guys in Texas have some experience in this.

    I say just turbo the 383 that's there to learn tuning on.

    I do like this project!!!!!!
    “If the people of the nation understood our banking and monetary system, I believe there would be a revolution before tomorrow morning.” -Henry Ford

  11. #11
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    Re: Non- TM turbo sizing LS1

    I just pulled the 36K mile engine and trans off the transport truck yesterday so i dont think thats an option. the mount kit is on the way and headerflanges and pipes are on the way. I need to get a turbo so i know where i can fit the damn thing!

    the 383 is going into whatever we pick up for his wife. most likely a nova.

    -jeff

  12. #12
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    Re: Non- TM turbo sizing LS1

    Non of those are what they purport to be. You would have to get the exact GT45 model I suggested. The smaller versions (gt4594 or gt4502 won't work).

    I thought the T88 was original at first, then I read that it has a 69mm inducer so its not a T88. maybe a T70, which won't work.
    EDIT: I just remembered that Greddy sizes their turbos strangly, possibly to trick people. T88 Greddy doesnot mean T88 Garret. T67 Greddy = 20g mitsu.
    Last edited by Ondonti; 10-30-2009 at 07:38 PM.

  13. #13
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    Re: Non- TM turbo sizing LS1

    There are a bunch of the larger 4708 turbos for sale on LS1tech. THe 4508 is a smaller t4 housing turbo using the bigger wheels. Its got the smaller t4 flanges etc. The 47 is huge t6 flanges etc. Going to spool slower.
    Its going to be 1000+ for a turbo, used.

  14. #14
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    Re: Non- TM turbo sizing LS1

    damn i dont wanna spend that much. i guess ill have to do some shopping and more research to see what a cheaper alternative is going to be. thanks for all your help. its been very much apreciated.

  15. #15
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    Re: Non- TM turbo sizing LS1

    You might be able to get away with a smaller turbo, it will just make the higher rpms pump hot air into the motor as you leave the compressor map.

    You probably won't make your goals but the turbo will have a lot less lag :P

  16. #16
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    Re: Non- TM turbo sizing LS1

    even at 10 psi it will not be efficient? im not worried about the lag issue. its this guys first turbo car so he doesnt know what to expect. the less lag the better but i dont want it to be out of steam by 6k.

  17. #17
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    Re: Non- TM turbo sizing LS1

    If you want it to be happy above 6k like I also think an LS1 should, then you want the turbo sizes i suggested.

    10psi is often worse then higher boost..because of how maps are shaped. Turbos are usually designed for about 15-20psi being the middle of the map. Thats usually where the map is also widest. When you are running low or high boost, you have to be more careful about turbo choice because the map narrows.

    5psi would be even worse. Also, few turbos are built to make 5 psi on a 350ci engine. I can find turbos that love 5psi for my 3.0L pretty easy. The problem with OEM turbo setups is almost all of them start running out of breath if they came from the factory as low psi setups and also small turbos. 3000gt is an example. Stock 7psi in the early years, but with tiny turbos, power starts dropping off after 5000 rpms. So when you modifiy them to the max on stock turbos, they still cant make much more then 300awhp (at the wheels) and they start out 220awhp. MKIV Supras make about the same hp on the dyno stock (220rwhp, which is actually less power) but can make 500+whp with stock turbos. The supras are laggier and will get whooped stock for stock, and thats even with their weird sequential turbo setup. Toyota could have just put on smaller turbos but they didnt. The 3000gt also will suddenlty make power past 7k on stock heads/cams when you put a turbo on that can keep boost up at high rpms.
    the 300whp 3000gt's on stock turbos usually cant even make 10psi at 7000 rpms! Even with the wastegatess wired shut. Increasing the boost see's big boost numbers at 3000 rpms become "crap" when the party is supposed to be happening

    My car is 181 cubes, and I don't consider it super laggy with an 800whp capable turbo. It makes power out of boost and with decently high compression will still be fun to drive out of boost.

    a 346ci engine with a 1200+whp capable turbo should probably feel more responsive as long as you build a decent setup. I don't have a nice exhaust manifold setup either.
    Buy a twin scroll turbine housing (thats how the big GT series come) and keep your left and right bank exhaust separate (use a divided flange).

    A GT4202 is a 900+whp turbo....but you have to imagine using that size on a 346ci engine is like putting a 46 trim to4e on my current 3.0 setup. Its going to be great until I get near 6000 rpms and then start pumping heat.

    Another problem is that the larger turbos all seem to be swayed towards 20+psi racing cars.
    In the smaller turbo area, there are more "old" turbos from the days that 40psi boost was unheard of. This is one reason why it would be easier to match two oldschool turbos.

  18. #18
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    Re: Non- TM turbo sizing LS1

    http://www.squirrelpf.com/turbocalc/...61&map_sel7=62

    Here are some TT options. You can see how some of the turbo options like the "super 50" trim is complete garbage while a 60 trim looks pretty good even at 7000 rpms?

    I added twin t04z (my turbo) and see how well 1600whp of combined turbo fits? lol.

  19. #19
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    Re: Non- TM turbo sizing LS1

    Now if you could find out what turbo this is exactly, two of them might be cheap. This one looks pretty dang good. and when you crank it from 300hp/turbo to 400/turbo it still looks great!

    And if you bump it up to 22 pounds of boost or so, making 900hp, still 71% efficient.


    Twin 20g mitsu's is good up until 400hp each on your displacement.

    That said, I have an hx35 that I am going to single turbo my Spirit with and well, it doesn't fit very well above 6000 rpms

  20. #20
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    Re: Non- TM turbo sizing LS1

    so i was doing some math and what i figured (im new to this so give me a break) is that i need a turbo that has at least a 577 HP rating. that has a pressure ratio of 1.68. does this sound right to you?

    now heres my question. if i found a turbo that is rated for say 600 hp. it doesnt mean that its going to work for my app. right. cause your talking about 1000+ hp rated turbos and me just being happy with thoes. so whats the difference? Obviously the 1000hp turbo is going to be larger with more lag but doesnt that mean not as eff at 10-15 psi. where as the 600Hp would be. or is it all a RPM game that im overlooking when doing math?

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