Thread: Twin charge questions

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  1. #1 Twin charge questions 
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    Hey guys. New to the forum. I came here because I'm planning to build an old ('61-'93) Pontiac 4 cylinder using an M90. I already have an M90 to play with (porting, pulleys, etc to do yet) but I've been reading up on twin charging. If I understand it correctly, you are using the supercharger in it's stock location, using it for it's low end response capabilities, but running a turbo into the blower. I think I have a handle on all of that. My installation is completely custom. The M90 will set on a custom plate mounted off the side of the 4 cylinder, which means it can set in any installed location within the engine compartment. Owing only to a belt drive connection.

    Here's my question. Has anyone ever used the blower to drive the turbo?

    I understand that what you are doing in a normal twin charge system is using the low rpm response of the blower and then using a turbo with much more potential air flow for higher rpms and power. But then the blower eventually becomes a restriction. I saw mention using the internal bypass before the rotors to open a larger pathway thru blower, which has got to help a lot under turbo boost.

    My thought is to drive the M90 into the turbo to spin that thinking that it may give the turbo some spin up right at idle and just off idle. Then the turbo can go thru an intercooler and directly into the motor. But my questions are, can the M90 develop enough pressure/flow to properly spin the turbo at low RPM (off Idle) to make any pressure for low rpm response, and conversely, can it make enough pressure/flow to spin the turbo up at mid and high rpms?

    I have no info to go on that would tell me whether the blower can do this or how much pressure/flow is required to do all of this. I was just brainstorming this as the supercharger can heat the air as much as it wants, it will not hurt the turbo. What little heat from the supercharger will be so much less than the exhaust running thru it and heating everything in the engine compartment. The turbo will still heat the air from the compressing, so I would still use an intercooler. The exhaust system is completely free of any restrictions but you will still have the drag from the supercharger.

    Again it would be whether the supercharger can flow enough to spin the turbo up to make any appreciable boost? Can the blower make more pressure down low than the cars exhaust?

    I hope I explained this right. It's just a brainstorming question, as I may end up doing a single turbo and be done with it. But that old Pontiac 3.3 liter 4 cylinder is half of a 389 so it can run some pretty big porting/valves and a pretty big cam, so it will be lacking low end grunt. I thought the regular twin charging system would fit that bill. The supercharger spinning the turbo is just another design off of that.

    Thank for listening guys. I appreciate all the experience in this forum.

    Mark L
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  2. #2 Re: Twin charge questions 
    Killa Bee Scottydoggs's Avatar
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    iirc theres 3 members who are or were twin charged. you'll have better luck being your trans wont let go on you like these fwd tranny do with all the extra power.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  3. #3 Re: Twin charge questions 
    Killa Bee Scottydoggs's Avatar
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    how it looks on a grand prix.



    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  4. #4 Re: Twin charge questions 
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    I saw that pic on this Turbo section while I was looking into twin charging. Got a good look at it. Looks like the system can move quite a bit of air/flow. Are the higher HP builds bypassing the supercharger in some way or are they running all of the turbo flow thru the normal charger?
    Thanks for the pic Scotty.

    Mark L
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  5. #5 Re: Twin charge questions 
    Florida Tuner Z34Phoenix's Avatar
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    The sc's boost bypass valve will open when the turbo builds boost. It is designed to open at low load when the pressure after the blower is lower then entering. On a stock sc'ed engine this would be vac. In twin-charge this valve (bbv) will open both at idle and when the turbo is making more boost then the sc.

    the idea of using the sc to just spin the turbo is horribly inefficient. You would be better off finding a novi sc or other cerntrifical sc. Using a roots blower to generat pressure and then use that pressure to turn a turbin introduces two areas to loose energy. There is no good way to connect boost from the sc to the exhaust so that both feed the turbo. A properly sized turbo will spool up fine and generate great mid to upper rpm power. I have not looked into twin turbo setups where a smaller turbo is used to spool up the bigger one, but this may be a better option for you.

    The main issues with twin charge is:
    -financial investment in two forms of boost.
    -will need an air to air inter cooler for the turbo and air to water for the sc. Or possibly air to water for the turbo as well. A big enough heat exchanger and pump to cool the heat generated by both.
    - the extra weight added by having both systems.

    in most cases more power can be had by just a proper sized turbo then with twincharging.

    96 Z34 (RIP LQ1 14.81@92.3) L36 Swap 14.9@91.5 www.cardomain.com/id/z34phoenix
    Topswap: P&P All,Si Valves,L76's,LW Pushrods,SD's,DHP PT PB 13.91@99.8
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  6. #6 Re: Twin charge questions 
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    Yeah, I was suspicious of the blowers ability to spool a turbo. Just though I'd throw it out there. I'm a old big block guy and I've been used to big low end grunt. I don't want this 4 cylinder to be a full on flat liner off idle or really un responsive under normal driving conditions. Even if it has great higher rpm power, I want it to be a nice street car. The automatic will help it if it is a pooch but I'd rather engineer a way around it first. I will probably build the engine capable of anything I can throw at but start it out with the blower first. Choose a car to use it in, install it, and get all the new car bugs figured out. Then start pushing it farther, whether that be a blower turbo combo or just a proper turbo alone. Time will tell. Thanks for your input guys, it is much appreciated.

    Mark L
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  7. #7 Re: Twin charge questions 
    GTP Level Member danomite02's Avatar
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    http://s1158.photobucket.com/user/da...N0748.mp4.html

    horribly inefficient. 70mm turbo.
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  8. #8 Re: Twin charge questions 
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    Was that a vid of a turbo blowing through an M90 or was it an M90, and not the exhaust, spooling the turbo? Just a 5 second vid showing a boost gauge hitting 17 psi does not help me. I'm sure blowing through the M90 plus a possible bypass to help is not a problem. If you are saying that video was the M90 spooling the turbo alone, then I have to rethink what I just said. My guess is, the video is showing an exhaust driven turbo blowing through the M90. Through the M90 makes the system more efficient/capable, not the blower more efficient/capable. I'm trying to learn here so I ask for more info.
    Also, in the video, you are already cruising along at a nice speed, maybe 25 mph? The exhaust is already spooling the turbo somewhat so you'll have a head start spooling it to full boost. Do you have a video of it boosting off idle? My turbo charged 462 in my Trans Am did not spool really well off idle like a smaller turbo would have, but at cruise it was instant. This is a ride along video of it on an on ramp. It was probably 20 miles per hour but in first gear so it was probably 2500 rpm.




    You can hear that the boost virtually instantaneous. This is the TA on a Mustang dyno. There are four cars on the vid, mine is the last four runs. The title at the start of my TA's runs was incorrect. That was at 10 psi not 15, with the second and third at 12 psi, the last at 15. The last run at 15 was 886.8 RWHP. The audio and visual is not in sync on the last two runs??? All runs were from 3000 to 6000. You can hear the car accelerate faster with each additional PSI. First run to last run. My runs start at 5:10 on the video.

    http://videos.streetfire.net/video/FAT-DYNO-DAY_643621.htm

    You can see the boost was instant when I nailed it. But it was not very quick at the strip. I easily lost a second to spool at the strip. It seemed to take for ever for the turbo to spool up. Once it did it, I was skating all the way down the strip. Wished I had a vid of that but I only had my wife with me. No one to video it.
    danomite02, if that is your car can you tell me more about it? I'd like to know your combination. Do you use a BOV? I didn't hear one after you closed the throttle.

    Mark L

    Last edited by Marks63Catalina; 12-23-2013 at 08:48 AM.
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  9. #9 Re: Twin charge questions 
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    As far as I know he twin charged. Here is the link to his ride thread.
    http://www.grandprixforums.net/showthread.php?t=78251

    Sent from my XT1080 using Tapatalk
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  10. #10 Re: Twin charge questions 
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    Damn that hot air turbo feeding the blower... that's a recipe for boom.
    If you're gonna do it, make sure you intercool the turbo and the blower!
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  11. #11 Re: Twin charge questions 
    GTP Level Member danomite02's Avatar
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    i think i misunderstood your intent. Yeah my car is the "traditional LOL" twincharged. not the m90 directly feeding the turbo. I dont have an idle to boost vid for ya currently.
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  12. #12 Re: Twin charge questions 
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    I just got done reading your old thread. But no updates for two months? How did it turn out? Sounds like you were making steady progress until the chain broke?

    Mark L
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  13. #13 Re: Twin charge questions 
    GTP Level Member danomite02's Avatar
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    Yeah she has been sitting since the timing chain let go. As soon as im done fixing up my new DD ill be diving into the pontiac. Priorities LOL. Gotta pull the heads and see what kind of damage has occured, and go from there....
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  14. #14 Re: Twin charge questions 
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    I hope all is well in there. Will be looking in when you get it up and running again. In the mean time, have a Very Merry Christmas. Maybe Santa will bring a fully built short block, heh. I think I'm gettin' the ol' chunk a coal again!!! LOL.

    Merry Christmas to everyone else too. Have a great holiday.

    Mark L
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  15. #15 Re: Twin charge questions 
    GXP Level Member darkhorizon's Avatar
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    No need to intercool both normally... The blower basically turns off due to the physics of a positive displacement blower when the turbo starts making positive pressure. The natural bypass valve in the M90 works to help keep the pressure equal on the in and the out of the blower.. some make it bigger. Also turbos run on heat.

    Also, what 4cyl are you building to 700hp+?
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  16. #16 Re: Twin charge questions 
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    I'm an old time Pontiac nut. Pontiac made a 194.5 ci 4 cylinder back in '61 to '63. It is cast as half of a 389 engine.





    It uses a special 180 degree crank otherwise it uses all of the V8 parts. Rods, pistons, head etc etc. Turbocharged they can make a lot of power. I plan to build the engine to withstand over 700 hp , then use an M90 blower at first for low end and off idle response. Then look into a turbo to blow thru the blower. If I can't reach my HP goal that way I'll pull the blower and go straight turbo. I want to drop this into a mid '80's Vette or a third Gen Firebird. Prefer a GTA. But if I can score a good '89 -'91 6 speed Vette, that would be my choice. If I'm forced to go straight turbo then I'll change over to an automatic for spooling.

    The legendary Mickey Thompson played around with these motors way, way back in the day. He set many salt flats records, some still stand today.
    With the availability of many various aftermarket performance heads now, the potential for big horsepower had never been better. They are heavy but an aluminum headed 4 cylinder wills till be lighter than an aluminum Chevy small block. Plus, with the drivers side cylinder bank completely missing, it opens up all kinds of room to hang blowers and turbos, or both. It's something I've been contemplating ever since the '70's. Now I'd like to take a shot at it.

    I'm a firm believer in you can never cool the intake charge too much.
    This is a pic of the engine in the Trans Am I posted earlier in the vid.



    I used one air to water intercooler and made 1065 HP but the intake temps were climbing. This is my current project. Twin intercooled twin turbos.




    I'm running an intercooler of that same size per turbo. Plus the twin 750 blow thrus on E85 themselves impart a small natural intercooling effect by way of their operation. Turbos run on heat but the engine intake does not need nor like it. Anywho, that's my side project. It's taking a back set to my twin turbo build but I'm sneaking it in along side it. Doing what I can when I can.
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  17. #17 Re: Twin charge questions 
    GXP Level Member Turbocharged400sbc's Avatar
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    oh how i love the oddball stuffs

    but i dont see the m90 being a good fit with a build for that power unless your wanting the extra oddball ontop of the vintage oddball

    m90 is a mechanical vampire
    ~James~ Psychotic Gearhead
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  18. #18 Re: Twin charge questions 
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    Yes I'm starting to see that it may not be the end all piece. I might port it out and sell it off to a 3800 owner for an upgrade. I have a friend with a 4-71. Maybe I can persuade him to give that up?? Probably not. He's had it for along time. I have much more turbo experience anyway so I will probably go right into that kind of power adder right off the bat. But I wanted to try to make a blower work for the low end response. Although many may argue, a turbo system is still the easiest to build since you can place it virtually anywhere. Just have to pipe it. The blower requires more refined mods for the drive unit. And it does restrict it's placement to some degree. Plus the turbo has no RPM limits like a mechanical blower does. Smaller turbos are easier to pick up form others that are up grading too. Damn, I hate when I talk myself out of something. It means I have to admit to myself that I'm wrong. LOL.

    "Mechanical Vampire", love that statement.


    Mark L
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  19. #19 Re: Twin charge questions 
    GTP Level Member danomite02's Avatar
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    errrhhhmahgahdd more pics please. Looks like some sick builds!!!
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  20. #20 Re: Twin charge questions 
    GrandPrix Junkie Sandman's Avatar
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    subbing because this has peaked my curiousity
    05 Saab 9-2X Linear (Saabaru)
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    Quote Originally Posted by TLSheff View Post
    You said "I'm done with it"... car says "Oh, really? *trollface*"
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