Re: Hellcat help, someone smart explain
[Re: AeroMonte]
#2551315
09/17/18 11:27 PM
09/17/18 11:27 PM
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Joined: Dec 2007
Posts: 486 IL
knyech1
mopar
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mopar
Joined: Dec 2007
Posts: 486
IL
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I am doing a Hellcat swap into a 71 Barracuda as you all know. I am using a Holley EFI computer and harness. The original blow off for the supercharger uses a Jeep throttle body that is controlled by the computer to relieve pressure back into the intake. The Holley system cannot duplicate this function. What I have worked out, and I am no engineer, is a vacuum controlled turbo blow off valve that is plumbed back to the intake just behind the engines throttle body into an extension we fabricated. Will this work or am I overlooking something? By moving the throttle body 6-8 inches farther away from the intake, will that affect anything? I've thought about this so much I am starting to second guess myself. I know one of you out there understands I hope and can explain the technical stuff for me. AeroMonte, I hate to say it but this seems like a wasted effort. While the supercharger might use the same size throttle body as a particular Jeep application, the logic is reversed. It is essentially programmed inverse of the inlet throttle body, so when the inlet tb sees ~4.8V it is completely open and when the bypass tb sees ~4.8V it is completely closed. Even the Whipple 4.5L supercharger for the Hellcat/Demon utilizes the stock bypass valve. The reason that FCA does it this way is so they can program the bypass tb to completely close at a certain throttle position to build boost when they want, and when you let off the throttle, the bypass will snap open, recirculating the compressed air. "E-actuators" are the new age of wastegate actuators are the same way. The Eaton/Magnuson/Edelbrock roots superchargers use a more simple (and less expensive) pressure pneumatic actuator with a light spring that it has to overcome. It works, but isn't programmable like the one on the Hellcat/Demon superchargers. Again, the factory system would have worked just fine.
knyech1-
'71 Sassy Grass Demon 340/904. Pump gas, 1.61 60ft, 7.439 1/8 @ 95mph, 11.824 1/4 @ 111mph
"Not too bad for a pump gas 340, full of used parts and hillbilly ported stock heads." - V.B.
'03 2500 5.9L HO 6-spd on 35's. 395hp/755ft-lb at tires.
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Re: Hellcat help, someone smart explain
[Re: AeroMonte]
#2553098
09/21/18 11:19 PM
09/21/18 11:19 PM
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Joined: Oct 2004
Posts: 68 Southern Michigan
mike_coates
member
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member
Joined: Oct 2004
Posts: 68
Southern Michigan
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The system will work if it is like you described. The vacuum source needs to come from after the inlet air TB. Vacuum is created when the throttle is closed, thus opening the bypass valve to reduce parasitic losses at idle or part throttle. It isn’t controlable like the factor e-bypass but it works well. The e-bypass allows the oem to manage boost to tailor the torque curve to their liking. With the added length in the ducting, Inlet pressure will be a little lower which will affect the vacuum response a litle on throttle closing. The long bypas duct will affect response also. The valve does act as a blow off valve. It is a bypass to reduce losses. But if it fails, the unit will have a high chance of failure. A closed throttle with a closed bypass can heat up the unit and seize it in seconds especially at high speeds. If someone is making an ecu for the hellcat, it should include the control of the bypass, IMO.
'70 Swinger 340 '91 Dakota '72 Challenger '05 Ram
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Re: Hellcat help, someone smart explain
[Re: AeroMonte]
#2553721
09/23/18 05:17 PM
09/23/18 05:17 PM
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Joined: Feb 2003
Posts: 18,582 Rust Belt, SW PA
Silver70
I Live Here
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I Live Here
Joined: Feb 2003
Posts: 18,582
Rust Belt, SW PA
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I used ms3 gold box/harnesses on all my hemi swaps. I don't know if they have them available with a program for hellcats, if not, surely they will eventually. Around 1300 for all and fully tuneable. I don't understand why people spend so much more to use a stock ecm and custom made harness of other more expensive options.
68 Road Runner, 69 Belvedere, 71 Challenger Vert 340 barracuda, 01 Ram CTD, 95 Ram, 04 Ram, 85 Daytona turbo Z 66 GTO, 06 Magnum RT AWD. 07 Ram CTD, 07 Ram
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Re: Hellcat help, someone smart explain
[Re: Silver70]
#2553856
09/23/18 10:24 PM
09/23/18 10:24 PM
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Joined: Feb 2010
Posts: 33 Northern California
B5 Classic
member
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member
Joined: Feb 2010
Posts: 33
Northern California
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In my case, I don't like all the smaller company systems that are out there where in a few years, they may not support it any more or they may even not exist. I was going to use the Dominator until Mopar came out with the Hellcrate and the ECU / wiring harness to go with it. Unlocked and fully programmable. With what's being done by guys like HemiTuner on the factory stuff, well, that's good enough for me. Keeps my car all Mopar too. The only stuff on my car that's not Mopar are my TTI headers; Baer brakes and custom Moroso oil pan. Oh, and AlterKtion front suspension. I'm and old "old school" guy, so that pleases me. I used ms3 gold box/harnesses on all my hemi swaps. I don't know if they have them available with a program for hellcats, if not, surely they will eventually. Around 1300 for all and fully tuneable. I don't understand why people spend so much more to use a stock ecm and custom made harness of other more expensive options.
Last edited by B5 Classic; 09/25/18 03:45 PM.
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Re: Hellcat help, someone smart explain
[Re: B5 Classic]
#2554298
09/25/18 12:11 AM
09/25/18 12:11 AM
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Joined: Dec 2007
Posts: 486 IL
knyech1
mopar
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mopar
Joined: Dec 2007
Posts: 486
IL
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In my case, I don't like all the smaller company systems that are out there where in a few years, they may not support it any more or they may even not exist. I was going to use the Dominator until Mopar came out with the Hellcrate and the ECU / wiring harness to go with it. Unlocked and fully programmable. With what's being done by guys like HemiTuner on the factory stuff, well, that's good enough for me. Keeps my car all Mopar too. The only stuff on my car that's not Mopar are my TTI heads; Baer brakes and custom Moroso oil pan. Oh, and AlterKtion front suspension. I'm and old "old school" guy, so that pleases me. I used ms3 gold box/harnesses on all my hemi swaps. I don't know if they have them available with a program for hellcats, if not, surely they will eventually. Around 1300 for all and fully tuneable. I don't understand why people spend so much more to use a stock ecm and custom made harness of other more expensive options. B5 Classic, MegaSquirt has been around since 2001. For a long time, that was the choice of ECU for the Drag Week guys because you could build the box yourself and build in your own features. You can make it exotic or simple, and either way it costs far less than a Holley or similar setup. There is a MASSIVE following and awesome support either from DIYAutotune or on the MS forums/groups. The support isn't getting anything but better every day. I personally use an MS2 Extra ECU and it has all the fancy stuff that Holley, FAST, FITech, Mopar, etc have. Auto tune, customizable VE and AFR tables, AE enrichment, all the bells and whistles and it cost me $750. The MS3 Gold Gold Box and Harness kit was made specifically for the Hellcat. Remember that Mopar especially has to get their 400% markup for anything they sell.
knyech1-
'71 Sassy Grass Demon 340/904. Pump gas, 1.61 60ft, 7.439 1/8 @ 95mph, 11.824 1/4 @ 111mph
"Not too bad for a pump gas 340, full of used parts and hillbilly ported stock heads." - V.B.
'03 2500 5.9L HO 6-spd on 35's. 395hp/755ft-lb at tires.
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