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Thread: Theory crafting new projects

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    Hybrid booster Turbo Mopar Contributor
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    Theory crafting new projects

    I have a few new projects in store for the next year or two that I'm going to do and thought it would be good to get some ideas from the community on how they might go about doing them. I do a lot of "theory crafting", as video gamers say, in my head about how I might do a certain project but I’ve learned from other projects that I’ve done like the a/c cooled water to air intercooler and variable valve timing setup that it saves me time and gives me a lot of alternatives if I post ideas before I jump in and start doing them myself. So to start this off I’m going to list a couple of things that I have to do this summer to my wife’s car and I will list what the finished product has to be capable of then maybe you all can chime in and let me know what ways you might go about achieving the necessary end goal. If this goes well then I have a couple more ideas that are really far out there even for me that I will need input on.


    First up is the wife’s car. Since I have been working on the Omni for the last two years she has been after me to build her a car that in her words “has some passing power”. We have ridiculously few passing straights here and they are short to boot. So if you want to get around a car or two with a normally powered car you must use the “sling shot maneuver” by getting a run in the curve before the straight and hope nothing is coming in order to pass someone that is content to run 40 or 45 mph the whole 30 miles of back roads that she travels each day to work.

    A few parameters that I must work within are-

    1. It HAS to be dependable.
    2. The car must be near stock looking and sounding.
    3. She loves her 01 2.4 Sebring and wanted one just like that but with more power so I bought an 05 2.4 Sebring cheap from ebay so that’s what I have to work with.
    4. All mods have to be cheap and something that I am capable of doing. No just buying a SRT4 motor and harness and dropping it in. I have lots of time but not money lol.

    Ok so as I mentioned I have the car already. I have decided to turbo charge it for the extra power it needs. I have bought a Mexican exhaust manifold and turbocharger so that will simplify the install some. I figure an extra 40 or 50 hp will be enough so I plan on using a low boost (7 or 8 psi) non-intercooled setup. I also want it to have built-in torque limiting so little if any boost under 4000 rpm to save the A604 transmission. I prefer to keep the motor as stock as possible too and not install any aftermarket fuel control system. I’m thinking a fmu with a map clamp setup and a high pressure pump and return line. Feel free to ask any questions or suggest any ideas that will help me to get this setup done as cheaply and dependably as possible.

  2. #2
    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: Theory crafting new projects

    If it's a returnless style fuel system you will have to add an external inline fuel pump along with the FMU to bump pressure up. You'll find it's actually cheaper and FAR more adjustable to just use a $350 AEM FIC in order to use larger injectors on the stock fuel pressure, and actually tune your fuel and timing effectively.

    As for limiting boost before 4000 rpm, i suppose there are several ways to do it. Probably the easiest thing would be to fab an adjustable stopper for the wastegate puck arm and then find the point that holds it open enough that it builds no real boost at low rpms. Downside of that would be that your boost rise to your actual target boost at 4000+rpm would be pretty slow. Maybe not a big deal if you start building boost at 3000-3500 and get to ~7psi at 4000 rpm. Most of the time you will probably be downshifting to 4000+ rpm anyway so it's not like it will be a horrible long pull in one gear from 3000 to redline.

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    Re: Theory crafting new projects

    I've never really looked into piggyback controllers but that is in my price range since a good fmu was going to cost about 200 dollars anyhow. As far as the boost control goes I was thinking about making a remote mounted actuator with a cable, think cruise control diaphragm and cable only heavier duty. The diaphragm would need to be spring loaded pulling in as a normal wastegate actuator is. The diaphragm would also need to be sealed on both sides. The outer end would be hooked to boost to open the wastegate when the boost goes over 5 psi or so. The other end would be hooked to a vacuum source with a solenoid in line. Vacuum could be used to hold the wastegate open. The solenoid could be controlled by a wide open switch like a NO2 system. The A604 downshifts under most wot situations and the rpm is above 4000 then so it should be ok to dump the vacuum and close the waste gate anytime you floor the engine and build boost. This would be an on demand boost system with simple controls. Part throttle acceleration would be close to normal since a lot of exhaust would be bypassing the turbine through the open wastegate puck. No doubt it will take some adjusting to get it right hence the remote mounted wg actuator.

  4. #4
    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: Theory crafting new projects

    Remember the $200 FMU still needs a $100 inline pump and return line to be able to raise pressure beyond what the internal regulator on the pump assembly is set to. To me that's a crap deal compared to all the power that you get from an FIC and a ~$50-70 set of bigger injectors off CL like stock SRT4 stg0 or stg1 injectors.

    Well, you could either have a vacuum cruise servo just pulling in the opposite direction from the wastegate can, or you could run a dual-can wastegate and have vacuum working against the spring tension to be able to run basically no boost until you open that line back to current manifold pressure which would then let the wastegate can act 'normal'.

    Honestly, though, if you only need a range of 0-7psi, you could basically take one of our stock actuators, convert it to an adjustable rod, and then set the tension so loose that the minimum boost is basically zero. At one point i got a piece from FWDP (iirc) to convert a stock log 'big can' actuator to be adjustable. I didn't even thread the stock rod to fit the internally threaded adjuster. I just cut the stock rod, overlapped a machine screw with the right thread, and tack welded them together and threaded the adjuster onto the end of it.

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    Hybrid booster Turbo Mopar Contributor
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    Re: Theory crafting new projects

    I have seen a waste gate actuator on a Garrett that was set pretty low. It started opening at 4 psi. Even completely unhooked from the boost line it would still get blown open at 12 psi due to the backpressure against the puck. I guess something like that would work if the puck would be opened up by 7 psi or so. The only thing I really don't want is boost at lower rpms and part throttle like lugging the engine up a long hill in overdrive. If the wastegate is closed under those circumstances it could build boost below 3000 and that would really bring up the torque on a motor that normally has very little at that rpm. I feel certain the transmission is not calibrated to handle that amount of torque in overdrive at that engine rpm behind a 2.4.

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    Re: Theory crafting new projects

    im thinking if you "size" the turbine housing to the desired rpm level you would want to "build" boost that might work better, then control the amount of boost from there with the wastegate.

    piggy back fuel controller and fuel inj should be the way to go, same driveability until in boost. i really like the fmu for this, but have no experience with a non return system. one other possibility would be to add a cold start inj that kicks on at desired boost levels.

    another thing to consider is the timing map to boost level, not sure how much pressure you can run in with the stock ign map?

    and whats the plan for intercooling?

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    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: Theory crafting new projects

    A stock turbo is going to build boost from 2000 rpm if not a little earlier. The turbo is basically a fixed quantity in this situation since it's already bought and modifying the turbo itself is probably actually the least cost-effective way to affect boost rise.

    Regarding the transmission, it's not that it's not calibrated to handle torque in 4th gear, it's that the hard parts literally cannot do it. One of the clutch elements that's applied in 4th gear in a 604 is incredibly weak and there is no real 'fix' for it. Luckily for you, there is no need for a fix because 3rd gear will go faster than your wife will EVER actually drive it. Most 604 cars will do 115mph in 3rd gear before the TCM forces an early upshift and would do ~130 if they could get all the way to redline. I would encourage that you build some kind of safegaurd circuit in to either kick the trans out of 4th (by defeating/spoofing the TRS or TPS signal or torque management signal to TCM perhaps) or kill power in the event that it actually sees boost in 4th gear.

    But, by simply making the turbo spool slowly enough that it does not build boost until 3000 rpm, you should have that problem mostly covered as well, since 3000 rpm in 4th gear is fast enough (75+mph) that a typical non-car-enthusiast person will not want to accelerate hard beyond that speed anyway.

    I still think the simplest solution is to build an adjustable stopper for the wastegate arm and then fiddle with it until you cant get real boost until 4k rpm. Your wife will almost certainly never hit 4000 rpm in 4th gear(90+mph) , and yet 4000 rpm at any 'normal' road speed is just a downshift away.

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    Re: Theory crafting new projects

    i was unsure if the turbo was unboltable from the exhaust manifold, or what brand, bolt pattern or size the turbo is? i "thought" they were some sort of t3 or mistu style turbo. i thought that there would be some sort of options for that? and basically getting the turbo to "lag" by wastegate is usually backwards of what most people are trying to do.

    will the turbo always lag to the 4k plus desired rpms or will the turbo just always lag? if there is always a percent of exhaust bypassing the turbine, will it affect the transient response? basically when you want to "pass" in 2nd or 3rd gear will the turbos response suffer?

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    Re: Theory crafting new projects

    Quote Originally Posted by Vigo View Post
    Regarding the transmission, it's not that it's not calibrated to handle torque in 4th gear, it's that the hard parts literally cannot do it. One of the clutch elements that's applied in 4th gear in a 604 is incredibly weak and there is no real 'fix' for it. Luckily for you, there is no need for a fix because 3rd gear will go faster than your wife will EVER actually drive it. Most 604 cars will do 115mph in 3rd gear before the TCM forces an early upshift and would do ~130 if they could get all the way to redline. I would encourage that you build some kind of safegaurd circuit in to either kick the trans out of 4th (by defeating/spoofing the TRS or TPS signal or torque management signal to TCM perhaps) or kill power in the event that it actually sees boost in 4th gear.
    I've had my 300m to the speed limiter 110 in 3rd gear. Must have been around 5k rpms or so.

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    Re: Theory crafting new projects

    Good idea to disable boost altogether while its in over drive. So I might just hook into the wire that commands the 2-4 band to apply and the Overdrive clutch to apply and when both of them are on then I will pull the wastegate open. Nice analog system that I can fine tune as I want. So along with the wide open throttle switch I should be able to open the wastgate under all conditions I don't want boost on the motor and it wont cost much at all to build. The turbo is a t3 so it will spool fairly quickly on this 24 valve motor I think. I feel that if I get the control switches setup like I want them the car should have boost on demand just when its needed. Wide open throttle and downshifted into second or third gear and the boost will probably be waiting on you. That's what I'm working for anyhow.

  11. #11
    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: Theory crafting new projects

    There are no bands in a 604 but you certainly can interrupt some of the circuits to the solenoid pack. Problem there is that once the TCM detects certain fault conditions it will dump you into a 2nd-gear-only limp mode and not return to normal until you turn the key off and back on again.

    A better way to disable 4th gear would be to spoof the TRS (trans range sensor) signal to make it think you put the shifter in the 3 position. But, maybe the better solution altogether is not to lock it out of 4th at all but to build a system that pulls the wastegate open whenever it IS in 4th, as you mentioned.

    I've had my 300m to the speed limiter 110 in 3rd gear. Must have been around 5k rpms or so.
    My old modded 3.5 intrepid forced a 3-4 upshift at 5500 rpm and ~116 mph. It had an autostick TCM and un-limited PCM swapped in. Non autostick cars force a 3-4 upshift at 4800 rpm and have a 105-110mph limiter.

    If it had been able to go to 6500 in 3rd it would have done ~137. I took it up past 130 in 4th gear and a couple days later my 4th gear started slipping at low load. The car had 120k. I rebuilt it myself and then sold the car a while later. If i'd been able to make it ride 3rd to redline back then i think the car could have gone ~145 mph. It wasn't that modded, either. I modded 2 52mm TBs to fit it, did a cowl intake, and had smallish true duals from the downpipes back. When i rebuilt the trans i put in a ~3300rpm stall converter and '2.7 gears'. When it ran right it would run with 14 second cars.

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    Re: Theory crafting new projects

    What about finding a PTGT PCM? Can that even work in the cloud cars? I know there's all kinds of wonky crap with the instrument cluster and the steering column.

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    Re: Theory crafting new projects

    I don't know why I said 2-4 band, must have had a brain cloud. I've rebuilt dozens of the 604's. I should have said 2-4 clutch. She will never hold it to over a hundred in 3rd so I'm sure it wont be a problem. I was thinking that if I used something like a switching transistor to signal off the 2-4 clutch solenoid and the overdrive solenoid without adding enough resistance to the circuits so the computer wouldn't go into limp mode then I could use those signals to control a relay that would switch my vacuum pulloff on the wastegate thereby denying or at least reducing boost only in 4th. It may not even be a problem considering the transmission downshifts pretty much anytime you accelerate very hard and if I put a wot switch on it so that I have boost only when its pinned then I'm sure it will never see boost in 4th with her driving or me for that matter lol.

  14. #14
    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: Theory crafting new projects

    Cool man, cant wait to see what you come up with. I'm really impressed with your other project and based on what kind of experience and knowledge you have im 100% sure you can get this whole idea to work. Post lots of pics!

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    Re: Theory crafting new projects

    What about a boost solenoid that controls one canister that keeps the flapper open until 4000 rpms and then a boost kill integrated for 4th gear issues? Another canister for standard boost. That second canister could also be a completely seperate external wastegate.

    Modifying the turbo would be free. All you seem to want is to let the transmission downshift before boost kicks in. Just progressively hog out the turbine housing volute until you get the desired shift without boost. At 4000 rpms spooling quickly won't be a problem. This will cause the car to not perform like a proper small turbo car but its easy. The car will act like a big turbo car that doesn't make up for the smaller powerband with a huge peak hp. Peak HP would probably be pretty decent. If your car doesn't shift cause of some aggressive part throttle driving, I can't say what would happen. I have a slight concern that the compressor wheel might not be able to keep up with rising engine rpms since there is a lot less shaft torque available but thats just theory crafting :P There is probably still excess torque available to the turbine shaft and your wastegate will still need to control boost. Bigger turbo would be the easy path where you know the compressor wheel will put in the work required.

    4000 to 4800 rpms seems like an odd powerband to achieve btwj if you do it with electronic/mechanical tricks. I don't know if that will do what you want when it comes to passing cars. . Modifying the turbo would allow you to only lag as long as needed to downshift. You don't want a car that accellerates quickly from 40 to 48 mph to pass someone.... Seems like you are going to have to deal with a shift during your pass.
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    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: Theory crafting new projects

    Well assuming a few things (25.5" tire diameter, 3.9:1 diff ratio) 4800 in 3rd is still 93 mph. Most wives would be done with their passing by that speed.

    6500 in 2nd is actually 81 mph so if you start from a lower speed (she probably wouldnt pass someone who was already doing 70 on a 2-lane..) you would actually be in 2nd for the pass.

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    Re: Theory crafting new projects

    A 75 shot of N2O sounds easier if used for passing manuevers...

    Granted, that's nowhere near as fun to mess around with as fabbing a turbo setup.
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    Re: Theory crafting new projects

    It seems the average speed of most people (or at least the first car in a string) around here is about 40 mph. The Sebring does downshift to second at that speed. I asked her to check today on her way to work or back at what speed the transmission shifts into third but she never had the chance as she was following several cars all the way to and from work and could not pass anywhere. Maybe tomorrow I will find out. I'm sure that having boost in 2nd and 3rd will be the perfect ticket for what she wants the car to do. As far as nitrous goes I'm just getting setup with a 200 lb lease tank but that is for my Omni and a "near future race car". I hope to sell enough locally to get the nitrous free for my use. If she were to get addicted to it on her car too then I'd be losing money lol.

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    Re: Theory crafting new projects

    I tried out her 01 today since it was the first day the roads were clear. I will downshift into 2nd gear from 62 mph or anything less. It shifts out of 2nd at 68 which is 6000 on the tach. So if I get boost in 2nd and 3rd that will be enough. It wont be needed in o/d at all for her needs.

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    Re: Theory crafting new projects

    Ive been reading up on the AEM FIC and it seems a lot of people have problems setting them up. Anyone on here have any experience with them?

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