Need Tech Help - BTF, TJ, etc
Thread Starter
Safety Car
Joined: Apr 2001
Posts: 3,525
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From: Houston TX
Need Tech Help - BTF, TJ, etc
I thought maybe BTF, TJWong or others might be able to assist.
I am helping set-up a fully built 3-rotor (Japanese only) with a large turbo application. All of this is custom. Due to the fact that the cylinder head has two seperate intake tracts per rotor, the intake has been fabbed to allow the use of a single small TB (Chrysler 1.8L TB) and the larger entries have a large TB (LS1 TB).
My issue is that the small TB still retains the mechanical cable to open, while I am trying to operate the second TB via DBW (drive by wire). The idea is to have the second TB open based on TPS (from the first TB (0-5V analog signal) and the MAP reading. I was trying to get the second TB to begin opening based on 108kPa and 2.5V TPS. The second TB would progressively open by reference from the TPS signal and 160kPa MAP signal. The second TB DBW requires a digital signal to actuate.
When I look at FAST, BS3, Haltech, they have simple signal out that would actuate an external device, but I am not sure what I would need to do to accurately accuate the digital driver on the LS1 TB from the analog output from the aftermarket ECMs.
I know this is way out there, but any info would be most helpful.
Thanks in advance,
Aaron
I am helping set-up a fully built 3-rotor (Japanese only) with a large turbo application. All of this is custom. Due to the fact that the cylinder head has two seperate intake tracts per rotor, the intake has been fabbed to allow the use of a single small TB (Chrysler 1.8L TB) and the larger entries have a large TB (LS1 TB).
My issue is that the small TB still retains the mechanical cable to open, while I am trying to operate the second TB via DBW (drive by wire). The idea is to have the second TB open based on TPS (from the first TB (0-5V analog signal) and the MAP reading. I was trying to get the second TB to begin opening based on 108kPa and 2.5V TPS. The second TB would progressively open by reference from the TPS signal and 160kPa MAP signal. The second TB DBW requires a digital signal to actuate.
When I look at FAST, BS3, Haltech, they have simple signal out that would actuate an external device, but I am not sure what I would need to do to accurately accuate the digital driver on the LS1 TB from the analog output from the aftermarket ECMs.
I know this is way out there, but any info would be most helpful.
Thanks in advance,
Aaron
Drifting
Joined: Nov 2003
Posts: 1,637
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From: Honeoye Ny
hmm, I f Im not mistaken man the ls1 system uses a pwm system to operate a electric motor that fights a spring. Or is it current modulated?
either way you could setup an output that was PWM (like an injector driver) The other option is a seperate circuit that has a PWM driver on it and functions according to rpm and map. You would use the spare output on your BS3,halltech etc for activation of the circuit.
yet another way I could think of doing it is using a greddy emainge ultimate ( I install like 3 a month) and use the sub injector outputs to control the secondary throttle.
the only possible hiccup would be the current demand, possible requiring a heavier driver.
either way you could setup an output that was PWM (like an injector driver) The other option is a seperate circuit that has a PWM driver on it and functions according to rpm and map. You would use the spare output on your BS3,halltech etc for activation of the circuit.
yet another way I could think of doing it is using a greddy emainge ultimate ( I install like 3 a month) and use the sub injector outputs to control the secondary throttle.
the only possible hiccup would be the current demand, possible requiring a heavier driver.
Melting Slicks
Joined: Jun 1999
Posts: 2,872
Likes: 3
From: Wilmington NC
Andy,
It is possible.. but, that is one hell of a risky thing to try and do by yourself and could be a liability if something went wrong which is exactly what was happening with the early DBW vettes... if that DBW TB malfunctioned for some reason it could get someone in a bad situation in a hurry. if the main throttle is cable opened, and you are wanting to operate the larger TB in sequence I would look into more of a dual quad setup where once the smaller TB has reached its max throw the larger TB begins to open on the same cable. this will still give you the entire opening of the first throttle body before the larger one begins to open which will yield excellent part throttle driveability and still give you max flow on the larger one when they put their foot in it. a spring actuated barrel would work in this application.. just something to put some thought into. throttle opening is kind of a hairy situation.. especially on a HIGH HP application.
Chris
It is possible.. but, that is one hell of a risky thing to try and do by yourself and could be a liability if something went wrong which is exactly what was happening with the early DBW vettes... if that DBW TB malfunctioned for some reason it could get someone in a bad situation in a hurry. if the main throttle is cable opened, and you are wanting to operate the larger TB in sequence I would look into more of a dual quad setup where once the smaller TB has reached its max throw the larger TB begins to open on the same cable. this will still give you the entire opening of the first throttle body before the larger one begins to open which will yield excellent part throttle driveability and still give you max flow on the larger one when they put their foot in it. a spring actuated barrel would work in this application.. just something to put some thought into. throttle opening is kind of a hairy situation.. especially on a HIGH HP application.
Chris
Drifting
Joined: Nov 2003
Posts: 1,637
Likes: 2
From: Honeoye Ny
it's fail-safe though. If voltage is lost it will close. However if your driver fries and somehow fails-high it would open it up. But I agree, a cable or pnuematic opereated seconday is a far easier solution.
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Aaron I am not sure if you even want to go there. I am fighting a TAC issue right now in a 40 Ford Deluxe street rod that has a 427 small block with Hilborn stack style EFI, it is using a GM MEFI with a Corvette TAC module and a C5 LS1 TB. For some time now on occasion it drops out, for some reason the TAC module resets and he looses the throttle, it just goes to fail safe and the spring in the TB returns it to a safe engine speed. It has been a pain in the **** I can tell you that because I have yet to find the problem causing this.
Thread Starter
Safety Car
Joined: Apr 2001
Posts: 3,525
Likes: 2
From: Houston TX
Originally Posted by Baldturbofreak
hmm, I f Im not mistaken man the ls1 system uses a pwm system to operate a electric motor that fights a spring. Or is it current modulated?
either way you could setup an output that was PWM (like an injector driver) The other option is a seperate circuit that has a PWM driver on it and functions according to rpm and map. You would use the spare output on your BS3,halltech etc for activation of the circuit.
yet another way I could think of doing it is using a greddy emainge ultimate ( I install like 3 a month) and use the sub injector outputs to control the secondary throttle.
the only possible hiccup would be the current demand, possible requiring a heavier driver.
either way you could setup an output that was PWM (like an injector driver) The other option is a seperate circuit that has a PWM driver on it and functions according to rpm and map. You would use the spare output on your BS3,halltech etc for activation of the circuit.
yet another way I could think of doing it is using a greddy emainge ultimate ( I install like 3 a month) and use the sub injector outputs to control the secondary throttle.
the only possible hiccup would be the current demand, possible requiring a heavier driver.
thanks for the response. It has been about 15 years since I went through college EE classes, I am a ChE/MBA). Could you detail exactly the thought process on the seperate driver that drives the PWM driver, and how that could be integrated into the avtermarket ECM set-up, which is now looking like Haltech.
Thanks again to all who returned with comments.
Aaron
Safety Car
Joined: May 2003
Posts: 4,283
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From: Houston Texas
Stock that motor made about 300 hp with 6psi. Peter Farrell who has done several conversions into the 93-95 2 rotor RX7 used the Electromotive Tech 1 with 6 ignition coils. With port work and stock twin turbo, they were able to get 500hp with 12psi. Just remember when building the exhaust that these motors will burn the packing out of a muffler so you might want to use a chambered one. I am guessing after reading your post again that you don't have the stock intake setup which PFS used.
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Arron, you maybe able to do this using a GM/Delphi MEFI controller, a C5 pedal assembly, and a TAC module from a C5. You could setup the throttle and linearize it using a table within the MEFI programming to make the secondary TB follow any curve you desire. How ever it would not be cheap to do this. But it would work as the MEFI can control in batch fire mode and it can use a 2 or 3 bar MAP sensor for boost enrichment. Also you can easily integrate a GM HEI EST style module into the ignition and set it up that way.
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Melting Slicks
Joined: Jan 2002
Posts: 3,293
Likes: 79
From: Jackson MI
Is there any reason that you could not have the second tb open on WOT only?? You were trying to get it to open with 108kPa and 2.5V TPS which is a few psi and half throttle? Why not put a WOT switch in there like on a nitrous system and when it goes flip the relay that will controll the proper voltage to the TB, bam it opens and you're good to go.
I'm sure if you are using any kind of after market ECM system they will have a configureable on/off output like that. My Accel Gen7 has two of them with configureable tables depending on map reading, rpm, and throttle possition.
By the way those 2.0L rotaries really rock! It should be a great motor when its all done and you crank the boost.
I'm sure if you are using any kind of after market ECM system they will have a configureable on/off output like that. My Accel Gen7 has two of them with configureable tables depending on map reading, rpm, and throttle possition.
By the way those 2.0L rotaries really rock! It should be a great motor when its all done and you crank the boost.
Thread Starter
Safety Car
Joined: Apr 2001
Posts: 3,525
Likes: 2
From: Houston TX
Guys,
Thanks for all of the words of wisdom and encouragement. This motor is a 3 rotor (basically an additiaonal 1/2 motor attached to a standard 2 rotor engine). It was only available in Japan, and required considerable work to get it to fit in the std RX7 chassis. That is all behind us now.
We can concentrate on the twin TBs. I do still like the idea of electronic control of the secondary TB, so I will continue to ask questions on that front. This package should run on 20+ psi boost, and the 108kPa indicated is indicative of no boost, no vacuum (basically atmospheric psi).
More input please.
Aaron
Thanks for all of the words of wisdom and encouragement. This motor is a 3 rotor (basically an additiaonal 1/2 motor attached to a standard 2 rotor engine). It was only available in Japan, and required considerable work to get it to fit in the std RX7 chassis. That is all behind us now.
We can concentrate on the twin TBs. I do still like the idea of electronic control of the secondary TB, so I will continue to ask questions on that front. This package should run on 20+ psi boost, and the 108kPa indicated is indicative of no boost, no vacuum (basically atmospheric psi).
More input please.
Aaron
Drifting
Joined: Nov 2003
Posts: 1,637
Likes: 2
From: Honeoye Ny
Aaron, I will look around for the required IC but basically we can use a frequncy generator controlled by the 0-5v input (throttle) to increase the frequncy of our PWM circuit. This will accuratly control the current going to the throttle by wire. you can keep it from activating early by usiing the controlled output to provide voltage to the IC. When I get out of class tonight (10pm) I'll throw some stuff together for you in Pspice and try it out.
Thread Starter
Safety Car
Joined: Apr 2001
Posts: 3,525
Likes: 2
From: Houston TX
BTF,
That sounds great. I will patiently await your response. If we can get this to work, then this would be basically "the best of all worlds" with respect to the airflow requirements on the dedicated intake tracts.
Thanks for helping me out on this project. This forum is a great place.
Aaron
That sounds great. I will patiently await your response. If we can get this to work, then this would be basically "the best of all worlds" with respect to the airflow requirements on the dedicated intake tracts.
Thanks for helping me out on this project. This forum is a great place.
Aaron
Safety Car
Joined: May 2003
Posts: 4,283
Likes: 0
From: Houston Texas
Aaron did you guys do any porting to the housings? Also did you have to change the rear housing out with one from a 13B in order to mount the transmission? With respect to ignition, the two plugs per rotor don't fire at same time, how did you address that one? Sorry for all the questions but I have had four RX7s and always wanted to do this conversion.
Drifting
Joined: Nov 2003
Posts: 1,637
Likes: 2
From: Honeoye Ny
I think I can handle this one-
The processor uses a crank trigger or something like a 36-1 or 60-2 (the minus being missing teeth) once it has "sync'd up" it knows via the time between each tooth and the count of which tooth it's on to decipher where the crank shaft position is +/-some% depending on processor speed and programming.
Then it's a simple matter of telling which of the 6 coil drivers (for c.o.p) or 3 for wasted spark when to fire, as in firing order. It will charge and spark the appropriate coil according to your timing map. But I beleive there is like 30deg or so difference judging from the cap & rotor on my 12A.
You can read much more about this on the megasquirt website, the MS-S extra code has been successfully adapted to rotories. They probably explain it better then I can.
The processor uses a crank trigger or something like a 36-1 or 60-2 (the minus being missing teeth) once it has "sync'd up" it knows via the time between each tooth and the count of which tooth it's on to decipher where the crank shaft position is +/-some% depending on processor speed and programming.
Then it's a simple matter of telling which of the 6 coil drivers (for c.o.p) or 3 for wasted spark when to fire, as in firing order. It will charge and spark the appropriate coil according to your timing map. But I beleive there is like 30deg or so difference judging from the cap & rotor on my 12A.
You can read much more about this on the megasquirt website, the MS-S extra code has been successfully adapted to rotories. They probably explain it better then I can.
Last edited by Baldturbofreak; Oct 3, 2006 at 08:50 PM.
Drifting
Joined: Nov 2003
Posts: 1,637
Likes: 2
From: Honeoye Ny
alrighty I have given this some thought and really there is two strategies.
1) We can try to use the tach signal to trigger a transistor controlling the output of a variable current source, mastered by the tps signal(or map).
This strategy would open the throttle as a function of rpm/throttle(map) position. kinda like a vacuum secondary and wpuld be totally independant. Set with potentimeters.
2)we can create a pwm driver circuit that remains at a fixed freqency and the current leg shall be fed by your spare output lead on your haltech. non-linear but simple.
what i really need at this point is some info on the drive motor. I.e. current demands, how is setup in the factory effort (LSX) to get an idea for parts that would be involved
1) We can try to use the tach signal to trigger a transistor controlling the output of a variable current source, mastered by the tps signal(or map).
This strategy would open the throttle as a function of rpm/throttle(map) position. kinda like a vacuum secondary and wpuld be totally independant. Set with potentimeters.
2)we can create a pwm driver circuit that remains at a fixed freqency and the current leg shall be fed by your spare output lead on your haltech. non-linear but simple.
what i really need at this point is some info on the drive motor. I.e. current demands, how is setup in the factory effort (LSX) to get an idea for parts that would be involved
Last edited by Baldturbofreak; Oct 11, 2006 at 07:34 PM.
Melting Slicks
Joined: Sep 2004
Posts: 3,153
Likes: 114
i dont know much abou these motors but i know they are very interesting 
what would be the advantage of running two throttle bodies??
how about haveing 1 BIG body with a custom cam on the body?? this would give you, if built right, a very ajustable throttle, but still the flw at full throttle!
thanks Chris.
what would be the advantage of running two throttle bodies??
how about haveing 1 BIG body with a custom cam on the body?? this would give you, if built right, a very ajustable throttle, but still the flw at full throttle!
thanks Chris.
