| LS7 in a C4 - A brain storming session |
Subject: LS7 in a C4 - A brain storming session by bogus on 2011/3/28 17:47:32 I have been fighting the good fight on what to do with the engine in my 92. Part of the problem with any upgrade is the pros/cons of the project. The con here is that the LT1 engine controllers are not getting any more common on the market, so that is a problem. They are also hard to program, with chip burns and such. So I wanted to start a brain storming discussion and get some things sorted out in my head before I progress with this project. I have gone back and forth on a SC 383 or an NA LS7 for some time. And after a lot of thought, the NA LS7 just seems more practical. The output is about the same, and the LS7 will be easier to get past CARB. First off, mechanically, the install has been sorted out. There are motor mount adaptors and all that now available. I know that Dick Guldstrand has an LSx to ZF6 adaptor, and has a sweet clutch using an hydraulic throw-out bearing. It may be the same that RAM sells, but I will find out in due course. There are others supposedly in development, but I haven't heard more on it other than that. The biggest one is this: I will have to piggyback the existing LT1 harness with the LS7 harness, to get some very specific data elements to keep the ASR working. I want the ASR and ABS to function, along with the IP and such. There is an option to use the original LS1 style mechanical throttle body on an LS7. The ASR system, when active, will close the throttle body; this act will force the PCM to retard timing. So that separate instruction is gone; rendered redundant from my estimations. The questions: 1. If you are doing a piggyback setup, only one PCM needs to power things, so if the LS7 PCM is doing the power, then the only thing that the LT1 needs is to tap into the signal line and get the result. Does this sound correct? 2. The LT1 ECM will need to be reprogrammed, because it will no long actually run the car, I don't need it to send codes back for lack of signals and stuff. All I would need from it, to keep the CCM happy is RPM, temps, TPS. AFAIK, all those sensors are still the same. 3. What about the VSS? It changed... would a signal doubler from Dakota Digital fix this? I can run the raw signal to the LT1 controller and the doubled to the LSx controller? 4. Motor mount adaptors exist. As do transmission adaptors... how do they interact? Are they a matched kit? Think about this... if the motor mount adaptors move the engine 2" forward, for example, and the trans adaptor is designed to give more space in the bell housing for the clutch, can one use the same motor mount with the ZF trans adaptor? Or does it cause the motor to move to far forward. I have been under the impression that the motor mount adaptors are more focused at the auto trans or T56 world, where fitment to the engine is not a problem. 5. I have read where the AC compressor gets in the way of the K-member. Is this true? What is the fix for this? Can the compressor be relocated? 6. I have conceptualized the dry sump moving to the battery tray on the C4. Longer hoses should'nt harm anything? Or is there a pan with left side pickups? 7. What am I missing? Some will think I am crazy to consider this conversion, but let me put it this way: The car is paid for. I have no desire to buy a new one. The cheapest used Z06 is $35k, with the associated increase in insurance and registration fees. For that matter, anyone can just "buy" a Z06, but to build one from a C4 strikes me as being different... I can get a new LS7 from GM for about $14k. I suspect that means used ones are under $10k, to be honest, I would expect half. I can't build a 383 blower motor for that money. The blower will be $5k+, the shortblock has to be strong enough, then comes the dyno tune... And heads... Time for that famous word: DISCUSS! |
