RuffTuff 95 S/C pulley

Changing the S/C pulley to a smaller size will NOT increase boost. The Lysholm Compressor on the Millenia S is capable of producing 23 psi boost. Boost is limited by the ECM to 14 psi. Information to the ECM is provided by the MAP sensor. 14 psi is the practical limit for the S engine. If boost is increased the temperature of the intake charge would increase, The dynamic charge temperature sensor would sense this and send a signal to the ECM to retard the spark, therefore negating any power increase.

Is this specific to the miller engine management system? I have a cousin who has a GTP and changed his pulley. Mind you it's not a miller engine but would the same theory apply to him?

Modern engines that use computer control would most certainly use it to limit boost on a supercharged car. It would probably use a BAC valve to let air bypass the S/C (sort Of) during high boost and under vacuum. This would not apply to turbochargers (the bypass part)but the waste gate would be controlled by the computer. It amazes me that people can be duped into buying<br>stuff that doesn't work. Did your cousin install<br>a boost gauge to check the boost before and after <br>he changed the pulley?

No my cousin only has the standard boost gauge, which is just a digital meter with no numerical markings. So you're saying that the ECU is responsible for the amount of boost? Is it correct in assuming that changing/reprogramming the ECU may lead to increased performance due to better engine management?<br><br>You seem very knowledgeable, are or were you an automotive technician?

First I must caution you not to use a smaller pulley on your S. The B rotor on the S rotates at ~6 times engine speed (35,000 rpm at 6,000 engine rpm), This is the MAXIMUM design speed of the Lysholm, The pulley from Mazda has a vibration dampener integral with the pulley. I doupt that the aftermarket pulleys have this feature<br><br>Not an auto tech just a computer tech. I have become a student of the Miller Cycle. I have purchased all the SAE papers (5) that I could find on the Miller Cycle engine and the Lysholm<br>S/C, written by Mazda and IHI engineers. I do all of the repairs and trouble shooting on my S. I have a sophisticated OBD 2 program in my computer<br>that has a router and cable to connect my car computers to my PC.

I forgot to answer the part about changing/reprogramming the ECU. IT certainly possible that a very few people could change some programming in the computer IF they had the source code, but no manufacturer will give out it's source code, they guard it carefully. They could also trick the computer into thinking it's receiving signals from various sensors when it's<br>receiving from a false source. There was an article about 8 years ago in Motor Trend in which they tested The E-Prom chip replacements for GM <br>engines, non of them yielded an appreciable increase in hp. The GM chip for the Corvette 350<br>yielded exactly the increase GM advertised.

Where did you acquire all the SAE papers and the OBD 2 program. It's an intriguing piece of equipment to have, I might add. Would you be able to post a pic of it? And how much did it cost you? Did you fabricate all the connections?

Inspector Gadget: You seem to know alot hooking up your computer and all to your car,,You have my attention Proffeser is there anything else you can share with us ???

The program is available at <a href=http://www.obd-2.com/ target=new>http://www.obd-2.com/</a><br>the cable with OBD II plug and router is available at this site. The SAE papers are 940198, 980774,938219, and 940843. they are available on the SAE ewb site.

thanx.