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Originally Posted by Ondonti
Would you like me to quote about 20 different times I have said "dohc" motor in various threads?
Do i really need to go and post dyno sheets again?
Do I need to post 3000gt threads that are called "dohc na overrated"???
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My interest has been with the claim that the 12v 3l is "underrated"... So far I have yet to see hard proof, just a lot of speculative claims...
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There were changes to the motors but I would say the 142 and the 150 are not actual exact numbers, but arbitrary ways of showing "improvement". The difference might be correct but that doesnt mean the actual number is.
Do you think adding .45 compression adds 10hp to a 140hp car BTW????Maybe 2hp. increased timing etc on the ODBII isnt going to get you there either because james Dempsey already showed that there isnt much to gain with timing advance. He only found 5hp..........and that was on a modified engine. Doubtful the odbII 3.0 computers even contribute to more hp.
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You are talking two very different things. What Dempsey did was adjust the base spark. The computer controls the spark curve. I can very easily see changing the spark _curve_ resulting in more hp.
As I said, I have talked to a real spark calibration engineer. Any time _anything_ in the engine configuration is changed they redo their spark hook calibration maps... Where they set the production spark curve is depdent on many things including production tolerances. If they have shrunk the tolerances, they could likely push the curve closer to the theoretical best.
While I am on the subject, minor machining changes can make a big difference in engine performance... Talked to an engine calibrator who was working on the next model year of the GM 3.4L DOHC. The car was down on power and he wasn't sure why. As it happened I had a prior model year car that had been converted to the new electronics and cal set. He confirmed that my car performed as he would expect.
He was left with machining changes... Ultimately it didn't matter, because the DOHC engine was axed for that model year. (High warrenty costs and a better option)
As for OBD2, that is just a set of diagnostics. A very LARGE set of diagnostics, but by itself it doesn't buy you any peformance gains. Spent a year working on/with some of the OBD2 code for '96 model year vehicles.
Some of the learning algorithm data might be helpful for tweaking some of the calibrations on the fly.
The larger processor made more complex/accurate fueling algorithms possible... So you could have some minor gains there. Increased accuracy of the spark timing would also be possible. You could have had a stack up gains that neted a few hp.
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The 224hp dohc 2.2 chrysler will dyno 35-45whp more then a 220hp mitsu dohc v6 when both are stock........Here you have chrysler underating a motor. It doesnt even make sense in this case.........If they were rating HP like mitsu does for its 24v motors then the 2.2 dohc chrysler would be rated as making 275hp.
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I had a T3, factory hp was about right. But the engine was exhaust choked... Open the exhaust and instant power upgrade at every RPM...
TurboDodge.com 
everyone on this forum said if they had a stock 3.0 and lived close to you they would do it.
