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Forum nameTurbo/Nitrous Tech
Topic subjectRE: Detonation..Lets make this a good topic to discuss, as its a very important one
Topic URLhttp://forums.2gnt.com/dcboard.php?az=show_topic&forum=8&topic_id=105245&mesg_id=105249
105249, RE: Detonation..Lets make this a good topic to discuss, as its a very important one
Posted by XtremeRS, Dec-31-69 06:00 PM
Excellent info there. You are completly right about the timing with low/ high rpms. Lets take an example first of our engines without boost. Our ecu's adjust ign timing based on many factors: rpm, intake air temp, coolant temp, TPS postion, and engine load, and MaP sensor readings. A datalogger will be the most benificial tool ever IMO. Our ecu will advance timing under vacum conditons constantly. When under a minimal engine load, timing will be advanced quite a bit, up to 30+ degrees. When we punch the gas, ecu goes into open loop, and timing is pulled back to around 15 degrees, and may go up slightly (at least this is what i noticed on the datalogger). I strongly believe my episode of my destroying detonation happend in closed loop, part thottle boosting. I hit almost 10 psi in third gear at around 3500+ rpms, with 80% or slightly less throttle. Then I heard the nasty rattling. Then i came to a stop light, and was smoking from the hood out the breather catch can filter i have installed. Why did this happen? In closed loop, the ecu will advance timing to where it gets the most power, and the least amount of emissions (adjusts the A/F ratio to stoich). I think closed loop part throttle boosting is a major concern, as our ecu's don't KNOW we are boosting! Even more improtant for spark retard in this situation. IMO, it will be VERY hard to tell how much timing should be advanced or retarded with rpm alone, as engine load is the key factor to how its done by the ecu. WOT boosting is much easier to come up with, as we can do this with units like the Crane or MSD. Retarding with rpm will most def hurt power over all rpm ranges if used that way. Retarding with boost only is a better way to go IMO, for better power production. Thats what is so nice about factory turbo charged cars. Their ecu's can read boost, and adjust the timing for the load, knock amount, and boost. We need an aftermarket device to simulate this. But now, WE have to figure out how much timing, when to retard, and with how much boost. As rpm increases, the engine load decreases,which leads me to believe most of our engine damage happens at a lower rpm, where timing is the most advanced,with the greatest load, with higher boost. There will be more load in different gears, at diff rpms also. Example, there will be more load at 2000 rpm's in fifth, then at 2000 rpm's in third. Same is true for WOT runs. You will have more engine load at WOT in 5th gear, than at WOT in 4th gear. I noticed this just by reading my o2 voltages on WOT runs. I got .98 v in second gear, and by WOT in 5th gear, i was around .92 v. My fuel pressures were rock steady and at the same psi in all gears. Increased engine load makes the car run hotter, and leaner, because more load needs more fuel. I only wish there was a way to tune our A/F ratios at WOT to engine load, to get a perfect .93v in every gear. At least start out leaner in a lower gear, and then richen it up for higher gears, exactly opposite of what happens now. To me, it just seems that we should not part throttle boost in closed loop, without timing retard, past 5 or 6 psi. WOT boosting, not going over 7 or 8 psi with out minor retard also. How much, well, thats what we need to figure out, to make the max HP we can anyway, without detonating. Some of the dyno numbers posted here, IMO, have been rather low. Esp with the guys running 10 + psi with rpm, and linear boost timing retard units. And also, i am basing my theories and numbers here running stock 9.6:1 comp ratio. Lower comp ratios *should* let us run a little more boost without any retard. Another thing that will make it harder to ignition tune is the A/F ratio. Richer A/F will have a tendancy to detonate less, as leaner A/F can detonate with greater possibility. This leaves a big window as to how much timing needs to be retarded. We need to find the *best* A/F ratio to start with, then tune the igniton retard. They both go hand-in-hand..

I am searching hard for someone with a J&S Safeguard..no luck yet.. Their input and HP numbers with and without it would be perfect. I do plan on getting one of these, and hopefully, if funds permit, i will dyno tune the car at like 9 or 10 psi, with, and without the J&S. I'm sure some interesting HP numbers will result. If i had the 600 bucks, i'd do it right now, on the stock internals.
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