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Do you think it would work? I was looking back at the spark retard based rev limiter I did and decided it just wasn't practical. Basically what you'd end up with is flames shooting out the exhaust instead of a good rev limiter. Which is still fun, but a good way to ruin parts at full throttle. So would setting the dwell to something super short so the coil doesn't charge work? Or is there something in the icm that will screw up my plans? I'm using DIS with a modified version of 6E.
__________________ Increasingly I find the difference between a 'fact' and opinion is the number of people that believe it.
3.4 block converted to roller valvetrain with 220/225 cam on 115 lsa, early '769' heads with 3500 valves, LS6 springs & mild porting, worked over heddman headers, 3500 plenum with ported 3400 lower & 'short star' 65mm throttle. 210hp at 5800ft (that's 270hp at sealevel )
It might, if you can get a short enough dwell. Isn't cutting the fuel the normal way to do it?
Yea, but that's a no no with n2o.
I was looking through the 6E hack briefly and noticed some dwell related stuff... I thought the icm was what did the dwell too but that got me wondering.
Ultimately it would be nice to have a spark based rev limiter but aside from something goofy like wiring up a relay to kill power to the icm, finding a way to change dwell is the only way to do it... more research tomorow... bedtime now.
__________________ Increasingly I find the difference between a 'fact' and opinion is the number of people that believe it.
3.4 block converted to roller valvetrain with 220/225 cam on 115 lsa, early '769' heads with 3500 valves, LS6 springs & mild porting, worked over heddman headers, 3500 plenum with ported 3400 lower & 'short star' 65mm throttle. 210hp at 5800ft (that's 270hp at sealevel )
I'd be tempted to experiment and watch the waveform on the ignition scope. I don't know by what means the ECM would communicate the desired dwell to the module, though.
There's a few disfunctional or carryover code sections in 6E that look like something gm planned to implement but didn't. The power steering logic is another example that just doesn't work, but it's there taking up space... I need to build an ecm test bench to test this stuff out quicker.
__________________ Increasingly I find the difference between a 'fact' and opinion is the number of people that believe it.
3.4 block converted to roller valvetrain with 220/225 cam on 115 lsa, early '769' heads with 3500 valves, LS6 springs & mild porting, worked over heddman headers, 3500 plenum with ported 3400 lower & 'short star' 65mm throttle. 210hp at 5800ft (that's 270hp at sealevel )
You could also use spark retard. Basically as the engine approaches its cutoff RPM, you rapidly pull spark. This would effectivly arrest the engine in a more controlled manner rather than cutting fuel or spark. Another option, if your diving into the code, is to allow the ECM to control the N2O. A few hundred RPM before the cutoff is approached, you cut the flow of nitrous. When the RPMs have stabilized, you then restore the flow. This will also allow the ECM to control the additional fuel directly, so the mixture can be enriched prior to adding the nitrous. Makes it less likely that you will blow the intake off when you hit the button.
How much coding are you planning on doing? There are some other improvements that you can make to the 6E as well.
Also, are you using the 6E code on a 6 cyl.? IIRC, the 6E code is explicitly designed for an 8 cyl, and assumes that 8 cyls. are present in the fueling logic if my memory serves me right. You can use it on a 6, but the MAF calcs will not be correct as the fuel is calculated as a duty cycle, rather than as actual mass of air per cylinder like modern MAF systems.
Yep, v6 with 6E. The maf is from a '97 thunderbird so recalibrating was a given. I've been recalibrating what was an ARAP base for sevral years now so it runs like a watch. The LV8 calc has a scalar that needed to be changed and I had to set the # cyls & fueling mode to v6 but other than that I haven't found anything that makes it v8 specific.
There's a few simple code changes like wbo2 input and extended the main spark table to 6400 rpm that were done over the years but I only recently took on the challenge of rewriting all the LV8 stuff for a 3bar map, n20 controlled by the egr table, writing launch spark retard code and a bunch of other stuff I have planned. It's going to be something along the lines of BAUJP, but flexible enough for any type of power adder.
I did a spark retard rev limiter but decided against it, ended up as a flamethrower. Cutting the nitrous is a good idea, I should have thought of that. The problem I keep running into is finding space for new stuff. I also need to figure out a way for the LV8 calc to repalce the map incase the map fails. The simple solution was leaving LV8 alone & having the map write to the same location, but that makes reading the datalog kinda hard as the signal constantly switches between the two. Doesn't appear to effect spark though.
Have you made a compilable hack yet? Thats how i start my projects. Something the size of the $6E can be made to compile in about 1-2 days of work. After that, you can delete and change things at will as the addressing can be made inherent, which allows you to relocate blocks of code. You could then also add things like a true 16-bit single table MAF lookup and fuel calcs for better resolution, or replacing the LV8 SA with true MAP based SA.
I would use the ecm to control it like the 4th gens do. cutting spark or the rev limiter as a nitrous saftey? sorry to come off mean but your asking for broken parts. the solenoids are still going to be dumping nitrous and fuel while the eng is off for a few split seconds guess whats going to happen!!
I think shutting it off a few hudred rpm ahead would be enough for the lines to empty. Spark cut is the better way to go but so far there really isn't a way to do it with these ecm's. Even if you kill the signal the icm will still fire at base timing, so the only way is to command either less spark or shorter dwell and dwell is controlled by the icm. Other ideas?
I think shutting it off a few hudred rpm ahead would be enough for the lines to empty. Spark cut is the better way to go but so far there really isn't a way to do it with these ecm's. Even if you kill the signal the icm will still fire at base timing, so the only way is to command either less spark or shorter dwell and dwell is controlled by the icm. Other ideas?
The GM fuel cut and power adders just don't work well together. N2O can be coded to shut-off at a certain RPM before pulling fuel. Not so with Turbo/Supercharger. It is a more difficult problem. It requires spark being cut.
Don't dwell at all for a given pseudo-random spark event with cut spark. You could also use the scheme of cutting power to the coil like the EDIS requires for cutting spark. Yeah, with the EDIS that is the only way to cut spark. At least with the GM dizzy you can cut the icm control signal.
I currently start adding a little more fuel and pull timing once the rev limit is hit as a means to slow down the rate at which the engine revs. It is not a rev limiter, but is the next best thing.
That's probably the best compromise. It may shoot flames without a catcon but it gets the job done without hurting stuff.
__________________ Increasingly I find the difference between a 'fact' and opinion is the number of people that believe it.
3.4 block converted to roller valvetrain with 220/225 cam on 115 lsa, early '769' heads with 3500 valves, LS6 springs & mild porting, worked over heddman headers, 3500 plenum with ported 3400 lower & 'short star' 65mm throttle. 210hp at 5800ft (that's 270hp at sealevel )
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