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| timing question for Tom Drake https://www.slantsix.org/forum/viewtopic.php?t=21679 |
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| Author: | Sam Powell [ Wed Jan 31, 2007 6:16 am ] |
| Post subject: | timing question for Tom Drake |
Hi Tom, I am hoping you can give me some useful advice here. My turbo EFI slant has never run to my satisfaction, and installing the DFI ECM made things more complicated, and hence worse, not better as I expected, and or hoped for. The ECM has been deemed correctly functional by Accel's tech department on the simulation machine, so any problems are either in calibrations, or my hardware set up in some way. I am open to any and all suggested changes. The specific need right now is to determine what is an appropriate timing setting under boost for a slant. I understand you have one of the best around. I have a mild cam, and am running 7 lbs of boost. When Eli looked at the calibration file in the ECM, he thought the timing was not advanced enough under boost. I think the calibration file he was looking at had the timing pulled down to about 10 degrees BTDC under 8 lbs of boost. He was worried about generating accessive heat in the turbo itself through late ignition. I think, however he is evaluating this in terms of a big bore V-8 and not a small bore inline engine. Can you, in general terms, tell me what your timing is under boost. How much advance are you running at 7 lbs of boost? I told Eli I would get back to him after I had heard from you. He sounded very interested in finding out what your recommendations are, and sounded willing to update his axioms about forced induction by adding small bore input to his experience. Thanks. Sam |
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| Author: | Rust collector [ Wed Jan 31, 2007 9:13 am ] |
| Post subject: | |
I am not Tom, or a guru of any kind, but 10 degrees sound awfully low to me. |
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| Author: | Tom Drake [ Wed Jan 31, 2007 9:59 am ] |
| Post subject: | |
We have run 24 degrees for quite a while now on 10-12# of boost. Remember that we are on Methanol so that affects how much we can get away with. Tom I no guru either! |
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| Author: | DionR [ Wed Jan 31, 2007 3:36 pm ] |
| Post subject: | |
You might try looking around the internet for a table showing advance for a '86 or '87 2.2 turbo, non-intercooled. They had virtually the same bore and stroke, so the spark advance would be similar. The later 2.2/2.5's had a fast burn head, so I expect those tables would be wrong. If you don't find something, I will try and post the info I've saved (for this exact reason) tomorrow. |
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| Author: | Sam Powell [ Wed Jan 31, 2007 4:35 pm ] |
| Post subject: | |
Thanks guys. My slant has a pretty much stock cam, with wider lobe centers to eliminate overlap somewhat. How do the cams metioned so far, the Drake's car, and the early 2.2 Turbos compare cam wise, and how would this effect the timing? I know bigger cams can take more timing since they reduce cylindar pressure somewhat. Although I would think a turbo more than makes up for this reduced pressure from the bigger camshaft. In retrospect, I think this thread should have been started on the Engine section. Sam |
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| Author: | Tom Drake [ Wed Jan 31, 2007 5:58 pm ] |
| Post subject: | |
We ran the MP purple shaft cam...the small one. Pretty mild cam. The first cam we ran was a stock 1976 cam. |
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| Author: | DionR [ Thu Feb 01, 2007 4:18 pm ] |
| Post subject: | |
Don't know the separation on the 84-87 turbo cam but lift is .430 and duration was 240-240. I will try and find the lobe separation in my MP book later. Here is a chart showing the 2.2 T2 advance compared to the Mopar Performance 2.2 T2 advance. The base one is the second chart, the upgraded MP setup is the first. Hope it helps. Don't forget this is for a 12 psi intercooled application, too. 
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| Author: | Sam Powell [ Thu Feb 01, 2007 5:27 pm ] |
| Post subject: | |
Thanks Dion, I printed that out, and it is in my notebook now. It looks like they were running considerably more advance than I have been able to so far. Check the new thread for new developements. Sam |
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| Author: | DionR [ Fri Feb 02, 2007 8:21 am ] |
| Post subject: | |
Just to finish this, the stock 84-87 turbo cam has a lobe separation of 110 degrees and 20 degrees overlap. For comparison, the N/A 2.2 cam is 244-244 duration, .430 lift, 108 separation and 28 degrees overlap. |
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