 cylinder head temp sensor, what the brain thinks |
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| worn |
 Jun 19 2013, 09:14 AM
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#1
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Winner of the Utah Twisted Joint Award  Group: Members Posts: 3,560 Joined: 3-June 11 From: Madison, WI and North Bend WA Member No.: 13,152 Region Association: Upper MidWest 
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Well, I have been tweaking the MPS. I still am having low torque below 2,000 rpm, making smooth transitions to speed a bit more dramatic than I would like. I think that the cam may be playing a role here that I may never tune out completely. Now over 2,000 is another story (IMG:style_emoticons/default/laugh.gif) (IMG:style_emoticons/default/w00t.gif)
The point of this post is that if you are fooling around and the cylinder head temperature lead (I think it is Temp I) comes undone, the brain sees infinite resistance. It therefore, on a warm summer evening, thinks the motor is frozen cold and dumps in fuel. It won't start. You have spark, you have fuel, but the thing is flooded to the gills. Nooo, its EFI! Yep, flooded. (IMG:style_emoticons/default/hissyfit.gif) So I started thinking that a spare might be in order since no start can mean travel by foot - or used to before cell phones. An alternative would be alligator clips to simply ground the lead. That way the brain would think the engine was hot and you could limp home. My list of spares on a trip away from home is growing. |
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| Cap'n Krusty |
Jun 19 2013, 01:43 PM
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
QUOTE(worn @ Jun 19 2013, 08:14 AM)  Well, I have been tweaking the MPS. I still am having low torque below 2,000 rpm, making smooth transitions to speed a bit more dramatic than I would like. I think that the cam may be playing a role here that I may never tune out completely. Now over 2,000 is another story (IMG:style_emoticons/default/laugh.gif) (IMG:style_emoticons/default/w00t.gif) The point of this post is that if you are fooling around and the cylinder head temperature lead (I think it is Temp I) comes undone, the brain sees infinite resistance. It therefore, on a warm summer evening, thinks the motor is frozen cold and dumps in fuel. It won't start. You have spark, you have fuel, but the thing is flooded to the gills. Nooo, its EFI! Yep, flooded. (IMG:style_emoticons/default/hissyfit.gif) So I started thinking that a spare might be in order since no start can mean travel by foot - or used to before cell phones. An alternative would be alligator clips to simply ground the lead. That way the brain would think the engine was hot and you could limp home. My list of spares on a trip away from home is growing. The ECU needs, no MUST, see a ground at the CHT wire. No ground, no start, no run. As for the camshaft, I'm guessing you are talking about a profile other than stock. IME, and I've been working on 914s for 40 years, you're NEVER going to get acceptable low end performance or idle with virtually any aftermarket grind. Early on, I worked with the guy who developed the first (and probably the best) aftermarket diagnostic machines as well as another guy who was the first person in the US to rework MPSs, and they couldn't get past the vacuum signal problem. Times have changed, but D-jet hasn't. Same old analog system, pretty limited by hardware and the basic design. The Cap'n |
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| worn |
Jun 19 2013, 03:13 PM
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#3
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Winner of the Utah Twisted Joint Award Group: Members Posts: 3,560 Joined: 3-June 11 From: Madison, WI and North Bend WA Member No.: 13,152 Region Association: Upper MidWest
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QUOTE The ECU needs, no MUST, see a ground at the CHT wire. No ground, no start, no run. As for the camshaft, I'm guessing you are talking about a profile other than stock. IME, and I've been working on 914s for 40 years, you're NEVER going to get acceptable low end performance or idle with virtually any aftermarket grind. Early on, I worked with the guy who developed the first (and probably the best) aftermarket diagnostic machines as well as another guy who was the first person in the US to rework MPSs, and they couldn't get past the vacuum signal problem. Times have changed, but D-jet hasn't. Same old analog system, pretty limited by hardware and the basic design. The Cap'n Well, thanks Capn'. Yeah. The big problem happened early when I didn't make sure the spade plug was in tight. Then go pull the MPS for a little tweak and sleeve catches. Yeah, it is a webcam 73 + 2.5 degrees. I like it, and I had a hunch it would not have the low rev torque. That isn't what they are supposed to do. Still, I have gotten it better and better with timing and air fuel. It is a real comfort to hear your opinion because it will allow me to quit beating a dead horse that much sooner. |
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| worn |
Jun 19 2013, 03:15 PM
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#4
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Winner of the Utah Twisted Joint Award Group: Members Posts: 3,560 Joined: 3-June 11 From: Madison, WI and North Bend WA Member No.: 13,152 Region Association: Upper MidWest
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QUOTE(worn @ Jun 19 2013, 01:13 PM) As for the camshaft, I'm guessing you are talking about a profile other than stock. IME, and I've been working on 914s for 40 years, you're NEVER going to get acceptable low end performance or idle with virtually any aftermarket grind. Early on, I worked with the guy who developed the first (and probably the best) aftermarket diagnostic machines as well as another guy who was the first person in the US to rework MPSs, and they couldn't get past the vacuum signal problem. Times have changed, but D-jet hasn't. Same old analog system, pretty limited by hardware and the basic design. The Cap'n Forgot to ask. What is the best source of a "stock" grind cam? Is the only route regrinding? |
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Posts in this topic
worn cylinder head temp sensor Jun 19 2013, 09:14 AM
lsintampa May be why some go to carbs.
Once something with... Jun 19 2013, 09:26 AM stugray Worn,
My recent experience says you are correct. ... Jun 19 2013, 11:47 AM stugray
I have a stock cam with matching lifters I would... Jun 19 2013, 03:28 PM Cap'n Krusty Webcam has been selling that grind for as long as ... Jun 19 2013, 04:09 PM
worn
Webcam has been selling that grind for as long as... Jun 19 2013, 09:37 PM green914
May be why some go to carbs.
Once something wit... Jun 19 2013, 04:47 PM ThinAir FWIW, I'm running an Elgin 330-1 cam in an oth... Jun 20 2013, 12:56 AM ThinAir Update: I just did the first fill-up after making ... Jul 12 2013, 12:13 PM Retread
Update: I just did the first fill-up after making... Jul 12 2013, 03:55 PM r_towle Ask SLITS nicely if he has the 411 VW mps unit he ... Jul 12 2013, 09:16 PM Tom The CHT is TS2 and contrary to what The Cap'n ... Jul 14 2013, 08:24 AM |
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