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Old 12-10-2008, 12:40 AM   #1
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Default MAP signal problems



I have a vac hose from the front of the manifold, into the car, with the boost gauge "T" about 1' from the computer.

Do I need to rethink this, or do the little fuel filter on the vac line?
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Old 12-10-2008, 12:47 AM   #2
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T off of the fuel pressure regulator vacuum line or use the nipple on the back of the 99 intake that isn't used by the stock system. It has a clean signal that will possibly eleviate this problem. The front port tends to be turbulent in comparison.
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Old 12-10-2008, 12:50 AM   #3
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I've heard that its bad to T off stuff because the T's create restriction.
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Old 12-10-2008, 12:53 AM   #4
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Whoever said that is full of **** in this case. I have a FUEL FILTER in my MS map signal line to actually create a restriction to keep the signal clean.
Go shove your needle dick in the vac line for a while, let me know when it fixes your irregular map signal.
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Old 12-10-2008, 01:02 AM   #5
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Quote:
Originally Posted by hustler View Post
I've heard that its bad to T off stuff because the T's create restriction.
Technically they do, however a restriction is only a problem where there is flow across it. Neither the MAP sensor nor the fuel pressure regulator actually pass any air through them- there is virtually zero flow through the tee, thus there is virtually zero pressure drop across it. You could pass the signal to either through an orifice with a 0.5 mm passage and it wouldn't matter in the least.

The FPR line is an excellent place to take the MAP signal from, as is the brake booster line. I tee'd the rubber brake line just before the checkvalve, which made for a very convenient run through the unused rubber plug in the firewall next to the speedo cable.
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Old 12-10-2008, 01:04 AM   #6
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Go shove your needle dick in the vac line for a while, let me know when it fixes your irregular map signal.
lol
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Old 12-10-2008, 01:05 AM   #7
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Yeap, agree to the above post. I used some tiny *** small vacuum line to help smooth the signal going to MS. Like really really small ID. And the line is ~8' long too as it runs from the port Chad described to under the car, and comes up under the passengers seat area where my MS2 is. It did help smooth the signal a bit, though I still get electrical noise on it.
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Old 12-10-2008, 01:31 AM   #8
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My MAP looked similar when I had the line at the front of the IM. I did the recommended fix of teeing it off the FPR and added a small inline filter (HD/Lowe's has several in the lawn mower parts section) and that smoothed it out nicely. It didn't cause the engine to run much differently, but VE analyzer in MLV seems to work a bit better without the 3-4 kPa fluctuation bouncing it between table cells. I also recall that MAP fluctuations may have been triggering someone's MAPdot accel enrichments, but you shouldn't have that problem if running TPS-based enrichments.
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Old 12-10-2008, 12:40 PM   #9
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I used some tiny *** small vacuum line to help smooth the signal going to MS. Like really really small ID.
There is much truth here.

When I was running an EMU, I initially used 3/16" (I think) rubber vacuum hose coming directly off the back of the manifold and into the MAP sensor. The signal was very noisy- lots of peaks. I later changed this so that the MAP sensor was teed off the line that was feeding my boost gauge, which involved several feet of ultra narrow semi-rigid plastic tubing and compression fittings. The signal immediately smoothed out.
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Old 12-10-2008, 03:21 PM   #10
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This is how mine has always been, guess thats why I don't have issues.
Quote:
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There is much truth here.

When I was running an EMU, I initially used 3/16" (I think) rubber vacuum hose coming directly off the back of the manifold and into the MAP sensor. The signal was very noisy- lots of peaks. I later changed this so that the MAP sensor was teed off the line that was feeding my boost gauge, which involved several feet of ultra narrow semi-rigid plastic tubing and compression fittings. The signal immediately smoothed out.
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Old 12-26-2008, 11:11 PM   #11
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thread ressurection for great benefit to future searchers
after moving to the FPR line:
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Old 01-21-2009, 12:38 AM   #12
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my **** is acting up again:

and from the same log, nothing changed:


i have the very tiny vac hose goes from the FPR line, then a T for the boost gauge, then to MS. What am i ******* up?
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Old 01-21-2009, 03:54 PM   #13
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go to home depot and get a mig welding tip--the largest wire hole they carry. put it inline with the signal. it may only be a .030 hole and you may want to drill it out to .040 or .050 so get those drills too.

what wastegate are you running? it might also be doing that since that's how they work.
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Old 01-21-2009, 11:27 PM   #14
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Quote:
Originally Posted by y8s View Post
go to home depot and get a mig welding tip--the largest wire hole they carry. put it inline with the signal. it may only be a .030 hole and you may want to drill it out to .040 or .050 so get those drills too.

what wastegate are you running? it might also be doing that since that's how they work.
I'll try that home depot ****...should I put the FPR behind the restriction too (makes sense to me).

I have the wastegate connected directly to the compressor nipple. Should I put a nipple on that and go of the vacuum bank in the brake-line?
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Old 01-27-2009, 04:19 PM   #15
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the inline fuel filter fixed this.
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Old 01-27-2009, 08:40 PM   #16
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can someone please post a "perfect" map signal so I can know my goal?
[img][/img]
this is the best I have so far.
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Old 01-27-2009, 08:46 PM   #17
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Small vacuum line.

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Old 01-27-2009, 09:58 PM   #18
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it aint perfect, but the boost is ruler flat.
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Old 01-27-2009, 11:08 PM   #19
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I need to fix the map problem and wire up TPS on the NOW!!! Who in the Houston crew wants to let me borrow their shade?
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Old 01-27-2009, 11:32 PM   #20
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On the topic of the inline fuel filters, I went to HD and they did not have any fuel filters for lawn mowers at all. Went to OSH and found only one - intended for a 1/4" or 5/16" ID line... kinda big but I bought it as I couldn't find any others. Anyone have a better source for these that works with smaller vac line?
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