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> Dyno pull, Help
Jetsetsurfshop
post Mar 4 2015, 09:45 AM
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Doing a Dyno pull right now and we're having trouble getting an rpm reading using a plug wire and the positive side of the coil. Any advice?
Thanks.
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Bleyseng
post Mar 4 2015, 09:51 AM
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Try terminal #1 of the coil
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stugray
post Mar 4 2015, 10:00 AM
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Do you run a MSD?

With the multi spark system, it throws off some magnetic pickups.
If you measure from the coil, then the RPM will read 4X faster than measuring it on one of the cylinders.

I have been watching your thread in the paddock and I am interested in the results because my engine is very similar to yours.
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ChrisFoley
post Mar 4 2015, 10:12 AM
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QUOTE(stugray @ Mar 4 2015, 11:00 AM) *

Do you run a MSD?

With the multi spark system, it throws off some magnetic pickups.
If you measure from the coil, then the RPM will read 4X faster than measuring it on one of the cylinders.

I have been watching your thread in the paddock and I am interested in the results because my engine is very similar to yours.

If your intake and exhaust aren't the same too, you can expect very different results.
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ChrisFoley
post Mar 4 2015, 10:15 AM
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QUOTE(Jetsetsurfshop @ Mar 4 2015, 10:45 AM) *

Doing a Dyno pull right now and we're having trouble getting an rpm reading using a plug wire and the positive side of the coil. Any advice?
Thanks.

Last time I was on a Dynojet the rpm reading was pulled off one of the plug wires with an inductive pickup.
The direction of the pickup coil can make a difference so if it doesn't work, try flipping the clamp around on the plug wire.
Any spark plug works for your purpose since you aren't concerned with timing.
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Jetsetsurfshop
post Mar 4 2015, 10:35 AM
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QUOTE(Racer Chris @ Mar 4 2015, 08:15 AM) *

QUOTE(Jetsetsurfshop @ Mar 4 2015, 10:45 AM) *

Doing a Dyno pull right now and we're having trouble getting an rpm reading using a plug wire and the positive side of the coil. Any advice?
Thanks.

Last time I was on a Dynojet the rpm reading was pulled off one of the plug wires with an inductive pickup.
The direction of the pickup coil can make a difference so if it doesn't work, try flipping the clamp around on the plug wire.
Any spark plug works for your purpose since you aren't concerned with timing.

We did try to flip the inductive pickup. Didn't fix it. My plug wire are putting off a lot interference. There solid. I guess that a problem.
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stugray
post Mar 4 2015, 10:55 AM
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QUOTE(Jetsetsurfshop @ Mar 4 2015, 09:35 AM) *

QUOTE(Racer Chris @ Mar 4 2015, 08:15 AM) *

QUOTE(Jetsetsurfshop @ Mar 4 2015, 10:45 AM) *

Doing a Dyno pull right now and we're having trouble getting an rpm reading using a plug wire and the positive side of the coil. Any advice?
Thanks.

Last time I was on a Dynojet the rpm reading was pulled off one of the plug wires with an inductive pickup.
The direction of the pickup coil can make a difference so if it doesn't work, try flipping the clamp around on the plug wire.
Any spark plug works for your purpose since you aren't concerned with timing.

We did try to flip the inductive pickup. Didn't fix it. My plug wire are putting off a lot interference. There solid. I guess that a problem.


"Do you run a MSD?"

If so, there is a wire that gives a clean tach signal that can be used by the dyno (white or gray cant remember)
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Kansas 914
post Mar 4 2015, 11:27 AM
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QUOTE(stugray @ Mar 4 2015, 09:55 AM) *


"Do you run a MSD?"

If so, there is a wire that gives a clean tach signal that can be used by the dyno (white or gray cant remember)

If you are running MSD (6AL) here is a clip of the tach wire instructions:

Attached Image

Attached Image
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ChrisFoley
post Mar 4 2015, 11:48 AM
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Shane told me on the phone, no MSD box.
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Dave_Darling
post Mar 4 2015, 12:28 PM
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How about taking the signal off the (-) side of the coil, then? It'll read 4x higher than going off a single plug wire, but that shouldn't be a huge problem.

--DD
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Jake Raby
post Mar 4 2015, 12:30 PM
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This will also occur if you have a spark plug thats trying to foul.. Due to resistance increases in the lead.

I keep an optical pick up handy for weird instances like this, or when I test a diesel. If they have an optical pick up, you can solve this issue in 5 minutes.
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Jetsetsurfshop
post Mar 4 2015, 01:57 PM
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Swapped plugs. Worked out, thanks Jake.
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Jetsetsurfshop
post Mar 4 2015, 07:07 PM
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Thanks everyone for the help/suggestions. We finally got it. (IMG:style_emoticons/default/piratenanner.gif)
It was mostly on me. I didn't get the car ready for the pull. At first we were picking up interference from the plug wires and the spark plugs needed to be replace. Once we got this fixed, we got results. We ran out of time to tune the car. My only real goal is to get a class for Time Trails with the NASA group. Ill post up the dyno sheet in the paddock.
Thanks again Jake for the tip off on the plugs and thank you Chris for picking up the phone. Sorry I was so short. The shop needed me for another pull then.
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ChrisFoley
post Mar 5 2015, 07:40 AM
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QUOTE(Jetsetsurfshop @ Mar 4 2015, 08:07 PM) *

...
Sorry I was so short. The shop needed me for another pull then.

No problem, I've been there.
So glad you worked it out and didn't have to abandon the effort.
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stugray
post Mar 5 2015, 10:01 AM
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Still curious about results! :-)
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DBCooper
post Mar 5 2015, 10:22 AM
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QUOTE(Jake Raby @ Mar 4 2015, 10:30 AM) *

This will also occur if you have a spark plug thats trying to foul.. Due to resistance increases in the lead.

I keep an optical pick up handy for weird instances like this, or when I test a diesel. If they have an optical pick up, you can solve this issue in 5 minutes.


OK, some credit where credit is due; that was good, Jake. I get annoyed at you when everything is about selling or promoting and you're not actually helpful. But several times recently you've helped people out with information without doing any self-serving selling. That's a positive contribution to the community, something I both recognize and appreciate, so thanks. And something else of more practical importance, that's the kind of thing that enhances your reputation far more than the self-promotion ever could.

Good job.
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76-914
post Mar 5 2015, 10:35 AM
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post Mar 5 2015, 10:36 AM
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Michael N
post Mar 5 2015, 10:43 AM
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QUOTE(stugray @ Mar 5 2015, 08:01 AM) *

Still curious about results! :-)


Ditto. Can we see them?
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Jake Raby
post Mar 5 2015, 10:43 PM
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QUOTE(DBCooper @ Mar 5 2015, 08:22 AM) *

QUOTE(Jake Raby @ Mar 4 2015, 10:30 AM) *

This will also occur if you have a spark plug thats trying to foul.. Due to resistance increases in the lead.

I keep an optical pick up handy for weird instances like this, or when I test a diesel. If they have an optical pick up, you can solve this issue in 5 minutes.


OK, some credit where credit is due; that was good, Jake. I get annoyed at you when everything is about selling or promoting and you're not actually helpful. But several times recently you've helped people out with information without doing any self-serving selling. That's a positive contribution to the community, something I both recognize and appreciate, so thanks. And something else of more practical importance, that's the kind of thing that enhances your reputation far more than the self-promotion ever could.

Good job.


If I didn't know the answer to this problem I'd just be another one of those people with a huge image that has no freaking clue as to whats going on. I've gotten where I am from proficiency, and thats all. :-)

If that dyno graph is squiggly and looks "nervous" even with max smoothing thats another indication that you need a set of plugs, or have way too high of resistance somewhere.

BTW- These issues often occur with higher cylinder pressures, so this engine sounds like it's got some balls. When I approach 14:1 CR this sort of thing happens almost every time and the plug wires and ignition system that are used are very critical. Thats why I have an optical pick up to fall back on.

This post has been edited by Jake Raby: Mar 5 2015, 11:43 PM
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