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IP springs and their color versus resistance to compression
by
ORCoaster
on 21 Mar, 2021 23:14
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In my learning of the IPs on our early Rabbits and such I have learned, or thought I learned that there are basically 4 different colors of springs in the dynamic advance hole. That cover on the front of the IP is where I am talking about.
I thought the coveted spring color was green, it gives the fastest advance to the pump. Is that correct or am I not remembering this right?
Then comes the Silver, the Red, and the Blue in the order of harder to compress or less advance. Is this correct?
Today I pulled the front cover off my Rabbit and was going to put the green spring I thought was in there into the turbopump I have on the Caddy. Just to see what that would do for a faster jump with the truck. Well to start the spring was not green, and it was slightly shorter in overall length compare to the red one I did get out of the turbopump.
So I swapped them and the truck does seem a little peppier. Could just be me thinking I did all this work so I better see a change for the better.
So my questions are about the differences between colors and how does the shorter spring compare with those colors?
Does Anyone have that knowledge at their fingertips or on top of their head?
Thanks for the follow-up.
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#1
by
sgnimj96
on 22 Mar, 2021 09:02
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I think all those old factory advance springs are a little shorter than they started out. That's probably why shims get added.
Was looking at some different springs the other day, but they don't have any color left on them.
So I measured them with a caliper, then squeezed them and measured. Went with the tallest spring that would compress the most.
When putting that little cover back on, I can also feel how much tension is being put against the advance piston by how hard it is to press the cover closed without the screws.
Internal pump pressure is a big factor. Mine is adjusted to spec and a soft spring like the green one advances too much unless it gets a lot of shims added.
Those threads that talked about how great the green spring is didn't talk much at all about internal pump pressure.
Most of the "success" testimony IMO was that it compensated for a lack of dynamic advance.
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#2
by
ORCoaster
on 22 Mar, 2021 21:52
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I agree that internal IP pressure is key. I am going to bust out my adapter that fits on the pump and see what I am running on the turbopump. I am just baffled that my 2 door Rabbit with a NA 1.6 Liter engine seems to jump between the gears whereas the truck does not. I don't think there is that much of a weight difference.
I am running 2.5-inch exhausts on both so I am not backpressure limited.
That and the Rabbit gets better mileage. So I know I need to figure out where my power is going. Or maybe not getting into the power band.
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#3
by
fatmobile
on 22 Mar, 2021 23:02
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I'm pretty sure the green spring came from the 1.5 diesels.
I've seen them in the 107A pumps that came on the 1.5.
The stroke was shorter so the RPMs went higher.
So it had a different timing curve.
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#4
by
ORCoaster
on 23 Mar, 2021 22:07
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By stroke, I am thinking the length of the rod itself right? Memory is blurred after the Covid attack. Maybe even before that.
So it stands to reason the 1.5 would spin faster then. When you mentioned that green spring came on the 1.5 pump I think that is where mine is hiding. In the box with the rest of the 1.5 stuff. So thanks for mentioning that. I really thought I put it in the Rabbit. And indeed I may have but then got a second pump for my veg oil conversion way back when and I picked up a second pump then. It runs awesome so not fooling with it. It had the silver spring in it.
I wish I could figure a way to measure the compression on these springs but alas I don't have that equipment and finding the answer is more of a curiosity than a need.
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#5
by
sgnimj96
on 24 Mar, 2021 12:48
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I just squeezed the spring as hard as I could with thumb and finger, with a digital caliper on it to measure. Not perfect but it does give a clear indication of the differences in springs.
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#6
by
fatmobile
on 28 Mar, 2021 22:46
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I usually set a couple different weights on a spring and see how much it moves.
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#7
by
ORCoaster
on 30 Mar, 2021 00:06
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How much weight do you usually use? Are we talking pounds, like 2 or 3 or more like 1?
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#8
by
fatmobile
on 31 Mar, 2021 02:36
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Depends on how strong the spring is.
For the VNT 15 boost controller spring I think it was 5 pound bag of sugar.
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#9
by
libbydiesel
on 31 Mar, 2021 19:15
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A nice way to measure spring rate is to place a scale on a drill press, then place the spring on top with it under the chuck. Then set it up so the chuck is touching the spring with just a slight bit of tension and set the stop at a given distance lower. Zero the scale and compress the spring to the stop distance and read the weight on the scale. A simple bit of math (if you aren't compressing a full unit of the distance of your rate) will give a relatively accurate value for the rate.
At this point I have a nice drill press and an accurate digital shipping scale. A workable substitute for the shipping scale is a bathroom scale, and a workable substitute for the drill press is to clamp both spring and scale in a vice, measure, compress further and measure length and difference in weight, etc...
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#10
by
ORCoaster
on 31 Mar, 2021 22:34
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I am now distracted by a new pop tester that arrived today. I will be going through the box of "extra injectors" to see IF I can come up with a nice balanced set. Those will go in the Caddy and I will see how bad those really are. I think I have one of the four that is not playing nice in there.
I almost bought a drill press from the Habitat for Humanity Restore last week. I just don't really have the need or the room for it. But now maybe I will go back and see if it is still for sale.