unixcowboy

Does anyone have any idea what spring rate the fuel pin spring is?

I checked mine - the pink ( red ) and green one - on a homemade spring tester and it shows ~ 15psi to 1/2 compression and 25psi to full compression.
I've found 2 different numbers listed :
464 617 700
464 617 701

I'd like ~ 10psi higher since I can easily hit 45psi, and with cruise control set at 70mph if I hit a good hill the boost will spike over 25 and settle in at ~ 18 - 20psi.

jimbo486

any wastegate on the hx-40 that can be adjusted? how about the starwheel, have you adjusted it up to increase spring tension?

EDIT: or what you're saying is you'd like ~35psi of spring tension but still be able to fuel the same amount at full pin travel?

unixcowboy

Right Jimbo486.
I want the extra tension to prevent the pin from moving under low boost.
I'm getting too much fuel at low boost but I can provide the fuel when needed at higher boost. When I first put in my new sticks - and forgot to connect the wastegate - I hit 55 psi and had gobs of smoke because the engine was turning too slow. After connecting the wastegate the max boost dropped to 47 which I think is a livable number but smoke got even worse, and it didn't feel like the power was up where it should be.
Granted I've still got a pretty loose TC and the single clutch can't hold what power I have now, I am planning on going to a triple clutch TC sometime this year. That should help performance but it's also going to increase the smoke because the engine will be loading better.

I want to make max power and try to keep it as clean as possible.
Not that I don't like the smoke, I just don't want it running around town at 35 - 40 mph and 3 - 15 psi boost. Since the stock settings and sticks didn't smoke at those numbers I'd like to get back there so it'll be a real sleeper.

big stinky

Some guys on here used a manual boost controller in the afc line...

That would delay signal so you wouldnt get afc signal till after say 15 psi or whatever... That combined with a custom spring could get you there...

Just wondering what you used to test the springs? Im assuming you either used the stock diaphragm or did a bunch of math to figure out the area on the diaphragm?

jimbo486

a spring compressor with a dial indicator on it. looks like a drill press with a big foot on it. spring gets compressed between the "foot" and the table. the dial measures psi and usually there's a ruler of some sort to indicate the distance the press has traveled.

unixcowboy

What jimbo486 said, except I made one out wood.
Put a pivot in the middle that I can pull down with a fishing scale.
Watch the compression 'til the coils are fully compressed and read the weight.

I know how fish scales tend to be over optimistic but it's close enough...

BTW - just finished making a new spring out of 0.125 music wire....
Measured 20 lbs to 1/2 compress and 35 lbs to compress fully. I'll take the truck out and try it later today.

big stinky

How can you effectively measure psi without knowing how many square inches you have?

Or am I overthinking this?

Another thing I was thinking about was a variable rate spring...

unixcowboy

You're making it complicated.
The spring doesn't care about square inches, it's got a specific amount of pressure it will apply. You can measure this by compressing the spring and measuring how much force it takes to make the coils touch.

I've put a smear of grease on the pin and driven the truck watching the boost and then pulled the pin to see how far down the pin the mark went. It moves ~ 1/3 of the total with boost limited to 15 psi.
I just came back from driving with the new spring I made and never let the boost go over 15 psi and the mark on the pin in ~ 1/4 of the total travel. So the new spring does hold the pin up longer. I also noticed in my side mirror that the truck doesn't smoke as much now when pulling away from a light. And my right foot is still as heavy as it always has been.
I'll be driving on a road that's 60 mph speed limit later tonight so I'll see what happens then. That's when I smoked pretty good - getting up to 55 - 60 mph. The pin used to drop ~ 1/2 of full travel and I hope it stays to about 1/3 or so.

jimbo486

you made a spring?? sweet!! awesome results!!! now you can maybe play with the starwheel to fine tune the spring rate. having a spring with different rates leaves the potential for mulitple springs with different tensions to be made in the future instead of having to adjust the starwheel up or down. however, the starwheel can still be used to fine tune the spring rate as i already mentioned.

unixcowboy

Of course if you don't compress the spring all the way you'll not get the maximun resistance the spring can apply.
Right now my starwheel is 3 1/4 turns from the bottom so that means I can reduce the total tension of the spring. Unfortunately I wound the spring in a constant rate so I really can't get too much adjustment out of it. Still learning how to get springs to do what I want
I've read about winding variable rate springs and will probably tackle one but not now. You can make them tight when they first compress and loose when you get near full compression - or you can make them the other way. Fascinating reading.

I also found out that a spring with 3 1/2 turns like ours can be made to a higher strength by - of all things - reducing the number of turns. SO a 3 turn spring shoud be higher and a 2 tuns one should be higher yet.
Lots to play with...BUT if anyone is thinking of doing this be very careful. I put too much stress on the 0.125 music wire and it snapped.....Almost took off a finger, hurt like EDIT for a couple of days. I'd hate to see that wire fly towards my face !!!

jimbo486

wow! not sure if i wanna rack my brain now trying to understand how to make springs with higher strength and less tension or vice versa and many other attributes

Fred Swanson

so what about running the starwheel all the way up. I do that for summer driving in the crazy heat, and it helps alot for cutting down the smoke, but doesn't limit the travel that I can tell.

unixcowboy

Fred,
Get a caliper and compress your spring inside the caliper by squeezing the jaws with your fingers. Read the measurement, it will probably be close to what mine measured - 0.300.

Run your starwheel all the way up and - if your caliper can measure depth - measure the depth of the inside of the starwheel to the top of the hole where the pin goes.

I don't remember what mine read but I think you'll find it's less than 0.300.
That means you're compressing the spring as far as it will go before your pin is hitting it's maximun travel.

jimbo486

it won't limit travel so much as it will call for more boost so that the pin can overcome the spring tension in order to get more fuel. if you have it run all the way up and not getting enough fuel to spool the turbo, you won't get the fuel you need and it will limit you on power. just a quick thought. i could be wrong. i'm still fairly new to all of this

unixcowboy

That's what I thought also Jimbo.
I turned my pin - the M2 - 180* so the cut side was facing away from the afc pin. Then I took the truck for a drive.
It's surprising how much boost you can get with the pin effectively disabled...
I was able to get nearly 20 psi. Of course that's all I got.. I normally run much higher.