dpkilty's EJ25 powered build log

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dpkilty
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Re: dpkilty's EJ25 powered build log

Postby dpkilty » 14 Sep 2016, 07:24

So I am still debating on inboard or outboard suspension setups...

The last couple months have been spent looking up parts and prices and getting a ballpark idea of what everything is going to cost. The problem is now after seeing the total cost of the build slowly add up to near $20k I am slowly going back through everything and seeing what's needed and what's wanted. Do I really need titanium banjo bolts for the brakes? No. Not at all. Are they cool? Yeah, and they weigh less... Neither are big enough factors to justify the $26 I'd be spending on them though. Especially when the stock banjo bolts are just fine. I could even add them later if I really felt compelled to. Anyway...

Outboard setup: cheaper, easier, lighter.... all three things I like to hear. But I am just trying to be sure I have the right components selected for the shocks and springs. QA1 has changed their lineup and now the recommended "book" shocks are now the Proma Star Double Adjustable DD601. Those are 18.75" long extended and 12.625" long compressed. That will work for the outboard shock as well? I believe that works fine for the inboard setup, I just want to double check.
As for springs I understand I'll likely need a stiffer spring versus and inboard setup. The inboard setup I believe is around 200 in/lbs, QA1 offers 200, 225, 250, 300, and 350. I am thinking of stepping up to the 250. The rear setup is 300. Or would I be better to start at front 300 and rear 350? I know its all subjective, but I will have a little more weight in the rear of the car compared to Kurt's. So I'm thinking a slightly stiffer spring may be needed anyway.

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Re: dpkilty's EJ25 powered build log

Postby Midlana1 » 14 Sep 2016, 13:12

Due to both less shock travel and the large layover angle, the springs need to be much stiffer, like double the inboard rate, maybe as much as 600 lbs or so. Related to this, even though the outboard solution is lighter in concept, the stiffer spring weighs a decent amount more than its equivalent inboard cousin for the same wheel rate.

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Re: dpkilty's EJ25 powered build log

Postby ChrisS » 15 Sep 2016, 08:32

I pondered inboard/outboard for a while and in the end, have decided inboard for two main reasons - a suitable outboard upper mounting point risks looking ugly and I really didn't want to run such an acute spring/damper angle as was looking likely, nor want to have to deal with the falling rate that comes along with that nor the relatively high spring rate required.

Inboard is a bit more complex to build but not all that much and same goes for cost really.

Really though, no totally compelling reasons to go either way so it comes down to a matter of taste more than anything I think. I've never had inboard suspension on a car so that's another (weak!) reason to give it a try.

YMMV as they say.

dpkilty
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Re: dpkilty's EJ25 powered build log

Postby dpkilty » 15 Sep 2016, 11:07

I have no real preference either way. I like the looks of the inboard suspension and everything, I just recall Kurt mentioning in the book about how outboard would possibly be easier and cheaper.
If there isn't much difference really then I'll stick with inboard and go on.
After doing some digging on the forum it does look like its not quite as simple as throwing a strut and a spring in place and going on.

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Re: dpkilty's EJ25 powered build log

Postby Midlana1 » 15 Sep 2016, 11:19

dpkilty wrote:...After doing some digging on the forum it does look like its not quite as simple as throwing a strut and a spring in place and going on.

In comparison though, it does seem that way.

I tend to come across as overly negative sometimes and to be fair, I'm very happy with the suspension geometry and resulting shock rate of going inboard. Just expect some extra work go get there!

dpkilty
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Re: dpkilty's EJ25 powered build log

Postby dpkilty » 16 Sep 2016, 09:34

No worries about anything.
That's why I am trying to figure most things out now instead of later.
I'll just go with an inboard setup (which I had planned for anyway).

I have since moved on to wiring and I am finding conflicting data about what gauge wire to run. I do plan on spending the extra money and doing things to be more like a motorsports harness. I would like to offer that service as a part of my business so I figure this is a great way to get more experience. Kind of a two for one deal...

I plan on using Mil Spec MIL-W-22759/16 wire.
The wire supplier (Pegasus Racing) shows this:
AWG Current Rating* Insulation Diameter (Inches)
24 Gauge 5.1 amps 0.045"
22 Gauge 6.3 amps 0.052"
20 Gauge 8.9 amps 0.060"
18 Gauge 11.4 amps 0.071"
16 Gauge 13.9 amps 0.079"
14 Gauge 17.7 amps 0.095"
12 Gauge 24.0 amps 0.120"
10 Gauge 32.9 amps 0.138"
* Current Rating is based on continuous duty for wires in bundles, harnesses, or conduit at sea level.

Using various generic online calculators is giving me different results when trying to figure AWG size per circuit.
I'm thinking its mostly because the other online calculators:
1: factor in length which the table above does not
2: is for generic wire not the exact wire. Differing insulation and conductors could be causing the issue.
3: the above table says its for wires in bundles, many of the online calculators say they are not rated for bundles...

Right now I am planning my circuits based on the table above. Once I get all my data for amperage and lengths then I can post up that info and have a second set of eyes double check my maths.

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Re: dpkilty's EJ25 powered build log

Postby Midlana1 » 16 Sep 2016, 11:46

The variables you list are all valid. A big part of the problem is that it's completely arbitrary what's - short of melting - an allowable temperature rise for a given wire is. It all depends what (again, arbitrary) safety factor is being used.

dpkilty
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Re: dpkilty's EJ25 powered build log

Postby dpkilty » 19 Sep 2016, 13:41

Again still just rough guessing on a few things here (mainly length, which I'm just using an arbitrary 10 feet for everything) I have basically told myself that 10 amps is the cutoff. Anything below 10 amps is going to be run on 20 ga and anything above will be 12 ga. If I have a circuit that is close to the 10 amp limit I'll probably move it to 12 ga wire. I plan on using a lot of LED's for tail lights, turn signals, and even headlights. So hopefully I can keep the amperage down a little there.

According to the chart I posted above everything should fall well within those limits.

It should make things a little easier to source connectors and everything as well. Plus since I do want to twist the wire harness all mil-spec like having the wire diameters match up like they do will make things a lot easier (hopefully)...

dpkilty
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Re: dpkilty's EJ25 powered build log

Postby dpkilty » 23 Sep 2016, 10:54

I know it seems like I am jumping all over the place with these questions (and I kind of am) but i'm doing research on systems here and there in my free time at work or other places. I get side tracked and go down rabbit holes all the time... you know how it is.

Anyway now its brakes. I'm a little confused with the line routing.

On my OEM car (and many others I've worked on) there are 4 individual lines. 1 for each wheel. They all come off the ABS distribution block. Usually 1 or 2 lines feed the block from the master cylinder.
In our case (depending on the master cylinder setup chosen) we will have 1 line coming off each master cylinder. Simple enough. One MC is front and one is rear. So I run my line from the MC to an arbitrary spot on the chassis and have a "T" fitting/block. Then I have a line going to each wheel. I'm okay with that. My hydraulic knowledge isn't the greatest but most of the time when you split things off like that you try to keep lengths equal after the "T" fitting. Is that also the case here? I am assuming so, but I've been wrong before...

Also my thoughts are to have the main line feed from the master cylinder route close to the front (or rear) of the car. Place my "T" fitting and run those lines close where a suspension arm connects to the chassis. Have another bulkhead type fitting that will allow the use of a shorter line that goes out to the wheel. That way if anything were to happen I am only replacing a line a foot or two long not one that is three times that. Yeah it introduces more places for leaks, but I like it for ease of maintenance in the event of bad things happening.

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Re: dpkilty's EJ25 powered build log

Postby Midlana1 » 23 Sep 2016, 12:32

For flow, you're right about wanting equal lengths after the tee, but for brakes it's all about pressure. You'll be fine regardless where the split is.


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