In reply to GaryC83 :
Yikes, the prices on those are crazy. Not sure why someone would pay that for what looks to be a plastic Holley hi-ram clone.
Long term I'd love to make my own patterns and do some Aluminum casting. I'm working on building a CNC router with this sort of thing in mind.
In reply to Nukem :
Agreed 100%. Financially doesn't make sense for what you are getting. At $600-l000, I'd have a different attitude, but with a LOT of unknown longterm potential issues..and that pricing.. its kind of a joke, in my opinion.
If that was guy in his garage messing about, for his own car I would have a *much* different attitude about them.
Being said, casting is a cool way to go. And don't be afraid of fabricated manifolds, either. We either scratch fabricate and or modify a TON of the stuff we do.
In reply to GaryC83 :
I could be that guy...
It might be cool to make a part that mates up with some of the Holley parts (lids, snouts).
Stock 5.0 HO Lower, Printed Base to mate with the HO lower, Holley cast throttle body adapter and hat ?
Biggest concern I had with doing a fully fabricated upper was getting the runner transitions from the lower to the plenum nice. If you've got thoughts there I'd love to hear them.
Nukem said:I've got some work to do to actually get the rocker suspension working. I followed this little article to run the numbers of what I currently have in CAD, and it wasn't good: https://www.waveydynamics.com/post/rising-rate-suspension
Effective motion ratio was reasonably close to the planned 1:1 around ride height, but fell off (and digressive) once it got near full bump / full droop.
EDIT: holy carp. What a wall of text. I'm leaving it for now, but I will happily delete it if you don't have use for the contents.
I want to admit fervently that I didn't absorb the whole article fully, so keep that in mind as I ask possibly silly questions... Though it felt like he was more concerned with aero platform and balancing rate against increasing downforce than with wheel rate and mechanical grip/balance/predictability.
I'm more accustomed to the "motion ratio" than the "spring leverage ratio" mode of looking at these things, and I think defaulting to 2:1 being 2 units wheel travel to 1 unit spring travel. I thought it was a little odd that he used one when working from the force based side and the other when starting with displacement to work to travel and damper, but maybe that's sensible (or maybe that's just the tip of the iceberg of things I'm missing).
In any case, the thing that's puzzling me is that I don't see any reference to accounting for the motion ratio being squared to get to wheel rate from spring rate. That is, if you take the simplest case of an X mm suspension arm and mount a coilover halfway at 0.5X mm, the motion ratio is 2:1. But the relationship of spring rate to wheel rate for this is 4:1. You have to square the motion ratio to accommodate the double action of the spring having half the leverage AND half the travel of the wheel. So a 1000lb/in spring in that situation would have a wheel rate of 250lb/in. Move the wheel 1" and you compress the spring 0.5". 0.5" on a 1000 lb/in spring is 500lb at the spring perch, which in this case is 250lb at the wheel.
I guess the spring leverage ratio is really just the same relationship from the opposite direction, so you still wind up with having to square 0.5 to get 0.25 which is then "spring rate * leverage ratio² = wheel rate."
With your variable leverage ratio and this bit, it seems like your wheel rate will go from roughly 300 * 0.7² =~ 150lb/in at full droop to 300 * 1.25² =~ 470 lb/in at full bump? Did the 300 lb/in spring recommendation take this into account, or were they based on a 1:1 motion ratio where wheel rate is equal to spring rate?
Are you doing something similar at the front? Seems like the F/R roll stiffness balance is going to vary wildly if the front is closer to constant and the rear is sweeping over those kinds of values.
In reply to Jesse Ransom :
Some pithy thoughts here. I'm going to read through a few more times and maybe do some math before I try and respond fully.
Generally I'm trying to do this math to get something close to a 1:1 motion ratio throughout the suspension travel. Not really in it for the aero considerations.
I originally specc'd out the spring rate assuming a constant 1:1 motion ratio using some maths provided by the folks at Viking Shocks, with the thought that it should work out as long as my actual suspension was geometry was 1:1 at ride height. I've iterated on the geometry a couple of times since I last shared here to get closer to that assumption. I think I'm currently at about 0.9 to 1.05.
I'm still trying to decide on the front. I'll probably start with the stock geometry but perhaps with a coilover instead of the coil + Armstrong damper (like some of the MGB stuff available from a few different companies). I'll have to think harder about F/R roll moving around.
FYI, I am very appreciative of your wall of text.
I hope it helps. I saw your mention that you'd improved the linearity but didn't see how much. That gets your wheel rate variation down to from ~240lb/in at full droop to 330 at full bump. I honestly do not know whether that's enough to cause issues. Even the simple coilover-on-arm setup up front of course isn't perfectly linear, and I assume live axle with the pickups inboard of the wheels is a bit different in heave vs roll, so you may have gotten close enough to 1:1 that it doesn't matter, or is at least on the scale of the other noise. Hopefully it's a fun rabbit hole, and giving it a ponder can't hurt ('til it starts impinging on your impressive rate of build progress).
Nukem said:I could be that guy...
It might be cool to make a part that mates up with some of the Holley parts (lids, snouts).
Stock 5.0 HO Lower, Printed Base to mate with the HO lower, Holley cast throttle body adapter and hat ?
Biggest concern I had with doing a fully fabricated upper was getting the runner transitions from the lower to the plenum nice. If you've got thoughts there I'd love to hear them.
That would be awesome. I'm not sure I understand the concern with the transition. I would think that using a thick enough base plate to provide some smooth radius, or some kind of internal trumpets would both work. I'm sure it could be optimized further, but does it need to be? I'd be looking for inspiration from the 1.8t or other turbo 4 cylinder manifolds.
In reply to Shavarsh :
I'm trying to squeeze in a few more inches of runner length, instead of just going strait from the plenum to the lower part of the intake. Might be unnecessary...
Internal trumpets is a good idea...
Just some ideation ^
Hypothetical printed runner extension to mate up with a fabricated plenum which I haven't sketched up yet.
Cross ram? haha
Edit: It might not be too hard to mill the upper and lower mating surface and shorten the stock intake.
Have you always wanted to do all this to a "B/GT"?
In reply to 759NRNG :
The BGT is for no other reason than it showed up for auction for cheap a few years back and I thought it was cool.
Nukem said:In reply to 759NRNG :
The BGT is for no other reason than it showed up for auction for cheap a few years back and I thought it was cool.
Fair enough carry on
In reply to Shavarsh :
Problem is, I don't have a mill in my basement, but I do have a 3D printer and a welder...
I've got a cross ram design option on the way.
That BBK unit has a huge section joining the two plenums right in the middle, and the throttle body off the the side in usual Ford 5.0 fashion. Any thoughts on if the plenums we're "more separate" (in the extreme, having separate throttle bodies?)
I think that's a fine idea, there are plenty of commercial options for ls, mopar, even stock jaguar v12 (though not crossed), etc that use a dual throttlebody crossram. Or look to the honda j series manifolds for single throttlebody inspiration.
In reply to Shavarsh :
Thanks! I was looking for the J series one, but I couldn't remember what motor it was actually from.
In reply to Shavarsh :
As promised, a Honda J series inspired cross ram:
I made a test part. Hood clearance is perfect, clearance to the fuel rail is not perfect. I think an aftermarket fuel rail and relocating the FPR will solve the issue.
Go for it!!!
Lower part of the intake is fully ported. This was my first time porting. Surprised how quick it went and how much material I could take out.
I've been thinking about this intake all wrong. I need webers!
Or 8 flat slide Mikunis!
In reply to TurboFource :
I think if I found some suitable throttle bodies to do ITB, I'd have to do it. I don't think I actually want the hassle of tuning a bucketful of carbs.
But the look tempts me...
Maybe I'll redesign a bit to use the Weber flange dimensions, to at least leave the option open.
Modern bike TBs may be worth looking at
I've got a set of DCOE-looking TBs waiting to go on the Volvo. Pricey for 4, though.
The 996/997 Porsche family might provide a good throttle body adapter for the dual plenum you sketched.
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