Spamby
Meat Product Toy
Less rotational mass means more power to the wheels and a peppier engine.
GD Bianca ('06 STi), A New Start
- Thread starter Gregroot198521
- Start date
Less rotational mass means more power to the wheels and a peppier engine.
Alin
Diehard Car Enthusiast!
How much less? Any exact numbers?
Grinder34
Track Monkey
Well, rotational mass is a part, but i think stiffness is a larger factor. The polar moment of inertia of a driveshaft is kinda low compared to something with a large diameter, and weight towards the outside, like all 4 wheels. (which in turn, is low compared to the total inertia of the car. Somewhere else i've ranted about lightweight wheels)
But overall weight, stiffness, and rotational weight all factor in. I cant say which is a better bang for the buck. In fact, i bet the roof is already pretty light.
As i said, i just like throwing fuel onto a burning fire to see what happens.
Spamby
Meat Product Toy
True, very true. I think it removes the carrier bearing as well so that helps with flex, etc.
Alin
Diehard Car Enthusiast!
Significant enough that the money for it is worth over something else in the power department?
This is way more advanced than basic bolt ons for the beginner owner, so for example.... How much of a diff would it make compared to stage 1? What about compared to just a CBE?
I don't know all the mathematical science behind it, but for every pound let's say, you're saying about 10 pounds, how much output or performance is translated?
Basically, CF DS or AP and CBE? Let's start there.
This is way more advanced than basic bolt ons for the beginner owner, so for example.... How much of a diff would it make compared to stage 1? What about compared to just a CBE?
I don't know all the mathematical science behind it, but for every pound let's say, you're saying about 10 pounds, how much output or performance is translated?
Basically, CF DS or AP and CBE? Let's start there.
Spamby
Meat Product Toy
I'd say it's more of a down the line kinda thing. Dollar per horsepower is probably not very good considering a protune or ap would yield more impressive results.
CBE probably doesn't yield much if any power.
Maybe around 10 ponies or torque with the addition of the driveshaft. I remember seeing a comparison and they got something like 15 pounds of torque, iirc?
Overall I believe it to be more of a driveability thing rather than a power mod.
Alin
Diehard Car Enthusiast!
Damn... When the time comes to get another STi down the line (which for sure will happen cause I fucking love these cars. 04 again as well!
), I think I'm going to keep motor stock completely! Do on suspension and "driveability" mods to it. What else is considered in the ect. part of modding like the CF DS? Would it be in the same category as clutches and flywheel? ect?
All this activity, lol.
Yeah, a CF driveshaft will raise the COG, but it's more of a driveability thing, than dealing with power increases (I'm thinking a stage 2 or 3 setup is the max power upgrade I'll do on this one), as I'm more interested in keeping the power curve a bit lower for better response in the desert. CF roof may be a "later down the line thing, this is likely the one I'd get: Aerosim CF Roof, or the MooreSport one, which is a little lighter, and has the lip around the edge like stock, but is a lot pricier. Aerosim weighs 5 lbs, MSI one is 4.2 lbs, each chops about 20 lbs off the roof from what I've searched. Only issue is that I will feel very iffy about chopping a hole in something that expensive to install my roof scoop/vent.
CF driveshaft would likely be one from the Driveshaft Shop, as those seem to have the most consistently good reviews I've seen (and I believe they were the lightest setup too). It weighs about 12 lbs, and seems to be about half the weight (slightly less than half, IIRC) of a stock DS. RallySport Direct did a comparison on a stage 2 2011 STi with a slightly heavier PST CF driveshaft, and yielded a 9 HP and 7 ft-lb of torque increase, on winter blend 91 octane at 4300 ft in temps of ~mid-30s.
Oh, and speaking of CBEs, since someone mentioned them, I got a used Borla Hush coming my way, which I'll be doing a little modifying on for my desired exhaust exit point (about 6-10" higher in the bumper, with a hole in the bumper for the exit point), as well as taking care of a leak that occurred on the slip fit section (with some welding after getting everything situated). Also got a JDM hazard switch in the same purchase, about $250 shipped for both.
Yeah, a CF driveshaft will raise the COG, but it's more of a driveability thing, than dealing with power increases (I'm thinking a stage 2 or 3 setup is the max power upgrade I'll do on this one), as I'm more interested in keeping the power curve a bit lower for better response in the desert. CF roof may be a "later down the line thing, this is likely the one I'd get: Aerosim CF Roof, or the MooreSport one, which is a little lighter, and has the lip around the edge like stock, but is a lot pricier. Aerosim weighs 5 lbs, MSI one is 4.2 lbs, each chops about 20 lbs off the roof from what I've searched. Only issue is that I will feel very iffy about chopping a hole in something that expensive to install my roof scoop/vent.
CF driveshaft would likely be one from the Driveshaft Shop, as those seem to have the most consistently good reviews I've seen (and I believe they were the lightest setup too). It weighs about 12 lbs, and seems to be about half the weight (slightly less than half, IIRC) of a stock DS. RallySport Direct did a comparison on a stage 2 2011 STi with a slightly heavier PST CF driveshaft, and yielded a 9 HP and 7 ft-lb of torque increase, on winter blend 91 octane at 4300 ft in temps of ~mid-30s.
Oh, and speaking of CBEs, since someone mentioned them, I got a used Borla Hush coming my way, which I'll be doing a little modifying on for my desired exhaust exit point (about 6-10" higher in the bumper, with a hole in the bumper for the exit point), as well as taking care of a leak that occurred on the slip fit section (with some welding after getting everything situated). Also got a JDM hazard switch in the same purchase, about $250 shipped for both.
^Indeed Al, indeed.
This is the overall plan behind that Borla Hush I bought (also got that JDM hazard light switch in the same deal); it’s used and is leaking at the slip fitting, so that will be getting welded up. I figured this exhaust would be perfect for my plans as I was planning on building something similar, this ended up cheaper ($250 shipped for exhaust and the hazard switch). On to the plan though; this is a rough Paint job of what I want as a result:
It's a rough illustration (think I made the tips a little smaller looking than they really are), but basically there is a way to run exhaust up a little higher in the bumper (little bit of metal removal required, and mounting point changes will be required), and make a little CF lip (the gray oval in the picture) around the exhaust. I'll also have to do some plastic welding to close up the bump on the bottom, but it will remove the exhaust from hitting out on the trail (plus I dig the look after seeing another GD STi with a single tip exiting in the same way - mjfubar on IWSTi).
This should illustrate how much metal will be cut out (and braced):
I'm figuring I should be able to chop out at least 6-10" above (to that spot pointed to in the pic, maybe a little higher; I'd weld a brace across the bottom of the hole (and weld shut the cut if there is more than one layer anywhere)). If it comes down to removal of the bumper bar, I'll make a tube replacement (I was considering making one anyways).
And some parts pics to hold off the pic-hungry, until I can put said parts in:
Braid Wheels:
Killer B Oil Pan, Pickup and Baffle:
TSS Weld-on Strut Mounts and Trailing Arms/TA Mounts:
And a collage of some of the other bigger (read pricier) components:
This is the overall plan behind that Borla Hush I bought (also got that JDM hazard light switch in the same deal); it’s used and is leaking at the slip fitting, so that will be getting welded up. I figured this exhaust would be perfect for my plans as I was planning on building something similar, this ended up cheaper ($250 shipped for exhaust and the hazard switch). On to the plan though; this is a rough Paint job of what I want as a result:
It's a rough illustration (think I made the tips a little smaller looking than they really are), but basically there is a way to run exhaust up a little higher in the bumper (little bit of metal removal required, and mounting point changes will be required), and make a little CF lip (the gray oval in the picture) around the exhaust. I'll also have to do some plastic welding to close up the bump on the bottom, but it will remove the exhaust from hitting out on the trail (plus I dig the look after seeing another GD STi with a single tip exiting in the same way - mjfubar on IWSTi).
This should illustrate how much metal will be cut out (and braced):
I'm figuring I should be able to chop out at least 6-10" above (to that spot pointed to in the pic, maybe a little higher; I'd weld a brace across the bottom of the hole (and weld shut the cut if there is more than one layer anywhere)). If it comes down to removal of the bumper bar, I'll make a tube replacement (I was considering making one anyways).
And some parts pics to hold off the pic-hungry, until I can put said parts in:
Braid Wheels:
Killer B Oil Pan, Pickup and Baffle:
TSS Weld-on Strut Mounts and Trailing Arms/TA Mounts:
And a collage of some of the other bigger (read pricier) components:
DownforceTom
New member
That's definitely fucking awesome.
Didn't expect an actual good response on it after I showed the wife that picture (she thought it looked weird). Definitely makes me happy that other people dig the idea too though, and hopefully I can make it as clean as the idea. Biggest pain will be trying to get the plastiwelding to look clean. Suppose the easiest method would be covering the whole bottom of the bumper with HDPE, and forgo the welding as much as possible, plus it'd be an easy method to run the sheet towards the front of the car, and make a semi-diffuser-like piece that'd be attached to the factory diffuser.
For sure. The +1s (you guys) definitely encourage it more than the naysayers I've encountered. Easy part will be modifying the exhaust, the pain in the ass is going to come when I have my first attempt at plastiwelding since I was a kid (literally, probably 13-16) and I was attaching dinosaur feet to G.I. Joe knock-offs that broke.
I think so, at the very least it'll give me something to do, and it shouldn't cost too much (some Aluminum or HDPE sheet, some 3" stainless tube, some time and some innovation); I'm working out the game plan currently off pictures, so I have a few ideas on how to do this the easiest and cleanest. Pretty sure I'll be able to use the plastic that is part of the stock exit to form the cover-up, just will need some heating, molding and bending to get it right. The borderline useless stock diffuser will likely get some modifying too, thinking in the way of extending it to the sides of the bumper (probably get the design figured out with cardboard, then transfer to some Aluminum or HDPE sheet. I'll have to decide what route it will go (under or over the links and axles in the rear), up to the sills area in front of the fuel tank. Up there I am planning on welding in some angle iron pieces for some protection (like sliders on other off-road vehicles) with triangle jack points too, and these would also be good points to install more sill protection (almost like running bars, but tucked close to the body).
Most of this is just thinking "out-loud", trying to arrange my ideas as best as possible.
Most of this is just thinking "out-loud", trying to arrange my ideas as best as possible.
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