[CQquattro]

Some more progress, got the engine and trans positioned where they need to be, and started mocking up the intercooler and radiator location. They will be angled with an exhaust vent coming out of the hood.

Also fabbed up a "plug" for a carbon intake plenum I'll be making.

 

[Chopped]

I got so much greif when I mentioned this swap for a race car. Glad to see someone thinks the way I do. I'll be watching this one!

 

[CQquattro]

Vehicle dynamics question, any insight?!

Last night I started mocking up the placement of the new steering rack, I'll be using one from a 240sx. It is getting mounted to the audi subframe, right about where the OEM mounts are for the transmission. There is a hump in the RB oil pan that allows the steering rack to sit in this location (stock location for RB). However, the subframe gets in the way of the tierods during suspension travel & full lock. If I install a 0.5" spacer between the frame and subframe (moving the subframe down 0.5") I get enough clearance. My question is, what happens to my suspension geometry? It's obvious the control arm bushings will be moved closer to the ground, and that will change the resting angle of the control arm, but is that it? I'm trying to figure out if my center of gravity is lowered or raised? I believe the car will maintain the same ride height, is the control arm angle the only thing changing?

 

[dalspaugh]

They way I see it, yes. resting angle is the only change I can see. The ball joint at the bottom of the spindle will take the extra angle up. I guess if you want to get really precise, it will actually change the camber slightly (positive) because the arm is a fixed length, and you are moving it in an arch around where the ball joint wants to be.

I think that made sense...

 

[CQquattro]

Yes I agree, camber will change ever so slightly since the ball joint to bushing angle will be slightly different (thinking triangles and hypotenuse length) If anything else I believe my cg will be slightly lower but probably negligible. I had a friend try to convince me my cg would be raised, since the car is getting raised .5", I knew that couldn't be right!

 

[dalspaugh]

Yes I agree, camber will change ever so slightly since the ball joint to bushing angle will be slightly different (thinking triangles and hypotenuse length) If anything else I believe my cg will be slightly lower but probably negligible. I had a friend try to convince me my cg would be raised, since the car is getting raised .5", I knew that couldn't be right!

haha yeah I guess CG would be lowered ever so slightly because you are adding weight down low.

 

[pkw]

read about "roll center"

 

[CQquattro]

yes pkw! Been a couple years since engineering classes and I already overlooked roll center, lol.

For others that are interested, here is a good article about roll center. http://www.motoiq.com/MagazineArticles/ ... enter.aspx

at this point I really cant do much to determine how my roll center will change when I lower the inner control arm pivots, as I've changed so many other things (engine is heavier, but also farther back and lower than factory.) The good news however is that if i lower my inner control pivots and it has an adverse affect on handling, i can likely change the outer ball joint pivot location.

 

[Chopped]

Do you have the entire front sub and suspension from a 240? Might just use it all?

 

[The German]

^ without knowing that the 240 front suspension looks like, this sounds like the best plan to me. Moving the control arms, rack, tie rod pivots, etc. around with no plan or calculation you are 99% likely to end up with something that handles like poo. There are lots of decent suspension modeling programs out there- I strongly suggest reading, modeling, and iterating electronically before cutting and welding. It would be a shame to put all this work in and wind up with something that drives like a tractor.

 

[pkw]

FWIW back when the 240sx first came out, I declared it a good handling car that just needed more engine. That was a long time ago, but I bet I would still respect one. Might work very well to use that stuff. one concern is how well will the front 240 compliment the rear Audi. If they do not do the same thing at the same time or one end does it before or after it should, It is not so great. It makes a car boring or a widow maker....worst case.

 

[alxdgr8]

I'd mod the crossmember to clear before spacing the crossmember down. If anything, you want the control arm mounts to be moved upwards (not downwards) if you are lowering your car at all since that already pushed the control arm angle towards horizontal.
Best bet would probably be a custom tubular subframe.

 

[CQquattro]

the 240 front crossmember, control arms, knuckles etc. won't work as they are designed for rwd, no room for front axles.

I could use front end components from an r33/r34 GTS, but the trouble I foresee is even more suspension modifying. The r33/34 uses a double wishbone style front end, while far superior to the mcpherson style I would need to weld on upper control arm mounts to the body.

Last night I spaced the subframe down 0.5", at ride height my control arm still has some angle to it before reaching parallel with the ground. Also did some quick roll center drawings, honestly it looks like it'll work just fine. Worst case scenario I can also drop the outer ball joint 0.5" too.

Also looks like my bumpsteer will be very minimal, I plan on fabbing a bracket that bolts to the knuckle, in order to get the outer tierod end closer to the lower ball joint location. I attached a picture of a front knuckle from a 1998 Impreza, if you look where the tierod bolts onto it, thats about where I need to put mine.

 

[dalspaugh]

My vote would be to do it and take notes as you go. Once the car is running driving you'll have time and a better idea on what to modify for a rev 2. Getting the drivetrain figured out is plenty for the first go at it even if it doesn't handle perfectly.

my $.02

 

[CQquattro]

Was able to get a damaged race wheel and out dated tire from work, just had to see what it looked like. That's a 325 tucked under there, ha!

 

[The German]

the 240 front crossmember, control arms, knuckles etc. won't work as they are designed for rwd, no room for front axles.

I could use front end components from an r33/r34 GTS, but the trouble I foresee is even more suspension modifying. The r33/34 uses a double wishbone style front end, while far superior to the mcpherson style I would need to weld on upper control arm mounts to the body.

Last night I spaced the subframe down 0.5", at ride height my control arm still has some angle to it before reaching parallel with the ground. Also did some quick roll center drawings, honestly it looks like it'll work just fine. Worst case scenario I can also drop the outer ball joint 0.5" too.

Also looks like my bumpsteer will be very minimal, I plan on fabbing a bracket that bolts to the knuckle, in order to get the outer tierod end closer to the lower ball joint location. I attached a picture of a front knuckle from a 1998 Impreza, if you look where the tierod bolts onto it, thats about where I need to put mine.

You should look at a MK3 VW knuckles - you may be able to use them as-is or with slight modification. Worth looking at... I wonder if MK3 dampers would plug right in as well.

 

[Pete82]

nice to see something different being done to one of these

 

[Chopped]

Yep. Motorgeek was near death before this tread.

 

[CQquattro]

More work gettin done, decided to cut out the factory strut towers and make my own to accommodate some caster/camber plates. Starting on the passenger side

 

[CQquattro]

Some more progress. Got the top plate welded in for the new passenger side strut tower, waiting on the arrival of my new turbo and steering rack before I can begin the driver side strut tower/firewall. Glad to see the pedal assembly I selected will fit very nicely.

Also got one of the valve covers powder coated, and finished up the "plug" for the mold of my carbon intake plenum.