LocostUSA.com :: View topic - Tongboy's F20C powered Autox & track toy

You say that the S2K diff was ~60lb and that the Miata diff was ~62lb, but you did not have that mounting bracket on the S2K diff in the picture. Is said bracket really less than the ~2lb difference or does the Miata diff win on weight in the end?

Tom...

Man, you're moving right along. I'm excited to see another s2000 build get ahead of me so I have something else to copy...err think about

One thing that I had wondered about is in mounting the engine/trans and differential. Is it OK to go ahead and solid mount them? I have no idea how much vibration you'll get as the driver, but I'm probably OK with a little discomfort. What I was concerned about it the engine and diff itself. They come with some pretty cushy motor mounts, which will kind of let everything mush all around, but how much of that is actually necessary to protect those aluminum connection tabs from fatigue? When I was a co-op at Delphi there was a whole division devoted to shock/strut mounts and engine mounts with all kinds of different combinations of different rubber and shims and things moulded into them. I know a Buick is supposed to drive like a marshmallow, but certainly some of that effort was more than just nice to have. On the other hand, I'd love to be able to keep the engine from squishing all around and doing who knows what to the exhaust hanging out the side. If anyone has any prior experience I'd like to hear what you think.
Keep up the good work!
Sam

Why not incorporate the OEM mounts into your chassis some how ?

Steve

I'm not comfortable with the single upper arm because it places the lower arm in bending under acceleration and braking. To find out if what you've is acceptable, try this:

Isn't that the stock Miata design?

I'm not comfortable with the single upper arm because it places the lower arm in bending under acceleration and braking. To find out if what you've is acceptable, try this:

1. Assume a 1500 lb car and driver.
2. One G acceleration.
3. Divide force by two because there's two rear wheels.
4. Divide by three because the top upright pivot is about 3x higher than the lower arm.

This gives 1500 lbs/2/3 = 250 lbs.

So, using whatever means necessary, push or pull the top of the upright fore or aft and measure the deflection. Also keep in mind that any deflection will cause rear bump-steer. I recommend making the upper link a true A-arm.

[edit] since the lower arm sets toe, there shouldn't be any bump-steer, but regardless, having the lower arm assembly bend/flex with power and braking is going to be trouble.

ordered rollbar and supporting parts from rollcage components - FANTASTIC price. I'm looking forward to receiving those parts after hearing good things from other members here.

Author:	Tom17 [ February 13, 2012, 1:08 pm ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
You say that the S2K diff was ~60lb and that the Miata diff was ~62lb, but you did not have that mounting bracket on the S2K diff in the picture. Is said bracket really less than the ~2lb difference or does the Miata diff win on weight in the end? Tom...

Author:	Tongboy [ February 13, 2012, 4:47 pm ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
Tom17 wrote: You say that the S2K diff was ~60lb and that the Miata diff was ~62lb, but you did not have that mounting bracket on the S2K diff in the picture. Is said bracket really less than the ~2lb difference or does the Miata diff win on weight in the end? Tom... it's true - with the axle cups and the bit more provisioning for mounting the s2k diff probably does weigh more than the miata diff. I'm not sure how much extra weight the LSD in the miata diff would add but they are going to be fairly close in final weight. the worthwhile difference for the few more lbs of the s2k diff is that they are designed & built from the factory to deal with the higher power output of the motor. I'll be holding onto the miata diff anyways in case I want to change the final drive to the 4.3 that it has. carguy123 wrote: It doesn't. BTDT aww, don't tell me that! It looks like i'm right in line with the better output s2k headers that are offered and they show some pretty substantial mid-range gains when the vtec engagement point is adjusted down (aka when emissions don't matter) I think the vtec point makes a bigger difference than the headers do but I wont know until I get on the dyno... do you have a thread with your testing? i'd love to check it out

Author:	carguy123 [ February 13, 2012, 4:55 pm ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
I'll look for the dynos, but we got much better results with adjusting VTEC and A/F ratios than anything we did to the headers. IIRC we lost about 7 hp total and and didn't fatten the mid range band enough to make us think it was real and not operator error or different temps on the day of the dyno runs.

Author:	S27sam [ February 14, 2012, 10:26 pm ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
Man, you're moving right along. I'm excited to see another s2000 build get ahead of me so I have something else to copy...err think about One thing that I had wondered about is in mounting the engine/trans and differential. Is it OK to go ahead and solid mount them? I have no idea how much vibration you'll get as the driver, but I'm probably OK with a little discomfort. What I was concerned about it the engine and diff itself. They come with some pretty cushy motor mounts, which will kind of let everything mush all around, but how much of that is actually necessary to protect those aluminum connection tabs from fatigue? When I was a co-op at Delphi there was a whole division devoted to shock/strut mounts and engine mounts with all kinds of different combinations of different rubber and shims and things moulded into them. I know a Buick is supposed to drive like a marshmallow, but certainly some of that effort was more than just nice to have. On the other hand, I'd love to be able to keep the engine from squishing all around and doing who knows what to the exhaust hanging out the side. If anyone has any prior experience I'd like to hear what you think. Keep up the good work! Sam

Author:	carguy123 [ February 14, 2012, 11:11 pm ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
Ultralites (S2000 powered) seem to have settled on Delrin/or other hard isolator mounts or solid mount. Driven hard, and you know you will or you wouldn't be using the S2000 engine, they've had some minor issues with the diff mount unless you contain it somehow. So very soft mounts are probably not the best idea but Energy bushings on up to solid mount is probably your safest bet.

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Tongboy's F20C powered Autox & track toy http://locostusa.com/forums/viewtopic.php?f=35&t=13245	Page 3 of 15

Author:	Tongboy [ February 16, 2012, 3:44 am ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
S27sam wrote: Man, you're moving right along. I'm excited to see another s2000 build get ahead of me so I have something else to copy...err think about One thing that I had wondered about is in mounting the engine/trans and differential. Is it OK to go ahead and solid mount them? I have no idea how much vibration you'll get as the driver, but I'm probably OK with a little discomfort. What I was concerned about it the engine and diff itself. They come with some pretty cushy motor mounts, which will kind of let everything mush all around, but how much of that is actually necessary to protect those aluminum connection tabs from fatigue? When I was a co-op at Delphi there was a whole division devoted to shock/strut mounts and engine mounts with all kinds of different combinations of different rubber and shims and things moulded into them. I know a Buick is supposed to drive like a marshmallow, but certainly some of that effort was more than just nice to have. On the other hand, I'd love to be able to keep the engine from squishing all around and doing who knows what to the exhaust hanging out the side. If anyone has any prior experience I'd like to hear what you think. Keep up the good work! Sam Thank you sir, I've seen your build - keep at it! you're a brave man using a lot of the s2k parts. I looked at a lot of them and didn't end up using most of them but I can see how most of them can be used depending on your cars intended purpose. So further stewing on the front suspension leaves me loving the way modernbeat did/redid his previous cars suspension based around the fiero/chevette parts and basically using bolts and heim joints. So I went down to the junkyard and picked up a set and cleaned them up. comparison of the fiero & the miata spindle I'll run wilwood dynalites for calipers and use the hawk machine bracket to fit them up - I'm hoping I can use a better solution for hubs than the stock chevette integrated rotor setup but that will be a functional setup to start with if need be. tomorrow i'll start on fabricating a-arms, hurray! (I think)

Author:	boostboost [ March 2, 2012, 12:29 am ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
Why not incorporate the OEM mounts into your chassis some how ? Steve

Author:	Tongboy [ April 17, 2012, 2:37 pm ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
boostboost wrote: Why not incorporate the OEM mounts into your chassis some how ? Steve I don't want the deflection of the stock mounts for a car intended for race duty primarily. It's time I update this thread, normally i'm on top of my build threads but I spend so much time thinking with this project that I don't think to pick up the camera and snap some pics. Progress has been happening albeit at a much slower pace than I'd like. The fabrication of the headers is all but done now, i'm very happy with them I've got my coast fab racing muffler ready to go on - just needed to get the rear axle area setup so that we could determine where to direct the exhaust away from. Got my seat mounted so I can work on the steering & pedal cluster - picked up seat mount brackets from another forum member here holy cow sitting in that seat makes me want to race something now that the weather is getting nice, those parking lot cones are calling my name! I've spent the last few days working on the rear suspension. I"m happy with how it's turned out - with with the lower H-beam and upper camber arm to provide better shock room than the more common miata setup- I don't expect i'll have any issues but we'll see I had some flat mounts laser cut that i'm really liking - the fit snug around 1x1 square tube and let me pretty easily get adjustment in mounting locations. I used them here to allow toe adjustment as well as camber curve adjustment on the upper mounting location My fabricator convinced me to go inboard on my front suspension so I had to design around that change. I had some plates cut for that as well and now I need to get back to fabricating the front control arms to get all of that in place.

Author:	KB58 [ April 17, 2012, 4:21 pm ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
I'm not comfortable with the single upper arm because it places the lower arm in bending under acceleration and braking. To find out if what you've is acceptable, try this: 1. Assume a 1500 lb car and driver. 2. One G acceleration. 3. Divide force by two because there's two rear wheels. 4. Divide by three because the top upright pivot is about 3x higher than the lower arm. This gives 1500 lbs/2/3 = 250 lbs. So, using whatever means necessary, push or pull the top of the upright fore or aft and measure the deflection. Also keep in mind that any deflection will cause rear bump-steer. I recommend making the upper link a true A-arm. [edit] since the lower arm sets toe, there shouldn't be any bump-steer, but regardless, having the lower arm assembly bend/flex with power and braking is going to be trouble.

Author:	bremms [ April 17, 2012, 8:43 pm ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
I'm having some serious issues with motor mount deflection. The volvo motor mounts are squidgy at best and I can feel and see a lot of motor deflection. I'd like to use the E36 M3 mounts. A lot of the volvo guys use XKE mounts.

Author:	carguy123 [ April 17, 2012, 9:07 pm ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
KB58 wrote: I'm not comfortable with the single upper arm because it places the lower arm in bending under acceleration and braking. To find out if what you've is acceptable, try this: Isn't that the stock Miata design?

Author:	gotboost348 [ April 18, 2012, 12:05 am ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
miata have a a arm setup.and with the abuse i think is a cheap insurance to do a a arm setup

Author:	cheapracer [ April 18, 2012, 12:50 am ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
carguy123 wrote: Isn't that the stock Miata design? They run a 'T' upper arm http://locostusa.com/forums/viewtopic.php?t=566

Author:	Tongboy [ April 30, 2012, 2:19 am ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
KB58 wrote: I'm not comfortable with the single upper arm because it places the lower arm in bending under acceleration and braking. To find out if what you've is acceptable, try this: 1. Assume a 1500 lb car and driver. 2. One G acceleration. 3. Divide force by two because there's two rear wheels. 4. Divide by three because the top upright pivot is about 3x higher than the lower arm. This gives 1500 lbs/2/3 = 250 lbs. So, using whatever means necessary, push or pull the top of the upright fore or aft and measure the deflection. Also keep in mind that any deflection will cause rear bump-steer. I recommend making the upper link a true A-arm. [edit] since the lower arm sets toe, there shouldn't be any bump-steer, but regardless, having the lower arm assembly bend/flex with power and braking is going to be trouble. I appreciate the math - I did have fears about it and I put about 200lbs of effort into it with just the tack welds on it and measured a very small amount of deflection (around a 32nd.) I am going to go to an upper a-arm though to prevent any unplanned geometry changes that might be hard to track later on. In the meantime I've wrapped up the front end suspension - I put the as-built back into my suspension program and it came out looking great, no bump steer when it's all setup correctly and good camber curves as well as right about 1:1 motion ratio with the inboard shocks and their relatively short motion range. Also got my first set of wheels - 13x10 aero wheels - 5" backspacing in the front (still leaves a lot of scrub radius with the fiero spindles) and 4" in the back. threw some 22x9x13s on - I'll probably use these for regional autox and some track days to get the car setup because I can get them for sub 100/4. they are larger in diameter than the ideal tires to run for autox but they'll work in a pinch and i've got enough suspension height adjustment range to run them satisfactorily front and back. To get the radiator in the proper place I needed to figure out the nose situation. ordered rollbar and supporting parts from rollcage components - FANTASTIC price. I'm looking forward to receiving those parts after hearing good things from other members here.

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Author:	JackMcCornack [ April 30, 2012, 5:12 pm ]
Post subject:	Re: Tongboy's F20C powered Autox & track toy
I'm with Kurt re the upper control arm. It doesn't have to be a single welded arm, though; you could just add a radius rod (tube, really, but that's what they call 'em) to what you already have. Tongboy wrote: ordered rollbar and supporting parts from rollcage components - FANTASTIC price. I'm looking forward to receiving those parts after hearing good things from other members here. I'll give a +1 for Roll Cage Components--the's who I use. When you order a roll bar from Kinetic, it ships straight to you from Roll Cage Components, 'cause there's no good reason to add to the expense by shipping it to Oregon first. The guy (Jim Whitley) does great work at a great price, and he must buy a lot of tubing to keep his costs so low.