I think it's quite possible, and with minimal mods to the space frame also.
VW based 6 speed from EIP: $5K 500 HP Chevy: $5K Complete suspension replacement (mostly rear): <$5K (this product isn't available yet, but wait until I learn to weld...) Which leaves $5K for brakes, wheels and tires.
I'm confident that the suspension can be modded, with no cutting of chassis metal, to fit 17x10 rear wheels. These can fit 275-305 width tires.
Splurge a little bit and buy RaceLogic traction control and you won't have to worry about breaking the tires loose... just keep your foot planted and shift.
with strut adaptors and very minor frame mods the 84-87 rear suspension can fit 335/35/17's and look stock
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08:28 AM
toddshotrods Member
Posts: 1177 From: Columbus, OH, USA Registered: Aug 2004
I started out building a Pro-Street car but got bored with the one-dimensional performance idea. I was working on adapting it for more rounded performance but the gang here convinced me to to go back to the mid-engine layout. As I said, I like the space frame so I decided to just table this whole project and start over with another Fiero. This car ends up being a parts/research car.
edited for typos ------------------ Todd Perkins - the member formerly known as "perkidelic" todd's hot rods
[This message has been edited by toddshotrods (edited 12-29-2004).]
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09:47 AM
Will Member
Posts: 14252 From: Where you least expect me Registered: Jun 2000
Originally posted by gusshotrod: WIll: Polor moments are measured from the cg of the car, not the center of the car. The closer all items are to the cg, the lower the pm.
My point was that any time you spread mass out over a larger area, you increase MOI. That's exactly what you're doing with a longitudinal driveline. You're spreading more mass out over a larger area. You're going to increase MOI over a transverse driveline. And waste HP in a lossier gearbox.
quote
What's wrong with the stock suspension? Front instant center changes too quickly with suspension movement, camber gain not right, roll steer, slow steering, small bearings, small brakes, small ball joints, durometer of rubber bushings, weak sway bar, bad shocks, lack of or difficult adjustment, scrub radius, anti-dive.
Of all these items, only roll centers, camber changes and anti-dive[squat] require geometry changes. The rest are relatively small items that don't require a redesign. And I think that deciding to scrap everything and redesign from the ground up is a bit premature. For instance, pro-dive can be dealt with using wedges between the suspension crossmember and chassis. You don't want any anti-dive on a supercar anyway. Have you ever played with the factory geometry in an analysis program? Changing the height of pivots a small amount can have an ENORMOUS affect on the roll center behaviour. You might be surprised at the improvements that can be made with relatively minor changes...
Slow steering can be fixed with a faster rack or a steering quickener. Small bearings have already been dealt with; Buy a set of aluminum lowering knuckles from Street Dreams.... they use '88-'92 Camaro Z28 bearings. Scrub radius/kickback can be neutralized with wheel offset. Small ball joints? I've never heard of anyone breaking them due to excessive performance... I have heard of them coming apart from just being worn the F#$% out due to poor maintenance... Everything after and including sway bar bushings is just tuning... If you want stiffer sway bar bushings, buy a set of pillow block sway bar mounts from Gerald Storvik. There are a number of aftermarket products to increase the tunability of the stock suspension. I think that with monor mods like slotted ball joints and alignment shims instead of factory camber washers, the adjustability of the stock suspension is a hell of a lot better than a lot of what's on the market. I have eccentric UHMW front lower control arm bushings and slotted ball joints. I can get -1.5 degrees of camber at each front wheel easily. On the rear, I have UHMW bushings and Koni struts and I can get -1.75 degrees easily. The GM suspension isn't bad from an adjustment perspective.
What have you done with your Fiero? Have you ever tried to see how far the factory design can be taken?
(Or you could start with an '88 and most of your complaints would be moot)
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Rear suspension basically the same. Also, transverse transaxle will not allow the engine to be lowered and still maintain minimal angle on the axle/cv joints. The input to the transaxle is above axle height, on the Porsche it is several inches below axle height.
If you're using an engine/trans adapter plate, lowering the engine is relatively easy. When designing the plate, rotate the engine back relative the the transmission. When installing, mount the engine vertically. The transaxle ends up rotated forward and the engine is significantly lower. The CV angles haven't changed.
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Originally posted by toddshotrods: Even the 88 redesign is a sports car suspension which was designed to be a cost effective upgrade. Cost ruled over performance.
You're right about one thing... cost ruled over performance. The suspension used in '88 was originally supposed to be on the car when it was introduced in '84. The bean counters said that the car had to use off the shelf components. The car was redesigned for the early suspension. The '88 suspension was what was originally supposed to go on the car, and was a FAR superior design to what ended up going on the car...
I think that the space frame is basically a sound platform for supercarness. After all, we all already know that it has tremendous capacity to absorb punishment and keep the driver alive. That's a testament to the engineering that went into it. I don't think I'd modify it much... maybe just a cage and a few very selective chassis stiffening braces, like an X-brace over the top of the engine bay.
I think that the vast majority of the Fiero's deficiencies can be overcome with careful and creative applications of small changes. The idea "It sucks so let's scrap the whole thing and start over" is like giving up to me. I think that most of the engineering and performance potential is already there... it just needs some careful and creative work to be released.
I associate the factory tub with fieroness. If it's not on the factory tub, it's not a Fiero. What you and gusshotrod are discussing will have so little of the factory tub left that they'd no longer be Fieros, IMO.
------------------ Turn the key and feel the engine shake the whole car with its lope; Plant the gas pedal and feel in your chest neither a shriek nor a wail but a bellowing roar; Lift and be pushed into the harness by compression braking that only comes from the biggest cylinders while listening to music of pops and gurgles. Know that you are driving an American V8. There are finer engines made, but none of them are this cool.
Luck, Fate and Destiny are words used by those who lack the courage to define their own future
[This message has been edited by Will (edited 12-29-2004).]
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10:52 AM
Will Member
Posts: 14252 From: Where you least expect me Registered: Jun 2000
with strut adaptors and very minor frame mods the 84-87 rear suspension can fit 335/35/17's and look stock
I'm designing strut blocks that will work in a similar fashion, but less so. I don't like having to cut the chassis that much. I think that with 1" strut blocks, rather than the 2+" block shown, 17x10 wheels and 275/40-17's would work. Also notice, those are not Fiero struts... they have been borrowed from some other app.
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10:55 AM
toddshotrods Member
Posts: 1177 From: Columbus, OH, USA Registered: Aug 2004
Originally posted by gusshotrod: ...Any available automatic transaxle is heavy and results in the engine five+ inches too high with too much rear weight bias...
...The input to the transaxle is above axle height, on the Porsche it is several inches below axle height...
I know this isn't the most scientific method to compare them, but since i don't have a Porsche tranny here... I lined up the exhaust bolts and the bottom of the oil pans, but the transverse pic is off because it is at an angle. Does anyone have a straight side view of a Fiero tranny bolted to an SBC (for the sake of comaparison). Also, is the G50 transaxle different than this one? Is its axle center line located higher in the case, relative to the input centerline?
In this example, the difference only seems to be around an inch or so. I know moving the weight of the engine down an inch is a lot, but you also have to weigh the advantages against the cost for the intended purpose.
------------------ Todd Perkins - the member formerly known as "perkidelic" todd's hot rods
I'm designing strut blocks that will work in a similar fashion, but less so. I don't like having to cut the chassis that much. I think that with 1" strut blocks, rather than the 2+" block shown, 17x10 wheels and 275/40-17's would work. Also notice, those are not Fiero struts... they have been borrowed from some other app.
avoiding frame modification is always nice - 295's would also be nice
[This message has been edited by Kohburn (edited 12-29-2004).]
I'm designing strut blocks that will work in a similar fashion, but less so. I don't like having to cut the chassis that much. I think that with 1" strut blocks, rather than the 2+" block shown, 17x10 wheels and 275/40-17's would work. Also notice, those are not Fiero struts... they have been borrowed from some other app.
Nice. It also appears that you could get some lowering effect from this... Can you think of anything that would stop this approach from working on 88's as well?
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11:26 AM
toddshotrods Member
Posts: 1177 From: Columbus, OH, USA Registered: Aug 2004
Originally posted by Will: ...I associate the factory tub with fieroness. If it's not on the factory tub, it's not a Fiero. What you and gusshotrod are discussing will have so little of the factory tub left that they'd no longer be Fieros, IMO.
No argument from me on that one. My project has never been about preserving the essence of the Fiero, it has always been about what I see in the basic design of the car. More importantly, it has always been about what I want to drive down the road in. In fact, when I finish only those who ask or read will even realize that the "skeleton" is Fiero-based. Gusshotrod seems to at least be interested in preserving the look of the Fiero though.
My project starts with a question. What if another division or manufacturer saw the potential in the "factory tub" and struck a deal with Papa GM for P-body space frames to build their own mid-engine American supercars? So, I agree my car will not technically be a Fiero when finished, but it will be a close cousin
Will is probably right, in saying there is a lot to be gained with small incremental advances. I just hope that the person/people who try it that way put as much thought into what they are doing as he does. It's easy to slap a big motor and a few performance parts on a car, but it takes a bigger effort to properly design a safe vehicle. There is a guy on another board I frequent who works for Art Morrison (street rod company). He was able to develop a Mustang II based frame for Tri-Five Chevies that makes them handle like sports cars. He did it by doing what Will said - a little tweaking here and there. The car was tested and delivered on its promise - sports car handling and feel.
The important points here are this guy is really good at suspension theory and design. He designs salt flat and road race cars on the side, and hopes to go into business on his own specializing in those areas someday. In the end, while he was pleased with the results he was not content and his biggest gripe was the compromises he had to make for the MII front suspension. I made mental note of the fact that if it had been his car he would still not have been satisfied with the end result - after all that work. In the same amount of time, and with the same effort he could have designed a new suspension that would have scratched his itch.
I know me, and I don't want to be left with that "I wish I woulda" feeling so I know what I have to do. It's all in what YOU the owner and/or builder wants in the end.
------------------ Todd Perkins - the member formerly known as "perkidelic" todd's hot rods
I'm glad to see that this discussion made a signifigant turn towards suspension. Too many of the initial posts were talking 1/4 mile and 0-60 acceleration. Although these are important measures in the performance of any car - does anyone really think that modern supercars (such as the noted Enzo) are built for straight line performance? Not a chance - these are roadgoing race cars designed to corner. Glad to see that become a focus here
Originally posted by Will: I'm designing strut blocks that will work in a similar fashion, but less so. I don't like having to cut the chassis that much. I think that with 1" strut blocks, rather than the 2+" block shown, 17x10 wheels and 275/40-17's would work. Also notice, those are not Fiero struts... they have been borrowed from some other app.
Hmm... So just moving the strut over an inch allows 10" wheels and almost 11" tires? Can the same thing be said for the stock fiero struts? (Or will somebody have to find the right app struts to install?)
I doubt just moving it over will allow all that. You still have to worry about the spring perch. I'm sure he intends to do some coilovers as well as other things.
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02:42 PM
PFF
System Bot
ryan.hess Member
Posts: 20784 From: Orlando, FL Registered: Dec 2002
I doubt just moving it over will allow all that. You still have to worry about the spring perch. I'm sure he intends to do some coilovers as well as other things.
Sorry... yeah, I assumed coilovers.
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02:43 PM
toddshotrods Member
Posts: 1177 From: Columbus, OH, USA Registered: Aug 2004
I agree MinnGreenGT, and would just like to add to what you said. Gusshotrod pointed it out on the first page too, it's still about more than numbers - even if those numbers pertain to sports car handling (i.e. skidpad, slalom, etc.) The point is to design a car that you simply do not want to stop driving. A trip through your favorite twisty road should leave you with a craving to do it again, not exasperation from fighting an unruly beast that produces good numbers.
The numbers are still important though because they give you a reference point. Is your car completely composed and confidence inspiring at 100mph or 200mph? Does it transistion well in a slalom at 50mph or 70mph. Does it barely eek out .95g on the pad at the verge of self-destruction, or put down a 1+g "lap" without breaking a sweat? Does it blast to 60 in six seconds and then stop on a dime, or to 100 in 6 and hand over nine cents change. What is your desired heart rate at the end of each test? These things help the owner/builder identify his or her goals and then chose a course of action to effectively realize them.
Now, where did I put that reciprocating saw...
------------------ Todd Perkins - the member formerly known as "perkidelic" todd's hot rods
[This message has been edited by toddshotrods (edited 12-29-2004).]
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02:54 PM
cooguyfish Member
Posts: 2658 From: Hamilton, OH, USA Registered: Mar 2002
I agree MinnGreenGT, and would just like to add to what you said. Gusshotrod pointed it out on the first page too, it's still about more than numbers - even if those numbers pertain to sports car handling (i.e. skidpad, slalom, etc.) The point is to design a car that you simply do not want to stop driving. A trip through your favorite twisty road should leave you with a craving to do it again, not exasperation from fighting an unruly beast that produces good numbers.
The numbers are still important though because they give you a reference point. Is your car completely composed and confidence inspiring at 100mph or 200mph? Does it transistion well in a slalom at 50mph or 70mph. Does it barely eek out .95g on the pad at the verge of self-destruction, or put down a 1+g "lap" without breaking a sweat? Does it blast to 60 in six seconds and then stop on a dime, or to 100 in 6 and hand over nine cents change. What is your desired heart rate at the end of each test? These things help the owner/builder identify his or her goals and then chose a course of action to effectively realize them.
Now, where did I put that reciprocating saw...
I new there was a reason i'm gald you're back, you just hit everything i want with my car... now get to work and make something that is replicatable so i can have it too
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03:55 PM
Will Member
Posts: 14252 From: Where you least expect me Registered: Jun 2000
Originally posted by cooguyfish: I new there was a reason i'm gald you're back, you just hit everything i want with my car... now get to work and make something that is replicatable so i can have it too
That's a big reason I want to go with incremental tweaks and minor space frame mods... I can build them and sell them and put a fleet of Fiero supercars on the road.
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05:24 PM
R Runner Member
Posts: 3696 From: Scottsville, KY Registered: Feb 2003
Just my opinion, but I don't think there's anything worth saving from a Fiero chassis if you want to get serious about this. Front and rear suspension layout, steering, etc are all not up to the task. Unibody is quite strong but heavy and cg is too high. Any available automatic transaxle is heavy and results in the engine five+ inches too high with too much rear weight bias. Goals should be low polar moment, low CG height, correct suspension geometry/springs/shock rates/roll rates and roll couple, good sprung/unsprung weight ratio, useful gear ratios, power to weight, sticky tires and good aero. And it should't break. Just running tens in the quarter is not my idea of a supercar, neither is +1G on a skidpad. You can make any car do that. I thnk is about how the car transitions, how it behaves on the road with all variables factored in. Doesn't do much good to go fast if a bump in the road puts you in the next lane, or a sudden lane change requires a death grip on the steering wheel.
Amen, Brother.....
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06:31 PM
R Runner Member
Posts: 3696 From: Scottsville, KY Registered: Feb 2003
1. Steal Pauls (Roadrunner) car. 2. Add 100 lbs street equipment and some street tires. 3. Blow 'em ALL away.
( Thank you !!!) Actually, that is the in the grand plan after the wide body and aluminum wheels (say good bye to 40 lb. of rotating mass and unsprung weight!) The clutch will be tough to manage and C12 is a bit pricy for street use, but what the heck, it would be great for cruising and you only live once! Here hemi, hemi, hemi....
Paul
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06:40 PM
R Runner Member
Posts: 3696 From: Scottsville, KY Registered: Feb 2003
I suck at using the quote function so i'll try to paraphrase (I can't spell either ). You mention making small incremental improvements. Yes, a great car can be made that way. I have done many if not all of the mods you mentioned to an 87 GT. I ran it in SOLO II and a few other events. Compared to my tube chassis, COMPLETELY different. We at talking about two different cars here. Forget the motor. If I put a stock 2.8 in my race car, (with the same weight and location of CG which I know is not realistic) and put stock wheels on it (and we will pretend that this dies not effect the geometry, dampening, and tuning) the tube chassis makes a huge difference in performance. I feel a very tiny bit of flex in the race car. In the GT with a stiff suspension, I would regulary hear the fiberglass roof creak and (since a small crack had already started) I actually cracked the "A" pillar in half. I inturn made subframe connectors and welded them to the frame. (I'll give up the prints free if some one wants them). This made a big improvement. My point is... I'm long winded.... no wait.... the stock space frame is too soft to make major suspension upgrades to even if major is defined as one brick at a time. Fine for the street, not for the track.
As for the CG, I beg to differ on the longitudinal setup. I can tell you what mine is and let you compare. The center of mass of the tranny/engine is about 16" in front of the rear axle which is in the stock location. If you compare the SBC setup transversly mounted, I believe it to be further rearward. As for the CG height, I am running the 930 tranny inverted which puts the input shaft below the axle. My engine pan (dry sump) a mere 4.5" off the ground. It is only about 1/8" above the bottom of the chassis. Here is a picture for reference...........
Just want to clear up some misinformation. Todd: The G50 is run inverted which puts the axle centerline 2.5 inches above the crank centerline. WIth a 26 in. tire, this puts the crank centerline 10 in. above the deck with zero axle angularity. WIll: I don't think you've quite got the concept down regarding polar moments. To reduce pmi, move everything closer to the GG. Running the numbers quickly, looks like about 30% reduction in pitch, about 50% reduction in roll (longitudinal vs. transverse).
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08:16 PM
toddshotrods Member
Posts: 1177 From: Columbus, OH, USA Registered: Aug 2004
Yeah that's nice Paul. The pic I have obviously didn't have the transaxle inverted - make sense what gusshotrod was talking about now. That's a huge difference. Your axles are even running downhill from the transaxle to the wheel.
Will - if one rotated the transverse transaxle as you suggested, what about lubrication? Do you think it would be an issue? On a manual it shouldn't be a problem, but what about the 4T60E & 65E? Also, would the diff keep enough fluid in it for sustained high performance usage?
------------------ Todd Perkins - the member formerly known as "perkidelic" todd's hot rods
[This message has been edited by toddshotrods (edited 12-29-2004).]
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08:21 PM
toddshotrods Member
Posts: 1177 From: Columbus, OH, USA Registered: Aug 2004
We have three distinct schools of thought on how to accomplish the same objective here. The only problem is there seems to be a lot of effort from each respective side to validate its point by proving "the other two" wrong. Why not just concentrate on solutions to the problems each faces and see what's in them? I know people are always going to present what they believe in most with the greatest amount of passion, but it is also true that you often find the things you need most while helping others.
I can't say that there is no possible way the Fiero can compete with world-class supercars with incremental enhancements, because I haven't seen anyone really push it that far yet. I can't say that the full tube chassis road race cars with plates could never be a production type road car because I haven't seen enough people try that either. There was a time when people said the rear-engined dragster would never work because they had never seen it done properly before. The main problem turned out to be something as simple as the steering being too quick making the car uncontrollable. There was a time when people said front-drive drag cars would never hook and run fast. This year I watched them going sevens.
The Fiero community is too small to be this divided. Those of us in this tiny little world who are actively seeking supercar performance are few and far between - battling each other is suicide.
------------------ Todd Perkins - the member formerly known as "perkidelic" todd's hot rods
That's a big reason I want to go with incremental tweaks and minor space frame mods... I can build them and sell them and put a fleet of Fiero supercars on the road.
i really like this idea, mainly because my own evil and twisted intentions could still be done, just without all the R & D. so let me know when you start working here.
This is a cradle I built. The suspension pick-up points are raised 3/4 in and the roll steer is removed. This uses 88 supsension with a few tweaks. It has mount for a small block. There is room for two turbo mufflers, and is lighter and stiffer than the stock cradle.
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09:56 PM
R Runner Member
Posts: 3696 From: Scottsville, KY Registered: Feb 2003
I thought we was having fun!. I fully respect all opinions posted here. As a matter of fact I am going Will's route with my imsa.
I'm having fun too. For me, this is the most enjoyable thread in a long time.
Perk..... I'm really not trying to argue, just supporting why I think the way I do. It appears that Will and gusshotrod are doing the same. All good clean fun. If I did step on some toes, I did not mean too.
Paul
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10:36 PM
Will Member
Posts: 14252 From: Where you least expect me Registered: Jun 2000
Originally posted by gusshotrod: WIll: I don't think you've quite got the concept down regarding polar moments. To reduce pmi, move everything closer to the GG. Running the numbers quickly, looks like about 30% reduction in pitch, about 50% reduction in roll (longitudinal vs. transverse).
I "get" MOI just fine. We may not be on the same page. I'll use this picture to demonstrate:
The CG of the engine is roughly under the carb. The CG of the transmission is probably close to being under the blue chassis bar right behind the axle. If there were a transverse gearbox attached to this engine, it's CG would probably be under the unpainted X brace. The CG of the transverse box is closer to the CG of the engine than the CG of the longitudinal box. The MOI of the whole setup is less with the transverse box (and the transverse box is lighter with less parasitic loss).
Now what you're talking about... keeping the overall length the same while increasing the wheel base and pushing the rear wheels back using a longitudinal transaxle will increase MOI of the car because you're spreading mass out. MOI is proportional to the square of the distance from CG...
The moment I'm worried about is around the vertical axis. This is the one that affects the car the most. I'd say the pitch axis is the 2nd most important (and the transverse setup has as large an advantage there as it does vertically), with roll being the least important. Roll is the only axis about which I can see the longitudinal setup having less MOI than transverse.
quote
Originally posted by toddshotrods: Will - if one rotated the transverse transaxle as you suggested, what about lubrication? Do you think it would be an issue? On a manual it shouldn't be a problem, but what about the 4T60E & 65E? Also, would the diff keep enough fluid in it for sustained high performance usage?
I don't care about the automatic transmissions... The only way you can do this is to dry sump the engine. If you do that, an active lube system for the transmission is child's play (and highly recommended, along with an oil/water heat exchanger). With enough pressure, you could run a misting nozzle into the final drive mesh... And I guess you could make a custom pan and run an external fluid reservoir for an automatic...
[This message has been edited by Will (edited 12-30-2004).]
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11:50 PM
Dec 30th, 2004
Will Member
Posts: 14252 From: Where you least expect me Registered: Jun 2000
This is a cradle I built. The suspension pick-up points are raised 3/4 in and the roll steer is removed. This uses 88 supsension with a few tweaks. It has mount for a small block. There is room for two turbo mufflers, and is lighter and stiffer than the stock cradle.
Similar idea to what I'm going to build, although I'm going to go to lengths to make mine as compatible with as many different engines, mounts, etc as possible, probably including a bolt in member to pick up the standard Chevy mount points... I agree that the factory rear roll center is too low. But wasn't that relatively easy to fix?
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12:09 AM
toddshotrods Member
Posts: 1177 From: Columbus, OH, USA Registered: Aug 2004
Thanks Will, sounds easy enough. As for the automatic thing... I always buy a manual for my dailies and prefer them. However, well built performance autos can handle a LOT of abuse, and with a TCI controller you can have full control with a cool set of F1 style paddles behind the wheel.
Glad to hear everyone's cool as a basket of cucumbers Maybe I am just paranoid because I have seen so many great threads end up in flames.
Took some pics I gotta go see if they're worth posting... be back
------------------ Todd Perkins - the member formerly known as "perkidelic" todd's hot rods
Will: By moving the engine, which is the largest mass, closer to the cg, the overall pmi is reduced; even if the trans is farther away (as it weighs much less). Also, rotating the engine as you described is a good idea. Have you thought about how much of the block would have to be removed to miss the axle? The roll center on the rear clip I made is still too low and can't be raised any further as the linkage would hit the trans. Maybe a better solution would be custom hub carriers to lower the outboard pick up point? Then you still have the problem of less than ideal camber gain and axles running at angles. If you rotated the engine/trans as you described, there might be room to raise the roll center and use longer linkage (if you can rotate it enough). Were you thinking of ditching the struts? What type of rear suspension were you thinking of?
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02:03 AM
toddshotrods Member
Posts: 1177 From: Columbus, OH, USA Registered: Aug 2004
My favorite part of the Fiero, and the humble beginnings of my project:
So far, my time has been spent mostly in research. Even the "demolition work" shown here was done mainly to support the design process, with an eye towards finally beginning to build it in 2005.
The rigidity will come from a full front to rear cage. It will tie into the ends of the clipped factory main frame rails. In back the cage will actually extend through the frame and have the rear cradle mount incorporated in it. Inside the car I want to tie the front cradle mounts into the cage with down tubes that end directly over them. Gonna have the cage done at a chassis shop, and I want the car on the frame table while it's being done.
------------------ Todd Perkins - the member formerly known as "perkidelic" todd's hot rods
[This message has been edited by toddshotrods (edited 12-30-2004).]
Just so we are all on the same page......... (literally ) Here is a section or two from one of my better books. All credit should be given to the author Fred Puhn. We can use this as a discussion reference...
BTW.... Did we really ever answer the original thread question?
has anyone actually measure the front suspension components and figured out just how much they have to change the position and length of arms to correct geometry?
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10:29 AM
toddshotrods Member
Posts: 1177 From: Columbus, OH, USA Registered: Aug 2004
am I the only person to think about replacing the fieros front suspension with struts?
I thought about it before, but haven't given it serious consideration (which to me means seeing what kind of geometry an optimum setup could have). BMW uses struts to good effect on the 3-series - I believe they're on all four corners. Not sure what the rest of the suspension is though. My Accord (91) has struts at all four corners, but I also have upper and lower control arms in front and a typical multi-link in back. It's much more sophisticated than the Fiero rear setup. The strut actually functions more like a coil-over.
Crow - you're building a roadster right?
Everyone Why don't we all follow Paul's lead and put the stock Fiero's numbers on paper or in some software and start tweaking. I am sure people have done it before but let's all hop on the page as he just opened and do it openly this time, right here where everyone can see the results and offer suggestions. First thing is we need clearly defined objectives. Here are my suggestions:
One Best incremental enhancements to the most common 84-87 front suspension. First-gen Camaro guys have this. It evolved from racing and is a simple mod that moves the UCA pivot point for good geometry. It's about time this becomes available for the Fiero. There are companies that sell templates and instructions for performing "the Guldstrand mod" on first-gens. We can go them one better by developing free downloadable drawings and plans. Same crossmember, same arms, just revised geometry. The maybe special tubular control arms for the next step. The point is, all the currently available bolt-ons should work with option "one". Goal = performance on par with or exceeding the 88 setup.
Two A complete "from scratch" front design that will bolt to the front of any Fiero with nothing more than minor modifications. Of course some things like knuckles would likely be pre-existing parts from some other vehicle. Tires will fit under the fenders. Goals = great geometry, great driving experience, great numbers. More expensive but more rewarding for the true performance junkie that doesn't want to alter the look of the car.
Three The ultimate front suspension that can be adapted to the space frame. May require extensive mods and possible a wide body to cover the tires. No compromises in the design except maybe what can fit on or around the stock main frame rails, transaxle, engine, etc. Other less critical items may need to be moved. Goal = supercar performance, no excuses.
Four The ultimate front suspension that can be fit under the stock bodywork (width). Would most likely require a tube chassis or at least getting rid of the factory main rails.
Five Incremental mods to 84-87 rear strut suspension. Altered pick-up points, etc. Complement to "One".
Six New cradle with strut suspension as gusshotrod has done, and Will has planned, which will address geometry and provide best solution without radically transforming car. Complement to "Two".
Seven SLA suspension designed to work with stock main frame rails (strut towers removed of course) and transverse powetrain, on custom cradle. Goal = best possible geometry for this layout.
Eight SLA suspension designed for Porsche transaxle cars with complete custom rear frames. Goal = best geometry possible no excuses.
The last two actually could be the last four because it depends on whether or not the stock body (width) is being maintained.
Any takers
------------------ Todd Perkins - the member formerly known as "perkidelic" todd's hot rods
I am working on some other stuff, so you guys will need to give me some time. If I can get it working, I have a front suspension geometry program that I can plug the numbers into. The problem with the program is that (other than I can't get it to run on my new computer) it needs X,Y, and Z coordinates for each pivot point. A lot of data. I have it for the race car but have never plugged it in. It would be very interesting to compare the wheel position vs. input between the IMSA design and the stock design. I know apples and oranges, but we could (I know I could) learn a lot.
Please forgive me if I can't get it working or run out of time.
I agree with the bolt it in idea for the front suspension. I have often wanted to design my own for the street using some of the concepts from the IMSA.
On another note...... (and I have said this before).......... What about a 4.3 (400 hp easily) on a porsche G50 with a flat water pully? No cutting for the front fire wall. I know it will work and have the sources to put one together, but again, never enough time. Eventually I will build this setup with the custom suspension (my design) and make it a daily driver. In a way it will be my supercar. With that engine combo, it would still be "light" and well balanced giving it some good potential for a we designed suspension....
Sorry Perk..... didn't read the last few posts........ gota' run
Paul
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04:56 PM
Will Member
Posts: 14252 From: Where you least expect me Registered: Jun 2000
Will: By moving the engine, which is the largest mass, closer to the cg, the overall pmi is reduced; even if the trans is farther away (as it weighs much less). Also, rotating the engine as you described is a good idea. Have you thought about how much of the block would have to be removed to miss the axle?
But the CG moves around as you reorganize mass within the car... it's a catch-22. My opinion is that pushing the driver forward and the transmission and rear suspension (wheels, brakes, etc) rearward, you're spreading mass out and increasing MOI.
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The roll center on the rear clip I made is still too low and can't be raised any further as the linkage would hit the trans. Maybe a better solution would be custom hub carriers to lower the outboard pick up point?
Now you're thinking...
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Then you still have the problem of less than ideal camber gain and axles running at angles. If you rotated the engine/trans as you described, there might be room to raise the roll center and use longer linkage (if you can rotate it enough). Were you thinking of ditching the struts? What type of rear suspension were you thinking of?
Actually, lowering the outer pickup point and raising the inner not only raises and stabilizes the roll center, it improves camber performance. Think about where the hub carrier will be on the control arm arc... The trade off is more tire scrub... CV angles are the result of raising or lowering relative to stock, NOT where the suspension pickups are. If the car's within an inch or two of stock height, it's probably fine. I think there's plenty of potential in the strut configuration. After all, BMW and Porsche use it to great effect. Colin Chapman wouldn't have built Grand Prix cars that way if he couldn't get it to work outstandingly well.
I did however, once come up with an SLA configuration based on the '88 rear suspension that kept the roll center within an area the size of my hand through 5 degrees of body roll and 3" of suspension travel each direction.... I might have to revisit those measurements to make sure that I have them all correct. I've also started writing my own suspension analysis software...
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09:53 PM
ryan.hess Member
Posts: 20784 From: Orlando, FL Registered: Dec 2002
Originally posted by Kohburn: I'd like to focus on the front suspension since I feel the rear isn't a major problem area that a few minor changes can't fix the front however has major camber issues
For supercar minimal body roll, I don't think that's NEARLY as much of an issue as the other two major faults of the front suspension... excessive scrub radius (resulting in poor steering feel and excessive kickback) and pro-dive (resulting in excessive dive under hard braking).
The former can be fixed with the correct (and enormous) wheel offset. The latter can be fixed with wedges between the chassis and cross member, effectively rotating the whole suspension down around the rear LCA pivots. This increases front ride height, but it shouldn't be necessary to use more than an inch or so thick wedge at the axle CL... When used with 2" lowering knuckles, the result should be 1" of lowering overall and significantly less brake dive.