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Discussion Starter · #1 ·
Ok all i took the car out for a little road test. It's scaled/weighed and adjusted/aligned for drag/rally car. The front sway bar is on and I’m using LSmans race genesis shocks. Everything is adjusted. 40% weight in front 60% in rear. The car isn't tuned properly yet (decent starting tune). A/F is high 9's low 10's. I did a couple rolling pulls around 50-60% throttle. the first thing i noticed is the steering is not stiff enough. Is there a way to stiffen it up. The last thing i want is to over correct when the rear breaks loose. And yes it broke loose.

At about 80 the rear breaks loose with maybe 60% throttle. The turbos spool and it feels like a 200 shot of nitrous (because a/f is much better). I'm not stressing the rear breaking loose because that's to be expected. I am worried about the steering though. Correcting for the rear breaking loose is very sensitive. This is only at 10 LBs and around 80MPHs and maybe 600HP. The steering is horribly sensitive at 80 what happens when I’m going 160?

Any thoughts on stiffening it up would be great! What do the race teams do?
 

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Discussion Starter · #3 ·
What is your alignment set at camber,caster and tow? Have you check for bump steer?
Are you using the ff manual rack?
I'll have to pull the alignment sheet when i get home. But yes using the FF manual steering rack. The car is solid up to when i have to correct for it breaking loose. The streeing is very sensitive even at low speeds. I was hoping the sway bar would have stiffened it up more than it did when i put it on. Is this normal? Very sensitive steering or do you think the alignment is causing it?
 

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The alignment is where you work from, caster angles are typically high on these from 4 to 7 degrees. At those settings you can actually feel the car is self correcting.

A steering damper is typically used on drag link type steering, because it's literally a shock absorber with 50/50 valving and high dampening. Those type of steering setups also use the typical recirculating ball steering boxes which naturally impede steering feedback forces. A rack and pinion doesn't, input on the rack spins the steering shaft. Extreme cases, like smacking a street curb, were known in the early days to actually injure people's hands. They didn't know to keep their thumbs out.

You can tune some of it out, but responsive steering is the point of rack and pinion. Dead slow with no feedback doesn't make for much of a steering box on a track.

Another factor is tire sizes and weight distribution. With 60% in the rear, it's like a Porsche, it naturally has oversteer, not understeer. The back end comes around quick once momentum is put into play. I learned to drive in a VW bus, same thing, doesn't handle at all like a '66 Mustang. You learn to drive it respecting the weight bias - or you travel backwards on snowy roads a lot. :)

Separate all the influences into each respective input, make adjustments, and then you learn what's different from the daily driver. Assembling a car is the easy 5%, now you get to sort out the alignment, sway bar bias, spring rates, etc. Every change to improve straight line traction on the strip will tend to be a negative aspect on the road, it's the nature of dialing in a car exclusively biased to a particular use.
 

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Linxs
You have a gen 1 chassis. Unless you have modified the front upper a arm mounts to move them rearward, the best caster you could see is about 1.5 degrees. The Gen 2 chassis had the front upper a arm mounts moved rearward about 1/2 inch and they get more caster.
 

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Yep, but put more caster into it and it becomes tougher to turn. We recently increased the caster to just over 3 degrees, still a relatively mild caster number, and drivers that had never driven a GTM before commented on how heavy the steering was...so, once again, a reason for the power steering mod. :)
 

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Discussion Starter · #8 ·
Yep, but put more caster into it and it becomes tougher to turn. We recently increased the caster to just over 3 degrees, still a relatively mild caster number, and drivers that had never driven a GTM before commented on how heavy the steering was...so, once again, a reason for the power steering mod. :)
what rack do you suggest? You mention the MR2 power steering pump is recomended.
 

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The Mustang power steering rack that is a driect replacement to the FFR supplied rack. IMHO it should be modified by AGR with a 265 torsion bar. Their # is 817-626-9006. The rack number is 712591.
 

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Linxs,
I think I know what you mean. When I first started driving mine and the tires broke loose it seemed like the car wanted to drift around. I finally figured out most of that was me. I've never driven a car that required so little imput from the steering wheel to change direction. Moving the wheel 5 degs moves the car quite a bit. This is amplified at higher speeds. I now have the AGR power rack with the 265 torsion bar, MR2 pump, Crash (Eeney) pump control, Genesis shocks and swaybar. The new rack is quicker than the manual rack, The steering is a little heavier, you get a little less feedback to the wheel when you hit imperfections in the road. The quick rack is great on the twisties but at high speed in a staight line you need to be very gentle with the input to the wheel. If I was building a Texas Mile car I would want a much slower rack.
Keith
 

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I do believe there is a slower rack available from AGR. Also, there is an issue with alignment in that the FFR PDG GTM can become very "twitchy" even with the slow rack at high speeds under heavy, WOT, accelleration. As you say, you just have to be VERY careful of the amounts of inputs you are putting in.

Where the PS really shines is in slower corners, in dampening bumps and such at, really, all speeds, and in allowing more caster and a quicker box so as to make it easier to recover from a loose rear end situation.
 

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Discussion Starter · #12 ·
Linxs,
I think I know what you mean. When I first started driving mine and the tires broke loose it seemed like the car wanted to drift around. I finally figured out most of that was me. I've never driven a car that required so little imput from the steering wheel to change direction. Moving the wheel 5 degs moves the car quite a bit. This is amplified at higher speeds. I now have the AGR power rack with the 265 torsion bar, MR2 pump, Crash (Eeney) pump control, Genesis shocks and swaybar. The new rack is quicker than the manual rack, The steering is a little heavier, you get a little less feedback to the wheel when you hit imperfections in the road. The quick rack is great on the twisties but at high speed in a staight line you need to be very gentle with the input to the wheel. If I was building a Texas Mile car I would want a much slower rack.
Keith
Interesting. Do you mind if i ask roughly how much the setup was? I'm not sure about putting on a PS pump i have no room upfront. I have a waterbox for the intercoolers in that area. I guess i can see what AGR has to offer. Thank all!
 

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Interesting. Do you mind if i ask roughly how much the setup was? I'm not sure about putting on a PS pump i have no room upfront. I have a waterbox for the intercoolers in that area. I guess i can see what AGR has to offer. Thank all!
I used the corvette variable press rack and pump and it works very good. But I research other options as well. I had order a rack from agr was told two weeks delivery and after two weeks he told me maybe in four more weeks,after i cancel the order I had to go through the credit card company to get a refund,after that I decided to go with the corvette system.
One of the systems I looked into was the mustang quick ratio rack and a gm corvette engine driven p/s variable press pump,it is made for track use with the mustang power rack. Flaming river makes them and you can fine tune it with a bypass valve if needed but I have been told that is not needed. Check the roadster forum they use the same rack with engine driven pump. Summit has the agr and other quick ratio racks and the same with the variable press pump, the pump and rack run about $500.00 dollars. I ran steel lines from the pump to the rack and adapted the corvette hoses for about $80.00 dollars.
 

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I am pretty sure AGR had some issues when they first started selling through Summit. Something about large volume of orders and not having enough stock on hand or something like that. Anyway, you can certainly use other sources for the rack. It is simply a Mustang Cobra power steering rack with a 265 torsion bar. I am told that you can use the regular factory supplied torsion bar, that is a bit heavier, but that then you must turn the pump down to the pooint where there is a bit of an issue with surge because the pump isn't turning enough RPMs. The smaller torsion is the fix for this.

All told with braided lines and adapters, you are looking at about $1000. The pumps have gone up in price lately and are getting to be more than half the cost of the entire package...used! The Toyota pumps are good pumps though. If anyone has the experience and/or desire to build their own pump controller that would interface with the PWM output of the controller that www.myraceshop.com sells, then the pump could really be any 12 volt hydraulic pump that puts out 600-800 PSI. I do have instructions on how to build these controllers, but that is the beauty of the Toyota pump, as the FET high power controller is built into the pump.
 

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Discussion Starter · #15 ·
wow great information guys thanks. I'm going to work on getting more caster and i guess i'll go ahead and get the rims and tires i was holding off on to see if anything improves. replacing the rears 305 with 345 MT drag radials should fix the break loose (lol for now) and replacing the front 245 with 275 sized tires will help out front. I'll put it on the rack again and see if i can get more than 2.9 caster which is where it is today. If i still don't like it i will prob. go Mikes route. Thanks again!
 

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I have had the same issue with my car and all I can say is, if you think you are gonna "free hand" the steering wheel above 80... be ready to see the ditch !

Keep your left elbow ON THE DOOR as a brace and your left palm firmly planted into the steering wheel and you will be surprised how much better you can keep the car straight.

I am running the 345's and mine doesnt break loose as bad as your describing.. unless you allow a tire to cross the double yellow line under accelleration ... dont do that by the way.

I started a thread on here about how to achieve more caster from the Gen 1 car .... yes I know.. along with Crash's shim kit !! lol ... you will have to weld in and redrill the holes for the upper mounting tabs... Its really not as hard as Im descirbing though for any average car builder. I have mine as far as I can get it with out rewelding the whole mounting section of the upper a-arms and my car STILL DOES NOT RETURN TO CENTER when I let off the steering wheel !! and Im gonna bet yours wont either... and until it does... its gonna be REAL sensitive !
 

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Discussion Starter · #17 ·
I have had the same issue with my car and all I can say is, if you think you are gonna "free hand" the steering wheel above 80... be ready to see the ditch !

Keep your left elbow ON THE DOOR as a brace and your left palm firmly planted into the steering wheel and you will be surprised how much better you can keep the car straight.

I am running the 345's and mine doesnt break loose as bad as your describing.. unless you allow a tire to cross the double yellow line under accelleration ... dont do that by the way.

I started a thread on here about how to achieve more caster from the Gen 1 car .... yes I know.. along with Crash's shim kit !! lol ... you will have to weld in and redrill the holes for the upper mounting tabs... Its really not as hard as Im descirbing though for any average car builder. I have mine as far as I can get it with out rewelding the whole mounting section of the upper a-arms and my car STILL DOES NOT RETURN TO CENTER when I let off the steering wheel !! and Im gonna bet yours wont either... and until it does... its gonna be REAL sensitive !
What did you name the thread so i can look it up?
 

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A lot of the not returning to center thing may have to do with the surface you are driving on. I know it does with the race car. So much so that I frequently think the steering wheel is not on centered(we have a quick release), but once I get the car on a relatively flat section of track, it, indeed, is on correctly.
 

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I think we are talking about two differing goals here. Are you setting the car up to be a daily driver that you can cruise down the freeway and drink your coffee with one hand and steer with the other? If so then yes, I can see the need for a bunch of caster so that the wheel will self center.

For a track vehicle I have never run much caster. I guess maybe it's because I've raced open wheel formula cars (hardly anyone runs more than 2 or 3 degrees of caster) but to my way of thinking I WANT the car the be responsive....heavy, dead feeling steering is NOT what I desire. On a race track I steer into AND out of the corner AND I even steer it down the straits......who cares if the wheel self centers. A rear engine car with a lightly loaded front end IS going to feel different than a heavy front engined street car......and it should.....
 
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