355 Ferrari F355 Challenge Steering rack

Manual racks often give less road feel than hydraulic, especially on a car designed to have power assist. They are much, much heavier. You steer from the shoulders not the hands.

 

This video discusses disabeling your power steering with a "loop" feature. Probably the best way to go. Not worth converting to 348 (if you even could) for .25 turns quicker.

Keep in mind a 348 also has a smaller diameter steering wheel which helps.


An old poster once posted his power pump wasn't working (on a 355) and the car effectively functioned as manual. Said it was a pain in the ass for low speed driving, but once speed picked up, steering felt light. I'll try to find the post.


Do we have an answer yet on the lock to lock on a Fiorano rack?

 

Who’s going to give it a try ?

 

@spaghetti_jet





https://www.ferrarichat.com/forum/threads/reducing-steering-assist-355.338443/page-2#post-140841426

"When I first got my 355 back in 2003 it came "fully serviced" prior to delivery. The job they did was shoddy and among other minor issues there was a pipe clip chafing on the PAS drive belt. A few months in the belt shredded about 150KM from home. Once I'd established that the belt was the only issue I decided to drive home without power steering. The steering was surprisingly light when moving. Not too much difference I'd say compared to normal, although I didn't do any heavy cornering so can't speak for steering loading up when heavily cornering. Obviously I was taking it easy. The biggest issue was at parking speeds which required brute force on the steering wheel to park.

My experience is that there is not a lot of power assistance when actually moving so if you really wanted to change the feel of the steering I would say to install the challenge or fiorano parts since mechanically/gearing-wise the feel is still quite light when on the move."

 

Huh? Less road feel? I'd be surprised if the 355 has more road feel than a 348. Never driven a 355 so I can't compare myself.

 

I have always wondered if the steering feel on these cars degraded with age. I remember Clarkson loved the steering feel on the 355.
Do you think the bushings and other suspension/steering components may have aged to where steering feel would be impacted? I know the tires on my car are probably 14 years old and need to be replaced. I'm sure that has something to do with it.

 

Interesting, I will say once your roiling the 348 steering is very light, definitely hands light not shoulder. Perhaps when stopped and turning the wheel without rolling sure. Roll a tad and is lightens up. Around the neighborhood streets I can steer with 1 hand no problem at highway speeds its almost too light, it can over respond to quick inputs. I always thought manual racks offered more feel than assisted racks. Not to confuse the issue I like assisted racks myself, certainly not criticizing the 355's steering

 

I recently measured the stock front and rear springs with 30k mi and at free length they measured 165 lbs/in for the fronts and 245 lbs/inch in the rear. Stock specs are designed to be 185/260. I need to double check them again at another place just to make sure it isn’t the tester that is off.

Old/worn bushings will degrade feel as well.


However, considering the Fiorano Handling package made upgrades to steering, beefier roll bars, and stiffer springs… there was alot of room for improvement.

 

I find the steering feel of the 355 to be among the weak points of an otherwise sensational driving experience. But I highly doubt it has anything to do with power vs manual rack. My 993 has power steering and the feel is amazing -- improved by solid inner tie rods, poly rack bushes, and PSS10 Bilsteins. I would bet that swapping out the rubber steering rack buffers on the 355 for poly would make a noticeable difference. It sure did on my 993.

I highly doubt the answer is manual steering. If you have a chance to drive a 964 RS America, which has a manual rack, it definitely doesn't have better road feel.

I suspect there is also some interplay between road feel and suspension firmness. My stock 37K-mile 355 has (to me) a fairly floaty suspension for such a high performance car. I'm sure the shocks could use a rebuild and bushings could be freshened up. I never drove one new so have no idea what I'm comparing my car to, but the steering is definitely a little vague. A tighter front suspension would probably improve it.

 

Steering feel from Ferraris such as the CS, Scud, Speciale etc… should be proof power steering isn’t the issue. Perhaps a smaller percentage of the issue. Other aspects of the car need to spec’d correctly first.

https://www.pistonheads.com/gassing/topic.asp?h=0&f=235&t=1376648

“I had 98 355GTS with FH pack, totally transforms the car. 2nd only to my 991GT3 in the handling stakes”

 

Manual steering on my 355 Ch. IMO, steering feel is significantly improved compared to street 355 ps, which I perceive as relatively numb for a hydraulic assist. Also, driving inputs (shifting, manual steering, clutch, braking) are better matched amongst each other…this improves driving experience for me.

For comparison, I rank manual steering on my Ch to be on par or better with manual steering ac 911 and GT3 Cup steering…all three I’ve driven back to back. Better than any other street 911 hydraulic steering. Just to state perhaps the obvious, tires also make a difference in feel; so there are other variables to consider.

 

How is it on low speed?

It should be noted a 355 challenge has solid bushings, stiffer springs/dampers, stiffer engine mounts, stiffer roll bars, cage, etc.. I can imagine there's almost no deflection.

 

Steering on my 355 is light on the street, weights up nicely when pushed with good feel. I think less assist coupled with less caster would balance that out - and give a less drastic change when lightly loaded vs. at the limit. The FH pack makes it quicker ratio and apparently changes the boost level, hence a little more weight across the range, but it's not doing anything magical you couldn't do with some tuning on the stock rack unless it's the faster steering you're after. I will say the steering feel on my 355 feels about perfect, I wouldn't change it and the only change from stock is the springs (H&R).

 

For best context, I can answer relative to other manual steering cars. Specifically, 355 Ch manual steering effort on Trofeo Rs is very comparable to street 911 3.2 (on Yokohama A052s sticky summer tires) which was my daily driver this summer. So no issues with hopping in 355 Ch for backroad or track drives. Parking lot maneuvers were about the same for both cars. Best to turn steering wheel when rolling - par for the course to those familiar with driving manual steering cars. Still, both cars’ steering effort at low speed felt lighter than manual steering 944 Rothmans race car (with engine weight over the steering rack and front tires) and 50s Alfa Giulietta.

Having said this, I’ve been driving light ps steering Cayenne this week and intend to do so through fall/winter. Hopefully, my arm muscles do not atrophy. Lol. Seriously, I’ve owned manual steering cars (355Ch for >8 years and with manual steering the last 3 years) long term. All good. Exemplary feel benefit significantly outweighs higher steering effort at low speed IMO.

 

LHD manual rack for 355 is PN# 157544. 348 PN# is 155566. They both appear to be TRW racks.

https://www.ferrarichat.com/forum/threads/348-steering-rack-install.587795/

https://www.scuderiacarparts.com/part/6882/ferrari/157544/mechanical-steering-box.html

Based on drawings, they appear to be an identical unit on the outside, so there is a high chance a 348 manual rack can work on a 355. It could very well be the 355 manual rack might have faster (or slower) than 3.0 turns lock to lock (348 spec) hence different part numbers. Another 355 unsolved mystery .

 

I don't see Ferrari choosing slower than 3.0 turns and since we know it isn't the same as a 348 rack, then chances are it is quicker than 3.0. Could be somewhere between 2.25 -2.75 turns.

 

@Senshi458

Can you confirm the lock to lock steering turns on your 355 FHP car? It should be somewhere between 2.25 -2.75 turns. If you can comment on handling, even better .

 

Let’s see what the Fiorano Handling Pack is all about.



Image Unavailable, Please Login

 

Do you mean only one measurement? If so, how far were they compressed?

 

They said near coil bind.

 

If that's really the only measurement they took, their results should roughly correspond to the dynamic load specs in the WSM. They come to about 180 lb/in for the front spring and 255 lb/in for the rear, +/- 3%.

 

Figured I’d post this regarding the 355’s active damping system.

https://www.ferrarichat.com/forum/threads/355-suspension-differences.446857/page-5

“The F355 active damping system is misunderstood for sure; I field questions about its operation all the time...

The system works well, it's the first active damping system put into road car volume production by Ferrari (with technical partner Bilstein), subsequently every road car since has some version of active damping as the technology has evolved.

Q: I can't feel a difference between the two modes

A: Under certain driving conditions this is not surprising. If one were to switch modes whilst driving on fairly smooth pavement, especially something like Interstate/ Motorway driving where cornering is almost a non-event it would be very difficult to discern differences.

Why? Because the shocks are not moving all that much under these conditions, perhaps less than 1 inch/ sec, and without lateral acceleration the computer is told to adjust very little.

The previously posted graph from the WSM only tells part of the programing: adjustment related to road speed only. The active damping systemalso monitors lateral and vertical acceleration plus throttle position. So under high cornering forces and bumpy conditions the program is also adjusting accordingly. The WSM graph should look more like the ECU topographical map of fuel injector open time, with the above variables ondifferent axes.

The true test is to find choppy pavement, thenthe chassis experiences short but high velocityinputs so you'll feel the difference. Anothermethod is driving on track.

Also, keep in mind that the system never quitegoes to the extreme settings of 0° or 90°.

The adjuster moves a wedge shaped valve that controls oil flow past the main piston valving and meters oil past specific discs just to control the bypass (aka "bleed") oil flow.

Attached image is actually from a Mondial T, I don't have a good quality image on thiscomputer for F355. The Mondial T adjuster isGeneration One of this system, the adjuster wedge is shaped differently and the shock rod doesn't have additional flow control discs forbleed, just an open port as seen in the photo. Mondial T also adjusts over about 270° vs about 90° for F355. The change was made to improve response time.

This system is misunderstood so much thatvirtually every F355 Challenge we've worked with has the system removed from the car....

Best,
Rob”


“The computer only monitors electronic sensors and actuators: accelerometer, solenoid motors, and any continuity issues...”

 

From my personal experience, shock damping settings do affect steering feel/response.

I had a Lotus Exige, which I daily drove for a year or two and ultimately racked in about 100k mi over a decade. My commutes were 45 min hwy driving (no traffic) each way on days I worked. The Exige has manual steering.

I focused primarily on weight reduction and handling when I built that car. No expense spared. I had a 3-way JRZ setup then went with a 2-way Ohlins TTX setup. The Ohlins TTX allowed me to conveniently adjust rebound and bump settings on the fly. I made 1 adjustment (rebound or bump), drove for 2-3 days, and took notes. I did this until I went through every rebound/bump setting combination possible because I wanted the perfect setting for the road (track a different setting).

I found that when I softened up bump settings for front dampers beyond a certain point, steering feel became increasingly loose/vague. Not bad, but noticeable. Remember… an Exige has manual steering.

I bring this up because the 355 has active damping. The 355 might feel soft and vague when just cruising about, but the Bilstein ECU could very possibly be stiffening damper settings for better steering once it senses the car turning up. I am hoping the FHP Ecu has even better/more fine tuned settings over standard, since it was introduced later in 98/99 after Ferrari spent more time with the 355. Stiffer front springs/roll bar should help as well. We’ll find out soon enough.


I never found the “perfect” road setting for the Exige. Every setting was a compromise. Might be good for one road condition, but not another. If only it had active damping .

 

Here’s the Exige I built. I guess the new owner had some Youtuber (from Norcal?) review it. He does make some nice comparisons to the Porsche Cayman’s electric steering.

I don’t know if the new owner lied or the Youtuber misunderstood, but I did the basic bolt-on power mods to the car, not the new owner. Intake, headers, decat, and muffler. Probably the first thing I did . And the car isn’t 2000 lbs. It’s 1500 lbs.

 

Is the FHP ECU you showed plug and play for any 355 ?