[GTO]

Originally Posted by subache

Useful info GTO, thanks! Please tell me how much it may cost approximately?

Old Sierra, so my brother had bought it used for about 2.5K. My Jeep is running the exact same air-con (transferred from the Sierra)

[subache]

Originally Posted by ananthkamath

small world, Chethan!! welcome to the forum.

Thanks Ananth! Was wondering till now if you had become too busy these days!!

Originally Posted by ananthkamath

......why not buy a cheap jeep and prep that for serious off-road work? i am sure kiran would suggest the same to you. Probably can be put together for less than 50k. You already know there is nothing on earth to match a well setup jeep off-road, certainly not a 2WD Sierra.

Very right Ananth! Its only for the love of doing it I am exploring these mods' feasibility on my car

Originally Posted by ananthkamath

At 150k kms and a whining noise, I'm guessing the turbo is probably on its way out.

Consulted Kiran already, yes its the Turbo mostly. Two options suggested by him: buy a new Turbo - about 35-40k or refurbish with a warranty (will PM the details to you before doing anything) at a known place in Banglore - about 12.5-15k, working out the budget for the cheaper option (can manage to run with this for another 5k kms as told by Kiran).

Originally Posted by GTO

Old Sierra, so my brother had bought it used for about 2.5K. My Jeep is running the exact same air-con (transferred from the Sierra)

I guess you have got it at a nice bargain GTO! it is costing around 8k for the setup locally in Mysore.

[veyron1]

Originally Posted by subache

I had thought of even making new coil springs at the front with lesser coils (hence stiffening up) for the same spring length

Sorry, subache..it's the other way around, actually. Same height, lesser coils would mean softer setup (coil rod radius being the same). More coils, stiffer the setup. An easier way to stiffen the suspension is to get better dampers (Safari's OEMs are gas-charged, those should do the trick. Mounts have to be slightly altered for bushings & fasteners, though).

Originally Posted by subache

Also I observe, the front of the car gets too pitched-in in case of heavy braking. And the rear gets easily locked up due to this and the car drifts sidewards.

A fouled LSPV (load sensing-proportioning valve). Replacement will solve the problem. Basically, an LSPV is a spring loaded bypass valve that decreases the hydraulic pressure to the rear tandem cylinders when the body height increases (no-load), or increases it when it lowers(full/part-load). You should find it at the rear right hand side of the chassis, besides the coil spring...

The 207 DI (& the TL 4x4) shares front body parts & few interior parts with the Sierra, like the headlamps, fenders, windshields, dash & the like; that's about it. The front suspension is way different. The 207 DI/TL runs 16 inch rims, IIRC, with different sway bar rod dia. (front), linkages and mounts.

If the car has done 150,000 kays, the turbo's shot for sure. Do you see oil at the turbo housing/intercooler plumbing? Black smoke spewing out the back at WOT? Time to change the turbo & service the fuel pump..

Frankly speeaking, I'd advise you to bring the car back to mint condition first (mechanically & aesthetically). That alone would set you back around a lakh, if you go the whole hog; that is, engine o/h, A/c, new tyres, maybe a coat of paint, etc.

Then, you could get a Gypsy king (as a second car) for all your wadi-bashing.

P.S- The Sierra turbo 4x4 is a sweet machine, but very rare. It's no different from the normal one aesthetically, except the 4WD knob between the gear lever and the parking brake. If your local dealer is any good, he should be able to find one for you.. There were a few mint ones in Gujarat for sale a few months ago (2003 make, 0 km, export models- last of their ilk)...sadly, at a very steep price of 6 lacs...

[ananthkamath]

Originally Posted by veyron1

Sorry, subache..it's the other way around, actually. Same height, lesser coils would mean softer setup (coil rod radius being the same). More coils, stiffer the setup. An easier way to stiffen the suspension is to get better dampers (Safari's OEMs are gas-charged, those should do the trick. Mounts have to be slightly altered for bushings & fasteners, though).

actually lesser coils = stiffer.

Originally Posted by subache

Also I observe, the front of the car gets too pitched-in in case of heavy braking. And the rear gets easily locked up due to this and the car drifts sidewards. Is this because of the weight distribution prob between front and rear? Have heard that in case of tempo trax, safari and scorpio vehicles, the rear brakes loosen up not to lock the wheels in case of heavy braking due to some kind of safety arrangement. Is this true?

i'd suggest not touching the spring rates. It might just be a problem with the LSPV as suggested by veyron. The safety arrangement you speak of is a brake proportioning valve. Its function is to reduce hydraulic pressure to the rear slave cylinders under moderate to heavy braking, to prevent rear lockup.

At 150k km your original shocks are likely to be quite tired. A set of OEM shocks would be a good investment to start with, unless you can find stiffer ones for a sensible price. I'm pretty sure your car feels way underdamped right now (boat-like body motion) and new shocks would cure most of the above issues. .

[Mpower]

Has this been happening from day1.

I think your LSPV is fine, its just your front shocks are totally shot, so the nose dives and your rear is unloading causing it to lock up.

Since its a separate shock and spring, some basic research should help you find a different OEM or aftermarket shock that should work.

[veyron1]

Originally Posted by ananthkamath

actually lesser coils = stiffer.

Sorry, ananth. I should've been more specific. What I meant was this; If, for example, a 30cm tall spring with 10 coils/windings is taken, and one coil is reduced, you'd have a stiffer 27cm tall spring. But if you reduce that one coil and retain the height at 30 cms, you have a softer spring; rod radius constant in both cases.

Since subache wants to stiffen the suspension AND increase his ride height, reducing the coils wouldn't solve the problem (if the spring height is kept the same and the number of coils reduced, he'd end up with a softer setup-which was what I was getting at).

@Mpower; if the front nosedives and the rear does come up, the LSPV is supposed to reduce the fluid pressure to prevent the lock-up, ain't it...

[subache]

Originally Posted by veyron1

Sorry, ananth. I should've been more specific. What I meant was this; If, for example, a 30cm tall spring with 10 coils/windings is taken, and one coil is reduced, you'd have a stiffer 27cm tall spring. But if you reduce that one coil and retain the height at 30 cms, you have a softer spring; rod radius constant in both cases.

Since subache wants to stiffen the suspension AND increase his ride height, reducing the coils wouldn't solve the problem (if the spring height is kept the same and the number of coils reduced, he'd end up with a softer setup-which was what I was getting at).

I am again sorry veyron1, Ananth and me are still right I guess because, if we reduce one coil in 30 cm tall spring and still maintain height at 30 cm, the spring becomes stiffer. Here it is how:

Case1:
Spring height: 30 cm; No. of coils: 10; Wire dia =d;
Now to create 'Y' deflection, each section of coils have to deflect by some amount which is amounting to 'X' kg of load let's say.

Case2:
Spring height: 30cm; No. of coils: 9; Wire dia =d;
Now to create the same 'Y' deflection, each sections of coils have to deflect so much more which means we need to apply larger load than 'X' kgs. which again means the spring got stiffer as one coil got reduced for the same height.

[Calculator for Designing Compression Springs, just change the no. of coils in the calulator and observe that maximum load possible changes in each case]

[Rigid Rotor]

A fouled LSPV (load sensing-proportioning valve). Replacement will solve the problem. Basically, an LSPV is a spring loaded bypass valve that decreases the hydraulic pressure to the rear tandem cylinders when the body height increases (no-load), or increases it when it lowers(full/part-load). You should find it at the rear right hand side of the chassis, besides the coil spring...

Excuse me gentlemen - ahem - hate to interrupt this rather intense discussion - but as I understand it - the Sierra's LSPV is in the hydraulic (brake line) circuit and as the Sierra manual describes it - it works on the principle of a ball mounted in a cylinder that's tilted up from the horizontal - the 'upslope' end of the cylinder is pointed towards the nose-end of the vehicle. Under hard braking, the ball rolls upslope and reduces the fluid pressure to the rear circuit - thus proportioning the fluid more towards the front brakes.

So I don't think the LSPV has either a load or a ride height sensor.

Any opinions on this one then??

[subache]

Originally Posted by Rigid Rotor

..... and as the Sierra manual describes it .....

Hello Rigid Rotor, Do you have a Sierra manual with you? Is it Turbo's or NA model?

Thanks for sharing this info about LSPV, I am sure the T-Bhp Gurus would respond for this!

[veyron1]

Originally Posted by subache

I am again sorry veyron1, Ananth and me are still right I guess because...

My sincere apologies. Suspension 1-0-1. Somehow, I seemed to keep thinking that lesser coils equate to a softer setup under similar load and height conditions, as has been my previous experience (albeit with real-world experimentations). Thanks for that link. Reminded me of a lot of other stuff as well...

@Rigid Rotor: If you check the Sierra's undercarriage, you'd find the LSPV at the aforementioned location. Again, the LSPV is "in" the hydraulic lines, and a purely mechanical spring-loaded bypass valve, like I said. No sensors. One end of the actuator spring is attached to the chassis, and the other, to the suspension. Under braking or under load, the spring changes the LSPV load, thus increasing/decreasing pressure.

[ananthkamath]

Originally Posted by Rigid Rotor

Under hard braking, the ball rolls upslope and reduces the fluid pressure to the rear circuit - thus proportioning the fluid more towards the front brakes.

I'd like to see how a tiny metal ball overcomes 2000 psi of hydraulic pressure purely under braking forces, which might hardly touch 1g on the Sierra.

[Rigid Rotor]

@Veyron1 - I concede the point - LSPV does appear to be a generic design component to automatically adjust brake bias and as per available internet literature - is mechanically linked to ride height of the rear suspension. Frankly, its been about three years since I sold off my NA Sierra (along with that dammed manual !!).

- notwithstanding, I still very clearly remember that the NA Sierra manual is explicit about the "upslope ball" component in the brake circuit that I mentioned earlier.

@Ananthkamath - well you have a point on a 'tiny metal ball overcoming 2000 psi of hydraulic pressure purely under braking forces, which might hardly touch 1g on the Sierra.' - but as I said earlier - we need a Sierra manual to settle this point on the exact functioning of the "upslope ball" component - and now I'm on the hunt for a manual and will get back to you with the exact text!

- and hey Subache ! so sorry for the diversion - if I get my hands on a Sierra manual (again), you will definitely be the first to know!!

[Mpower]

Originally Posted by veyron1

@Mpower; if the front nosedives and the rear does come up, the LSPV is supposed to reduce the fluid pressure to prevent the lock-up, ain't it...

LSPV as I understand it works under steady state conditions and not under transients.

Originally Posted by Rigid Rotor

as the Sierra manual describes it - it works on the principle of a ball mounted in a cylinder that's tilted up from the horizontal -

post a pic of the text in the manual

[vijuvarghese]

Here the description of GP valve from Sierra manual

[underground1419]

What is the top speed of the Sierra turbo? I read its 130kmph in many of the posts in this forum but I've also seen a video of a sierra touching 160kmph on this forum!