ZF 4HP22

As that man said. And I'm sure he'll correct or clarify anything else I've stated above, as necessary.
 
WarrenL said:
rp61973 said:
Seconded. My late Type 35 was rebuilt 2 years ago by Harvey's colleague. For what is commonly know as the 'clunkomatic', my 35 'box is smooth and very nicely setup. I am sure the 4HP22 is a great conversion, but I would never foresee any reason to convert my P6 in a similar way.
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I'll give you one BIG reason! Overdriven fourth gear and the accompanying lock-up torque converter. In one fell swoop you've removed the P6B's weakest link - its frustratingly low gearing on the open road. A second reason, particular to my situation: the 35 had crapped itself and I had to do something. With what we already collectively knew about the ZF it seemed pointless to me to rebuild the 35, but if you've already gone down that path then you'd be rightly reluctant to upgrade to the ZF. You guys are both perfectly correct in that a well set up 35 is a good box, but you need to experience the ZF before you dismiss it. The difference in refinement and shift smoothness is a revelation, as Graeme points out. It is far superior to any BW35/65 in any state of tune that I've ever come across, in Rovers, Jaguars, Fords, etc. You're looking at 20+ years of progress in transmission design just for starters. The seamless shifting up AND down (you hear the engine change but you feel nothing) as you drive around the town, the quietness compared to the 35, the directness of the box (the car no longer feels as if it's winding up its rubber band to get going), the way you can control the shifts with the throttle: it's all a big improvement. And as soon as I nail the 4th gear upshift problem I'll report back on the real fruits of the exercise. But even with only the first 3 gears operational I can already feel the upgrade has been worth the significant effort involved.

It's a pity that, here in far-flung Christchurch, Graeme is the only Forum member who has been able to experience my car first hand. I'd like to make it an open invitation to all to who pass through to try the ZF out and form their own conclusion.
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I don't for one second doubt what you say and far be it for me to dampen your effusion, but I was responding specifically to the two points you made regarding kickdown response and a clunk on changeup to top gear. None of which should be present in a well set up T35.
 
Effusion:- a sudden and uncontrolled expression of strong emotion.

Yes you definitely need a cloth, if not a mop and bucket. :D

Jim.
 
Thinking more about this, and speaking to Andy eight of them, I'm planning on sourcing a hp24 now.
After my current engine rebuild my configuration will have ported sd1 heads with bulleted guides and waisted valves, stainless headers/tuned length exhaust, CD ignition, crower mild cam etc...estimated torque/hp should be getting near the threshold of what the hp22 can handle.
Since I want the box to last as much of the car's lifetime as possible, and bearing in mind I'm bound to up the capacity at some stage to 4.2/4.6, for me it makes sense to get the hp24.
Jim
 
Hi Jim,

As far as I am aware, the ZF 4HP24 is an electronically controlled box.

With those intended engine mods, why have you decided on an auto transmission with overdrive?

Ron.
 
As a complete box, you are quite right Ron. But the HP24 internals fit into the HP22 giving you the required torque upgrade but with the HP22 cable control and Range Rover valve block.

I must say I really don't understand your antipathy to the ZF boxes, Ron. If you feel the overdrive top is too high a ratio you could always lower the overall gearing with low profile tyres - which in some ways would be an advantage in itself. The prime objective of using the ZF boxes is to obtain a box which can be readily fitted to the car that has torque convertor lock up. This is an absolutely huge technical advance over the BW boxes. And therefrom spring major advantages in fuel economy. The overdrive top is a further bonus for those of us that do many motorway miles and feel that the car in standard trim is undergeared (leaving aside the oddity of the apparently even further undergeared NZ cars - I wonder if they used 2200 diffs?) The issue is not, in my opinion, about torque capacity or about change quality. I'm sure you are quite right in your praise of your uprated BW, for my part I'm perfectly happy with my standard BW35 on both scores. The advantage gained from the TQ lock up and the overdrive are game changers in terms of the usability of the car here in the UK. Against these, the ZF would have to be horrendously unreliable (which it doesn't seem to be) to put me off such a conversion.

Chris
 
Hi Chris,

Yes I am aware of fitting the 24 internals into the 22 case, I actually mentioned that very thing a few posts back :wink:

I don't have a problem with the ZF box per se, rather I was asking Jim why he wanted to run an automatic transmission (any automatic transmission) behind his intended 3.5 modified engine.

Ron.
 
SydneyRoverP6B said:
Hi Jim,

As far as I am aware, the ZF 4HP24 is an electronically controlled box.

With those intended engine mods, why have you decided on an auto transmission with overdrive?

Ron.
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Is there not an early version of the hp24 which isn't electronically controlled?
Ron. I like the car being an effortless auto, but also want it to be able to change it's character if you like..
That's partly where the B&M ratchet shifter will come into play, with the ability to manually quick shift.
My car is definitely a custom, but will maintain certain charms of the original well designed car.
I guess I'm aiming for a "grand tourer"
I'm at the very early stages of learning about these boxes, but my 35 is currently needing work and an upgrade now is as good a time as any

Jim
 
Whilst there are two basic versions of the HP22 - cable controlled and electronic, all HP24's are electronic. Hence the need to cobble 25 innards into a 22 box to suit our cars.

Chris
 
Corazon wrote,...
After my current engine rebuild my configuration will have ported sd1 heads with bulleted guides and waisted valves, stainless headers/tuned length exhaust, CD ignition, crower mild cam etc...estimated torque/hp should be getting near the threshold of what the hp22 can handle.
Click to expand...

Hi Jim,

Just one other point, those intended mods won't go anywhere near pushing your engine's maximum torque to test the torque handling threshold of the ZF 22. Indeed, under around 3500 rpm you'll see a loss of torque, with the peak occuring further up the rev range. An example being the Rover Vitesse engine which delivered a maximum torque of 220lbs/ft at 4000rpm, some 1300 rpm revs higher than the standard P6B engine with its small valve heads. Maximum torque for the P6B engines ranged from 226lbs/ft down to 202lbs/ft. The standard SD1 engines delivered less torque, dropping to 182lbs/ft.

Ron.
 
Ron, my choice also must take into account potential future upgrades in capacity, perhaps to a 4.6 as you have :D
But with the current configuration for example, I'm being very cautious about what cam I choose.
I've been doing lots of calculations based on Vizard's cam event criteria. So far off the shelf, the Crower 50229 seems the closest to what I want.
Tuning the length of the secondaries ( I want to do a dual exhaust with balance pipe) should also help to keep the torque where most useable.
Saying that better breathing heads will automatically equal less torque seems to contradict a lot of what I've read. Porting can make great gains in both departments if done correctly.
Out of interest, are your heads the factory 4.6 items?
Sorry for clogging up the zf thread!
Jim
 
No Jim, it's not the porting that reduces low rpm torque but the bigger valves of the SD1 heads. In essence any change that improves high rpm breathing has a trade off in reduced low rpm torque. That applies to cam profiles and to valve sizes.

I have a pet view of how to design an engine for maximum driveabilty for a given performance. It is to get the basic breathing, combustion chamber shape etc etc as good as you can get it. That will involve big valves, big exhausts, matched and polished porting etc. Then redress the balance with a very soft cam. I arrived at this conclusion after owning a BMC 1300GT which effectively has the Cooper S engine with a fractionally milder cam. An absolutely superbly mannered engine with the ability to rev its nuts off when required.

The combination of the small valves and the standard cam in the P6 is really very good. It clearly needs the top end opening out if doing anything serious, but going to a head that breathes much better requires some caution. You might find the standard cam is then already too fierce.

Chris
 
Good idea Ron :)
I think we've slightly misunderstood each other at some point, we're after the same thing essentially- just from different angles.
Chris, most of the ideas I'm trying to put into practice are coming from Vizard's extensive dyno testing, not any personal real world experience, yet!
The kind of porting I'm talking about is to do with generating higher swirl, unshrouding valves/combustion chamber work etc not enlarging ports.
This combined with perhaps a slight increase in compression and the correct cam can certainly see an increase in both peak torque and horsepower.
Dyno results of similar work have seen either no loss to the low rpm torque and higher peak torque elsewhere, or an increase in peak torque below 2500rpm..
The only slightly larger sd1 valves combined with the bulleted guides and smoothed valve throats should take care of the higher rpm gains without impacting on the low end from my research..
Although perhaps not too obviously, I am actively trying to create a motor that's works optimally with an auto box.
The main point of choosing the hp24 of course is one of preparation, as I will increase the capacity at some stage in the future. Be it months or years, the hard work with the gearbox will have been done and ready to accept what I throw at it :D

I don't claim to know a lot about this, but I'm learning as I go and don't mind making a few (not too costly) mistakes on the road to enlightenment :wink:
Jim
 
Road test in 4th gear.

LATEST!

My missing 4th gear has been found (valve body problem) and Brown Rover has been road tested: 2200rpm at 100kph, and the difference is amazing! For a direct comparison with the old setup, you need only move the lever from D to 3. In 3rd (the same old 1:1 as the old top gear) the car is busy, but let it shift up to 4th and the engine noise dies away and the car seems to just lope along effortlessly. It is a huge difference. A quick prod of the loud pedal immediately reinstates 3rd for a spot of overtaking or a run up an incline, and then you're back to near engine silence. After all the hard work, I'm absolutely thrilled that the difference is so noticeable.

Bit of bureaucracy now. I'll have to book the car in for low volume certification, then a WOF and registration. The LVC might be a couple of weeks away, I've been warned, but my 3 month registration hold expires about then, which is perfect (if you re-register before the minimum 3 months hold is up they backdate it, the swine).
 
Excellent news & a comparatively short period between your BW35 meltdown & successful marriage of your ZF's into a functioning unit for Brown Rover.
 
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