[Dorchester]

At last it arrived after being stuck during a whole week in Ebay international hub Litchfield.
Magic reference: MHB 000261.
A Spanish rogue on Ebay tried to sell me a mere 48mm one telling it was the right reference!
I required a refund: agreed even without sending back the crap.

It'll be a direct swap in the missus 25 1.4.
What to expect?
A a trifle faster response and maybe 1 or 2 hp and that's it.
Doesn't worth it?
Mind that I only paid £35 and it's in pretty good nick.
But it's still too cold for an outside job the garage isn't heated.

 

[LeRich]

If you're upgrading from a restricted TB then it'll be a noticeable difference. You'll need the cable too.
If you're upgrading from an unrestricted 48mm TB then there'll be negligible improvement.

 

[Dorchester]

If you're upgrading from a restricted TB then it'll be a noticeable difference. You'll need the cable too.
If you're upgrading from an unrestricted 48mm TB then there'll be negligible improvement.

Initially the engine was a 84 cv one.
I'd already derestricted the genuine 48mm TB, and the solution is far simpler for a LHD than for a RHD one.
Initially the TB opened at half way only. I only cut a small plastic bit and hey presto the TB was fully opening. No need to change the cable.
I know the improvement from 48 to 52mm will be tight but I need to add that

• the engine is fuelled with full E85 (ethanol) which has already improved the responsiveness of the engine (E85 is octane 105),
• that I've modified the box with 5 holes at the bottom to ease breathing,
• that I've fitted a GREEN cotton filter which lets the air flow even a tad more freely than my previous K&N,
• and icing on the cake that Steve Abbott (Saws Tuning) has improved the advance on another ECU while desarming the immobilizer so the ECUs were swapped.

I hope the 48-52 difference will be slightly noticeable to complete all the previous improvements. Fingers crossed.
we'll see.

 

[gnu]

You’ll have to let us know

 

[Dorchester]

Job just done!
The result is impressive and it's impossible to say it's only feeling or placebo. Not at all: easy to notice the difference before / after.
The throttle response is absolutely immediate, beefy and massive. Not any delay: it's brutish!
Hence it gives very fast accelerations: I'm chuffed!
The diameter difference doesn't look that huge, only 4mm, but in my math that's 17% more air flow which is far from negligible.

Indeed that doesn't make a very sensible difference in bhp: it's the same engine, bore, stroke, you name it but when accelerating it's stunning and it can glean some precious tenths of second if not a few more. Very useful when overtaking or changing gears while uphill: faster than before going up in the revs.
I'm dreadfully curious to know whether my better half will notice any difference: place your bets!

The job was easy but one mod I've to do: drilling another hole to insert the end of the cable on one side and dig a little groove on the same plastic arm at the other end where the cable is to be inserted.
It wasn't intended to be fitted in a 1.4 indeed. That's why.

In the beginning I was puzzled because the length of the cable wasn't adequate then no direct fit but after a good five o'clock tea, I was clear in my mind.
Just enough time to take the exact measures to avoid a mess and that was it.
Then I asked my better half to give me an eye and a foot to verify that all was fine when pushing on the pedal and hey presto rebuilding the whole stuff including the bar strut and testing on the road the brilliant result. And don't forget to push 5 times on the pedal with the key in 2nd position to reset the TB.
Phew!

 

[Dorchester]

We shall go to a good restaurant next Sunday: exceptionally I'll drive the missus 25 and on a lovely country road which I know well I'll see the result on a 90 km (56 mls) round trip.

 

[Dorchester]

Miraculo!
My better half made her first drive this morning with the new 52mm TB and went for some shopping.
I came with her as a passenger.
And at some moment she noticed the acceleration was better.
Hurray!
That's THE evidence...
Bonkers!

 

[Dorchester]

Well back from our Sunday trip.
I can't confirm my first feelings... It was understated actually!
In fact it's even better than I'd thought in the first place...
More grunt, more oomph and she pulls harder and faster as soon as I push a little on the pedal.
It looks I'm driving a GTI now!
Another blatant evidence: on well-known twisty country roads I can now easily drive uphill in fourth gear when it was a bit easier to drive in third previously.
With all the little mods I'd done before, it's the one essential that was needed to complete the job.
Every little helps as one says...
It can't be better now.

 

[gnu]

Great result! I’ve looked them up, you can get them for around 60 Euro. So seems a good upgrade. By the sounds of it you used the original cable etc.

 

[Dorchester]

Yes I was very lucky to find one in England via Ebay for a very fair price (£35 + shipping + custom taxes).
Initially the engine was restricted to 84 bhp (opening only at half). I'd just cut off a little bit of plastic and then the TB was opening fully.
Before the TB swap, my 103 bhp 214 cabby - same engine as it looks - gave me the impression to be swifter, more lively & efficient than the 25 1.4 hatch.
But now as I've driven both cars on the same twisty and hilly country road, I can ascertain that now the 25 1.4 has unquestionably more torque than the 214 cabby.
And mind that they have got both same air box mod (holes) & same K&N filter, and both cars have approximately the same weight.
The only difference now is the TB: 48mm in the 214 cab, 52mm in the 25 1.4.
To be fair I've to add that the ECU in the 25 had been slightly remapped, essentially improved advance. Despite that before the TB swap, the cab looked slightly better.
Today in the 25 I was driving uphill on some parts of the route easily in 4th gear, when in the cabby the 3rd looks more appropriate & efficient.
The 25 is my better half's car: I'm jealous now!

 

[Dorchester]

You're quite right: same cable. It was easier to play with the black plastic arm.
On the 52 TB there are actually 2 parallel grooves but neither of them was convenient, one being far shorter and the other a bit too long.
I took the best possible measure to fit the cable in accordance with the pedal travel in the cabin.
Then I choose the longer groove and drilled a similar hole cum notch at the farer end, and opened the same groove at the closer end because it wasn't open.
I took enough time and did my best to finish the job nicely with several files as if it had been done genuinely from factory.

 

[Man in the Car]

Your use of E85 may be having some impact on the improved performance - fitting a 52mm TB was quite popular on the 1.4 ZR in the early days, but those who did so only reported an improved throttle response. Several of those who tried them on a rolling road after fitting a 52mm TB actually found it had given them a reduction in power, so it was always a mod which folk were discouraged from doing for that reason.

The changes that you had done when converting to E85 have perhaps left it better able to utilise the (presumably) improved airflow?

 

[Dorchester]

You're quite right as well. The only example I've got is my KV6 2.5 when she was remapped in July 2021 by a well famed and respected race circuit tuner garage.
As expected they took measures before and after on the bench i.e. at the wheels. Hence I've converted them to match with the factory figures done at the flywheel (converted as well from metric value).
Mind that all my mods (air box, cotton filter, resistors for E85 and full SS MIJ exhaust line) had been done before and that the car was fuelled with full E85 (i.e. 85% ethanol in Summer).
The 75 was given 195 bhp before the remap, that is 20 bhp more than from the factory... And 203 bhp after the remap that gave only 8 bhp more, because they were a bit uneasy with the Jatco auto box. They are obviously used to remap more modern and powerful cars nearly exclusively with manual box! But they did a very good job. Mind they tested the car before because they were very dubious about my E85 home made mods (they are doing the conversion themselves). They told me in the beginning that unless the engine and the car were perfect they will not go further. I was shaking in my boots as you may guess... After a very close exam they found her in very good nick for her age and accepted the deal. Phew!

Hence we may guess that both my not tested K4 engines have already made significant gains from their home made conversion to E85. That's another important parameter indeed.
Anyway the difference between the 2 engines after the 52mm TB swap in the 25 does give the evidence that in the 214 mk2 cab the E85 conversion was not yet enough because she keeps her factory fitted TB (by necessity, I haven't found any straight alternative) when the 25 is obviously enhanced by the 48 to 52 swap so much that now the test on the road has inverted the positions: the 25 from second becomes first.
Supplementary holes at the bottom of the air box to feed with more air, and a tad warmer as well (which is meliorative for ethanol but detrimental for petrol BTW) plus cotton filter less restrictive were likely not enough to take full advantage of the difference. Remained a restriction at the 48mm TB. Now it looks that the flow is coherent and not reduced as before.
At least that's the lesson I'm inclined to learn from the experience when I'm taking all data and parameters into account. But you may be right despite that: a TB swap in the first place without any other previous mod might have lead to another conclusion.

EDIT: but incidentally if a better air flow from the box for the above reasons isn't sufficient with a 48mm TB, maybe the reverse may be true: fitting a 52mm TB without improving the air flow within the box. I'd noticed a big improvement at least in the throttle response in my KV6 the day I drilled the holes at the air box bottom...

 

[Dorchester]

Some afterthoughts...
As I'm neither an engineer nor a mechanic but a pragmatic man who does some empirical tests, I'm inclined to think that every stage in a chain are the following and that they should be coherent:

1. the air box opening diameter
2. the filter
3. the TB diameter
4. then the mix taking into account several parameters such as kind of fuel & octane, ECU parameters, injectors, you name it
5. the engine itself witch is even more complicated for a ignoramus as I am
6. the exhaust line

I have nothing more to add regarding the 2 first stages, but the 3rd one: only upgraded in the 25, but stock in the 214 and the 75.
I shall say nothing about the stages 4 & 5 I don't know a jot about. That's engineer business.
The 6th stage resulted in 3 different solutions among my 3 Rovers:

• 214 cab: no mod. I didn't found anything suitable so far.
• 25 1.4: swap of the factory back box for a 1.8 VVC one with a slightly larger diameter (+ 0.5 inch) and twin pipes.
• 75 V6 2.5: swap of the factory line for a full SS derestricted exhaust line.

That may be clearer now... in my mind as well.

 

[Dorchester]

Here is another one at a very fair price (last one at the seller's):
52mm TB MHB 000260

 

[markvrs]

Hi, You can get brand new 52mm throttle body with TPS fitted from MGF&TFBitz for £60.95. Works fine on my 200.

 

[Dorchester]

I guess you've got a 200 mk3 bubble shape don't you?
Because those 52mm TB don't match with the mk2 ones. I'd thought I could fit my 52mm in my 214 cabby and I can't.
That's why it ended in the missus' 25.

BTW I've got now one last thing to check: how a 52mm TB could affect the mpg. I bet it depends largely upon the driver.
Whether you take the opportunity of using full extra torque or not... Otherwise heavy foot or not.
Is my better half to change her driving habit or not? I place my bet on the latter.
We'll see...

 

[markvrs]

Hi Dorchester,

My bad, yes I do have Mk3 bubble 200. The 52mm Throttle Body I mentioned from MGFnTFBitz had the same part number that you mentioned in your first post, and on the picture. (MHB 000261) so I assumed it was what you were after, I misunderstood somewhere, sorry. It was a straight fit replacing my 48mm, just rerouting original throttle cable onto different grove in TPS crank.

Cheers markvrs

52mm Alloy Throttle Body Item No MHB000261

£60.95 GBP

1

 

[Dorchester]

Hello markvrs, have you had a close look on the price of the one I gave the link to?
£33.33!