10 replies to this topic

[kwacktastic]

After a few months of pontificating and cogitating (you can get arrested for that in some counties!), I finally took the plunge and shelled out for a new alloy throttle body from Minispares. The unit supplied (manufactured by Burlen / SU) was very straight-forward to fit - the entire job took less than twenty minutes. The car now idles consistently at 800rpm without a hint of wavering. Throttle response now seems much crisper too.

The old unit was inspected and no obvious faults could be found - there were no cracks, nor was there any distortion (detectable with the naked eye). There must have been something not right though!

Suffice to say, I'm delighted with the results. The only downside was the cost - £150 all in. A bit on the steep side, but ultimately worth it in my opinion as it's made the car even more pleasurable to drive!

Any MPi owners suffering similar idling problems may therefore want to consider replacing their old plastic throttle body with an alloy version before they consider replacing expensive MAP sensors, Lambda sensors, etc.

Hope this is of use.

Cheers,

Kwack.

[BabyBek]

Thanks for that!!

Mine's been a little erratic, nothing too noticable, but u know its not quite settled, if you know what I mean!!
Good mod to start saving for!!

[Darc]

Thats my Next buy, i Take it the ECU dont need to be modded in any other way, Just got to buy the 52mm (i think) body an fit it is it as straight forward as that?

[kwacktastic]

I chose the 48mm version as that's the standard size. There is a 52mm version available but that's intended for cars with highly modified engines (as I understand it).

No modifications to the ECU (or anything else) are required apart from the need to remove one of the fuel rail clamps (replaced with a cable tie) - this is due to the fact the Minispares version has a throttle butterfly which fully opens (i.e. 90 degrees) when compared to the standard plastic version which only goes to three-quarters open (about 75 degrees).

All-in-all, a very straight-forward modification!

[miniboo]

i think you can fit the 52 mm throttle body as a way of upping the power on a fairly standard engine.

One of the minimags did this month not sure which one.

The ecu is good for upto 90 Bhp i believe.

the way i see it, it is like fitting a 1.75 inch su instead of a 1.5 inch. Does that make sense?

[kwacktastic]

The literature that came with the kit showed a graph of output power against revs for the two versions. Both are very similar up to 5000rpm, after which the 52mm version offers better results. Up to 3bhp extra at the top end seems to be typical. The trade-off is that fuel consumption apparently increases significantly. There's also the slight risk that the engine will be over-fueled (i.e. very rich) which could ultimately result in damage to the cataytic converter - nasty!

[THedooBZ]

The trade-off is that fuel consumption apparently increases significantly. There's also the slight risk that the engine will be over-fueled (i.e. very rich) which could ultimately result in damage to the cataytic converter - nasty!

yup this is right, it would overfuel, your best off leaving the size at the standard 48mm.

[miniboo]

i thought that the ECU would adjust as necessary?

[kwacktastic]

That's a chance I wasn't prepared to take! There are easier (and cheaper!) ways of getting a few extra bhp - I viewed this modification as something that needed sorting before attempting to get extra power. It now runs beautifully and actually feels slightly more responsive than before. I'm happy with the 48mm version!

[Sprocket]

i think you can fit the 52 mm throttle body as a way of upping the power on a fairly standard engine.

4BHP max Whooppee

Also why would it over fuel, you are alowing more air to be drawn in, if anything it will be lean. The ecu will ad more fuel to compensate for this, but then the engine will only consume as much air as its Volumetric efficiency will alow and so the fueling will be much the same, fitting a bigger throttle body does nothing if the engine does not need the air. what it does is increase response. Also the 3 or 4 BHP extra is at the top end because the standard plastic itwm does not open fully anyway.

[kwacktastic]

The figures quoted by the supplier show the 52mm version is significantly better at the top end than the 48mm version. Both versions open fully (i.e. 90 degress) so there's more to it than that. Either way, my Mini will very rarely see 5,500rpm so I saw little point in going for the larger version.

You may well be right about the ECU compensating. I spoke to quite a few people about this and read quite a few reports on the advantages and disadvantages and concerns about over-fuelling seemed to come up frequently, not to mention concerns over rough running and fuel consumption. Minispares quote the following regarding the 52mm version:

"FOR TWIN POINT CARS ONLY THIS BODY IS 52MM WHICH IS OVERSIZE AND FOR USE WITH OTHER TUNING MODIFICATIONS .THE ECU MAY REQUIRE MOFIFICATION FOR BEST RESULTS"

The Burlen literature makes no mention of modifications required to the ECU and goes on to claim up to 10% power increase at the top end when used in conjunction with a performance exhaust. As you say - whoopee! For out-and-out racers, I'm sure there's a gain to be had. But for old farts like me, using the car on a daily basis its likely to make little if any difference.

At the end of the day, you pay your money and you take your choice. I made my choice and I'm merely reporting that I'm happy with it.