12 replies to this topic

[tango gt]

Hi, Im looking to put twin HS4 carbs onto my Mainstream Cooper which is basicaly a 1275 mg metro engine roughly 73/5 bhp, I was just wondering if anyone would have any clue as to how much my BHP increase would be so I can let Footman James know

[AndyMiniMad.]

Im prety sure that by fitting twin carbs your insurance will increase..as they are seen as a performance modification....However you wont actually gain any BHP.. so whats the point...Unless its for the looks...some people like the look of twin carbs..particularly as you are driving a cooper...And possibly you might notice a slight improvement in throttle response. But in my opinion they are more difficult to keep in tune...I would stick to the Hiff44 that was standard on the Mg metro engine..

[liirge]

They are also louder, if that floats your boat!

Edited by liirge, 19 September 2011 - 06:49 PM.

[Pigeonto]

Hi, Im looking to put twin HS4 carbs onto my Mainstream Cooper which is basicaly a 1275 mg metro engine roughly 73/5 bhp, I was just wondering if anyone would have any clue as to how much my BHP increase would be so I can let Footman James know

I'm with Footman James and said that I will eventually be fitting twins and they said to tell them when I have done so but it will not affect the premium.But then again I'm a couple of years older!!!!
Incidentally, I can speak from some experiece regarding the result being as I have just done exactly what you are considering:-Andy MM is probably right with your spec.But I improved upon my MG engine spec by using a Piper 270 cam and a little higher compression ratio and an LCB ehxaust manifold/decent system and boy what a difference the twins made. I'm having twins from now on.

[jaydee]

They surely increase fuel consumption!



Really, improve cylinder head before, and the twins wont give you more HP but will improve torque.

[liirge]

They surely increase fuel consumption!



Really, improve cylinder head before, and the twins wont give you more HP but will improve torque.

Oddly enough I've seen in a lot of cases the exact opposite (in terms of fuel consumption)- this is mainly with the fitting of twin HS2's, rather than the 4's. It makes sense that if you go from a single HS4 to twin HS2's you will save fuel on part throttle.

[tango gt]

Thanks for all the help guys, the only reason i was after bhp numbers was to tell insurance as they tend to ask. all im after is the low down grunt and like you say the instant throttle response and torque.

as for "liirge"'s response, i have a sony xplod with a volume button

[jaydee]

Thanks for all the help guys, the only reason i was after bhp numbers was to tell insurance as they tend to ask. all im after is the low down grunt and like you say the instant throttle response and torque.

as for "liirge"'s response, i have a sony xplod with a volume button

Just tell them there wont be any power increase, its an equivalent carb..
and if they want to charge you for the look, tell em a lie like you're replacing becuase the HIF broke down

Edited by jaydee, 20 September 2011 - 05:18 PM.

[Yoda]

Hi Guys.

Thought i would add a comment or two!
Andyminimad, Just so that you know, TangoGT is now running my old car and to do this (for insurance purposes) we removed the high spec 1380 engine and fitted the Metro MG engine due to it being the correct spec for the mainstream cooper with the exception of the diff ratio. We understand all the aspects of running twin carbs and how to tune them! they do NOT go out of tune, you will definitely see much better mid range response and you WILL see an increase in BHP.

It is not intending to be done for looks either.

The carbs have only done a couple of thousand miles from new too, so no worries regarding worn spindles etc.

Liirge, I think you know we like the extra noise when flooring the LOUD pedal

Jaydee, we also know about the fuel consumption increase, but that will only happen because with the extra response, one tends to hit the loud pedal harder. Driven sensibly with a well set up pair of HS4's, you can actually get better economy due to a better burn percentage wth the more even flow of gasses.

The actual question was " I was just wondering if anyone would have any clue as to how much my BHP increase would be so I can let Footman James know "

[jaydee]

Yes but practice, however, differs from theory, who in the real world will drive sensibly twin HS4s?
Once you'll hear the noise and the pull, you'll have lead foot

[tango gt]

And that jaydee, just about sums me and my old man up!

[AVV IT]

My understanding is that adding twin HS4's won't add any power unless the engine was underfuelled by the HIF44 in the first place, which isn't likely!! I was also of the understanding that Footman James used the rather simplistic formula of calculating modification premium increases proportionally to actual BHP increases (i.e. 10% more power = 10% increase in premium). So therefore no power increase would mean no increase in premium either, but you would still have to advise them of the mod though.

[liirge]

Hi Guys.

Thought i would add a comment or two!
Andyminimad, Just so that you know, TangoGT is now running my old car and to do this (for insurance purposes) we removed the high spec 1380 engine and fitted the Metro MG engine due to it being the correct spec for the mainstream cooper with the exception of the diff ratio. We understand all the aspects of running twin carbs and how to tune them! they do NOT go out of tune, you will definitely see much better mid range response and you WILL see an increase in BHP.

It is not intending to be done for looks either.

The carbs have only done a couple of thousand miles from new too, so no worries regarding worn spindles etc.

Liirge, I think you know we like the extra noise when flooring the LOUD pedal

Jaydee, we also know about the fuel consumption increase, but that will only happen because with the extra response, one tends to hit the loud pedal harder. Driven sensibly with a well set up pair of HS4's, you can actually get better economy due to a better burn percentage wth the more even flow of gasses.

The actual question was " I was just wondering if anyone would have any clue as to how much my BHP increase would be so I can let Footman James know "

I don't even know why i bothered writing that comment earlier, everyone loves the twin SU noise!