m30 on carbs?

[e30Alex]

What are the pros and cons of and m30 on weber 40s or 45s?I think it would look and sound awesome.Apart from the fuel economy, what are the drawbacks?Would the ecu still work for the coil etc???Cheers Alex

[Turbo-Brown]

The cons are that carbs are cack when compared to throttle bodies

Think you'd lose the load dependent ignition advance as I believe the standard ECU would need the AFM to work properly.

[e30Alex]

laffin, it was just a thort.Alex

[Brianmoooore]

Carbs are museum exhibits!

[johnna]

If you want to try to arrange perfect stoichometric air/ fuel ratio using a collandar and a straw, go for carbs...


That said, a set of six bike carbs would be fruity fruity fruity!!!

[Turbo-Brown]

That said, a set of six bike carbs would be fruity fruity fruity!!!

Still got the same problems of using the fueling equivalent of an abacus to work out your engine's fuel requirements though.

[johnna]

That said, a set of six bike carbs would be fruity fruity fruity!!!

Still got the same problems of using the fueling equivalent of an abacus to work out your engine's fuel requirements though.

Yes, I take your point, but one carb per cyl on a straight in pipe will be a lot more accurate in operation than a single carb feeding mixture down six pipes or a twin set feeding three pipes each. Plus bike carbs often come with throttle pots, allowing an megajolt light jr set up (or similar).

There is a reason why all car and bike manufacturers have adopted efi though! It is better in every respect.

[Turbo-Brown]

Think if you wanted to skimp on the webers, you could use one so that each choke served three cylinders, but going for two and having three cyls feeding off two chokes would cause probably massive overfueling to one or two cyls.

Ideally, if you wanted webers, you'd have three carbs which each have the two chokes giving essentially six carburettors.

EFI is the way to go though, and throttle bodies just make that all the schweeter

[gareth]

the only thing to remember with carbs is the noise! compare a the sound of a 2 litre injected sierra with a mk2 rs2000 on 45's and a lary cam. no comparison!!! carbs sound soooo good. it's mustly the gurgling noise of the fuel being pumped into the engine by the gallon!

actually, my old mk2 rs2000 (180bhp on 45 dcoe webers, rally head, daft compression and a full rally spec cam) used to use fuel at a higher rate than the original fuel pump could deliver. this limited the top speed to about 135 before massive fuel starvation happened. a high capacity fuel pump soon sorted that! the downside was an average of 16mpg on a run and 5mpg caning around town

i'd still sell my left nut for another one though!

i've not heard a M20 or M30 on carbs other than our old E21 320/6 (m20 with a shiiiiiite peiburg cab) and that sounded really nice. something i miss with injection. oh, the burbly over-run too... as the carbs still throw fuel away when you're off the throttle!

[DRIFTBOY]

I agree with the noise thing!

I went out in a mates tuned (160bhp - proven on the rollers) Mk2 Escort RS2000 last week and the noise gave me a semi !

The old Ferraris and Lamborghinis sound so much more raucous on their multiple carbs too.

Martin.

[Speedtouch]

My old 1275cc Minor and 1860cc MGB sound quite rorty with their SUs on the overrun too - with lots of popping and farting from their crude exhaust systems

[gareth]

tell you what martin, driving a RS2000 is hard when you have 2 gearsticks to choose from!!! mine used to have the same effect on me. it also had a single box 2.5" exhuast

what torque figure is he putting out btw? i had 180bhp / 135lbft at one point but when i played about with slightly smaller chokes and tinkered with the cam timing, it made about 165bhp and 160lbft which on the road was a LOT faster. it had a nearly flat torque curve from 2k to 8k!

this is one of the reasons people who quote only bhp figures make me laugh! also the reason i have a M30

..... and i have been very tempted to fit carbs!

[johnna]

http://s15.photobucket.com/albums/a366/ ... =pinto.flv

listen to it!!!!

But I replaced that with this:

[DRIFTBOY]

Gareth - I can't remember my mates torque figure, he did tell me, but it's nicely set up and pulls like a train from quite low revs, as a good Pinto should!

That was a reason I chose the M30 too.

Johnna - I can see that's a Capri! I love those too, my best sounding car was a 2.8i with naughty exhausts!
Might have sounded better on triple twin chokes though!

Martin.

[Hadrian]

So different choke sizes can change your power:torque bias? This couldn't be done with fuel injection.... could it?

[johnna]

Yes, by varying the length of inlet plenum runners, especially on injected TB's.

[gareth]

pinto porn!!!! i do still love those engines and it's possible to get more than 100bhp / litre from them on carbs though it'll cost an arm and a leg.

So different choke sizes can change your power:torque bias? This couldn't be done with fuel injection.... could it?

yes! this is why multivalve engines with their better breathing and larger ports etc generally have more power but less torque that a 2 valve / cylinder version.

the 8V versus 16V golf is one of the best examples of this. a 8V golf will hold onto a 16V golf the whole time you're on a twisty road with a lot of speed fluctuations but the 16V will outrun the 8V in a straight line.

this is all VERY generalistic by the way but the principle is there!