Single vs twin su's on N/a application
Turbo Mini Forums

Is their much difference in them between perfomance.

I am considering trying to track down a pair of twin 1.5 su's for the n/a engine I'm building. Spec someting along the lines of

1275cc
286 cam
10.5:1 cr
light flywheel
Sorted head
possible 1.5:1 rockers.

how would drivability and power potential compare to a 1.75 su

Thanks.

Edited by minimole23 on 24th Apr, 2008.

it would be a bit better than a 1 3/4 but i would still use the hif 1 3/4 less hassel you would only lose a couple of nannas and better fuel econamy

always looking for them bigger bunches of bannanas

IMO the key factor is not the number of carbs but the manifold design. There's a shed load on twin carb manifolds in TBASE.

stick with a MG manifold and SU hif 1.75" correctley callibrated

theres loads about and there hard to beat
hoggy and rob says.....

I had a 1380 with twin 1.25s about 20 years ago only about 90bhp but used to achieve 40mpg - so I always believe that whilst more difficult to set up twin carbs give better results

On 5th Sep, 2011 Vegard said:
I stand corrected. You should know

From my experience the 1.75 was ok on say 1330 with 285 style cams, once the capacity went up and the cam duration/lift along with it twin 1.5's on steel manifold was better - but not as good for torque or power or driveability as a weber 45 on mapped ignition!

if you have the chance bin the 286 kent cam its not a particularly nice grind and doesn't produce the beans at the top end or the torque low down - now the 296 on the other hand!

If Carling made Mini engines
it would probably be like this one!

Thanks all.

What sort of power band would you be looking at for the 296? I'm not that fussed about drivablilty!

Revs will be kept to 7000 to help reliability.

I wan't to build a nice n/a engine before going seriously turbo in the future.

well a 296 is real torquey until about 2200rpm, then it drops off the face of the face of the earth until about 3200 rpm when it wakes up and comes on strong from there all the way. To stop this being a real pain daily you would need to run something like a 3.6 diff on 10's to keep the motor from needing gearchanges to keep it out of the "off cam" band. The 286 has similar characteristics at slightly lower rpm, ie drops off at 1500 ish and comes back at 2500 ish - but it doesn't produce the goods in the mid range or top end like a 296 with 1.5 rockers will.

hope this helps a little

If Carling made Mini engines
it would probably be like this one!

Thanks.

I'm planning to run a 3.44:1 and I'm on 12's with pretty much the same rolling radius of 10's due to the tyres.

Its all good stuff to consider:)

296 is pretty fierce for road use i guess
If you wanted something like a 286 without the mid range hole.

You could try a RE13PP. I have an OT version and that you can (just) potter along at 2000 rpm (3.1FD) in 4th and it will rev to about 7 K-isch.(probably more)

it has a kind of three level powerband. ok pulling from idle, pretty hard from 3k .fully on cam about 4K no mid range hole

In the wet it will provide rolling wheelspin in 3rd at 40 Mph. and this one has yet to have the mapped ignition fitted and be really set up well.

very fussy about timing .

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

Hi,
I'd go 1380 if you're going to build something N/A
Mines a Piper 285, 45DCOE mapped ignition, no hole In fact there's 64 curley whirleys @1500RPM



Cheers,
Gavin :)

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I like the 285 piper - it was a nice grind in 1330. The 296 kent was road usable no problems - passed all the emmisions tests - when used with mapped ignition, ticked over at 900 rpm etc. The MED AGSP is a step up fro mthe 296, but you have to be commited to dial in mapped ignition precisely to run one on the road - no holes in teh powerband full throttle from 2000rpm all the way to 8200 and 146 baldwin nanas. Can't comment on the Russell cams as I haven't tried them but don't doubt they produce the goods as well.

JK

If Carling made Mini engines
it would probably be like this one!

i used to have a 1380 with a 296 scatter on twin 1.5s (maniflow inlet)

was a top road motor, only gripe was the 1500 rpm tickover

doing it again id go for a single 1 3/4 as the twins were a pain to set up, but only cos am a lazy git and half cut, twins looks sweet

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Going through one of my boxes of bits yesterday and found a twin 1 1/4" manifold, it's the big flange type so it can be opened up to take twin 1 1/2" carbs. With a bit of flowing it's not a bad manifold, but it's not as good as the tubular maniflow ones mind. Anyway it's yours if you want it.

Thanks very much.

If I require it, I shall let you know:)

I still can't get the tubo idea out my head, and feel that all these lumpy cams may as well have a similar effect to the lag.

Hmmm.

Hi,
The more cc you've got the less cammy it will be. Add mapped ignition and things get a whole lot better too. As you can see from the chart mines got plenty of go from 1500rpm
On the other hand, if you've going to spend money ( ie not got parts lying around) then spend your money building a turbo motor.
You've not got to run 15+ psi from the off.
Cheers,
Gavin :)

VEMs Authorised Installer / Re-seller. K head kits now available!

WB/EGT gauges. Click here for customers write-up

Visit www.doyouneedabrain.co.uk

My Mini build diary

well I am driving a STR-930 cammed 1071 on the road... Thats even more agressive than the 296. and less cc. Its really no big issue.