15 replies to this topic

[timothy]

Hi, I'm planning my engine build and am looking to run about 12psi of boost with an intercooler on a 1275 a series. Is it neccessary to run s/c drop gears? What level of boost will the standard helical drop gears withstand? Also roughly what power and torque will I be expecting with this, I'm guessing between 140-150 bhp in line with turbo-mini.co.uk.

Cheers

[Ethel]

It's not the gears but the bearings they run in that fail. Have a look on Turbominis site people have tried all sorts of fixes. You don't get the 'days of thunder' sound effects with helicals though!

Well actually it is the thrusts (they're still bearings aren't they?). Helicals act like a screw thread and create a side load that can cause the thrusts to turn and eat in to the casing - torque is the culprit. You can join my campaign to get someone to produce a taper roller bearing conversion if you like.

Edited by Ethel, 29 April 2008 - 02:22 PM.

[Guess-Works.com]

The bearings survive fairly well... it's the fact the idler chews it's way through the transfer case which is the problem

But anything over 120 I would suggest SC drops...and even before considering SC drops, you'll be needing at least an X-Pin diff...

Edited by GuessWorks.co.uk, 29 April 2008 - 01:41 PM.

[t@z]

s/c drops are very very noisey all is love and war and dam fun but crikey noisey lol

[Turbo Phil]

If your looking for 140-150hp & the associated increase in torque then your going to need them. They are a weak link in the transmission, after the diff. You may get away with a properly rebuilt helical box, as many do, but it could be borderline.

[timothy]

Ok cheers, I'm trying to strike the delicate balance of power/budget so maybe I should keep the boost down to around 10psi and keep helical drops saving a £200. Also I'm not entirely sure about the good old s/c whine, it sounds great when your outside the mini or when your bombing around a track i'm sure but on a long journey and for a daily driver I imagine it'd soon get a little irritating.

Cheers.

[Turbo Nick]

a full length dash and soundproofing will cut the noise a hell of a lot inside the car, i used to run mine with no soundproofing/carpets etc in my daily drive and it was fine. when i hit the motorways i just used to stick my ear defenders on.

I'd say spend your money on a 4 pin diff from minispares first then drops second reliabilty wise.

[davegreory42]

sorry to hijack (and ask a stupid question) but i'm building a 1380 at the moment and was wondering about gearbox options, the thing is i know precisely nothing about gearboxes, so, whats the difference between SC drop gears and a full SC box?

[Pie]

sorry to hijack (and ask a stupid question) but i'm building a 1380 at the moment and was wondering about gearbox options, the thing is i know precisely nothing about gearboxes, so, whats the difference between SC drop gears and a full SC box?

SC Drops - Only the drop gears/ Transfer gears are s/c

SC box - Every gear inside the box (with exception of CWP) is SC.

Basically to get the best, you need a straight cut gearbox with straight cut drop gears, complete with a 4pin/x-pin/cross-pin (call it what you like) diff and a central oil pick-up.

[Guess-Works.com]

All depends what you intend on using the car for.... if it's an everyday driver and you do some mileage, then I would suggest sticking with Helical gears and drops...

As Bud' has said, noise at speed can be a bit of an issue with SC's, so ear defenders are an optional extra.

[samwell]

bearing in mind it won't just be reliability you gain with SC drops, there is an associated power gain (reduce in power loss witnessed as an increase in power at the wheels) which is not insignificant.

Sam

[JetBLICK]

As Bud' has said, noise at speed can be a bit of an issue with SC's, so ear defenders are an optional extra.

I tend to find they get quiter... as you get faster the noise becomes more high pitched, by the time your at motorway speeds i think its so high pitched its sub-sonic or somethin, because you can hardly hear 'em

[Guess-Works.com]

As Bud' has said, noise at speed can be a bit of an issue with SC's, so ear defenders are an optional extra.

I tend to find they get quiter... as you get faster the noise becomes more high pitched, by the time your at motorway speeds i think its so high pitched its sub-sonic or somethin, because you can hardly hear 'em

Nah... that just the blood in your ears masking the volume....

[Ethel]

As Bud' has said, noise at speed can be a bit of an issue with SC's, so ear defenders are an optional extra.

I tend to find they get quiter... as you get faster the noise becomes more high pitched, by the time your at motorway speeds i think its so high pitched its sub-sonic or somethin, because you can hardly hear 'em

Nah... that just the blood in your ears masking the volume....

Visions of a go faster Mini driver, blood trickling down their neck, wondering why all the dogs howl as he passes them. The ear defenders aren't really a joke, even a relatively mild dose of loud noise will damage your hearing if it goes on long enough.

Any thoughts on improving the reliability of Helical drops? Minimum clearances seems sensible. What about extra oil feeds etc?

[Udo]

Any thoughts on improving the reliability of Helical drops? Minimum clearances seems sensible. What about extra oil feeds etc?

Try here, some very nice machine work

http://www.minifreun...oilpressure.htm