1425 turbo
Turbo Mini Forums

Hi, im new to the site and am currently building up a mini. I already have the turbo box welded in and have all the relavant bits. But im wanting advise on the engine. I was thinking about a 1425 turbo, because of the cc this wud give very good low down torque and the turbo providing good mid and high range power. Is this possible? as i have never seen one before. It sounds a good engine but wud it work? Any help is greatly appreciated

jamob

Hi Jamod,
you have to know that the overbored and I think so overstroked, are a not great in the minds of turbo lovers,
this said , a lot of turbos are built to give the last hps that can't be gived with an n/a set up, and that a turboengine can be seen from a different angle ( high torque),
I think that a 1430 can be reliable or enoughly with a low boost system, ie , a 1430 , a st 3 head an intercooler and maximum 7 psi of boost, it can be reliable only if it is a roady engine, ( an engine which will be used at max throttle and high revs for a low time and very rarely), my roady trubo and daily mini was out of boost and at part trhottle the most of the time abusing of the power available at very short time and rarely, when the driving condition were sure, this can allow a lighter boost, and more cc.
having discuted how a 1430 would be "reliable "on a roady set up, the difference of using a 1430 at part throttle and a 1380 or a 1310 is so small and the price so different ( set of S rods,pistons, work on the head and pistons to achieve a low c/r (about 9/1)
that I wouldn't build and try to turboing a 1430 or a 1380 if I didn't have a 1380 or 1430 to blow before, as I will extract more power from a 1300 and more boost at a lighter price.
I hope that you'll understand that I didn't want to discuss with the reliability( as I'm sure it can be) of such a project if it is raisonnable in term of boost, but more in discussing the interest of making a pricey 1430 and having to stay with a low boost as you can have more hp's and more torque with less money and higher boost.
fab

Thanks for the advice fab,
In that case just a few more questions though! What is a good spec for a road engine that would be used daily? I want an engine that has bags of power but it also needs to be reliable.

Which would be better in an ideal world if the money side wasn't a factor - a smaller cc engine with high boost or a bigger engine with low boost, from a reliability and power point of view.

What are the weak points in the chain as regards to the reliability, the box?

Where do i start!?

jamob

You don't need cc's when you have boost!

1 or 2 psi will make more torque than overboring from 1275 to 1380...

Its all to do with Volumetic Efficiency, of which the A-series suffers due to an odd 5 port head design. Even a massivly modifided head will strugle to flow enough air for a 1425, just down to the volumes of air required. A turbo solves this by puching your VE through the roof! A race head might get to 110-130% VE but a turbo can see more than 200%.

If you want low torque then you can run a smaller turbo, but thats at the expense of top end power. But how much power do you want in a mini, even with a std engine they are hardly slow!!

Reliability is all down to how the engine is built and how it is maintained! The gearbox is always going to be the weakest point, but there are things you can do to help it. Other reliablilty issues are headgaskets (which get less rebailable on big over bores anyway).

Alex

AlexF