27 replies to this topic

[Dog]

But if I was using as a everyday car, then I would use the simlur set up but might think about putting the ECU in, to save torque hitting the box too early

Eh???

Right, as you know, if you left a std metty T3 turbo, it will be a constant 4psi, this on its own isn't that bad.

But the orgianl metty turbo, had an ECU, this ECU made the turbo, boost 7psi once it hit 3500rpm.

As you know a lower boost means less torque, so less torque in town is ideal, as it won't eat the teeth off the gears, or ruin any other part of the box.


The ECu is a good way to look after a turbo engine if using everyday.

[Jammy]

I see, I learn something new everyday! And its not always about yellow snow...

[pikey7]

As you know a lower boost means less torque, so less torque in town is ideal, as it won't eat the teeth off the gears, or ruin any other part of the box.

Actually I didn't know that. (probably 'because it's wrong)

Lower boost doesn't mean less torque, it usually means a flatter torque curve (thus reducing gearstripping abilities) but it depends on the turbo trim too......

You can still have a low boost turbo with a very steep torques curve which will eat gearboxes.

[Dog]

As you know a lower boost means less torque, so less torque in town is ideal, as it won't eat the teeth off the gears, or ruin any other part of the box.

Actually I didn't know that. (probably 'because it's wrong)

Lower boost doesn't mean less torque, it usually means a flatter torque curve (thus reducing gearstripping abilities) but it depends on the turbo trim too......

You can still have a low boost turbo with a very steep torques curve which will eat gearboxes.

Ok so it might not be 100.1% accurate, but you get the jist of what the ECU does

[pikey7]

Do you know what the ECU does? As far as I understand the Metty turbo system is bascially controlled by the actuator which is Vacuum actuated. The carb obviously isn't controlled by the ECU, so all I can thinkis that it does something to control (in some way) the advance curves, which I can't see having a lot of influence on the boost produced!?

[Turbo Phil]

The actuator is actually opened by boost, not vaccum. The actuator holds the wastegate shut by means of a preloaded spring inside it's body, which in turn sits against a diaphragm. Now the actuator is connected to the compressor housing of the Turbo, so when the pressure inside the compressor housing reaches a preset level {in the case of the Metro Turbo 4psi} the actuator opens the wastegate in the Turbo allowing some of the exhaust gases to bypass the exhaust turbine, thus limiting boost. Obviously once the boost drops again the actuator closes the wastegate.
As for the ECU, this in no way controls the ignition, unlike on modern cars. The sole purpose of the ECU is to control the boost via an electronic solenoid. Limiting boost to 4psi below 4,500 and to 7psi thereafter.

This is all covered in the "sticky" at the top of the Turbo section.

Phil.

[pikey7]

Sorry, Vacuum was a bad way of putting it. I meant "manifold pressure".

Anyhow, an interesting way of increasing gearbox life! Thanks for the sticky.

Can the ECUs be "played with" to change the levels at all?

[Turbo Nick]

*IF* you could play with the ECU all you could really do is change the point at which the solenoid valve is opened, to get any more boost you'd have to fit a bleed valve inbetween the compressor housing and the solenoid to get it above 7psi.

[AlexM]

You might be able to smooth out the action of the solenoid valve if it is possible to alter the ECU, im sure there must be some benefit to this.

[josh_tacon]

bttt!!lol

will a T2 off a bluebird or a silvia fit ok?
i think im going to have a go at modifying the standerd turbo manifold.
will it perform any differnt than the R5 turbo unit?

cheers
josh

[Turbo Phil]

Both those cars came fitted with the slightly larger T25 iirc. They're a four bolt mounting, so adapting it to the Metty manifold will be the same as fitting the R5 unit.
Performance wise they're supposed to be reasonably well matched, though you'll not see boost as early as the R5 unit, this certainly seems to be almost spot on.

Phil.

[josh_tacon]

but would a t25 mean it would come on boost a bit later than the t2 but earliyer than the t3?
will it be on boost for longer than the t2 but not as long as the t3?
or is it not as simply as i think?
has anyone got any ideas of the boost up times for the t2, t25 and the t3 turbos?
are each type the same or does it depend what car its from etc?

cheers
josh

[Turbo Phil]

It depends what car the Turbo's from. Not all T2's, 25's & 3's are the same, this just refers to the "group" they come from. Each Turbo is tailored to it's application by altering the AR ratio of the compressor and exhaust housings. A smaller exhaust housing allowing faster spool up at the expense of flow higher up the rev range.

Phil.

Edited by Turbo Phil, 05 April 2006 - 10:26 PM.