4AGTE questions

[Bagpuss]

We'll see with the axle I guess, failing that I know weir do a spool gear conversion kit that will definitely take the power. If I went for a full engine swap it would be the v8 swap just for the fact that it's a more reliable power than a tuned turbocharged engine (and it'll sound infinitely better!)

[gazt]

I have a 4AGTE motor. Not got the car on the road yet so haven't driven it! Mine runs megasquirt ECU, VVTi COPS (no distributor) with T25 turbo on eBay tubular manifold. Everything except the MS was bought second hand and has been completed relatively cheaply.

I'm not expecting it to last forever so am building a 7AGTE motor with forged pistons/rods. AGZE pistons are still available at about £70 each plus £110 for ring set.

[jab]

The above post was by me. Didn't realise I wasn't logged in lol.

[Tony N]

It's worth bearing in mind that you need to use GZE pistons, rods, and crank together as the small and big ends are 2mm larger.

[Bagpuss]

So if I was to go down this route buying a GZE long block is definitely the way forwards. I guess the next question is how much boost can the stock long block take before needing uprated head studs and gaskets/stronger internals? If I ran the t28 turbo I would aim for around 17-18psi of boost I think.

[Tony N]

According to the discussions on the old turbo board on club4ag they're good for anything up to 2 bar boost with the right turbo and fuelling.

A T28 is good for around 1 bar, much past that and you're running off the efficiency curve and they just generate heat. Also the thrust bearing needs to be upgraded to a 360deg type past 1 bar else reliability starts becoming an issue.

I'd say you should be able to push 250 to 300hp from a 4A-GZE with a T28 at 1bar depending on cams etc.

[Bagpuss]

2 bar!? That's much more than I'd hope to run, this is good news! It would certainly make setting it up cheaper than swapping the V8 in. Bit disappointing on the T28 front mind you, I had assumed they would be good for up to 18psi, I'd run a td05-16g instead but the convenience of premade manifolds makes the T28 much easier to set up.

[Tony N]

You'll run into problems with the gearbox and axle far before a GZE lets go!

The half shafts are the weak link in the axle so fitting a spool won't help. Weir did have a large shaft conversion for use with a spool but I think when Sweeps enquired it wasn't available. However if you run sensible tyres you're likely to be OK on the shaft front, I think the real problems come in the forests when impacts from jumps etc. cause them to break.

What's the thinking behind 18psi? A T28 at 1bar will make for a very entertaining 86 and is definitely pushing past the limits of a T50. If you want more you could start looking at the different flavours of GT28R available but you'd at least need to upgrade from the T50 first I'd say.

[Bagpuss]

Like I say the shafts in my axle are uprated to match the cusco 2way diff already, they're one thickness all the way along rather than tapered down at the geared end so hopefully they'll be fine!

The gearbox may be an issue, but that's not a major worry for now. The idea behind the 18psi figure was to achieve around 250-300hp, as otherwise it'd be more effective for me to stick with the v8 conversion and take the 260bhp it offers.

[Tony N]

Ah yes, I missed the Cusco shafts, I can't see them giving you any problems with a 4A-GTE. If you do go ahead and decide to change the gearbox, I'm half way through converting to a W58 Supra box and am having an adapter plate to fit the T50 bell housing to the W58. Let me know if you're interested.