Stock 4AGE Smallport Turbo Choice please

[maj]

30% drivetrain for me since I've lived in AWD land for so long

TBH for a silvertop a low boosted turbo response wise should work well if you factor in VVT and E85. 16V I would still agree with but maybe not as strongly.

An SC would be very cool but I think you will struggle to get 160kW without spinning it too fast and feeding a 20v too much boost. as Vito said, keep it simple stupid.

[JustenGT8]

Rotax would work well I reckon and easy to package....I'm stuffed for space so anything extra hanging off the engine will be tight. I believe there's even a kit, not that I would use it but some good ideas to poach

[trdee]

I assume you mean Rotrex, or do you want a 2 stroke supercharger? From what I have seen of how they perform I am not a fan. Linear boost response makes for nonlinear torque/power. To get decent boost down low without retarded boost up high you would either need a fancy CVT style gear set up or you would need to overdrive it heaps and have a wastegate style bypass system to bleed off excess boost as the revs rise. Lots of headfuck/complication/weight/points of failure/etc

The other option as mentioned before would be an n/a 9A. E85, comp and cams will get you to your power target.

[JustenGT8]

Lol iPad auto spell. Yeah centrifugal are the worse of both worlds (SC and turbo), but they are the best of this style of SC. I'd love a twinscrew but hard to come by at the right price.

[xero]

I'd be happy with a responsive 160rwkw...and as good as FI can be it is still hard to beat n/a for throttle response....imagine the noise!!

Mild turbo 4A, angry N/A 9A or blacktop beams. There are plenty of ways to go about it

Also I don't need to imagine the noise https://www.youtube.com/watch?v=EOaWgek7Owc

i know im a bit late to the party but RE angry N/A engines:
my angry small port makes 120rwkw
a good mates unopened beams with ITBs and good tune made 140rwkw
and another mate has a built beams for sale that made ~160rwkw for $9k

Hi comp, RPMs and short gearing can make up for lack of FI torque. oh and the noise is great. all this depends on what its going into and packaging requirements etc.

still would love me a turbo 4A ae86 some day...

[DX20VT]

The arp studs only seem to be an issue with the 20v head. Quite a few people reporting head lift with arp studs on a 20v head at relatively low boost levels where the stock bolts had no issues.

Are you saying that the stock bolts do not suffer from that.

I used to run Toyota headstuds on my 4A 20V turbo motor, but they were $1.40 each so $14 for a set.
2 years later they are almost the same price as an ARP set, about $200,
so when I went 7A turbo we used ARP headstuds,

and at 20 psi now it pushes water out the overflow which the tuner says is a sign of the head lifting as they have seen it before on 4A turbo's.

Maybe next time it is apart we might put new Toyota studs back into it?
Thoughts?

[trdee]

apparently they do not, although I'm sure they would have a limit too... IIRC bazda was running up to 26psi on OEM bolts without issue, whereas fandio was getting head lift with the ARP studs at as little as 22psi. both are using BT20V heads

my new motor is using oversized ARP headstuds as I want to run 30+PSI and I am not entirely sure the stock bolts will live with that

[andrew_mx83]

Does anybody hardness test 4a heads? It is also possible that rather than studs stretching, the aluminium under the washers is deforming causing the stud to lose tension
Arp make insert washers which are an interference fit in the stud hole that prevent the material from collapsing. Some info/debate about them here: http://www.supraforums.com/forum/arc...t-683040.html?

Ive put them in the head im building for my new motor, but i also have a head here which is soft and known to lift even with studs so i may fit the insert washers and put it on an engine at some stage just as an experiment.

[trdee]

Not really unless it has been in a BHG/overheating situation. Wouldn't that problem affect the stock bolts too though?

[DX20VT]

apparently they do not, although I'm sure they would have a limit too... IIRC bazda was running up to 26psi on OEM bolts without issue, whereas fandio was getting head lift with the ARP studs at as little as 22psi. both are using BT20V heads

my new motor is using oversized ARP headstuds as I want to run 30+PSI and I am not entirely sure the stock bolts will live with that

I don't think boost is a good thing to compare it against as I made more HP at 21psi than Bazda had at 28psi,
but I was on race gas and he was on pump gas.

The guys that tune my car had a 4A that they fitted 10 or 12mm mitsi ARP headstuds too i think to overcome the problem,
but mine only just starts to lift at the peak of the hp I want to make so I don't want to get carried away.

[trdee]

True, the real measure is combustion cylinder pressure i guess... although generally most 4As seem to make relatively similar power levels on similar boost so normally it's an easy yardstick to use. Race fuel changes that of course

Yeah I believe the studs I have are 4G63 derived. Don't remember tbh lol

[andrew_mx83]

Not really unless it has been in a BHG/overheating situation. Wouldn't that problem affect the stock bolts too though?

yeah, probably, but what i was getting at is *perhaps* the fastners were not the problem in the examples posted and one head was more or less hard than the other. i doubt the arp studs would stretch before OEM ones...

either way $100 worth of insert washers and probably about the same in machining to fit them may be good insurance if you're running retarded amounts of boost.

[rick q]

OK - I'm just chasing a little more advice from those who know .......

You may recall I'm stitching together a little budget turbo upgrade for my clubbie - I'm looking for nice linear response rather than peak power as the clubbie sees mostly track time. I'm now using a smallport block, 20V head and TD04 with W2A intercooler.

The manifold's made, lots of parts have been sourced and it's all well under way. I was looking to start at around 9.5:1 compression ratio which looks to fit with my goals of better response.

Late model GZE pistons in a 20V head with a standard 1.2mm Head gasket will give me 9.4:1 - so a little bit more once the block and head have received a tidy up. Trouble is - I can't find any standard bore late model pistons.

I've cc'd the dish in the early model 8:1 GZE pistons I found at 13.2cc - quite a bit more than the 10.4 the www tells me. With these, an 0.8mm head gasket and .1mm off both the deck and the head, I'll get around 8.7:1.

That strikes me as too low for crisp response on the track. Can anyone here tell me if I go down this route whether I'll just end up with a doughy unresponsive lump- or better yet, tell me where I can get some used 8.9:1 GZE pistons for beer money????

[JustenGT8]

8.7 will be fine at the track as you are on boost (or at least at boostable revs) all the time. Where a higher comp mostly helps is with off boost performance, or top end with a small turbo that is running out of flow (eg WRC scenario). Turbo sizing will effect boost response far more than a change in comp ratio.

That's not to say a higher comp wouldn't be a little crisper, but as you are on a budget and have to compromise those pistons will be fine. A bit of boost headroom too of course if you want to wind it up a little

[trdee]

basically what he said. on a TD04 with a 20v head you will be on boost pretty much all the time, so you won't notice the lower comp.