4agze turbo should I use 8.9:1 or 8:1? Track car, help pls.

[~SlideWays~]

This is for a fwd club day track car.

Currently it is an early bigport 4agze 8:1 with Link, GT28 and external blah blah. This made 150kw's atw on std injectors and 13psi. (running tvis on a rev switch)

The engine needs a rebuild now, I am thinking maybe I should use the later 8.9:1 pistons to up the compression that way I don't have to max out the turbo (say 18-20psi) to make a good increase from the previous result.

I will obviously use bigger injectors and fuel pump, but what I am wondering is if I am aiming for as close to 200kw's as possible and still being able to take 15min hard runs around a curcuit. Should I use the lower compression pistons with more boost or the higher ones and less boost?

Also looking at swapping to the smallport head as that is what seems to be making the numbers due to flow etc etc. Plus the bonus of the external oil drain, which was causing big problems for me with the bigport head (ie filling catch can).

Any help or even suggestions for what I should look at doing to make the engine more reliable would be great. ie baffled sump, etc.


Cheers

[atmosports]

Flow of the head isn't as much of an issue with a forced induction motor, running the extra oil drain is to my way of thinking a must, I could fill up the top end on my road car motor with spirited driving on the road, you could always just look at the bigport casting & if possible drill/tap a hole for a external drain similar to the smallports, done this heaps of times on other engines.

As for making it more reliable, I'd say fit a decent set of bearings/rings/valve springs etc. Replace the big end bolts with ARP or similar bolts & probably do the same with head bolts/studs. A factory head gasket should be ok, but if you wanted you could probably fit a cometic or similar Multi layer steel gasket, but unless you have had or know of people having problem with stock head gaskets probably cheaper/best to stick with them. A baffled sump is always a good more, especially for a circuit car, sure many people get away without them, but it only takes a split second with oil to do damage. Obviously get the crank/rods/pistons etc crack tested & if not already done you could get the rods shot peened. Probably wouldn't hurt whilst it's all apart to balance the rods/pistons etc & then get the rotating assembly including the clutch/flywheel etc balanced as well. Apart from that I'd just say make sure everything is square & ruuning true & all the clearances are within tolerance etc. Probably pay to fit a new oil pump/water etc if you don't know the history of the old ones

I would personally say go for the higher compression pistons & run slightly lower boost if needed. This should give better off-boost driveability amongst other things. I've generally done this for road/rally use as it seems to produce a nicer car to drive than lower compression, they just seem to pull a lot smoother, more linear power delivery I guess. If you were building a high revving, high boost all out circuit/drag car & chasing he big power then I'd say drop the compression back.

[flygt4]

high compression ftw. run a slightly larger turbo at a lower boost to make more power with a better spread if you're building it from scratch you may as well use proper aftermarket forgies, rather than the ae101 gze items , with a slightly higher CR , maybe 9:1 with a tdo5 turbo or a t3 hybrid jobbie. well thats what id do then you're set to run a larger turbo at a later date if you decide you're not happy with it.

did you find out what happened to your last engine in the end?

[CAMB01]

I was talking with your bro Gav and i might have figured out what happened, u wouldve been getting alot of blowby and pressurising the crankcase, not allowing the oil flow back from the turbo. So it wouldve blown the seals out in the turbo.

Atmosports has suggested what ive done to my motor. Would be very reliable as long as its tuned right.

[Mr Revhead]

yeah as atmosport.

stock gasket is fine, TRD for a little more compression.
you need to be making some SERIOUS mumbo before you exceed the capabilities of stock 4agze pistons.

[nite b]

8.9-1 & smallport head, you wont look back. Low comp is cool but always end up feeling 'laggy', even with conservative turbo. Power will be bit more linear and well suited to what you require. 18psi on a good tune & medium size turbo etc, will net you easy reliable 200kw@wheels. Nice accomplishable goal, sounds good!

[Dell'Orto]

9:1 with a 20v head and a GT28RS. Will be one mofo punchy car

[flygt4]

even tho my car has a silvertop head , i still reckon its pretty much just for wank value on a FI setup only real advantage seems to be it happily revs up to 8500. the quad throttles just make themselves a nuisance unless you're on full throttle all the time , as in drag racing.

simplicity is your friend

[crnkin]

8.9-1 & smallport head, you wont look back. Low comp is cool but always end up feeling 'laggy', even with conservative turbo. Power will be bit more linear and well suited to what you require. 18psi on a good tune & medium size turbo etc, will net you easy reliable 200kw@wheels. Nice accomplishable goal, sounds good!

what brendan said. Basically a late model 4agze map version, rebuilt and balanced is the best posible engine combo per dollar than almost any other engine (4k pow pow power)

[~SlideWays~]

Thanks everyone, good info there. Hopefully all goes to plan in getting a smallport head and 8.9 pistons, etc.

Can anyone point me in the right direction for a fwd non tvis intake manifold and fuel rail? I do have one but it has been cut n shut for my rwd one (yet to be turbo'd...if I keep it).

[IH8TEC]

just get a tvis one and dont use the tvis plate with the butterflies,

[~SlideWays~]

just get a tvis one and dont use the tvis plate with the butterflies,

Would the ports line up with the twin hole jobbies though? Don't have the head yet (lol I could pull the one in ae86 apart for measurements but can't be arsed )

I would have thought that there would be a big over lap.

[Mr Revhead]

no the ports dont match up.

make one you pussy

[~SlideWays~]

no the ports dont match up.

make one you pussy

Didn't think they would. I've found one though so now hopefully I get the head too

Pfft why make one when mr toyota made a good one already?

[IH8TEC]

well not sure if they make smallport tvis manifolds.

the manifold on my car is a bluetop tvis one without the tvis plate in there, so no butterflies, yes it has twin holes for each inlet on the manifold and the head has 1 each cyl. but they line up.

could put money on it that a smallport tvis one would line up with a smallport head.

[~SlideWays~]

well not sure if they make smallport tvis manifolds.

the manifold on my car is a bluetop tvis one without the tvis plate in there, so no butterflies, yes it has twin holes for each inlet on the manifold and the head has 1 each cyl. but they line up.

could put money on it that a smallport tvis one would line up with a smallport head.

Never was a tvis smallport dude. Doesn't matter, problem solved anyway.

[Mr Revhead]

for the record the intake ports on the TVIS head are much bigger than the non TVIS one.
hence the names bigport and smallport

[Bazda]

I like low compression and lots of boost, i dont generally worry about lag too much. My cars lag now feels crap all and thats on 7.8:1 compression.

if ur only gona limit ur boost to 18psi then prob go with 8.9:1 but if u want more boost cos u want more pow pow then go with lower compression.

[matt dunn]

I also say go the higher compression route.

My current engine is low at less than 8:1, and I built an experimental engine that used the 8.9:1 GZE pistons, and it was much more responsive and nicer to drive than the lower one.

Not too sure on outright power yet as although I had it up to 20psi, It will need a good tune on a dyno before I run full advance into it,
But I dont see why it would not make as much or more power than the lower comp one.

matt

[Crucible]

But I dont see why it would not make as much or more power than the lower comp one.

I would agree with that also

Because with either setup wheather it be a hi-comp low boost or low comp with higher boost the " final" compression ratio ( static + boost pressure) is what limits how much power youll make anyway before the fuel will self ignite - detonate....

So I would say hi - comp engine would be a better choice IMO as it has the advantage of better off boost drivability.

also remember just because you have a higher static compression ratio its the cam profile that will give you an "actual" compression ratio

cause if you have a static comp of say 9.0:1 and you have a cam with poor lift and duration you may only have an "actual" comp ratio of a lot less.

just my 2 cents