GZE power - what is it capable of with the charger

[takai]

Yeah, esp the AE101 which are quite heavy.

My GZE was pulling 113fwkw with 10psi and the bigport 240* cams, the cams dont really give much in the bottom end, but if anything take it away there, but that is masked by the charger. But they do give a bit in the top end where the charger starts to run out of puff.
As for torque that setup ran at about 350Nm of torque and tapered off to 280 or so.

I dont have the car or documentation anymore so i cant give exact figures.

[myne]

If that's 280nm at 7000rpm, you're talking about 205kw - hardly a bad effort.

*edit* those numbers have to be wrong. For it to make a mere 115kw, it couldnt make 350nm any later than ~3000rpm - at which point it'd be making 110kw. It'd have to drop to 280nm BEFORE 4000rpm or it'd go over 120kw. You'd end up with a very peaky power band that'd be almost impossible to use.

[takai]

Yeah, as i said i dont have the graphs on me here as I gave them to the new owner along with the documentation. But it tapered off relatively slowly and then flatlined at some point. Ill see if i can dig up a scan of it, but not hopeful.

[dynomatt]

On the topic of cams, I'd caution against increasing duration...more lift is always good, but increasing the duration on a boosted car (turbo/supercharger) may have problems. It's due to inlet flow restrictions etc...

What's the factory duration of the 4AGZE?

I've just been through the process of rebuilding my 3SGTE, we improved the flow on the inlet substantially, and went for pretty wild cams...they had 11mm lift I think and about a 270 advertised duration. Unfortunately, it made bugger all power...and the duration (probably more likely the overlap) was probably the cause...went back to about a 245 cam and suddenly made heaps more power...

We think the theory is that in an NA engine, you are relying on atmospheric pressure to fill the cylinders, so extending the duration compensates at high revs. Whereas the turbo/supercharger is doing that work for you...

Dunno if this helps your evaluation, just some experience to think about.

Matt

[myne]

Actually, on NA engines the overlap, in combination with the inertia of the incoming and outgoing air, actually allows incoming air to be slightly sucked in by the outgoing air.

Ideally the inlet valve is supposed to open just as the pressure drops slightly inside the chamber and the exhaust valve is supposed to close *just* before the fresh air gets to it.
Also, with the longer inlet duration, the valve remains open AFTER BDC allowing the inertia of the air to carry it in. The valve is supposed to close just as the flow starts to reverse.
similar with exhaust valve opening. A slightly earlier opening will start the flow just before the piston hits BDC. The maximum potential for power has already been used, the pressure of the still expanding combustion charge will slow the piston down if it's left too late. Best to start the outward flow before the piston comes back. It reduces pumping losses.

Problem is, engines cover a wide range of flow over their rev range. So at low rpm, high duration cams can allow exhaust to start exiting the inlet, which disrupts the inlet flow, contaminates the charge and loses power. At the other end of the stroke, the still open valve can allow inlet gasses to exit, resulting in not only a contaminated charge, but also LESS of it.
On boosted engines, it can allow the inlet mixture to exit through the exhaust without being used, though the extra pressure of the gas can prevent reversal.

That's why cams have an effective range. Because at different RPM, different cam timings and lifts work more efficiently. This is why Honda's VTEC, Toyota's VVTi-L etc were invented. Honda's allows 2 distinct cam profiles to be used, with the engine switching at ~5000rpm. A lower cam that runs out of puff at ~5500rpm and a higher cam that is useless till 5000 rpm.

Beyond that, eventually there may be a way to electrically or hydraulically lift valves.
That would allow for infinitely variable timing and lift, which would be the absolute BEST way to make power at ALL RPM.

[dynomatt]

Sorry..this is going slightly off topic.

Is what we experienced validated by your comments? I'm not technically minded enough to fully understand the theory.

What effect does having a boosted engine (ie positive pressure) have on cam selection different to NA?

Tighe did my cams and even he was struggling to fully appreciate what's going on.

For info, Lancer Evo's utilise a cam duration that's about 190 degrees...VERY short duration.

But I agree that every engine is different...I guess I'm lucky that I have a limited rev range within which to operate...so the best cams will work within that range.

Matt

[myne]

The problem would have probably been in the overlap.

Inlet opens while exhaust is still open -before top dead centre. The exhaust pressure, because it's boosted may initially be greater or equal to the pressue of the incoming air. This will stall the inlet flow and possibly contaminate it with exhaust gas.
The exhaust valve then stays open after top dead centre which can allow inlet gasses to escape directly through the exhaust before they get a chance to be used.

Most 'turbo' cams have very little overlap.

Have a look at this http://auto.howstuffworks.com/camshaft1.htm
It's not very deep, but the concept is there.

[Hen]

There was an interesting thread on the old forum, posted I think by Nick.Parker about his experiences setting up some bigger cams on a 4AGZE. He had a hard time getting it right and the way I remember it the best result was using zero overlap. Have a search for it though.

Hen

[nick.parker]

Hi,

I still haven't dyno'd my SC14 AW11 MR2, will do it soon though, since I have
even more things I want to do to it. I have done just about everything
you can outside the motor. Big throttle, big piping, modded bigport TVIS inlet
manifold, big pulley, SC14 pumping 18psi, water to air intercooler..still got a
2.5" exhaust and extractors to go though.

I currently use Wade 267° camshafts, and it you love the instant low end
torque then don't get these. I had the 240's before and the car was balistic
at low RPM, like really really impressive, probably like a _very_ strong V8.
Made the rear squat right down and front very light on hard take off basically
from off idle. But that went when the 267°s went on. However the car is very
strong from 3-6K now and doen't feel so short of breath at higher revs now.
I had to try more than 10 different cam timing settings by SOP testing :-) to
find what I liked the best.

So overall I like it more, and its still pretty good on the low end.

At a recent Autokhana thing the instructor thought my car was in the 200-250hp
range and was so impressed by the 'package' he actually wanted to buy it off me!

Probably the higher comp 8.9 :1 motor would give me a good gain and I intend to put
a smaller inlet cam on to get a little more low end back, in exchange for a small decrease at higher rpm which could probably be gotten back with a bit of head porting or something.

Regards, Nick

PS: You can see some in car video on :
http://www.e-wire.net.au/~nrparker/M...new_engine.htm

[feral4mr2]

What's the factory duration of the 4AGZE?

232 degrees.

[Hen]

232 for the smallport version.
240 for bigport version.

Cams are identical to the 4AGE of the same year/month (As is everything inside the block/head bar the pistons and rings). There is plenty of info out there about such things.

Hen

[Nim]

On the B18C2 (my engine) the cam switches at about 5800 (although that depends on temperature and stuff like that, sometimes it switches a bit earlier). At 5800, the first cam is just starting to run outta puff. I imagine the redline on the first cam would be about 7000 or so. But the second cam kicks it up to 8150 (bit of a strange redline I know).

[feral4mr2]

232 for the smallport version.
240 for bigport version.

Cams are identical to the 4AGE of the same year/month (As is everything inside the block/head bar the pistons and rings). There is plenty of info out there about such things.

Hen

the only 4age i thought thats spose to have the 240 duration 7.56 lift cams is the old 3 rib bogport 4age. my 7 rib bigport 4age and gze didnt have these cams, they have the 7.1mm lift 232 durantion cams... .

[nick.parker]

Hi,
with regard to CAMs this is fact.

I measured my smallport, high compression 4AGZE's cam lift to be EXACTLY 7.1mm implying the 232 degree camshaft.
I measured my AW11 bigport 4AGZE cams at just under 7.56mm lift (slighty worn?) camshafts, so I assume they are 240's.

I assume that 4AGZE AW11s (jap import - all are I think) have 240 degree cams.

Regards, Nick

[takai]

Im pretty sure that a lot of the AW11 GZEs (AFM) had 240* cams.
Just a bit of a warning, the cams can lean out on the bottom end with the MAP sensored high comp GZEs.