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ae86drift
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Re: K&N 20VALVE Throttle Pods?

Fri, 03 December 2004 07:51

from the master himself (http://www.billzilla.org/4agmods.htm)

Quote:

170hp - 180hp
Still not any huge differences between the big and small port engines here. Not a lot more work required to get the extra 10hp from the engine now; just slightly bigger cams really. I'd recommend 288 to 304° duration.

180hp - 190hp
Definitely 304° cams, and you'll have to start paying attention to tuning the inlet manifold length, if you haven't done so already. This is also getting to the limit of what a lightly ported small port head can manage.

190hp - 200hp
Getting towards the upper limit of 304° cams, and you'll also need to have the compression up to a good 11:1. 200hp is about the limit for a small port head, no matter what the porting, so from here on the big port is the way to go. Another area that has pretty much reached its limit is the stock valves - Past 200hp you'll be needing the big valve kit. More on that next paragraph.
The standard exhaust manifold has also reached its limit, so 200hp is about as far as you can go with an engine that still retains a large amount of standard parts. It will need to be revved to around 9,000rpm to get 200hp, though if built properly the engine will still be able to be driven on the road.

200hp - 220hp
Past 200hp is where the 4AGE becomes a much more serious engine, and so it requires a much greater attention to detail. It's the point at which you have to start spending a lot more money, for ever decreasing results. But, if you want the extra power then you gotta spend the dollars ...
The reason I've taken the jump from 200hp to 220hp is that there's not a lot of people that make 4AGE's of around this amount of power, hence I don't have a lot of information as such. I've found that past about the 180hp mark, it's the pure racers that do their best to get over 200hp, and so there's a bit of a gap. The other reason I seem to have skimped over the 170hp - 180hp - 190hp - 200hp sections is that once the head work is done, it's really cam changes that make a lot of difference. You get a little bit here and there with compression ratio's, etc, but there's really not a lot of work to be done to get that jump from about 170hp up to around 200hp.
Cams up around the 310° mark, with 0.360"/9.1mm lift are needed. You'll also have to start thinking about getting some 'shim under' buckets, which have the valve clearance adjusting shims as a small 13mm pellet shim, rather than the 25mm dia shim that sits on top of the cam buckets. This is because with cams bigger than the low 300's and roughly 8mm lift, the 'shim over' buckets will occasionally catch the edge of the shim with the top of the lobe of the cam and spit it out the side, thus RAPIDLY destroying the bucket and most likely a fair chunk of head in the next few milliseconds. The shim under kits can be obtained from TRD at hideous expense, or from other racing shops for (merely!) large amounts of money.

The big valve sets are equally as expensive, but again I know of a way that can reduce costs. I have found that the valves from a 7MGTE Supra engine should be identical to the TRD big valve kit, for a fraction of the cost. They are 2mm larger than the 4AGE valves, and should not be fitted if the engine makes less than about 200hp because you will LOSE power. The other problem with the 7MGTE valves is that they're about 2mm shorter than the 4AGE ones, so much thicker shims are needed. With shim-over buckets this is an ugly thing, but I guess it's possible with shim-under type buckets.

There are two crankshafts available for the 4AGE, the 'small' one which has the big end journals of 40mm dia, and the 'big' crank which has 42mm big ends. The big crank weighs about 700grams more than the small crank, (~11kgs Vs ~11.7kgs) and up to about 200hp - 220hp it is stronger, but in practice there is little difference between the two cranks. This changes with more than that amount of power though ...
The factory exhaust manifold, which was good up to about 200hp, now must be replaced with a good set of aftermarket extractors. By good, I mean that they must fulfill a few criteria to make them good rather than merely average -
- The four pipes MUST be equal length, to within less than 1/4"/6mm.
- The four pipes must NOT have any crushed bends in them anywhere at all.
- The four pipes must go into the collector in the same sequence as the firing order of the engine, ie, 1-3-4-2. Many of them simple put the pipes into the collector in any order that's convenient, but these sort make less power than a good set.
- The collector must be around the 60mm dia mark. Many aftermarket extractors have 50mm collectors, and this is not large enough to make big HP

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