La400

another note round port exhaust

RRocket

I have experience with DOHC Ford 4.6's. With a COMPLETE head job (valves, valve job, port work, etc.) 40HP is not too difficult through the stock manifolds. Once you throw in a set of cams AND headers, you're talking close to 100HP. DOHC V8 engines REALLY come alive when you do stuff like this to them. You might also try to extrude hone the intake just for something to do, though I think doing that will definitely require different engine management...

Vette Boy

Nothing else, just take a 4.6L DOHC V-8, port the heads there's increase the power by 40HP? No cam, no headers, no CIA intake, nothing...a stock Stang (300HP stock?).

Hollywood

But think of the craftsmanship between ford and Lexus. Im sure that Lexus probly payed more attention production/design wise.

whats size are the gs430 injectors over the gs400?

JBrady

Interesting specs. The factory listing that I have is slightly different at:
230 degrees intake duration (-14 ~36 BTDC, 64 ~14 ABDC)
229 degrees exhaust duration (41 BBDC, 3 ATDC)

What the intake numbers mean is that the cam has a range of 36 degrees before TDC to 64 degrees after BDC. Total timing is 230 degrees so if you are fully advanced with openning happening at 36 BTDC your closing happens at 14 ABDC. If you are fully retarded at 14 degrees AFTER TDC your closing happens at 64 ABDC.

Something to remember is that this engine does not have simply 2 positions. The timing advances and retards throughout the RPM range depending on load. Interestingly enough the cam timing for light load and max load is more or less the same. Max advance happens at idle, starting and low temps yeilding absolutely no overlap... while maximum retard occurs at medium RPMs with medium to heavy load.

JBrady

Here is from the Lexus tech pages. This shows the graph for the 5 relative timing ranges.

La400

Thanks jbrady,
I needed that info. From what I see and based upon the flow of these ported heads, I am beginning to suspect that I will need a little more cam and fuel to make full use of them. Ported them may of been a overkill. Then again the total system may just love the increased flow. Have them on by the 14th. Will be interesting.

JBrady

The black ring represents the fixed exhaust timing while the white ring shows the variable intake timing. Here are the first 3 conditions.

JBrady

The other 4 ranges listed.

La400

That is great info. Thanks a lot. I got both factory manuals, maybe I should look towards their information more, if this where you got it from.

La400

Hey, that is super info and very helpful for understanding what is going on.
Thanks again.

Best,

Hollywood

What is the timing range that the ECU has control of ie: to combat knock detection to 94 octane gas. How many maps are on the ecu? 2?

JBrady

The timing I am referring to is valve timing. The ECU also controls ignition timing but that is not something I have ready data on.

Hollywood

I know, but since we are on the subject I thought I'd bring it up.

Does the v8 have a knock sensor even?.

SCV8

Nice pictures, thanks for sharing those.

I had the rare opportunity to examine some IRL heads today, all I can say is "wow".
I need to get a spare set of heads and start a welding project I think. Things were smaller than would be expected, about the same size as our engines actually, just that the geometry was WAY different.

I've looked at some Ford 4.6 info for inspiration, looks like they do have alot of potential, especially with their added displacement.

The ECU has a couple basic modes, a default, or "open loop"mode for startup, and "closed loop", which is a dynamic, using all the sensors mode. In open loop, the lower rpm ranges are controlled by the sensors, and at open throttle things are a bit more pre set. What's nice about that is that you can tune for WOT, and the lower ranges will be compensated for by the ECU, to a limit anyways. Not so sure about the late model (obdII) ECU being able to accept too many mods, although Jbrady has had good luck with his exhaust.

There's a company www.splitsec.com , that has some decent stuff for tuning altered, late model cars, reasonably priced too.