Basic K24 build- how does it sound?

accordselux said:

what is this modified vtc mechanism?

I'm doubting it's advancing timing 45 degrees :wow:

What does this mean, is there a thread on this?

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Cam Timing Mechanism

The biggest gift Honda has given to tuners of the K-series engine is the VTC mechanism. Located on the end of the intake camshaft, the VTC mechanism, via hydraulics, allows 25 [crank] degrees of continuous movement on the TSX and 50 degrees on the RSX. For all you old school tuners lurking out there still changing the jets on your carburetors who think you have to junk the VTC mechanism and go with a good old fashioned cam timing wheel, think again. In every naturally aspirated K20A and K24 engine we have tuned, the intake cam needs to be rotated through 25-30 degrees between peak torque and peak power. For emissions, the ability for Honda to rotate the cam to zero at idle to dial out all overlap makes for a very clean engine with no need for EGR. EGR porting is in place on the head, but is blocked off.

25 degrees of cam movement is fine for a stock TSX engine, but completely inadequate for a modified engine with as little as race headers and intake. A stock engine needs no more than 20 degrees of cam moment on the high cam. A well modified setup needs no less than 25 degrees on the high cam. Take a good look at the modifications we made to the VTC mechanism. If you have a TSX, you are going to need these changes. Although you could probably purchase and bolt on an RSX VTC mechanism for 50 degrees of travel, there is less valve to piston clearance on the TSX pistons. Our measurements suggest 45 degrees maximum cam movement is much safer. Allowing the full 50 degrees movement leads to a greater risk of valve to piston contact should you accidentally mis-shift and over-rev.

Click to expand...

VTC Cam timing mechanism


The biggest gift Honda has given to tuners of the K series engine is the VTC mechanism. Located on the end of the intake camshaft the VTC mechanism, via hydraulics allows 25 [crank] degrees of continuous movement on the TSX and 50 degrees on the RSX. For all you old school tuners lurking out there still changing the jets on your carburetors, who think you have to junk the VTC mechanism and go with a good old fashioned cam timing wheel, think again. In every naturally aspirated engine K20a and K24 engine we have tuned, the intake cam needs to be rotated through 25-30 degrees between peak torque and peak power. For emissions, the ability for Honda to rotate the cam to zero at idle to dial out all overlap makes for a very clean engine with no need for EGR. EGR porting is on place on the head but is blocked off.

25 degrees of cam movement is fine for a stock TSX engine but completely inadequate for modified engine with as little as race headers and intake. A stock engine needs no more than 20 degrees of cam moment on the high cam. A well modified setup needs no less than 25 degrees on the high cam. Take a good look at the modifications we made to the VTC mechanism. If you have a TSX you are going to need these changes. Although you could probably purchase and bolt on an RSX VTC mechanism for 50 degrees travel, there is less valve to piston clearance on the TSX pistons. Our measurements suggest 45 degrees maximum cam movement is much safer. Allowing the full 50 degrees movement leads to a greater risk of valve to piston contact should you accidentally mis-shift and over-rev.

TSX VTC mechanism showing material to be removed to increase the cam advance from 25-45 degrees


Engine characteristics.

The K24 is a long stroke engine. Naturally aspirated the engine's peak torque is around 6000 rpm falling off rapidly on the way to the redline. From about 6500 rpm up the power curve is fairly flat as a result. At 7500 rpm the piston speeds are about the same as that of a K20 at 8500 rpm, while trying to ingest about 15% more air through a head with similar airflow to a Type S. This means that the naturally aspirated K24 engine is difficult to get high RPM power from. Forced induction provides an excellent fix for this problem.

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