[Hai5]

Hello there 👋

Last year I’ve build my motor to compete in a Racing series.

The engine made quite good power at the end, but consistent low torque out of it.

270,1PS @ 8570 RPM 224,8 Nm @ 6440 RPM

K20Z4
Fitted with Toda Pistons, oem Head gasket, oem con rods, Toda D Cams (Toda told me that I need more than 12.1:1 cr rather like 12.5:1)
Toda valve springs, toda vtc 35°, oem exhaust gear, Toda rep. Exhaust manifold, carbon intake Manifold, 70mm tb, Spoon N1 exhaust.


Will I get any benefits if I change the exhaust gear to a adjustable one ?
To adjust timing of the ex. Cam ?
How about moving to Toda C or even A3 cams ?
Would a Thinner head gasket be an option ?

Best regards

 

[Lotus]

35° limit on VTC likely induces torque losses below some 6k. @LotusElise might chime in here with more know-how.
Toda D are rather long duration on the high cam for a k20 I think.
a higher CR definitely helps, but a thinner HG further limits max VTC angle and with it torque.
Maybe machining the valve pockets can help allowing for a higher VTC angle.
Reducing the distance of head to block also shifts the exhaust cam timing.
In this case an adjustable gear wheel might help. But the exhaust cam‘s timing influence is not as big as the intake cam timing.

If you do racing and every single HP counts, it is worth the effort.
But then it would also be worth the effort to optimize the set-up using engine simulations.
Do you have a dyno plot for us?

 

[LotusElise]

Welcome to K20a.org @Hai5. You run your Civic on circuit races? How long per stint are they?

270,1PS @ 8570 RPM 224,8 Nm @ 6440 RPM...Toda D Cams

From the distribution quite race application matching, but the level of the torque at peak power and torque tells a story. I see, as @Lotus, a too big camshaft for your application and engine setup. I have customers with a stock short block, TODA A3 added stock cylinder head, a modified RSP IM and a TODA header with 265 PS and around the same torque. On my 310 PS/284 Nm 2-Liter-NA-engine there are also only TODA A3 cams. Power comes not basically from the cam, but the cam can throttle ponies quite much.

carbon intake Manifold,

Could you please be more specific on the Intake Manifold? I would need more specific data of the runner length and diameter as the IM has a huge effect on peak power.

 

[Lotus]

I can only guess that this is a Pracworks IM. It is the only carbon option I am aware of.

 

[Hai5]

In this case an adjustable gear wheel might help. But the exhaust cam‘s timing influence is not as big as the intake cam timing.

Unfortunately machining is not an option at the moment. In this case you would rather stick with oem Ex. Cam gear ?

If you do racing and every single HP counts, it is worth the effort.
But then it would also be worth the effort to optimize the set-up using engine simulations.
Do you have a dyno plot for us?

I do have.

Welcome to K20a.org @Hai5. You run your Civic on circuit races? How long per stint are they?

Thank you for the kind greeting.
Exactly, Sprint races. 50km per Race, two per day.

I can only guess that this is a Pracworks IM. It is the only carbon option I am aware of.

You are right! It’s the Praceworks one.

 

[Hai5]

This was my first motor.
K20A2: OEM Cylinderhead, OEM Block, Only Drag cartel dip cams, Toda rep. Ex. Mani., carbon intake.
VTC 40° via ECU controlled, Spoon ex., Nothing else.

From this point I’ve got literally no advantage over the K20Z head, the Toda pistons and cams. Very disappointed.
Equal times on track..

 

[LotusElise]

In this case you would rather stick with oem Ex. Cam gear ?

The TODA exhaust camshafts are already pretty retarded on their centerline with stock exhaust cam gears, which is good for good scavenging engine setups. The valve to valve clearance can be an issue. TODA D at 35° VTC must be around 5.5 [email protected] lift, which means not much room for further retard, while the valve-to-piston clearance is no issue on the exhaust at this centerline, the D have. I would keep it if the header is supporting it.

...the Praceworks one.

Could you please measure the runner length and inner diameter at around 30 mm downstream from bell mouth? The aim would be to see where it supports the peak power best.

 

[LotusElise]

K20A2: OEM Cylinderhead, OEM Block, Only Drag cartel dip cams, Toda rep. Ex. Mani., carbon intake.
VTC 40° via ECU controlled, Spoon ex., Nothing else.
From this point I’ve got literally no advantage over the K20Z head, the Toda pistons and cams. Very disappointed.
Equal times on track..

Understood and plausible. That was what I was mentioning. The cams are too big to make a nicer torque curve. Do you still have the drop in cams?

 

[Hai5]

The TODA exhaust camshafts are already pretty retarded on their centerline with stock exhaust cam gears, which is good for good scavenging engine setups. The valve to valve clearance can be an issue. TODA D at 35° VTC must be around 5.5 [email protected] lift, which means not much room for further retard, while the valve-to-piston clearance is no issue on the exhaust at this centerline, the D have. I would keep it if the header is supporting it.

thanks for the explanation!

Could you please measure the runner length and inner diameter at around 30 mm downstream from bell mouth? The aim would be to see where it supports the peak power best.

I will try my best!
Edit:

from this point to the head about 150mm length id: about ≈ Ø50mm

Understood and plausible. That was what I was mentioning. The cams are too big to make a nicer torque curve. Do you still have the drop in cams?

Yes, I still have the drop in cams.
Looks like there are comparable to the A3 ? Isn’t it ?

 

[LotusElise]

Yes, I still have the drop in cams.
Looks like there are comparable to the A3 ? Isn’t it ?

That's great. If you have the time and curiousity I would recommend those to test. You would make more torque almost everywhere with the actual engine setup by exchanging just the cams with the DC drop in cams. The TODA A3 are bigger in duration and lift compared to the DIC cams by DC. The TODA will increase the torque on the right side of the engine speed bandwidth over the DIC cams. The TODA D's are just to big in duration to give any advantage.

If you would share the engine calibration I could check if your header fits your setup too.

 

[Hai5]

If you would share the engine calibration I could check if your header fits your setup too.

i would if I could. Is it even possible to download the calibration file of the Doctronic ecu?
Otherwise I need to contact my tuner for the file 🤔

BTW. I’ve updated my recent post with the runner length etc.

 

[LotusElise]

i would if I could. Is it even possible to download the calibration file of the Doctronic ecu?

Yeap, possible. Plug the USB-cable to the ECU and download the file. If you need help PM me, I will send you my phone number.

 

[Hai5]

Yeap, possible. Plug the USB-cable to the ECU and download the file. If you need help PM me, I will send you my phone number.

it worked.