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Hi all, long time reader first time poster here. I'm in the process of building an Opel GT endurance race car and wanted to run a few questions past the community to get some good opinions or information.

The main parameters of my build requirements are that the motor must be built with OEM parts (except injectors, pistons, connecting rods, and crank) and also must be N/A. The OEM parts can however be modified (ex. ported heads)

The goal is to make between 240 and 280 crank HP

But onto the questions:

1: What would the ideal OEM parts K series motor be? a K24a2 lower with a ported k20 head? a ported TSX head? What about intake and exhaust manifolds? Basically if you could mix and match all the OEM K series stuff what would you frankenstein together for reliability and power?

2: I'm planning to modify my oil system by adding an Accusump system, an external cooler, and by adding baffles to my OEM oil pan. Is there anything else I can do to improve the oil system, especially with constant G forces?

3: Does anyone know of any similar builds or posts they could link me to? I'd love to get as much information as possible!

Thanks in advance, your input is much appreciated!

Car Tire Land vehicle Wheel Vehicle
 

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Welcome! here is a link to a K series endurance build

240-280 crank HP doesnt need too much "fancy" stuff on a K24. Are you allowed to have cams? You will want to research the theories on what has the greatest impacts on fuel efficiencies... does compression require more fuel than duration and lift of a cam... those types of things. you may find that you can get a K20 to do the work you want for fuel savings. do you have a fuel cell in the car now? how big is it?

do you have a measured amount of Gs you know the car has pulled? how the pan is baffled and the oil cooler might be all you need for the motor. I'm not familiar enough with the accusump system, but i'd want to keep things as simple as possible for an endurance car with +3 drivers.
 

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Exactly, K.I.S.S.

So if I read that initial info correctly, Reground OEM cams would be allowed. What fuel will you be using?

As far as oem, is that only k series items or are other honda parts from other honda engines allowed?
 

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1993 EG Hatch
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Nice, I like the Opel Breadvan.

For an endurance build I would recommend building for torque throughout the rev range and not concentrating on HP. A K24 does not like high revs, and if you are endurance racing it, keep the rev limit to stock or less.

I will also recommend using a RSX type S or S2000 oil cooler. This also requires a type S water pump and water pump housing. It simplifies an oil cooler install and also benefits as an oil warmer from a cold start. We run this setup on a mostly stock K24a2 and have not seen over 220 deg oil temps. If you run an external oil cooler, use a sandwich plate with a built in thermostat so you do not overcool the oil. The Mishimoto's are good.

Regarding the use of an accusump, I would recommend not going that route. You will need a valve on the accusump. Manual valves are the most reliable but require the accusump to be within arms reach of you in the driver's seat, so likely you need an electric valve. For some reason the electric valves have a high failure rate.

If the accusump is being utilized, that means the engine's oil pickup is dry, the accusump will start supplying oil at the pressure just before the pickup went dry. From that point on, the pressure will drop as the oil flows and the air that is compressed in the accusump expands. When oil makes contact with the pickup again the pump will need to scavenge the air in the pickup to re-prime the pump. From first hand experience, I have seen this take an alarming amount of time. Once the pump is re-primed and pumping oil again, the pressure to the engine will be low because the pump is both supplying the engine and refilling the accusump. If you have an external oil cooler in the loop as well, that can increase the amount of air in the oil circuit that has to be expelled before oil is flowing again. Depending on how bad the oil starvation is, this can happen multiple times during a lap.

The oil level in the engine's sump should be full when oil pressure is at it's peak. That means any time the oil pressure is lower, the accusump will have pushed out some of it's oil and the sump will be over filled. This could lead to oil windage, robbing hp and frothing the oil.

In order to reduce the dependence on the accusump, a baffled pad should still be used.

I have many years experience with an accusump in a Lotus Europa that I autocrossed and did track days with. I will never go down the accusump road again.

I am currently endurance road racing a K swapped EG civic using a Moroso road race oil pan. Knock on wood, we have had zero oiling issues with the Moroso pan and type S oil cooler. We run the car on 225 wide Hankook RS4 tires
 

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Arouse the DAMPFHAMMER!
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Welcome to K20a.org @K24OpelGt.

I'm planning to modify my oil system by adding an Accusump system, an external cooler, and by adding baffles to my OEM oil pan. Is there anything else I can do to improve the oil system, especially with constant G forces?
I have seen this take an alarming amount of time
My first thought too @TedR, the Accusump System is way too slow to be the right counter challenger of the G-forces. It's like an anti-knock-system, which reacts on a failure not as a preventer of an failure. The only stuff what helps is preventing the oil pump from surge at all time. There are two systems, wet and dry sump. If you want to go with an wet sump system you need to keep the oil at the sump by baffling it properly. There is a company claiming their baffled system can handle up to G-forces of 2.0. I will find it later...
 

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Welcome to K20a.org @K24OpelGt.


My first thought too @TedR, the Accusump System is way too slow to be the right counter challenger of the G-forces. It's like an anti-knock-system, which reacts on a failure not as a preventer of an failure. The only stuff what helps is preventing the oil pump from surge at all time. There are two systems, wet and dry sump. If you want to go with an wet sump system you need to keep the oil at the sump by baffling it properly. There is a company claiming their baffled system can handle up to G-forces of 2.0. I will find it later...
Unit 2 Fabrication

The guys i race with said the Moroso pan is okay for about 1.4-1.5 Gs. This was consistent feedback from the group. The TrakTuff pans were a little better getting to 1.7Gs before having oiling issues, but it was an inconsistent pan for each user that i talked to. Most are on the Unit2 pan now and they all love it... they all no longer worry.
 

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2002 DC5 Type S
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For an endurance build I would recommend building for torque throughout the rev range and not concentrating on HP. A K24 does not like high revs, and if you are endurance racing it, keep the rev limit to stock or less.
I did SCAA/NASA schooling with a supercharged K24, you are right it does not like high revs from downshifting, rev-matching, and spiriting towards corners purposely being able to stay in gear longer. The K20 has more tools than the K24 and with the right intake, header, and cams it is able to compete with the K24 on the straights.

I own a K20 in a DC5. I love it, I am getting more power out of it.
 

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96 civic HX K24a
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My ideal setup using oem cams/manifold
K24a2/k24a block 10.5:1 CR
K20a2 /k20z1 cylinder head
K20z1 intake cam
K20a2 /k20z1 oil pump
K20a2 /k20z1 water pump Housing with oil cooler
RRC manifold or ported RBC
K20z1 harmonic balancer
Type s throttle body if aftermarket isn’t allowed, (probably will make the best tq with the oem TB )
Basically I would put every compatible part off the k20 models onto the k24 to give it as much life on the racetrack as possible. Rev limit 7500 or lower for extended use is advisable. If you are after anything upwards of 230 wheel ponies it will take a set of larger camshafts. If you port the head, bigger cams, and an aftermarket manifold/tb the party really starts. But with that stuff comes a higher peak rpm power usually and that probably isn’t ideal for this kind of racing.
 

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I run a stock K24A2 in my endurance racing 1985 Supra. With a KPower intake (+ 70mm eBay throttle body) and modified S2000 OE header it makes 215hp/170tq on a chassis dyno (higher when measured on a roller dyno). At 2650lb with driver the car is capable of running at the front of most Champcar races.

With a Front engine/rear drive orientation you will want to use an oil pan designed to match, and you definitely want to replace the OE oil pump with a K20 pump. I run Megasquirt MS3 Pro for engine management, they've finally sorted a few bugs in the programming and it runs everything including the VTEC and VTC.

What are you thinking about for a transmission option?

 
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