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Discussion Starter #1
Hi All,

I'm building a S2 Lotus Elise with a Honda K20a conversion.

The block is currently being built, new bearings and pistons but all standard OEM (very slight over bore so the block can be honed).

The car is being built for track work at circuits like Castle Combe and Thruxton (I'm in the UK) and some road use (I like a good European alpine tour).

I am aiming for 500whp per ton and the car should end up weighing around 800kg (1765lbs)... So need to produce ~450whp but with as wide a power band as possible (I would like spool by say 4krpm).

So far I am looking at the GTX3076R, is this the right choice?

Please bear in mind I am in the UK, so perhaps won't have the same selection of turbos available here (?!)

Many that's in advance for any advice you guys can give me.

Thanks,

Adam.
 

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Arouse the DAMPFHAMMER!
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Adam,

interessting project you are aiming for :up:

...I'm building a S2 Lotus Elise with a Honda K20a conversion...So need to produce ~450whp but with as wide a power band as possible
It would be easier to cover the necessary air induction cross section for engine and coolers with an Exige bodywork :D...

...there exists examples like this or that and kit's, but I would say for the mountain area of the Alps the cooling and the rear wheel slip would get to an issue. To prevent from this proper air piping, enough cross section for air in- and outlet in- and outto the engine bay, sufficient water intercooler and a stand alone ECU are necessary.
So far I am looking at the GTX3076R, is this the right choice?
Pretty big...first question to that...what fuel you want to drive? Likely 98 or 100 ROZ, don't you?
 

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Discussion Starter #4
Hi All,

Many thanks for the replies.

1. K20a2 I believe (UK domestic market Civic Type R) Standard compression (11.5/1??)

2. Yes Exige bodywork might be easier - but I have a plan! Large Air>Water charge-cooler, large bore water hoses, alloy rad up front and a very large pump!

I may yet go to Exige or GT2 Bodywork (I'm not so worried about cosmetics).

3. Already have the standalone ECU sorted, also have baffled sump, pro-alloy baffled and foamed fuel tank and larger in tank fuel pump (spec'd to 800bhp).

4. Fuel will be standard UK "Super" pump gas, so that's 98RON or in some places 99RON (this is NOT the same as USA octane ratings I think?!?)

''In the UK, Octane on fuels is quoted as ‘RON’ or ‘Research Octane Number.’ Without going into great detail as far as methodology, there is another common measurement system called ‘MON’ or ‘Motor Octane Number.’ MON typically yields a numerical value 10 points lower than RON from the same sample of fuel.

The Octane number quoted on the pump (PON or Pump Octane Number) in the USA and Canada is an average of RON & MON (RON + MON / 2.) So if you are comparing UK & USA fuel, you typically need to add 5-6 points to a USA Octane number to get the EU equivalent.

Many thanks again guys!!:new_slayer:
 

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Arouse the DAMPFHAMMER!
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1. K20a2 I believe (UK domestic market Civic Type R) Standard compression (11.5/1??)
UKM, same as EUDM, K20A2 = 11:1

2. Yes Exige bodywork might be easier - but I have a plan! Large Air>Water charge-cooler, large bore water hoses, alloy rad up front and a very large pump!
:up:...what about the oil cooler?

3. Already have the standalone ECU sorted, also have baffled sump, pro-alloy baffled and foamed fuel tank and larger in tank fuel pump (spec'd to 800bhp).
:up:

4. Fuel will be standard UK "Super" pump gas, so that's 98RON or in some places 99RON (this is NOT the same as USA octane ratings I think?!?)
Yes, it is not the same, as there (RON+MON)/2 to rate the octane number is used...ROZ is the German acronym for RON, it is just the same.
 

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IMO the EFR is not even comparable to a Gtx... especially when you look at more than just peak hp figures.

There is also the 7163 that can make the op's desired hp level and that would have instant response
 

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I like these as well, but the gtx are also great and you can't go wrong with either. How is the spool on these turbos? Can either make full boost by 4k?
Short answer: Yes.

Long answer:
I built up a "similar" car (see Midlana in sig) with a K24 turbo using a GTX3576R, which replaced a GT3071R. Both turbo plots are overlayed below with the top lines being the 3576. The dyno sessions were several years apart and the higher power of the -76 was due solely to slightly higher boost. Both spin up at around the same rpm, in the low to mid-3000s.

Two things to keep in mind: This is a 2.4 liter engine, so an otherwise identical K20 will make about 20% less. Also, the plot is from a Dynapack dyno notorious for reading ~20% higher than typical drum-style dynos, so figure another 20% there. So take that "444 whp" value and remove 20% for being a Dynapack, then another 20% because yours is a K20, ending up at around 284 whp.

That said, you'll gain some of that back if you rev the K20 higher than 8000 rpm, so you may end up around 320 whp or so. Also, I'm running 9:1 compression; your 11:1 compression will gain more back, so maybe around 350 whp or so, but at that high a compression you won't be able to run as much boost, so who knows. Anyhow, there's some more numbers for you to play with!

 

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Arouse the DAMPFHAMMER!
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...your 11:1 compression will gain more back, so maybe around 350 whp or so...
Sl0wlane, you really want to keep the stock CR? I thought, of course, this guy will integrate a 9.5:1-, max 10:1-Pistons, because the necessary boost level will be about 18-21 psi to get the 480 fwhp/450 [email protected] krpm (1 psi backpressure from intercooler incl. and 50 °C for MAT).

The problem is knocking, as your gas temperatures in the combustion chamber tends to scratch on the 400 °[email protected] area with that boost, which likely causes knocking. A 9.5:1 reduces those by about 35 °C, another 20 °C reduction by every 10 °C reduction of MAT (manifold air temperature) and of course fuuuuuel, a lambda of 0.78 or so will also help :D.

With a CR of 11:1/98 RON your ignition timing will be retarded significantly compared to a CR of 9.5:1. Consequently also your exhaust gas temperature increases in same effort and will wear/damage the turbine quicker. The hole system gets more heated, therefore more cooling power/cross section is needed. I would say up to 300 whp/100 octane a stock CR is good, beyond that the higher residual gas content of a TC application tends to cause knocking, which should get rid of by retarding the ignition timing.

To your question, the GT3076R (don't know the difference to the GTX3076R) would fit your demand very likely, peak torque would be around 5.5 krpm and peak power around 8.0 krpm with an A/R of 0.6 and a trim of 56 (according to the calculation :wink:)
 

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Discussion Starter #13
Thanks very much guys... I'm now discussing a low compression engine build (just pistons, rods and arps).. I don't think I need to with sleeves at this power level.

The alternative is to get the car running NA and save more cash for another engine build and all the turbo bits later... But that feels like spending money twice...
 

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Discussion Starter #14
Guys... Many thanks for the info!

Finally decided upon and purchased:

1. Owen Developments OD GT3579HTA M-Spec Turbo
2. TiAL 44mm gate

The engine will be built with forger Pistons, rods rtc for a compression ratio closer to 9:1.

Hoping for 500bhp+

Should be fun in an Elise!
 

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Arouse the DAMPFHAMMER!
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...Should be fun in an Elise!
Aaaaahhhh...maybe beyond 140 km/h :D, below that the accelerator pedal dip in would generate pretty much torque, making the cornering a bit more tricky :D.

...for a compression ratio closer to 9:1....
You still will use 98/100 RON fuel? Which piston design or make/part number?
 

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Haha... Yea, I think it might be a bit of a handful!

I'm aiming for full traction control, boost by gear, and probably only enable full boost from a steering wheel mounted "over boost" button.

And perhaps 2-step launch control and ALS further down the road...

I will only be using standard UK "super unleaded" 98RON... Might have it mapped for race gas omce it's all running well.

No sure on Pistons yet, that's with Clockwise :)
 

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Arouse the DAMPFHAMMER!
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I'm aiming for full traction control, boost by gear, and probably only enable full boost from a steering wheel mounted "over boost" button...perhaps 2-step launch control and ALS further down the road...
You are saying ECU is drive for you :D...aaaahhhh :D gone sweet manuell light car concept gone...curious about what Colin, one of the greates English car engineer and enthusiast, would say about your ECU's capability, as he loves to keep the racers and their cars at the limit for the best times :D

...No sure on Pistons yet, that's with Clockwise :)
LOL :D...ok, curious about your MBT to knock margin coherence at WOT...depends on your cams and piston design, but I believe there will be cuts due to advanced knock margin for 98 RON/9:1/~26 bar [email protected] krpm
 

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Discussion Starter #18
curious about what Colin, one of the greates English car engineer and enthusiast, would say about your ECU's capability, as he loves to keep the racers and their cars at the limit for the best times :D
One wonders what he might say about the latest Exige V6s then? As that's totally filled with electronics, traction control and electronic stability systems :D

Thanks again for the input thou, I will be keeping it all in mind! I know keeping the charge cool is going to be the biggest issue... And I'm yet to decide... Keep the Elise body and front mount 3 large radiators for a chargecooler... OR.. Go all out bonkers and roof mount a huge intercooler RS200 style...
 

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Arouse the DAMPFHAMMER!
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One wonders what he might say about the latest Exige V6s then? ...
For me, that's no real Lotus, just the same chassis...I think he wouldn't mind at all :D

...I know keeping the charge cool is going to be the biggest issue...
Yes, indeed :D. Nice challenge. Don't you think this was already solved, e.g. in the King's Elise?

More there: http://kingsperformance.com/kp-lotus-elise-power-packages/

Or there: http://k20elise.com/honda-k20-swap-parts-modifications-list/k20elise-build-overview/376
https://youtu.be/2NE4vS62TmY

And some others at http://www.lotustalk.com/

...Go all out bonkers and roof mount a huge intercooler RS200 style...
I wouldn't do that...the Elise cooling cross section area is limited, also the clearance space. A Exige body would be a better one for that. But as mentioned above, there are possibilities :D...maybe you have access to E85, which would be great, as the charge cooler wouldn't get that big for the same knock margin :D

In terms of drivability I would choose more SC (http://www.tts-performance.co.uk/#!lotus-elise/celz) than TC...same peak power, just a bit lower torque line below peak power...I am convinced the TC Elise would be fun at fast tracks like "Grüne Hölle" (Nürburgring)...for me hill climbing is furthermost application with slow corners, great VS band from 30 to 200 km/h, therefor a 300 BHP NA is the my way...SC could be next stage :D.

Which gear box inserts do you use? I would recommend stronger everything (e.g. http://www.kmodperformance.com/K-Series--TRANSMISSION.html), at least for 1.-4....as those 400+ Nm-guys to often has broken teeths, even with that light car, the gear switch dip in torque is nearly the same: huge and like a hammer blow for the notched impact strength of the teeth (tip in retard, gear related boost a.s.o. are good technologies to reduce that, but reality shows always a need for higher requirements levels because of imperfect human being :D)
 

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Guys... Many thanks for the info!

Finally decided upon and purchased:

1. Owen Developments OD GT3579HTA M-Spec Turbo
2. TiAL 44mm gate

The engine will be built with forger Pistons, rods rtc for a compression ratio closer to 9:1.

Hoping for 500bhp+

Should be fun in an Elise!
Did you ever finish this? Any dyno graphs?

Curious, since I'm thinking of going GT3582R twin scroll with a K24 and not quite sure how well that'll work.
 
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