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Post by jwagner on Jan 27, 2017 3:57:30 GMT
Pulled the trigger on a KMiata swap kit to put a K20 into my Exocet. I got a ride around Laguna Seca last fall in the KMiata K24 Miata and was really impressed, to the point that I was really thinking twice about whether it made sense to put that much power in a 1500lb car. But the extra 75HP+ that we should be able to get out of a K20A2 should go a long way toward making the Exocet competitive in the 2 liter classes we play in - SCCA D Mod and Midwestern Council C Race time trials. The goal is 250 whp and 1425 lbs wet. We're at 1489 lbs now and the K20 should be lighter, especially since the power steering stuff is going away.
The KMiata stuff is on order and we should have the parts in a couple of weeks. We're having a subframe built that will take a NA manual rack. And we're looking hard for a K20A2 - leads appreciated.
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Post by phocup on Jan 27, 2017 9:04:25 GMT
Very nice! Going to be following your build like I'm following the 500HP K build on miataturbo. Is the only reason you picked K ?
Seems from my mental math, HP / $ wise, LFX is a much better deal, though that would put you in E-Mod and you might have to add some weight.
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Post by jwagner on Jan 27, 2017 16:01:51 GMT
I want to stay in the 2L classes and the K20 seems like the best/easiest option. The car should be a little lighter and better balanced, and will still have a great power/weight ratio. Agreed on the LFX, but that would put us in the unlimited time trials class, and as you mention - E Mod for AX. Plus, it just seems excessive in a mostly track driven car.
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Post by phocup on Jan 27, 2017 17:09:05 GMT
Make sense. I just talked to David this morning and he gave me his standard recipe for a 250-275WHP K20 for D-mod.
K20 longblock
12.5:1 wiseco pistons
Drag Cartel 2.2 or 3.2 cams and supertech springs
Ported Ultra Street manifold
Our 4-2-1 race header
conservative 8500 rpm redline ( 91 pump gas )
Are you doing something along the same line ?
Also, seems like there's been A LOT of interest as Exomotive sold a bunch of chassis over the winter and I'm sure plenty of them will be in D-mod with K20s so you'll have plenty more competition soon!
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Post by jwagner on Jan 27, 2017 19:12:46 GMT
I was heading in the same direction, although I was hoping to find an engine that didn't need the bottom end refreshed, so no upgrade on the pistons/rods. NA K20s are supposed to be damn near indestructible so the only reason to pull it apart would be more compression and I think that head updates are more cost effective, even if I leave some HP on the table.
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Post by phocup on Jan 27, 2017 19:37:20 GMT
Hah! I JUST emailed David this. K20A from JDM type R carries a premium on Ebay but has more HP / torque / rev than normal K20A2 as well as 11.5 compression. If it saves you from having to pay for a full blown bottom end build + new piston / rods, it might be a good compromise solution.
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Post by dietcoke on Jan 27, 2017 22:43:52 GMT
You might as well build the car for EM, it is heavy for DM, because your weight minimum is 1385 pounds WITH driver, and a 1600 pound car isn't competitive. You could come in right on the 1700 pound minimum (with driver) in EM.
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Post by jwagner on Jan 28, 2017 22:42:04 GMT
You might as well build the car for EM, it is heavy for DM, because your weight minimum is 1385 pounds WITH driver, and a 1600 pound car isn't competitive. You could come in right on the 1700 pound minimum (with driver) in EM. Yeah, but them I'd have to compete with you - You're right, the car will never be a serious DM contender. Too heavy and too wide and there's too much purpose built for the class running now. There's also the driver, which is going to be a problem no matter what class... |
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Post by jwagner on Feb 21, 2017 23:06:08 GMT
Found a K20A2 in a salvage yard near Detroit. 80K miles, $1600 shipped without starter, alternator, ECU ($50 each at local salvage yard) or wiring harness. Was lucky to find a harness for eighty bucks on craigslist, they're normally around $200.  Need to find a Honda motor builder near here to freshen the head and checkout the bottom end. Have a bunch of new parts - oil pump and chain, oil seals, etc., and need to buy some more - timing chain, gaskets, etc.. KMiata is a little over an hour drive from me in the northwest burbs of Chicago. Picked up the subframe and a bunch of goodies Saturday.  It's been incredibly warm here in the (normally at this time of year) great white north and we used the opportunity of having a warm garage to pull the motor.  On the next warm weekend we'll swap it into the Miata. Not sure what to do with the turbo motor in the Miata now. Might make a good coffee table... Might seem a little odd to replace a turbo motor with a NA motor, but I want to take the '94 R back to stock, or very nearly stock, with air conditioning, a heater, stereo, etc., to make it a civilized daily driver. |
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Post by cooltech on Feb 22, 2017 15:26:27 GMT
We are also going the Honda (K24) route with the intention of campaigning the car in NASA ST2 class. There is a Weight:HP ratio limit of 10:1. With an Exocet race chassis with fluids, fuel cell, and driver, we are guesstimating weight at ~1750lbs. As such our target HP should be 175HP. We've built a few NA 1.8L Miata motors with 11:1 pistons, etc. and have been able to dyno 160-165 RWHP. No quite there - and arguably with less than OEM reliability. Throw in a K24 with requisite header & intake (to fit "Miata/Exocet" chassis) and RWHP should be approx 200. As such, we plan to de-tune the K24 to the class requirements of 10:1. We are Exocet chassis #226 and allegedly being created this week. We are anxiously awaiting arrival of the chassis!!! Here are a few pics.    |
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Post by jwagner on Feb 22, 2017 20:24:24 GMT
Your power and weight estimates seem pretty conservative, depending on the size of your driver. IIRC we were weighed at 1489lbs wet with the Mazda BP engine with power steering. Hopefully the K20 gets us under 1400 without PS.
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Post by cooltech on Feb 22, 2017 21:42:19 GMT
175lb driver (my son). We will have Exocet race chassis and planning to have a fuel cell and maybe a few extra tubes for protecting the fuel tank. With the Exocet's capability to stop on a dime, we have some concern about having a properly protected fuel cell. Will likely have on-board fire protection as well. According to David, K24 should save about 30lbs over 1.8L Miata engine and without power steering, we're saving maybe another 10 lbs or so? Race chassis + a few tubes + fuel cell + on-board fire protection...... I think we will be at 1700 minimum but would be oh-so-happy to be wrong!
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Post by phocup on Feb 23, 2017 22:34:39 GMT
You will be very close I think. I just corner balanced last week and came in at 1651# with 185# driver, sport chassis with extra cross diagonal, 1.6L drive train, 1/4 full gas tank, 10# light weight battery, no rear wing.
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Post by phocup on Feb 23, 2017 22:38:16 GMT
Ooooo .. dem be Oooohlins you're running! Fancy!
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Post by cooltech on Feb 24, 2017 15:02:48 GMT
Well, one day or another if a frame finally shows up - we may be suspended with those Ohlins! We tried the Ohlins on a track Miata a couple years back and were disappointed that we couldn't get them "short" enough to give us the race ride height we wanted. With a lot of adjustability and perhaps being a little on the tall side, we're hoping they might work on the Exocet without the spacers. (We have the spacers in case we need them - and can always fab something in-between, but hoping that we may not need them.) Our Excocet will have ONLY track-use so ride height can be a little lower than street or dual-purpose builds.
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