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Old 02-16-2016, 03:34 AM
zhao kan's Avatar
zhao kan zhao kan is offline
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Default Redsuns RX7 continues: How I dropped 6 seconds with 3 easy mods

write-up for this year:

As this thing sat going into chumpcar:



kyb oem replacement shocks and some sorta cut springs + header and exhaust and a filter making decent improvements on the stock 146hp engine. 225 wide re71r's for tires and hawk blues for pads. alignment of around -1.1 degrees front and a bit under -1 degree rear for camber... making it chew through front tires like crazy.... as usual in chumpcar mode, but it doesn't feel toooo bad, but it is clear lack of camber is murder, and

This took it to a wopping 1:35.4 second lap time at around 1am in the morning.






Plan: So mid august rolls around and there is a rule change coming next... meanwhile conroy has a bunch of parts sitting around. Project lets make a missle and see if it can drop 5 seconds to beat the STU record Dom K. set in his civic at 1:30.4?.

Braking:
good enough for STU. bleed brakes, call the rest good.
power: STU has some decent powered cars in it, the king of which is from what I remember is a k24, which I know from my RSX days dynos at 200whp with I/H/E kpro. The 146 crank hp engine even with a intake and header/exhaust isn't going to compete with that. maybe it's making 140whp on a good day. Short of doing an engine swap, modding for power is out.

This leaves tires, suspension.... and uncharted territory: aero.

Tires: This is easy. What am I allowed in stu? DOT slicks. What do I buy? hankook z214s. why? cheap, and grip well. and I cram the most tire I can under factory fenders, which is a 245 upfront. I hate staggered setups with no power, so I put 245s on the rear as well on some borrowed RPF1's conroy had laying around from chumpcar. Are tires going to drop 5 seconds? no...

suspension: luckily conroy has some decent suspension he ripped out of something or other... camber plates, adjustable ride height, various spring rates to choose from. Fun stuff, we go with the stiffest spring he has, and i max this thing out for camber. I also slam the car... because even with the suspension on as high as it goes up front, its retardedly low (wtf was this suspension out of? lol). Somewhat worrisome...

At the same time I also replace some worn bushings on the rear end that were responsible for some huge slop in how it handled in corners. Off it goes for an alignment and now it's sitting closer to around -3 degrees of camber upfront, which should be just about perfect, and a suspension that hopefully doesn't roll like crazy in corners.

Aero: the unholy uncharted territory I've never gone except with brief open wheel experience seeing how big a difference mucking with it can affect the car, and how significant it can help. Conroy pulls out a broken to shit front bumper, but it looks pretty good. it sits low, and has a built in ricer splitter. i'm liking it. 4 new holes in it later and 4 quick release zip ties, and its on the car. Now this thing looks like a missle car that was already fired into a wall...



but we need a wing too. Out comes a freeby ricer wing. It's made to work on a FC, it's adjustable, and it's very blue. Good enough. On that goes on a random eyeball setting.



This is really getto aero..... but it's still aero, and allows for some on the fly tuning at the track of how the car handles. It might help.

so after a weekend of work, this is how this thing sat: What a total piece of shit. missle car complete.

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Stratotech: FD - 68.3, NA FC - 68.9, NA MR-2 71.6 (Wet), NA MR-2 71.8 (dry), RSX - 73.0, GC8 WRX - 69.9, fugu's miata - 76.5 daytons+broken alignment and swaybar, em2ftl's civic - DNF
Edmonton Indy Track: IT2 FC race: 159.4 IT2 FC qualify: 159.5. IT2 class track records forever lol.
Race City: FD 129.x, NA mr-2 135.x
Castrol: NA FC 43.1 IT2 class track record until we run the short track again which may be never.
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Old 02-16-2016, 03:35 AM
zhao kan's Avatar
zhao kan zhao kan is offline
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So race weekend happens. I do a practice, find out it's really loose in the rear. thank god for the rear wing, so I crank that up, and now it's manageable. Qualifying happens and I pull out a 130.7.

I just dropped almost 5 seconds with tires, suspension, and some aero, but it's not good enough.

What is also painfully obvious is how little HP I have, as even with being on pole position in the IT run group, choosing to start the race at exactly where I want in my power band, and... i'm getting passed like crazy on race start. It feels like i'm down a good 75hp+


I also find out that it's not 130.4 that is the track record in STU.... Ryan Smith decided he was going to beat that record the race weekend before in martin's FD..... and did it with a 129.5. F$ck lol. So it looks like I mis calculated how muhc time i had to drop to beat the record

But the race weekend isn't over, and there is a money race left. I enter that, and find out i'm stuck in the fastest run group... in basically a chumpcar with a ricer wing. Great lol. Up against 28 cars all the way up to GT1, but I'm really worried about the 2 miatas. gerards seems down on power but chris S's has been rocking out 1:30s or faster all weekend so I give myself a chance of beating gerard if i'm on my A game, but little chance of chris. Well the race starts, and I actually get a good race start and barely get passed (I love you miatas blocking the high hp cars lol). I also manage to stay within a few cars of the leader. The GT1 car pulls away, but i'm in the middle of the miatas with some hondas on my ass. After a few laps, the miatas aren't as fast as I expected in this race, and i'm pulling away. Handling is making up for my lack of power and the car is working well.

But god damn it, yellow flag. fuck. Huge lead on 3rd is now shot, and worse 3rd is a honda with more power than I can handle. thank god the race start is predicable, and we have to go through the chicane... but 2 big straights is going to set me up to get passed without some luck. The GT1 car rockets out of the chicane letting me WOT it after him to catch up and then the green flag drops... and the honda behind me couldn't get a pass off down the straight before turn 1 because i stuck to the inside. We go into turn one with him on my left on the shitty outside line, and i scrape him off in corner 2. One more straight and i'm golden..... i stick to the right side of the track letting him have another shitty outside line if he wants to go sidebyside in the carousel... and he rams me before we hit the braking zone. I laugh knowing he just gave up the race, I take the carousel, and pull away never to see him again. What's also surprising is the GT1 car is not very far ahead..... and i'm actually wheeling him in about half a second a lap it seems. After about 5 laps of this and i'm now getting real close, he slows way down and lets me by. I'm now in first, and the rest of the race becomes a glorified lapping event, and is completely uneventful.

Pulling back in I look at the times... I managed a personal best of 129.70, and most of my laps in that race were 1:30s.

I missed the STU record by 2/10ths of a second, and dropped about 6 seconds with my crappy mods. And the interesting thing is the car still isn't setup very well..... leaving a lot on the table for improvement.
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Stratotech: FD - 68.3, NA FC - 68.9, NA MR-2 71.6 (Wet), NA MR-2 71.8 (dry), RSX - 73.0, GC8 WRX - 69.9, fugu's miata - 76.5 daytons+broken alignment and swaybar, em2ftl's civic - DNF
Edmonton Indy Track: IT2 FC race: 159.4 IT2 FC qualify: 159.5. IT2 class track records forever lol.
Race City: FD 129.x, NA mr-2 135.x
Castrol: NA FC 43.1 IT2 class track record until we run the short track again which may be never.
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  #3  
Old 02-16-2016, 03:43 AM
zhao kan's Avatar
zhao kan zhao kan is offline
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2016:

and now for 2016 i'm left wondering what to do with it.

Things it needs:

1) fixing the diff. It has a factory LSD which does not work, meaning it is a one tire fire every significant corner... meaning I am literally losing 0.5-1 seconds per lap from this.
2) tuning the suspension to actually be what is ideal, rather then the random guess alignment it has currently. Being loose in the rear end tells me it's not tweaked very well at all, and cranking the wing was just a temp fix.
3) proper aero. This thing could really use a full aero package. If done right, this may even be chumpcar legal still.
4) engine port is a possibility, as it is extremely frustrating to have to pass everyone in the corners, only to have them get easy passes on every race restart.
5) transmission. It's the best damn transmission the car has ever had, and conroy gave it to us because it wasn't good enough for the bandit...

I'm figuring most of the IT/STU crowd will end up in PTC, and I'd like to keep this thing as not too hard to put back to 100% chump legal.

Aero would be fun to see how fast I can make this thing without adding any power, but going wiht full aero is a huge points cost in nasa rules... and how fast it will make the car is beyond me.

Porting the engine is probably the easiest way to make this thing a lot fastest... and I know there are tons of chumpcars with ported rotaries, but is it technically legal for chumpcar?
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Stratotech: FD - 68.3, NA FC - 68.9, NA MR-2 71.6 (Wet), NA MR-2 71.8 (dry), RSX - 73.0, GC8 WRX - 69.9, fugu's miata - 76.5 daytons+broken alignment and swaybar, em2ftl's civic - DNF
Edmonton Indy Track: IT2 FC race: 159.4 IT2 FC qualify: 159.5. IT2 class track records forever lol.
Race City: FD 129.x, NA mr-2 135.x
Castrol: NA FC 43.1 IT2 class track record until we run the short track again which may be never.
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  #4  
Old 02-16-2016, 04:40 AM
Ron_e Ron_e is offline
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Yes porting is legal for ChumpCar if done with hand tools. CNC head porting must be claimed.
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  #5  
Old 02-16-2016, 04:25 PM
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GrantC GrantC is offline
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Quote:
Originally Posted by Ron_e View Post
Yes porting is legal for ChumpCar if done with hand tools. CNC head porting must be claimed.
Maybe once he's done porting the "heads" he can do a set of cams for his rotary...
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Old 02-16-2016, 11:00 PM
Ron_e Ron_e is offline
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Quote:
Originally Posted by GrantC View Post
Maybe once he's done porting the "heads" he can do a set of cams for his rotary...
I was giving hand porting versus CNC porting of heads from a piston engine as an example.

To clarify, hand porting of the intake manifold, heads, exhaust manifold, header, and port matching is all legal for a piston engine. CNC porting of heads for a piston engine must be claimed.

Porting of the intake and exhaust of a rotor housing is also legal if done by hand regardless of whether you do it or whether you pay someone like RX-7 Specialties to do it.
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Old 02-17-2016, 11:25 AM
matt matt is offline
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Quote:
Originally Posted by GrantC View Post
Maybe once he's done porting the "heads" he can do a set of cams for his rotary...
Don't be a dick.
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Old 02-17-2016, 11:26 AM
matt matt is offline
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That is pretty godamn impressive man.

My vote? Fix the LSD, go ChumpPort & Aero.
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Old 02-17-2016, 09:08 PM
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EM2FTL EM2FTL is offline
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Quote:
Originally Posted by matt View Post
That is pretty godamn impressive man.

My vote? Fix the LSD, go ChumpPort & Aero.
Agreed.

Seriously impressive drop in time, nice write-up Kris.
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Stratotech - 72.2 (EM2), 71.1 (RedSuns NA FC 2011 spec), 71.2 (NA MR2)

Castrol -
1:32.99 (FC - Chumpcar Edition)
1:29.1 (FC, PTC Edition)
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  #10  
Old 02-17-2016, 11:10 PM
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4kruzn 4kruzn is offline
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Always love Kris's write ups. And his use of creative ways to describe nice race parts and have them
Sound like junk. Lol. But seriously, nice driving and great use of low budget parts to make a huge improvement. Call me for ported engine and diff rebuild. We can easily pick up another 1.5 seconds. Hahahaha. Psssst.... Don't tell anyone.
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