Reply With QuoteThe Government Motors computer returns codes and you run everything off the Chevy stuff. I don't know if you're aware, but GM computers are awesome, some of the best.Originally Posted by MoonieGT
How will emissions testing work on a car like this assuming it's registered in an OBD-II county?
SOLD - '91 BRG
SOLD -'99 Signal GreenLooking for my next car...
The Government Motors computer returns codes and you run everything off the Chevy stuff. I don't know if you're aware, but GM computers are awesome, some of the best.
TXMC: Drinkin, shootin, racin!
But does the GM computer return the right VIN? I thougth OBDII checked make/model/VIN along with the error codes?
So long as the motor is out of a newer car than the one it's going in it will pass emissions. Don't think they give a crap about the VIN.
"Pain is inevitable, suffering is optional." Haruki Murakami
Lots of questions there. Lemmie see if I can hit them all.
First up: oil pans
We know more about LS1 oil pans than I care to admit. I have probably worked with every production iteration GM has produced, from the trucks, GTO, CTS, 4th gen Camaro, C5 "batwing" LS1 pan, the Corvette LS2 pan, and several aftermarket oil pans. No, our swap won't need a $825 custom made sheet metal oil pan (in my experience these designs always leak), it will be built around one (or both) of the two common LSx swap pans. Holley makes one for $400, and GMPerformance sells one for $145. We have both on hand for other swaps we're working on. Brandon took a picture of each one and then ghosted them together (see above). One of these two will work, if not both. All other production LS1 pans have a lot more bulk at the front portion of the pan (right side in picture above), which gets in the way of the K-member and steering rack. We are building a custom tubular K-member to clear the oil pan + our own design real full length headers, unlike all other kits which use off-the-shelf shorty headers (restrictive) and expensive custom oil pans.
Accessories is easy: the most compact accessory drive layout for the LSx motor is the 1998-2002 Camaro/Firebird set-up. The C5 Corvette has crazy wide placement of the alternator, the truck stuff is insaley tall, the CTS and GTO stuff is unique and also too big in places, and the C6 bits are wacky. The early LS1 Camaro front drive brackets are still available from GM new, and they are all affordable - except for the power steering bracket, which is no longer produced. No worries - there is a cost effective replacement made from billet aluminum. This engine has MASSIVE aftermarket support.
Computer is also GM, and normally we build swaps using factory 1999-2002 Camaro ECMs and MAF sensors from the Camaro (3.5" ID) or C5 Corvette (4" ID). Cheap, plentiful and easily tuned with HPTuners or LS1 edit, among other open source software set-ups. $75 buys you a license and you can tune to your heart's content.
Emissions is trickier, but if you want 49-state OBD-II compliance it is possible. Just use a full OBD-ii wiring harness and substitute/hook up all of the Camaro emissions systems to the Miata. Even the most basic race harnesses still have an OBD-II port for programming and diagnostics.
JasonM picked up a ZF 6-spd and bellhousing today so that will be tested in this Miata soon!
Thanks,
Terry @ Vorshlag
Last edited by Fair!; 08-29-2012 at 08:59 AM.
Terry Fair @ Vorshlag Motorsports
Awesome! Thanks for the info! Really looking forward to this build.
Will a scattershield in place of the factory LS1/T56 bellhousing provide additional clearance to the miata unibody?
I have used SFI rated scattershields and they tend to be LARGER than factory style, aluminum bellhousings.They are also much heavier and somewhat expensive. When you think about what they are made to do - basically contain a bomb - its to be expected.
As you can see in the picture above, the TKO/3550 trans with the scattershield has a huge "can" as opposed to the T45 and T56 factory bellhousings.
And yes, the TKO/3550 transmission shown is much shorter and lighter than the T56 and ZF S6-40 we have already test fit into the Miata LS1. We have a kit Cobra with a Tremec 3550 behind a big block Ford V8 in our shop right now... looks encouraging. That was option #3.
Terry Fair @ Vorshlag Motorsports
Update?
It is too fAST to post.
Polished Turd Racing
Mick wrote: "I think Jerrett is the best autocrosser I have ever seen naked."
Terry and Vorshlag always have several project cars going at once, so there will sometimes be a wait between updates. But, he will get around to it. Keep up to date with all of them at http://www.vorshlag.com/forums/index.php.
After considering a number of transmissions and a few different LSx options, the owner took our advice on the transmission and we are buying one along with the supporting accessories (bellhousing, T-O bearing, shifter) and having the engine build finished. More fab when the parts arrive with a good writeup on -why- we chose those parts for this build.
Awesome! Can't wait!
Project Update for October 1, 2012: Well we've had a busy few weeks since the last update, after the blur that was August (Pikes Peak hill climb event), spending September racing at the SCCA Solo Nationals, a Global Time Attack event, and some other autocrosses. But the LS1 Miata project hammered along with a few test fits, some changes, new parts arriving, and key decisions being made. We acquired several donor parts, weighed and tested each of them, and whittled down our options quite a bit. Let's get caught up:
Three Transmissions, One Winner
The transmission to use in this chassis was always an unknown. The tunnel is tight in some areas and we didn't want to require our end users to hack up the tunnel in their cars to fit the transmission. A little engine bay trimming isn't so bad, but slicing and widening the tunnel is major work that most people do not want to tackle - us included!
The first manual transmission candidate we tested with was the Tremec T56 6-speed transmission. This one is very well known, but with increasing demand and a finite supply from the 1998-2002 Camaros and Firebirds, the used prices have been creeping up towards $1500. The T56 "Magnum" (really just an aftermarket version of the 2010+ Camaro's TR-6060) is around $2800 new, but has increased torque capacity to 700 ft-lbs among other needed improvements. We used one of these in our E36 "Alpha" car behind a 490 whp 7.0L LS2 and it was a great trans. The Miata fitment testing we did on the LS1 + T56 fit "pretty well", but still had some width limitations inside the stock NB chassis' tunnel. We really do not want our LS1 swap kit to require tunnel surgery and we want the engine as far back as possible, so this gave us reason to think twice.
1998-2002 GM F-Body T56 weighed in at 125.8 lbs, dry.
The T56 also didn't have an easy way to attach the Power Plant Frame ("PPF" or Torque Arm) to the rear end. Also, this transmission is relatively heavy at 126 pounds. It is a great transmission, capable of handling some good torque (450 ft-lbs), shifts well enough, but has two overdrives... which is overkill for this chassis.
Next up, we purchased and tested with the ZF S6-40 6-speed manual from a 1989-1996 Chevy Corvette. This "ZF6" is a freagin' TANK of a transmission, used in several BMW models (with a different tail assembly missing the PPF mount) with either 650 or 1000 ft-lbs of torque capacity in stock form. It also has a provision for a very similar torque arm as the Miata, as used in the C4 Corvette. That was my favorite choice up front, but as some of you pointed out, it has a few flaws.
1989-1996 Chevy Corvette ZF S6-40 weighed at 153 lbs, dry.
First is that weight! Good grief this thing is heavy, even using a factory magnesium C4 bellhousing. That big torque rating comes with a lot more steel on the internal gears. It also has a divorced shifter that mounts to the body, unlike the T56 which has an internal rail shifter (which makes for better shift feel and easier swapping). We found a good specimen with a magnesium bellhousing made for the LT1/LT4 engine, but it was going to take an expensive adapter plate to mate to the T56 bellhousing made for the LS1 engine - and it would only gain weight.
The shifter location was not right and the clearance to the tunnel was non-existent.
Finding the ZF S6-40 new is impossible, as they have been out of production for over a decade. Finding them used is difficult because they only came in certain C4 Corvettes and rebuild costs were also high. Physically the remote mounted C4 shifter location was way too far forward and the transmission itself was WIDE. There was no way this big beast was going to fit the Miata tunnel without a major fight. The only feature it added was the potential to use a modified C4 PPF, but that was not enough to overcome the many other obstacles. So the ZF6 was a dead end. Hey, you sometimes have to try something to find out what works and what doesn't. We had seen weights listed all over the place, and now we know.
Yes, some of you figured out this was the transmission I eluded to in my first post, and yes, you were right that it is not a good swap candidate. I am not always correct.
Our third choice was the Tremec 3550/TKO series 5-spd, and I think we have a winner. This 5-speed has an internal rail shifter and only weighs 95 pounds, but the two aftermarket TKO versions have 500 and 600 ft-lbs of torque capacity. They are hard to find used, but only cost $2200-2300 brand new. Of course it has no provision for the PPF, but I have pretty much given up on this as an impractical goal. Sure, we could hobble together something that attached to the back of the TKO, but we already have enough custom fabricated parts in store for this swap to make all of our other "wish list" items work.
We have seen these TKO's in all manner of race cars and kit cars, including a Cobra with a Ford big block that was in our shop for some work for about a week. We got to measure the trans, drive it, and this trans is pretty slick. It is so compact, yet so strong! The only question left was which aftermarket version to use?
TKO 500 vs TKO 600
There are actually 3 choices when it comes to the GM pattern Tremec TKO transmission. The differences in torque rating and costs all come from some internal gearing differences. But there are key reasons why we want to use the 600:
- Tremec TKO 500 Chevy/GM - TCET4616
- Transmission is rated at 500 lbs. ft. Torque
- 3.27, 1.98, 1.34, 1.00, .68
- Tremec TKO 600 Chevy / GM - TCET5009
- Transmission is rated at 600 lbs. ft. torque
- 2.87, 1.89, 1.28, 1.00, .64
- Tremec TKO 600 Chevy / GM Road Race overdrive - TCET4618
- Transmission is rated at 600 lb-ft. of torque
- 2.87, 1.89, 1.28, 1.00, .82
When you look at the ratios the "normal" TKO600 actually has a much more usable first gear for a car like the Miata. That tall first gear works better when you are using these transmissions in a light, powerful car with not enough tire (we won't ever have "too much tire" on these cars, heh). Way back when I was racing a Mustang 5.0L with the factory T5, it had "3.35" first gear. Later I went to a T5-Zcode, which had a taller "2.95" first gear and the change was very noticeable. The taller 1st gear was much easier to launch with at an autocross and the gap between 1st and 2nd was closer - for a more normal feeling gap. This TKO600 looks like that same upgrade over the TKO500.
So the TKO600 is where we would go, just for the better first gear. It also has a slightly taller 5th gear, for better highway cruising. There is also a TKO 600 "road race" version which is the same box, with the same taller first gear, but a lower 5th gear, for using all 5 gears in anger on a road course (much tighter ratio 4th to 5th). We don't think there's any road course where this would be needed on a Miata with a big thumping V8, and it wouldn't have as much of a "street friendly overdrive" as the .68 or .64. So the TKO600 with the .64 5th is what we think is ideal.
(continued below)
Terry Fair @ Vorshlag Motorsports
(continued from above)
The TKO's synchros are big beefy brass units, which are a bit unusual in construction; we have heard stories that they don't shift well above 6500 rpm, but then other racers using them say they work fine. We talked to a local Tremec rep that came by our shop last week and he said he can make these TKOs with a custom carbon blocker rings and synchro package so that they will shift like butter at high RPMs. For this build the engine we have in store isn't a super high rpm buzz bomb and will likely make peak power at 6000, so this isn't a concern this time.
Other Parts In Store
We are still exploring possibilities with the rest of the swap, but we do know the Ford 8.8" aluminum IRS differential housing from the Ford Mustang Cobra is what we will build the back of the car around.
Left: The BMW E46 188mm diff next to the aluminum 8.8" Ford. Right: RX8 front parts (top) will be used, but the rear uprights are 5-link and wrong (bottom).
Development on the front end is starting with a pair of Mazda RX8 uprights and hubs. These feature 5x114.3 bolt circle hubs, with much stronger hub assemblies than the 4 lug Miata. The uprights are nice aluminum units which we will build control arms to fit, and feature large front disc brakes (12.5" diameter). We still have a lot of work to jig up for these, and we will increase the wheel and tire size to work with the bigger front and rear uprights/hubs/brakes.
Engine Being Built
We have several swaps going on with stock LS1 drivetrains, but the customer for this Miata wanted something more. His 400 whp minimum power level meant that it would be a pretty hotted up 5.7L LS1, or one with some better head work and internals. We contacted HK Racing Engines in Houston and they came up with a potent little combination based around an LS1 5.7L block we sent them. It will have CNC ported heads, a small duration but high lift hydraulic roller camshaft, and extra beefy internals. The machine work is complete and they are assembling the longblock now. We are using one of two oil pans on this engine...
The pans above have a much lower front profile than the Camaro LS1 pan that people tend to (cut up and modify) in these Miata swaps, but are nowhere as expansive as custom fabricated oil pans.
You can see the massive improvement in the front of the sump area, where the steering rack would be. That picture we took is showing showing the factory F-Body LS1 oil pan ghosted over the GM LS1 swap oil pan. Hopefully the Holley or GM swap pan will clear the stock steering rack placement, and more than likely the Holley version will be what we use. We have all three pans here for mock-up test, which we will do as soon as the TKO600 arrives.
OK, that's all we have for now. We have the transmission nailed down, three oil pan options, new front uprights/hubs/brakes to work off of, the rear differential picked, and a few more things in the works. We still have a LOT of work to do, but this swap is being attacked between other LS1 swap jobs underway at the shop right now (five cars). Just wanted to give a few updates on where we are headed with this Miata swap.
More soon,
Terry @ Vorshlag
Terry Fair @ Vorshlag Motorsports
Must have been a very random unannounced appearance.
It's gravity.
Any recent activity on the project build?
90 Red NA
91 Red NA
99 Triple Black NB "Dimples"
Most likely large amounts of blow by, oil consumption, and oil starvation in hard corners!
5 lug hubs, forged aluminum A arms and an 18x10 wheel? Yes.
Actually, works a lot better with a slightly smaller tire. But that was what we had on hand to test with.
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