M Coupe LTW build

[Calichase]

Out of curiosity on that dyno pull, were you using good fuel? I've seen similar high end dips when knock sensors pull timing thanks to lower quality fuel issues. just a thought

[FD3S]

Originally Posted by Calichase

Out of curiosity on that dyno pull, were you using good fuel? I've seen similar high end dips when knock sensors pull timing thanks to lower quality fuel issues. just a thought

On the days of the dyno I was using 95 octane fuel.
My tuner has available maps for 93, 95, 98 and 100 octane. I have chosen the 95 maps because you can find it everywhere.

I have put also 100 octane fuel and tried the car on the street and the drop after the 7200 was obvious again. However a forum member advised me that the car needs many tanks of 100 octane to adapt to it. I don't know.

Sorry for the thread jacking.

[Michael9218]

Originally Posted by M-Cast

Have you ever looked at Turner's IAT Relocation Kit?

I do have that kit. I have the temp probe in the tube in front of the filter box.

[Michael9218]

Originally Posted by Calichase

Out of curiosity on that dyno pull, were you using good fuel? I've seen similar high end dips when knock sensors pull timing thanks to lower quality fuel issues. just a thought

93 octane Chevron gas.

[racerbruce]

Such an incredible build - your technical acumen is over the top!

[M-Cast]

Michael,

I know you have been trying everything to shave weight and came across this and thought you might be interested.

This company has a full Lexan kit for the M Coupe
http://www.plastics4performance.com/...indow-kit.html

You could probably drop another 100lbs. replacing the glass.

[Michael9218]

Originally Posted by M-Cast

Michael,

I know you have been trying everything to shave weight and came across this and thought you might be interested.

This company has a full Lexan kit for the M Coupe
http://www.plastics4performance.com/...indow-kit.html

You could probably drop another 100lbs. replacing the glass.

Will,

Thanks for the link. I have talked to them. A rear window is on it's way. Side glass is too small to be worth the effort (their words). I prefer to keep the windshield glass.

My wing arrived, so I've been a bit of a made scientist working on a nice aero solution...more to come.

[Michael9218]

Originally Posted by Michael9218

The car was back in the shop to eliminate lingering bogus codes from the de-wire and to get the dyno tune. The dyno tune found 20 more hp from the off-the-shelf performance tune. There is an odd dip in hp at 7,200 rpm. Tuner thinks this could be some kind of harmonics with the exhaust as he wasn’t able to get rid of this. It’s not noticeable when driving the car. I do like the flat torque curve. I assume this is due to the stepped header design. Absolute values aren’t entirely relevant since different dynos and different days will produce different results. Motor is stock, with Supersprint stepped headers and catless exhaust and underdrive pulleys.

I believe I found the cause of this dip in power at 7,200 rpm. While at Road A this Sunday, it was wet and cold so I went out with the DSC left on. Climbing out of T7 on the backstraight I noticed a definite dip in power at 7,200, but only in 4th gear. So it appears to be speed related, not rpm related. As the day dried out, I turned off the DSC and the mystery dip went away. So it appears to be a glitch in the DSC causing a drop in power for a couple hundred rpm at that speed. Where it was happening on the track there was no traction issue, plus it was happening on the dyno rollers as well. Elsewhere on the track where I was accelerating through that speed were downhill so it wasn't noticeable.

[Michael9218]

Time for some aero (and an update)!

For the front aero, I wanted to go with a custom setup that gives me a large front splitter and dive planes to match up to a large rear wing. For now, I decided to mock up a working prototype using wood for the splitter and thin wall steel square tubing for the splitter frame. By my calculations, using thicker wall aluminum would’ve only saved 3 or 4 pounds. Future plans are to make a carbon fiber over foam splitter and either Swiss cheese the steel square tubing or replicate the frame in aluminum.

Earlier in the build, I welded on some down “C” channel with captive M6 nuts onto the front clip. So now I just needed to make a splitter frame that will bolt up into place…easy peasy…



I want the splitter to extend forward 6” and ride 2 ¾” off the deck. Total width is 70". To ensure rigidity, I chose to run square tubing bars forward to give support rather than using support cables. Just gives it a cleaner look , IMO. Of course, the tough part was making sure the frame was level fore aft and side to side. By making this frame, the splitter can be a simple sheet of plywood or carbon fiber (or alumilite or ABS…).
To mount the splitter, I welded in captive M5 nuts inside the square tubing and capped them with a 45 degree cut for a nicer look. I used countersunk fasteners for a clean underside. The back of the splitter is held in place with “L” brackets. This means only fasteners are used at the front so I don’t have to reach back in there to secure the rear of the splitter.

M5 nuts welded in square tubing.


Sizing up a sheet of plywood. Shovel nose splitter?


Mocking up splitter, fence and dive plane box.


Steel frame mounted to splitter. Note tabs on backside with captive nuts for the aluminum second panel.


Splitter and frame in position on the floor. Zero clearance splitter?


Underside of splitter.


I also chose to make the splitter rather short to make removal for loading easier (though in the end I made multi-section ramps so I don’t have to remove it). The idea being that I will make a separate panel to go behind the splitter. So the splitter goes back to the front of the wheel wells and an aluminum panel that is 32” x 32” extends the flat bottom past the wheel wells. Eventually the plan is to flat panel the entire underside into a diffuser.
To keep the plywood splitter from disintegrating in the wet, I painted and varnished it. This sheet is 15/32” cabinet grade ply. I also floated the underside of the panel with flexible spackle to give a smooth-as-glass finish. So far after several rainy sessions, it’s showing no signs of water intrusion. But I know it’s just a matter of time.

[Azeka1]

Very impressive! Thank you for sharing this. Roughly how much does this weigh in its current configuration?

[Michael9218]

To fill the gap between the fangs, I made a panel out of aluminum and riveted this to the underside of the bumper. Playing around a bit with the spoolgun for the MIG. Isn’t pretty but works pretty good! So I made the fence out of two pieces that I welded together.

Cardboard mock ups.




For the dive plane box sections, I made these out of aluminum and riveted them to the bumper. This way the splitter itself is essentially floating under the bumper and is not attached to it. It’s only attached to the frame. I also cut the front edge of the fender opening about 5/8” to provide needed clearance for the 275 Hankooks. I was getting a little rub when turning.

[Michael9218]

For the wing, I chose a 70” x 14” element with large end plates from RHR Performance. Since no one made a mounting solution I liked, I went it alone and fabricated my own. I first mocked up the mounting interface to the rear deck lid (which wasn’t easy since there isn’t a flat or straight surface on that damn lid), then suspended the wing in position and mocked up the mounts using cardboard. Once satisfied with them (much trial and error here…) I cut them out of 3/16” aluminum plate. These I had TIG welded at a local fabrication shop. Spoolgunning with a MIG wasn’t going to cut it! The wing is 2” above the roof line and half its cord past the bumper.

Multiple angles to deal with.


Made a jig to suspend the wing. Trial and error on uprights. Cardboard is cheap...


Using 3/16" particle board to make final template.


Bits ready for install...


And now the money shots...


Very happy with the results.






Gotta love the distortion in this view. Looks like the wing is 12' wide...

[dre99gsx]

Mad max wants his car back!

Very nice - purpose built.

[mattfwalters]

Holy crap. This is just beautiful work. Thanks for sharing.

[Michael9218]

Another loose end I wanted to address was the exhaust. I plan to use a diffuser and the stock fitment exhaust is in the way. I was also using a 2 ¼” BMS exhaust system. I wanted to go 2 ½” from section 2 all the way back. So I fabricated my own crossover pipes, bought a couple Magnaflow race mufflers (6” 5”x8”) and some V band assemblies and took it all to the local shop for TIG welding and install. I tucked up the mufflers so they’re out of the way, cutting a hole in the bumper and making the little pieces to give it a finished look. They’re solid mounted. I then made a couple panels to clean up the airflow until a proper diffuser is installed.

Made a jig to make two identical cuts.




Nice and tight.


BMS X pipe and the new race mufflers.

[Michael9218]

While tinkering around, I decided to make a wind deflector for the passenger side window. Not sure how much this will help, but it can’t hurt, eh? Looks the business…

[Michael9218]

Originally Posted by Azeka1

Very impressive! Thank you for sharing this. Roughly how much does this weigh in its current configuration?

I'm actually a little disappointed in the weight. Somehow 90 lbs materialized since last I weighed the car. Dry the car is now about 2,700 lbs.

More weight reduction is on the way...

[racerbruce]

Originally Posted by Michael9218

I'm actually a little disappointed in the weight. Somehow 90 lbs materialized since last I weighed the car. Dry the car is now about 2,700 lbs.

More weight reduction is on the way...

What are your thoughts in achieving the additional weight savings?

What will be your target weight, and what will be the weight to HP ratio??

[M-Cast]

Michael, are you going to be at the September Road Atlanta CCA event? Would love to see this out at the track

[Michael9218]

Originally Posted by M-Cast

Michael, are you going to be at the September Road Atlanta CCA event? Would love to see this out at the track

Unfortunately, no. Will be out of the country on vacation. I was there last weekend and will be doing the Chin event Aug 19. Made some big progress on chassis setup...

[ANILE8]

Originally Posted by Michael9218

With the transmission out, it made sense to use the ZF 5 speed I had in the shop. I also had the Bimmerworld strapless clutch kit from the S52 that will mate the S54 to the ZF tranny. The ZF is 20 lbs lighter than the Getrag 6 speed. Mounting the shorter ZF is pretty easy. Order yourself a transmission mount from a 2.5 Z4 that came with this transmission and it then bolts right up. The driveshaft did have to be lengthened 100mm by a local driveshaft shop. I also had to have a custom length DSSR fabricated for the gear selector.

Humm, I always thought our cars come stock with the ZF GS6-37BZ, not a Getrag. What made you stay with a synchro box?

I am thinking of changing the stock H pattern 6-spd to a sequential dogbox with straight cut gears from Samsonas or Hollinger RD6.

H pattern synchro boxes are so slow; after you have driven a sequential you can never go back.

[F360C]

Subscribed! Incredible build.

How are you liking the SLR front control arms? I am thinking of picking up a set.