The GTM Supercar Build Log

Archive for the ‘Engine’ Category

RaceLogic Traction Control Installed

Thursday, June 21st, 2012

I’ve been meaning to get this post up for a while now, but better late than never!

Last month I finished the installation of the RaceLogic traction control system. I can say this system is pretty amazing now that I’ve put a few hundred miles on it and have played with it a bit. The RL system monitors all four wheel speeds and when it detects slip, misfires the engine using preset cut patterns. The cuts are so seamless I rarely notice the RL system stepping in – it just feels like the car has tons more gripping power.  I have not messed with the launch control system yet, but plan to play with it more over the summer.  The system allows you to dial in 0 to 25% of allowed slip. 0% being ‘wet mode’ which allows zero slip, and only 5% in a straight line.  The system is very customizable once you hook a laptop up to it, allowing you to change fuel cut patterns, straight line slip allowance, etc. I have left everything at their defaults.

On to the installation:

The first task was getting to the injector wires in the engine harness. Not the most glorious task, but not real difficult either. Once the wires were isolated I picked a spot where I wanted to mount the RL logic box. I choose above the left side of the engine bay – seemed to be the best spot for it. The harness RL provides to the injectors is very short, so I had them ship me a much longer harness so I did not have to do a bunch of wire extensions to get the logic box injector wires to the injector wires in the harness.

Once I had the harness, weatherpack connectors were used to connect the RL injector signal wires to the ECU/fuel injector signal wires. This allows me to return the car ‘to stock’ in case the logic box fails for some reason (which would prevent the car from starting).  The RL logic box acts as a go-between between the ECU and injectors. ECU runs to the RL logic box, RL logic box outputs to the injectors.

With the harness done, some  additional logic box and digital controller wiring had to be done. A wire taps into your RPM signal (I used the wire coming from the ECU, in the tunnel), and you have to route a +12v switched power source to the digital controller and logic box. The logic box connects to the digital controller via a serial cable. I opted to put the digital controller just ahead of the engine cover/water fall below the shifter.

The last task was to connect the 4 wheel speed sensors (I used the already-present ABS sensors in the Corvette hubs, with new GM pigtails) to the harness wheel speed signal wires. Another weatherpack connector was used for this, for simplicity sake.

Everything was finished with any necessary grounds being routed to the chassis. The wheel speed signal wires are shielded so I just grounded the ground wire in each wire bundle to the chassis, along with the signal grounds.

I’ve included the wiring schematic I drew up with the pics below.

Push-button Start with RFID Security Installed

Sunday, July 17th, 2011

I finally decided to tackle installing the 2go-keyless push-button start system I picked up last fall. This is a pretty straight forward modification. Easiest way to tackle this, for me, was to go in from underneath. With the underbody aluminum out of the way there is some decent working room to make the necessary wiring changes, and install the controller box.  The old ignition was removed and the ignition wires were connected to the control box harnesses (only 4 wires to join up).  The start switch plugs right into the control box. A programming switch is installed under the dash ‘just in case’ the key fob fails and I have to manually start it. With everything in place I covered the control box in Thermotec heat shield and stuck it up inside the tunnel with some heavy-duty 3m adhesive tape. Harnesses were then connected, switches plugged-in, and ground established.  The only real trouble I had was once everything was tested and buttoned up, the system stopped working. After checking all my wiring, re-doing the ground connection, etc., I realized it was due to a faulty (or improperly programmed) fob. During my previous tests before cleaning everything up I had used the ‘backup’ fob. At least that one works.

The system itself is nice. The start button lights up when the car is running and flashes every second when it is ‘armed’ when the car is off. The keychain fob can be put into a manual or automatic mode. Manual requires you to press the button on the fob while starting, automatic is completely passive – just need to have it on you when starting the car. The range for the fob detection is about 10′. The start button itself can be lightly pressed to turn on accessories. Pressing and holding starts the car. Definitely nicer looking than the standard key ignition.

Engine Cover, New Trans Oil Puke Tank, and Engine Oil Breather Tank Installed

Sunday, May 22nd, 2011

Enjoying a rainy weekend here so I got a few more ‘to-dos’ checked off the task list. First on the list was installing the carbon fiber engine cover to make the engine bay look ‘pretty’. Since my old breather/oil fill cap would not fit/work with this cover I opted to install a remote breather tank for any oil fumes/vapors that get emitted through the breather otherwise.  This was something I’ve been wanting to do as the oil vapors and junk collect on the rear glass…and I wouldn’t want that stuff all over the new engine cover. The breather tank was mounted in the driver rear wheel well (lots of space back there to work with), and connected it to a screw in AN adaptor that fits the LS valve cover oil fill neck.  The engine cover then installs by sliding down over 4 set screws that I installed in lieu of the fuel rail bolts used previously. I just need to have some badges/emblems made to fill out the inserts now.

The trans oil puke tank was another issue I’ve been looking to correcting. The trans likes to spew oil in considerable amounts into the puke tank that I had installed previously, as it seems that the breather was mounted right over 5th gear. I acquired a new tank and mounted it high in the passenger rear wheel well so that any overflow from the trans should hopefully drain back down into the trans rather than just collecting in the tank. Time will tell on how well this current attempt works.

Sticky Shifting Dilemma and CAI Reinstalled

Sunday, September 5th, 2010

After each of my several longer drives in the GTM (20 min+) I noticed something that should not be happening – after 20 or so minutes of driving it became really difficult to shift the transmission into gear. I can only describe the feeling as ‘sticky’ or ‘sludgy’, as it would still shift fine, but it took considerable effort to move the shifter up and down into gears.

My first thought was it was because I did not have the trans oil cooler running. My second thought was that the clutch stopper was potentially stopping the pedal too soon and the clutch was never fully deactivating when shifting and when it heated up it was creating friction, and thus the sticky shifting. I activated the cooler pump, moved the clutch stopper back some more, and hit the road. Same problem after extended driving.

After numerous replies on the GTM forum I turned my attention to the thicker of the two shifter cables that run from the Brandwood shifter box to the trans shift rod. This cable controls the fore and aft motion of the shifting (ie: going into gear), and it also runs very close to the exhaust. The responses I received pointed to a potential overheating issue with the cable, causing the shifting issue. I ordered an Earl’s Flame Guard insulation sleeve for the cable, but in the mean time I used some extra 3/4″ corrugated high-temp resistant wire loom to wrap the shifter cable. I took the car out for the longest drive to date and when I pulled back in the garage the shifting was as smooth as it was when I first started the car. Problem solved 🙂

With the shifting issue taken care of, I set to reinstalling the cold-air intake. To create a buffer between the exhaust and the intake sleeves I actually just loosened the exhaust collars and rotated them so the bolts that run through the collars would support the intake. I then stuck some Thermotec heat barrier to the bottom of the sleeves where they rest on the collar bolts. I took an extended drive with this configuration and it worked great. Intake air temps dropped from 140+ degrees at speed when previous drives were logged, to 75 degrees. HUGE difference. Leaving the car at idle for several minutes after the 30+ minute drive had the IAT’s sitting at around 100 degrees. Previously the IAT’s would see 150+ degrees while idling. The CAI is pure win.

Exhaust Mesh Glued, Intake Tubing Secured, Fuel Vent Filter Hosing

Sunday, August 8th, 2010

With the gluing of the exhaust mesh pieces into place I have officially completed the GTM Assembly Manual.  I removed the diffuser to get to the underside of the mesh easier.  Hopefully the weatherstripping trim pieces will hold up to the exhaust temperatures, but if not I will either roll the mesh back (like the manual has you do), or come up with something else to use.

After gluing the mesh in place I secured the intake tubing to the frame. Josh found some cool swivel zip tie mounts that take 2 zip ties and have a swivel in the middle for flexible mounting. The bottom zip tie goes around the frame the tubing passes over, and the top zip tie goes around the tubing, effectively cinching it down to the frame without the need of any hangers or mounts.

Finally, I cleaned up the hosing that connects each fuel tank vent to the air filter. I lengthened the fuel hose and secured it to the top frame member of the chassis running  behind the rear window, and then secured the filter to the frame. Lastly, another fuel hose was attached to the fuel filter ‘out flow’ port and ran to the back of the car for disposing of fumes away from the cabin.

Exhaust Mounted, Idle Tuning Complete?!?

Thursday, August 5th, 2010

Finally got around to mounting the exhaust last night. Josh fabbed up an exhaust mount to replace the Kooks ugly (to me) mounts that wrap around the nice polished mufflers. The Kooks mounts mount to the trans (you make the brackets) to avoid flexing the exhaust against the stationary frame. Josh’s mount does mount to the frame, but it uses a rubber ‘bumper’ so that it can flex under revs, etc.  Works very nicely as I can see the exhaust moving with the motor as it idles, etc. The mount is out of the way and not very conspicuous.

With the exhaust mounted the rear mesh was set in place (with the cutouts made for the tips, previously). The mesh was slipped over the exhaust before it was mounted. After some fine tuning of the cutouts weatherstripping was applied around the cut edges. This creates a nice finished look. I will have to remove the diffuser to glue/silicone the mesh in place.

With the exhaust on I set to tuning again. The motor still dies after revs out of idle with the exhaust – I was hoping it would magically fix itself with the exhaust in place. Today I was blessed with an easy tuning session, however. I added 5g/sec of air across the entire base airflow table and it started up and idled great and took some flogging of the throttle without any problems. Revs, drops to idle flawlessly. It would seem that the garage tuning is done for now. Once I get the car inspected (the 20th!) I will be able to get it on the road and see what needs to be done (if anything) in regards to driveability.

Tuning Progress

Monday, July 26th, 2010

Spent the day working on trying to get the car to start and idle. Success! I can now start in neutral or in gear and idle all day long. Throttle recovery is better in gear than in neutral, so the car is now drivable it seems. Really hard throttle fluctuations have to be controlled on descent with some throttle blips to prevent stalling. That will get tuned out with time as I learn more about the throttle follower/cracker tables.

I am awaiting a new rivnut mandrel to mount the exhaust mount Josh made. Once that is here the exhaust will be mounted and I will refocus on tuning. I am confident that adding the rest of the exhaust will help the engine run much smoother as well.

Diffuser Almost Complete, Tuning Fun

Saturday, July 24th, 2010

I finally received the 3/16″ black rivets I needed to mount the louvers onto the diffuser this week.  Mounting the louver assembly is a straight-forward task. With the louvers in place I hammered (with a rubber mallet) the strakes onto the louvers and got them into place. With the strakes drilled and riveted I was ready to mount the diffuser on the car.

Since I had previously prepped the body for the diffuser install it didn’t take long to bolt it up. The only thing I have to do yet is jack up the car and rivet the underside of the diffuser to the frame of the car. That will not take long at all. The diffuser really completes the back end of the car and shows you how low the vehicle really sits.

In other news, I am still working on the tuning side of things.  I know I could pay a pro and have it done today, but I’m trying to learn how the computer works and if I can get it close on my own I will be happy! A week ago the car would not start with the 96mm tb, and it would not idle with it. I could only run it with my foot on the throttle (then it would die). Now I can start it and it will idle for 5-10 seconds before dying, and I can start it and coax it to idle indefinitely by bringing the RPMs down to idle manually then letting off. Rapid throttle fluctuations are the target of my tuning focus right now, as a hard rev in neutral (ie: 4000rpm+) will cause the car to stall when the RPMs try to come down to idle (overshoots the idle and dies).

Diffuser Prep, Tuning, Other Misc Stuff

Friday, July 16th, 2010

I haven’t posted in a few days, but I’ve been keeping busy with small tasks here and there:

– wired up the rear view mirror
– fine tuned the intake tubing positions so that they are ready for mounting when I get the intake duct mesh silicone’d in
– formed the exhaust and intake duct mesh pieces; dropped them off for powder coat
– picked up louvers from powder coating, will install on diffuser soon
– prepped diffuser by drilling more rivnut/bolt attachment points to the body to make it sturdier
– Josh finished the exhaust mount, waiting on a new mandrel to install bigger rivnuts to mount it and complete the exhaust
– making progress on getting the motor running properly: installed a Nick Williams 96mm tb, and am currently working on tuning it with HP Tuners. Motor runs if I stay on the throttle at 1000rpm or higher, but it dies if I let off.

At this point the interior is complete, and all that remains is buttoning up the exhaust and intake, creating a heat barrier between the two, installing the exhaust and intake mesh, and installing the louvers and diffuser.  I also need to get the motor to idle, too.

Cold-air Intake Installed, Mesh Painted, Trans Oil Overflow Tank Installed

Monday, June 7th, 2010

I recently revised my CAI design again and moved on to ‘version 3’. This version eliminates the bends as the piping goes towards the side ducts. Instead, I purchased 2 45-degree silicone sleeves and ran straight pipes with the intake filters on them to sit directly behind the side ducts. Very nice clean look. I will install some hangers to help support the ends of the straight pipes as well, and probably fab a heat shield to sit between the exhaust and intake.

Painted the remaining mesh inserts (front/rear small ducts, and hood ‘mouth’) black. They are ready for install.

I noticed when driving the go-kart that the trans was spewing oil from the breather cap on the top of the trans. Not a lot, but enough to make me want to do something about it. The solution is an overflow tank that will catch any leaked oil. The tank has a petcock  that allows me drain the oil when needed.  To complete this setup I need to install a hose attachment in place of the breather cap, and run a short hose to connect the tank to the trans.