My ongoing Turbobaja build

[MarioVelotta]

We would load it under 2000 rpm with a low kpa, basically free wheeling. Like you where on a slight downhill, 1-2% throttle, and we made the AFR swing both ways. It only made it worse. It was happiest with a semi rich fueling and normal/high timing.

Which got me thinking.

Do you think with the large open chambers it could be misfiring on a cylinder? In turn unloading the r&p for a split second? I wonder if we turned on the the dwell table, added a buttload of dwell in that no load area if it would help fire a non optimal fuel mixture?

Wanna try it?

[turbobaja]

Hmmm, I think I see what you're saying. Remember how much difference in CHT there was during those really light loads, like 70F between 1/2. It seems to idle on 2 cylinders during warmup. Front 2 cylinders heat up quick while the rear 2 lag by quite a bit on a cold start idle. Cold driving @ part throttle is when it's usually the most upset. Heavy, rapid jerking at lower rpms. I'll roll into the throttle and it gets worse with more load, not quite lugging the engine, but trying to pull from 1,500-1,800rpm gently. AFRs usually very rich when cold like this, 11.5-12.5 w/WUE. If I clutch it and lightly rev it up, then ease it back into gear, sometimes it'll smooth out, sometimes not. I could see more spark energy helping out down in the lower rpm, light load areas. Let's give it a try . Last time I checked the coils don't get warm idling now.

[Clonebug]

Hello????

Oh Karl!!!!

Where arrrrreeeee Youuuuuuu!!!!

Please tell me you haven't become bored with your Baja and have found a new hobby........

[petew]

Please tell me you haven't become bored with your Baja and have found a new hobby........

Didn't you know? He sold the baja and all his tools and took up Cross-stitch.

[turbobaja]

Hey guys, been a busy season for me lately. Been working on the tune on and off between travels and other projects. I've been able to get rid of almost all the annoying bucking and jerking. Most of it seemed to be due to the rich tune with too much advance down low. I tried backing off timing and it just got lazy, so I pulled fuel instead and it woke up a bit and quit kicking back. I'm trying to lean out my very light load areas enough to keep the transition ON/OFF fuel cut less noticeable. It gets a little better after every drive. I've just been modifying my AFR target tables and letting VEAL rough in the VE table for me, working much better now with just minor smoothing after a VEAL session. Idling has been really good since having Mario's help. Still "open loop" with respect to the IAC valve, but the Active Timing is working wonders for stabilizing my idle.

Been thinking about upgrading my brakes...not all disc brakes are equal

[Chip Birks]

What brakes sets you running?

[turbobaja]

What brakes sets you running?

They're heavy, non-vented, solid disc, ductile iron wide 5 discs front/rear from AC Industries. They use factory VW calipers front/rear. Mechanical park brake in rear is nice, but it's the rear calipers themselves that just don't bite hard enough. I can lock up the fronts with heavy braking, but have to aggressively downshift at times to keep out of trouble with the back end.

[Chip Birks]

Mendeola has some nice looking stuff. Large vented rotors and such. How heavy is your rig? I have Airkewld Bad series on the rear of mine, same caliper as you have I'm sure, I haven't really noticed any major improvement over the drums thus far. I do only have them in the rear right now though, and I know that's not optional. Pretty sure I'm gonna go with the same Bad brakes up front but with the big 4 piston Wilwoods.
Have you tried needing with front and rear brake bias with a proportioning valve?

[Chip Birks]

Just double checked the Mendeola stuff, I don't see any wide 5. That's a bummer.

[turbobaja]

The baja weighs about 2,500lbs w/out me. It's usually packed with some gear and at least one other person, and I like to pull a small trailer that weighs another ~300-500lbs depending on the trip. I've got a Prop valve, but figured all it could do is reduce front pressure and I'm looking for more assist overall so I've never installed it. I also run a cutting brake in the rear circuit which could have some effect on the pressure to the rear calipers from the pedal. The system seems to be free of air with a firm pedal, but the cutting brake works ~ok at best. They're trying to stop a 31" tire and a lot of weight. The fronts seem to work pretty good, maybe if I get some nice 4-piston calipers on the rear I can dial it in with a Prop valve.

[Steve Arndt]

The crux, the parking brake. The upgrade bigger calipers (wilwood, etc) don't have a mechanical parking brake.

Have you experimented doing controlled hard stops and pulling the parking brake gently to increase rear braking force as a test? Before adding the proportioning valve this test may just give an idea if it would help. Decreasing front brake pressure would let you push harder on the pedal and get the extra rear force. Something to think about...

[turbobaja]

Hand/parking brake application is about as noticeable as cutting brake application. You can feel it, but it's not gonna do it in an "emergency".

I almost pulled the trigger on a set of Tatum rear discs and calipers last night. They use a separate mechanical park brake and its mount is integrated into the main 4-piston caliper mount with an anchor for the stock park brake cable. Only thing that I question about the Tatum setup is it's got an aluminum hub that I have to torque onto my axles. All the others seem to have a steel hub that bolts to the rotor and wheel flange. Tatum and Jamar seem to have the star shaped wheel flanges so they'll clear my spokes and I won't have to spend additional $$ to have them machined like I did on my AC Industries setup.

[Chip Birks]

My Airkewld brakes have an aluminum hub as well. He offers 2 different types of aluminum for the rears. One that is his standard style, and then his race strength. I have the latter. Hoping they don't strip the splines out. They are in service on a vw pro mod or two, so that's a little comforting.

[turbobaja]

So I pulled the trigger on a set of Tatum Motorsports brakes for all 4 corners on Feb 19th and just now am getting the rears installed. Well, trying to at least. The fronts are 'yet to be machined', I guess, and I'll be waiting until Tatum finds time to cut a pair of hubs for my BJ spindles (only LP, combo, etc options, so had to "custom" machine them). This is their busy time of year and my front brakes work ok for now, it's the rears that really need help. Lucky for me, other vendors stock and sell Tatum parts. So my rear kit has been here for months...



Had to cut off the old caliper mounts to clear the new parts, and with everything loosely bolted on, it would appear things are going smoothly...







No true mock up is complete without tightening the shiz out of things like they'll be in the end, so with that done, problems started showing up.



2 problems basically. The (5) spacers that mount the rotor the the hub are just a little too long, causing the rotor inner face to contact the caliper mount and also bottom out the inner pad inside the caliper body. The spacers have standard, fractional dimensions, along with all the hardware these brakes came with. They measure 11/16" long, 1/16" too darn long. I thought about cutting each spacer down, but a new set of spacers from MCMaster.com is 20 clams...done deal, hopefully.



Also the snout of the hub is too large OD to fit inside the axle seal lip, and binds against the face of the seal once tightened down, binding up rotation and surely gonna chew up the seal. I need to cut it down to the size of the shim.




Of course I've waited until almost too late to make this upgrade. My goal is to be racing at Woodburn OR in a few weeks and I'd like to make a few other upgrades while I'm doing the brakes. I need to pull out some of the "auxiliary" harness and choose a few circuits to trigger my ECU to control alki injection and a launch limiter of some kind. I'm not going to be pushing it to it's limits for the sake of a halfway decent time slip. I'm going to run a safe boost level (11-12psi) and try to be consistent. Plan is to flat-tow it behind my Bronco just to be safe. Gonna leave it in full street trim, no removal of seats or sound deadening. Probably take out the tool kit and jack, etc. Might put the smaller 235/75R15 tires on the back instead of the 31x10.5s for a little better "gearing", and be a little easier on everything.

[MarioVelotta]

Dude, why are you always so lucky The spacers are the easy thing, but finding a shop to take the hubs down a tiny bit shouldn't be to much trouble. If it is, my guy can do it for sure.