Well, I got my car thrashed together and did very well at the rallycross last weekend. But watching the video, I heard some unusual noises at roughly 1:01-1:11 and 4:11-4:14.

http://www.youtube.com/watch?v=2DQdDXU1FTQ

I note that both times, the noise occurred in 2nd gear, maybe 4000rpm, and at the very end of the afternoon runs. I'm worried that it was detonation. I can't think of any other noise that might possibly sound like that and also be load-dependent.

Specifics: about 80-85degF day, coolant temps about 200degF at the end of the runs. Oil temp unknown. Engine runs 24 degrees L+T, was running a fuel mix of about 30% 87 and 70% 93 with 1:128 2-stroke oil thrown in. Mechanical advance is all in before 3000rpm. AFRs were in the 12:1-12;5:1 range the night before. Engine is all GSL-SE, nicely bridge ported on the end housings, mild street port on the primaries, and "my favorite intake" a series 4 N/A port matched to work on a GSL-SE block.

I was hoping that I was being conservative on the timing (this time) and I threw eight gallons of 93 into the tank on my final fuel stop before the event as an extra safety measure. Engine still seems to have good compression, idles very nicely... well it idles the same, at any rate. If anything, the rallycross seems to have helped compression a lot, given that the thing only had about 250 miles on it before the first run.

Or maybe I'm just paranoid.

 

It sounded to me like the exhaust is rattling. I would check for anything loose and by the pictures of some of your past exhaust setups I bet I'm right.
Looks like you had a good time, nice driving.

 

I have had a very similar issue with my motor, a 1/2 bridge ITB. In my case after pulling back the timing and messing about with fueling, we came to the conclusion it was that the plugs were too hot and starting to act as glow plugs. We had similar timing, temps and air temps and it pulled hard until the motor (and engine bay) got warm, then it started to detonate under hard pulls. After checking everything and seeing that all was well we decided to actually talk to a couple of well respected race shops and got some ideas. We are going to use Mazda race plugs this year as the general feeling is that as the car makes more power and is using the bridge setup, under hard pulls the stock plugs just get over heated and turn into little glow plugs until they can get cooled with fuel on the throttle overrun.

What plugs are you using? If you are using stock, you may need to use the race plugs. Its a good place to start before you hurt the motor.

Eric

 

i would treat it like it is detonation, i like the spark plug idea. stock is 7L and 9T, you can go 9L and 11T...

i'd also think about running it a little richer, or maybe it wants slightly less timing?

 

Good point... I'm running FC trailing plugs all around.

I'm already planning on cutting timing back to 20deg and adding a bunch of fuel for the overrun for cooling purposes. The engine wants less timing, driving down the highway at 65mph has the engine brapping happily, which isn't so hot for emissions or fuel economy.

Right now my high vacuum/over 5000rpm bins are at ~40% VE (MS1-basic), think I'll bump those up to ~65 or so. Full load VE bins are right around 100 in the meat of the powerband with the ones surrounding it around 85, and I *just* kiss static on the injectors. I'll double check the AFRs after I get the pinion seal replaced so I can drive the car again, but if I can't add more fuel because the injectors can't cut it, I'm not sure what to do.

The exhaust is actually pretty well engineered, it doesn't go anywhere near anything, still allows transmission R&R without having to touch the exhaust, and it is all slip-fits with band clamps tacked in place. I found that repeated heat cycles make the band clamps lose their tension, thus the tack welds. On that same tip, the driver's side engine mount is chained down to prevent tearing in half.

I just hope I haven't flattened another set of corner seal springs, this engine needs to last until July at least before the next engine is ready to go in.

edit: compression is 85psi front/90psi rear all even, on my piston engine gauge which is a verified 10psi lower than anybody elses' gauges. So, we're doing pretty good for old parts with flaked housings.

 

I just had a thought. I have an old water injection system kicking around, I wonder if that would help any.

 

If it is detonating, then you shouldn't have to use water injection on a N/A motor. check your egt temps and make sure your air/fuel and egt's match and are ok. If that all checks out and you are still detonating, then use a higher heat range and higher quality plug. I have had excellent results with the NGK 6725's or 7420 in the 10.5-11.5 heat range and had no detonation and great power all the way past 10k rpm's. They are pricy though. Just be glad you don't have a v8 or v12 to buy plugs for.

 

A V8 would be kinda nice... you generally don't have to replace the plugs every 3,000mi, you can run an automatic trans (notice how many times I was not in the right gear and wasted time TRYING to downshift? Automatic = bang shifter, in gear, no thinkin' or slowing down required) but there are a lot of other factors that don't really belong in this thread.

I'm probably just going to throw fresh 9's in again, set timing to 19-20 degrees per Racing Beat, make sure it's got a good distributor cap, and make sure the fueling is addressed properly. And cross a lot of fingers.

One other thing I haven't mentioned - sometimes, not every time but maybe half the time, I hear a clicking from the engine as it winds down to a stop. Like apex seals snapping back and forth in their slots, or something.

 

BUE plugs kick *** too. I'm loving mine. $2.50 each for the coldest thing NGK makes. I'd be surprised if it was detonating. I never have even in 110* here in the desert. I'm @27* full advance with mechanical advance still working. run 87 octane always and 1oz per gallon of 2 stroke and my AFR's are near 13:1. Unless your O2 sensor is going and it's leaner than it reads. I know mine is. LOL I just switched to the BUE's, but I've been running Rx8 plugs in the leading and BR9EIX in the trailing for the last few years.

 

i'm sure they all do that. it probably rocks in the stationary gears....

 

I've never heard an engine do this before. It sounds almost like when you get the distributor cap on wrong and the rotor hits the trailing terminals, but it only does it when the engine is winding down and not all the time.

But great, now you have me worried that it's an oiling issue or something. I never bother to look at the oil pressure gauge during a run, but it's still right on 70psi all the time except at hot ~1300rpm idle, where it's 50psi. With Mobil 1 5W30. So, probably good there. I'm never running it over 8000rpm due to the 3mm iron seals, too, so the E-shaft modifications I did are probably overkill...

I put the 8k chip in the MSD and I know I tapped it a couple times, but I'm not leaning on it. (The shift light is damn near invisible in daylight) I was first worried that the noise on shutdown was apex seals flapping around because of rev limiter damage, but this was well before I heard the video. In the car you don't hear very much, mainly exhaust and gear noise.

 

it could be something in the wheels/belts/alternator too...

 

There is that, after all.

Plan of attack:

- External "OMG" shift light to augment the weenie in-tach one
- 22" belt to absolutely, positively ensure that the water pump isn't stalling
- New 9 heat range plugs. The ones in the car may have gunk on the trailings, never actually took them out when I rebuilt the engine, after the engine processed about five or six Block Weld attacks
- Turn timing back to 20deg. Actually did this a couple hours ago... engine seems to pull about the same and definitely cruises better with less timing. Runs a bit cooler, too, was running about 170-175 on the way to my friend's house and about 160 on the way back. (Not what I'd think would happen...) Need to revisit the fuel map in the cruising range, though. Speaking of...
- Add a ton of fuel to the 5000+ rpm overrun sections of the map. I'd like to do this as low as 3000rpm but I cruise on the highway at up to 4500 so I want to avoid excess overfueling, given that this is still kind of my daily driver.

As well as other, differential-related things. Under load, the diff seems to be pulling away from the rearend housing so I'm going to stud it. Also, the replacement pinion seal is leaking almost as badly as the one I burned from clogging it with hay.

 

What is your injector duty in the high RPMs? Are you still just running on GSL-SE injectors? If you are already ready running the S4 manifold, why not use the secondary injectors?

 

i leaned out the Tr3 from too rich to idle to a little lean, and the coolant temps came up too, i've never seen that before!

 

Peejay. You might remember, with my last motor I was experiencing a loud clicking sound, but only when the secondaries opened up. Any other time it sounded normal. She coughed up an apex seal within a few hundred miles.

But you say you are hearing the clicking after you let off, so maybe that's not your issue.

Good luck.


.

 

Either my MS unit has a faulty inj#2 driver or I have three bad sets of FC N/A injectors. Either way, I can't get it to run with four injectors.

Besides, I eliminated the secondary injector ports on my manifold. The fuel rail was interfering with my air filter, preventing it from sealing properly. In addition, now I can remove the intake manifold as one assembly, which means I could permanently seal upper-lower gasket surface to prevent a possible source of vacuum leaks and therefore dust intrusion.

 

With the timing at 20 degrees and AFRs at 12-12.5:1, the car ran 14.8 at 91, hitting the 8000rpm rev limiter for the last 60 feet or so of track thanks to the 4.077 gear (yep, the early build GSL-SE final drive) and the hard as rocks 205/50-15 Direzzas that I got from Fidelity101 that spun hard off the line, spun on the 1-2 shift, and slipped a little on the 2-3 shift.

With a friend in the car.

Hitting 87% duty cycle, which is about 180hp at .6lb/hp/hr BSFC, which also correlates to the ET/MPH considering that my friend was in the car so we were up to nearly 3000lb.

Clearly, I want to add some of the timing back. My 4-port half bridge's ETs and duty cycles correlated more to a .5lb/hp/hr. (I'd also use 8700-9200 as a shift point)

And maybe think about where to pull weight from the car, but I don't see it anywhere.

And build another 2mm seal engine so I don't have to suffer under this low rev limit. I know what I want: I want 300hp from an MFR style peripheral port, since that is what the Group B cars had. I hate to think what that would do for my daily drivability. When the injectors see overlap, fuel consumption goes through the roof.

 

we were talking about this the other night, although it was starter pistol VS starter light.

so it turns out your brain processes sound MUCH faster than it processes visuals. we were talking swimming, but i guess lap times are faster in the pool with the starter pistol vs the lights. the pistol is close enough that the difference in speed of sound vs light is less than the difference of the processing speed in your head.

so you want a buzzer.

 

The redline buzzer is still functional. It's just way too quiet. I can't hear it over the rest of the cacophany. At the dragstrip I can hear it a little, because all I hear is intake and exhaust and drivetrain whine, but on course even that gets drowned out by suspension clunking/banging and the sound of vegetation/dirt/gravel sandblasting the bottom of the car. Really, I kinda shut my hearing off when on course.

The big yellow light should do nicely. I bought a Proform one from Summit for $25 last year, was supposed to go into the VW, but the VW is so slow you can look at the tach, see "oh, 4000rpm", wait a while, change CD, look again, "oh, 4800", make some phone calls, look down again, "hey, 5200!" and then shift. So not necessary. But anyway, it's so cheaply built that if you connect the tach sense wire directly to 12v, it lights up constantly, so it should interface well with the external shift light connector on my tach.

Besides, I want the light to come on well before 8000rpm, like 7200-7300rpm, it's not a shift now light, but more of a start looking at the tach light.

 

Update:

Did another one yesterday. With the shift light, I felt more confident in running the car out more in 1st gear, so I was using a lot more RPM. The format of the runs was unusual, as there was a course roughly 65-70 seconds long that we would have to do two laps in a row. This is a lot trickier than it seems, because you remember the first few corners all wrong when you are approaching at ~45mph instead of ~20mph... So my first run, I spun the second lap. My second run went okay. Both times, coolant temps were hovering around 210-215degF at the end of a run.

Third run, car shuts off about 110 seconds in. I coast off the course, and the car relights by itself. Curse a lot, wait for course to clear out, drive to paddock area and secure distributor wires with zipties and duct tape, since it felt like when my MSD came unplugged one time.

Fourth and final morning run, going good, going strong, car shuts off about 110 seconds in. I keep coasting on-course. About five-ten seconds later, car relights and I finish the run.

Hmm. Hot day + more RPM + running higher duty cycles than normal + much longer runs than I've ever really done with Megasquirt. ECU too hot to touch! I ziptied it to a cooler location than the trans tunnel and finished the day, which had markedly shorter runs.

But coolant temps are still way higher than I would like, and in the afternoon after my second to last run, they were around 220f and would NOT come down until right before starting my final run. The 60-7215 belt I put on is stretched heavily enough that I can easily turn the water pump by hand, so it appears that 22 1/8" is way too long for a water pump drive. I wonder if an FC water pump pulley would be larger enough to take up the difference.

Meanwhile, it's probably time to do quad injectors, and swap to FC style ignition.