Hello,

Just got my car running with a BS3 setup. Basically, my combo is a renegade setup with a slightly bigger cam and a bigger blower (Procharger D2-r with cog). Only made 4 passes so tune isn't even close, but so far here is what I have. Car launches hard (1.34 60 so far), but breaks up going down the track (all gears and pretty much feels like it is tied to a tree). I let off before the 1/8 and went 6.20 @ 109 and 10.86 at 90. #ad


I'm seeing 20 psi of boost with 20 degrees of timing and 10.0 - 10.5 air/fuel. This is at 6800-7000. I realize I need to fine tune these to realize more out of the combo, but I'm perplexed by the breaking up problem. The big thing I see from the logs is huge rpm spikes throughout the run (where it is acting up). I have the crk and cam shield grounds both grounded at the same location and have a .070 gap on the sensor.

The car was pig rich and somewhat fouled the plugs (NGK 10's gapped at .030) at idle. I'm wondering if the plugs are the issue here. Either way, I need to get more time at the track or dyno to sort it out. Just looking for some ideas. Thanks.

BTW, I'm using a crank trigger and cam sensor setup (in distr) with a MSD 6AL.

 

Are you sure those spikes are on the RPM line and not the A/F ratio line? I know that misfires will show up as lean spikes on the A/F. What is the rev limit in the BS3 software set at? What is the rev limit set for on the MSD box?

If the spikes are indeed on the RPM line, I would say this would indicate a rotor phasing problem (spark jumping from rotor to wrong post on dist cap). I had a phasing issue before, and I do seem to recall seeing weird spikes on the rpm graph. I also noticed the tach jumping around. Try setting your timing down to 20 deg. at about 3000 rpm and very low load. Rev the car in park until you get it to run 20 deg total and watch to see if the tach jumps around.

Rob

 

No definitely the rpm line. The rev limit is set up over 9000 rpm in the BS3. I only had a 7000 pill for the MSD (which I kept hitting) so I pulled it out that day.

I have the rotor phased at 20. I can certainly do your ck and see what happens though. That would be sweet if that is all it is... 8)

 

That is a lot of boost for a 6AL and an 0.030 gap. I would get a fresh set of plugs and pull them in to 0.025 or even 0.020 or so. You might also go with 9's to keep them from fouling until you get the tune a little closer. I would also ohm check all of your wires and rotor phase for good measure. I would also aim for a bit leaner A/F ratio.

-Chris

 

:withu:

I concur with everything said above. That's a lot of airflow and cylinder pressure for a 6AL. Plus, being that rich makes it harder to light off the mixture too. My guess is you replace it with a digital 6 or digital 7 and good coil, lean it out, and this all goes away. and yes, -10 plugs are too cold. If you were running 30psi and 8500 rpm I'd say -10s. But not where you are now.

 

If you are seeing RPM spikes I would look at the crank sensor. Do you have it wired Red to Green? Are there any marks on the wheel or the sensor, basically, has the sensor ever touched down on the wheel? 0.072" gap is a good start. Do you have an alternator near the crank sensor or its wire? You do know the Cam Sync and Crank Sync ground MUST be to the same ground point.

 

If indeed you are seeing spikes on the RPM trace, then Don is right in telling you to look into crank sensor issues. Garbage in = Garbage out. I cringe every time I see stuff like crank trigger wires zip tied to electric water pump wires, etc. I always recommend running a shielded crank trigger harness and keeping it as far as possible away from wiring carrying anything more than a very slight amount of current.

-Chris
www.mtpturbo.com

 

If he were misfiring (too fat, gap too large) and/or hitting the limiter, wouldn't it show up as spikes on the A/F line?

Rob

 

Yes, and the misfires show as lean spikes. What I am concerned with is this. The engine will not gain RPM as fast as a spike can occur. So if the engine isn't performing well, especially if it isn't tuned well, it wont gain 500 RPM like a spike may show and then settle back down to a normal RPM. So then I would investigate the crank sensor and the like as I described above.

 

Thanks for verifying Don.

Rob

 

mine has, and it pretty much took of about .040 of the front off the end of the sensor. it seems to work just fine though. should i replace it??

 

Hell, I thought .030 was fairly conservative too---LOL! I am going to go to 9's. I thought this would be making 30 psi or in that range, but it isn't even close. When I max the blower out, I bet I'll be in the 25 psi range. Wires, etc are good though. I'll get the 9's, do some more tweaking on the tune and see what happens. Thanks.

 

Thanks Shane---will do.

 

No marks on the sensor and it is brand new. It is a smith systems sensor (blue and white wire). I called Smith Systems and he told me that the blue wire should be wired to the red wire (pin A) on the BS3 harness. NOTE: Early on, I tried wiring it both ways and I showed cranking rpm with the sensor wired either way.

My gap is .070. Both cam and crk grounds are at the same location too. I was concerned about the alternator too, so I made sure to keep the harness away from that the best that I could. I can tell you that both harnesses run along side the water pump harness though (right side of intake manifold).

Where the crank sensor harness comes out (it points toward the alternator). I looped it around (gently) and back towards the water pump/crank sensor brackets. It probably comes 2 - 3" from the alternator there. That is the closest.

I have considered wrapping the harness in tin foil and ground it, but I thought I was being extreme or paranoid. What about twisting the wires together?

One other thing, my datalogs don't show the spikes until I'm off the t-brake and converter has flashed. Basically, when I'm under power and moving and the rpms are climbing is where I get the spikes. Some of the spikes go up, some down. The ones that go down stop at the 4000 rpm range (my 2 step is at 4000). There is nothing on the log that correlates to the spikes (tp glitching prior to spike, air fuel changes prior to spike, etc)....

 

Thanks! That may be all it is (water pump harness, etc)... The only time I see it is under heavy load as the car starts to go through the gear in 5000rpm range on up. This happens in every gear too.

 

Yep, some of these spikes are 2000 or 3000 rpm!!! I wish this engine accelerated that hard!

 

Last thing---How the hell do I reply to multiple people at once rather then posting up 50 replies? Also, how do I get this to notify me when a reply is posted? Thanks guys for all of the help!

I can't believe how easy this system is to use. At least with the support of knowledgeable people like yourselves. Thanks and take care.

 

Any comments? Thanks.

 

Here are some pics of the log file. The 2nd one is just zoomed in on the rpm in 3rd gear. It looks like I'm letting up on the throttle on the launch/1st gear, but in 3rd it is pretty steady. Not sure what's going on with the rpm....

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Have you followed thru on any of the suggestions yet?

Rob