Hi all. I went to New England Dragway yesterday (April 5th) with my 93 Caprice 9C1 with the TBI L05. I knew my performance was down compared to previous drag runs, but I wanted to quantify it. For the record, the car has run a best of 15.86 @ 84.87mph at this dragstrip, in warmer weather. This was with no muffler and a K&N drop-in filter. Everything else was stock, 235/70 15 tires. And to be honest, neither of those "mods" made any difference, SOTP.
Last night's best run was a 16.357 @ 84.23mph with 145k on the car. You might be saying "that's not so bad, just had a bad launch." Normally, I'd agree. The only problem with this logic is that I've gutted the cat and done a custom air intake with big PVC pipe and a K&N cone filter since then. BIG SOTP gains with gutting the cat (clogged). The car felt a lot stronger for a few months, torque and HP wise. Then I started getting weird push-pull action at higher rpms (usually 4000+). I decided to put in the classic quarter mod into my fuel pressure regulator. This worsened the problems at high rpm, making me think increasing pressure placed an extra demand on my fuel pump, such that it couldn't keep up with volume. Solution from that logic? New fuel pump, which I haven't done yet. Don't have the funds at the moment, so all I can do is bench-diagnose or maybe cheap stuff, like fuel filter.

Anyway, I e-mailed Ken Rolt with my thoughts on the drag ordeal last night, and I was going to paste it in here, or at least relevant excepts.

Anyway, my top end probems reared their ugly head during the runs. I could actually feel that it was going to be a bad run. Besides the fact that traction last night was terrible for everyone (my best 60' was 2.451), my MPH were bad. I also did a data capture during the 2nd run and I don't think it revealed anything terribly interesting.
During the runs, especially the first two (I ran 3), it was hanging up at the top of 2nd. It was so bad, I thought it was my tranny that was shifting late, but I looked down and saw that the MPH were normal, it was just that the engine was totally out of breath. When it finally shifted into 3rd, it was very positive and a huge rush of power. Hence my bad MPH (considering all the air-flow mods it has). I tried decreasing tire pressure, I put the right rear at 26psi and left the drivers side alone, but that didn't affect 60' at all. That's how bad traction was...

I did a data capture during the 2nd of three runs and will present that data upon request (this is already long enough) but I don't know if it's helpful at all. I can say that there were 10 counts of knock (should it be zero?) and BLMs were 133 (during the runs). I think it just locks into the previous BLM (which was an idle). I don't think it can change during WOT...so that may not even be relevant. The O2 data was kind of odd. The 1-2 gear range is fine, but around the 2-3 shift it gets weird. This confirms what I felt in the car. My plan is still coil, plugs, fuel filter, fuel pressure reading, as soon as I get some funds.

Other pieces of evidence:
After the runs, my BL values were around 145, which means the ECU was widening the injector pulse width to counter for what I think is a lean situation (fuel pump). On my way home after the event, I noticed the car began running much better, inexplicably. It had really nice torque (to make passes on the highway in 4th, TCC locked) and also midrange and top end (though the tip-top end, 4800+, was still nothing). It was quite pleasant...I just don't understand why it would seemingly "switch" to this running condition. I don't think it's in my head. Does this suggest fuel pump? What I really need is to hook up a fuel pressure guage and get a reading at idle then WOT + high rpm. That would answer my fuel pump question I think.

What do you all think (if you've read this far)?

Thanks in advance,
Kevin Moore
93 9C1

 

hey Kevin,
Sorry I missed you guys last night. I saw Bill and he filled me in on your night. He gave me a ride today to get my car out of storage.
Fuel pump is a possibility but not a strong possibility. Definitely check the pressure at WOT before replacing. I have a TBI pressure test set up if you're interested in coming up here. The extra pressure from the quarter mod should not have any affect on your pump. I'm not sure why it should run worse at RPM though with slightly more pressure. Filter would be a cheap step to take to eliminate a likely cause. Check lines for kinks while your at it.
I'm going to install my LCAs and do the Caddy intake box, sewer pipe and K&N this month. Maybe we can interest KR in a mod day at his house. He's between us.

 

I'm requestiong the data you captured.
It definatly sounds like one of 2 things...either a fuel problem and I can already tell you that a BLM of 133 isn't good. You might want to check your plug wires and spark plugs. If a wire starts to arc to the header/engine or you've got a bad plug you'll get funky engine running problems that seem to go away when you fiddly under the hood.
Definatly post the log file, I'd like to take a look at it.

 

I didn't use a laptop, just an XP240 and I wrote down the relevant data in a notebook. RPM, speed, O2 voltage is all I have.
MPH RPM O2 (mV)
21 3625 910
21 3625 910
31 4475 915
38 3150 963
45 3675 963
45 3675 910
53 4050 985
59 4475 888
64 3375 888
64 3375 924
68 3375 805
73 3525 928
73 3525 928

And like I said, BLMs were 133 during the duration of the run. Sometimes it locks back into 128 during WOT blasts on the highway, but will resume 135-139 during cruise. The other thing is, the data looks funny. MPHs, RPMs and O2 values repeat themselves and stuff doesn't always line up right. Is this due to the slow ALDL line or what?

Like I said in the original post, right after the run, while driving to pick up my time slip, BLMs were 145, which is quite high. Remember, gutted cat, no muffler and custom intake, or is this still too much block learn for those mods? Isn't this indicative of a fuel supply problem?

 

Yeah, BLMs above 128 is a fuel problem but it can also be a timing issue. If the timing is way out of wack a lot of oxygen can get passed through the engine and into the o2 sensor. This would show a lean condition and the car would dump major amounts of fuel in to compensate hence some knock and the car retards lots of timing. This all adds up to major complications. If it smells rich and the cars BLMs are still above 128 then you might want to look for an exhaust leak before the o2 sensor and make sure spark/timing is setup correctly.
A fuel delivery problem can also cause the problems. Try cranking the fuel pressure up and try and get the BLMs to be around 128 when you're cruising down the highway in drive, not overdrive.

 

What dictates whether the BLMs will be 128 or otherwise during a WOT run? I have seen mine sit at 128 but also higher. And I have NEVER seen them change during a WOT run, only afterwards.
When I put the $0.25 mod in, I did notice lower BLMs across the board, but I had that top end push-pull problem, so I took the $0.25 out, and despite higher BLMs, it runs better.

 

sorry to but in but this sounds interesting.. I'm trying to understand all this data.. so your saying in general when at a cruising speed(steady) the blm's should show 128??

I know with winaldl it creates a table of different blm for rpms

 

No, at cruising, my BLMs are anywhere from 133-139, depending on RPMs and throttle position.