Chevelle 2009 projects

[Fred32v]

Now WXO is wondering what the Air Fuel Ratio table for his GTO looks like
and he's thinking he might want to play with it.

[TireSmoker]

I don't know if the OEMs use AFR Target tables in their computers. I can't say for certain, but I don't think they do, at least GM anyway.

LC-1 arrived today from Summit. I wired it up, calibrated it, and it seems to be working as intended. I didn't have time to go for a drive tonight to really try it out. I'm encouraged by what I saw, though.

-Dave

[wxo]

Now WXO is wondering what the Air Fuel Ratio table for his GTO looks like
and he's thinking he might want to play with it.

I've decided to leave that sort of tinkering to the professionals (and 'Smoker).

[TireSmoker]

Tuning Progress

I made some tuning progress today, although it was slow going at first. Today is the first time since Tuesday that I've had some time to play with the car for a few hours. I started driving around and recording datalogs and pumping them through the log analzyer. After 3 iterations, it wasn't running nearly as good as I had hoped. Lots of lean popping, and just not quite right. After some poking around, I had found where I had changed a core value ("req_fuel", the injector constant, has been changed to 16 from 20. when I was messing around in the garage several nights before, and had forgot to change it back. It was, thankfully, set too lean. I changed the value back and the car was instantly running better. I went out and took another datalog, ran it through the analyzer and I finally have something that is fairly nice and driveable.

It's amazing how well things work when they are properly configured!

I've made several laps of the area and no real problems. I think I might drive down to Salem, OH with it tonight to watch some motorcycle racing. That should be a good test.

-Dave

[TireSmoker]

Update:

The best way to sum it up right now is that it runs so good, I need a radio. In other words, it's running great.

When I ended my last message, I was considering going to watch my friend Mike race his motorcycle at a dirt flat track down in Salem. Salem is a little over 60 miles from here. I drove the car there and it made it with no major issues. At this point, the car was running decent, but not great. However, it made the round trip with no real problems. Remember, I haven't driven the car much for a few years.

I picked up a set of 30 lb/hr injectors to replace the 22's I had in there initially. Changing them out was actually very simple. But no job can go smoothly, right? Sometime after starting it up after replacing the injectors, it was smoking kinda funny and idling pretty high. This had really bummed me out, as this was just a day or two after the 120 mile trip. It turns out that one of the plenum gaskets had gotten torn and likely sucked into the engine, hence the smoking. Replaced the gasket, it idled normal and ran good again.

Next up was the trip to TRP. The car had been running good for a couple weeks. VeeDub came over that Saturday morning around 10am and we were ready to go. I reach in to start it -- nothing. Not a click, Nothing at all. ARGH!!! So, we jack up the car, loosen the header and exhaust on the passenger side, remove the starter (a Summit hi-torque mini-starter) and also grab my stock starter from The Basement and head to NAPA. Both starters check out good on the bench. WTF?? We get home and decide to put the stock starter in. I get the starter in -- and now its so tight, it needs shimming. I did a crappy shim job -- they're difficult to get in around the headers and I'm trying to get to the track. It's still ugly sounding. Need to fix that this weekend.

We got to TRP about 1 or 2pm. I managed to get in 3 time runs, with the first one being best at 14.47 @ 95. It seemed like a good start, but I really thought this thing was gonna be in the 13s, or at least running 100mph. I tried making some small tuning changes, but all I did was slow down, running 14.55 and 14.58. At that point, I called it a day. In reality, it was a really good day -- I drove there, I made 3 passes, and drove home with no problems for the first time since June 2008. But I was a little bummed with the times.

Last Friday, VeeDub, his GF Molly, and I rode around in the car for probably a few hours, recording datalogs, running them through the VE Analyzer. No problems.

I was still having a problem with a stumble on tip-in. In the datalog, You could see the vacuum dropping super low on just a slight throttle opening, then slightly recovering. It was causing a bog. I'm talking like within the first 5% of throttle movement. So tonight, I decided to remove the Holley 58mm throttle body and replace it with a Chevy 48mm unit -- much better throttle response. No more stumble.

At this point, I'm really glad I've stuck it out with the EFI. It's really running nice, I haven't gotten a drop of gas on my hands while tuning it, and I haven't touched any of the hardware or wiring for a few weeks now. I'm thinking it might be time to put it all back up under the dash. And it looks awesome when I open the hood.

And then put in a radio. And drive it more. I'll post some video soon.

-Dave

[TireSmoker]

Argh, this rain is killing me. I'm working from home today and was hoping for a break in the weather to take a quick drive to make a quick video. I finally just went for one anyway. No real good WOT spots, but it just drives real nice.

[youtube]http://www.youtube.com/watch?v=cW1vlI2_taI[/youtube]

Here's the 14.47 pass.

[youtube]http://www.youtube.com/watch?v=UQY8IIkCyjs[/youtube]

[TireSmoker]

This is another short clip. A little better audio, but the road was still damp. I thought I recorded a lot more, but the camera card filled up before my good WOT runs. Bummer, I'll just have to do it again.

-Dave


[youtube]http://www.youtube.com/watch?v=gSUOdxgBZuA[/youtube]

[ttamrettus]

Dave, nice work. I love it.

[TireSmoker]

Minor frustrations continue...

I was on my way to a test-n-tune at Dragway 42 last Friday. I had the tune dialed in pretty good, I thought. I was hoping for an improvement from 14.47 @ 95. I drove the car to work downtown that day. Ran good in the morning, topped off with 92 octane on the way to work. I got caught in a bunch of stop-n-go on I-71 in the evening, but the car ran fine. After I got some clear road, I went to put my fut in it and it started completely falling on its face. UGGGH... what now. Car ran absolutely fine at anything less than 1/2 throttle or so. Fired up the laptop and saw it go lean as I'd get into it. At the 71/76 interchange, I reloaded a known-good tune into the computer, just as a precaution. No difference.

This reminds me of a few years ago when I had a fuel pump that was on its way out -- it registered enough pressure under low-load situations, but under high-load, pressure would drop significantly. Markss327 and I figured it out when we raised the hood and did a burnout, watching the pressure gauge. (I have a video of this somewhere).

So I let the car cool down at 42 for a while. Tried having my friend Ken watch the pressure gauge as I tried to do a burnout at the very rear of staging. From his description, the pressure wasnt dropping much. And it was spinning the tires. I didn't wanna be That Guy and do a huge burnout in the staging lanes. With a poorly running 14-second car. I made one run, but it was junk.

After that, I was just hoping that it would make it home. And it did! It continued to run great at idle/part throttle. So, it's not dead, just reduced functionality at the moment. It still fulfills its most important function of being able to move in/out of the garage under its own power.

So, fuel pump? filter? Pump doesnt seem to sound much different. We'll see.

-Dave

[markss327]

Any updates?
I DO remember that little event - of gauge watching - car in gear, 4000 rpm, hood up, and peering at a tiny fuel psi gauge....

[TireSmoker]

Not really. I haven't fixed anything on the car yet. On the other hand, it is not running anywhere near as bad as it was on that drive and that night at 42. It continues to start and drive around fine. The only troubles I've been having is that you can tell its starviing for fuel a little bit at the top end, and I believe the issue lies with the pump. We need to do another burnout test.

At this point of the year, I'm not interested in taking it apart just yet. I'll wait till the snow flies.

-Dave

[TireSmoker]

So the car continues to run pretty much flawlessly, except for an un-predictable WOT. It has yet to really run bad like it did that night at 42, though. Sometimes I can run it through first gear, and it runs *strong*. I've been able to just jump in and drive it, and it hasn't let me down or acted weird or anything. I keep waiting for something to go wrong. But it doesn't. I'm loving that,

I have a new fuel setup in the works. A while back, i bought an in-tank pump from the Summit bargain bin for $50. It's for a 96-97 Cobra mustang, so it should be decent capacity. I'm making a surge tank that mounts in the engine compartment, and will be fed by old mechanical fuel pump. The in-tank pump will be mounted inside the surge tank. The tank is big enough that the mech, pump could stop supplying fuel and the tank will have enough fuel for at least 6-7 seconds of fuel (at WOT) before running out. Mechanical pumps dont care if they suck a little air, and quickly re-prime when the pickup is re-submerged in fuel. This will let me go back to a stock (non-sump) tank. I scored one cheap off craigslist a few weeks ago, $10!

What this means in the real world, is that when I go around a corner (or launch at the strip, or on the street, or take an on-ramp aggressively, etc) and there's less than a 1/3 or 1/4 tank, the fuel can slosh away from the pickup in the tank, causing a momentary loss of power, and worse, damaging the EFI pump. They're really delicate in this regard, I don't know why. I've ruined 2 pumps already, and the 3rd is on the way out, I think. The new setup should keep the pump submerged 100% of the time, unless the car actually runs completely out of gas.

But this is also my final effort -- if this does not work in a satisfactory fashion, I might just be done with the EFI. If I can't fuel it consistently, there's no point. It's not for lack of effort.

-Dave

[TireSmoker]

I should probably start a new thread or update the title or something...

So, The Tiresmoker started 2011 the same way 2010 ended. Tony's motor with my EFI, running sweet once it had a little temperature in it. *Very* driveable and nice, except for heavy throttle, which was still trouble. But I drove the car a few months like this and enjoyed it. But for a variety of reasons, the EFI era is over for the time being. It's not forever, but at least for right now. This weekend, I switched back to a carb setup.

A Tale of Two Carbs:

When this motor was purchased, it was complete from intake to oil pan. No carb, no distributor. Tony picked a new HEI from Summit, and later found a Holley 770 Street Avenger on craigslist for $200 -- half-price. It looks like brand new after a light clean up on the outside, and is otherwise out-of-the-box stock. When I first got the car running, it didn't run very good at all. Ran lazy like it wasnt getting fuel, and some popping through the carb, like it was lean. Something was wrong, and I assumed it to be the carb. The previous owner had admitted that it never ran the way he expected it to on his engine. I had my recently acquired Edelbrock 750 sitting there too. We bolted it on, and it was a little better, but still no where near right. The engine felt lazy and was still popping. After it showed similar symptoms with 2 different carbs, I decided it must be an ignition problem.

This 350 is a '92 bottom end. It was designed for computer control, so its timing pointer is basically 0, +4 and -4. It's also located at 12-o-clock, and its difficult to see. We added a timing tape to the balancer and just use the 0 mark now. The engine has a second timing pointer for an older style small block where TDC is at like 2-o-clock. This is what I had timed the engine with originally, so it was very retarded. DOH! I ran into this when I did the EFI and had forgotten about it. Once I remembered and re-timed it on the correct pointer, it ran muuuuch better. Note to self: remove the incorrect pointer.

The Edelbrock 750 is still on there, and after the timing was resolved, it starts right up, it idles well, and it'll pull strong to 6000 RPM now! I've been reading up on these carbs and they seem pretty easy (and un-messy) to tune. I might play with it a little bit to see what improvements I can make with minimal effort. With the $10 accelerator pump, $10 hard-feed-line, and $18 fuel pressure gauge, I replaced, I now have $68 in this carb. I very much like that they can be adjusted without spilling fuel all over the place.

I do want to get the Holley back on there soon. It's actually very easy to swap between the two carbs; it can be done in about 5-10 minutes. I want to get it sorted it out for Tony, since he's been nice enough to let me keep his motor all summer. Seems like a fair trade!

I also changed gas tanks when I did the carb swap. As mentioned earlier, I had found a gas tank for $10 on craigslist a while back. I think it actually came from a Pontiac Tempest. Well, the filler neck is slightly too long, pushing my license plate a little 'open'. Annoying. Don't wanna go back to the old tank. Sump is ugly, and I've had nothing but problems relating to it for the past few years. It'll either be sold or thrown out.

[TireSmoker]

So after a long weekend of playing with carbs, I remember why I went to EFI in the first place. After getting the timing sorted out, including putting the lightweight springs in the distributor, I've had two different carbs on the motor, both with their stock calibrations. And neither really run very good. Admittedly, they are both used carbs. I opened/cleaned/inspected the Edelbrock 750, but didnt do a rebuild because I didn't have the kit at the time. I have since replaced the accelerator pump plunger and the needles/seats, though. Tony's Holley 770 appeared to be in like-new condition, and after having the primary fuel bowl off, it seemed clean inside. I have my old Holley 750, freshly rebuilt, also waiting on the shelf.

I even plumbed in a fuel pressure regulator, something I've never used with a carb before. At initial fire-up, it showed 5psi. Edelbrock recommends 5.5 psi, but I'm not gonna quibble over a 1/2-psi. Not sure what Holley recommends, but I'm pretty sure I'm in the acceptable range. Before the regulator install, I was seeing 8-9 psi, a little much.

I guess I had gotten a little emboldened with the ease of success I had with the Edelbrock 600 on the Corvette. I literally bolted that one on out of the box, set the idle mixture, and it has run great. I was figuring that after spending a bunch of time refreshing myself on their operation and adjustments, that it should be relatively simple to bolt them on and go. Sadly, that hasn't been the case.

They both will start and idle, and I can run them at WOT after getting past the inital bogs/stumbles/poor part-throttle and they both pull to 5500+ RPM.

The one obvious thing I have not done yet is to wire up a read-out gauge for my wide-band oxygen sensor. It can operate independently of my EFI computer. That should help me out a bit.

-Dave

[MostMint]

Most of the time this problem comes from not enough fuel dumped in to overcome the "stall" in the air when you open the butterfly in the carb. The way to fix this is install a more aggressive accelerator pump cam and/or a larger shooter nozzle to et more fuel in faster to compensate.

I know nothing about the Edelbrock but on a Holley these are easy changes. I assume also that your accelerator pump cams are adjusted properly. You'll need the chart that shows which cam is the best (they are color coded) and you'll need to know your current shooter size. I bought a box of parts from Holley that has the cams and the shooters a ways back. I looked in it tonight and it appears I gave you several shooter sizes a while back (I left a note for myself). Maybe you still have them and can remember where they are?