I thought you guys might like to see what TBI can do. All the BS about air flow limited has been answered, the holley 670 flows a lot of air.
Here is the data, if you do the math the 0-60mph is under 4.8 seconds. This is on 245/50-16 All season tires, hehe. I can't wait to get to the track, I'm going Tuesday even if I have to push the car down the track! I did some runs from 50-110mph on the highway and let's just say that the times in my sig are about to change. This might sound like bench racing but look at my total SA and you'll see I have room for improvement. Oh, this is on a full tank of 87 octane. Soon to have wideband data, been too busy with school and Formula SAE.

 

Just as a point of interest, VE drops while MAP stays the same at the higher RPM. Can you run this on a bench and study what the PWs are doing there?. If the WB stays steady thru there maybe no issue, but sumthin to look at.

Might be surprised by what SA makes it happy.
Looks good other wise.

 

I'm looking forward to hearing your results!

Will you be running out at National Trail?

 

Sweet! What's your build?

-Rippin

 

I'll be running at Dragway 42, national trails is closed for the rest of the season.
My car in a nutshell: 91 RS, 330hp gmpp crate motor (350 4-bolt, vortec heads, 212/222 .435/.460 lift), RPM intake, Holley 670 TBI, walbro 255, stock 4L60 with SLP shift kit, 3.73s, torsen SLP take-off, centerline 16x8 wheels w/245/50-16 pirelli p-zero nero all seasons, 36/24 sway bars, 3 point STB, LCA brackets, Hotchkis LCAs, SLP boxed panhard bar, Alston SFCs, Eibach pro, Bilstien HD, 3" cowl, no cat, no a/c, everything else is stock except stereo.
Stock GM 8746 ecm, stock HEI, coil, wiring. It's your basic performance upgrades all on a budget. Oh, almost forgot, waterpump is a Stewards stage 2.
Forgot... SLP tri-y headers with Borla adjustable exhaust.

 

I have the second VE table dropping VE as engine speed increases past peak torque. This is normal and all in the calibration.

 

I'm curious as to what ign parts you are running. I've noticed more fluxuations in RPM just like yours (mine are the same) with a factory setup that shouldn't be falling off until the upper RPM ranges. Thanks

 

The majority of the fluctuations are because of jitter in the ECM counters. These counters are used for both the RPM & MPH inputs. This causes the counts to vary even though the RPM/MPH may in reality not have changed.

[edit: Jon, and nice acceleration]

RBob.

 

Would these jitters cause actual RPM fluctuations you can feel?

Would sometimes you'd feel them, and other times not?

Wondering if my 8747 is causing this, as I think its scaling runs out around 4800.

 

I don't think that it would be something you could feel. But under unusual circumstances it may. This is why: the jitter in the RPM is only going to affect the table lookups. The engine speed is not actually changing, just the ECMs view of it.

So if you have a low resolution table with a large change between rows, then the ECM may be commanding a large change due to the jitter. This is as it bounces between several RPM values the looked-up values will be far apart. Thing is, which table/tables can cause this to the degree that it can make a difference in how the engine runs.

I don't know. I worried about it for a while, did a study of what was causing the jitter, even tried some modifications to the clock circuitry. Concluded that it was in how the chips were designed and operated. In the end I just stopped worrying about it.

RBob.

 

Could different gearing and or tire sizing amplify this problem?

 

I'm using the stock HEI with stock coil and .035 gapped spark plugs, cheapest spark plugs I could find .
I'm running 9.1:1 compression and these heads have excellent plug position so what's the point of upgrading? I will install a hotter "standard" cylinder coil for comparison tests. I just drove home to NJ last night, 22mpg again, I love it. Oh, these tires rock. Never buy Kumho... EVER!!!
I'll post a full 1/4 mile data later. I NEED to get my wideband installed Tuesday morning.

 

The primary advantage of upgrading an ignition is to raise the reserve capacity. If you never have a problem, and it works for you then the HEI is fine. Run a lil lean, and when the stock fails, the upgraded one will march right along. And if the AE isn't correct you can have a tip-in sag that's from being lean and running out of ign..

Good ignition systems are like insurance.
Seems like a waste of money, until you need it.

 

That's how I feel. But even tip in is great although it is very picky. If I'm off a little on the tune it'll let me know right away with throttle response. I have to change the retard and advance SA rates still. Those are stock and I think they are responsible for some of the tuning issues. I always figured that a "hotter" coil is more for larger gap spark plugs or higher compression engines. CDI is a great upgrade for a motor with more compression and crappy combustion chambers and/or a high reving lightweight.
I figure a hotter coil is next, then it's straight for the FAST eDist with CNP!

 

CDI exchanges fast rise time for holding current.
For 12,000 RPM engines you have to run it, since you run out of time to properly charge a single coil. Actually with a single coil, 8 Cyl, and over 6,000 RPM your out of proper dwell time to charge a single coil.

The multi strike CDIs are great for alternative fuels and sloppy rich idles.

Ya eDist rocks..
Not even worth playing with anything other then coil near plug.

 

The best bang-for-the-buck (didn't I already use that recently?) is one of the $17 Made in USA oil filled canister coils from Jegs or Summit.

The difference was such that I had to go back to the epoxy coil just to prove that it wasn't a placebo effect. And it wasn't. Try it out.

RBob.

 

Gotta watch it thou, the oil filled one's are made for firewall mounting, and don't take vibration well.
Epoxy is for on engine apps.

Firewall apps., kill coil wires rather quickly compared to on engine ones.

 

I have one of those accel "yellow" coils that a friend gave me. I'm in the process of doing the swap so see if it'll help me out at low engine speeds. I'll notice that other than the blue moon ecm hickup, the car can and will stumble right off idle about once every few days at a stoplight while in closed loop. It's really odd and hard to datalog because it doesn't happen frequently enough to run lockers.
Soon I will have thermocouples in the headers to do extensive fine tuning. I'm going to do the wideband and EGTs all at once. This will kick my incentive to do my best with what I've got. It's amazing being in complete control over a computer that is in complete control of something so powerful, it's like being a REAL GM engineer, hehe.

 

If it doesn't have Made in USA on it carry a spare coil & ignition module. . .

RBob.

 

Born in the USA, born in the USA..... (the boss, bruce, no not you Grumpy, the other bruce)

 

Now, I'm crushed.
Here I thought I was Boss.
LOL
Oh well, back to the cave.........

Maybe I should take offense to being called, Not Boss,
Thou maybe I should be used to that by now................





Now I wonder how many people with misunderstand that....

Oops had to reedit, I had toooo many smiles.......