I am trying to figure out whether I burned a chip incorrectly, or if my tuning is so out of whack that the car won't run...here are the details:
1992 Camaro w/ 730 ECM
custom 350 engine:
Stealthram intake
36lb/hr injectors (yes, they are too large...)
Isky 272/282 roller cam
Vortec Heads
9.5:1 CR

I am using the stock 305 TPI Manual Tranny bin file as my starting point with the following changes:
Injector flowrate altered for larger injectors
AIR, EGR, and closed loop currently turned off
Slight mods to VE table to add more fuel at higher RPM
that's about it for the tuning mods so far.

And my problem...
It will crank and fire up, but just sits there chugging at around 200rpm. Hitting the gas seems to do almost nothing. Fuel pressure is fine and spark is present on all cylinders...though the distributor has not been dialed in perfectly yet - it is close (can't get a timing light on it with it running so poorly).

I would really like to try and find a "known-good" bin file for something somewhat close to this engine, but I am not sure how to select a good file from the various sources out there. For example, Moates's site has tons of bins, but few explanations as to what mods were present for each tune.

Suggestions?

 

> Isky 272/282 roller cam

Is this at 050 lift? If not, what is the lift at 050 and the LSA/LDA numbers.

Sounds like the lower VE table is too high. The more radical the cam the higher the manifold pressure. And the need for a higher idle speed and usually more spark timing.

Start pulling fuel out of the lower speed VE table until it clears up. Then move on to getting it drivable.

RBob.

 

The other thing to do is to make sure that the ECM is running from the PROM, and not in limp mode.

At key-on, engine-off watch the SES light.

It must: turn on briefly, blink off, then turn on solid. Can repeat the test after 10 seconds or more of key-off.

No blink off, not running from the PROM.

RBob.

 

Thanks a lot RBob. I am definitely suspicious that I may be in limp mode for some reason. I will try the SES test tonight. I am also borrowing a friend's Matco scanner (a "Determinator"...great name) to look at data and datalog. I also tihnk you're right about the MAP value being too high and placing me in an inherantly rich area of the VE. I will move the low RPM high MAP stuff down a bit.
The cam has 112 degree lobe centers and duration is 225/234 degrees at 0.050"
Here's a link to the cam card:
http://iskycams.com/timingchart.php?...ber=201272/282

I am kind of curious if many people have run 36lb injectors on an engine this tame before. Obviously turbo guys must do it (especially the high HP turbo 4's and 6's, which likely use even larger injectors). I am just wondering if I can get it to idle at a reasonable RPM using the stock-based ECM - I have had it running with another engine management system before, and it idled fine at 700 RPM, so I assume it can be done. I guess what I am wondering is if I need to change any other variables in the bin file other than the injector flow rate (i.e. offsets, etc.) to account for injectors this much diferent than stock. Or is just chaning the injector flow rate parameter enough (coupled with a full VE and SA recalibration of course)?

 

I checked it last night and the SES light flashed lke you said, Rbob. So I know it's not in limp mode. Unfortunately, my friend's data scanner only goes back to 1995 vehicles! Sonofa...
Going to try and pul some fuel out later today to see if it will run a bit better.

 

Cam has some overlap but not too bad. If the 36#/hr injectors are the older stle Bosch then the short PW compensation tables will need some work. They tend to open slower then the Multecs used in the stock TPI set ups.

Data logging is the key so you can see where the engine is operating. And what the ECM is doing to keep it running.

RBob.

 

Rbob -
I am using FAST 36lb/hr high impedance injectors. I forget the PN, but I think they're from the 3.8L SC engines...not 100% sure though.

When you say "short PW compensation," are you referring to the "Injector PW Low Offset vs. Base PW?" If so, my current values are all zero above 2.2ms base PW, and they taper from 15 uSec at 1.95mSec BPW to 216 uSec at 0.488 mSec BPW. Assuming my injectors open slower than the Multecs, I would want to make these numbers higher, right?

I seem to remember the Multecs open very quickly (maybe 0.8msec) and the Bosch (pintle) style requires more like 1.0-1.3 msec. Anyone care to confirm this?

I have a Snap-On scanner that I am borrowing, but I feel like an Ostrich may be necessary soon. I am also going to re-confirm my timing value. Since the engine has never been run off the distributor (my last setup was DIS), I have not been able to set the timing with a light just yet.

Thanks again.

 

That is the correct table. This is what I've been using for a set of Bosch injectors from a non-SC 3.8L engine (about 91 MY):

0.00
0.00
15.26
30.52
45.78
61.04
61.04
61.04
76.30
76.30
76.30
91.56
122.08
305.20
488.32
488.32
0.00

Top is the 3.9 msec entry, bottom being the 0 msec entry. The last entry is zero so that a zero PW doesn't get an offset added. I don't recall whether $8D checks first or not.

RBob.

 

Rbob and everyone -

thanks for all the continued help! I got the car running today. My ignition advance was off by more than I thought...it was way negative. Once I dialed it in, it started right up and idled. My problem was that it was so off that I couldn't get it running enough to set the timing without the engine flooding/stalling.

As a tuning technique, I found a great old Super Rod article that did a huge intake manifold comparo. It has a graph of the power curve of the stock TPI against a stealth ram intake with no other engine changes (except for tuning optimization). I am going to use the % differences between the two torque curves to get a good approximation of the VE table changes I need to make.

 

Please share that article. I would love to see it.