Any FI experts here?

[John Milmont]

Just fired my sbc from a fresh build with a megasquirt 2 efi system and got it to run, but had to use the gas peddle to keep it going. I'm trying to get it to idle properly but I'm having a lot of trouble and don't understand whats going on.

As this is the first time the engine has been run, the ignition was not set. As soon as we got it going, we set the timing the best we could but since its not running right, its not perfect.

I have a wideband o2 sensor hooked up - I'm not sure if its reading accurately. It was saying the engine was running extremely lean, something like 20:1, but when I kept adding fuel to the various cells, it didn't seem to run any better and the engine would die before I could get down to 14.7:1.

It seems like the engine wants to idle at a very low RPM, so i thought the timing needed to be advanced more. We kept advancing the timing and it seemed to run better, but it was getting so advanced that I was getting worried - the timing (base timing here, the electronic advance is disabled) was so advanced it was off the indicator...

Another concern I have is that the engine doesn't seem to pull any vacuum. I think mostly this is because I have the throttle open and its running at such a low RPM, but I'm not sure. This is really messing up my fuel map since its picking cells at such a high kPa...

Anyone have any tips to get this thing idling? What am i doing wrong?

 

[Randy V]

What are you using for a system in general (ie -stacks, single throttle body, etc..)
Most throttle body systems need an IAC (idle air controller), and yours may be out of adjustment.
Also, there is the TPS adjustment to be concerned with in order to get things cleaned up.

Timing - all engines like a lot of initial advance at an idle. That will raise RPM and vacuum. Think about how an old engine with vacuum advance responds. Pull the hose off of the vac advance diaphragm and the engine RPM decreases and throttle response is lazt. Now plug it back in again and notice how the engine picks up rpm, smoothens out and becomes far more responsive..

 

[John Milmont]

Its a plenum style intake with a single throttle body. Port injection.

It does have a GM style IAC which is always on. I have tried playing with that and havn't noticed any difference. I set it to zero which should close it off, and even put a finger over the hole where it draws air from just to see if that makes a difference.

I don't think the IAC is really doing anything yet because the throttle is not closed.


My biggest question is how am i running the engine at 800rpm @ something like 90kPa
I'm wondering if there is some vac leak im missing somewhere.

 

[John]

John, it definitly sounds to me like a vacume leak somewhere, a little trick shown to me years ago to find said vacume leaks, run over all posible spots with a can of CRC and spray a bit every where, and if the rpm rises when you spray in a particular spot bingo, theres your leak. hope it helps
cheers John

 

[Tom]

John,
Send me your latest .msq file and I'll take a look at your settings and baseline table. Are you making the adjustments to the AFR table or VE table? Did you follow the initial setup directions for timing, fuel pressure, etc? So much to discuss here not knowing what you've done or not done so far but I'll wait till I hear more about your settings.

 

[John Milmont]

Hey guys, I have had some limited success. I can now get the car to start without any help from the gas pedal. But, I can only get it to run for about 10 seconds and the vacuum is still low. When it does run, it turns about 500 rpm and nothing I do seems to change it. I have tried giving it more and less fuel; I have opened and closed the IAC, nothing seems to make a difference. I can at least hear it sucking more air when i open the IAC, so i at least know thats working.

It seems like there's a vac leak, but i have checked everything and cant find anything. There really isn't a whole lot of vac lines to check...

My wideband is still saying in running really lean, like 18:1. When i starting increasing the fuel in the afterstart enrichment or the warmup, i can bring it down a little but usually stall the engine which ends up flooding it. I cant get anywhere near 14.7...

The engine needs to warm up before it uses the VE table, and i haven't been able to get it warm yet.

I haven't played with the AFR table, but I think i should at least be able to get it running as is...

I have included my MSQ file, please disregard the cranking pulse widths since I have that set low to clear a flood.

I'm beginning to think that something else is wrong. I'm a little suspicious of the ignition. I have had the electronic spark control (ESC) disconnected so far which allows me to set the base timing. I noticed today that I had no spark at all with the ESC connected.

 

[Ian Anderson]

What pressure are you running your fuel at? And have you got a gauge onit to make sure you are getting said pressure?

Ian

 

[John Milmont]

What pressure are you running your fuel at? And have you got a gauge onit to make sure you are getting said pressure?

Ian

I haven't put a gauge on it yet. I will do that since I'm now looking for problems.

 

[Tom]

John,
I just downloaded your .msq file and took a look. I have found a few problem areas that you need to correct. Yes, eveything points to lean settings right off the bat. I'll send you a PM with my phone number so I can walk you through the settings when you're ready.

Before we start, please confirm you have 350 cubic inches, 30 lb injectors, and fuel pressure is set to 3 bar (44psi). In the meantime, I highly recommend you purchase VE Analyze Live! It's a great tool to use and you will save countless hours of tuning once we have the baseline settings corrected.

PM on its way!

Tom

 

[John Milmont]

Tom,

The engine is a 383 stroker with 37# injectors from racetronix. I'm running a converted LT-1 intake manifold and my cam specs are 230/236 with .576/.571 lift measured at the valve.

I got your PM, I will give you a call later today.

Thanks,
John

 

[John Milmont]

Well, I fired the engine again last night and got a little better idle with some help form Tom, but only marginally. I found that I had to change some of the wiring to get the electronic control of the ignition to work. The information and documentation for the megasquirt has been disappointing and I believe has actually set me back in some regard. I have found contradictions in some of the documentation and other information that just doesn't seem to be true at all. The megasquirt is a good system, I just wish the information was organized better.

I got the engine running at about 1000rpm now, but it still is reporting that its very lean and its running choppy as hell. I found I had to advance the timing quite a bit to get it to run better, but its still stalling out whenever I give it fuel. It does't seem to make any sense.

 

[John Milmont]

So I got it running pretty good now. Turns out the timing was everything, and the engine needed a lot more than I had set.

 

[Tom]

John,
Good news. Looks like you figured out your ignition table and advance settings.

Now get the VE Analyze add-on and let it auto-tune your fuel tables. You can fine tune from there, then find a dyno to finish tuning your WOT settings.

Good luck!

Tom

 

[John Milmont]

Progress:
http://youtu.be/ga4dFytnR3I

 

[Ken Roberts]

I've had some past experience with the LT1 converted intakes. I believe from memory that Felpro 1205 gaskets wouldn't seal to the heads. If this is what you are using and still experiencing problems than it might be an avenue to explore. The biggest gasket that would seal the heads to the intake is a Felpro 1204. Anything larger and you risk vacuum leaks at the gasket.