No Start Problem on 492 LSX

[Asteroid]

The engine is a NA 492 cid LSX tall deck installed in a Comp Jet race boat. It has a Wilson Dominator mechanical T/B and Siemans 60# injectors (69# at 58psi). Cam is 258/270. Compression ratio is 14:1. Fuel is Sunoco 110. PCM is a #411 F-body unit. This is an SD tune.

It has been very hard to start, but once running everything runs fine. It cranks and cranks and belches flames out the headers. Sometimes it will start after a long crank session. The T/B does not have IAC so idle is controlled by set screw.

I have tried many changes and I just seem to make it worse. I have reworked the cranking VE table per Rinkrat info on another thread. I have reduced the main VE table at low RPM. All this to reduce fueling during cranking. The flames out the stacks and the plugs are black tell me it's too rich during cranking. I have logged my most recent start attempt and the injector pulse ranges from 3 to 4ms. This seems high, especially with the large injectors. Cranking timing is at 12.5*. You will see in the scan file that I tried some throttle peddle while cranking to no avail. This thing should light right off with no throttle required. Why doesn't it?

I have attached my latest bin file and scan file to this thread. Any help or suggestions would be greatly appreciated.
KSD

[Atomic]

Try lowering you min injector pulse to 0.8 across the board and the default injector pulse to .8 from 0 to 3200 and 0 after that.

[Asteroid]

That sounds like a great idea, unfortunately it did not make any change to the starting problem... Same pulse widths which were above 4ms. I could zero out the pw modifier, but it's so low now (around .2ms) that I doubt it would help much.

I have the cranking VE table so low that I added 20 points to it across the board to see if that helps. Its still half of the stock values. Any other ideas would be welcome.

I'm wondering if the injector has a minimum default flow that it cannot go below? I may try adjusting my fuel pressure regulator down to 30psi to see if it will allow a start.

KSD

[Atomic]

It does, but if the commanded pulse is less than the min pulse it simply doesnt inject so you should get no fuel, not excess...

What spark system are you using? What fuel pressure?

...and thats the biggest LSx engine ive heard of...that has to be close to maxed out with the available bore and stroke, right?

[Asteroid]

It has C5 coils and I run 58 psi fuel pressure.

The displacement is possible with the LSX tall deck block. I've been building large displacement LS engines for road racing Corvette's for a while and 454 is about as big as you can go with an aluminum block without going to epic efforts and cost. My boat racing class mandates an iron block so the LSX was the natural choice. My class has a 515 cid maximum limit and I'm racing a bunch of old school BBC's. They're not sure what hit them as the high tech small block is right there with the best of them... Yes, it's definitely maxed out. You might get a little more with an after market block due to the raised cam tunnel which would give more room for a longer stroke. I'm at 4.254" bore, 4.330" stroke and 2" rod journals to make it possible...

I have another race next week end and I'll be nowhere if I can't get it to start reliably. Very frustrating.

[Atomic]

Well if its backfiring then that usually means the spark is waaay retarded, so I would start with the spark side of the engine....test all the wires, coils usually dont fail, but if you have an extra pack try it just incase. What spark plugs are you using? Im assuming the cam is lined up correctly with the crank since once its started it runs well...

[edcmat-l1]

In the tune you posted, nothing has been changed as far as inj data, except the flow rate.

The rest of the data needs to be modified to fit, especially the offset.

Also, and this shouldn't really be an issue with that size engine, you may need to reduce the cranking fuel, and the first pulse mass. I've had to do that on bigger injectors, in smaller motors.

[Asteroid]

It's not backfiring, its just burning excess fuel in the headers... My scan data shows that my cranking timing is at 12.5* which is about perfect I think... At this time I do not have control of cranking spark adjustment but I think it is available if I ask Bill for it.

I continue to think the problem is excess fuel delivered at cranking speeds. The problem is, I have not found a way to reduce the pw while cranking. A 4.5 ms pw at cranking speeds with injectors that are 75# has to be putting way too much fuel into the system...

This has to be a PCM tuning problem that I have not been able to solve...

[edcmat-l1]

Wow. So did you not read post number 7 at all before you posted post number 8? Something about a horse and water comes to mind.

[Asteroid]

You might want to check the times on those posts. I was responding to post #6 while you were posting #7. So yes, I posted what became #8 before #7 was available to me... I've been looking for a way to reduce cranking fuel which should be obvious from my earlier posts. So instead of being a smart a$$, provide a little more detail on how to do it instead of generalities. I wouldn't be asking this question if I knew the answer.

I'll drink the water if you get me close enough to the trough.

Asteroid

[Asteroid]

In the tune you posted, nothing has been changed as far as inj data, except the flow rate.

If you are referring to the fact that the other tables in the fuel control section were unchanged from stock except injector size, that is true.

The rest of the data needs to be modified to fit, especially the offset.

I don't modify data, so this statement does not make sense. If you say I should modify some tables, then which tables and by how much?

Also, and this shouldn't really be an issue with that size engine, you may need to reduce the cranking fuel, and the first pulse mass. I've had to do that on bigger injectors, in smaller motors.

The first pulse is a fuel spike to get things moving, after that my injectors are delivering a flow pw of 4+ ms for the remainder of the cranking cycle. Now if you can tell me how to reduce that cranking pw we might get somewhere.

If you read the first response to my thread you will see that I got a very detailed suggestion on how to modify some tables and what to set them to. Try using that as an example of how to help a guy out...

Asteroid

[edcmat-l1]

If you read the first response to my thread you will see that I got a very detailed suggestion on how to modify some tables and what to set them to. Try using that as an example of how to help a guy out...

Asteroid

As for the very detailed suggestion, I did read it. I also read how well that worked out for you.

I guess I should have avoided your thread altogether. I don't exactly spoon feed infomation. Rather, I'll clue you in to where you should make changes (lead you to water), I won't pour it for you.

If you're tuning your own stuff, at some point you will have to learn what the different tables do, and their affects.

G/L

[Asteroid]

Thanks for your comment, sorry I was abrasive. I may be new to this forum but I am not new to HPT.. I do not do this for a living and my experience has been in a rather narrow application (NA strokers). This is the first time I have ever had an engine that would not start for me and the stock cranking tables just have not been something I ever needed to work on.

Believe me when I say I did not want to come to a forum and beg for help. I did do a search here before I posted and there was almost nothing available on over fueling while cranking.

I am working on the fuel control page as you suggested and I am learning a lot from that. If you would just clarify this comment: "....especially the offset", I will go away and get it figured out. Which table contains the 'offset' that you were referring to?

KSD

[Atomic]

I have the correct data for the siemen's 60s as provided by greg banish, and the only tables that were appreciably different in relevant regions were the ones I mentioned in my first post.

With that said, what is your battery voltage while cranking? You haven't mentioned what plugs and their gap either. If it has been consistently over-fueled then one or more may have fouled, causing starting to be even harder.

[Asteroid]

I have the correct data for the siemen's 60s as provided by greg banish, and the only tables that were appreciably different in relevant regions were the ones I mentioned in my first post.

With that said, what is your battery voltage while cranking? You haven't mentioned what plugs and their gap either. If it has been consistently over-fueled then one or more may have fouled, causing starting to be even harder.

Yes, I have been concerned with that also. This is a 14:1 engine and I have a geared starter on it to help with cranking. My data shows that it is cranking at 60-70 rpm with a fully charged battery. The plugs are NGK TR6 gaped at .055". They are black but not wet from rich cranking. The fueling is correct at WOT as verified by WB and the plugs are a light greenish tan from the Sunoco 110 fuel. I have pulled the plugs several times during this ordeal and brushed and cleaned them and blown them out with air. They are still black after this cleaning. This does not help much and I plan to buy another set to see if that helps.

[Atomic]

I would try a tighter gap, maybe around 0.045". I ask about the battery voltage because that is very important for injector response, not just cranking power.

I think you should set the cranking VE table back to normal, as that isnt your problem and could be creating more problems than solving. This is the one I used on my 408 stroker,

70.0	70.0	70.0	70.0	66.2	63.0	61.0	59.0	57.0	55.0	53.0	53.0	53.0	53.0	53.0	53.0	53.0	53.0	53.0	53.0	53.0	53.0	53.0	53.0	53.0	53.0	54.0	54.5	55.0	55.4	56.0	56.0	56.0
75.0	75.0	75.0	75.0	69.7	66.0	61.6	60.2	58.8	57.4	56.0	56.0	56.0	56.3	56.6	57.0	57.0	57.0	58.0	58.3	58.6	59.0	59.0	60.0	61.0	61.3	61.0	62.0	63.0	63.0	63.3	63.3	63.3
80.0	80.0	80.0	80.0	74.4	69.5	62.0	61.0	60.0	59.0	58.0	59.0	60.0	60.8	61.3	62.0	61.0	62.0	63.0	63.5	64.0	64.0	64.0	65.0	66.0	66.4	67.0	68.0	68.0	68.0	68.8	68.8	68.8
90.0	90.0	90.0	90.0	80.9	73.9	62.4	61.8	61.2	60.6	60.0	61.0	62.0	64.0	65.0	66.0	66.0	66.0	67.0	68.0	68.0	68.0	68.0	69.0	69.0	69.5	70.0	71.0	72.0	72.0	72.0	72.0	72.0
100.0	100.0	100.0	100.0	90.0	80.0	64.0	63.0	63.0	63.0	63.0	64.0	65.0	67.0	69.0	70.0	70.0	70.0	70.0	70.0	70.3	71.0	72.0	72.0	72.0	72.7	73.0	73.0	75.0	75.0	75.0	75.0	75.0
100.0	100.0	100.0	100.0	90.0	80.0	66.0	65.4	66.6	67.8	69.0	70.0	70.5	71.0	71.2	71.5	72.0	72.0	72.0	72.0	72.0	73.0	74.0	75.0	75.0	75.0	75.0	75.0	76.0	76.0	76.0	76.0	76.0
100.0	100.0	100.0	100.0	90.0	80.0	67.7	66.0	67.5	69.0	70.5	71.0	71.5	72.0	72.5	73.0	73.0	74.0	74.0	74.0	74.0	75.0	76.0	77.0	77.0	77.0	77.0	77.0	78.0	78.0	78.0	78.0	78.0
100.0	100.0	100.0	100.0	90.0	80.0	68.7	66.6	68.4	70.2	72.0	72.0	73.0	74.0	75.0	75.0	75.0	76.0	76.0	77.0	77.0	77.0	77.0	78.0	79.0	79.0	79.0	79.0	79.0	79.0	79.7	79.7	79.7
100.0	100.0	100.0	100.0	90.0	80.0	73.6	72.0	73.0	74.0	75.0	75.0	76.0	76.5	77.0	77.0	77.0	78.0	78.0	79.0	79.0	80.0	80.0	80.0	80.0	80.0	80.0	80.0	80.0	80.0	81.0	81.0	81.0

Also change the main ve table back to something more realistic since making it super low is not working.

[DrkPhx]

I don't see it in HPT, but in EFIlive there is a Commanded Fuel when Cranking table which is the commanded AFR value based on ECT and 24X counts. It's very sensitive to adjustment and controls the AFR from the initial crank and transition to the OL commanded fuel table once in idle. I would take a look at this table. If you log commanded AFR you can confirm the actual values Also, 12 degrees spark for cranking is awfully low for such a big cube motor with ultra high static compression. My 02.

[edcmat-l1]

I don't see it in HPT, but in EFIlive there is a Commanded Fuel when Cranking table which is the commanded AFR value based on ECT and 24X counts. It's very sensitive to adjustment and controls the AFR from the initial crank and transition to the OL commanded fuel table once in idle. I would take a look at this table. If you log commanded AFR you can confirm the actual values Also, 12 degrees spark for cranking is awfully low for such a big cube motor with ultra high static compression. My 02.

There is no single table in either EFIlive or HPtuners that "controls the AFR from initial crank to OL commanded fuel table". It is a series of tables, adders, and timers. Getting them all to work together is harmony is more trial and error thing than anything else. Usually, with the bigger cubed motors, with 60 lbs SD injectors, you normally don't have to do this.

To the OP, the "offset" table I'm talking about is the Offset vs Volts vs VAC under injector control.

[DrkPhx]

Ed - I don't know what it's called in HPT; but in EFILive it's called the Commanded Fuel When Cranking (B3604). The values can be set to either EQ ratio, AFR or Lambda and it's located in the Crank/Start folder. If you log commanded AFR, you can see the AFR values transistion (using the runway highlight feature) from this table to the OL Commanded (along with the after start added tables) AFR Table.

OP - Sorry for the thread hijack. I was just trying to offer some additional input.

Here's the description from EFILive:

When the engine is cranking, this is the commanded fuel.
Based on engine coolant temperature at startup and the number of times the 24x sensor indicates 90° of engine rotation.

[edcmat-l1]

In HPT it's cranking fuel. But it's only part of the equation. Even in EFilive, you have INITIAL FUEL PRIME, NON SEQUENTIAL FIRST FUEL PULSE, AND NON SEQUENTIAL SENCOND FUEL PULSE. And then all of these tables have delay timers. And then there's your after start enrichment tables that add before you end up settling in the open loop EQ table.