Why Won't it Start Correctly??

[onegonewild]

I have a 97 350 Vortec engine in a 2001 S-10 punched out to 383. With the cam, heads, headers, ported and polished heads, marine MPFI intake, 27lb injectors, and CAI, it is really hard to start this engine. I have tried varying table B0102 and B4343 to make it start a lot easier but with no success. With B4343 where it is now, is the only way i can get it to start without having to shove my foot in the pedal. The injectors are spec'd out correctly and I have proper fuel pressure when cranking. Just seems like I have way too much timing or too much fuel!

NEW CL.tun

I'm using COS5 with a 2002 Chevy Express Van tune in a 0411 pcm. I have the same issues no matter if I keep the factory OS or use the custom.

[Taz]

What TB (throttle body) are you using ?

Your 27 lb injector flow rate - that's at 4 bar (58 PSI) ?

B4001 is setup for a fuel return line / FPR on the fuel rail - that is correct for your install ?

What is the fuel pressure when measured at the fuel rail ?


Regards,
Taz

[slows10]

Maybe not enough fuel. Took a quick look and B3604 is pretty low. Compare some of your tables to a factory stock L31. It will help you check to see if you are in the ballpark with some of the crank/start tables and others. Try raising B3201 also. You probably need more fuel since it is a modified 383 and not a stock 350 L31. Or you may have to go in the direction of more airflow in the startup tables also since it is a bigger engine. If you raised B4343 and it helped you may need more.

[Chuck L.]

Newbie calcs:
You show 3.5547G/S. My calc shows that as 28.21#/hr.
I assumed that the 27PPH is the rate at 43.5psi. [Taz ' ??]
If that's an accurate assumption, then the actual flow of the 27pph inj at 58psi, should be 31.17pph. Again, "newbie calcs"= 3.9274 G/S, is what I get.

[onegonewild]

Taz-
Using a ported 75mm throttle body. I believe 0.0226 is correct for B4349
These are injectors from a 2002 LS1 engine rated at 27lbs. Im using all the tables for injectors from a 2002 camaro except modifying the IFR.
Yes, referenced for vacuum and measuring 58psi at the rail with vacuum unhooked.

slows10-
If I raise B3604, does that increase the fuel when cranking? It feels like it is getting way too much fuel when cranking.

Chuck-
I calculated these out as 27lb injectors from a 2002 camaro. Isn't the camaro rating these injectors for 58psi from the factory?
I called Bosch on these injectors and they state these are a new design for the 2002 camaro and rated at 27lbs. But is that at 43.5 or the GM specs of 58?

[Chuck L.]

Taz-
Using a ported 75mm throttle body. I believe 0.0226 is correct for B4349
These are injectors from a 2002 LS1 engine rated at 27lbs. Im using all the tables for injectors from a 2002 camaro except modifying the IFR.
Yes, referenced for vacuum and measuring 58psi at the rail with vacuum unhooked.

slows10-
If I raise B3604, does that increase the fuel when cranking? It feels like it is getting way too much fuel when cranking.

Chuck-
I calculated these out as 27lb injectors from a 2002 camaro. Isn't the camaro rating these injectors for 58psi from the factory?
I called Bosch on these injectors and they state these are a new design for the 2002 camaro and rated at 27lbs. But is that at 43.5 or the GM specs of 58?

I flow tested a set of 0280155931 injs for a test project. They are out of an 01 Vette/LS1.
The info as I recorded it:
Flow fluid 6.41#/gallon.
AT 43.5psi = 25.6#/hr.
At 60.0 psi = 29.67#/hr.
AIRC, most inj flow ratings are at 3 bars.
Doing the math, I converted the above values from 60, back to 43.5, and came up with 25.26..Using exactly 58psi, the calc shows the flow at 43.5 to be 25.69.

Here's a link that shows the flow numbers/psi..
http://www.witchhunter.com/injectordata1.php4

HTH,

[onegonewild]

I just figured they were spec'd to flow 27lbs at 58 psi. Hmmmm
I'm going to try your data and see if it resolves. I need to wait until the engine is cold and will let you know the results.

Thanks!

[slows10]

Yes best to figure out your IFR before adjusting anything else. S10 fuel pressure should be 58 psi at rail with vac line disconnected. With it connected and at idle mine is around 53-54 psi. Im not sure if the vortec L31 is the same, I think it may be.

[Chuck L.]

Yes best to figure out your IFR before adjusting anything else. S10 fuel pressure should be 58 psi at rail with vac line disconnected. With it connected and at idle mine is around 53-54 psi. Im not sure if the vortec L31 is the same, I think it may be.

That's pretty much the kind of drop I look for....

[onegonewild]

I'm running a Regulator from a 2002 Corvette on a MPFI intake from the Mercruiser Marine engine.

Ill plug those IFR values in, recalculate VE table, and let you guys know!

Thanks!