Possible Lean condition in L-jet motor - HELP, Fuel injection issues Options

[Cupomeat]

Ok, I am having the following problem on my 1.8l Ljet induction 914 motor.

First the basics;
1.9L (96mm big bore kit with KB pistons etc.)
8.4 to 1 CR
1.8 heads built out to 2.0l valve sizing, etc.
Stock fuel injection with adjustable FP regulator turned 15% higher than stock, currently(Pre-Lambda L-Jet, bummer)

Now, the symptoms;
Under normal acceleration, the car runs great and sounds fine, but under prolonged full throttle, the engine heat seems to go way up and pinging occurs. No pinging ever happens when I am rowing through the lower gears, but only seems to happen in 5th gear after prolonged Wide Open throttle (WOT).

So, my assumptions;
1. The car is going lean at prolonged WOT resulting in high head temps and pinging.
2. Ignition timing does not seem to play a role in this as I've played around with retarding the timing to decrease the pinging, but it never goes away at Prolonged WOT.

My plan;
1. Buy a WB Fuel/air ratio gauge and weld in the bung for the 02 sensor to support my theory

2. I have an inline fuel pressure gauge in the engine compartment, but can't watch it when I drive the car, especially in 5th gear at WOT (for very long, LOL)

3. Check to make sure the throttle switch is working to trigger WOT

4. If #3 is fine, is it possibly the fuel pump is running out of pressure?

5. I am also going to install a remote oil cooler to try to bring the heat down, but on a mild 1.9l, it seems excessive, especially as I probably have about 85 hp.

6.Probably install a cyl head temp gauge to try to pinpoint temps besides oil.

7In the end, if I have to pay for Dyno time to get to the bottom of this, I will but I'd rather not spend that yet.

Anything else people can think of? Any help/thoughts would be appreciated.

Eric

[toon1]

In your case ( as most ) an 02 sensor WILL be benificial.

you have increased the CC or CI displacement of the engine and the F.I system is not desined to hadle it.

ALTHOUGH, you HAVE increased the F.P. to try and compensate.

15% over stock pressure is about 4 P.S.I. correct? that's about 40cc/min. increase in flow.

Did you do some calcs. to see if that will be enough?

Here's one thing to think of:

1) you have increased the size of the pistons
2) you have increased the size of the valves.

This will create MORE demands for air flow into the motor which should require a bigger TB.

The TB may be too small for sustained high rpm's. When the air intake of a motor is too small, at sustained high rpm's (WOT), the vac. signal; will actually raise(more vac.) as the engine is trying to pull more air that it's getting.

If this is what's giong on, you may see a slight DROP in F.P. because there is VAC. being reapplied to the engine.

it sounds like you have a VAC. gauge. If so it would be easy to do a test.

Keith

[Cupomeat]

In your case ( as most ) an 02 sensor WILL be benificial.

you have increased the CC or CI displacement of the engine and the F.I system is not desined to hadle it.

ALTHOUGH, you HAVE increased the F.P. to try and compensate.

15% over stock pressure is about 4 P.S.I. correct? that's about 40cc/min. increase in flow.

Did you do some calcs. to see if that will be enough?

Here's one thing to think of:

1) you have increased the size of the pistons
2) you have increased the size of the valves.

This will create MORE demands for air flow into the motor which should require a bigger TB.

The TB may be too small for sustained high rpm's. When the air intake of a motor is too small, at sustained high rpm's (WOT), the vac. signal; will actually raise(more vac.) as the engine is trying to pull more air that it's getting.

If this is what's giong on, you may see a slight DROP in F.P. because there is VAC. being reapplied to the engine.

it sounds like you have a VAC. gauge. If so it would be easy to do a test.

Keith

My calculations for increasing the fuel pressure were based on overall displacement increase, but that unfortunately should cause the engine to run rich as lower RPM (while under the AFC flapper box ) control and then right on in the upper RPMs.

Time to calculate a little more.

Hmmm, very interesting, so if at WOT, at say, perhaps 4500, the airflow exceeds the amount of air the TB can flow, it will start to actually increase the partial vacuum until redline.

This would in-fact lower the fuel pressure and run lean... but would not the fuel pressure drop actually preserve the fuel pressure to manifold pressure delta? The Rising Rate fule pressure regulator should maintain a constant pressure delta between manifold and fuel rail pressure. With a partial vacuum, or an increase in vacuum the pressure delta would be the same and it would not make any difference.

Hmmm, OK, now I need to buy a WBO2 gauge, a cyl head temp gauge (4) and a manifold vacuum gauge.

Looks like I'll need more dashboard, LOL!

Great theory, I'll see if I can support it by the instruments.