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> Possible Lean condition in L-jet motor - HELP, Fuel injection issues
Cupomeat
post May 28 2008, 04:11 PM
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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

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Brando
post May 29 2008, 01:19 PM
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First you have to determine if it's fuel or ignition... the WBO2 sensor will help you figure that out with an A:F ratio.

If you know your timing is good then no worries there...

L-Jet does use a rising-rate FPR as the captain said. When using stock 1.8 components (injectors, CHT, AFS, FPR, etc) and going up in displacement you might have to adjust the air flow sensor to give more fuel. Again, you need a WBO2 to check and set this right. AFAIK when you hit the 2.0 liter mark you should go up to 912E injectors as they flow more than stock 1.8 injectors.

With the change in compression you might want to try a bit higher octane fuel... Maybe 89 if you used 87, 91 if you used 89... etc and see if that helps with the pinging.
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