Engine Problem and I'm Not Happy

[Paladin06Greg]

Well this time you are wrong!

Don't sweat it happens to all of us.

Also I think I've found the problem and it's not the A/F ratio. I'll be sure after I run the car tomorrow.

JoeB,

How in the HECK did you come to that conclusion. Please don't put words in my mouth. I barely have room for my foot now.

Sorry if I came to the wrong conclusion. That's the problem with written communication, sometimes that happens. The way I came up with that conclusion is when Rizal pointed out that Arrieta's built the 3 of our engines, yours was the only 1 having a problem and 1 thing different waas the MSD Ignition. Then you pointed out that the MSD Ignition had been eliminated and that you weren't happy, I don't see any other way to read that but of course I could be wrong and sorry about that.

As for the tuning, no I wouldn't "0" out the S-AFC and start over. 0 in the low throttle would be very rich. The thing is, at idle, we are at the base of the air flow signal from the MAF. It doesn't make a difference if it is the stock or TT MAF, they will be close. That is the biggest factor determining the amount of fuel that will be delivered. Based on the fuel map in the ECU, at idle it will hold the injectors open a certain amount of time for 14.7:1 A/F. Then the feedback through the closed loop system will write in temporary corrections for temperature, altitude and slight changes in the state of the engine. If the ECU thinks it is holding the injectors open for lets say 5mS on 250cc injectors but you have 370cc injectors, it will spray 48% more fuel than it should. I would expect the correction at idle to be very close to that. Maybe less depending on how much different the voltage is from the MAF at idle.

As you start to accelerate, the voltage will go up slower than it did with the stock MAF because the percentage of airflow accross the MAF is lower in its total capacity. Therefore the amount of fuel will be better balanced as you go up (closer to 0 correction). At the top end however, you will most likely need to add fuel as the TT MAF is more closely matched with larger injectors. With our 370cc injectors, I think I added around 10-15% at red-line.

Hopefully you can get it straight fairly quick. Running that rich usually leads to very frequent plug swaps and that's no picnic. From your description, you might need to swap the plugs to even get it tuned if you're still getting the misfires. Then you'll need to tune it in as short time as possible to keep the plugs firing. After that, you may want a fresh set of plugs in. Denso is going to love you. -JoeB

[Alex(AUS)]

In all fairness Greg, Joe is trying to diagnose your car on a forum So he could be wrong. It isn’t exactly easy to see what is wrong from what you have said. However, running rich and/or a bad tune sound plausible. From the brief description you have given, to me, it sounds much more serious (and I sincerely hope its not). If it isn’t a rich condition or a really poor tune I would be more inclined to do some compression checks. I know you have forged pistons but this sounds alot like other problems I have seen in the past (once again I really hope not). Do a compression check just to be reassured it isn’t a problem. Just my 2c.

Good Luck!!!

Alex

Well this time you are wrong!

Don't sweat it happens to all of us.

Also I think I've found the problem and it's not the A/F ratio. I'll be sure after I run the car tomorrow.

JoeB,

How in the HECK did you come to that conclusion. Please don't put words in my mouth. I barely have room for my foot now.

Sorry if I came to the wrong conclusion. That's the problem with written communication, sometimes that happens. The way I came up with that conclusion is when Rizal pointed out that Arrieta's built the 3 of our engines, yours was the only 1 having a problem and 1 thing different waas the MSD Ignition. Then you pointed out that the MSD Ignition had been eliminated and that you weren't happy, I don't see any other way to read that but of course I could be wrong and sorry about that.

As for the tuning, no I wouldn't "0" out the S-AFC and start over. 0 in the low throttle would be very rich. The thing is, at idle, we are at the base of the air flow signal from the MAF. It doesn't make a difference if it is the stock or TT MAF, they will be close. That is the biggest factor determining the amount of fuel that will be delivered. Based on the fuel map in the ECU, at idle it will hold the injectors open a certain amount of time for 14.7:1 A/F. Then the feedback through the closed loop system will write in temporary corrections for temperature, altitude and slight changes in the state of the engine. If the ECU thinks it is holding the injectors open for lets say 5mS on 250cc injectors but you have 370cc injectors, it will spray 48% more fuel than it should. I would expect the correction at idle to be very close to that. Maybe less depending on how much different the voltage is from the MAF at idle.

As you start to accelerate, the voltage will go up slower than it did with the stock MAF because the percentage of airflow accross the MAF is lower in its total capacity. Therefore the amount of fuel will be better balanced as you go up (closer to 0 correction). At the top end however, you will most likely need to add fuel as the TT MAF is more closely matched with larger injectors. With our 370cc injectors, I think I added around 10-15% at red-line.

Hopefully you can get it straight fairly quick. Running that rich usually leads to very frequent plug swaps and that's no picnic. From your description, you might need to swap the plugs to even get it tuned if you're still getting the misfires. Then you'll need to tune it in as short time as possible to keep the plugs firing. After that, you may want a fresh set of plugs in. Denso is going to love you. -JoeB

[Paladin06Greg]

Thanks all.

[SC V6]

you figure it out?