Don Terrill’s Speed-Talk

maximum rpm velocity at 14^ past top dead center Replace with "peak cylinder pressure" - I can't even contemplate what an RPM velocity is. But, the guy went too far in defining that it's such a precise thing. Maybe he was trying to point out that "more isn't better" but over-def...

Using high octane fuel while incrementally advancing ignition can be used to determine when the combustion peak pressure angle is too close to TDC. It will also show up as reduced plug seat temperatures and increased EGTs at a constant load and speed. I can say with certainty that more advance = mo...

How can you detect pre-ignition in an early fase, if at all possible ? If you're lucky, you felt the power drop and lifted right away. If the source was the spark plug electrode, you might get lucky and completely melt it only before the piston truly overheats - but check compression - it likely at...

With 93, it almost surely was detonation first, if at all, but pre-ignition killed it. Pre-ignition leads to destruction way too fast to allow detonation marking "afterward" because there's usually no afterward. Pre-ignition usually doesn't go away until stuff's destroyed or the throttle i...

Fixed my clutch in - dying problem by moving the throttle blade adjustment screw and resetting the IAC. I lowered counts from around 60 at idle to about 15 and now clutch in is much more manageable. Not perfect, but worlds better. My next tuning issue to figure out is that I am backfiring thru the ...

If it's speed density then density is a function of both pressure and temperature. So if there's no IAT sensor........it's NOT speed density. Likewise if you put the IAT sensor before the throttle .....it 's NOT speed density. Wherever there's a drop in pressure, there's also a drop in temperature....

The air flow will change with the square root of the change in pressure. Doubling the pressure will increase flow by 140% not 200% The actual volume never does change; it is the air density that changes and impacts air mass flow. The pressure ratio that matters is the pressure above the piston divi...

So I have my new Megasquirt system up and running, but I have a slight problem. The ignition signal is from the coil terminal (MS is just controlling fuel at this point) and it is bouncing all over the place from about 700RPM-1200RPM, and then it cleans up and has no issues. When it is jumping arou...

The xtau is only active during accel and not anywhere else. In fact the delay in itself is an xtau imo As for Bill's comment : i think a lot of factors are already accounted for in the 8 ms delay Well, I guess it's not a complete X-Tau then. I've read some Bosch documents and watched the actual inj...

His megasquirt ECU comes with an advanced "X-Tau" model built in, if he wants to go that route. It works but it's really difficult to tune in my experience. Once it's calibrated properly it works great though. You can get very crisp throttle response this way. I've found real X-Tau to be ...

Thank you for your feedback. My original 400 does not have a reluctor wheel, but I though I could add an external trigger easily. The problem is attaching the external trigger to some ECU that could complete a misfire calculation and output a misfire code. I've got something in the pipeline... It's...

I make a cylinder balance calculation in the FiTech system - but it doesn't tell you which cylinder - unless you force a misfire (pull a plug wire). It's not sequential, so there's no cam sensor to know the actual position and phase of the engine, but it is a rolling buffer of 8, so if you see the s...

If you want a 4 barrel or dual quad EFI setup, we'll have them in stock in a few days. You'd keep your distributor setup, and just connect to the coil for an RPM signal. http://www.fitechefi.com. I haven't run it on a 12 cylinder yet, though - and I'm not sure what your manifold choices are.

A single cylinder engine naturally has an extremely "jumpy" MAP. This MUST be sampled in sync with the engine position to get any useful reading. We actually use that MAP signal as a pseudo cam sensor to get sequential operation from a single cylinder or ITB setup. Do you have any ability ...

It's easy to be ahead of the OEMs in terms of chips. New ones come out almost every year and they don't update their ECU designs nearly that often. Building a quality board and using state of the art parts is pretty easy. If Tuner Studio suffices for the user interface, than this seems pretty doabl...