Megasquirt 380SL -> 560SL

[hotshoe]

Originally Posted by RadioTek

Megasquirt measures Incoming Air Temperature. The O2 sensor on the exhaust measures how close the fuel/air mix is to 14.1 to 1 and adjusts the mixture accordingly, with fine adjustments from the software.

Scott

Planning a conversion myself.

WOW, I'm impressed. I guess calculations could be made to do this but if GM and Ford could leave the mass airflow sensor off I'm sure they wouldn't spend the money on it. Is the megasquirt a pulsed injection? Or a continuous injection. I ask these questions more out of curiosity than anything else. I have my 560SL running pretty sweet with the fuel system mods I have done already, but if a major part takes a dump (fuel distributor) I'll be looking to a more modern modification.

[RadioTek]

From what I gather, it was designed for simplicity in the earlier versions. Possibly because MAF's were either very expensive or had a lot of 'proprietary' behavior. It's an option on the newer versions of MS, from what I gather.

Just found a port on the manifold that looks like I might be able to weld an O2 sensor bung onto, so I'm ordering my pieces for the build.

Scott

[hotshoe]

GregZ looks like you did a great job. I like it a lot, and your workmanship looks outstanding. Please keep us posted on the tuning phase and how great it runs.

Radio, I will be watching your progress with great interest. I assume that you will be posting on other boards also?

[Mike D]

MS uses a MAP system as opposed to a MAF style. I believe it can use the MAF but since it comes with a MAP already installed on-board it only makes sense to base it on manifold pressure. Intake air temp is only used as a qualifier to the MAP control algorithm.


MS is "pulsed" but the MSII only does "batch" fire. The newest version (MSIII) is capable of sequential injection (operating individual injectors in the firing order sequence). Either of the systems is a vast improvement over the originals in terms of emission control.


Megasquirted M117, M110 and M115. Fuel only but I'm getting closer to getting the M110 to fuel and air.

[Strife]

MAF's aren't simple "resistance" elements. On a GM, it's a heated platinum element with a built-in circuit that would change an output frequency/ square wave duty cycle depending on how cool the platinum element gets (that's why they are so expensive). They have very, very thin/delicate elements so that they can change readings very quickly. When they get dirty, they get insulated from the cooling properties of the air or have more mass and get "slow to change" or don't change at all. Cleaning yields varying results. Running with a leaky air intake filter or no filter element at all can kill them fairly quickly. So can an engine compartment with a lot of oil (like from leaks, or blow-by and a bad PCV system).

It is my understanding the newer megasquirts can use them as an adjunct to the MAP, or even instead of it. Only the new ones can do it because the processors are fast enough to measure the pulses.

Many people on boards don't think they improve running/economy/emissions any more than a good MAP.

[Strife]

Originally Posted by Mike D

The newest version (MSIII) is capable of sequential injection (operating individual injectors in the firing order sequence). Either of the systems is a vast improvement over the originals in terms of emission control.

I've been debating going with sequential but I haven't found anyone who has conclusively found it to be "better", and a lot of people have found it to actually be worse - possibly because timing it is a black art, and only for direct injection (straight into the combustion chamber) would it make absolute sense.

On that subject, a backyard mechanic of the future (if any...) is going to find it very difficult to improve on the FI systems of post-2010 cars...

[RadioTek]

Originally Posted by hotshoe

GregZ looks like you did a great job. I like it a lot, and your workmanship looks outstanding. Please keep us posted on the tuning phase and how great it runs.

Radio, I will be watching your progress with great interest. I assume that you will be posting on other boards also?

I'll be starting a build thread here and at Benzworld when I get the pieces and start putting this thing together.

I'm not Roncallo, so it will be nowhere near as thorough and detailed. Especially since my garage is a real mess.

Rule Number One on garages: NEVER let your wife store ANYTHING in your garage, even if it is only temporarily. It isn't temporary, and it breeds and multiples when you turn your back.

Scott

[GregZ]

Based on RPM, engine displacement, air temperature, manifold pressure and ambinet pressure, you can calculate how much oxygen is actually entering in the combustion chamber. This calculation can be as (or more) precise as a MAF reading except it cannot react as fast to a quickly changing RPM as a MAF can.

Tuning indeed is a black art. I have not have it down yet. I actually have not tuned the engine much (just to the point of it running decently). I have had to put this on the side-burner (plus I started working on its body, so it is somewhat body disassembled and all grey). Too many things to do....


so true! :
"Rule Number One on garages: NEVER let your wife store ANYTHING in your garage, even if it is only temporarily. It isn't temporary, and it breeds and multiples when you turn your back. "
I get into constant arguments with my wife, and I have a four car garage now (brag, brag)