355 Motronic 2.7 vs 5.2

If I had to do it over I would have bought a 2.7 as there are guys on here like NoDoubt who can do chip programing for the 2.7 version................. I have a 5.2 version and there are a few more systems to go wrong on it... like an extra pair of O2 sensors post cats... ...............though at least my valve guides were done !!

 

M2.7 is OBDI.
M5.2 is OBDII.

OBDI means that the fuel maps and programming are stored on a chip. Chip programmable (i.e. you physically swap chips to change the fuel maps or programs). It also means that you don't need a special tool to "scan" or read the error codes. Instead of using a scan tool, you press a button connected to the ECU and the error codes slowly flash your Check Engine Light (CEL) on your dash.

With OBDI, erasing your error codes is as easy as disconnecting your car battery.


OBDII means that the fuel maps and programming are stored in flash memory. Download-programmable (i.e. you connect to the ECU and download code). Error codes remain in OBDII even if you disconnect your car battery. You need a scan tool to delete error codes. You need a scan tool to read error codes (scan tools are cheap...about $30 on Amazon.com).


M2.7 is a symetrical system. Two of everything (one for each side of your engine).

M5.2 is assymetrical. One MAF for your air intake, for instance. M5.2 also tracks more sensors (e.g. an air intake temp sensor in addition to the MAF) and errors than does M2.7 (e.g. 4 O2 sensors on M5.2 whereas M2.7 only has two O2 sensors).

M2.7 is easier to program for more power.
M5.2 is more consistent in emission compliance.


M2.7 fundamentals and "secrets" are somewhat known in the tuner community.
M5.2 has managed to keep most of its internals proprietary and secret.

 

If it's going to be a car you plan on modding 2.7 without question. Unfortunately I really wanted an F1 so I had to settle for the 5.2

 

I own a 355 M2.7 and could say the 2.7 ECU is easy to access and erase and that is a good thing.
Some people say that the MO2.7 are more powerfull than 5.2 but Im not shure.
Too on 2.7 you can remove cat convertors easily because the o2 sensors are before it.
Too the 355 have no airbag and it is nicer inside the car I prefer like this...

 

All of the 355 Challenge cars have the 2.7 system, there must be a reason they stayed with it. More power?

 

Yep

 

2.7 has the nicer air filter.

I feel it sounds better also.
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The 2.7 is a MUCH easier system to work with. The only 355 I would get would be a '95, especially if you are a DIY'er like me.

 

There's no "seat of the pants" difference. That said, my next car will be a 2.7 355.

-Peter (2.5 Mondial t Coupe and loving it!)

 

This is interesting to me since I have a 2.7 Motronic equipped 95 456. I have a dumb question: based on what has been written, I assume that one can super tune the chip to work better, provide more power, etc. How does one go about that on these cars? Do people sell chips already programed or do you have to do the programing yourself? If so, presumably you have to put the car on a dyno and experiment with what you want to do? Finally, how then do you reprogram the chip?

 

To reprogram M2.7 chips, first you pull the chips out of the ECU's and scan them (for 348's M2.7 chips are identical, so you just need to scan one chip from one 2.7 ECU, but for your 456 I can't say that will be true for you - probably is, but no gaurantees).

To scan in an M2.7 chip you need an inexpensive (~~ $140) EPROM reader/programmer such as the Batronix unit at www.Batronix.com.

This will give you a binary/hex file that contains firmware programming for your car as well as your error routines, error codes, air/fuel maps, ignition/coil dwell maps, and spark ignition advance maps.

To find those maps in your hex file, you'll either want to do a search here on Fchat for an index of the maps for your car/model/year...and/or download a map decoder/grapher program (lots of shareware versions on-line).

Pause...

Once you've made it to that point, you then want to graph your personal car's air/fuel ratio while you are at full power. I'd suggest using the Innovate LM-1 wideband O2 sensor to record a good Italian Tune-Up run.

With that air/fuel ratio graph in hand, you are now at the point where you can add or subtract fuel to the air/fuel tables on your Wide Open Throttle (WOT) maps that you scanned in from your chip. To adjust your air/fuel ratio at the right RPM's, you simply increase or decrease as desired the number stored for each RPM section.

Need 5% more fuel at 4000 RPM's? Then bump up the data number stored at the 4000 RPM point in each of your WOT air/fuel tables.

Need 10% less fuel at 5000 RPM's? Then subtract 10% from the data number stored at the 5000 RPM point in each of your WOT air/fuel tables.

Repeat for each RPM section.

Save your changes. Now use your Batronix EPROM programmer to burn two new chips with those changes.

Install those two chips into your two M2.7 ECU's.

Your car should now give you your desired air fuel ratio over your entire RPM band when you slam the accelerator to the floor.

Oh, you can also advance your ignition timing as far as your courage allows (good way to blow a motor, of course).

In this manner your ECU's will give you the maximum performance available for the modifications and condition of your particular Ferrari.


Pause

Now, all of that said, you could just go purchase an aftermarket set of ECU chips for your car. Many vendors sell them for most M2.7 systems. However, those vendors have only made guesses as to what data changes need to be made.

It would be unusual for an aftermarket set of chips to get lucky enough to give you peak performance for your car's mods and wear/tear/condition straight out of the shipping box.

But they will tend to advance your timing a bit from stock while staying in a safe range, so no doubt you'll get some performance boost (at expense of gas mileage and emissions, obviously) from most any decent aftermarket chip.

 

Great response, thank you very much. Sounds like a few hours of dyno time would be good to have for this exercise.

Alberto

 

Last summer I talked to a former F1 mechanic for Michael and he saw my engine out service being done (2.7) and said that it was by far the best system for the 355. He now works on the 430 challenge cars.

 

For me the 2.7 vs. 5.2 debate never was a consideration. If this were the only difference I'd absolutely take the 2.7. But valve guides and an F1 shifter were higher on my list so the 5.2 was my only option. There's also other details which were fixed / upgraded in the newer cars which is nice for safety and reliability (I've heard of a fuel line fix that was recalled earlier, leak resistant PS reservoir, and other stuff I'm sure I don't know about or weren't publicized).

I've heard there's a 5 hp benefit on the 2.7 cars but never saw dyno sheets.

 

I also heard from the same source that the only reason Ferrari went to the 5.7 was to save money. For me 6 speed is what driving is all about. The valve guide issue is overblown and I think most of us know that, in fact there is some talk now that the steel guides in the later models may cause problems down the road. As for power all you have to do is look at the air restrictions in the piping added to the 96 and up models and its only obvious which system has more power. All in all every 355 is an amazing machine. But the 95 gives you more options. Much easier to run straight pipes and chip tune. My 355 will smoke a 360 everytime.

 

It was U.S. legislation that did it. 1996 cars (there may have been some exceptions for 1996 models already shipped) and on had to have air bags and OBDII.

Ferrari sometimes gets complete exemptions from U.S. legislation based on its small production volume, but didn't win one that time.

So Ferrari couldn't keep the impressive M2.7 systems.

M5.2 is a good OBDII (2) system, though.

But M2.7 is a fantastic OBDI (1) system.

 

How much ignition timing advance is considered safe?

And what A/R ratio are we looking for across the rpm range? What A/R fuel ratio is ideal for cruising rpms for fuel efficiency?

What's the best location to place the wideband? Should we have two widebands for each side or should the wideband be placed where the headers converge at the y pipe?

 

are you sure you are not overestimating yourself with believing that you are the DIYer you think you are?

this because you have 10 hours of reading and couldn't find the main differences between 2.7 and 5.2 and and on top of that the engine management is only a small part of the car.
even on a 5.2 you can do everything yourself.

as a DIYer why would you have a PPI done by a third party? in my view, I would judge the status of my car myself and take it as is for the right price.

I remember when I bought my car, I didn't even test drive it. it looked good, had a good feeling and the price was OK and on top of that wouldn't loose more valuable time to look at other cars.

 

I would lean toward a 5.2 only because it is self diagnosing in many ways. Believe me, you will need it.

 

I'm not sure how much ignition advance a 355 runs but typically you can creep up on it on a dyno, observing spark plugs for signs of detonation and also power output. (if you add a few degrees and gain no more power, or lose power you have went to far).

I like to run a few less degrees at peak tq.

A/F ratio at wide open throttle for a naturally aspirated engine for max power will be in the 13.0-13.2-1 range but I run it a few tenths of a point richer at peak torque. (and also a few tenths of a point richer if it's going to be road raced).

Wideband a few inches after the header collector is fine. Dual wideband is convenient but you could just have a bung after each collector and swap the wideband from side to side to verify fueling is the same.

During cruise the vehicle will be in closed loop (relying on o2 sensor feedback for fuel trims) and forced to stoichiometric, or 14.68-1 for gasoline. (actually is closer to 14.1-1 as most fuel has 10% alcohol but a wideband on gasoline scale will show 14.68).

 

Thanks for that info James. Are you running 93 pump?

"I like to run a few degrees less at peak tq"

A few degrees less than the factory default?

 

I don't have my car yet so not running anything yet! But yes I always have ran 93.

What I mean by that is, instead of having a flat timing curve, say 30deg across the board, if it likes 30deg at peak hp I would probably run it at 27-28deg at peak tq. Peak torque is highest cyl pressure and it's generally easier on the engine (and less prone to knock) to have a bit less timing at that point.

 

The guy who tuned my computers on a dyno added 5 degrees on low end, huge difference.
No stumble and dead feeling below 4000. Great throttle response. Also took a lot of fuel out of low end-- was running rich on low end. My car is a 2.7.