I'm getting a motor and trans out of a 2000 Pontiac everything on it is stock and it has 80,xxx miles. Anybody have a good base tune for megatune? Or do you guys suggest using the donor comp?

Megatune? I imagine that is a standalone.. and in that case yes, just use a stock ecu.. you dont even need to flash a 96-98 gtp pcm.

I believe that he means Megasquirt. If it is the Megasquirt I would say that its far more cost effective to go with the OEM PCM that is already optimized for that engine. I can't see any reason for using a Megasquirt as you would need to develop the tune from scratch and you have no diagnostics in that ECM.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

quote Originally posted by Dennis LaGrua: I believe that he means Megasquirt. If it is the Megasquirt I would say that its far more cost effective to go with the OEM PCM that is already optimized for that engine. I can't see any reason for using a Megasquirt as you would need to develop the tune from scratch and you have no diagnostics in that ECM.

What do you mean by 'no diagnostics'... you can see everything live. You mean no check engine light? True. If you are going to use MS then you would probably be able to figure out what is going on by data logging... the same way you would data log with a stock ECM.

To each their own...

The issue with standalones is simply the time investment...

There is NO reason to run a megasquirt over a stock ecu... The time savings is massive, and the "worry free" factor is also nice, along the lines of what dennis was talking about. He also means more than just a SES light when he is talking about diagnostics. Stuff like knock sensors, PE adjustments, and other timing related safegaurds are dialed in from the factory, and some are much more advanced and complex then you can find in a megasquirt.

Basically, even the BEST standalone base tune would be extremely far off compared to a gm base tune that has months and months of a full team of people working on it.

Yeah i mean Mega Squirt. I'm not to worried about the time investment after all it is a fiero . I am looking for something that can be tuned to the way i like it, have two set ups that i can switch, one for performance and one optimized for MPG and with that it would just be a switch of a program while my laptop was in the car.

A good tune will be one that offers both performance and economy, there is no excuse to have one tune that is not good at the other... Stock GM ecu's do this very well.

quote Originally posted by GT2efiero: Yeah i mean Mega Squirt. I'm not to worried about the time investment after all it is a fiero . I am looking for something that can be tuned to the way i like it, have two set ups that i can switch, one for performance and one optimized for MPG and with that it would just be a switch of a program while my laptop was in the car.

You are describing the factory OEM program that is optimized for all around power and economy. As for tunability, I tune my GTP PCM, no problem. All you need is editing software and a laptop. Modifcations are also easily accounted for with the factory setup.
Megasquirt is a speed density sytem where the fueling is derived from sensor inputs that choose a value in a fixed VE table. You pull the value out and hope that it is correct. The 3800SC system is what they called a MAF based system. In this system actual air measurements are being taken that directly control the fueling.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

quote Originally posted by darkhorizon: A good tune will be one that offers both performance and economy, there is no excuse to have one tune that is not good at the other... Stock GM ecu's do this very well.

Whatever... In Megasquirt you tune a the VE table for various loads on the engine... there is no 'lean cruise' mode... if the engine is under little load on the VE table you lean it out... if you need power you richen it up. Its not rocket science... Also, how much does that supporting equipment/software for programming/tuning OBD-II cost? You have to consider that as well.

Like I said, to each their own... if you want to learn/own why you car is doing what its doing and are will to spend the time, there is no reason not to use Megasquirt. It can be used in parallel with the stock ECM if you want stock tranny control or iginition. Just because GM has separate tables for lean cruise or some other type of operation doesn't mean that one cannot produce the same results in a different way, with one table as in Megasquirt. Like I said if you have the time and desire there is no need to retain the GM ECM for engine management.

quote Originally posted by Dennis LaGrua: Megasquirt is a speed density sytem where the fueling is derived from sensor inputs that choose a value in a fixed VE table. You pull the value out and hope that it is correct. The 3800SC system is what they called a MAF based system. In this system actual air measurements are being taken that directly control the fueling.

You can also use WBO2 to control fuelling, which is also available for OBD-II. The Mass Air Flow sensor gives you the actual volume of air inhaled by the motor vs. a VE table, but it still relies on other sensors on the engine to determine operation. There are still new cars that come with MAP sensors, so it is not like its a dead technology. Once the VE table is dialed in on a given engine it is a pretty dang accurate way to manage fuel, and while it is fixed, it still can extrapolate points between table entries via software algorithms and be adjusted using the O2 readings.

Sounds to me like you're reinventing the wheel... but I'd be interested to see how you make out.

Can MegaSquirt utilize for the knock sensors and pull timing the same way? I would imagine it can.

I was under the impression that MAF is great for daily drivability, but by it's nature tends to lose accuracy with high air flow, so MAP is supposedly better for getting peak performance with high flow. This is the basic explanation I was given: MAF is a hot wire + thermistor, so a given change in CFM will manifest as a smaller change in temperature/signal at higher air flow, so there's naturally less signal resolution in higher RPM. Another way to look at it is that the curve in a graph of CFM vs. thermistor cooling/signal will tend to level off with high flow/RPM - leveling results in less data resolution.

But I could be wrong.

[This message has been edited by FieroGT42 (edited 04-09-2009).]

I should clarify my position... if you are going to use a 4T65E-HD as your transmission, I would definately go with the GM PCM. If you are going the manual route... I would use the Megasquirt if you have the time and inclination, if you just want to plug in a stock 3800SC and run it, by all means use the GM unit.

As far as reinventing the wheel... not really, the system has been tested and used by people with all sorts of applications. Getting the base configuration completed based on engine displacement, injector paramters, etc. is the hard part... the tuning, with a WBO2, is the journey you have to be prepared for

My 2001 Chevy Prizm(Toyota Corolla) as both a MAP and a MAF sensor and only has one catalyst. But still meets all emission standards and gets 35MPG. From what I read it converts to MAP when under high load and uses MAF when cruising. I believe that most 3800's still have a MAP as well.