Thanks for reading my post.

Quick question.

I have a 383 that has been built quite mild. It is going to be converted to a TPI, and installed in a 4x4. The question is whether to go SD or MAF.

Which is better SD or MAF, or is this simply an academic question?? Its my understanding I can simply install a 350 MAF system without having to worry too much about a custom chip, whereas the SD may require significant tuning.

Any tips or advice are welcome.

cheers

 

If it was a mild 350 I'd say you'd be OK with MAF, but for that engine go SD.

 

It is really going to depend on how much HP you plan to make and how much of the "tuning" you wish to be a part of (i.e. burning your own eprom).

First, 383s, even mild ones, move a lot of air. I am currently helping a friend "tune the eprom" for his 383 Miniram with AFR 195 Competition Ported heads with 2.05I/1.60E. We are planning on swapping SD, but we've been seeing how far you can push the MAF system with tuning. And yes, even with MAF, you will need to do a lot of tuning and testing.

The reason is, he is maxing the MAF (255 gm/sec) at 5,000 rpm. However, his engine makes peak HP close to 6,500 rpm. So we still need to add more fuel 1,500 rpm beyond what the MAF can register. With the "Power Enrichment %Change AF Ratio vs RPM" we can add fuel all the way to 6,400 rpm, but we've had to do a fair amount of testing to determine the proper amount as we are "flying blind", and using "old fashion methods" to tune our mixture like reading spark plugs. We are currently looking at building a WB 02 sensor so we can "fine" tune fuel with the PE tables.

So, if you max the MAF, you aren't "dead meat" and "forced" to go SD provided you want to get into eprom burning to "compensate" for the lack of fuel correction by the ECM once the MAF hits 255 gm/sec. Tuning the fuel tables would be more precise and easier with SD, but you don't have to go MAF.

Also, based on my experiences helping tune my buddy's 383, you should be okay with a stock TPI as your peak HP is most likely to be less than 5,000 rpm; which is the point where he maxes the MAF.

As for the eprom. MAF or SD, you will most likely need to tune it. MAF compensates for air flow (provided it has certain key parameters set), but does nothing for the spark tables and thats where the power is. Proper control of the spark advance curve and minimizing knock retard is the key to power. The best place to do that is in the eprom and to do it right, you need to do a LOT of testing.

 

I AM USING THE STOCK MAF ON A 400 TPI THAT WAS BUILT MILD. I WANTED ALL TORQUE AND RUN IN THE LOWER RPM RANGE. I HAVE A BUNCH OF POWER EVEN AT 1500 RPM, AND DON'T RUN OVER 4500 RPM. I DID PUT IN LARGER INJECTORS BUT HAVE NOT UPDATED THE COMPUTER YET. WILL DO THAT IN THE SPRING. ONLY PROBLEM I AM HAVING IS IN THE 10-20 DEGREE WEATHER, IT FLOODS OUT A LITTLE AT 1000-1500 RPM IN THE MORNINGS WHEN I START TO WORK. ONCE WARMED UP, IT DOES JUST FINE. SO IF YOU ARE RUNNING THE LOWER RPM RANGE I WOULD SAY IT WILL WORK JUST FINE. I HAD TO DRAW THE LINE SOMEWHERE ON THE $$$, AND THE INTAKE WAS THE LINE WHERE I STOPPED. IF YOU ARE GOING TO RUN UP OVER 5000, YOU SHOULD UPDATE

 

i would go with the speed density setup. the instalation is slightly easier and the speed density system will offer slightly more airflow for the engine. It may only be worth a few horsepower butevery little bit counts. with either setup the added cubes are going to require some custom tuneing there is also the issue of the speed density has a faster engine computer. Both are good systems but if theprice diffrence between the two systems is slight i would go with the speed density setup.

 

Your running rich and when the engine is cold, it relies on the "settings" within the eprom which in your case is incorrecct. I predict that if you ever ran a scan tool on it that your BLM/INTs are really low.

Definitely get that eprom tweaked. You wasting gas whenever the engine goes into open loop, which is more often than people realize. Also, you probably not getting the performance you are capable of.

Scope out the DIY Prom Board and track down Formul5. He has a MAF 400 and was EXACTLY in the same boat as you until he "bit the bullet" and dived into eprom burning. Formul5 is looking for other MAF 400 users to "share experiences" so they can get better performance.

But if you don't hurry, I'll convert him to the "Dark Side of the Force" and make him an SD user.