I have been doing a ton of reading about how ls1 guys (speedinc in particular) are having great success with hptuners and speed density setup. My question is:

If I go into tunercat and check off speed density, what are the goods/bads for tuning my turbo 383 project when its done?

With the MAF, I will probably max it out with some boost. I assume this means that I should have a summer tune and a Fall tune (one for hot weather and one for cold weather) since the MAF wont be able to make changes to A/F. I have no problem wit this. However, if I can get rid of the MAF and still have great driveability and performance, then that sounds like the way to go. Anyone feeling like discussing the differences in the two setups? Thanks.

Jon

 

speed density also relies on the MAP sensor, whichis only good to 1BAR, you can use a 2BAR sensor, but you must rescale all your tables that have to do with KPA in your tune...go to diyautotune.com and check out the megasquirt system, thats what i plan on using

 

Yeah, definitely need to use 2 bar sensor anyway (whether I do maf or speed density). Thats how I planned on controlling timing. What aout issues with controlling fueling with a maxxed out MAF versus the speed density setup. anyone care to explain?

 

I don't have any info to add, but consider me subcribed. TTT

 

Subscribing. . .

I've been considering this for my car also. But, I'm running 20 psi, so I'd need a 3 bar map sensor.

Also keep in mind that the factory VE tables go up to 99% and they won't accept a value greater than that. You'd have to half the VE table and injector constant to allow yourself to go over 100%.

Mike

 

speed desity use the VE tables? ive never messed with the speed density system

 

The VE table is the fuel map for Speed Density mode.

 

On a SC engine can't you leave the MAF on and once the MAF maxes you tune using the PE tables? Some say the pcm goes into speed density mode once the MAF is maxed.

Since a centrifugal SC increases linearly with boost can't you just increase the %change to Air/fuel Ratio Vs. RPM @WOT and the % Change to Fuel/Air Ratio Vs. Cool Temp @ WOT?

That is from tuner-cat btw which i understand is the same as the PE tables in LT1edit.

 

What you just described is the currently accepted method to provide fuel for FI cars with the MAF system and it works well, and is probably the preferred method to retain driveability on cars that are driven on a daily basis. From what I understand, there isn't much difference between speed density and tuning with the PE tables after the MAF maxes out, the main benefit would be removing the MAF as an airflow restriction. Plus leaks in the intake system, while still not desirable, would be less of a problem to tuning and engine performance and you could put the bypass valve wherever you want on the pressure side and still vent to the atmoshere. I have no problem admiting my lack of experience with PCM tuning though and all this could be dead wrong. If it is, someone corect me so that I can learn from it.

 

The problem with that method is that the computer is blind once the MAF maxes out. During the transition to full boost, there will be a rich spot, and it won't compensate when you change the boost level. For instance, if you tune for 11 psi, then adjust the wastegate for 18 psi, the computer never knows the difference so it'll run lean.

 

I am running 2bar map on my turbocharged 93 LT1 vette. It seems to run fine. A friend did all this for me.

 

What causes the rich spot when the MAF maxes out? Changing the boost is not as much of a problem for us guys who have thier compressor attached to the crankshaft, but I can see where that is an issue for you beltless boost guys. Do you feel that staying with the MAF is the best way to go?

 

What I'm saying is. . . with a supercharger, if you are using PE tables to adjust A/F ratio once the MAF maxes out. . . then you've added, say, 20% fuel at WOT and 5000 rpm. So, if you were riding along at 5000 rpm, then hit the gas, it would transition through an area where the 20% is being added even though it isn't needed.

No. For the reasons I stated above and others. Basically, once the MAF maxes out, you might as well have a carburetor because the injection is deaf and dumb. Furthermore, there comes a time when you'll need more than the 50% max the tables will accept.

Mike

 

I have a 2 bar setup running on my T-Trim 93 formula. It took quite a bit of playing to get alot of the stuff right and even more to get the car to go into a good closed loop without trying to acheve 14.7 at or near boost. Without a emulator I would have probally never figured it completely out.

I had alot of problems with everything from DFCO, coldstart open loop, AE, etc.. Basically almost everything i had access too had to be changed.

 

Will,

Could you email or PM me a list of everything I would need to run the megasquirt on my car.

Thanks
Travis