Speed density nerds only please!

[NIKwoaC]

If its true that a speed density system can eventually learn to adapt to increases in air flow so long as the cam allows for decent vacuum at idle...

And the computer "ignores" the O2 sensors at WOT...

Then how does the speed density "learn" to add more fuel at WOT? Does the computer actually take readings from the O2s during WOT and not apply them to the current conditions, but instead save the data until it can be applied later? Is this why it sometimes takes several operating cycles before the EEC IV can catch up with new modifications?

I know there are a group of you guys hidden in a dark basement somewhere just brimming with this sort of knowledge. Lay it on me!

 

[facemelter71]

THere are a couple of good horse power cars running speed density,but they have unlimited electronic resources.Switch to masss air.Thats the best i can do for ya.

 

[vristang]

subscribing
because I am not sure if the SD ecu operates the same as the MAF strategy for Adaptive Fuel....

 

[Mike85000]

From what I've read, the SD's adaptive limit is about 12-15% max.

But that being said, the ECU ignores O2 readings at WFO, it runs open loop which uses known stored values.

However, the values it refers to for open loop operation are modified by the learning strategy during closed loop.

Some people seem to have good luck with HCI SD setups using a cam from one of the many SD safe charts. I have a feeling that many of these setups work by accident.

The SD ECU can only determine how much fuel to inject by measuring MAP vs RPM vs Temp and TPS. It has tables from the factory, and can only deviate so much from these values to adapt (12-15%). The ECU baseline tables were established by ford for the bone stock 5.0L.

A stock 5.0L vs a modified one could have the same vacuum at a given rpm, but the modified motor would be moving a lot more air. Therefore the modified engine would run lean. The ECU would read the lean O2 sensors, and add fuel. But it can only adapt so much (the "Adaptive Limit"). You can play with this level with fuel pressure tweaks to some point i'd imagine.

Now back to my theory about it working by accident.

Some ppl do the HCI, throw in a cam that has a little more duration and overlap than the ECU is used to, therefore lower vacuum.


The change in MAP reading compared to the stock cam can at some points through the curve cause the ECU to compensate fuel, but not for the right reason.

This last part is all speculation by me and may be completely wrong.


All in all, I'd say if you stay conservative with the cam, and play with the fuel pressure you should be able to get it to work for you.


There are quite a few people who know much more about this stuff than me, try s b f t e c h

 

[lang williams]

Here's a speed density cam chart. That site has a lot of SD info.

http://www.50tech.com/viewtopic.php?t=50694

 

[NIKwoaC]

Here's a speed density cam chart. That site has a lot of SD info.

http://www.50tech.com/viewtopic.php?t=50694

I have heard that/seen that a MILLION times. Still doesn't answer my Q! It is good info, nonetheless.

 

[lang williams]

From what i've read as long as you keep a sd friendly cam that supplies enough vacuum you can swap heads, super charge or add nitrous. One of the mustang mag editors had a supercharged 347 running SD. The big knock i heard was once you pass 300 HP an need bigger injectors you need a custom chip.

 

[ratsride]

From what i've read as long as you keep a sd friendly cam that supplies enough vacuum you can swap heads, super charge or add nitrous. One of the mustang mag editors had a supercharged 347 running SD. The big knock i heard was once you pass 300 HP an need bigger injectors you need a custom chip.

give me more info on your combo, pm me .. i am pushing 400+ rwhp on a sd system and yes upgrade the injectors , rob them from a s/c or lighting depending on the cam you want to run.

 

[NIKwoaC]

give me more info on your combo, pm me .. i am pushing 400+ rwhp on a sd system and yes upgrade the injectors , rob them from a s/c or lighting depending on the cam you want to run.

Woah, trying to revive my old thread? Care to elaborate on your setup? I'd like to hear what you have to say.

 

[Mustang5L5]

Subscribing. I'm still rocking SD even though i have a MA kit. I refuse to convert until i need to

 

[mavmavv]

I know a lot of boosted LS1 guys run SD once they max out the air flow that a MAF is capable of reading.

Im not familiar with 5.0 SD vs a late model GM SD tune.

 

[NIKwoaC]

Subscribing. I'm still rocking SD even though i have a MA kit. I refuse to convert until i need to

That's always been my take on it. SD + 86 motor = boat anchor. My car probably won't see MAF until a new chunk of cast iron nestles between the strut towers.

I'd still like to hear from some people with some serious SD tech knowledge. I do know that some racers and/or forced induction guys run SD, but those are all custom built efi systems.

 

[joel5.0]

If adaptive strategy is used in the logic, it does affect any "open loop" condition....... including WOT. Old school '88 setup with an AOD I've worked on, requires a system KAM reset at the track every time, in order to obtain the best ET's.

 

[tmoss]

Old school '88 setup with an AOD I've worked on, requires a system KAM reset at the track every time, in order to obtain the best ET's.

Absolutely, auto or manual. Do it before a dyno too.