pcmhacking.net

There is some great work being done here with the LS1 PCM. On top of its already very capable features it also provides sequential ignition and injection, as opposed to batching, as well as being able to drive LS1 coils, all of which I consider great features, especially the LS coils. I mean, who doesn't like the fat spark given off by an LS coil?

Great if you own a V8 but what about the rest of us, be that running non-V8 engines or retrofitting EFI to older non-EFI cars? Thanks to the great work of people on this site the '808 ECU running 12P has catered to the rest of us really well over the years and has evolved way beyond what the original GM designers and developers ever had in mind, but the '808/12P combination has pretty much hit its limit with regards to its capabilities.

I see a few threads have looked into using the LS PCM with 6 cylinder engines but to date, and correct me if I'm wrong, I don't believe any real progress has been done in this area. By far the greatest amount of work has been done with V8 engines in mind as one would expect being a V8 PCM.

I'd like to use an LS1 PCM on my 4 cylinder engine. To date I have not seen any discussion with regards to making these PCMs work with a 4 cylinder engine. The PCM is already capable of controlling a 4 cylinder engine. GMs Active Fuel Management system, when activated, is running on what is effectively a 4 cylinder engine. All the code is already there and working within the PCM. When a certain set of conditions are met the PCM activates AFM and becomes a 4 cylinder PCM and when these conditions are no longer met then the PCM reverts back to a V8 PCM.

If the PCM is artificially held in AFM mode by coding it that way then wouldn't it be possible to control a 4 cylinder motor in exactly the same way that a V8 is controlled, utilising all the capabilities the the V8 guys enjoy?

I'd like to start a discussion as to the possibilities of this working and what would be required, both software and hardware wise, in order to achieve this if it is achievable, and if not, then why not?

So, am I crazy or could this work?

Thanks.

Chuff

The AFM stuff is on the later E38 PCMs on the VEs, not the P01 and P59. The 6 cyl version works in factory configuration, but only in batch mode. While there isnt much in software I imagine you could attempt to put one on a 4 cylinder engine now by replicating the trigger system for the v8, and only installing half the injectors and coils. It'd be a bit weird and the trigger system woulnt be the easiest thing to fabricate but I dont see why you couldnt if you really wanted too.

There's an old post on the efi live forum about using an ls1 ecu on a 4 cylinder one guys runs his turbo 4 cylinder suzuki motor on one 24x reluctor wheel 1x cam

@Antus - Thanks antus. I wasn't aware that AFM was on the E38 & not the LS PCMs. That kinda makes my 1st post null & void. I get what you're saying about only installing half the injectors & coils but I'd imagine the PCM would go a bit nuts trying to figure out what's going on.

@delcowizzid - Thanks for the lead. I'll look it up and see what I can learn

Thanks everyone. I was hoping their could be a relatively easy way to reconfigure a V8 bin to deal with half the input/output data while retaining all the functionality provided by the V8 bin. I'd image it would be a great option for retrofitting like the '808 has been up till now.

Chuff wrote:@Antus - Thanks antus. I wasn't aware that AFM was on the E38 & not the LS PCMs. That kinda makes my 1st post null & void. I get what you're saying about only installing half the injectors & coils but I'd imagine the PCM would go a bit nuts trying to figure out what's going on.

I dont think it would. There are 8 coils, and I dont think it'll be aware 4 of them are not there. There are 8 injectors, and it may throw a DTC there, but if that is the case you can probably mask that error. It'll be watching the narrowband in the exhaust, but if the mixtures are still good, I think it'll be happy.

The crank trigger might be a pain, but one you fit the right trigger wheel to it I think that'd be ok. The cam trigger might be a bit harder. But I think from when Holden202T was looking at running an ecotec v6 on one, the pattern was 50% high and 50% low, so there might be an existing system you could fit. Ive never looked at how cam triggers are implemented though, I dont have a v8 myself.

It would take a quite a bit of tuning, as it'd be set up for the amount of air and advance a v8 is expecting, and thats probably the biggest reason people dont do it. There are a lot of tables in those PCMs, and its a lot easier to start off with a pretty close platform and not need to change most the calibration. Moving to a 4cyl would be more work after you got the hardware working.

Thanks antus.

The post by delcowizzid got me Googling and apparently it is as simple as that. Wire it up, plug it in, turn off some DLC codes so it doesn't trip into limp home mode and that bit's done.

I was unaware of the cam timing trigger you mentioned so I once again asked Google and I see what you mean. That's quite doable on the engine I would use if I were to ever go down this path.

Then, as you rightly point out, there'd be a lot more work required tuning the PCM for the reasons you mention. If a base calibration was available to suit a 4 cylinder in a similar way that there is a base 4 cylinder calibration for the '808 I imagine it would be a much easier task requiring mainly fine tuning to make it suit the specific requirements of the engine.

Pity. Would have been a good capable setup.

Chuff,

I am exploring this same option, using a P01/P59 and v8 OS on a 4-cylinder application. While we are still in the planning stages of the project, I may have a workable theory. I intentd to run 4 LS coils, along with 4 suitable injectors, simply modifying the coil and injector firing order.

The Theory: Since you can physically assign any driver ciruit to any of its associated outputs(injector or coil outputs), let's take the 5.3 v8 firing order, and rearrange it. Instead of 18726543 firing order/events, in your tuning suite just change the order to 13421342(or whatever your firing order is), disable DTC's and fault flags for cylinders "5-8", and wire the injectors/coils accordingly. It does require an appropriate 24x/1x setup which we have addressed on the engine but beyond the scope of this post.

Now, this is only theory at the moment, but I intend to implment this in the next few months. Unless there is reason it wouldn't work or shouldn't be done.

I welcome comments and criticism, provided it's constructive.

Ed

i'd love to see you try it, but I have my doubts. the OS has hard coded degree anges from the cam. Im not sure exactly what theyre used for but skipping half the cylinders at one end of the cycle sounds like it could cause problems. let us know how you go. if you find weird things happen and its no go try stock firing order with every second coil and injector disconnected.

I think the other guy took out every second cylinder in the firing order I can't remember

I mean it will run but how accurate the timing will be is anyone's guess