How should I wire my LS?

A build thread is forthcoming, but the background is that I have an L92 from a 2007 Yukon Denali that I'm putting in my S197 Mustang.  Car will primarily be an autox / hillclimb / TT car, but will stay tagged just cause.  Phase 1 of the motor build will be as little as possible while I get the other variables nailed down.  Clean it up, re-gasket it, and replace anything that is too ugly upon teardown.  Long term it will get built with a compression bump and some additional RPM headroom.  Still figuring out if I want to go with a VVT cam or eliminate that and go with something LS3 based, and still deciding if that happens now or later.  I think I prefer to keep the VVT though seeing how flat some of the graphs I'm seeing are.  

Initial plan was to just go aftermarket standalone.  I've got some experience with that and I like the elegance of it.  That said, reading some threads here, reading through LT1swap.com, etc has me contemplating weeding the original harness and running it off of the original (E38) ECM.  I do like how robust OEM components are compared to most of the aftermarket, so that's a consideration.  If I can save a few bucks, all the better, but that's less of a concern.  That all said, I'm drowning a bit in OEM acronyms, figuring out which variation of ECM I have (2007 being a bit of a weird year it seems), what that is and isn't capable of, etc. 

I'm also not sure what exists as far as tuning options if I keep the original ECM.  For standalone, I know how things work.  And for mostly original cars I know there is OBD port flashing and such.  I think maybe HP tuners has the ability to do legit tuning on the original hardware, but it's not entirely clear.  And is that a thing I buy, or that I need a shop that speaks that language, etc?  Tell it to me like I'm 5.  ;)

Any other wisdom / input is appreciated.

I would go (have gone) with the OEM part. All the hard work of edge cases has been done for you - cold start, AC idle compensation, intake air temp compensation, etc. With an aftermarket ECU, that's all on you or your tuner. It's well documented (once you figure out what you have, and I'll bet there's a part number actually printed on the PCM) and HP Tuners is pretty easy to use.

First off, the e38 sucks. I'd go aftermarket every day and twice on Sunday if that was my options.

Im not completely sold on vvt in a ls. I like simplicity and would just eliminate it. I did in my old suburban and never really noticed any difference when really running hard. It was soft on take off but that may have been the cam I selected.

Tuning options are HPTuners or efilive for a stocker.

Personally, as long as it runs, I'd swap a cam, lifters, and run it as is. Disturb as little as possible. Don't look at it too much to overthink the "I should"s. Clean it up, paint it you want, change parts, and install.

 In person, seeing more happy drivers with OEM stuff than aftermarket solutions.

The aftermarket controllers seem to all run wideband O2 sensors. That is a good thing. A buddy of mine that does his own tuning added a wide-band sensor and piped the signal into the EGR input of the OEM ECM. Very useful trace to have on board.

I would say that weeding out a harness is worth doing once just to make you very familiar with the whole wiring system. After that, I would probably look at just buying the China harness cause whynot for the price?

May or may not be relevant, but a problem I ran into when building the Hot Rod was that the O2 sensors needed to be grounded to the chassis. The wiring that I had wanted to ground the O2 sensors to an isolated ground in the ECM. Drove me crazy trying to figure out why no O2 signal. 

Keith Tanner said:

I would go (have gone) with the OEM part. 

Ranger50 said:

First off, the e38 sucks. I'd go aftermarket every day and twice on Sunday if that was my options.

God, I love the internet.  It's good to be back. ;)

I know jack about the specific ECU you have, but I will say I followed the lt1swap directions (with a few slight changes, mostly a more robust fuse/relay configuration), and it was not difficult at all.  I am not good at wiring, either.

A shop should have no issue with tuning any ECU that HPTuners can handle.  If you are going to be making progressive upgrades, you may want to spend the money on an HPTuners interface to do at least some of the work yourself.  If you intend to do all the engine work as one big batch, it'll probably be cheaper to pay a tuner.

I highly recommend the Terminator X if you want to modify the engine.

Also - don't let the magic out of the LS by opening it up.    

DILYSI Dave said:

Keith Tanner said:

I would go (have gone) with the OEM part. 

 

Ranger50 said:

First off, the e38 sucks. I'd go aftermarket every day and twice on Sunday if that was my options.

God, I love the internet.  It's good to be back. ;)

I've had to tune two e38's in my vehicles and it has left me head scratching more than once. The older boxes are way easier to tune imo. 
Only way I'd do an e38 is for 6l trans control which is stupid easy to tune. But given at least holley has a control box now.... 

I don't have a need for trans control, so there is that.

DILYSI Dave said:

Keith Tanner said:

I would go (have gone) with the OEM part. 

 

Ranger50 said:

First off, the e38 sucks. I'd go aftermarket every day and twice on Sunday if that was my options.

God, I love the internet.  It's good to be back. ;)

Nothing like building a consensus :)

I'm not sure if I have experience with an E38 or not. I might - I think that's what might have been in my car the first time it got an LS. It was an inconsistent bastard, but that was in large part due to a "tuner" who reflashed his own OS on it and had no freakin' clue what he was doing. I fired him, got it reflashed to a stock OS, took over tuning and got it reasonably happy. It was probably 50 hp down from where it could be, but it was enough at the time and I wasn't chasing power.

The second LS got installed along with the GMPP crate PCM, which I think is an E67. It's been rock solid, once we set up the MAF targets we basically just let it do its thing. It's the most powerful Miata we've ever built at FM other than the one with a megadollar Lingenfelter engine that also used the same PCM.

I also have the 1998 "red/blue" PCM in my MG which seems to work fine.

Meanwhile, I spent years supporting aftermarket engine management. Thus my personal preference :)

I semi-struggled with an e38 and HP Tuners for several years.  Running stock is super-easy (especially when you realize that truck engine tunes are capped at like 98 or 99 miles per hour on the front straight of Thunderhill).  You will still need to be able to tune super-basic stuff (wheel diameter, VATs, MAF, etc.), though, and for the cost, HP Tuners has gone a bit far for what you get.

Changing a cam or injectors or adding a turbo is where things tend to get rough.  As for the harness, I tried doing one myself (first one I had a guy on eBay do, which worked great) based on the LT1 guy's recs, and (on my second swap) I screwed it up and went with a cheap harness from eBay (which worked great, and I wish I'd done that first).  Life with a Holley Terminator is much easier, especially with weird cams and injectors and intakes . . .

rustomatic said:

I semi-struggled with an e38 and HP Tuners for several years.  Running stock is super-easy (especially when you realize that truck engine tunes are capped at like 98 or 99 miles per hour on the front straight of Thunderhill).  You will still need to be able to tune super-basic stuff (wheel diameter, VATs, MAF, etc.), though, and for the cost, HP Tuners has gone a bit far for what you get.

Changing a cam or injectors or adding a turbo is where things tend to get rough.  As for the harness, I tried doing one myself (first one I had a guy on eBay do, which worked great) based on the LT1 guy's recs, and (on my second swap) I screwed it up and went with a cheap harness from eBay (which worked great, and I wish I'd done that first).  Life with a Holley Terminator is much easier, especially with weird cams and injectors and intakes . . .

I'm more and more leaning to running it stock-ish.  Spend that time and money getting it in the car, mated to the Jerico, dry sump figured out, blah blah blah.  Then build it later.  

You mention a speed cap - I assume there's a way to disable / lie to the ECU?  No need for it to know my speed and more stuff to figure out if it does.  Same with wheel diameter.  I assume there's a way to disable?  

I'll probably give weeding my original harness a go, for the education / familiarity as much as anything.  But that could always change once I'm up to my eyeballs in spaghetti.  Biggest hesitation on the ebay harness is I've ready horror stories about them put together wrong.  I HATE the idea of trying to diagnose that.  At least my current harness was in a running vehicle a week ago.

Harnesses are easy if you just take one wire at a time and write things down. They're not fast, but they're easy. 

A speed limiter is the sort of thing you can usually turn off in HP Tuners with a checkbox. If you're putting in a manual, it can use the speed signal for the reverse lockout. Also, it lets you pull speed from the CAN bus for gauges. 

Stock ECU + stockish engine seems like the smart play to start. Factor ECUs have a number of advantages:
- Better diagnostic detection and reporting (codes should tell you which sensor/coil/etc failed)
- Limp home capability if something does fail
- Canned calibration files likely exist for a given cam/package (ex L92 + mild cam + headers - however, if you use the MAF and have different piping you'll need to do at least some tuning).
- What to change/disable for a cross-make swap and going auto to manual should be relatively easy to determine
 

That said, in the long run with a hotter engine build, going aftermarket would be my choice for a few reasons:
- I hate tuning things where you can't see everything that's going on. There's so many layers to the OEM software that it's often difficult or impossible to know what is causing a certain behavior. This doesn't matter much if the engine is relatively stock but any aftermarket tuning system for factory software is only giving you a limited subset of information and calibration parameters to adjust.
- Flexibility for integration with other CAN devices (data logging/dash/gauges/etc)
- Advanced features like launch control, traction control, no lift shift, etc 
- MS3 or MS3Pro seems like a good option. I like the open source nature vs having to be dependent on a specific company for information/support (this can cut the other way if you need dependable support). 

I went the cheap route and am running a MS2 w/ MS2extra code on a Gen 1 SBC w/ LS coils. Rolled my own wiring harness. Have tuned E67s on a couple different engines (s/c LE5 and t/c LS3). E38 is pretty similar. I like EFILive over HP Tuners due to some of the additional features they had back 10+ years ago, but I think the smart short term plan is to not get either and instead use that $$$ towards an aftermarket controller in the future. 

On the VVT, that can limit your cam choices so the pistons and valve play nice together. Usually there is a VVT limiter needed, like with the L99 vs LS3 Camaros.  The 5.3 LH6 I have doesn't have VVT, just the DOD which is being eliminated.

HPTuners is good, but they have recently limited what you can change or turn off, unless you take their online tuners course. If you want to go standalone, I know you know some guys that can help. 

WRT CAN and aftermarket gauges - the full protocol for GM is published and available. No need to reverse engineering like with, say, Mazda. 

In reply to NOHOME :

idk man, the chinese harness I bought had constant battery power on the tach lead and I had to fix and reroute several other circuits. I give the china harness 4/10 because yeah it was cheap and eventually got the job done but it caused a lot of frustration. I would have been time ahead weeding down a stock harness but went off the shelf to hopefully not have had to spend that time. staring down the barrel of another swap wiring job, I'm using an OE harness again like on my datsun challenge car. I have another chinese swap harness that will probably get used also, but for the time being I stocked up on factory truck harnesses. 

So, one potential issue with the stock harness - I am getting misfire codes with my swap right now, and don't know if it is just the old coils, or if it is the very crusty 22 year old salt belt wiring harness.  Will have to do some research, and get some new coils, but if that doesn't do the trick, I have some other changes I want to make that may lead me towards going aftermarket, and having a brand new harness could be a bonus.

In reply to eastsideTim :

Ok, this might sound weird, but make sure you have all of the injectors connected to the correct wires.

The way some harnesses are laid out, it is very easy to get the even bank injectors' connectors wrong.  Get thee a wiring diagram and verify that the wire colors for 4, 6, and 8 are what they are supposed to be.

It will cause misfires if they are mixed up.  It's easy to do.  People I work with have done it.  People I am have done it.

Unless you have a dead miss, it 99.9% isn't a harness issue.

In reply to Pete. (l33t FS) :

Using a factory harness right now, and labeled it well when I pulled it, so it should be right.  Plus, I am not really noticing the misfires, so am going to guess it may be the coils.  Plugs are fairly new.

If it is reporting misfires, but you are not feeling any misfires, you may need to do a crankshaft variation relearn.  Fairly common to need to do if you have changed any one of the crankshaft, crank sensor, or computer. Or reflashed the computer.

I know most scan tools with bidirectional controls can do it, not sure if any of the tuning suites can.  VCM Scanner may be able to do it if you have HPT.

It's "fun"!  You get the engine warmed up, apply the brake and the parking brake, hit "go", then go full throttle and let off right as the engine hits the rev limiter.  (It must hit the limiter, but not bounce against it)

I must point out, because this is what I do, you may have labeled the connectors but this does not mean that previous hands didn't get them mixed up.  Again, very easy to do with some harnesses...

DILYSI Dave said :

I'll probably give weeding my original harness a go, for the education / familiarity as much as anything.  But that could always change once I'm up to my eyeballs in spaghetti.

dude, I pared down the 1994 C4 harness and mated it with the 1965 Corvair harness and I have a 100% turnkey car. If I can do it, *you* can do it.

It hath been decided.  Phase 1 is gonna be running it as stock as possible, including a weeded OE harness and E38.  I've found enough support for HP Tuners and the E38 that I don't feel alone in the wilderness.  

Step 1 is gonna be to put that throw that disgusting rats nest into the ultrasonic cleaner to make it less nasty to work on.  

DILYSI Dave said:

It hath been decided.  Phase 1 is gonna be running it as stock as possible, including a weeded OE harness and E38.  I've found enough support for HP Tuners and the E38 that I don't feel alone in the wilderness.  

Step 1 is gonna be to put that throw that disgusting rats nest into the ultrasonic cleaner to make it less nasty to work on.  

I found the entire discussion interesting. Thinking getting up and running stockish is beneficial as well.  Once my race car is rehired I will be in LS swap land too.

The kid and I spent the evening removing loom and tape and 80% of the nastiness.  Depinning tools arrive tomorrow. Let's do this.