IAT mod for timing retard w/HP Tuner Pros/Cons

[VvtBEAST]

With HP Tuners I have been seeing that you can make a simple retard box for less then $30 for nitrous applications to assist in retarding the timing when spraying (N20)

My question is wouldn't this have an effect on the fuel maps/trims since you can no longer aquire an actual real time IAT? Or is there a different way it tally fuel trims when faking the IAT? I know I can buy a $300 timing box but I see alot of people do this with great success. Anyone on here that has this done? and does it cause issues when not being able to log real time actual IAT temps? And not having a IAT fuel trim availible to Make changes as real the IAT'S change?

[IneedAZ]

I made my own box. When i arm the nitrous it tells my ECM that the IAT is 10 degrees and i populated the IAT chart to remove timing for that temp. Seems to be working fine. You may have to play with the fuel jet since the car thinks the air is colder then it really is.

[rrrocketman]

Originally Posted by IneedAZ

I made my own box. When i arm the nitrous it tells my ECM that the IAT is 10 degrees and i populated the IAT chart to remove timing for that temp. Seems to be working fine. You may have to play with the fuel jet since the car thinks the air is colder then it really is.

This is the correct strategy. HPTuners exposes a table that correlates IAT both to spark correction and to fuel enrichment factor. Modify both tables to skew the fuel and spark according to your nitrous shot but only do it for a column of the table that will never be accessed under normal driving conditions. I use the coldest 2 columns (-40 I think).

Then, the only physical change you need to make is to determine the IAT sensor voltage that happens to be on the wire (use a multimeter) when HPTuners reports -40. This can be done by cutting the wire and putting a potentiometer in series. Once you figure out what resistance produces that temperature reading, you just need to make a simple parallel circuit (parallel with the IAT resistor that's already there) consisting of a fixed resistor matching your pot value and put the 2 circuits on a relay. The relay can be triggered by your nitrous switch. That way the bottle will open simultaneously with the relay switching from your car's IAT resistor to your fixed "fake" resistor and the correct table entries will be polled from the ECU, giving you fuel enrichment and spark retard for your dry shot.

[THUMOS]

[THUMOS]

@rrocketman, I've been reading your blog. Good stuff, sir! Let me ask your opinion. If I have a stout fuel system (dual pumps w/flex fuel stuff and 1400lb injectors for e85 in my 2013 2SS), is a dry system as robust an option as wet if I apply the IAT hack with the resistor and HPTuners? I mean, if fuel system isn't a limiting factor, is there any reason not to choose dry? I love the idea of controlling timing and fuel through my tune and changing to my "nitrous tune" with a toggle switch!

[THUMOS]

Can you think of any way to incorporate a progressive nitrous controller into this scenario? It seems the tables we can tune with HP Tuners don't really give us that much flexibility in the -40 column to adjust fuel (looks like spark is adjustable for RPM) for a variable shot that ramps over time/rpm.

[rrrocketman]

Sorry. Seems I haven't been checking here. I assume you're the one who posted on my hubpage though.

[THUMOS]

Yessir. And I do appreciate the help!

[ADM PERFORMANCE]

At ADM Performance we use Hp Tuners and EFI Live for tuning cars daily. You will find that EFI Live has a really cool feature that actually gives you a new timing table as well as a fuel table and injector table just for Nitrous,turbo etc .

You save you stock tune,than apply this free OS UPGRADE and now you get the above features.

You run 12+ positive to pin 5 on e38 via your nitrous relay or other 12v souce when the nitrous is triggered and now you have a completely new nitrous tune.

It works fantastic for multi stage boost cars,nitrous cars,cars that run race gas on weekends and pump during the week,even e85 cars.

Its a pdf here - http://www.efilive.com/documentation-tutorials

Scroll down - Custom OS Upgrade E-38 E-67.

Print it off and read it.It works great also.

[THUMOS]

Nice, but I'm a poor guy tied to HP Tuners. That said, I'm digging around in HP Tuners on my E38, and I'm looking at PE (Power Enrichment). It seems like this function could be made to tie in beautifully with nitrous. It commands richer air-fuel ratios by RPM at WOT, and there is also a spark correction table by RPM for it as well. If I'm not missing something, wouldn't this be a perfect match for an RPM porgressed dry system? I'm a newby to both timing and nitrous, so if this is a blind alley, please let me know.

@rrocketman...yes, I'm double posting again on your hubpage as well.

[scv_guy]

There is a better way to do it, i did the relocation of the IAT and used the iat timing adder. It works the only problem is if your meth fails in the middle of a pass your still going to be running advanced timing because it takes to long for the iat to react.
Use a DSX Flex timing box, it allows you to set up a separate map. Look it up
https://youtu.be/jvL0TkG59Gs

[IneedAZ]

Originally Posted by THUMOS

Can you think of any way to incorporate a progressive nitrous controller into this scenario? It seems the tables we can tune with HP Tuners don't really give us that much flexibility in the -40 column to adjust fuel (looks like spark is adjustable for RPM) for a variable shot that ramps over time/rpm.

I use a NOS Mini Controller along with my timing retard box using IAT. For the street I have my controller set to be 14% off the line and brings in the remaining over 1.5 seconds. When i run DR tires i change it up to 100% off the line if the car is hooking good and no wheel hop.

[mlee]

Originally Posted by ADM PERFORMANCE

At ADM Performance we use Hp Tuners and EFI Live for tuning cars daily. You will find that EFI Live has a really cool feature that actually gives you a new timing table as well as a fuel table and injector table just for Nitrous,turbo etc .

You save you stock tune,than apply this free OS UPGRADE and now you get the above features.

You run 12+ positive to pin 5 on e38 via your nitrous relay or other 12v souce when the nitrous is triggered and now you have a completely new nitrous tune.

It works fantastic for multi stage boost cars,nitrous cars,cars that run race gas on weekends and pump during the week,even e85 cars.

Its a pdf here - http://www.efilive.com/documentation-tutorials

Scroll down - Custom OS Upgrade E-38 E-67.

Print it off and read it.It works great also.

This is pretty cool

[PR325xi]

Originally Posted by IneedAZ

I made my own box. When i arm the nitrous it tells my ECM that the IAT is 10 degrees and i populated the IAT chart to remove timing for that temp. Seems to be working fine. You may have to play with the fuel jet since the car thinks the air is colder then it really is.

What resistor did you use?