Forum » General Tuning Discussion » Hot Restart - Haltech Pnp

Hot Restart - Haltech Pnp

General Tuning Discussion

Discuss all things tuning in this section. News, products, problems and results. 

= Resolved threads

Page 1

Hey guys, so in my 32GTR ive noticed after a hot restart the engine will run crap and sometimes stall...

As far as im aware this is due to the Intake air temp sensor being mounted in the intake manifold and being heat soaked after sitting for abit... Decided to do something about it today and connected the laptop and warmed up the wideband and fired it up.

IAT was 64 degree's and AFR was very lean 18-19:1 until the o2 control kicked in and added 15% more fuel...

Ive attached the log

Now this is a little tricky as AFAIK being a VE model the ideal gas law is calculated in the background and haltech doesnt allow you any way to see the calculations that are happening that I know of??? But from what Andre has said before that for every 10degree's of air temp you need to remove 2.5% of fuel to allow for less dense air, so im guessing Haltech is doing this in the background and seeing the IAT at 63 degrees and removing 10% of fuel (assuming they are using 20'c as their baseline) altho as you can see in the log the O2 correction added 15% correction and still wasnt quite at target? so maybe their baseline is zero 'c???

So looking at the haltech there didnt seem to be any obvious way to combat this? there is after start enrichment but this is coupled with coolant temp... There is a Air temp correction map but this is active all the time so didnt think that was a good way.

I found with the Haltech PnP you can activate a generic fuel compensation table and choose conditions for when this is active.

I choose the trigger conditions as anytime the IAT is over 50'c and the engine running time is under 3 minutes then my correction table comes into effect. Which is a 2D table with IAT as the axis and adds 2.5% enrichment for every 10 degree's... from a few initial tests its much much better altho not quite reaching normal idle AFR's but nothing you can detect without watching the laptop. maybe haltech does use 0'c as their base value?

Soooo basically just checking if this is actually a good way to tackle the problem? is 3 minutes long enough/too long or is there a better way to do it?

Ive attached a screenshot of the software settings also..

I do plan to get a better IAT sensor and mount it in the intake piping after the intercooler but will use a software fix for now.

Attached Files

The problem you're experiencing is pretty typical, however IAT is probably only part of the issue - You'll also find that fuel temperature will have heat soaked significantly too and this results in the fuel density being reduced and the engine runs lean.

There's no single 'right' way of dealing with hot restart. The most common is a generic fuel trim that's added for a period of time when the engine is deemed to be hot restarted. What you've described sounds like a pretty sensible approach to this although in my own experience it's incredibly hard to get a perfect result in all conditions.

The Haltech VE model accounts for the IAT in the main fuel model. There's nothing secretive or special about the way this is done and it's really just application of the ideal gas law. I find that many VE fuel models seem to be a little aggressive in the way IAT variation is dealt with and in the Haltech you can still make your own adjustments to the IAT fuel trim in the IAT compensation map (if this is all set to zero then IAT comp is handled solely by the fuel model).